Change search
Refine search result
1 - 46 of 46
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Badel, Xavier
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Linnros, Jan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Kleimann, P.
    LENAC, Univ.́ Claude Bernard Lyon-I, Villeurbanne.
    Norlin, B.
    Department of Information Technology, Mid-Sweden University, Sundsvall.
    Koskiahde, E.
    Metorex International Oy, Espoo.
    Valpas, K.
    Metorex International Oy, Espoo.
    Nenonen, S.
    Metorex International Oy, Espoo.
    Petersson, Sture
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Fröjdh, C.
    Department of Information Technology, Mid-Sweden University, Sundsvall.
    Metallized and oxidized silicon macropore arrays filled with a scintillator for CCD-based X-ray imaging detectors2004In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 51, no 3, p. 1001-1005Article in journal (Refereed)
    Abstract [en]

    Silicon charge-coupled devices (CCDs) covered with a scintillating film are now available on the market for use in digital medical imaging. However, these devices could still be improved in terms of sensitivity and especially spatial resolution by coating the CCD with an array of scintillating waveguides. In this paper, such waveguides were fabricated by first etching pores in silicon, then performing metallization or oxidation of the pore walls and finally filling the pores with CsI(TI). The resulting structures were observed using scanning electron microscopy and tested under X-ray exposure. Theoretical efficiencies of macropore arrays filled with CsI(TI) were also calculated, indicating that the optimal pore depth for metallized macropore arrays is about 80 mum while it is around 350 mum for oxidized ones. This result, together with the roughness of the metal coating, explains why lower SNR values were measured with the metallized macropores. Indeed, the macropore arrays had depths in the range of 210-390 mum, which is favorable to oxidized structures.

  • 2.
    Badel, Xavier
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Norlin, B.
    Department of Information Technology and Media, Mid-Sweden University, Sundsvall.
    Kleimann, P.
    LENAC, Université Claude Bernard Lyon-I, Villeurbanne.
    Williams, L.
    Applied Scintillation Technology, Harlow.
    Moody, S. J.
    Applied Scintillation Technology, Harlow.
    Tyrell, G. C.
    Applied Scintillation Technology, Harlow.
    Fröjdh, C.
    Department of Information Technology and Media, Mid-Sweden University, Sundsvall.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Performance of scintillating waveguides for CCD-based X-ray detectors2006In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 53, no 1, p. 3-8Article in journal (Refereed)
    Abstract [en]

    Scintillating films are usually used to improve the sensitivity of CCD-based X-ray imaging detectors. For an optimal spatial resolution and detection efficiency, a tradeoff has to be made on the film thickness. However, these scintillating layers can also be structured to provide a pixellated screen. In this paper, the study of CsI(TI)-filled pore arrays is reported. The pores are first etched in silicon, then oxidized and finally filled with CsI(TI) to form scintillating waveguides. The dependence of the detector sensitivity on pore depth, varied from 40 to 400 mu m here, follows rather well theoretical predictions. Most of the detectors produced in this work have a detective quantum efficiency of the incoming X-ray photons of about 25%. However, one detector shows that higher efficiency can be achieved approaching almost the theoretical limit set by Poisson statistics of the incoming X-rays. Thus, we conclude that it is possible to fabricate scintillating waveguides with almost ideal performance. Imaging capabilities of the detectors are demonstrated.

  • 3. Bazan, A.
    et al.
    Bellachia, F.
    Blondel, A.
    Colas, J.
    Citterio, M.
    Lafaye, Remi
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    Wingerter, I
    al., et
    The ATLAS liquid argon calorimeter read-out system2006In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 53, no 3, p. 735-740Article in journal (Refereed)
    Abstract [en]

    The Liquid Argon calorimeters play a central role in the ATLAS experiment. The environment at the LHC collider imposes challenging tasks to their read-out system. To achieve measurements of particles and trigger signals at high precision, the detector signals are processed at various stages before reaching the Data Acquisition system (DAQ). Signals from the calorimeter cells are received by front-end boards, which digitize and sample the incoming pulse. Read-out Driver (ROD) boards further process the data at a trigger rate of up to 75 kHz. An optimal filtering procedure is applied to optimize the signal-to-noise ratio. The ROD boards calculate precise energy, time and quality of the detector pulse, which are then sent to the DAQ. In addition, the RODs perform a monitoring of the data. The architecture of the ATLAS Liquid Argon detector read-out is discussed, in particular the design and functionality of the ROD board. Performance results obtained with ROD prototypes as well as experience from complete test setups with final production boards are reported.

  • 4. Bongi, M
    et al.
    Adriani, O
    Ambriola, A
    Bakaldin, A
    Barbarino, G C
    Basili, A
    Bazilevskaja, G
    Bellotti, R
    Bencardino, R
    Boezio, M
    Bogomolov, E A
    Bonechi, L
    Bongiorno, L
    Bonvicini, V
    Boscherini, M
    Cafagna, F S
    Campana, D
    Carlson, Per
    KTH, Superseded Departments, Physics.
    Casolino, M
    Castellini, G
    Circella, M
    De Marzo, C N
    De Pascale, M P
    Furano, G
    Galper, A M
    Giglietto, N
    Grigorjeva, A
    Koldashov, S V
    Korotkov, M G
    Krut'kov, S Y
    Lund, Jens
    KTH, Superseded Departments, Physics.
    Lundquist, J
    Menicucci, A
    Menn, W
    Mikhailov, V V
    Minori, M
    Mirizzi, N
    Mitchell, J W
    Mocchiutti, E
    Morselli, A
    Mukhametshin, R
    Orsi, Silvio
    KTH, Superseded Departments, Physics.
    Osteria, G
    Papini, P
    Pearce, Mark
    KTH, Superseded Departments, Physics.
    Picozza, P
    Ricci, M
    Ricciarini, S B
    Romita, M
    Rossi, G
    Russo, S
    Schiavon, P
    Simon, M
    Sparvoli, R
    Spillantini, P
    Spinelli, P
    Stochaj, S J
    Stozhkov, Y
    Straulino, S
    Streitmatter, R E
    Taccetti, F
    Vacchi, A
    Vannuccini, E
    Vasilyev, G I
    Voronov, S A
    Wischnewski, R
    Yurkin, Y
    Zampa, G
    Zampa, N
    PAMELA: A satellite experiment for antiparticles measurement in cosmic rays2004In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 51, no 3, p. 854-859Article in journal (Refereed)
    Abstract [en]

    PAMELA is a satellite-borne experiment that will study the antiproton and positron fluxes in cosmic rays in a wide range of energy (from 80 MeV up to 190 GeV for antiprotons and from 50 MeV up to 270 GeV for positrons) and with high statistics, and that will measure the antihelium/helium ratio with a sensitivity of the order of 10(-8). The detector will fly on-board a polar orbiting Resurs DK1 satellite, which will be launched into space by a Soyuz rocket in 2004 from Baikonur cosmodrome in Kazakhstan, for a 3-year-long mission. Particle identification and energy measurements are performed in the PAMELA apparatus using the following subdetectors: a magnetic spectrometer made up of a permanent magnet equipped with double-sided microstrip silicon detectors, an electromagnetic imaging calorimeter composed of layers of tungsten absorber and silicon detectors planes, a transition radiation detector made of straw tubes interleaved with carbon fiber radiators, a plastic scintillator time-of-flight and trigger system, a set of anticounter plastic scintillator detectors, and a neutron detector. The features of the detectors and the main results obtained in beam test sessions are presented.

  • 5.
    Bornefalk, Hans
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging.
    Persson, Mats
    KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging.
    Xu, Cheng
    KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging.
    Karlsson, Staffan
    KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging.
    Svensson, Christer
    Danielsson, Mats
    KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging.
    Effect of Temperature Variation on the Energy Response of a Photon Counting Silicon CT Detector2013In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 60, no 2, p. 1442-1449Article in journal (Refereed)
    Abstract [en]

    The effect of temperature variation on pulse height determination accuracy is determined for a photon counting multibin silicon detector developed for spectral CT. Theoretical predictions of the temperature coefficient of the gain and offset are similar to values derived from synchrotron radiation measurements in a temperature controlled environment. By means of statistical modeling, we conclude that temperature changes affect all channels equally and with separate effects on gain and threshold offset. The combined effect of a 1 degrees C temperature increase is to decrease the detected energy by 0.1 keV for events depositing 30 keV. For the electronic noise, no statistically significant temperature effect was discernible in the data set, although theory predicts a weak dependence. The method is applicable to all x-ray detectors operating in pulse mode.

  • 6.
    Chilo, José
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Lindblad, Thomas
    KTH, School of Engineering Sciences (SCI), Physics.
    Hardware implementation of 1D wavelet transform on an FPGA for infrasound signal classification2008In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 55, no 1, p. 9-13Article in journal (Refereed)
    Abstract [en]

    Infrasound is a low frequency acoustic phenomenon that typically ranges from 0.01 to 20 Hz. The data collected from infrasound microphones are presented online by the infrasound monitoring system operating in Northern Europe, i.e., the Swedish-Finnish Infrasound Network (SFIN). Processing the continuous flow of data to extract optimal feature information is important for real-time signal classification. Performing wavelet decomposition on the real-time signals is an alternative. The purpose of this paper is to present the design and FPGA implementation of discrete wavelet transforms (DWT) for real-time infrasound data processing; our approach uses only two FIR filters, a high-pass and a low-pass filter. A compact implementation was realized with pipelining techniques and multiple use of generalized building blocks. The design was described in VHDL and the FPGA implementation and simulation were performed on the QUARTUS II platform.

  • 7.
    Ersmark, Tore
    et al.
    KTH, Superseded Departments, Physics.
    Carlson, Per
    KTH, Superseded Departments, Physics.
    Daly, E.
    Fuglesang, C.
    Gudowska, I.
    Lund-Jensen, Bengt
    KTH, Superseded Departments, Physics.
    Nartallo, R.
    Nieminen, P.
    Pearce, Mark
    KTH, Superseded Departments, Physics.
    Santin, G.
    Sobolevsky, N.
    Status of the DESIRE project: Geant4 physics validation studies and first results from columbus/ISS radiation simulations2004In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 51, no 4, p. 1378-1384Article in journal (Refereed)
    Abstract [en]

    The Dose Estimation by Simulation of the ISS Radiation Environment (DESIRE) project aims to accurately calculate radiation fluxes and doses to astronauts inside the European Columbus module of the International Space Station using Geant4. Since Geant4 has not been previously used for this type of application it needs to be validated. This will be followed by a detailed evaluation of the incident radiation fields on ISS and culminate with the geometry modeling and full-scale flux and dose simulations for Columbus. Geant4 validation studies and comparisons to other tools are presented. These concern the angle and energy distributions of particles leaving irradiated targets and of energy depositions in the targets. Comparisons are made between simulations using different Geant4 physics models, experimental data, and other particle transport programs. Geant4 using the Binary Cascade model for inelastic nucleon reactions performs very well in these comparisons, but some issues with other models remain to be resolved if they are to be used for space radiation shielding applications. Results of Geant4 simulations of the transport of some relevant radiation field components through the hull of a simplified model of Columbus are also presented.

  • 8. Ersmark, Tore
    et al.
    Carlson, Per
    Daly, Eamonn
    Fuglesang, Christer
    Gudowska, Irena
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Nieminen, Petteri
    Pearce, Mark
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Santin, Giovanni
    Geant4 Monte Carlo simulations of the galactic cosmic ray radiation environment on-board the international space station/columbus2007In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 54, no 5, p. 1854-1862Article in journal (Refereed)
    Abstract [en]

    A characterization of the Galactic Cosmic Ray (GCR) induced radiation environment on-board Columbus and the Inter-national Space Station (ISS) has been carried out using the Geant4 Monte Carlo particle transport toolkit and detailed geometry models of Columbus and ISS. Dose and dose equivalent rates, as well as penetrating particle spectra are presented. Simulation results indicate that the major part of the dose rates due to GCR protons are associated with secondary particles produced in the hull of ISS. Neutrons contribute about 15% of the GCR proton dose equivalent rate and mesons about 10%. More than 40% of the simulated GCR proton dose and dose equivalent rates are due to protons in the energy range above 10 GeV. Protons in the energy range above 50 GeV contribute only 5% to the dose rates. The total simulated dose and dose equivalent rates at solar maximum are 63 mu Gy/d and 123 mu Sv/d, respectively. The dose equivalent rate underestimates measurements made during the 2001 solar maximum. The discrepancy can be attributed to deficiencies in hadronic ion-nuclei interaction models for heavy ions and to the lack of such models above 10 GeV/N in Geant4.

  • 9. Ersmark, Tore
    et al.
    Carlson, Per
    Daly, Earnorm
    Fuglesang, Christer
    Gudowska, Irena
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Nierninen, Petteri
    Pearce, Mark
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Santin, Giovanni
    Geant4 Monte Carlo Simulations of the belt proton radiation environment on board the international space Station/Columbus2007In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 54, no 4, p. 1444-1453Article in journal (Refereed)
    Abstract [en]

    A detailed characterization of the trapped-proton-induced radiation environment on board Columbus and the International Space Station (ISS) has been carried out using the Geant4 Monte Carlo particle transport toolkit. Dose and dose equivalent rates, as well as penetrating particle spectra are presented. These results are based on detailed Geant4 geometry models of Columbus and ISS, comprising a total of about 1000 geometry volumes. Simulated trapped-proton dose rates are found to be strongly dependent on ISS altitude. Dose rates for different locations inside the Columbus cabin are presented, as well as for different models of the incident trapped-proton flux. Dose rates resulting from incident anisotropic trapped protons are found to be lower than, or equal to, those of omnidirectional models. The anisotropy induced by the asymmetric shielding distribution of Columbus/ISS is also studied. The simulated trapped-proton dose (equivalent) rates, averaged over different locations inside Columbus, are 120 mu Gy/d (154 mu Sv/d) and 79 mu Gy/d (102 mu Sv/d) for solar minimum and maximum conditions according to AP8 incident proton spectra and an ISS orbit of 380 km. The solar maximum dose rates are found to be of the same order as measurements in other modules in the present ISS.

  • 10. Fernandez, A. F.
    et al.
    Brichard, B.
    Berghmans, F.
    El Rabii, H.
    Fokine, Michael
    Popov, M.
    Chemical composition fiber gratings in a high mixed gamma neutron radiation field2006In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 53, no 3, p. 1607-1613Article in journal (Refereed)
    Abstract [en]

    Fiber Bragg gratings are all-fiber wavelength-selective refractive index structures manufactured through UV exposure of optical fibers. Their applications range from WDM all-fiber filters, dispersion compensators and fiber laser resonators for optical telecommunication applications to different types of point or distributed optical fiber sensors for a large variety of applications. The nuclear industry is considering the use of photonic technology for data communication in the next generation of nuclear power plants. In addition, fiber Bragg grating sensors are being evaluated by the nuclear industry for structural integrity and temperature monitoring. This work aims to study, in harsh radiation environments, a new type of FBG referred to as chemical composition grating. These gratings differ from other types of FBG in that their refractive index structure is attributed to a change in the chemical composition. Chemical composition gratings have shown to be extremely temperature stable surviving temperatures in excess of 1000 degrees C. We have experimentally studied the effect of very harsh gammaneutron radiation on the properties of chemical composition gratings fabricated in a Ge-F doped silica optical fiber.

  • 11. Gierlik, M.
    et al.
    Batsch, T.
    Moszynski, M.
    Szczesniak, T.
    Wolski, D.
    Klamra, Wlodzimierz
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Perot, B.
    Perret, G.
    Comparative study of large NaI(Tl) and BGO scintillators for the EURopean Illicit TRAfficking Countermeasures Kit project2006In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 53, no 3, p. 1737-1743Article in journal (Refereed)
    Abstract [en]

    The Tagged Neutron Inspection System, which is the principle of the EURITRACK project, requires efficient and inexpensive gamma-ray detectors. For this purpose, properties of 3 x 3 and 5 x 5 cylindrical BGO and NaI(TI) scintillators and of a 5 x 5 x 10 rectangular NaI(TI) scintillator were determined. 14 Light yield, energy and time resolution of the investigated crystals at the energy of few MeVs of gamma-rays are emphasized. Additionally, the crystals efficiencies calculated with Monte Carlo simulations are compared to peak-to-total ratios obtained experimentally for various combinations of PMTs and the scintillators.

  • 12. Gustavsson, Mikael
    et al.
    Ul Amin, Farooq
    Björklid, Anders
    Ehliar, Andreas
    Xu, Cheng
    KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging.
    Svensson, Christer
    A High-Rate Energy-Resolving Photon-Counting ASIC for Spectral Computed Tomography2012In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 59, no 1, p. 30-39Article in journal (Refereed)
    Abstract [en]

    We describe a high-rate energy-resolving photon-counting ASIC aimed for spectral computed tomography. The chip has 160 channels and 8 energy bins per channel. It demonstrates a noise level of ENC= electrons at 5 pF input load at a power consumption of <5mW/channel. Maximum count rate is 17 Mcps at a peak time of 40 ns, made possible through a new filter reset scheme, and maximum read-out frame rate is 37 kframe/s.

  • 13. Hegyesi, G.
    et al.
    Imrek, J.
    Kalinka, G.
    Molnar, J.
    Novak, D.
    Vegh, J.
    Balkay, L.
    Emri, M.
    Kis, S. A.
    Molnar, G.
    Tron, L.
    Valastyan, I.
    Bagamery, I.
    Bukki, T.
    Rozsa, S.
    Szabo, Z.
    Kerek, Andras
    KTH, School of Technology and Health (STH), Medical Engineering.
    Ethernet based distributed data acquisition system for a small animal PET2006In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 53, no 4, p. 2112-2117Article in journal (Refereed)
    Abstract [en]

    We report on the design of a small animal PET scanner being developed at our institutes. The existing setup is the first version of the miniPET machine consisting of four detector modules. Each detector module consists of an 8 x 8 LSO scintillator crystal block, a position sensitive photomultiplier, a digitizer including a digital signal processing board and an Ethernet interface board. There is no hardware coincidence detection implemented in the system and coincidence is determined based on a time stamp attached to every event by a digital CFD algorithm. The algorithm is implemented in the digital signal processing board and generates a time stamp with a coincidence resolution of less than 2 us. The data acquisition system is based on Ethernet network and is highly scalable in size and performance.

  • 14.
    Hegysei, G.
    et al.
    Institute of Nuclear Research of the Hungarian Academy of Sciences.
    Imrek, J.
    Institute of Nuclear Research of the Hungarian Academy of Sciences.
    Valastyán, Iván
    KTH, School of Technology and Health (STH), Medical Engineering.
    Kerek, Andras
    KTH, School of Technology and Health (STH), Medical Engineering.
    Ethernet based distributed data acquistion system for small animal PET2006In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 53, no 4Article in journal (Refereed)
    Abstract [en]

    We report on the design of a small animal PET scanner being developed at our institutes. The existing setup is the first version of the miniPET machine consisting of four detector modules. Each detector module consists of an 8times8 LSO scintillator crystal block, a position sensitive photomultiplier, a digitizer and digital signal processing board and an Ethernet interface board. There is no hardware coincidence detection implemented in the system, coincidence is determined based on a time stamp attached to every event by a digital CFD algorithm. The algorithm is implemented in the digital signal processing board and it generates a time stamp with a coincidence resolution of 2 to 3 ns. The data acquisition System is based on Ethernet network and is highly scalable in size and performance

  • 15.
    Hofverberg, Petter
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Johansson, H.
    KTH, School of Engineering Sciences (SCI), Physics.
    Pearce, Mark
    KTH, School of Engineering Sciences (SCI), Physics.
    Rydström, Stefan
    KTH, School of Engineering Sciences (SCI), Physics.
    Wikström, Christian
    KTH, School of Engineering Sciences (SCI), Physics.
    The data acquisition system of the Stockholm Educational Air Shower Array2005In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 52, no 6, p. 2801-2809Article in journal (Refereed)
    Abstract [en]

    The Stockholm Educational Air Shower Array (SEASA) project is deploying an array of plastic scintillator detector stations on school roofs in the Stockholm area. Signals from GPS satellites are used to time synchronise signals from the widely separated detector stations, allowing cosmic ray air showers to be identified and studied. A low-cost and highly scalable data acquisition system has been produced using embedded Linux processors which communicate station data to a central server running a MySQL database. Air shower data can be visualised in real-time using a Java-applet client. It is also possible to query the database and manage detector stations from the client. In this paper, the design and performance of the system are described.

  • 16.
    Hormozan, Yashar
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Yun, Sang-Ho
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Svenonius, Olof
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Towards High-Resolution X-Ray Imaging Using a Structured Scintillator2012In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 59, no 1, p. 19-23Article in journal (Refereed)
    Abstract [en]

    Structured scintillators, by light-guiding secondary emitted visible photons to a pixel in a CCD or CMOS image sensor, improve the lateral resolution of X-ray imaging detectors. In this work we have fabricated pore arrays in a silicon wafer and subsequently filled them with CsI(Tl) by a melting process. The goal was to down-scale the pore geometry for increased resolution. The results show that although pore depth must be reduced to comply with achievable aspect ratio of the Inductively Coupled Plasma (ICP) etching, melting into the pores is possible. The time and temperature has, however, to be optimized to prevent thallium loss during the melting. By correlating light yield measurements with the X-ray absorption in samples of various geometries, we find that the efficiency is slightly reduced for pore diameters approaching one micron. Nevertheless, the increased absorption in deep pores will lead to a significantly improved quantum efficiency compared to thin films currently used to achieve the same lateral resolution.

  • 17. Iacobaeus, C.
    et al.
    Danielsson, Mats
    KTH, Superseded Departments, Physics.
    Fonte, P.
    Francke, T.
    Ostling, J.
    Peskov, V.
    Sporadic electron jets from cathodes - The main breakdown-triggering mechanism in gaseous detectors2002In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 49, no 4, p. 1622-1628Article in journal (Refereed)
    Abstract [en]

    We have demonstrated experimentally that the main breakdown-triggering mechanism in most gaseous detectors, including micropattern gaseous detectors, is sporadic electron jets from the cathode surfaces. Depending on the counting rate and applied voltages, each jet contains randomly from a few primary electrons up to 10(5), emitted in a time interval ranging between 0.1 mus to milliseconds. After the emission, these primary electrons experience a full gas multiplication in the detector and create spurious pulses. The rate of these jets increases with applied voltage and very sharply at voltages close to the breakdown limit. In our measurements, we found that these jets are responsible for the breakdown-triggering at any counting rate between 10(-2) Hz/mm(2) and 10(8) Hz/mm(2). We demonstrated on a few detectors that an optimized cathode-geometry, a high electrode surface quality, and a proper choice of the gas mixture considerably improve the performance characteristics and provide the highest possible gains. Results from this work were helpful in the construction of high-performance gaseous detectors for medical imaging applications.

  • 18. Iacobaeus, C.
    et al.
    Francke, I.
    Danielsson, Mats
    KTH, Superseded Departments, Physics.
    Östling, J.
    Peskov, Vladimir
    KTH, Superseded Departments, Physics.
    Study of capillary-based gaseous detectors2004In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 51, no 3, p. 952-959Article in journal (Refereed)
    Abstract [en]

    We have studied gain versus voltage characteristics and position resolutions of multistep capillary plates (two or three capillary plates operating in a cascade), as well as capillary plates operating in a mode when the main amplification occurs between plates or between the capillary plate and the readout plate (parallel plate amplification mode). Results of these studies demonstrated that in the parallel-plate amplification mode one can reach both high gains (>10(5)) and good position resolutions (similar to100 mum) even with a single step arrangement. It offers a compact amplification structure, which can be used in many applications. For example, in preliminary tests we succeeded to combine it with a photocathode and use it as a position sensitive gaseous photomultiplier. CsI coated capillary plates could also be used as a high position resolution and high rate X-ray converter.

  • 19. Iacobaeus, C.
    et al.
    Francke, T.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ostling, J.
    Pavlopoulos, P.
    Peskov, V.
    Tokanai, F.
    A high position resolution X-ray detector: An Edge on illuminated capillary plate combined with a gas amplification structure2006In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 53, no 2, p. 554-561Article in journal (Refereed)
    Abstract [en]

    We have developed and successfully tested a prototype of a new high position resolution hybrid X-ray detector. It contains a thin-wall lead glass capillary plate converter of X-rays combined with a microgap parallel-plate avalanche chamber operating in various gas mixtures at 1 atm. The operation of these converters was studied in a wide range of X-ray energies (from 6 to 60 keV) at incident angles varying from 0-90 degrees. The detection efficiency, depending on the geometry, photon's energy, incident angle and the mode of operation was between 5-30% in single step mode and up to 50% in a multi-layered combination. Depending on the capillary's geometry, the position resolution achieved was between 50-250 mu m in digital form and was practically independent of the photon's energy or gas mixture. The usual lead glass capillary plates operated without noticeable charging up effects at counting rates of 50 Hz/mm(2) and hydrogen treated capillaries-up to 10(5) Hz/mm(2). The developed detector has several important potential advantages over the exciting X-ray detectors and may open new possibilities for medical imaging, for example in mammography, portal imaging, radiography (including security devices), as well as many other applications.

  • 20. Issa, F.
    et al.
    Vervisch, V.
    Ottaviani, L.
    Szalkai, D.
    Vermeeren, L.
    Lyoussi, A.
    Kuznetsov, A.
    Lazar, M.
    Klix, A.
    Palais, O.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Radiation silicon carbide detectors based on ion implantation of boron2014In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 61, no 4, p. 2105-2111, article id 6849512Article in journal (Refereed)
    Abstract [en]

    Radiation detectors based on radiation-hardened semiconductor such as silicon carbide (SiC), have received considerable attention in many applications such as in outer space, high energy physics experiments, gas and oil prospection, and nuclear reactors. In the frame work of the European project I-SMART (Innovative Sensor for Material Ageing and Radiation Testing), we demonstrated for the first time the reliability of thermal neutron detectors realized by standard ion implantation of boron atoms to form a neutron converter layer (NCL). Two types of detectors were realized; the first was implanted by aluminum to create the p+ - layer, and then implanted by boron ( 10 B) to realize the NCL. The second type was based on p+ - layer, and was implanted by 10B into the aluminum metallic contact in order to avoid implantation-related defect within the sensitive area. Both kinds of detectors reveal to respond to thermal neutrons and gamma rays, showing consistent counting rates as a function of bias voltages, radiation intensity and type of shielding.

  • 21. Kapusta, M.
    et al.
    Moszynski, M.
    Balcerzyk, M.
    Braziewicz, J.
    Wolski, D.
    Pawelke, J.
    Klamra, Wlodzimierz
    KTH, Superseded Departments, Physics.
    Comparison of the scintillation properties of LSO: Ce manufactured by different laboratories and of LGSO : Ce2000In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 47, no 4, p. 1341-1345Article in journal (Refereed)
    Abstract [en]

    We measured photoelectron yield, light output, decay times of the light pulses, cerium concentration, energy resolution and time resolution of LSO:Ce manufactured by different laboratories and LGSO:Ce. The LSO samples show excellent scintillation properties: high light output, close to 30,000 ph/MeV and good energy resolution of 7.3% FWHM for Cs-137 gamma-source full energy peak. Time resolution measured in geometry fulfilling the PET scanners requirements is equal to 450 ps. We also present results fi om the measurements with LGSO:Ce by Hitachi Chemical Co., which is of similar chemical composition to LSO. LGSO, at present stage of development, shows about 20% lower light output than LSO and energy resolution of 12.4% FWHM for 662 keV gamma-rays. LSO crystals used in our studies posses similar in scintillation properties, although we suppose that the details of the productions method are different due to the differences in Ce concentration. LGSO is a new and very promising scintillator due to lower background radiation in comparison to LSO, but it features worse energy resolution and smaller number of photoelectrons.

  • 22. Kleimann, P.
    et al.
    Linnros, Jan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Frojdh, C.
    Petersson, C. Sture
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    An x-ray imaging pixel detector based on a scintillating guides screen2000In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 47, no 4, p. 1483-1486Article in journal (Refereed)
    Abstract [en]

    We have developed and preliminary tested a new digital X-ray imaging sensor based on a scintillating guide screen. The scintillating guides are used to channel the emitted visible light to the pixel detector. This enables us to avoid the well-known tradeoff between detection efficiency and spatial resolution which is encountered when a non-patterned scintillating layer is used on top of a CCD. A prototype has been fabricated using microtechnologies. The scintillator is CsI:T1 and the low-index cladding material used to channel the light is silicon dioxide. The performance of this prototype has been compared to that of a thick CsI single crystal. The results concerning the spatial resolution are quite promising and demonstrate a proof-of-principle. However, the performance in terms of signal to noise ratio and sensitivity have to be improved. These problems are currently addressed.

  • 23. Leon, R.
    et al.
    Marcinkevicius, Saulius
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Siegert, J.
    Cechavicius, B.
    Magness, B.
    Taylor, W.
    Lobo, C.
    Effects of proton irradiation on luminescence emission and carrier dynamics of self-assembled III-V quantum dots2002In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 49, no 6, p. 2844-2851Article in journal (Refereed)
    Abstract [en]

    The effects of proton irradiation (1.5 MeV) on photoluminescence intensities and carrier dynamics were compared between III-V quantum dots and similar quantum well structures. A significant enhancement in radiation tolerance is seen with three-dimensional (3-D) quantum confinement.. Measurements were carried out in different quantum dot (QD) structures, varying in material (InGaAs/GaAs and InAlAS/AlGaAS), QD surface density (4 x 10(8) to 3 x 10(10) cm(-2)), and substrate orientation [(100) and (311) B]. Similar trends were observed for all QD samples. A slight increase in PL emission after low to intermediate proton doses, are also observed in InGaAs/GaAs (100) QD structures. The latter is explained in terms of more efficient carrier transfer from the wetting layer via radiation-induced defects.

  • 24.
    Liu, Xuejin
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Bornefalk, Hans
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Chen, Han
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Danielsson, Mats
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Karlsson, Staffan
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Persson, Mats
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Xu, Cheng
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Huber, Ben
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    A Silicon-Strip Detector for Photon-Counting Spectral CT: Energy Resolution From 40 keV to 120 keV2014In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 61, no 3, p. 1099-1105Article in journal (Refereed)
    Abstract [en]

    We are developing a segmented silicon-strip detector for spectral computed tomography. The detector operates in photon-counting mode and allows pulse-height discrimination with 8 adjustable energy bins. In this work, we determine the energy resolution of a detector module using monoenergetic x-rays from 40 keV to 120 keV, provided at the European Synchrotron Radiation Facility, Grenoble. For each incident x-ray energy, pulse height spectra at different input photon fluxes are obtained. We investigate changes of the energy resolution due to charge sharing between pixels and pulse pileup. The different incident energies are used to channel-wise calibrate the pulse-height response in terms of signal gain and offset and to probe the homogeneity of the detector module. The detector shows a linear pulse-height response in the energy range from 40 keV to 120 keV. The gain variation among the channels is below 4%, whereas the variation of the offsets is on the order of 1 keV. We find an absolute energy resolution (sigma(E)) that degrades from 1.5 keV to 1.9 keV with increasing x-ray energy from 40 keV to 100 keV. With increasing input count rate, sigma(E) degrades by approximately 4 . 10(-3) keV Mcps(-1) mm(2), which is, within error bars, the same for the different energies. The effect of charge sharing on the width of the response peak is found to be negligible.

  • 25.
    Liu, Xuejin
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Chen, Han
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Bornefalk, Hans
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Danielsson, Mats
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Karlsson, Staffan
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Persson, Mats
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Xu, Cheng
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Huber, Ben
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Energy Calibration of a Silicon-Strip Detector for Photon-Counting Spectral CT by Direct Usage of the X-ray Tube Spectrum2015In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 62, no 1, p. 68-75Article in journal (Refereed)
    Abstract [en]

    The variation among energy thresholds in a multibin detector for photon-counting spectral CT can lead to ring artefacts in the reconstructed images. Calibration of the energy thresholds can be used to achieve homogeneous threshold settings or to develop compensation methods to reduce the artefacts. We have developed an energy-calibrationmethod for the different comparator thresholds employed in a photon-counting silicon-strip detector. In our case, this corresponds to specifying the linear relation between the threshold positions in units of mV and the actual deposited photon energies in units of keV. This relation is determined by gain and offset values that differ for different detector channels due to variations in the manufacturing process. Typically, the calibration is accomplished by correlating the peak positions of obtained pulse-height spectra to known photon energies, e. g. with the aid of mono-energetic x rays from synchrotron radiation, radioactive isotopes or fluorescence materials. Instead of mono-energetic x rays, the calibrationmethod presented in this papermakes use of a broad x-ray spectrum provided by commercial x-ray tubes. Gain and offset as the calibration parameters are obtained by a regression analysis that adjusts a simulated spectrum of deposited energies to ameasured pulse-height spectrum. Besides the basic photon interactions such as Rayleigh scattering, Compton scattering and photo-electric absorption, the simulation takes into account the effect of pulse pileup, charge sharing and the electronic noise of the detector channels. We verify the method for different detector channels with the aid of a table-top setup, where we find the uncertainty of the keV-value of a calibrated threshold to be between 0.1 and 0.2 keV.

  • 26.
    Lund-Jensen, Bengt
    KTH, Superseded Departments, Physics.
    The status of the construction and the performance of the ATLAS liquid argon electromagnetic calorimeters2004In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 51, no 5, p. 2181-2186Article in journal (Refereed)
    Abstract [en]

    The construction of the ATLAS liquid argon electromagnetic calorimeters is about to be completed. The barrel calorimeter and the first end-cap are inserted in their cryostats. The quality control performed during the production has resulted in only a very small fraction of malfunctioning channels (similar to0.1%) and a low constant term in the energy resolution. Several modules of the calorimeter and their corresponding presampler sectors have been tested in electron beams, and their energy resolution has been shown to be within the ATLAS requirements. The local constant term is better than 0.4% for all measured cells and the global constant term which includes the cell-to-cell response variation is less than 0.7%.

  • 27. Lundqvist, M.
    et al.
    Cederström, Björn
    KTH, Superseded Departments, Physics.
    Chmill, V.
    Danielsson, Mats
    Hasegawa, B.
    Evaluation of a photon-counting X-ray imaging system2001In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 48, no 4, p. 1530-1536Article in journal (Refereed)
    Abstract [en]

    A digital imaging system has been developed for mammography using silicon strip detectors operated in a pulse-counting mode and configured in a scanned slit geometry. More than 90% of the photons are absorbed in the sensor. The scatter rejection is very efficient and the image formation is nearly optimal since each X ray is processed individually. The result is a very dose-efficient system. In this paper, we present measurements that verify that the performance of the readout electronics is sufficient to count photons at high rates with high quantum efficiency and a charge collection efficiency that does not limit the dose efficiency. The spatial resolution of the system was measured to provide a modulation transfer function of approximately 0.5 at a spatial frequency of 10 lp/mm. Images of a mammography phantom were recorded experimentally to test overall system performance.

  • 28. Lundqvist, M.
    et al.
    Cederström, Björn
    KTH, Superseded Departments, Physics.
    Chmill, V.
    Danielsson, Mats
    KTH, Superseded Departments, Physics.
    Nygren, D.
    Computer simulations and performance measurements on a silicon strip detector for edge-on imaging2000In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 47, no 4, p. 1487-1492Article in journal (Refereed)
    Abstract [en]

    Silicon strip detectors to be used edge-on for imaging in a scanned slit geometry have been simulated. A software program was developed which can simulate the motion of free charges in the bulk detector and calculate the signals they induce on the electrodes. The purpose was to quantify the impact of charge sharing on system detective quantum efficiency(DQE). The energy spectrum that was used in this study is typical for mammography. The detectors are working in single photon counting mode and the optimal threshold level to discriminate noise from useful signals has been calculated. The loss in detective quantum efficiency due to charge sharing was found to be around 5% for a 100 mu m pitched detector. Coincidence circuits can be included in the electronics to eliminate this problem. Furthermore, it is described how the relationship between charge collection efficiency and photon interaction position in the detector can be measured.

  • 29.
    Maguire Jr., Gerald Q.
    et al.
    University of Utah, Department of Computer Science.
    Brill, Aaron Bertrand
    Brookhaven National Laboratory.
    Noz, Marilyn E.
    New York University.
    Bennett, G. W.
    Brookhaven National Laboratory.
    Schimpf, James H.
    New York University.
    Horii, Steven C.
    New York University.
    Yonekura, Y.
    Brookhaven National Laboratory.
    Zeleznik, Michael P.
    Bizais, Yves
    Brookhaven National Laboratory.
    Baxter, Brent S.
    University of Utah.
    Zubal, I. George
    Yale University.
    Hitchner, Lewis E.
    University of Utah.
    Rowe, R. Wanda
    Brookhaven National Laboratory.
    Interface Requirements in Nuclear Medicine-Devices and Systems1982In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 29, no 4, p. 1280-1290Article in journal (Refereed)
    Abstract [en]

    Interface designs for three nuclear medicine imaging systems, and computer networking strategies proposed for medical imaging departments are presented. Configurations for two positron emission tomography devices (PET III and ECAT) and a general purpose tomography instrument (the UNICON) are analyzed in terms of specific performance parameters. Interface designs for these machines are contrasted in terms of utilization of standard versus custom modules, cost, and ease of modification, upgrade, and support. The requirements of general purpose systems for medical image analysis, display, and archiving, are considered, and a realizable state of the art system is specified, including a suggested timetable.

  • 30. Moszynski, A.
    et al.
    Balcerzyk, A.
    Czarnacki, W.
    Kapusta, A.
    Klamra, Wlodzimierz
    KTH, Superseded Departments, Physics.
    Syntfeld, A.
    Szawlowski, A.
    Intrinsic energy resolution and light yield nonproportionality of BGO2004In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 51, no 3, p. 1074-1079Article in journal (Refereed)
    Abstract [en]

    The intrinsic energy resolution and nonproportionality of the light yield as a function of gamma ray energies, in the energy range of 14 keV to 1.33 MeV, were studied for small BGO (Bi4Ge3O12) crystals at room and liquid nitrogen (LN2) temperatures. The study showed that the intrinsic resolution of BGO and the light yield nonproportionality, as a function of energy do not depend on the crystal temperature. High light outputs of 14000 +/- 300 electron-hole pairs and energy resolution of 6.5% +/- 0.2% for 662 keV gamma rays were measured with the 9 mm diameter, 4 mm thick crystals, coupled to large area avalanche photodiodes and cooled down to LN2 temperature. Special attention was paid to analyzing the energy resolution of the escape peaks, which were well separated from the full-energy peaks due to the good energy resolution of BGO at LN2 temperatures and the energy of bismuth KX-rays. The intrinsic energy resolution of the BGO crystal for escape peaks does not show deviations from analysis of total energy absorption photopeaks. This is in spite of the fact that the contributions of X-rays and Auger electron cascade in creation of escape peaks are much smaller than in full-energy peaks. In the small volume crystal, mainly electrons produced in the photoelectric absorption create the escape peaks.

  • 31. Moszynski, M.
    et al.
    Balcerzyk, M.
    Czarnacki, W.
    Kapusta, M.
    Klamra, Wlodzimierz
    KTH, Superseded Departments, Physics.
    Schotanus, P.
    Syntfeld, A.
    Szawlowski, M.
    Study of pure NaI at room and liquid nitrogen temperatures2003In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 50, no 4, p. 767-773Article in journal (Refereed)
    Abstract [en]

    Three pure NaI crystals grown in different batches by Scionix (The Netherlands) were studied at room and liquid nitrogen temperatures. The room temperature studies performed with photomultiplier readout covered measurements of emission spectra, photoelectrons yield and energy resolution. Moreover, the scintillation light poises were measured by single photon method. Two crystals showed the photoelectron yield of about 1000 phe/MeV measured at room temperature with an XP2020Q photomultiplier. The energy resolution of the 662 keV photopeak was measured to, be about 16% and was limited mainly by a low number of photoelectrons and a large nonproportionality of the light yield. The fast light pulse had the main decay time components of 1 and 5 ns. The high initial photon intensity of the tested NaI crystals revealed a good timing. resolution of about 140 ps obtained for Co-60 gamma-rays. At. liquid nitrogen temperatures the measurements of light yield and energy resolution were performed using An Advanced Photonix, Inc. avalanche photodiode readout A high light output above 80 000 ph/MeV was measured for the best of the tested crystals. The energy resolutions of the 662 kAV photopeak of the three crystals differ a lot, varying from an excellent value of 3.8% to 6.2%. This suggests that the measured, pies energy resolutions depend on the purity of the scintillator samples reflected in the emission spectral The studies that were performed demonstrate the attractive properties of pure NaI at both room and LN2 temperature.

  • 32. Ostling, J.
    et al.
    Brahme, A.
    Danielsson, Mats
    KTH, Superseded Departments, Physics.
    Francke, T.
    Iacobaeus, C.
    Peskov, V.
    Study of hole-type gas multiplication structures for portal imaging and other high count rate applications2003In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 50, no 4, p. 809-819Article in journal (Refereed)
    Abstract [en]

    We performed studies in the operation of various hole-type gaseous multiplication structures (GEM, capillary plates, and others) at very high fluxes of X-rays (<60 keV-bremsstrahlung) and pulsed gamma radiation (<50 MeV-bremsstrahlung). In the case of X-rays, the counting rate was 10(5)-10(6) Hz/mm(2); in the case of gammas it reached levels of up to 10(9) Hz/mm(2) during the pulses. In most measurements, the entire area of the detector was exposed to these extremely high fluxes. Results obtained so far indicate that the GEM and the hydrogen-treated capillary plates could be successfully used in medical imaging applications.

  • 33. Periale, L.
    et al.
    Peskov, V.
    Iacobaeus, C.
    Francke, T.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Pavlopoulos, P.
    Picchi, P.
    Pietropaolo, F.
    Tokanai, F.
    The successful operation of hole-type gaseous detectors at cryogenic temperatures2005In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 52, no 4, p. 927-931Article in journal (Refereed)
    Abstract [en]

    We have demonstrated that hole-type gaseous detectors, gas electron multipliers and capillary plates (CPs) can operate at temperatures down to 77 K. For example, a single CP can operate at gains above 10(3) in the entire temperature interval between 77 and 300 K. The same CP combined with CsI photocathodes operates perfectly well at gains of 100-1000, depending on the gas mixture. The obtained results open new fields of applications for CPs as detectors of ultraviolet light and charged particles at cryogenic temperatures: liquid noble gas time-projection chambers, detectors for weakly interacting massive particles or liquid Xe scintillating calorimeters, and cryogenic positron-emission tomography.

  • 34. Peskov, V.
    et al.
    Baibussinov, B.
    Centro, S.
    Di Mauro, A.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Martinengo, P.
    Nappi, E.
    Oliveira, R.
    Pietropaolo, F.
    Picchi, P.
    Periale, L.
    Rodionov, I.
    Ventura, S.
    Development and first tests of GEM-Like detectors with resistive electrodes2007In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 54, no 5, p. 1784-1791Article in journal (Refereed)
    Abstract [en]

    We have developed and tested several prototypes of GEM-like detectors with electrodes coated with resistive layers or completely made of resistive materials. These detectors can operate stably at gains close to 10(5). The resistive layers limit the energy of discharges appearing at higher gains thus making the detectors very robust. We demonstrated that the cathodes of some of these detectors could be coated by CsI or SbCs layers to enhance the detection efficiency for the UV and visible photons. We also discovered that such detectors can operate stably in the cascade mode and high overall gains (similar to 10(6)) are reachable. Applications in several areas, for example in RICH or in noble liquid TPCs are therefore possible. The first results from the detection of UV photons at room and cryogenic temperatures will be given.

  • 35. Peskov, V.
    et al.
    Fonte, P.
    Danielsson, Mats
    KTH, Superseded Departments, Physics.
    Iacobaeus, C.
    Ostling, J.
    Wallmark, M.
    The study and optimization of new micropattern gaseous detectors for high-rate applications2001In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 48, no 4, p. 1070-1074Article in journal (Refereed)
    Abstract [en]

    We performed a new series of systematic studies of gain and rate characteristics of several micropattern gaseous detectors. Extending earlier studies, characteristics were measured at various pressures and gas mixtures at a wide range of primary charges, and also when the whole area of the detectors was irradiated with a high-intensity X-ray beam. Several new effects were discovered, common to all tested detectors, which define fundamental limits of operation. The results of these studies allow us to identify several concrete ways of improving the performance of micropattern detectors and to suggest that in some applications, resistive plate chambers may constitute a valid alternative. Being protected from damaging discharges by the resistive electrodes, these detectors feature high gain, high rate capability (10(5) Hz/mm(2)), good position resolution (better than 30 mum), and excellent timing (50 ps sigma).

  • 36.
    Riber Marklund, Anders
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Reactor Technology. Commisariat Energie Atom & Energies Alternat CEA, France.
    Kishore, S.
    Prakash, V.
    Rajan, K. K.
    Michel, F.
    Passive acoustic leak detection for sodium fast reactors using hidden Markov models2016In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578Article in journal (Refereed)
    Abstract [en]

    Acoustic leak detection for steam generators of sodium fast reactors have been an active research topic since the early 1970s and several methods have been tested over the years. Inspired by its success in the field of automatic speech recognition, we here apply hidden Markov models (HMM) in combination with Gaussian mixture models (GMM) to the problem. To achieve this, we propose a new feature calculation scheme, based on the temporal evolution of the power spectral density (PSD) of the signal. Using acoustic signals recorded during steam/water injection experiments done at the Indira Gandhi Centre for Atomic Research (IGCAR), the proposed method is tested. We perform parametric studies on the HMM+GMM model size and demonstrate that the proposed method a) performs well without a priori knowledge of injection noise, b) can incorporate several noise models and c) has an output distribution that simplifies false alarm rate control.

  • 37. Ryzhikov, V. D.
    et al.
    Starzhinskiy, N. G.
    Gal'chinetskii, L. P.
    Guttormsen, M.
    Kist, A. A.
    Klamra, Wlodzimierz
    KTH, Superseded Departments, Physics.
    Behavior of new ZnSe(Te,O) semiconductor scintillators under high doses of ionizing radiation2001In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 48, no 4, p. 1561-1564Article in journal (Refereed)
    Abstract [en]

    Changes in scintillation and optical properties of scintillators based on ZnSe(Te,O) crystals were studied under influence of ionizing radiations: gamma (similar to1.3 MeV, up to 500 Mrad), protons (similar to 18 MeV, fluence up to 10(16) per cm(-2)), electrons (0.54-2.26 MeV, up to 50 Mrad), and neutrons (source-thermal reactor channel, fluence up to 1016 per cm(2)). Light output of gamma-irradiated scintillator crystals ZnSe(Te,O) was shown to decrease by less than 10-12% under doses of 100 Mrad, with transparence in the visible range worse by only 10-12%. Effects of electron irradiation are similar. Under neutron irradiation of crystals, increase in their light output by 20-150% is observed, with nontrivial changes of optical characteristics in the visible and infrared (IR) spectral ranges. Proton irradiation caused the most sharp degradation of scintillation properties of ZnSe(Te,O) crystals, with selective absorption bands appearing in the ER (4-7 mum) region. Accounting for the role of recombination centers related to zinc vacancies and properties of interstitial zinc atoms, a model is considered of radiation-stimulated processes in ZnSe(Te,O) semiconductor scintillators.

  • 38.
    Suvanam, Sethu Saveda
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronics, Integrated devices and circuits.
    Kuroki, Shin-Ichiro
    Lanni, Luigia
    KTH.
    Hadayati, Raheleh
    Ohshima, Takeshi
    Makino, Takahiro
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Electronics, Integrated devices and circuits.
    Zetterling, Carl-Mikael
    KTH, School of Information and Communication Technology (ICT), Electronics, Integrated devices and circuits.
    High Gamma Ray Tolerance for 4H-SiC Bipolar Circuits2016In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578Article in journal (Refereed)
    Abstract [en]

    A high gamma radiation hardness of 4H-SiC circuits is performed. The OR NOR circuits are based on emitter coupled logic (ECL), using integrated bipolar NPN transistors. Gain degradation in individual bipolar junction transistors (BJT) is minimal up to a dose of 38 Mrad (SiO2), but for the dose of 332 Mrad (SiO2) a degradation of 52% is observed. The SiC BJTs show higher radiation hardness than existing Si-technology and high stability under temperature stress. It is proposed that the oxide charge-dominated recombination is the key base current recombination mechanism contributing to gain degradation. An improvement in the gain is seen after annealing at 400 °C for 1800 s due to the possible annealing of some of the oxide defects contributing to the oxide charge.

  • 39.
    Suvanam, Sethu Saveda
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Lanni, Luigia
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Malm, Bengt Gunnar
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Zetterling, Carl-Mikael
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Effects of 3-MeV Protons on 4H-SiC Bipolar Devices and Integrated OR-NOR Gates2014In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 61, no 4, p. 1772-1776Article in journal (Refereed)
    Abstract [en]

    Radiation effects of 3-MeV protons on 4H-SiC bipolar devices and integrated OR-NOR gates have been investigated. The chips were irradiated from a fluence of 1 x 10(8) cm(-2) until 1 x 10(13) cm(-2). Up until a fluence of 1 x 10(11) cm-2, both the bipolar devices and the logic gates were found to be stable, but for higher fluence, they begin to degrade as a function of irradiation fluence. Using TCAD simulations, degradation of the transistor current gain has been found to be more dominated by surface states than bulk defects generated by the proton irradiation. Simulations of logic circuits using SPICE show that the gain degradation is the key contribution to the unstable performance of the circuits from the fluence of 1 x 10(12) cm(-2) and above.

  • 40. Swiderski, L.
    et al.
    Moszynski, M.
    Wolski, D.
    Batsch, T.
    Iwanowska, J.
    Nassalski, A.
    Syntfeld-Kazuch, A.
    Szczesniak, T.
    Kniest, F.
    Kusner, M. R.
    Pausch, G.
    Stein, J.
    Klamra, Wlodzimierz
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Schotanus, P.
    Hurlbut, C.
    Further Study of Boron-10 Loaded Liquid Scintillators for Detection of Fast and Thermal Neutrons2010In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 57, no 1, p. 375-380Article in journal (Refereed)
    Abstract [en]

    Boron-10 loaded liquid scintillators were studied in order to improve n/gamma separation. Pulse shape discrimination (PSD) was implemented by means of a zero-crossing (ZC) method to distinguish between gamma-rays and fast/slow neutrons. Significant progress was done for BC523A2 and EJ339A2 scintillators loaded with reduced amount of B-10 (2% and 2.5%, respectively), as compared to the results obtained earlier with BC523A loaded with 4.4% of B-10. The improvement was probably caused by the reduction of B-10 content, as indicated in the reported study. A B-10 loaded scintillator EJ309B5 based on non- flammable liquid was also studied, showing the best separation of thermal neutron capture events from fast neutrons, gamma-rays and noise.

  • 41. Swiderski, L.
    et al.
    Moszynski, M.
    Wolski, D.
    Batsch, T.
    Nassalski, A.
    Syntfeld-Kazuch, A.
    Szczesniak, T.
    Kniest, F.
    Kusner, M. R.
    Pausch, G.
    Stein, J.
    Klamra, Wlodzimierz
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Boron-10 Loaded BC523A Liquid Scintillator for Neutron Detection in the Border Monitoring2008In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 55, no 6, p. 3710-3716Article in journal (Refereed)
    Abstract [en]

    A BC523A liquid scintillator loaded with boron-10 was tested as a detector for both fast and thermal neutrons. A pulse shape discrimination (PSD) method based on a zero-crossing principle was applied to distinguish between neutron and gamma radiation. High quantum efficiency Photonis XP5500B photomultiplier was used to enhance light detection from the scintillator. This allowed a good registration of the energy spectrum of neutron capture events on boron-10, corresponding to about 60 keV gamma-rays. The applied PSD method proved to be useful for n/gamma discrimination. A good resolving power of the method was achieved even without gating on neutron capture events. A comparison with a standard BC501A liquid scintillator was done to evaluate thermal neutrons detection efficiency in BC523A.

  • 42. Swiderski, Lukasz
    et al.
    Moszynski, Marek
    Nassalski, Antoni
    Syntfeld-Kazuch, Agnieszka
    Czarnacki, Wieslaw
    Klamra, Wlodzimierz
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kozlov, Valentin A.
    Scintillation properties of undoped CsI and CsI doped with CsBr2008In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 55, no 3, p. 1241-1245Article in journal (Refereed)
    Abstract [en]

    The light output, energy resolution, and nonproportionality characteristics were measured for undoped CsI and several samples of CsI with different doping by CsBr. A correlation between nonproportionality of the light yield and the intrinsic energy resolution was confirmed. Contrary to previously published results the light yield of the tested samples was found to be degraded with increasing bromine concentration. The inspection of light pulse shapes was done by the single photon coincidence method. Decay times of the scintillation pulse were measured for undoped and bromine doped crystals, showing the main scintillation in tens of nanoseconds range.

  • 43. Syntfeld-Kauch, Agnieszka
    et al.
    Moszynski, Marek
    Swiderski, Lukasz
    Klamra, Wlodzimierz
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Naasalski, Antoni
    Light pulse shape dependence on gamma-ray energy in CsI(Tl)2008In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 55, no 3, p. 1246-1250Article in journal (Refereed)
    Abstract [en]

    A detailed study of the scintillation light pulse shape in CsI(Tl) at room temperature as a function of incoming photon energy in 6 divided by 662 keV energy range is presented. Three samples of CsI(Tl) of different amount of Tl dopant (0.01, 0.06 and 0.25 mol%) were used in measurements. A delayed coincidence single photon counting method was applied to measure the decay times in the microsecond range. Three-exponential function was fitted to the time spectra to describe the light pulse shape, which resulted in three components of tau(1) = 730 +/- 30 ns (fast), tau(2) = 3.2 +/- 0.3 mu s (slow) and tau(3) = 16 +/- 2 mu s (tail). The intensity of the second component was found to be sensibly independent of photon energy, whereas the intensities of the first and third ones varied with the energy of absorbed photon in low energy region. For a given crystal the most intense fast component was measured for 6-keV X-rays from Fe-55 at the cost of decreasing intensity of the slowest one. Furthermore, the intensity of the fast component depends on Tl concentration and reaches its maximum value for the 0.06 mol% doping, close to the well-know optimal concentration of 0.1 mol%.

  • 44. Syntfeld-Kazuch, Agnieszka
    et al.
    Swiderski, Lukasz
    Czarnacki, Wieslaw
    Gierlik, Michal
    Klamra, Wlodzimierz
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Moszynski, Marek
    Schotanus, Paul
    Non-proportionality and energy resolution of CsI(T1)2007In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 54, no 5, p. 1836-1841Article in journal (Refereed)
    Abstract [en]

    Experimental studies of CsI(Tl) crystals with different amounts of Tl activator are presented. Properties such as non-proportionality, energy resolution and the number of photoelectrons per 1 MeV-gamma were inspected at two different shaping time constants, i.e., 3 and 12 mu s. A CsI(Tl) crystal was coupled to the XP5212 PMT with a photocathode blue sensitivity of 12.2 mu A/lmF. Six CsI(Tl) crystals of different sizes were tested. Among them, three samples were of known Tl concentration, which amounted roughly 0.05, 0.1 and 0.25 mol%. The data analvsis showed a much more proportional character of the crystal response, higher number of photoelectrons/MeV-gamma, and consequently, a better overall energy resolution obtained for 12 mu s time constant for all tested samples. The calculated intrinsic resolution improved for longer shaping time constants as well, indicating that, for CsI(Tl) crystals, a more proportional response implies better intrinsic energy resolution of the host crystal. In contrast, the intrinsic resolution at the low energy region (below about 30 keV) deteriorated for the longer shaping time constant. An alpha/gamma ratio was also measured for each tested CsI(Tl) crystal in order to find any indication of an explanation of the intrinsic resolution deterioration for low energy photons at the 12 mu s integration time.

  • 45.
    Xu, Cheng
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging.
    Danielsson, Mats
    KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging.
    Bornefalk, Hans
    KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging.
    Evaluation of Energy Loss and Charge Sharing in Cadmium Telluride Detectors for Photon-Counting Computed Tomography2011In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 58, no 3, p. 614-625Article in journal (Refereed)
    Abstract [en]

    We present estimates of energy loss and charge sharing for a pixelated cadmium telluride (CdTe) detector used for photon-counting spectral computed tomography (CT). In a photon-counting pixelated CdTe detector, several physical effects lead to detected events with reduced energies, including Compton scattering, fluorescence emission, charge diffusion, trapping of charge carriers and slow-hole-motion-induced incomplete charge collection. Charge sharing is the result of the lost energy being collected by adjacent pixels. We simulated the photon transport and the charge-collection process with a Monte Carlo-based simulation and evaluated these effects on the detector performance. The trapping effect and poor hole collection have been studied together using an analytical model. We also investigated the detector response under the influence of only the fluorescence effect. We conclude that the charge sharing effects should be taken into account when the pixel is smaller than 1 mm(2). A straightforward way to decrease the double counting of X-rays from events with charge sharing is to increase the electronic threshold. However, increasing the threshold comes at the cost of losing low-energy events, which is undesirable, at least in applications such as pediatric imaging.

  • 46.
    Xu, Cheng
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging.
    Persson, Mats
    KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging.
    Chen, Han
    KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging.
    Karlsson, Staffan
    KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging.
    Danielsson, Mats
    KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging.
    Svensson, Christer
    Bornefalk, Hans
    KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging.
    Evaluation of a Second-Generation Ultra-Fast Energy-Resolved ASIC for Photon-Counting Spectral CT2013In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 60, no 1, p. 437-445Article in journal (Refereed)
    Abstract [en]

    A second-generation ultra-fast energy-resolved application specific integrated circuit (ASIC) has been developed for photon-counting spectral computed tomography (CT). The energy resolution, threshold dispersion and gain of the ASIC were characterized with synchrotron radiation at Diamond Light Source. The standard deviation of threshold offsets at zero keV is 0.89 keV. An RMS energy resolution of 1.09 keV has been demonstrated for 15 keV photon energy at a count rate of 40 kcps, and it deteriorates at a rate of 0.29 keV/Mcps with the increase of output cout rate. The count rate performance of the ASIC has also been evaluated with 120 kV polychromatic x-rays produced by a tungsten anode tube and the results are presented.

1 - 46 of 46
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf