Change search
CiteExportLink to record
Permanent link

Direct 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
Accelerators for Physics Experiments: From Diagnostics and Control to Design
KTH, School of Engineering Sciences (SCI), Physics.
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis develops techniques of control-methods, optimization, and diagnostics of accelerator equipment and the produced particle beams with emphasis on the Large Hadron Collider (LHC) project at CERN. From a solid knowledge of the characteristics of the manufactured accelerator equipment gained from in-depth measurements and analysis of measured data, a link to an enhanced equipment design can be made. These techniques will be demonstrated in applications related to the LHC magnet production and to the LHC upgrade studies.

The LHC is a 27 km long superconducting accelerator, which CERN, the European high-energy particle physics research organisation, is presently being commissioned in a tunnel 80 m under ground level in the Geneva region. This machine forms the last link in an interconnected chain of several particle accelerators at CERN. The overall system performance, i.e. the quality of particle beams being accelerated in this accelerator chain is directly related to the control of the quality of the superconducting magnets used in the last link, in the LHC. Different upgrade scenarios to reach the ultimate design luminosity and beyond that, implying major machine changes are presently being studied. These scenarios all pose very challenging design requirements for magnets situated in the beam collision regions where extremely radioactive environments have to be dealt with. The LHC is expected to produce very highly energetic and intense particle beams for a number of physics experiments during the next decades, making the subjects of the thesis both timely and important.

The work described has been performed at CERN, which has become the largest high-energy physics laboratory in the world. Here, a number of particle accelerators are connected in series to permit the acceleration of particles to unprecedented high energies to explore the nature of our universe. The accelerators at CERN are assembled of a large number of parts requiring a high level of technological know-how. Control systems and optimization procedures play a natural and necessary role to fulfil the requirements. Diagnostics and control system technology have been used to increase the efficiency of accelerator operation. An extensive analysis of the measured magnetic field have been used to optimize the delicate process of controlling the assembly of superconducting accelerator magnets for the LHC. This paper also describes the control procedures developed, to permit the adjustment of the geometric shape of the 15 m long dipole to optimize the field quality and beam aperture.

From a detailed statistical analysis of the collected geometry data from the 1232 LHC main dipole magnets unresolved issues concerning the measurements were explained and corrected, providing more accurate information for the alignment of the main dipoles and quadrupoles.

The LHC will start operation in 2008, after a most careful installation of all magnets and a huge volume of other equipment in the accelerator tunnel. In particular, the very specialized welding techniques and the brazing of tubes, bellows and conductors, have posed great challenges. Tenths of thousands of welds that have to withstand temperature changes of 300 K and operation with super-fluid helium at 1.9 K have been made. The magnet systems that create the conditions for particle collisions in the two main experiments, the insertion triplets, will have to be exchanged when upgrading the performance of the machine. The upgrade of the machine’s luminosity is expected after 4 years of LHC operation at nominal luminosity. Unless the new magnets are very carefully designed and well shielded the particle debris from the increased collision rates will perturb their operation. Using a new superconductor technology, limiting the probability of magnet quenches, combined with a new layout of the insertion region can minimize the effect of the impinging debris. The necessary shielding layout to protect the magnet coils will be discussed.

The future of accelerators for particle physics is important: the development of accelerator technology to produce neutrino beams from beta decaying ions is one possibility for new physics. This subject will be treated from the aspect of energy deposition from decay products in superconducting magnet coils.

Place, publisher, year, edition, pages
Stockholm: KTH , 2008. , 101 p.
Series
Trita-FYS, ISSN 0280-316X ; 2008:14
National Category
Subatomic Physics
Identifiers
URN: urn:nbn:se:kth:diva-4739ISBN: 978-91-7178-931-0 (print)OAI: oai:DiVA.org:kth-4739DiVA: diva2:13719
Public defence
2008-05-14, Sal FB55, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100921Available from: 2008-05-09 Created: 2008-05-09 Last updated: 2010-09-21Bibliographically approved
List of papers
1. Experiments to Test Beam Behaviour Under Extreme Space Charge Conditions
Open this publication in new window or tab >>Experiments to Test Beam Behaviour Under Extreme Space Charge Conditions
Show others...
1994 (English)In: EPAC 94: 4th European Particle Accelerator Conference, 1994, 279-281 p.Conference paper, Published paper (Refereed)
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-8398 (URN)
Note
QC 20100920Available from: 2008-05-09 Created: 2008-05-09 Last updated: 2010-11-24Bibliographically approved
2. Automatic beam steering in the CERN PS complex
Open this publication in new window or tab >>Automatic beam steering in the CERN PS complex
1995 (English)In: Proceedings of the 1995 16th Particle Accelerator Conference, 1995, 2178-2180 p.Conference paper, Published paper (Refereed)
Abstract [en]

The recombination, transfer and injection of the four beams from the PS Booster to the PS Main Ring, have a high level of intricacy and are a subject of permanent concern for the operation of the PS Injector Complex. These tasks were thus selected as a test bench for the implementation of a prototype of an automatic beam steering system. The core of the system is based on a generic trajectory optimizer, robust enough to cope with imperfect observations. The algorithmic engine is connected to pick-up monitors and corrector magnets and its decision can be validated by the operator through a graphics user interface. Automatic beam steering can only be efficient if the beam optics is fully confirmed by experimental observations, a condition which forces the systematic elimination of errors both in hardware and software.

Keyword
Accelerator magnets, Algorithms, Automation, Computer hardware, Computer simulation, Computer software, Control systems, Error correction, Graphical user interfaces, Mathematical models, Optimization, Particle optics, Automatic beam steering, Beam emittances, Beam optics, Beam recombination, Beam transfer, Generic trajectory optimizer, Symbolic computing
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-8399 (URN)10.1109/PAC.1995.505490 (DOI)0-7803-2934-1 (ISBN)
Note
QC 20100921Available from: 2008-05-09 Created: 2008-05-09 Last updated: 2010-11-24Bibliographically approved
3. Production follow-up of the LHC main dipoles through magnetic measurements at room temperature
Open this publication in new window or tab >>Production follow-up of the LHC main dipoles through magnetic measurements at room temperature
Show others...
2004 (English)In: IEEE transactions on applied superconductivity (Print), ISSN 1051-8223, Vol. 14, no 2, 173-176 p.Article in journal (Refereed) Published
Abstract [en]

In this paper we review the tools used for controlling the production of the LHC main dipoles through warm magnetic measurements. For the collared coil measurements, control limits are based on the statistics relative to the pre-series production. For the cold mass, the difference between collared coil and cold mass is considered, allowing a very stringent test. In both cases, measurements are split in straight part average, variations and coil ends contributions. Two different alarm levels exist in case the measured field is out of limits. The analysis can be carried out at the manufacturer and allows detection of anomalies in the measured magnetic field. These can be either due to wrong measurements or caused by assembly defects. Techniques used to work out information on the magnet assembly from the field harmonics are outlined. We summarize the experience gathered on about 180 collared coils and 120 cold masses, pointing out the bad cases and investigating the reliability of the measurements.

Keyword
magnetic field errors, magnet production control, warm magnetic measurements
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-8400 (URN)10.1109/TASC.2004.829037 (DOI)000223147500009 ()
Note
QC 20100921.Available from: 2008-05-09 Created: 2008-05-09 Last updated: 2010-11-24Bibliographically approved
4. Control of the Dipole Cold Mass Geometry at CERN to Optimize LHC Performance
Open this publication in new window or tab >>Control of the Dipole Cold Mass Geometry at CERN to Optimize LHC Performance
2006 (English)In: IEEE transactions on applied superconductivity (Print), ISSN 1051-8223, Vol. 16, no 2, 212-215 p.Article in journal (Refereed) Published
Abstract [en]

The detailed shape of the 15 m long superconducting LHC dipole cold mass is of high importance as it determines three key parameters: the beam aperture, nominally of the order of 10 beam standard deviations; the connectivity of the beam- and technical lines between magnets; the transverse position of nonlinear correctors mounted on the dipole ends. An offset of the latter produces unwanted beam dynamics perturbations. The tolerances are in the order of mm over the length of the magnet. The natural flexibility of the dipole and its mechanical structure allow deformations during handling and transportation which exceed the tolerances. This paper presents the observed deformations of the geometry during handling and various operations at CERN, deformations which are interpreted thanks to a simple mechanical model. These observations have led to a strategy of dipole geometry control at CERN, based on adjustment of the position of its central support (the dipole is supported at three positions, horizontally and vertically) to recover individually or statistically their original shape as manufactured. The implementation of this strategy is discussed, with the goal of finding a compromise between conflicting requirements: quality of the dipole geometry, available resources for corrective actions and magnet installation strategy whereby the geometry tolerances depend on the final magnet position in the machine.

Keyword
dipole geometry, feed down, mechanic aperture
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-8401 (URN)10.1109/TASC.2006.870507 (DOI)000244804100036 ()
Note
QC 20100921. Uppdaterad från manuskript till tidskrift (20100921).Available from: 2008-05-09 Created: 2008-05-09 Last updated: 2010-11-24Bibliographically approved
5. Processing magnet geometry measurements for better control of LHC aperture
Open this publication in new window or tab >>Processing magnet geometry measurements for better control of LHC aperture
2007 (English)In: IEEE Particle Accelerator Conference, PAC07, 2007, 362-364 p.Conference paper, Published paper (Refereed)
Abstract [en]

The Large Hadron Collider superconducting axes of the magnet are measured from both ends. These two redundant measurements are combined to get a reliable measurement result. When the two measurements are put together, we observe a "saw tooth" effect due to the fact that the two measurements are, in general, not identical. This is expected from the accuracy of the two measurements. However the effect observed, in the vertical plane, is considerably larger than expected. Effects of temperature gradients in the cold bore tube during measurements have been observed and we show that this effect is the most probable explanation for the observations of the large differences in the measurements between the two sides. This work proposes an algorithmic approach to filter this effect to improve measurement results. Magnets are positioned with an accuracy of 0.1 mm, and the error in positioning coming from measurement errors due to the temperature effects can be up to 0.3 mm. Our analysis shows that by applying this correction we can assure the best positioning of the magnets in the tunnel in the vertical plane. Analysis is done for the 15 in long main dipoles, for which the effect is most visible.

Keyword
Colliding beam accelerators, Electric impedance, Magnets, Particle accelerators, Superconducting magnets, Temperature, Thermal effects, Vibration analysis, Effects of temperature, Most probable explanation, Saw-tooth, Vertical planes
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-8402 (URN)10.1109/PAC.2007.4440212 (DOI)000255096301045 ()978-1-4244-0916-7 (ISBN)
Note
QC 20100921Available from: 2008-05-09 Created: 2008-05-09 Last updated: 2010-09-21Bibliographically approved
6. Magnet acceptance and allocation at the LHC magnet evaluation board
Open this publication in new window or tab >>Magnet acceptance and allocation at the LHC magnet evaluation board
2007 (English)In: IEEE Particle Accelerator Conference, PAC07, 2007, 3739-3741 p.Conference paper, Published paper (Refereed)
Abstract [en]

The normal and superconducting magnets for the LHC ring have been carefully examined to insure that each of about 1900 assemblies is suitable for the operation in the accelerator. Hardware experts and accelerator physicists have contributed to this work that consisted in magnet acceptance, and sorting according to geometry, field quality and quench level. This paper gives a description of the magnet approval mechanism that has been running since four years, reporting in a concise summary the main results achieved.

Keyword
Computer networks, Electric impedance, Particle accelerators, Vibration analysis, Evaluation board, Field quality
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-8403 (URN)10.1109/PAC.2007.4439915 (DOI)000255096300009 ()978-1-4244-0916-7 (ISBN)
Note
QC 20100921Available from: 2008-05-09 Created: 2008-05-09 Last updated: 2010-09-21Bibliographically approved
7. A large aperture superconducting dipole for beta beams to minimize heat deposition in the coil
Open this publication in new window or tab >>A large aperture superconducting dipole for beta beams to minimize heat deposition in the coil
2007 (English)In: IEEE Particle Accelerator Conference, PAC07, 2007, 365-367 p.Conference paper, Published paper (Refereed)
Abstract [en]

The aim of beta beams in a decay ring is to produce highly energetic pure electron neutrino and anti-neutrino beams coming from b-decay of 18Ne10+ and 6He2+ ion beams. The decay products, having different magnetic rigidities than the main ion beam, are deviated inside the dipole. The aperture and the length of the magnet have to be optimized to avoid that the decay products hit the coil. The decay products are intercepted by absorber blocks inside the beam pipe between the dipoles to protect the following dipole. A first design of a 6T arc dipole using a cosine theta layout of the coil with an aperture of 80 mm fulfils the optics requirements. Heat deposition in the coil has been calculated using different absorber materials to find a solution to efficiently protect the coil. Aspects of impedance minimization for the case of having the absorbers inside the beam pipe have also been addressed.

Keyword
Computer networks, Electric impedance, Particle accelerators, Beta beams, Electron neutrino, Heat deposition, Superconducting dipoles
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-8404 (URN)10.1109/PAC.2007.4440213 (DOI)000255096301046 ()978-1-4244-0916-7 (ISBN)
Note
QC 20100921Available from: 2008-05-09 Created: 2008-05-09 Last updated: 2010-09-21Bibliographically approved
8. Simulation of decays and secondary ion losses in a betabeam decay ring
Open this publication in new window or tab >>Simulation of decays and secondary ion losses in a betabeam decay ring
2007 (English)In: IEEE Particle Accelerator Conference, PAC07, 2007, 3232-3234 p.Conference paper, Published paper (Refereed)
Abstract [en]

Radioactive ions injected into the decay ring of a Betabeam neutrino facility will constitute a continuous source of decay products distributed around the ring. Secondary ions from beta decays will differ in charge state from the primary ions and will follow widely off-momentum orbits. In the racetrack configuration of the ring, they will be mismatched in the long straights and may acquire large amplitudes, but the great majority of losses will be in the arcs. We describe here a comprehensive model of ion decay, secondary ion tracking, and loss detection, which has been implemented in the tracking and simulation code Accsim. Methods have been developed to accurately follow ion trajectories at large momentum deviations as well as to detect their impact coordinates on vacuum chamber walls and possibly inside magnetic elements. Using secondary-ion data from Accsim and post-processing with Mathematica, we have implemented a follow-on simulation in FLUKA with a 3D geometry of decay ring components and physics models for ion interactions in matter, allowing radiological studies and in particular the visualization and analysis of heat deposition in the dipole magnets which is a critical design factor for the ring. In our simulations we have also implemented absorber elements which are intended to localize the majority of losses outside of the dipoles. These studies provide estimates of ring performance (in terms of loss concentration and management), the effectiveness of absorbers, and the implications for successful superconducting dipole operation.

Keyword
Computer networks, Computer simulation, Concentration (process), Control systems, Data processing, Data visualization, Electric impedance, Electrolysis, Injection (oil wells), Particle accelerators, Secondary emission, Three dimensional, Vibration analysis, Charge states, Continuous source, Secondary ions
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-8405 (URN)10.1109/PAC.2007.4440382 (DOI)000255096301212 ()978-1-4244-0916-7 (ISBN)
Note
QC 20100921Available from: 2008-05-09 Created: 2008-05-09 Last updated: 2010-09-21Bibliographically approved
9. Parametric study of heat deposition from collision debris into the insertion superconducting magnets for the LHC luminosity upgrade
Open this publication in new window or tab >>Parametric study of heat deposition from collision debris into the insertion superconducting magnets for the LHC luminosity upgrade
Show others...
2007 (English)In: IEEE Particle Accelerator Conference, PAC07, 2007, 323-325 p.Conference paper, Published paper (Refereed)
Abstract [en]

With a new geometry in a higher luminosity environment, the power deposition in the superconducting magnets becomes a critical aspect to analyze and to integrate in the insertion design. In this paper, we quantify the power deposited in magnets insertion at variable positions from the interaction point (IP). A fine characterization of the debris due to the proton-proton collisions at 7 TeV, shows that the energetic particles in the very forward direction give rise to non intuitive dependences of the impacting energy on the magnet front face and inner surface. The power deposition does not vary significantly with the distance to the interaction point, because of counterbalancing effects of different contributions to power deposition. We have found out that peak power density in the magnet insertion does not vary significantly with or without the Target Absorber Secondaries (TAS) protection.

Keyword
Accelerator magnets, Debris, Diffractive optical elements, Electric conductivity, Electric impedance, Electromagnets, Flow interactions, Luminance, Modernization, Molecular interactions, Optical properties, Particle accelerators, Protons, Superconductivity, Tellurium compounds, Vibration analysis, Interaction point, Power deposition
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-8406 (URN)10.1109/PAC.2007.4440199 (DOI)000255096301032 ()978-1-4244-0916-7 (ISBN)
Note
QC 20100921Available from: 2008-05-09 Created: 2008-05-09 Last updated: 2010-09-21Bibliographically approved
10. Are Large-Aperture NbTi Magnets Compatible with 1e35?
Open this publication in new window or tab >>Are Large-Aperture NbTi Magnets Compatible with 1e35?
2008 (English)In: CARE-HHH-APD Workshop on Interaction Regions for the LHC Upgrade, DAFNE, and SuperB, “IR’07”: 6 - 9 Nov 2007, Frascati, Italy, 2008, 74-80 p.Conference paper, Published paper (Refereed)
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-8407 (URN)978-92-9083-319-2 (ISBN)
Note
QC 20100921Available from: 2008-05-09 Created: 2008-05-09 Last updated: 2010-09-21Bibliographically approved
11. Heat deposition and backscattering for one of the configurations of the IR for LHC upgrade
Open this publication in new window or tab >>Heat deposition and backscattering for one of the configurations of the IR for LHC upgrade
2007 (English)Report (Other academic)
Publisher
25 p.
Series
AT-MCS Internal Note, 2007-02
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-8408 (URN)
Note
QC 20100921Available from: 2008-05-09 Created: 2008-05-09 Last updated: 2010-09-21Bibliographically approved

Open Access in DiVA

fulltext(5304 kB)1457 downloads
File information
File name FULLTEXT01.pdfFile size 5304 kBChecksum MD5
0abdce51fd6bfb0c86d99d7a5f1aecac19799c86859209ca3925ab20c0ad0ce16061c397
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Wildner, Elena
By organisation
Physics
Subatomic Physics

Search outside of DiVA

GoogleGoogle Scholar
Total: 1457 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 818 hits
CiteExportLink to record
Permanent link

Direct 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