Change search
ReferencesLink to record
Permanent link

Direct link
Imaging the high energy cosmic ray sky
KTH, School of Engineering Sciences (SCI), Physics.
2006 (English)Licentiate thesis, monograph (Other academic)
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. Air shower data can be visualised in real-time using a Java-applet client.

The design and performance of the first three detector stations located at the AlbaNova University Centre are presented. The detectors have been running since the beginning of October 2005 and the data from this period is analysed to assess the stability and performance of the detector array. A total of 503 showers with a primary particle energy above 1016 eV, hitting all three detector stations simultaneously, have been detected during this period. The read out and data-base system used to collect the data are described together with a quicklook tool for ensuring the integrity of the data.

A preliminary study of the acceptance of the detector array as a function of weather conditions, to be used in future studies of cosmic ray anisotropy, is presented. The acceptance of the single detector stations is found to decrease with increasing atmospheric pressure and to stay constant over a large range of temperatures. The acceptance of the entire array of detector stations is found to have a stronger continuous dependence on temperature than single stations. The dependence of the array acceptance on pressure is inconclusive.

The ability of the array to reconstruct the primary cosmic ray direction is assessed with simulations. A critical feature for the reconstruction is the time resolution of the system. The performance of the GPS system is therefore tested, and the time resolution is found to be better than 15 ns for all tested GPS units. The angular resolution of the array for this time resolution is found to be (7.0\pm0.3)^{\circ}. As the time resolution is expected to decrease for a larger array of detectors, the dependency of the time resolution on the angular resolution is derived.

The measured distribution of the primary cosmic ray arrival direction is derived and compared to the expected distribution to check the performance of the system. The agreement between the distributions is good and the GPS timing system can therefore be concluded to work well. The simulations also show that the energy threshold of the array is slightly above 1016 eV.

A preliminary study of the cosmic ray anisotropy is presented. The hypothesis of an isotropic flux of cosmic rays was tested using a two point correlation function. The probability that the observed flux is a random sampling from an isotropic flux was checked with a Kolmogorov test and it was found to be 82%. The hypothesis of an isotropic flux is therefore supported.

Place, publisher, year, edition, pages
Stockholm: KTH , 2006. , viii, 106 p.
Trita-FYS, ISSN 0280-316X ; 2006:39
National Category
Subatomic Physics
URN: urn:nbn:se:kth:diva-3998ISBN: 91-7178-380-6OAI: diva2:10312
2006-06-02, A5:1003, AlbaNova University Centre, Roslagstullsbacken 21, Stockholm, 10:15
QC 20101116Available from: 2006-05-29 Created: 2006-05-29 Last updated: 2010-11-16Bibliographically approved

Open Access in DiVA

fulltext(4125 kB)241 downloads
File information
File name FULLTEXT01.pdfFile size 4125 kBChecksum MD5
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Hofverberg, Petter
By organisation
Subatomic Physics

Search outside of DiVA

GoogleGoogle Scholar
Total: 241 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

Total: 364 hits
ReferencesLink to record
Permanent link

Direct link