Radioactive source calibration technique for the CMS hadron calorimeter

E. Hazen, C. Lawlor, J. W. Rohlf, S. X. Wu, A. Baumbaugh, J. E. Elias, J. Freeman, D. Green, D. Lazic, S. Los, A. Ronzhin, S. Sergueev, T. Shaw, R. Vidal, J. Whitmore, T. Zimmerman, M. Adams, K. Burchesky, W. Qian, A. BadenR. Bard, H. Breden, T. Grassi, A. Skuja, W. Fisher, J. Mans, C. Tully, V. Barnes, A. Laasanen, P. De Barbaro, H. Budd

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Relative calibration of the scintillator tiles used in the hadronic calorimeter for the Compact Muon Solenoid detector at the CERN Large Hadron Collider is established and maintained using a radioactive source technique. A movable source can be positioned remotely to illuminate each scintillator tile individually, and the resulting photo-detector current is measured to provide the relative calibration. The unique measurement technique described here makes use of the normal high-speed data acquisition system required for signal digitization at the 40 MHz collider frequency. The data paths for collider measurements and source measurements are then identical, and systematic uncertainties associated with having different signal paths are avoided. In this high-speed mode, the source signal is observed as a Poisson photo-electron distribution with a mean that is smaller than the width of the electronics noise (pedestal) distribution. We report demonstration of the technique using prototype electronics for the complete readout chain and show the typical response observed with a 144 channel test beam system. The electronics noise has a root-mean-square of 1.6 least counts, and a 1 mCi source produces a shift of the mean value of 0.1 least counts. Because of the speed of the data acquisition system, this shift can be measured to a statistical precision better than a fraction of a percent on a millisecond time scale. The result is reproducible to better than 2% over a time scale of 1 month.

Original languageEnglish (US)
Pages (from-to)311-327
Number of pages17
JournalNuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Issue number3
StatePublished - Oct 1 2003

Bibliographical note

Funding Information:
We thank Erik van der Bij of CERN for his assistance with the S-LINK hardware and the grounding of the G-LINK transmitter chip. Sidik Isani of the Canada–France–Hawaii Telescope provided S-LINK to PCI driver software, and Guoan Hu of Boston University gave us his expertise on many items concerning the software. J. Rohlf acknowledges support from Fermilab which allowed a release from teaching duties.


  • Hadron sampling calorimeter
  • Radioactive source calibration


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