Upgrade fo the CMS Hadron Outer Calorimeter with SIPMs
The CMS Hadron Outer Calorimeter (HO) is undergoing an upgrade to replace the existing photodetectors (HPDs) with SIPMs. The chosen device is the Hamamatsu 3 x 3mm 50 {mu}m pitch MPPC. The system has been developed to be a 'drop-in' replacement of the HPDs. A complete control system of bias voltage generation, leakage current monitoring, temperature monitoring, and temperature control using solid state Peltier coolers has been developed and tested. 108 channels of the system have been installed into CMS and operated for more than 2 years. The complete system of about 2200 channels is in production and will be installed in the next LHC long shutdown scheduled for 2013. The CMS central calorimeter consists of a detector inside the solenoidal magnet, HB, and a component outside the magnet, the Outer Hadron Calorimeter, HO [1]. The HO is installed inside the magnet flux return yoke and provides for typically 3{lambda} of additional absorber to the calorimetric measurement. The outer calorimeter is composed of one or more layers of scintillator with wavelength shifting fiber readout into photodetectors. Figure 1 (a) shows the schematic layout of the calorimeters in CMS and shows the location of the HO scintillator layers. The front end electronics are placed inside the CMS detector, close to the scintillators. Figure 1(b) shows a photograph of the scintillators. Note the four wavelength shifting fibers per tile. The tile size creates a projective tower with the HB. Currently the photodetector used is the HPD but for performance and operational reasons it is desired to upgrade these with SIPMs. The CMS HCAL group has developed a drop-in replacement for the HPD using SIPMs. SIPMs are very suitable for this application because of several factors: The radiation levels are modest with a lifetime expected fluence of less than 5*10{sup 11} neutrons (E > 100 KeV) per cm{sup 2}. The energy flux into HO is small, the rate of larger energy depositions is low, and the required dynamic range is modest. The HO is in the return magnetic field of up to 2KG and the photodetector needs to operate in that environment. Finally, the available physical volume for the photodetectors is small.
- Research Organization:
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- AC02-07CH11359
- OSTI ID:
- 1031167
- Report Number(s):
- FERMILAB-CONF-11-464-CMS-E; TRN: US1200086
- Resource Relation:
- Conference: Presented at 2nd International Conference on Technology and Instrumentation in Particle Physics 2011: TIPP 2011, Chicago, Illinois, 9-14 Jun 2011
- Country of Publication:
- United States
- Language:
- English
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