Abstract
The High Luminosity phase of the Large Hadron Collider will deliver 10 times more integrated luminosity than the existing collider, posing significant challenges for radiation tolerance and event pileup on detectors, especially for forward calorimetry. As part of its upgrade program, the Compact Muon Solenoid collaboration is designing a high-granularity calorimeter (HGCAL) to replace the existing endcap calorimeters. It will feature unprecedented transverse and longitudinal readout and triggering segmentation for both electromagnetic and hadronic sections. The electromagnetic section and a large fraction of the hadronic section will be based on hexagonal silicon sensors of 0.5–1 cm2 cell size, with the remainder of the hadronic section being based on highly-segmented scintillators with silicon photomultiplier readout. The intrinsic high-precision timing capabilities of the silicon sensors will add an extra dimension to event reconstruction, especially in terms of pileup rejection. First hexagonal silicon modules, using the existing Skiroc2 front-end ASIC developed for CALICE, have been tested in beams at Fermilab and CERN in 2016. We present results from these tests, in terms of system stability, calibration with minimum-ionizing particles and resolution (energy, position and timing) for electrons, and the comparisons of these quantities with GEANT4-based simulation.
Highlights
The various setups described in the previous section were simulated with GEANT4 [9] in the framework of the standard CMS software (CMSSW [10])
We made a comparison between data and simulation based on the FTFP_BERT_EMM and QGSP_FTFP_BERT physics lists. The former is the one used by default in CMSSW for simulation of the complete high-granularity calorimeter (HGCAL), whilst the latter is used in CMSSW for simulation of the homogeneous CMS crystal calorimeter
The reconstructed impact positions were compared to a straight line fit extrapolation from two delay wire chambers [17] (DWC) located 147 cm and 273 cm ups0tream 5o0f the fi10rs0t HG1C5A0 L m2o0d0ule,2w50hich measure the trajectory of the incoming beam particle before it showers in Ethleeccatrloonrimeneteerrgpyro[GtoetyVp]e
Summary
Thirty silicon sensors were characterized at FNAL using a custom-built probe card featuring lighttouch “pogo pins” for electronic connection. The digital data from the Skiroc2s were carried by two flexible cables to a passive right-angle adapter PCB, through another pair of flexible cables to 6U “DDC” — Dual-Daughterboard Carrier cards These DDC hosted two “FMCIO” mezzanines, utilizing standard FMC (FPGA Mezzanine Card) connectors and incorporating Xilinx XC7A100T “Artix” FPGAs. The DDC routed the signals from two FMCIO ( two modules) to a standard HDMI connector. A flexible mechanical support system was built, utilizing a “hanging file” design (see figure 9) for easy insertion of modules (attached to cooling plates) and absorber plates, which allowed different configurations to be explored. A CAEN SY1527 mainframe equipped with a CAEN A1511B floating 0-500 V high-voltage module provided, again through a distribution board, the bias voltage for the silicon sensors through SMA cables to the “elbow” boards. Decoupling capacitors were on both the elbow board and modules
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