Electronics and triggering challenges for the CMS High Granularity Calorimeter

A Lobanov

doi:10.1088/1748-0221/13/02/c02056

Abstract

The High Granularity Calorimeter (HGCAL), presently being designed by the CMS collaboration to replace the CMS endcap calorimeters for the High Luminosity phase of LHC, will feature six million channels distributed over 52 longitudinal layers. The requirements for the front-end electronics are extremely challenging, including high dynamic range (0.2 fC–10 pC), low noise (∼2000 e− to be able to calibrate on single minimum ionising particles throughout the detector lifetime) and low power consumption (∼20 mW/channel), as well as the need to select and transmit trigger information with a high granularity. Exploiting the intrinsic precision-timing capabilities of silicon sensors also requires careful design of the front-end electronics as well as the whole system, particularly clock distribution. The harsh radiation environment and requirement to keep the whole detector as dense as possible will require novel solutions to the on-detector electronics layout. Processing the data from the HGCAL imposes equally large challenges on the off-detector electronics, both for the hardware and incorporated algorithms. We present an overview of the complete electronics architecture, as well as the performance of prototype components and algorithms.

Highlights

Collaboration to replace the CMS endcap calorimeters for the High Luminosity phase of LHC, will feature six million channels distributed over 52 longitudinal layers
We present an overview of the complete electronics architecture, as well as the performance of prototype components and algorithms
The high granularity of the High Granularity Calorimeter (HGCAL) and environment of the HL-LHC pose a big challenge for the detector design, in many aspects exceeding the demands to the electronics and trigger requirements of the current LHC detector

Summary

Chapter 2. Active elements

The high granularity of the HGCAL and environment of the HL-LHC pose a big challenge for the detector design, in many aspects exceeding the demands to the electronics and trigger requirements of the current LHC detector. In the anticipated HL-LHC running scenario with on average 200 pileup interactions the cell occupancy in some HGCAL areas may reach up to 60%, whereas the current Run-2 pileup level is four times lower This high flux of particles directly translates into large radiation doses, requiring the electronics to be radiation hard up to 2 MGy. The readout electronics needs to be sensitive to large signals of the order of 3000-5000 minimum ionizing particles (MIP), which occur in TeV particle showers, but as well to single MIP deposits in order to calibrate the individual channels. The current CMS calorimeters feature about 200 thousand channels in total, whereas the HGCAL will need to power, control and read out about 6 million channels This sets stringent requirements on the electronics power consumption. It is intended to reuse and incorporate as many common parts as possible from the current HL-LHC developments, such as the low-power gigabit transceiver (lpGBT) and versatile link data transfer system

Front-end Electronics

Findings

Trigger Primitive Generation