Speaker
Description
Summary
The timetable of operation at the Large Hadron Collider (LHC) includes a number of upgrades which will increase its center of mass energy and integrated luminosity. These changes will also result in a higher fake rate in the Compact Muon Solenoid (CMS) tracking and a lower energy resolution due to signal overlap in the calorimeters. The purpose of the LHC Phase 1 Upgrade is to mitigate these effects by replacing the pixel detector of the CMS Tracker, improving the Level 1 Trigger, and upgrading the detectors and electronics of the CMS Hadron Calorimeter (HCAL).
During the HCAL Upgrade, the current hybrid photodiodes (HPDs) in the Barrel and Endcap calorimeters will be replaced with silicon photomultipliers (SiPMs) and the PMTs in the Forward Calorimeter will be replaced with multi-channel models. The performance of the SiPM detectors significantly exceeds the performance of the HPDs, which allows for a finer depth segmentation within the upgraded detector. To accommodate these improved detection capabilities and the corresponding increase in signal channels, both the front-end and back-end electronics also need to be upgraded.
In the HCAL, the signal from the phototransducers is integrated over 25 ns periods and digitized by a charge integrator and encoder (QIE) ADC. As part of the HCAL Upgrade, the current Version 8 (QIE8) chip will be replaced by the Version 10 (QIE10). The QIE10 is specifically designed to accommodate the increase in detector sensitivity by featuring ten times the dynamic range as the QIE8, from 3 fC to 330 pC. The QIE10 also provides previously unavailable TDC information which supplies signal arrival time information to the experiment with half-nanosecond resolution. This information is crucial for background reduction, distinguishing products from different bunch crossings in situations with high pileup, and identifying anomalous noise in the phototransducers.
Before the QIE10 can be implemented in the detector, the prototype chip's functionality needs to be demonstrated through system integration tests and all packaged chips need to be verified by production testing.
System integration testing focuses on the QIE10 chip's performance within the whole signal flow, from the phototransducer through the front-end and back-end electronics. A PMT is connected to a prototype QIE10 front-end electronics board which, in turn, communicates with a prototype HCAL micro-TCA back-end board. We flash the PMT with an LED to simulate in situ conditions and examine capacitor ID consistency, charge bin widths, range and subrange overlap, charge calibration accuracy, timing measurements, and component cross-talk. These tests not only show that the QIE10 is operating correctly, but allow us to identify subtle hardware and software issues that are only revealed after the entire readout chain.
The purpose of production testing is to batch test all of the packaged QIE10 chips in order to determine which are of sufficient quality to send to the CMS detector. Every chip used in the CMS detector needs to pass a series of benchmarks, which we measure using Fermilab's robotic ASIC tester.
We present the results of these tests and argue that the QIE10 is ready for implementation in the HCAL Upgrade.
