CMS Preshower Detector Research Articles

Performance, Calibration and Alignment of the CMS Preshower Detector

The Preshower detector, part of the CMS Endcap Electromagnetic Calorimeter, is designed to have good spatial resolution to identify the position of incoming particles. The detector was installed in CMS and commissioned in 2009. LHC collisions provided data used to verify the calibration of the Preshower silicon sensors, and compare low-level observables such as energy deposits and clustering with Monte-Carlo - showing good agreement. The data also allowed an alignment measurement to be performed between the Preshower and the Tracker.

An efficient hardware design for rejecting common mode in a group of adjacent channels of silicon microstrip sensors used in high energy physics experiments

Algorithms have been studied using Monte Carlo techniques and implemented in a fast Xilinx Virtex II pro field programmable gate array (FPGA), in order to calculate and remove, after pedestal subtraction, the common mode of a group of adjacent channels. The implementation of the algorithms has been optimized both for speed and minimal FPGA resources, so as to be used in multi-channel applications. The aim of this work is to define the optimum algorithm for common mode calculation to be implemented for common mode rejection in the CMS Preshower detector.

Noise measurements on Si sensors

Abstract Developing silicon strip sensors for the CMS Preshower detector we have noticed that some strips have a noise higher than the average and not correlated to a high leakage current. In order to investigate this effect we have developed a set-up for noise measurement on wafers and diced sensors that does not require bonding. The set-up is based on the DeltaStream chip coupled to a probe card. We have tested 45 sensors and found that the strips with an above average noise have a higher relative current increase as a function of voltage, Δ I /( I Δ V ). We also observed that, on these strips, the breakdown occurs within about 60 V from the voltage at which the noise is observed. We describe our measurement method and present the results.

High-voltage performance of silicon detectors irradiated under bias

The CMS preshower detector contains 16 m 2 of silicon. The silicon sensors’ design is being finalized by taking into account their performance after five years of operation at high luminosity. Three detectors from different manufacturers were irradiated by neutrons and photons under bias and at low temperature. Their electrical parameters and their response to α and β particles were measured. The charge collection efficiency attains a plateau at around 300 V. The irradiation set-up and the results of the measurements are presented in this paper.