The high voltage system with pressure and temperature corrections for the novel MPGD-based photon detectors of COMPASS RICH-1

Abstract

The novel MPGD-based photon detectors of COMPASS RICH-1 consist of large-size hybrid MPGDs with multilayer architecture including two layers of Thick-GEMs and a bulk resistive MicroMegas. The top surface of the first THGEM is coated with a CsI film which also acts as photo-cathode. These detectors have been successfully in operation at COMPASS since 2016. Concerning bias-voltage supply, the Thick-GEMs are segmented in order to reduce the energy released in case of occasional discharges, while the MicroMegas anode is segmented into pads individually biased with positive voltage while the micromesh is grounded. In total, there are about ten different electrode types and more than 20000 electrodes supplied by more than 100 HV channels, where appropriate correlations among the applied voltages are required for the correct operation of the detectors. Therefore, a robust control system is mandatory, implemented by a custom designed software package, while commercial power supply units are used. This sophisticated control system allows to protect the detectors against errors by the operator, to monitor and log voltages and currents at 1 Hz rate, and automatically react to detector misbehaviour. In addition, a voltage compensation system has been developed to automatically adjust the biasing voltage according to environmental pressure and temperature variations, to achieve constant gain over time. This development answers to a more general need. In fact, voltage compensation is always a requirement for the stability of gaseous detectors and its need is enhanced in multi-layer ones.In this paper, the HV system and its performance are described in details, as well as the stability of the novel MPGD-based photon detectors during the physics data taking at COMPASS.

MPGD-based photon detectors for the upgrade of COMPASS RICH-1 and beyond

“…A typical discharge rate of few events per day is seen. No sizable voltage drop is observed when a discharge occurs, confirming the validity of the design of the HV distribution system [16]. In Fig.…”

A scalable High Voltage Power Supply System with system on chip control for Micro Pattern Gaseous Detectors

“…The SoC FPGA board selected for prototyping and software development purposes is the ZedBoard. 12 The choice is based on the analysis of the resources required by the system design tasks. The ZedBoard is based on the modern hybrid fully-programmable System-on-Chip (SoC) 12 https://www.xilinx.com/products/boards-and-kits/1-8dyf-11.html device Zynq-7020, which combines a 'hard' dual core ARM Cortex-A9 processor with an Artix-7 FPGA fabric.…”

“…12 The choice is based on the analysis of the resources required by the system design tasks. The ZedBoard is based on the modern hybrid fully-programmable System-on-Chip (SoC) 12 https://www.xilinx.com/products/boards-and-kits/1-8dyf-11.html device Zynq-7020, which combines a 'hard' dual core ARM Cortex-A9 processor with an Artix-7 FPGA fabric. The SoC manages the ADC, performing a fast post processing of the data to tag those events whose digitized waveforms are saved and sent via Ethernet for offline data analysis.…”

“…The correction algorithm depends on the detector characteristics and it is the result of dedicated laboratory tuning exercises. An example is provided in [12], where the following correction equation is introduced:…”

Multichannel Time Synchronization Based on PTP through a High Voltage Isolation Buffer Network Interface for Thick-GEM Detectors

“…Changes of pressure and temperature cause gain variations and are more severe in the case of multistage detectors. Segmentation of the electrodes adds further elements of complexity in the HV system [3]. An active High Voltage Power Supply System (HVPSS) based on Field Programmable Gate Array, System on Chip (FPGA/SoC) suited for MPGD technologies has been designed and tested as a step towards multichannel applications [4].…”