Speaker
Description
The High Voltage (HV) system of TileCal, the ATLAS central hadron calorimeter, needs to be upgraded during the so called Phase II Upgrade of the LHC for the HL-LHC. In thw proposed solution, the HV regulation boards are moved away from the detector and deployed in the counting room, safe from radiation damages and with permanent access for maintenance. This option requires a new layout with HV cables about 100 m long, but removes the requirement of radiation hard boards. HV-remote regulation boards have been developed and tested. Preliminary results of the performance will be presented.
Summary
The High Voltage (HV) system of TileCal for the HL-LHC will consist of HV-remote boards, located far from the detector in the ATLAS counting room and connected to the detector by 100 m long cables. Inside the detector passive HV-bus boards there will be used to bring the HV to each photomultiplier tubes (PMTs) located in mini-drawers inside the girders of the modules.
The HV-remote boards are the boards that regulate the HV for each individual PMT. In total, 256 boards are needed for the TileCal operations. Each input HV (of -830 or -950 V) can serve up to 24 PMTs and the voltage of each PMT can be decreased individually in a range of the order of 350V, as in the current TileCal design [1]. The boards are intended to use two primary HV inputs to provide HV for 48 PMTs in the case of the TileCal central barrel modules and 32 PMTs in the case of the two TileCal Extended Barrel. Relative to the current HV system, the main functional improvement is the addition of individual on/off controls for each individual PMT. The operation in the absence of radiation allows the simplification of the regulation loops with the removal of some electronic components. The control and monitoring, that in the current TileCal design is done with HV-micro boards [1] communicating with the ATLAS Detector Control System via CANbus architecture, will be completely redone.
The first prototype generation of the HV-remote boards has been produced to operate 24 PMTs, while he following generation will operate 48 PMTs. The communication and control is done via SPI bus through an ethernet interface. The first prototype boards use Tibbo EM1206 modules as interface, and it is intended that the final version uses a System on Chip solution.
The primary HV is provided by Hamamatsu C12446-12 modules, installed inside boards located in the ATLAS counting room..
HV-remote boards prototypes have been tested in the laboratory and results on stability, sensitivity to temperature, etc, will be presented. Problems identified in the first prototypes during the tests, will result in changes in the design of the following generations that will be discussed.
[1] R. Chadelas et al., "High voltage distributor system for the Tile hadron calorimeter of the ATLAS detector", ATLAS-TILECAL-2000-003, 2000, https://cds.cern.ch/record/436230
