RHIP, a radio-controlled high-voltage insulated picoammeter
A picoammiter system has been developed by prototyping and engineering. It consists in a current-voltage converter, based on an operational amplifier with very low input current, a high precision ADC, a radio controlled data acquisition unit and the computer-based control, visualization and storage. The picoammiter is characterized by a precision of the order of a tenth of picoamperes and it can measure currents between points laying at potentials of the order of a ten of kilovolts. The current-voltage converter and the radio transmitter are battery powered and a number of strategies have been implemented to limit the power consumption. The system is designed for multichannel application and up to 256 parallel channels can be controlled. The overall implementation is cost-effective to make the availability of multichannel setups easily affordable. The design, implementation and performance of the picoammiter system are described.
The novel photon detectors based on MPGD technologies for the upgrade of COMPASS RICH-1
The RICH-1 Detector of the COMPASS experiment at CERN SPS has undergone an important upgrade in 2016. Four new photon detectors, based on MPGD technology and covering a total active area larger than 1.2~$m^2$ have replaced the previously used MWPC-based photon detectors. The new detector architecture, resulting from a dedicated, eight years long, R\D the first THGEM, coated with a CsI layer, acts as a reflective photocathode. The signals are extracted from the anode pads by capacitive coupling and read-out by analog front-end electronics based on the APV25 chip. The new COMPASS RICH-1 photon detectors are described in detail: the detector design, the engineering aspects, the mass production, and the quality assessment are discussed. The assembly of the MPGD components and the installation of the new detectors are illustrated together with the main aspects of the commissioning. Preliminary indication of performance results are also presented.
The high voltage system for the novel MPGD-based photon detectors of COMPASS RICH-1
The architecture of the novel MPGD-based photon detectors of COMPASS RICH-1 consists in a large-size hybrid MPGD multilayer layout combining two layers of Thick-GEMs and a bulk resistive MICROMEGAS. Concerning biasing voltage, the Thick-GEMs are segmented in order to reduce the energy released in case of occasional discharges, while the MICROMEGAS anode is segmented in pads individually biased at positive voltage, while the micromesh is grounded. In total, there are ten different electrode types and more than 20000 electrodes supplied by more than 100 HV channels. Commercial power supply units are used. The original elements of the power supply system are the architecture of the voltage distribution net, the compensation, by voltage adjustment, of the effects of pressure and temperature variation affecting the detector gain and a sophisticated control software, which allows to protect the detectors against errors by the operator, to monitor and log voltages and current at 1 Hz rate and to automatically react to detector misbehaviors. The HV system and its performance are described in detail as well as the electrical stability of the detector during the operation at COMPASS.