Development of Slow Control Boards for the Large Size Telescopes of the Cherenkov Telescope Array

TL;DR

This paper describes the development and testing of slow control boards for the Large Size Telescopes of the Cherenkov Telescope Array, enabling control, monitoring, and testing of photomultiplier modules.

Contribution

The paper introduces a novel slow control board design that manages high voltages, monitors currents, and generates test pulses for CTA's LST camera modules.

Findings

Successful control and monitoring of PMTs achieved

Test pulses effectively emulate PMT signals for testing

Design validated through test measurements

Abstract

The camera of the Large Size Telescopes (LSTs) of the Cherenkov Telescope Array (CTA) consists of 265 photosensor modules, each of them containing 7 photomultiplier tubes (PMTs), a slow control board (SCB), a readout board, and a trigger logic. We have developed the SCB, which is installed between the 7 PMTs and the readout board. The main task for SCBs is the controlling of the high voltages for the PMTs and the monitoring of their anode currents. In addition, the SCB provides the functionality to create test pulses that can be injected at the input of the PMT preamplifier in order to emulate a PMT signal without the need of setting a high voltage, or even without the PMT itself. The test pulses have a very similar width as the PMT pulses (less than 3 ns FWHM) and their amplitude can be adjusted in a wide dynamic range. These features allow us not only to test the functionality of the camera modules but also to fully characterize these. We report on the design and the functions of the SCB together with the results of test measurements.