Installation and first commissioning results of the JEF lead tungstate calorimeter

TL;DR

This paper reports the installation and first commissioning results of a lead tungstate PbWO4 electromagnetic calorimeter (ECAL) for the Jefferson Lab Eta Factory experiment, replacing the inner GlueX forward calorimeter to achieve higher granularity and improved energy resolution. It details the modular ECAL design with 1596 crystals, a modified PMT active-base readout, and a light monitoring system, all integrated into the GlueX trigger and data acquisition framework and cooled with a water-based system. The initial commissioning used the light monitoring system and cosmic rays to equalize module responses and set HV across channels, enabling data-taking in spring 2025. The work demonstrates a successful large-scale PbWO4 calorimeter deployment at JLab, with implications for enhanced photon detection in multi-photon eta decays and related photoproduction studies.

Abstract

The Electromagnetic Calorimeter (ECAL), consisting of 1,596 lead tungstate scintillating crystals, has been recently constructed and installed in Experimental Hall D at Jefferson Lab (JLab). The calorimeter is a key component of the JLab Eta Factory Experiment, whose main goal is to measure the decays of eta and eta prime mesons into multi-photon final states. The ECAL replaces the inner part of the former forward lead-glass calorimeter. Scintillation light from each crystal is detected using Hamamatsu R4125 photomultiplier tubes. Calorimeter modules were fabricated and tested in the lab using light from light-emitting diodes before being installed in the detector frame. The detector is currently undergoing commissioning using the light monitoring system and cosmic rays. We will present an overview of the fabrication and testing of the calorimete modules, along with the first detector commissioning results. The ECAL was ready for data-taking in spring 2025.

Figures (8)

• Figure 1: Lead glass and lead tungstate modules.
• Figure 2: Assembled ECAL modules.
• Figure 3: Setup for testing ECAL dividers and assembled modules using the light monitoring system. The signal waveform induced by the LMS is digitized by a flash ADC (right). The flash ADC operates at a sampling rate of 250 MHz, corresponding to a sample interval of 4 ns.
• Figure 4: Installing ECAL in experimental Hall D. The ECAL modules at the center are surrounded by lead-glass modules.
• Figure 5: Installation of optical fibers for the light monitoring system. Each individual fiber is glued to the crystal on the front face of an ECAL module. The central hole in the plot corresponds to the beam hole.