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Lead tungstate calorimeter of the Jefferson Lab Eta Factory experiment

Alexander Somov

TL;DR

This work documents the design, fabrication, and integration of a lead tungstate electromagnetic calorimeter (ECAL) for the Jefferson Lab Eta Factory experiment. The 1596 PbWO4 crystals are arranged in a 40 × 40 module grid to replace the inner GlueX forward calorimeter, with a tungsten absorber and a refined cooling system to maintain stable light yield at ~17 °C. The ECAL integrates with the GlueX trigger via 12-bit, 250 MHz flash ADCs, FPGA-based pipelines, and a dedicated trigger processor, and it employs an LED-based light monitoring system for stability. The commissioning is underway, with first physics runs planned for January 2025, enabling improved forward-photon reconstruction and expanded physics reach for rare eta decays and related searches.

Abstract

A new electromagnetic calorimeter (ECAL) consisting of 1596 lead tungstate PbWO$_{\rm 4}$ scintillating crystals has been fabricated and installed in the experimental Hall D at Jefferson Lab (JLab). The high-granularity, high-resolution calorimeter is required by the JLab Eta Factory experiment, whose main physics goal is to study rare decays of eta mesons. The ECAL replaced the inner part of the forward lead glass calorimeter of the GlueX detector. Signals from the detector will be digitized using twelve-bit flash analog-to-digital converters operated at a sampling rate of 250 MHz. The ECAL is integrated into the trigger system of the GlueX detector using electronics modules designed at JLab. The ECAL is currently at the commissioning stage and should be ready for the physics run in January 2025. We will give an overview of the JEF experiment, the design and construction of the ECAL, and the integration of the detector and its infrastructure into the Hall D experimental setup.

Lead tungstate calorimeter of the Jefferson Lab Eta Factory experiment

TL;DR

This work documents the design, fabrication, and integration of a lead tungstate electromagnetic calorimeter (ECAL) for the Jefferson Lab Eta Factory experiment. The 1596 PbWO4 crystals are arranged in a 40 × 40 module grid to replace the inner GlueX forward calorimeter, with a tungsten absorber and a refined cooling system to maintain stable light yield at ~17 °C. The ECAL integrates with the GlueX trigger via 12-bit, 250 MHz flash ADCs, FPGA-based pipelines, and a dedicated trigger processor, and it employs an LED-based light monitoring system for stability. The commissioning is underway, with first physics runs planned for January 2025, enabling improved forward-photon reconstruction and expanded physics reach for rare eta decays and related searches.

Abstract

A new electromagnetic calorimeter (ECAL) consisting of 1596 lead tungstate PbWO scintillating crystals has been fabricated and installed in the experimental Hall D at Jefferson Lab (JLab). The high-granularity, high-resolution calorimeter is required by the JLab Eta Factory experiment, whose main physics goal is to study rare decays of eta mesons. The ECAL replaced the inner part of the forward lead glass calorimeter of the GlueX detector. Signals from the detector will be digitized using twelve-bit flash analog-to-digital converters operated at a sampling rate of 250 MHz. The ECAL is integrated into the trigger system of the GlueX detector using electronics modules designed at JLab. The ECAL is currently at the commissioning stage and should be ready for the physics run in January 2025. We will give an overview of the JEF experiment, the design and construction of the ECAL, and the integration of the detector and its infrastructure into the Hall D experimental setup.

Paper Structure

This paper contains 7 sections, 5 figures.

Table of Contents

  1. Introduction
  2. Calorimeter design
  3. Module design
  4. Electronics and trigger system
  5. Light monitoring system
  6. Summary
  7. Acknowledgments

Figures (5)

  • Figure 1: The frame of the GlueX forward calorimeter with the ECAL modules (brown rectangular area in the center) surrounded by lead glass modules (green). The photon beam passes through the hole in the middle of the ECAL. The innermost layer of the ECAL is covered by an absorber, shown as a light green area in the center of the ECAL.
  • Figure 2: Installation of the ECAL modules on the GlueX forward calorimeter. The original calorimeter frame after removing all lead glass modules (left). Installation of the ECAL surrounded by the lead glass modules (middle). Installed calorimeter with the ECAL in the center of the detector (right).
  • Figure 3: Assembled ECAL module with the attached PMT active base with signal, high voltage, and low voltage cables (left plot). Main components of the ECAL module (right plot): the PbWO$_{\rm 4}$ crystal wrapped with the ESR reflective foil and Tedlar, PMT with the light guide, PMT housing, brass-strip assembly, and mu-metal shielding.
  • Figure 4: PMT active bases designed at Jefferson lab (left). Installation of the active bases on the ECAL PMTs (right). Each base is connected to signal, high voltage, and low voltage cables.
  • Figure 5: Installation of the LMS optical fibers. Optical fiber is glued to each PbWO$_4$ crystal through the hole in the flange on the face of the crystal.