Development of the CEPC analog hadron calorimeter prototype

TL;DR

The paper reports the design, construction, and commissioning of a 40-layer analogue hadron calorimeter (AHCAL) prototype for the Circular Electron Positron Collider (CEPC), intended to support particle flow algorithm (PFA)–based jet reconstruction. It details the 40×40×3 mm^3 scintillator tiles read out by silicon photomultipliers (SiPMs) and SPIROC2E ASICs, the 40 absorber plates, and the 12,960-channel readout and calibration infrastructure (HBUs, DIFs, DAQ, LEDs, and temperature sensors). Electronic and cosmic-ray tests demonstrate pedestal stability, gain calibration, and a typical MIP response near 17 photoelectrons with ~97% per-layer efficiency, validating readiness for the beam tests conducted in 2022–2023. Beam-test data are anticipated to deepen understanding of hadron showers and to validate the PFA approach, ultimately guiding refinements to the CEPC detector design.

Abstract

The Circular Electron Positron Collider (CEPC) is a next-generation electron$-$positron collider proposed for the precise measurement of the properties of the Higgs boson. To emphasize boson separation and jet reconstruction, the baseline design of the CEPC detector was guided by the particle flow algorithm (PFA) concept. As one of the calorimeter options, the analogue hadron calorimeter (AHCAL) was proposed. The CEPC AHCAL comprises a 40-layer sandwich structure using steel plates as absorbers and scintillator tiles coupled with silicon photomultipliers (SiPM) as sensitive units. To validate the feasibility of the AHCAL option, a series of studies were conducted to develop a prototype. This AHCAL prototype underwent an electronic test and a cosmic ray test to assess its performance and ensure it was ready for three beam tests performed in 2022 and 2023. The test beam data is currently under analysis, and the results are expected to deepen our understanding of hadron showers, validate the concept of Particle Flow Algorithm (PFA), and ultimately refine the design of the CEPC detector.

Figures (14)

• Figure 1: The overview of the CEPC baseline detector concept. In the barrel from inner to outer, the detector is composed of a silicon pixel vertex detector, a silicon inner tracker, a TPC, a silicon wrapper, an Electromagnetic Calorimeter(ECAL), a Hadronic Calorimeter(HCAL), a solenoid of 3 Tesla and a return yoke with embedded a muon detector.CEPC_CDR2.
• Figure 2: The scintillator-steel sandwich structure of the AHCAL prototype. The scintillator tiles and PCB board were housed within the steel cassette, creating a sensitive layer for the AHCAL.
• Figure 3: (a) The schematic layout of the AHCAL scintillator tile, with a groove at the bottom to accommodate the SiPM and LED. (b) A scintillator tile wrapped with the ESR film. (c) The scintillator light response to Sr-90, from which the light yield of the scintillator was analyzed.
• Figure 4: (a) Overview of the electronic PCBs: the DAQ board(top left), the HBU without scintillator(top right), the HBU assembled with scintillator(bottom left), the electronic side of the HBU and the DIF board(bottom right). (b) The sensitive unit on HBU. (c) The SPIROC2E chip on HBU.
• Figure 5: (a)The design of the SPIROC2E chip, including 36 analog channels and a 12-bit Wilkinson ADCSPIROC2. (b) Parallel readout scheme of 9 SPIROC2E chips in a single AHCAL layerZhou_2023. (c) Schematic view of the readout and data acquisition, involving 40 DIF boards and a DAQ board.