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arxiv: 2606.21443 · v1 · pith:XYH2SYAJnew · submitted 2026-06-19 · ⚛️ physics.ins-det

Test of the JUNO 20-inch PMTs during Installation

Haojie Dong , Zhaoyuan Peng , Zhonghua Qin , Wan Xie , Haoqi Lu , Jun Hu , Lei Fan , Xiaoshan Jiang
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Chao Chen Xiaolu Ji Fei Li Shenghui Liu Xiaochuan Xie Mei Ye Hongzhao Yu Zeyuan Yu
This is my paper

Pith reviewed 2026-06-26 12:45 UTC · model grok-4.3

classification ⚛️ physics.ins-det
keywords JUNOPMT20-inch photomultiplier tubeneutrino detectorinstallation testdark count rategain measurementcharge spectrum
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The pith

JUNO installed and tested over 20,000 20-inch PMTs with seven measurement campaigns from 2022 to 2024.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

This paper describes the installation of more than 20,000 20-inch photomultiplier tubes in the JUNO neutrino observatory between October 2022 and December 2024. The authors detail seven test campaigns that measured dark count rate, gain, waveform, and charge spectrum to confirm each PMT met operational standards. These checks support the detector's goal of achieving 3 percent energy resolution at 1 MeV using a 20 kton liquid scintillator volume. Readers care because the large number of PMTs must function reliably for the experiment to collect useful neutrino data.

Core claim

The 20-inch PMTs were successfully installed in JUNO from October 2022 to December 2024. During the installation, seven test campaigns were performed to validate the PMT functionality, including measurements of dark count rate, gain, waveform, and charge spectrum. The paper presents the implementation of these tests and the corresponding results for the 20-inch PMTs throughout the installation process.

What carries the argument

Seven sequential test campaigns that measured dark count rate, gain, waveform shape, and charge spectrum on the installed 20-inch PMTs.

If this is right

  • The PMTs meet the functional requirements needed for JUNO data taking.
  • The test results provide baseline values for later calibration and monitoring.
  • The installation sequence and test procedures can be applied to the remaining 3-inch PMTs.
  • Consistent performance across campaigns indicates the PMTs survived transport and mounting without damage.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • If the installation tests prove representative, the full detector can reach its design energy resolution without major PMT-related corrections.
  • The collected test data set offers a reference for predicting how similar large PMT arrays might behave in other underground neutrino detectors.
  • Routine re-testing of a subset of PMTs after filling would directly test whether installation conditions match operating conditions.

Load-bearing premise

Measurements taken during installation will continue to represent PMT performance once the detector is filled and operating long-term.

What would settle it

A post-filling calibration run that finds the average dark count rate or gain of a statistically significant sample of PMTs has shifted beyond the range recorded in the seven installation campaigns.

read the original abstract

Photomultiplier tubes (PMTs) are widely used in neutrino experiments. As a new-generation neutrino observatory, JUNO requires an excellent energy resolution of 3% at 1 MeV. This will be realized with a 20 kton liquid scintillator detector instrumented with more than 20000 20-inch PMTs and 25600 3-inch PMTs. These PMTs were successfully installed in JUNO from October 2022 to December 2024. During the installation, seven test campaigns were performed to validate the PMT functionality, including measurements dark count rate, gain, waveform, and charge spectrum. In this paper, we present the implementation of these tests and the corresponding results for the 20-inch PMTs throughout the installation process.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

0 major / 2 minor

Summary. The paper reports that more than 20,000 20-inch PMTs were successfully installed in the JUNO detector from October 2022 to December 2024. During installation, seven test campaigns were conducted to validate PMT functionality via measurements of dark count rate, gain, waveform, and charge spectrum; the manuscript describes the test implementation and presents the corresponding results for the 20-inch PMTs.

Significance. If the reported test procedures and results hold, the work supplies a useful technical record of quality-assurance measurements performed on a critical detector component during construction of the JUNO neutrino observatory, which targets 3% energy resolution at 1 MeV. Such documentation aids future experiments in understanding installation-phase performance validation for large PMT arrays.

minor comments (2)
  1. [Abstract] Abstract: the abstract states that results are presented but supplies no numerical values, uncertainties, or summary statistics for dark count rate, gain, or other quantities; adding one or two representative numbers would improve the summary.
  2. The manuscript would benefit from a short table or figure summarizing the aggregate statistics (e.g., mean dark count rate and its spread across all tested PMTs) rather than only campaign-by-campaign descriptions.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for the careful review and the positive assessment of our manuscript on the JUNO 20-inch PMT testing during installation. The recommendation for minor revision is noted; however, no specific major comments were provided in the report.

Circularity Check

0 steps flagged

No significant circularity

full rationale

The manuscript is a purely descriptive experimental report on PMT installation and seven test campaigns measuring dark count rate, gain, waveform, and charge spectrum. No derivation chain, equations, fitted parameters, or predictions are present in the abstract or described scope; the central claim is a factual account of procedures performed between October 2022 and December 2024. The paper contains no self-citations, ansatzes, or uniqueness theorems that could reduce to inputs by construction. This is the expected outcome for a technical installation/validation paper with no modeling or extrapolation steps.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

The paper is a report on experimental tests with no free parameters fitted, no axioms invoked beyond standard physics, and no invented entities.

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discussion (0)

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Reference graph

Works this paper leans on

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