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Performance of the High-Angle Time Projection Chambers in the Upgraded T2K Off-Axis Near Detector

K. Aivazelis, D. Attié, P. Billoir, A. Blanchet, G. Bortolato, S. Bolognesi, R. Boullon, N. F. Calabria, D. Calvet, M. P. Casado, M. G. Catanesi, M. Cicerchia, G. Cogo, G. Collazuol, P. Colas, D. Cotte, D. D'Ago, C. Dalmazzone, T. Daret, R. de Oliveira, A. Delbart, J. Dumarchez, K. Dygnarowicz, S. Emery-Schrenk, A. Ershova, G. Eurin, M. Feltre, C. Forza, A. N. Gacino Olmedo, A. Gambalonga, C. Giganti, F. Gramegna, P. Granger, R. Guida, M. Guigue, S. Hassani, D. Henaff, F. Iacob, C. Jesús-Valls, S. Joshi, R. Kurjata, M. Lamoureux, J. F. Laporte, M. Lehuraux, S. Levorato, A. Longhin, T. Lux, L. Magaletti, T. Marchi, D. Marchesini, L. Mareso, M. Mattiazzi, M. Mezzetto, B. Mehl, E. Miller, L. Mellet, L. Munteanu, Q. V. Nguyen, N. Ospina, Y. Orain, R. Palumbo, C. Pastore, J. -M. Parraud, E. Pierre, C. Pio, O. Pizzirusso, B. Popov, F. Pupilli, E. Radicioni, Ch. Riccio, L. Rinaldi, F. Rossi, S. Roth, L. Russo, S. Russo, A. Rychter, W. Saenz Arevalo, L. Scomparin, Ph. Schune, D. Smyczek, R. Spina, J. Steinmann, S. Suvorov, N. Thamm, D. Terront, A. Teixeira, F. Toussenel, V. Valentino, D. Vargas, M. Varghese, G. Vasseur, C. Vuillemin, U. Virginet, Ch. Winterstein, U. Yevarouskaya, M. Ziembicki, M. Zito

TL;DR

This work documents the construction and first-performance evaluation of two high-angle TPCs (HA-TPCs) in the upgraded T2K ND280 near detector, featuring resistive Micromegas readouts (ERAM) and a lightweight field cage. It details the integrated electronics, gas system with continuous monitoring via gas-monitoring chambers, and a full reconstruction/simulation chain that models drift, diffusion, charge spread, and electronics shaping. Results from neutrino-beam and cosmic-ray data show spatial resolution better than $0.8~\text{mm}$ and $dE/dx$ resolution below $10\%$ across track angles and drift distances, with momentum reconstruction consistent with expectations and validated against multiple magnetic-field maps. The study demonstrates reliable detector performance and robust data–MC agreement, enabling the HA-TPCs to deliver improved flux constraints and reduced systematic uncertainties for T2K oscillation measurements.

Abstract

The off-axis magnetic near detector of the T2K experiment has undergone a significant upgrade, including the construction and installation of two new Time Projection Chambers featuring innovative resistive Micromegas technology and a field cage composed of thin composite walls. This paper provides a detailed description of the new components of the chambers, including the gas system, gas monitoring chambers, and data acquisition system. Additionally, it reports the results of extensive testing using both neutrino beams and cosmic rays, with comparisons between data and Monte Carlo simulations. The new detectors achieve improved spatial resolution and enhanced particle identification capabilities which are crucial for the precision goals of the T2K experiment.

Performance of the High-Angle Time Projection Chambers in the Upgraded T2K Off-Axis Near Detector

TL;DR

This work documents the construction and first-performance evaluation of two high-angle TPCs (HA-TPCs) in the upgraded T2K ND280 near detector, featuring resistive Micromegas readouts (ERAM) and a lightweight field cage. It details the integrated electronics, gas system with continuous monitoring via gas-monitoring chambers, and a full reconstruction/simulation chain that models drift, diffusion, charge spread, and electronics shaping. Results from neutrino-beam and cosmic-ray data show spatial resolution better than and resolution below across track angles and drift distances, with momentum reconstruction consistent with expectations and validated against multiple magnetic-field maps. The study demonstrates reliable detector performance and robust data–MC agreement, enabling the HA-TPCs to deliver improved flux constraints and reduced systematic uncertainties for T2K oscillation measurements.

Abstract

The off-axis magnetic near detector of the T2K experiment has undergone a significant upgrade, including the construction and installation of two new Time Projection Chambers featuring innovative resistive Micromegas technology and a field cage composed of thin composite walls. This paper provides a detailed description of the new components of the chambers, including the gas system, gas monitoring chambers, and data acquisition system. Additionally, it reports the results of extensive testing using both neutrino beams and cosmic rays, with comparisons between data and Monte Carlo simulations. The new detectors achieve improved spatial resolution and enhanced particle identification capabilities which are crucial for the precision goals of the T2K experiment.

Paper Structure

This paper contains 33 sections, 16 equations, 29 figures.

Table of Contents

  1. Introduction
  2. Field Cage Description and Performance
  3. Metrology and mechanical performance
  4. Metrology Measurements
  5. Mechanical Performance Tests
  6. Electrical Performance
  7. Electric field in HA-TPCs
  8. Readout Description and Performance
  9. Readout production
  10. ERAMs Performance
  11. Electronics
  12. Front-End Cards
  13. Front-End Mezzanine cards
  14. Back-end electronics
  15. Slow Control and DAQ
  16. ...and 18 more sections

Figures (29)

  • Figure 1: Schematic view of the upgraded ND280 installed in the opened magnet. The newly installed subdetectors are located in the left part of the drawing: two horizontal top and bottom HA-TPCs (black boxes) surround the new highly segmented Super-FGD active target (grey box). The top TOF panel is also visible. The original tracking system of the ND280 -- three vertical TPCs (yellow boxes) and two FGDs (blue boxes) -- is also shown. The J-PARC neutrino beam is coming from the left. Cosmic rays traverse the detector vertically. The coordinate reference system used for ND280 is also shown. The $x$-axis is parallel to the magnetic field, the $y$-axis is opposite to gravity, and the $z$-axis is along the incoming neutrino beam.
  • Figure 2: Cross section of the field cage, showing a schematic view of the copper strips connected by voltage dividers from cathode to anode. (not to scale)
  • Figure 3: Electric field norm ($\pm5\%$) around the nominal 1 V/m value.
  • Figure 4: Operating principle of Resistive Micromegas. The various detector elements are indicated. The glue thickness is optimized to achieve a consistent $RC$ value for each detector Ambrosi:2023smx.
  • Figure 5: Left: a photo of the upgraded sub-detectors installed in ND280, Right: the various ERAM detectors with their location, average gain and RC values.
  • ...and 24 more figures