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The Super Fine-Grained Detector for the T2K neutrino oscillation experiment

S. Abe, H. Alarakia-Charles, I. Alekseev, T. Arai, T. Arihara, S. Arimoto, A. M. Artikov, Y. Awataguchi, N. Babu, V. Baranov, G. Barr, D. Barrow, L. Bartoszek, A. Beliakova, L. Bernardi, L. Berns, S. Bhattacharjee, A. V. Boikov, A. Blondel, A. Bonnemaison, F. Cadoux, S. Cap, A. Cauchois, J. Chakrani, P. S. Chong, A. Chvirova, M. Danilov, C. Davis, V. Davouloury, Yu. I. Davydov, A. Dergacheva, C. Domangue, D. Douqa, T. A. Doyle, O. Drapier, A. Eguchi, J. Elias, G. Erofeev, Y. Favre, D. Fedorova, S. Fedotov, D. Ferlewicz, Y. Fujii, R. Fujita, Y. Furui, F. Gastaldi, A. Gendotti, A. Germer, L. Giannessi, C. Giganti, V. Glagolev, R. Guillaumat, I. Heitkamp, J. Hu, C. Husi, A. K. Ichikawa, T. H. Ishida, A. Izmaylov, K. Iwamoto, M. Jakkapu, C. Jesús-Valls, J. Y. Ji, J. Juneau, C. K. Jung, H. Kakuno, M. Kawaue, P. T. Keener, M. Khabibullin, N. V. Khomutov, A. Khotjantsev, T. Kikawa, H. Kikutani, N. V. Kirichkov, H. Kobayashi, T. Kobayashi, L. Koch, S. Kodama, A. O. Kolesnikov, M. Kolupanova, T. Koto, Y. Kudenko, S. Kuribayashi, T. Kutter, M. Lachat, K. Lachner, M. Lamers James, D. Last, N. Latham, D. Leon Silverio, B. Li, W. Li, C. Lin, M. Louzir, T. Lux, K. K. Mahtani, S. Manly, D. A. Martinez Caicedo, N. Mashin, T. Matsubara, C. Mauger, K. S. McFarland, C. McGrew, J. McKean, A. Mefodiev, E. Miller, O. Mineev, A. Minamino, A. L. Moreno, A. Muñoz, T. Nakadaira, K. Nakagiri, T. Nakaya, J. Nanni, L. Nicolas, V. Nguyen, E. Noah Messomo, T. Nosek, H. M. O'Keeffe, T. Ogawa, W. Okinaga, L. Osu, V. Paolone, G. Pelleriti, L. Pickering, M. A. Ramírez, M. Reh, G. Reina, C. Riccio, A. Rubbia, F. Saadi, K. Sakashita, N. Sallin, F. Sanchez, T. Schefke, C. Schloesser, D. Sgalaberna, A. Shaikovskiy, N. Shvarev, A. Shvartsman, Y. Shiraishi, N. Skrobova, A. Speers, M. Smy, D. Svirida, S. Tairafune, M. Tani, H. Tanigawa, A. Teklu, S. Tereshchenko, V. V. Tereshchenko, T. Tsushima, M. Tzanov, R. Van Berg, I. I. Vasilyev, T. Vladisavljevic, D. Wakabayashi, H. Wallace, A. Weber, N. Whitney, C. Wret, Y. Xu, Y. Yang, N. Yershov, A. J. P. Yrey, M. Yokoyama, Y. Yoshimoto, X. Y. Zhao, H. Zheng, H. Zhong, T. Zhu, E. D. Zimmerman, M. Zito

Abstract

The magnetised near detector ND280 of the long-baseline neutrino experiment T2K has been upgraded to improve its detection performance and, consequently, enhance our understanding of neutrino-nucleus interactions, reducing the systematic uncertainties in measurements of the neutrino oscillation parameters. A key component of the upgrade is a novel segmented plastic scintillator detector, called the Super Fine-Grained Detector (SuperFGD), made of approximately 2 million optically isolated 1 cm$^3$ cubes read out by three orthogonal wavelength-shifting (WLS) fibres. Scintillation photons are detected by 55,888 Hamamatsu Multi-Pixel Photon Counters (MPPCs). The SuperFGD provides 3D images of neutrino interactions by tracking the final-state charged particles produced isotropically, including protons down to a threshold of around 330 MeV/$c$. The high light yield of SuperFGD greatly improves particle identification and the sub-nanosecond time resolution provides an excellent identification of Michel electrons. The SuperFGD is also able to detect neutrons from neutrino interactions and, for the first time in a neutrino experiment, to reconstruct their kinetic energy using a fine detector segmentation and by measuring the time-of-flight with sub-nanosecond precision. In this article the details of the detector design, construction and performance are described. The detector was installed in ND280 and successfully commissioned with cosmic data in 2023 and, later, with the T2K neutrino beam. The detector response has been characterised with the 2023 and 2024 data and the results are reported in this article.

The Super Fine-Grained Detector for the T2K neutrino oscillation experiment

Abstract

The magnetised near detector ND280 of the long-baseline neutrino experiment T2K has been upgraded to improve its detection performance and, consequently, enhance our understanding of neutrino-nucleus interactions, reducing the systematic uncertainties in measurements of the neutrino oscillation parameters. A key component of the upgrade is a novel segmented plastic scintillator detector, called the Super Fine-Grained Detector (SuperFGD), made of approximately 2 million optically isolated 1 cm cubes read out by three orthogonal wavelength-shifting (WLS) fibres. Scintillation photons are detected by 55,888 Hamamatsu Multi-Pixel Photon Counters (MPPCs). The SuperFGD provides 3D images of neutrino interactions by tracking the final-state charged particles produced isotropically, including protons down to a threshold of around 330 MeV/. The high light yield of SuperFGD greatly improves particle identification and the sub-nanosecond time resolution provides an excellent identification of Michel electrons. The SuperFGD is also able to detect neutrons from neutrino interactions and, for the first time in a neutrino experiment, to reconstruct their kinetic energy using a fine detector segmentation and by measuring the time-of-flight with sub-nanosecond precision. In this article the details of the detector design, construction and performance are described. The detector was installed in ND280 and successfully commissioned with cosmic data in 2023 and, later, with the T2K neutrino beam. The detector response has been characterised with the 2023 and 2024 data and the results are reported in this article.
Paper Structure (57 sections, 4 equations, 58 figures, 6 tables)

This paper contains 57 sections, 4 equations, 58 figures, 6 tables.

Table of Contents

  1. Introduction
  2. General description of the SuperFGD
  3. Scintillator cubes
  4. Design and production of cubes
  5. Geometry of the cubes
  6. Selection of cubes using rods and fishing lines
  7. Making strings with 192 cubes
  8. Making a layer of strings with 192$\times$182 cubes
  9. Pre-assembly of a 3D array out of 56 cube layers
  10. Evaluation of assembly procedure
  11. 3D cube assemblies
  12. Total size of the SuperFGD cube array
  13. Tower tests
  14. SuperFGD mechanics
  15. Box plates and structure
  16. ...and 42 more sections

Figures (58)

  • Figure 1: The T2K near detector ND280 before the upgrade (left). The PØ D is replaced by new detectors HA-TPCs, SuperFGD, and ToF after the upgrade (right).
  • Figure 2: Left: A zoom view a scintillator cube with three orthogonal holes with a diameter of 1.5 mm. Two sides of the cube polished to see the holes, four sides a covered by a reflector. Right: Scintillator cubes before and after chemical etching. A trace from the injection mould pusher is seen at the top of both cubes.
  • Figure 3: Variation of the hole position at the drill entrance point. Top left: the variation of length L1. Bottom left: displacement of holes L1--L2. Bottom right: tilt of channels L1--L3. Top right: cube sketch with the definitions of each length.
  • Figure 4: A 15$\times$15 array of cubes on knitting needles used to check the orthogonality of cube holes.
  • Figure 5: Two halves of a cube layer (192$\times$91 cubes each) with welding rods just before assembly of a full layer. One can see strings of 192 cubes on fishing lines on the top of the right half.
  • ...and 53 more figures