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The NEXT-100 Detector

NEXT Collaboration, C. Adams, H. Almazán, V. Álvarez, A. I. Aranburu, L. Arazi, I. J. Arnquist, F. Auria-Luna, S. Ayet, Y. Ayyad, C. D. R. Azevedo, K. Bailey, F. Ballester, J. E. Barcelon, M. del Barrio-Torregrosa, A. Bayo, J. M. Benlloch-Rodríguez, F. I. G. M. Borges, A. Brodoline, N. Byrnes, A. Castillo, E. Church, L. Cid, M. Cid, X. Cid, C. A. N. Conde, C. Cortes-Parra, F. P. Cossío, R. Coupe, E. Dey, P. Dietz, C. Echeverria, M. Elorza, R. Esteve, R. Felkai, L. M. P. Fernandes, P. Ferrario, F. W. Foss, Z. Freixa, J. García-Barrena, J. J. Gómez-Cadenas, J. W. R. Grocott, R. Guenette, J. Hauptman, C. A. O. Henriques, J. A. Hernando Morata, P. Herrero-Gómez, V. Herrero, C. Hervés Carrete, Y. Ifergan, A. F. B. Isabel, B. J. P. Jones, F. Kellerer, L. Larizgoitia, A. Larumbe, P. Lebrun, F. Lopez, N. López-March, R. Madigan, R. D. P. Mano, A. Marauri, A. P. Marques, J. Martín-Albo, A. Martínez, G. Martínez-Lema, M. Martínez-Vara, R. L. Miller, K. Mistry, J. Molina-Canteras, F. Monrabal, C. M. B. Monteiro, F. J. Mora, K. E. Navarro, P. Novella, D. R. Nygren, E. Oblak, I. Osborne, J. Palacio, B. Palmeiro, A. Para, I. Parmaksiz, A. Pazos, J. Pelegrin, M. Pérez Maneiro, M. Querol, J. Renner, I. Rivilla, C. Rogero, L. Rogers, B. Romeo, C. Romo-Luque, E. Ruiz-Chóliz, P. Saharia, F. P. Santos, J. M. F. dos Santos, M. Seemann, I. Shomroni, A. L. M. Silva, P. A. O. C. Silva, A. Simón, S. R. Soleti, M. Sorel, J. Soto-Oton, J. M. R. Teixeira, S. Teruel-Pardo, J. F. Toledo, C. Tonnelé, S. Torelli, J. Torrent, A. Trettin, P. R. G. Valle, M. Vanga, P. Vázquez Cabaleiro, J. F. C. A. Veloso, J. D. Villamil, J. Waiton, A. Yubero-Navarro

TL;DR

The NEXT-100 detector demonstrates the viability of a high-pressure xenon gas TPC with electroluminescent amplification for neutrinoless double beta decay searches. By integrating a dedicated energy plane of PMTs and a tracking plane of densely packed SiPMs, NEXT-100 achieves precise energy and three-dimensional event reconstruction with strong background discrimination. The paper details the detector’s design, assembly, gas system, radiopurity program, and commissioning results, verifying stable operation, validated gas handling, and sensor calibrations. Collectively, the work confirms the technology’s scalability toward ton-scale experiments and provides a comprehensive foundation for improved background models and future measurements in the NEXT program.

Abstract

The NEXT collaboration is dedicated to the study of double beta decays of $^{136}$Xe using a high-pressure gas electroluminescent time projection chamber. This advanced technology combines exceptional energy resolution ($\leq 1\%$ FWHM at the $Q_{ββ}$ value of the neutrinoless double beta decay) and powerful topological event discrimination. Building on the achievements of the NEXT-White detector, the NEXT-100 detector started taking data at the Laboratorio Subterráneo de Canfranc (LSC) in May of 2024. Designed to operate with xenon gas at 13.5 bar, NEXT-100 consists of a time projection chamber where the energy and the spatial pattern of the ionising particles in the detector are precisely retrieved using two sensor planes (one with photo-multiplier tubes and the other with silicon photo-multipliers). The detector has been operating at stable conditions using argon and xenon gases at $\sim$4 bar and drift fields of 74 V/cm and 118 V/cm, respectively. Alpha decays from the $^{222}$Rn chain have been used to test and monitor the stability of the detector, showing a constant electron lifetime in the drift volume. In this paper, in addition to reporting the results of the commissioning run, we provide a detailed description of the NEXT-100 detector, describe its assembly, and present the current estimation of the radiopurity budget.

The NEXT-100 Detector

TL;DR

The NEXT-100 detector demonstrates the viability of a high-pressure xenon gas TPC with electroluminescent amplification for neutrinoless double beta decay searches. By integrating a dedicated energy plane of PMTs and a tracking plane of densely packed SiPMs, NEXT-100 achieves precise energy and three-dimensional event reconstruction with strong background discrimination. The paper details the detector’s design, assembly, gas system, radiopurity program, and commissioning results, verifying stable operation, validated gas handling, and sensor calibrations. Collectively, the work confirms the technology’s scalability toward ton-scale experiments and provides a comprehensive foundation for improved background models and future measurements in the NEXT program.

Abstract

The NEXT collaboration is dedicated to the study of double beta decays of Xe using a high-pressure gas electroluminescent time projection chamber. This advanced technology combines exceptional energy resolution ( FWHM at the value of the neutrinoless double beta decay) and powerful topological event discrimination. Building on the achievements of the NEXT-White detector, the NEXT-100 detector started taking data at the Laboratorio Subterráneo de Canfranc (LSC) in May of 2024. Designed to operate with xenon gas at 13.5 bar, NEXT-100 consists of a time projection chamber where the energy and the spatial pattern of the ionising particles in the detector are precisely retrieved using two sensor planes (one with photo-multiplier tubes and the other with silicon photo-multipliers). The detector has been operating at stable conditions using argon and xenon gases at 4 bar and drift fields of 74 V/cm and 118 V/cm, respectively. Alpha decays from the Rn chain have been used to test and monitor the stability of the detector, showing a constant electron lifetime in the drift volume. In this paper, in addition to reporting the results of the commissioning run, we provide a detailed description of the NEXT-100 detector, describe its assembly, and present the current estimation of the radiopurity budget.

Paper Structure

This paper contains 21 sections, 5 equations, 17 figures, 3 tables.

Table of Contents

  1. Introduction
  2. The detector vessel and shielding
  3. Time Projection Chamber
  4. Field Cage
  5. Cathode and Electroluminescence Meshes
  6. High Voltage Feed-throughs
  7. Energy Plane
  8. Tracking Plane
  9. Read-out and DAQ
  10. Read-out and DAQ Electronics
  11. DAQ Software
  12. DAQ Event Detection
  13. Gas System
  14. Emergency Recovery
  15. Improvement of the circulation flow
  16. ...and 6 more sections

Figures (17)

  • Figure 1: (a) Illustration of the NEXT-100 setup in Hall A of the LSC, showing the high-pressure time projection chamber, pressure vessel, internal components, and external shielding. (b) Operation principle of the high pressure xenon detectors of the NEXT program: a time projection chamber, using electroluminescence as amplification. (c) A picture of the pressure vessel and inner copper shell taken from the energy plane side during assembly. (d) Field cage after being assembled and inserted over the inner copper shell inside the pressure vessel, picture taken from the energy plane side. (e) Field cage after inserting the PTFE panels that create the light tube, picture taken from the tracking plane side.
  • Figure 2: (a) Pressure vessel after polishing and prior to installation at the LSC. Inner Copper Shielding of (b) the Energy Plane and (c) the Tracking Plane. These pictures were taken after their machining and during the cleaning process, prior to installation in the NEXT-100 detector.
  • Figure 3: (a) Drawing of the field cage without the outside insulator panel. The copper rings (red-brown) are inserted into the struts, the cable (pink) wraps around from the field cage connecting to the cathode (white), and the reflector panels (yellow) are slid into place through the struts. (b) Field cage during assembly. Resistor chains are visible along the drift region and connected to the cathode ring (left). Stainless steel wheels were used to help during assembly and insertion, and removed once it was inserted.
  • Figure 4: Expected thickness of the TPB coating of the PTFE panels covering the interior side of the light tube. Two test evaporations were evaluated (blue and red markers), showing an agreement at different radial distances within the evaporator (shown by the general trend in black). Values show a homogeneous coating between 34 of TPB, ensuring a maximal efficiency for light emission TPBStudies. Thickness was estimated by positioning test slides where the panels would be placed and, after a regular evaporation, measuring the deposition over said slides with a stylus profilometer. Errors reflect the actual size of the slides (for the radial distance) and the variation of the coating along each slide (for the thickness).
  • Figure 5: Measurement of the electrostatic deflection as a function of applied voltage shown for one of the EL meshes. Measurements are fit to a deflection model and the extracted mesh tensions are 990$\pm$45 N and 835$\pm$40 N N100Mesh.
  • ...and 12 more figures