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Cosmic Ray Measurements Using Charge and Light Readout in a Pixelated Liquid Argon Time Projection Chamber

SoLAr Collaboration, N. Anfimov, A. Branca, J. Bürgi, L. Calivers, P. Carniti, E. Calvo, E. Cristaldo, C. Cuesta, F. Declich, R. Diurba, P. Dunne, D. A. Dwyer, J. Evans, A. C. Ezeribe, A. Gauch, I. Gil-Botella, C. Gotti, S. Greenberg, D. Guffanti, A. Karcher, J. Kunzmann, N. Lane, S. Manthey Corchado, N. McConkey, A. Minotti, A. Navrer-Agasson, S. Parsa, G. Pessina, G. Ruiz Ferreira, B. Russell, S. Söldner-Rembold, A. M. Szelc, A. Tapper, F. Terranova, C. Tognina, D. Trotta, S. Tufanli, H. Vieira de Souza, G. Vitti Stenico, A. Verdugo, M. Weber, I. Xiotidis

TL;DR

This work tests SoLAr V2, a pixelated LArTPC with integrated charge and light readout, aiming to improve calorimetry and background rejection for solar-neutrino physics. The detector features a 32–33 cm plane with 1,200 active charge pixels and 64 SiPM light channels, operating in a ~30 cm drift at a modest field, and uses LArPix for charge readout alongside deconvolved SiPM signals for light. Calibrations and cosmic-ray muon data show coherent charge and light responses, enabling measurements of dQ/dx and dL/dx and yielding an electron lifetime of 1.87 ± 0.18 ms with a corresponding ~10% charge loss over 30 cm; the results demonstrate a viable path to combined calorimetry. Overall, the SoLAr V2 results validate dual-readout concepts and motivate next-generation prototyping toward kiloton-scale detectors with improved energy resolution and data-rate management.

Abstract

Liquid argon time projection chambers have emerged as a competitive technology for detecting solar neutrinos. The SoLAr collaboration was formed to explore argon detectors with pixelated light and charge readout, aiming for high detection efficiency and improved energy resolution. Building on the success of an initial prototype, we present results obtained with a second SoLAr prototype (V2), a $30 \times 30 \times 30$ cm$^{3}$ time projection chamber operated in a cryostat containing several hundred kilograms of liquid argon. We report measurements of cosmic-ray muons using both tracking and calorimetry from light and charge sensors, and we highlight the improved performance achieved through combined charge and light reconstruction. These results demonstrate the promise of dual-readout detectors and motivate future prototyping efforts toward kiloton-scale facilities.

Cosmic Ray Measurements Using Charge and Light Readout in a Pixelated Liquid Argon Time Projection Chamber

TL;DR

This work tests SoLAr V2, a pixelated LArTPC with integrated charge and light readout, aiming to improve calorimetry and background rejection for solar-neutrino physics. The detector features a 32–33 cm plane with 1,200 active charge pixels and 64 SiPM light channels, operating in a ~30 cm drift at a modest field, and uses LArPix for charge readout alongside deconvolved SiPM signals for light. Calibrations and cosmic-ray muon data show coherent charge and light responses, enabling measurements of dQ/dx and dL/dx and yielding an electron lifetime of 1.87 ± 0.18 ms with a corresponding ~10% charge loss over 30 cm; the results demonstrate a viable path to combined calorimetry. Overall, the SoLAr V2 results validate dual-readout concepts and motivate next-generation prototyping toward kiloton-scale detectors with improved energy resolution and data-rate management.

Abstract

Liquid argon time projection chambers have emerged as a competitive technology for detecting solar neutrinos. The SoLAr collaboration was formed to explore argon detectors with pixelated light and charge readout, aiming for high detection efficiency and improved energy resolution. Building on the success of an initial prototype, we present results obtained with a second SoLAr prototype (V2), a cm time projection chamber operated in a cryostat containing several hundred kilograms of liquid argon. We report measurements of cosmic-ray muons using both tracking and calorimetry from light and charge sensors, and we highlight the improved performance achieved through combined charge and light reconstruction. These results demonstrate the promise of dual-readout detectors and motivate future prototyping efforts toward kiloton-scale facilities.

Paper Structure

This paper contains 18 sections, 8 equations, 25 figures.

Table of Contents

  1. Introduction
  2. SoLAr V2 Detector
  3. Design of the Anode PCB
  4. Charge Readout
  5. Light Readout
  6. TPC Assembly and Integration
  7. DAQ and Operations
  8. Detector Calibration
  9. Charge readout system
  10. Light readout system
  11. Measurements of Cosmic-ray Muons
  12. Performance from the Light Readout System
  13. Reconstruction of cosmic muons with charge data
  14. Directionality and Track Length
  15. Charge Deposition per Unit Length and Electron Lifetime
  16. ...and 3 more sections

Figures (25)

  • Figure 1: SoLAr v2 prototype unit cell design. (a) Each unit cell consists of one SiPM (6 mm by 6 mm) and sixty charge collection pads (3 mm by 3 mm). (b) Detailed view of the PCB traces connecting each pixel to the LArPix chip, located on the back side of the PCB. (c) Stack-up of the layers of the PCB.
  • Figure 2: CAD drawing of the SoLAr V2 anode PCB.
  • Figure 3: (a) Charge feed-through, (b) FPC cable for charge power length: 1.2 m, width 1.5 cm, (c) FPC cable for charge data length: 1.2 m, width: 2.5 cm (d) The charge feed-through and cables.
  • Figure 4: (a) The cold preamplifier board; (b) light feed-through; (c) FPC cable for light data with a length of 18cm and a width of 1.6cm.
  • Figure 5: (a) Interior view of the TPC, illustrating the arrangement of the anode plane, cathode, and field cage; (b) the fully assembled and cabled TPC with the cold preamplifier PCB mounted and visible on the support structure; (c) SoLAr V2 TPC before insertion into the cryostat.
  • ...and 20 more figures