Monitoring antiproton numbers with a CMOS detector in a dense-track environment

@misc{regenfus2026monitoring,
  title = {{Monitoring antiproton numbers with a CMOS detector in a dense-track environment}},
  author = {C Regenfus and P Adrich and I Belosevic and F Benkel and M Chung and P Cladé and P Comini and P Crivelli and P Debu and A Douillet and S Geffroy and S Guellati-Khelifa and P Guichard and P.-A Hervieux and L Hilico and P Indelicato and S Jonsell and J.-P Karr and B Kim and S Kim and E.-S Kim and N Kuroda and B Lee and L Liszkay and D Lunney and G Manfredi and B Mansoulié and V Martimort and M Matusiak and V Nesvizhevsky and F Nez and K Park and N Paul and E Perez and P Pérez and C Roumegou and J.-Y Roussé and F Schmidt-Kaler and K Szymczyk and T.A Tanaka and B Tuchming and D.-P van der Werf and D Won and S Wronka and P Yzombard},
  howpublished = {HAL},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.04078},
  eprint = {2609.04078},
  archivePrefix = {arXiv},
  url = {https://hal.science/hal-05759150v1},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - Monitoring antiproton numbers with a CMOS detector in a dense-track environment
AU  - C Regenfus
AU  - P Adrich
AU  - I Belosevic
AU  - F Benkel
AU  - M Chung
AU  - P Cladé
AU  - P Comini
AU  - P Crivelli
AU  - P Debu
AU  - A Douillet
AU  - S Geffroy
AU  - S Guellati-Khelifa
AU  - P Guichard
AU  - P.-A Hervieux
AU  - L Hilico
AU  - P Indelicato
AU  - S Jonsell
AU  - J.-P Karr
AU  - B Kim
AU  - S Kim
AU  - E.-S Kim
AU  - N Kuroda
AU  - B Lee
AU  - L Liszkay
AU  - D Lunney
AU  - G Manfredi
AU  - B Mansoulié
AU  - V Martimort
AU  - M Matusiak
AU  - V Nesvizhevsky
AU  - F Nez
AU  - K Park
AU  - N Paul
AU  - E Perez
AU  - P Pérez
AU  - C Roumegou
AU  - J.-Y Roussé
AU  - F Schmidt-Kaler
AU  - K Szymczyk
AU  - T.A Tanaka
AU  - B Tuchming
AU  - D.-P van der Werf
AU  - D Won
AU  - S Wronka
AU  - P Yzombard
PY  - 2026
DA  - 2026/09/03
PB  - HAL
DO  - 10.48550/arxiv.2609.04078
UR  - https://hal.science/hal-05759150v1
AB  - The production of antihydrogen by the GBAR experiment at AD/ELENA requires good knowledge of the number of incident keV antiprotons, which can be problematic. We have used a commercial CMOS digital camera mounted around the experimental vacuum chamber to determine antiproton numbers from ionising particles created in the annihilation process on the surface of microchannel plate detectors which are used for beam imaging. We show that the multiplicity of emerging charged particles is as expected for individual annihilations of antiprotons with nucleons at rest, taking into account the surrounding material budget. Most of those particles are in the minimal ionising regime, but can be detected with nearly 100% efficiency in the CMOS pixel detector, while due to the thin depletion layer the device is insensitive to background gammas. Thanks to the high granularity and small pixel size millions of antiproton annihilations can be reconstructed in a dense tracking environment over a large dynamic range with good resolution. From cluster length studies of non perpendicular tracks the thickness of the depletion zone and effective detection area was estimated. The cluster length also allows for a monitoring of track angles. Antiproton numbers are determined from the number of reconstructed clusters in the CMOS sensor by means of the covered solid angle relative to a calibration measurements with well known beam intensities at the most upstream location of the GBAR apparatus. Material effects on the emerging annihilation products were estimated by Monte Carlo (Geant4) calculations, while annihilation artefacts on the complex surface of a microchannel plate are cancelled out in this approach. This method minimises largely systematic uncertainties, leading to a final error of roughly 10% for the reconstruction of absolute antiproton numbers.
ER  -