BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//CERN//INDICO//EN
BEGIN:VEVENT
SUMMARY:Determination of Ionization Yields for Recoil Nuclei in Argon
DTSTART;VALUE=DATE-TIME:20261030T154500Z
DTEND;VALUE=DATE-TIME:20261030T160000Z
DTSTAMP;VALUE=DATE-TIME:20261017T151059Z
UID:indico-contribution-6386@cern.ch
DESCRIPTION:Speakers: Mikhail Bakulev (MSU Physics Faculty)\nTwo-phase (li
 quid–gas) argon detectors exhibit good sensitivity to relatively low rec
 oil-nucleus energies (~ 1 keV) — which is precisely why they have found 
 widespread application in nuclear physics and astrophysics experiments. Sc
 aling up to active masses of tens of tonnes opens up another area for them
  — WIMP searches. Reconstruction of the recoil-nucleus energy from the d
 etector signal is impossible without knowledge of the ionization yield\, i
 .e. the ratio of the number of electrons emitted from the liquid into the 
 gas to the recoil-nucleus energy. Ionization yields are most conveniently 
 measured using neutrons that mimic WIMPs.\n\nWork on measuring argon ioniz
 ation yields with a two-phase detector is underway at the Budker Institute
  of Nuclear Physics. The recoil-nucleus energy of 120 keV obtained in earl
 ier measurements with a 2.45 MeV neutron beam from a D–D reaction-based 
 neutron generator [1] was relatively high\; moreover\, the accumulated sta
 tistics were insufficient to achieve the required accuracy. A solution was
  found in the use of the VITA accelerator-based neutron source at BINP SB 
 RAS\, employed for the development of boron neutron capture therapy (BNCT)
  techniques [2\, 3]: it made it possible both to increase the statistics a
 nd to move to lower recoil-nucleus energies. For two series of test measur
 ements\, a scintillation detector based on a stilbene single crystal and a
  photomultiplier tube was used instead of the two-phase detector. This mad
 e it possible to determine the detection thresholds of the neutron dtector
 s and the quenching factors of the stilbene crystals. Agreement with the e
 xperiment was also demonstrated by Monte Carlo simulations of the energy s
 pectra of scattered neutrons.\n\nThe next phase of the experiment is curre
 ntly being prepared: the light collection of the two-phase detector is to 
 be increased\, and the detector itself is to be placed in the bunker of th
 e VITA accelerator-based neutron source. The light collection is planned t
 o be improved by coating the entire surface of the detector with the wavel
 ength shifter tetraphenylbutadiene (TPB). A series of studies has already 
 been carried out\, in which the re-emission efficiency of TPB was measured
  and aging effects were investigated. The sensitivity to optical scintilla
 tion signals is expected to be enhanced by installing an additional photod
 etector array of silicon photomultipliers (SiPMs) ArrayC-60035-4P-BGA. For
  these SiPMs\, the gain\, the cross-talk probability\, and the dark noise 
 count rate at cryogenic temperature have been measured.\n\nReferences\n   
  1. A. E. Bondar et al.\, Siberian Physical Journal 12\, 3 (2017). \n    2
 . С. Ю. Таскаев. Ускорительный источник не
 йтронов VITA. М.: ФИЗМАТЛИТ\, 2024. 248 c. \n    3. S. Ta
 skaev et al. VITA accelerator neutron sources: status and research results
 . Preprint 202605.0884 (2026).\n\nhttps://indico.particle.mephi.ru/event/6
 26/contributions/6386/
LOCATION:Sevastopol Hotel
URL:https://indico.particle.mephi.ru/event/626/contributions/6386/
END:VEVENT
END:VCALENDAR