77 research outputs found
Optimization of light collection from crystal scintillators for cryogenic experiments
High light collection efficiency is an important requirement in any
application of scintillation detectors. The purpose of this study is to
investigate the possibility for improving this parameter in cryogenic
scintillation bolometers, which can be considered as a promising detectors in
experiments investigating neutrinoless double beta decay and dark matter.
Energy resolutions and relative pulse amplitudes of scintillation detectors
using ZnWO4 scintillation crystals of different shapes (cylinder 20 mm in
dimater by 20 mm and hexagonal prism with diagonal 20 mm and height 20 mm),
reflector materials and shapes, optical contact and surface properties
(polished and diffused) were measured at room temperature. Propagation of
optical photons in these experimental conditions was simulated using Geant4 and
ZEMAX codes. The results of the simulations are found to be in good agreement
with each other and with direct measurements of the crystals. This could be
applied to optimize the geometry of scintillation detectors used in the
cryogenic experiments.Comment: 12 pages, 8 figures, 1 Tabl
Impact of geometry on light collection efficiency of scintillation detectors for cryogenic rare event searches
Simulations of photon propagation in scintillation detectors were performed
with the aim to find the optimal scintillator geometry, surface treatment, and
shape of external reflector in order to achieve maximum light collection
efficiency for detector configurations that avoid direct optical coupling, a
situation that is commonly found in cryogenic scintillating bolometers in
experimental searches for double beta decay and dark matter. To evaluate the
light collection efficiency of various geometrical configurations we used the
ZEMAX ray-tracing software. It was found that scintillators in the shape of a
triangular prism with an external mirror shaped as truncated cone gives the
highest light collection efficiency. The results of the simulations were
confirmed by carrying out measurements of the light collection efficiencies of
CaWO4 crystal scintillators. A comparison of simulated and measured values of
light output shows good agreemen
New limits on , and decay of Ce and Ce with deeply purified cerium sample
A search for double electron capture (), electron capture with
positron emission (), and double positron emission
) in Ce and Ce was realized with a 465 cm
ultra-low background HP Ge spectrometer over 2299 h at the Gran Sasso
underground laboratory. A 627 g sample of cerium oxide deeply purified by
liquid-liquid extraction method was used as a source of quanta
expected in double decay of the cerium isotopes. New improved half-life
limits were set on different modes and channels of double decay of
Ce and Ce at the level of yr.Comment: 19 pages, 6 figures, 2 table
Improvement of radiopurity level of enriched CdWO and ZnWO crystal scintillators by recrystallization
As low as possible radioactive contamination of a detector plays a crucial
role to improve sensitivity of a double beta decay experiment. The radioactive
contamination of a sample of CdWO crystal scintillator by thorium
was reduced by a factor , down to the level 0.01 mBq/kg
(Th), by exploiting the recrystallization procedure. The total alpha
activity of uranium and thorium daughters was reduced by a factor ,
down to 1.6 mBq/kg. No change in the specific activity (the total
activity and Th) was observed in a sample of ZnWO crystal produced
by recrystallization after removing mm surface layer of the
crystal.Comment: 14 pages, 5 figures and 2 table
Personalized prediction of the results of reconstructive surgery for chronic otitis media
Introduction. The goal of the surgical treatment of patients with chronic otitis media is to eliminate the consequences of the inflammatory and destructive disease while preserving the anatomy of the middle ear and improving auditory function. According to the literature, the outcome of middle ear reconstructive surgery for the surgeon and the patient in most cases remains unpredictable. The development of an integrated approach to predicting the results of reconstructive sanitizing surgery will make it possible to select the most effective surgical tactics in terms of treatment time and type of surgical intervention.Aim. To develop a methodology for personalized prediction of the result of operations on the temporal bone in patients with chronic otitis media and substantiate the choice of optimal surgical tactics, taking into account clinical and functional parameters.Materials and methods. A retrospective study was carried out to compare the data of patients with the use of the author’s personalized prognosis method: “A method for predicting the result of tympanoplasty” and “A method for predicting the degree of hearing loss in otosurgery for chronic otitis media” with the results of surgical treatment of 263 patients with chronic otitis media, operated on in hospitals in Moscow. Chelyabinsk in 2018–2020.Results and discussion. In the observation, the patients were divided into two groups according to the sum of points, which determined the volume, type and timing of the operation. The sum of points less than or equal to 20 was assessed as a favorable prognosis for reconstructive debridement surgery. The sum of points in the range from 21–40 was assessed as the possibility of carrying out onestage surgery for the purpose of sanitation and reconstruction, but the patient should be informed about the unfavorable prognosis for the restoration of hearing. A score greater than 40 is assessed as an unfavorable prognosis, with an indication for separate-stage surgery, indicating a socially significant hearing loss in the postoperative period in patients with chronic otitis media.Conclusion. A personalized approach to predicting the results of surgical treatment forms groups of patients with chronic suppurative otitis media and helps in choosing surgical tactics in terms of the type, volume and timing of one-stage or separatestage reconstructive surgery and the need for reoperation for a period of one year
Limits on Dark Matter Effective Field Theory Parameters with CRESST-II
CRESST is a direct dark matter search experiment, aiming for an observation
of nuclear recoils induced by the interaction of dark matter particles with
cryogenic scintillating calcium tungstate crystals. Instead of confining
ourselves to standard spin-independent and spin-dependent searches, we
re-analyze data from CRESST-II using a more general effective field theory
(EFT) framework. On many of the EFT coupling constants, improved exclusion
limits in the low-mass region (< 3-4 GeV) are presented.Comment: 7 pages, 9 figure
Search for double beta decay processes in 106Cd with the help of 106CdWO4 crystal scintillator
A search for the double beta processes in 106Cd was carried out at the Gran
Sasso National Laboratories of the INFN (Italy) with the help of a 106CdWO4
crystal scintillator (215 g) enriched in 106Cd up to 66%. After 6590 h of data
taking, new improved half-life limits on the double beta processes in 106Cd
were established at the level of 10^{19}-10^{21} yr; in particular,
T_{1/2}(2\nu \epsilon \beta^+) > 2.1 10^{20} yr, T_{1/2}(2\nu 2\beta^+) > 4.3
10^{20} yr, and T_{1/2}(0\nu 2\epsilon) > 1.0 10^{21} yr. The resonant
neutrinoless double electron captures to the 2718 keV, 2741 keV and 2748 keV
excited states of 106Pd are restricted to T_{1/2}(0\nu 2K) > 4.3 10^{20} yr,
T_{1/2}(0\nu KL1) > 9.5 10^{20} yr and T_{1/2}(0\nu KL3) > 4.3 10^{20} yr,
respectively (all limits at 90% C.L.). A possible resonant enhancement of the
0\nu 2\epsilon processes is estimated in the framework of the QRPA approach.
The radioactive contamination of the 106CdWO4 crystal scintillator is reported.Comment: Minor changes of half-life limits after improving the data analysis;
version accepted for publication on Phys. Rev.
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