Survey of the performance of scintillation materials at low temperatures Biswas Sharma University of Tennessee, Knoxville 4/5/2017 Particle Physics and Astro-Cosmology Seminar 1
Motivation Versatility Unprecedented energy resolution requirement a challenge [Dong-Mei et al. 2014] Eg. Jiangmen Underground Neutrino Observatory (JUNO) requires 3%/ E(MeV) Previous experiments reached (5-6)%/ E Event discrimination 2
Survey 54 papers from 1970 to 2017 50+ different materials Organic and inorganic 3
Organic Scintillators Light yield of liquid scintillator temperature dependent Thermal quenching effects Excited solvent molecules may undergo non-radiation transition when colliding with other molecules Normally light yield will increase at lower temperature Rise in viscosity of the solvent Reduction in collisions 4
Organic Scintillators Plastic Scintillator Detector (PSD) at DArk Matter Particle Explorer (DAMPE) (2017) Linear alkyl benzene (LAB)-based and mesitylene-based liquid scintillators (2014) BCF plastic scintillation detectors (PSDs) (2013) Toluene (1985) 5
PSD at DAMPE DArk Matter Particle Explorer (DAMPE): satellite borne, contains Plastic Scintillator Detector (PSD) subsystem [Wang et al. 2017] Each bar coupled to a PMT (Hamamatsu R4443) at each end by Sirubber To be operated over a large temperature range from -10 to 30 C 6
PSD at DAMPE Temp. dependence of PSD system mainly contributed by 3 parts: Plastic scintillator PMT Front End Electronics (FEE) LED used to calibrate PMT, β source 207 Bi used to calibrate plastic scintillator bar 7
PSD at DAMPE Wang et al. 2017 8
PSD at DAMPE Temperature coefficient C = S/P(T = 20 C) S is the slope of the MPV curve, P(T = 20 C) is the ADC channels of the MPV at a temperature of 20 C 9
PSD at DAMPE Variation of signal amplitude due to temperature mainly from PMT 10
LAB- and Mesitylene-based LS Linear alkyl benzene (LAB)-based and mesitylene-based liquid scintillators [Dong-Mei et al. 2014] Daya Bay undoped liquid scintillator Solvent: LAB Fluor: 3 g/l 2,5-diphenyloxazole (PPO) Wave-length shifter 15 mg/l p-bis-(o-methylstyryl)-benzene (bis-msb) Gadolinium-doped LS Same recipe as above but mixed with a Gd complex with 0.1% Gd in mass Comparison: LS with same solute fractions but another solvent, mesitylene Light yield measured via Compton scattering of gamma rays from a radioactive source ( 137 Cs) 11
LAB- and Mesitylene-based LS Dong-Mei et al. 2014 12
LAB- and Mesitylene-based LS Dong-Mei et al. 2014 13
LAB- and Mesitylene-based LS Relative light yield of LS determined by comparing peak values measured by ADC at different temperatures Temperature lowered from 26 to -40 C (correcting for temp. response of PMT) Light yield increases by 23% for both LSs As no apparent degradation on the liquid scintillator transparency was observed, lowering the operation temperature of the detector to 4 C will increase the photoelectron yield of the detector by 13%, combining the light yield increase of the liquid scintillator and the quantum efficiency increase of the photomultiplier tubes. 14
BCF PSDs BCF plastic scintillation detectors (PSDs) [Wooton & Beddar 2013] BCF-60 or BCF-12 scintillating fiber coupled to optical fiber with cyanoacrylate Two most common scintillating fibers used in PSDs Temperature independence previously accepted as fact 15
BCF PSDs Change in measured radiation dose per C increase relative to dose measured at 22 C (2 pairs): BCF-60: 0.50% decrease BCF-12: 0.09% decrease Slight change in spectral distribution of light with temperature for both PSDs Temperature dependence of light transmitted through optical coupling between scintillator and optical fiber Wooton & Beddar 2013 16
Toluene Pure toluene (methylbenzene) [Homma, Murase & Ishii 1985] Decreasing temperature: Fluorescence maxima shift to longer wavelengths Red shift suggests that the fluorescence emission from excimer of toluene is promoted at lower temperatures Fluorescence intensity from pure toluene and PPO solution in toluene increases with decreasing temp. Homma, Murase & Ishii 1985 17
Toluene Decreasing temperature: Differential pulse-height distributions from alpha- and beta-particles shift to higher pulse-height with decreasing temperature Homma, Murase & Ishii 1985 18
Inorganic Scintillators NaI(Tl) CdWO 4 Li 2 MoO 4 19
NaI(Tl) Parylene-coated NaI(Tl) [Coron et al. 2014] NaI widely used as scintillator at room temp. Hygroscopicity limits use as cryogenic detector Parylene: humidity barrier, 2-5 µm layer 20
NaI(Tl) Luminescence spectra under X-ray excitation at several temp. Light output vs temp. at 1.5 300 K Thermoluminescence peaks observed around 60, 95, 150 K ~100 mk: degradation of optical appearance and light output of coating compromises reusability Coron et al.2014 21
CdWO 4 Low-temperature value of light yield of some modern scintillators (CaWO 4, CdWO 4, Bi 4 Ge 3 O 12 ) close to theoretical limit [Mikhailik & Kraus 2010] 116 Cd attractive in scintillator detectors [Barabash et al. 2016] One of the highest energy release (Q 2β = 2813.50(13) kev ) Comparatively large natural isotopic abundance (δ = 7.512(54)%) Applicability of centrifugation for cadmium isotopes enrichment in a large amount Availability of cadmium tungstate crystal scintillators (CdWO4) 22
CdWO 4 First successful test of cadmium tungstate crystal scintillator enriched in 116 Cd as a scintillating bolometer [Barabash et al. 2016] T=18mK, m=34.5g, Enrichment level: ~82%, time: ~250h High energy resolution(fwhm 2 7 kev for 0.2 2.6 MeV γ quanta) Powerful particle identification capability Light yield twice compared to non-enriched CdWO 4 Promising detector for next gen 0ν2β bolometric experiment eg. CUPID 23
CdWO 4 Barabash et al. 2016 24
Li 2 MoO 4 The luminescence of molybdates is almost completely quenched at room temperature, therefore they have not been considered as conventional scintillating materials. However, cryogenic scintillators operate at temperatures of several tens of milikelvin, which excludes the thermal quenching factor, and the systems earlier neglected because of low light yield at room temperature might be considered for application. [Spassky et al. 2015] 25
Li 2 MoO 4 Spassky et al. 2015 26
Conclusion Better light yield Better energy resolution Shift in peak wavelengths and decay times 27
Future Work Study the behavior of the remaining scintillators at different temperatures Study the mechanisms that lead to temperature dependence 28
Questions? 29
References Dong-Mei et al., Chin. Phys. C, 2014, 38 (11): 116001 Wang et al., Chin. Phys. C, 2017, 41(1): 016001 Wooton & Beddar, Physics in Medicine and Biology, 2013, 58(9) Homma et al., Journal of Radioanalytical and Nuclear Chemistry Letters, 1985, 95(5), 281-290 Coron et al., Eur. Phys. J. Web of Conf., 2014, 65: 02001 Mikhailik & Kraus, Phys. Status Solidi B, 2010, 247: 1583 1599 Barabash et al., Eur. Phys. J. C, 2016, 76:487 Spassky et al., Journal of Luminescence, 2015, 166 30