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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

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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

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  • 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

Motivation

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Survey

  • 54 papers from 1970 to 2017
  • 50+ different materials
  • Organic and inorganic

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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

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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)

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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 Si-

rubber

  • To be operated over a large temperature range from -10 to 30 °C

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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 207Bi used to calibrate plastic

scintillator bar

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PSD at DAMPE

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Wang et al. 2017

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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

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PSD at DAMPE

  • Variation of signal amplitude due to temperature mainly from PMT

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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 (137Cs)

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LAB- and Mesitylene-based LS

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Dong-Mei et al. 2014

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LAB- and Mesitylene-based LS

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Dong-Mei et al. 2014

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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

  • bserved, 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.”

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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

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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
  • f light with temperature for both

PSDs

  • Temperature dependence of light

transmitted through optical coupling between scintillator and optical fiber

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Wooton & Beddar 2013

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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.

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Homma, Murase & Ishii 1985

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Toluene

  • Decreasing temperature:
  • Differential pulse-height

distributions from alpha- and beta-particles shift to higher pulse-height with decreasing temperature

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Homma, Murase & Ishii 1985

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Inorganic Scintillators

  • NaI(Tl)
  • CdWO4
  • Li2MoO4

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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

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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
  • f optical appearance

and light output of coating

compromises reusability

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Coron et al.2014

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CdWO4

  • Low-temperature value of light yield of some modern scintillators

(CaWO4, CdWO4, Bi4Ge3O12) close to theoretical limit [Mikhailik & Kraus 2010]

  • 116Cd attractive in scintillator detectors [Barabash et al. 2016]
  • One of the highest energy release (Q2β = 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)

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CdWO4

  • First successful test of cadmium tungstate crystal scintillator enriched

in 116Cd 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 CdWO4
  • Promising detector for next gen 0ν2β bolometric experiment eg. CUPID

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CdWO4

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Barabash et al. 2016

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Li2MoO4

  • “The luminescence of molybdates is almost completely quenched at

room temperature, therefore they have not been considered as conventional scintillating materials. However, cryogenic scintillators

  • perate 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]

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Li2MoO4

Spassky et al. 2015 26

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Conclusion

  • Better light yield
  • Better energy resolution
  • Shift in peak wavelengths and decay times

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Future Work

  • Study the behavior of the remaining scintillators at different

temperatures

  • Study the mechanisms that lead to temperature dependence

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Questions?

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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

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