Thin scintillator CsI(Tl) films for precise tomography. Development and applications.

E. A. Kozyrev, K. E. Kuper, A. G. Lemzyakov, G. P. RazuvaevA. V. Petrozhitskiy, and A. S. Popov

Budker Institute of Nuclear PhysicsNovosibirsk State University

e.a.kozyrev@inp.nsk.su

Novosibirsk, June 26, 2018

Outline1. Introduction

2. Thin CsI:Tl scintillator films ➤ development➤ preparation ➤ performance➤ application

3. Summary

1. IntroductionThe following discussion will be related to CsI:Tl scintillator, however almost all topics can be applied for other materials too.● CsI(Tl) is one of the brightest scintillators (54 photons/keV)● The maximum of the broad emission is situated at 550 nm ● A relatively slow scintillator with an average decay time of about 1 μs for γ-rays● CsI(Tl) scintillation crystals can be used for particle discrimination using pulse shape

analysis● Microstructure inside volume decreases the lateral spreading of scintillating light.● Slightly hygroscopic

Relative light output as a function of temperature for CsI: Tl (Na) [1]

Measured emission spectra of the CsI(Tl) crystal with [Tl] of 10e-6, 10e-5,10e-4,10e-3, and 10e-2

mol under alpha particles excitations [2]

2. Thin CsI:Tl films: development CsI:Tl scintillation films were manufactured by the thermal deposition method. Substrates: glass (150 mkm), Carbon (200-1000 mkm) Mylar (DuPont, 2.9 mkm) saphir (800 mkm)Thickness of CsI:Tl films: 0.1-20 mkm

17 mm

Schematic of the thermal evaporation setting

680 ०C

200 - 400 ०C

P = 5×10-3 PaThe average velocity of deposition of CsI:Tl = 17 Å/sec.The scintillator volume is characterized by grain/columns structure.The grain structure depends on the type of used substrate, on its temperature and on the velocity of CsI:Tl deposition.

2. Thin CsI:Tl films: development

2. Thin CsI:Tl films: development

Fixing the substrate in the case without heating

2. Thin CsI:Tl films: development

Fixing the substrate in the case with heating

2. Thin CsI:Tl films: performance and properties

10 mkm 20 mkm

20 mkm20 mkm

Mylar substrate Glass substrate. V(evaporation)=17 Å/s.

Glass substrate. V(evaporation)=10 Å/s. Glass substrate. V(evaporation)=25 Å/s.

The cross section of CsI:Tl film with well separated grain structure

290

390350300

2. Thin CsI:Tl films: development , different substrates temperature

sintered/caked

2. Thin CsI:Tl films: performance

CollimatorCollimator Monochromator

Collimator

Scintillator

DetectorVisible light

Object SR

12 m

16.5 m

VEPP-3 X-ray source is used to study the properties of prepared CsI:Tl films as well as to perform 3D-tomography of different patterns

2. Thin CsI:Tl films: performance

Light output of CsI:Tl films for different substrates temperature.

LSF d/dx

FFT

2. Thin CsI:Tl films: preparationAdditional carbon layer was performed by magnetron deposition method. Required carbon thickness is about 250 nm. Light output decreases by 1.9-2.4 times.

The additional carbon layer removes the multiple scattering of visible photons inside scintillator.

substrateIncident X-ray

CCsI:Tl

Photodetector

geophysics crystallography solid state physics

biology archeology

2. Thin CsI:Tl films: application - X-ray imaging, 3D tomography

180 projections 720 projections 7200 projections

The profile of reconstructed tomography of sand with water in a plastic cell

2. Thin CsI:Tl films: application - X-ray imaging, 3D tomography

visualization of methane hydrate bearing sediments with micro-CT

0.5 mm

Methane hydrate has great potential as an energy resource. It is critical to know how hydrate is distributed in sediment pores and how it interacts with sediments in order to understand the potentially dynamic physicaland chemical properties of hydrate-bearing sediments.

2. Thin CsI:Tl films: application - beams diagnostics

The transverse beams profile tests was performed in PSI and J-PARC.

2. Thin CsI:Tl films: application - beams diagnostics

CsI:Tl film deposited on Mylar substrate

Muon deposits 20+/-1 keV

The beams profile was measured and compared with other methodics

The results of the Geant 4 calculation of transverse momentum spectra of muons after the penetration of the films

Y, mm

thick \ E 30 MeV 300 MeV

3 mkm 0.019 5.9e-04

5 mkm 0.025 7.2e-04

σ(px/p)

2. Thin CsI:Tl films: applicationThe thin scintillator films can be used for density measurements of plasma which could be exposed to soft X-ray radiation.

The experiments are ongoing in Budker Institute.PHYSICAL REVIEW A 66, 062506 (2002͒):Polarizability (α) is a measure of the charge redistribution of an atom or molecule when an external electrical field is applied. Polarizabilities are important for the determining the values of several physical properties of materials such as the refractive index, the dielectric constant, ion-atom charge-exchange cross sections...

η = 1 + 2πnα α = 11.4+/-1.2 Å^3

Radiogram of exploded 25-mkm Ag wire

Interferogram

Summary➤ The methodics of performance of thin CsI:Tl films was developed.

➤ The relationship between the morphology of deposited layers and the characterization of the film was presented.

➤ The post-deposition treatment by carbon leads to significant improvement of spatial resolution.

➤ X-ray radiographic methods with thin scintillator films can be employed with the films in polychromatic and monochromatic modes from 10 mkm of biological tissue up to 5 cm of dense rock for applied as well as purely fundamental research.

REFERENCES[1] https://www.crystals.saint-gobain.com/sites/imdf.crystals.com/files/documents/csitl-and-na-material-data-sheet_69771.pdf

[2] IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 48, NO. 4, AUGUST 2001 https://www.ipen.br/biblioteca/2001/08243.pdf

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