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Li doped
glass scintillators
  • Natural
  • enriched Li-6 doped ( 95%  6Li )
  • Li-6 depleted ( 99.99%  7Li doped )
se enlarged photo
Lithium doped glass scintillators
physical properties
  General Description:
Applied Scintillation Technologies manufactures a variety of Cerium activated Lithium Glass Scintillators.   These have been used for a variety of radiation detection applications since their developed in the 1950s.
 
Applications:
Typical applications include:
  • thermal neutron detection
  • neutron radiography
  • oil well logging
  • alpha, beta and gamma detection in environments
 
Glass types:
The glass scintillators are divided into 3 principal types, based on the lithium content (table 1).
Each of these is available in natural, 6Li enriched or 6Li depleted forms.
 
Glass forms:
In addition to fibers, the glass can be supplied as cylinders, rods, discs or plates.  
Shapes can be provided to customer specification including drilling and polishing and coating with highly reflective paint.   Large scintillators ( > 400g ) can be produced as arrays of matched pieces.
Glass can also be supplied in powder form with avarage particle size in the range 20µm to 1,000µm.

 
Physical properties:
Physical properties of the different glass types are shown in table 3.
 
Performance characteristics:
For detailed performance characteristics, refer other data sheets and cited papers.


    table 1        Types of Glass Scintillators    
Lithium Oxide
weight (%)
Natural 6Li enriched
(95% 6Li)
6Li depleted
(99.99% 7Li)
6 GS1 GS2 GS3
6 GSF1 GSF2 GSF3
18 GS10 GS20 GS30
21 KG1 KG2 KG3


table 2        Physical properties of Lithium scintillation glass    
  GS1 / 2 / 3 GS10 / 20 / 30 KG1 / 2 / 3 GSF1
Density ( g / ml ) 2.66 2.50 2.42 2.42
Reflactive index: n 1.06 1.55 1.57 1.58
Glass Transition: Tg ( °C ) 620 499 464 610
Softening point: Ts ( °C ) 650 522 490  
Strain point: Tsr ( °C ) 350 410 461 386
Coefficient of Linear expansion 7.0 x 10 -6 9.23 x 10 -6 100 x 10 -6  
max emission wavelength ( nm ) 395 395 395 395
Relative light pulse height per unit 100 [ 1 ] [ 2 ] 85 [ 2 ] 60 [ 2 ] 80
Relative light output to Anthracene 22% ~ 34% 20% ~ 30% 20%  
Decay time ( nSec ) 50 ~ 70 50 ~ 70 50 ~ 70 50 ~ 70
Resolution on the thermal neutron
peak obtained with moderated Po/Be
neutrons [ 3 ]
13% ~ 22%
( GS2 )
13% ~ 22%
( GS2 )
20% ~ 30%
( KG2 )
 
Peak / through ratio of above peak
( range ) for thermal neutrons
15:1 ~ 40:1
( GS2 )
  10:1 ~ 20:1
( KG2 )
 
 [1] pulse height of GS1 is 15% to NaI(Tl)
 [2] determined by thickness   /   light output raises by decreasing thickness down to ~ 2mm
 [2] thermal neutron resolution depends on system geometry

References:
L. A. Wraight Nucl. Inst. & Meth. 33, 181 - 193 (1965)
A. Spowart Nucl. Inst. & Meth. 75, 35 -42 (1969)
M. S. Coates AERE-PR/NP11 33, 181 - 193 (1967)
J. Cameron Nucl. Inst. & Meth. 56, 45 - 54 (1967)
H. Zetterstrom Nucl. Inst. & Meth. 42, 277 - 282 (1966)
E. Fort Nucl. Inst. & Meth. 85, 115 - 123 (1970)
A. Spowart Nucl. Inst. & Meth. 82, 1 - 6 (1965)
A. Spowart Nucl. Inst. & Meth. 140, 19 - 28 (1965)

Lithium Glass Scintillators neutron detection General:
Applied Scintillation Technologies manufactures a variety of Cerium activated
Lithium glass scintillators.   These have been used for a variety of radiation
detection applications since their development in the late 1950s.


The glass scintillators are extremely robust being resistant to all organic and
inorganic chemicals except hydrofluoric acid and strong alkalis and can be used
in temperatures ranging from -200°C to 250°C.   This allows them to be used in
conditions which prohibit the use of other scintillation materials.

Neutron detection:
The 3 types of glass available are natural lithium base, 6Li enriched and
6Li depleted.   The properties of the 3 types are similar except for neutron
detection where the 6Li enriched glasses are better.

The detection mechanism is,

 n + 6Li  >  Triton + alpha +   ~ 4.8MeV

Details of excitation are emission are shown in following graph.

  Graph showing excitation and emission spetrum of Ce3+ in Li glass
  emission spectrum of glass scintillator

table 3        neutron detection capabilities    
neutron energy   glass type   glass thickness  
0.01 ~ 20eV all types 0.1 ~ 10mm
thermal GS20 1.3mm
10eV ~ 100keV GS20 3.2mm
100eV ~ 1MeV GS20 25.4mm
1keV ~ 600keV KG2, GS20 9.5mm
1MeV ~ 6MeV GS20 25mm

Selectivity
Using pairs of  6Li and 7Li glasses, the gamma background detected can be subtracted.
The GS20 glass is particulary selective in its detection of thermal neutrons as shown by following graph.   This shows the pulse height spectrum for GS20 glass with an example background from 60Co.
Table 4 also shows an additional information on neutron selectivity overgamma response.
Gamma sensitivity of glass scintillator


table 4        Gamma sensitivities    
  scintillator type
  and thickness
Gamma photons to give the same light output as 1 neutron measured Gamma **
attenuation coefficient
226Ra 137Cs 60Co 226Ra 137Cs 60Co
   GS20; 1mm t 850 240 100 3.06 3.16 1.63
   GS20; 1.5mm t 550 160 74 8.14 7.89 2.17
   GS20; 3mm t 390 100 50 17.5 23.16 5.43
   KG2L; 6.2mm t 310 81 57 37.8 33.69 25.
 ** note:
   Gamma attenuation coefficients are underestimated due to detection of degraded Compton
   photons.   The error will be greatest for 1mm thick glass and smaller for thicker samples.

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Applied Scintillation Technologies Applied Scintillation Technologies
 8 Roydonbury Industrial Estate,
 Harlow CM19 5BZ,    United Kingdom
 Phone# +44 (0)1279 641 234    Fax# +44 (0)1279 413 679
Local distributor in Japan  
APACE Science
APACE Science, Inc.
 247 - 2, Hayashi 1-Chome, Tokorozawa, Saitama   359-1167
 Phone# +81-(0)4-2947-4424    Fax# +81-(0)4-2938-6002
  
G-tech, Corp.
 247 - 2, Hayashi 1-Chome, Tokorozawa, Saitama   359-1167
 Phone# +81-(0)4-2938-6001    Fax# +81-(0)4-2938-6002


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