1. No category

Applied Scintillation Technologies Products Range
AST has a history of developing scintillation detectors since the 1920’s. AST offer an extensive range of scintillating materials with a wide range of properties, notably emission spectra, that are tailored for a variety of applications. Detailed specifications for each of the products is shown in table 1. The applications of AST’s
scintillators range from medical imaging including dental, security, instrumentation, non-destructive testing and health physics.
Caesium Iodide Doped with Thallium (CsI(Tl))
GS20
Depositing CsI(Tl) onto a high quality fibre optic plate enables the design of compact and
high resolution imaging receptors (figure 2). CsI(Tl) can be integrated with CCD’s and
CMOS devices to undertake digital imaging in a cost effective manner. CsI(Tl) has a high xray attenuation coefficient, a high light output and high intrinsic efficiency. The columnar
structure of the CsI(Tl) reduces scatter and results in high resolution images.
AST’s glass scintillators are divided into 3 principal formulations, based on the percentage weight of
lithium content. Each type of glass is available in natural, 6Li enriched or 6Li depleted. In addition to
fibres, the glass can be supplied as cylinders, rods, discs or plates. Shapes can be provided to customer specification including drilling, polishing and coating with highly reflective paint. Large scintillators (>400g) can be produced as arrays of performance mapped pieces.
At AST CsI(Tl) can be coated onto fibre optic plates in different sizes up to 140mm in diameter. AST has the ability to customise solutions for application specific requirements. The
thickness of CsI(Tl) coatings is readily customisable between 50-500µm.
The most common varieties are GS20 and KG2 but GS20 and GS30 are commonly used in combination in handheld neutron/gamma discrimination instruments. GS20 is a lithium-6 enriched aluminosilicate glass doped with cerium (figure 4). GS20 is a rugged and compact scintillator which operates
efficiently in the temperature range of -250°C to 200°C unlike other scintillating materials. The
range of application of GS20 spans from neutron spectroscopy; neutron radiography, neutron porosity measurements to neutron detection in space and is a proven technology to replace 3He detectors.
CsI(Tl) has a range of application such as intra-oral dental imaging; medical imaging including mammography; non-destructive testing and industrial inspection; x-ray cameras;
and transmission electron microscopy and diffraction.
1.0
1.0
CsI(Tl)
GS20
0.8
Intensity (a.u)
Intensity (a.u)
0.8
0.6
0.4
0.6
0.4
0.2
0.2
0.0
0.0
400
500
600
700
400
Wavelength (nm)
500
600
700
Wavelength (nm)
Figure 2: An AST CsI(Tl) phosphor
and reflector coated onto an FOP.
Figure 1: Radioluminescence
spectrum of CsI(Tl).
Figure 3: Radioluminescence
spectrum of GS20.
Figure 4: GS20 illuminated under UV light.
Table 1: Specifications of CsI(Tl); GS20; ND screen; and Gadox
Peak Emission Wavelength (nm)
Colour
Decay Time
Radiation Detected
Light Yield (photon.MeV-1 of gamma radiation)
CsI(Tl)
540 [1] (figure 1)
Yellow-Green
680ns (64%) [1]
X-rays
65,000 [1]
GS20
395 [2] (figure 3)
Blue
50-70ns [2]
Neutrons
3,500 [1]
ND Screen
460 [3] (figure 5)
Blue
80µs [4]
Neutrons
160,000 [4]
Gadox Tb Screen
545 [3] (figure 7)
Yellow-Green
approx. 2ms (10%) [2]
X-ray
70,000 [5]
Neutron Detection (ND) Screens
Gadolinium Oxysulphide Doped with Terbium (Gadox)
The composition of ND screens is 6LiF/ZnS:Ag (figure 6). ND screens have a very high light
output and a low effective Z which is ideal for gamma discrimination. ND screens are
opaque to their own scintillation light restricting the maximum thickness of the screen to
0.5mm. AST ND screens can be produced up to 500mm X 500mm but screens of up to 1m
X 1m can be manufactured to special order.
The composition of radiographic screens for x-ray detection is terbium doped gadolinium oxysulphide (Gd2O2S:Tb3+) also known as P43 (figure 8). The screen has a high effective Z and has a high
quantum efficiency to convert x-ray energy into visible light. The Gadox screens are non-burn formulations which are rugged and cost effective scintillator option for radiographic screens.
ND screen are a high performance neutron detection screen often integrated into X-ray
based systems to allow the detection of high cross section elements such as carbon and
hydrogen found in plastic explosives. ND screens are also readily utilised for boarder security in mobile truck and container scanning systems. ND screens are used for position sensitive detector applications in ISIS at Rutherford Appleton Laboratories.
Standard sizes are 30cm X 40cm; 14cm X 17cm; and 17cm X 17cm. Custom sizes are available up
to 1m X 1.5m. Parameters such as resolution, sensitivity, speed and colour of response can be influenced in production for customised samples. The samples can be mounted on Bakelite; aluminium; or specialist plastics.
Screens are ideal for the non-destructive testing industry. The radiographic screens are commonly
used to check engines, pipelines, test equipment quality control, metal components, castings and
radioactive waste drums.
1.0
1.0
Gd2O2S:Tb
ND screen
0.8
Intensity (a.u)
Intensity (a.u)
0.8
3+
0.6
0.4
0.6
0.4
0.2
0.2
0.0
0.0
400
500
600
400
700
600
700
Wavelength (nm)
Wavelength (nm)
Figure 5: Radioluminescence spectrum of
the ND screen.
500
Figure 6: ND screen illuminated
under UV light.
Figure 7: Radioluminescence spectrum of
Gadox Tb screen.
Figure 8: SEM image of 10µm particulates of
a Gadox Tb screen.
References:
[1]
Knoll, G. F., 2010, Radiation Detection and Measurement, 4th Edition, John Wiley & Sons Inc, USA
[2]
Tyrrell, G. C., 2005, Phosphors and scintillators in radiation imaging detectors, Nuclear Instruments and Methods in Physics Research A, 546, 180-187
[3]
Shionoya, S. and Yen, W. M., 1999, Phosphor Handbook, CRC Press, USA
[4]
Anderson, I. S., McGreevy, R. L. and Bilheux, H. Z., 2009, Neutron Imaging and Applications, Springer Science, USA
[5]
Weber, M. J., 2002, Inorganic scintillators: today and tomorrow, Journal of Luminescence, 100, 35-45