Light Output and Radiation Damage in A Lead Tungstate Crystal
- PDF / 386,396 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 57 Downloads / 190 Views
ABSTRACT The optical absorption, light output and effects of radiation damage have been studied in a 2.2 x 2.2 x 12.8 cm 3 crystal of lead tungstate. The crystal exhibits a longitudinal attenuation length which varies from roughly 13 cm to 1.5 m over the region where the scintillation emission occurs (400-800 nm). The light yield produces approximately 10 photoelectrons per MeV on a photomultiplier tube with a bialkali photocathode. The scintillation and light transmission properties of the crystal were characterized before and after exposure to 1 Mrad of "°Co gamma rays. Significant radiation induced optical absorption was observed in this crystal, along with a considerable amount of phosphorescence after irradiation. Partial spontaneous recovery from the damage occurred at room temperature, and it was possible to induce additional recovery by optical bleaching. INTRODUCTION Lead tungstate (PbW0 4 ) is a relatively new crystal scintillator [1-4] which has a number of properties that make it an attractive candidate for use in electromagnetic calorimetry for high energy and nuclear physics. It has a high density (p=8.3 gm/cm 3), short radiation length (Xo = 0.9 cm), small Moliere radius (RM = 2.2 cm), and weak scintillation emission in the visible wavelength range. However, for may high energy physics applications, such as at the CERN LHC, calorimeters are required to operate in a high radiation environment, and therefore the radiation damage properties of the calorimeter materials are important. This paper reports on the results of an investigation of the optical absorption, light output and radiation damage in a PbW0 4 crystal of the type which could be used in a high energy physics calorimeter. The lead tungstate sample used in this study was produced at the Institute of Nuclear Problems in Minsk, Belarus. The sample is rectangular shaped, with dimensions 2.2 x 2.2 x 12.8 cm 3 . To the eye, the sample is transparent with a yellowish tint. All of the surfaces are well polished. Two principle characteristics of the crystal were measured: the optical absorbance and the scintillation light output. The crystal was exposed to a high intensity ' 0 Co radiation source in order to study the effects of radiation damage. The absorbance and scintillation light output were measured initially, and then after incremental radiation doses, up to a cumulative total dose of 1 Mrad. Following the last irradiation, the natural recovery of the crystal was measured as a function of time at room temperature after irradiation, and optical bleaching was used to try to induce additional recovery from damage. 475 Mat. Res. Soc. Symp. Proc. Vol. 348. 01994 Materials Research Society
2.0
0.5
S
E
T61
.. .. ...............
0 .3V
T2
T 6l
o
®T
- 0.2 -i o
0.5
CL U)
:1Tl
'C-
o0 .1 .. .
..
. .. .. . L
ci
0 .0
1 - -
400
500
T2
...
.
0.0 1
-A
600
. . .
700
1
800
wavelength (nm)
1
1I
400
500
600
700
800
wavelength (nm.)
Figure 1. a) Longitudinal absorption coefficient (L) and transverse absorption coefficien
Data Loading...
