203
TABLE 69.
Neutron energy
Total damage
(1)
(2)
MeV
Calc. area/
.
6.2
7.2
8.2
9.2
10.1
11.1
12.1
14.1
Fast Neutron Errect on Postposep TLD-700
l
|
|
33.5
|
98.6
114.5
|
139.7
|
185.4
228.4
211.9
199.1
244.0
(6)
|
|
(7).
| ove |
Precalib. area/ \Postcalib, area/
mg X Rad
87
42.5
38
64.4
AF
80.9
89.9
111.2
.38
45
46
84.7
(5)
(3)72)}
Obs.“areal
mg
59.4
(3)
Irreversible damage
mg ™ Rad
9.0
w.4
|
|
8.0
8.0
49
15.5
|
12.4
37
10.8
|
7.7
pears necessary to attribute the irreversible and re-
versible damage to the same mechanism, the differ-
ences in these factors being due only to the annealing
process, At the neutron energies present in this ex-
periment, 6 to 14 MeV,the deformation of the crystal
by collision processes appears to be the mechanism
for the damage.
CONCLUSIONS
The effect of fast neutrons on the gamma ray re-
10.5
10.7
11.3
10.0
|
|
(8)
a)
|
|
|
7.1
7.8
7.1
8.3
Reversible
0.89
0.64
0.78
0.62
0.73
0.52
0.78
0.69
|
:
0.73
0.63
0.84
0.48
0.68
0.54
0.71
0.54
should not be used in the presence of fast neutrons to
monitor gamma radiation.
Wewish to thank Prof. Herman Cember, Civil Engineering Department, Northwestern University, for
his encouragement and cooperation.
One of us (K.E.) carried out this work under a
fellowship from the U.S. Public Health Services.
REFERENCES
sponse of 7LiF has been investigated. The dosimeters
1. Kastner, J., Oltman, B. G., Tedeschi, P., and Beggs, J. N
Health Phis, 13, 918 (1967).
2, Kastner, J., Ramesh, Hukkoo, Oltman B.G., and Dayal, Y.
is reversible with the annealing procedure employed.
The results from this experiment indicate that "LiF
3. Lauritsen T., and Ajsenberg-Selove, F. Energy Levels of
Light Nuclei. To be published.
J’
were found to suffer a marked damage, part of which
Radiat. Res. 82, 625 (1967).
. ULTRASONIC EXCITATION OF THERMOLUMINESCENTLITHIUM FLUORIDE*
Jacob Kastner, R. H. Selner, C. M. Paden, and B. G. Oltman
Ultrasonic excitation of luminescence has been proposed to eliminate the black-body radiation background noise inevitably associated with thermoluminescent dosimeter readout.
Studies have been carried out with single LiF crys-
tals bonded directly to piezoelectric transducers. The
transducers were driven with a continuous radiofrequency generator over a range of frequencies from 4
to 10 megacycles/sec (MHz}.
* Abstract of paper published in Health Phys. 16, 803 (1969).
Glow peaks were observed at 10 MHz. After observing a rise in the transducer-LiF temperature, we
duplicated the temperature ramp with our normal
thermoluminescent readout apparatus. The recorded
glow peaks were identical with the luminescence pro-
duced by the ultrasonic excitation, verifying the latter’s essentially thermal character and thus eliminat-
ing the hope that ultrasonics might provide real
advantages as a readout technique.