Optimization of electrochemical-etching parameters for highly sensitive CR-39 fast neutron dosimeters Page: 4 of 15
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The Health Physics Research Reactor- (HPRR) at the Oak Ridge National
Laboratory was used to irradiate the plastic with fission spectrum neutrons.
The appropriate quality factor for converting dose from the unshielded HPRR to
dose equivalent is 9.4. In one neutron irradiation, a 1 mm thick polyethylene
cover was used as a proton radiator. This thickness is sufficient for optimal
sensitivity [Be79].
The apparatus for electrochemical etching has been described in a previous
publication [Th76]. The power supply and audio-oscillator had maximum voltage
and frequency outputs of 1 £00 V(rms) and 5 kHz, respectively.
Electrochemical etching was conducted with 9 N KOH at ambient temperature
(~25°C) for a period of 4 hours. Conventional etching, when used as a pre-
electrochemical etching step [A179], was in 9 N KOH at 60°C for 3 hours. These
values were chosen to be consistent with those used in previous studies [Ga80,
To81], and were kept invariant. The electrochemically etched tracks appeared
as spots and were counted in a Microcard reader at 16X magnification.
For making differential leakage current measurements, two identical
electrochemical etching cells were placed in parallel [Ga80]. Neutron-
irradiated (50 rad) CR-39 foils were placed in one cell, and undamaged, unirra-
diated foils in the other cell. Tap-water instead of KOH solution was used
while the differential conductance measurements were being made.
RESULTS
The purpose behind differential leakage current measurements is to aid in
locating the optimum voltage gradient and frequency [Ga80]. As the voltage
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Gammage, R.B. & Chowdhury, A. Optimization of electrochemical-etching parameters for highly sensitive CR-39 fast neutron dosimeters, article, January 1, 1981; Tennessee. (https://digital.library.unt.edu/ark:/67531/metadc1063569/m1/4/?rotate=90: accessed March 28, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.