Gopacitonce (107? torads) 
© Reactor up 
X Reactor down 
i} 2 3 4 
Integrated Thermol— Neutron Flux (10% n/em?) 
FIG. 5. Radiation effect on capacitances of type 
Top chart shows 
CP53B2EF504K fixed paper capacitors. 
averages for three Sprague, three Cornell-Dubilier. 
shows average for two Aerovox; bottom for one Aerovox. 
Thermal flux was 6.35 X 10!! 
little change. The results of several 
experiments are shown in Figs. 4-6. 
Some ceramic capacitors showed 
sporadic capacitance charges attributed 
to reactor-temperature changes in the 
interval from 20-50° C. Other capaci- 
tors have much smaller temperature 
coefficients and are only slightly affected 
by the same temperature changes. 
Measurement of small capacitances 
in a reactor is made difficult by the 
capacitance contributed by the con- 
necting cables, which changes through- 
out the irradiation, and by increased 
dissipation factors, which make im- 
pedance measurements more difficult. 
Semiconductors 
Because of both the growing applica- 
tion of transistors and their great sus- 
ceptibility to radiation damage, they 
have been studied as thoroughly as any 
type of component. The low damage 
threshold also has meant that weaker 
sources (thus more potential investiga- 
tions) could be used in the study. 
The effect of solar radiation on p—n 
junctions has been reported (10, 11), 
and gamma radiation is expected to 
behave in a like manner. In addition 
the regular structure of the crystals 
will be disturbed by collisions, and 
donors and acceptors will be created 
by neutron capture and subsequent 
beta decay. 
The effect of nuclear radiation on the 
forward and backward current of semi- 
conductor rectifiers, as indicated to 
date by this program is indicated in 
Fig. 7 and the table. The 1N58 ger- 
94 
s 
é 
§ 
5 - Xo 
= © Reactor up 2 i 
2 0.20 x Reoctor down fo} Soe 
iste} 
° 
° 
One : 
0.10 
25 (Cornel! —Dubilier) 
Oo, 
gk 
! ce) 
5 0 5 
tion. 
Center 
CP53B2EF504K 
manium rectifiers supplied by Sylvania 
and CBS Hytron suffered drastic 
changes in forward and backward cur- 
rent characteristics before reaching an 
integrated thermal flux of 10!7 n/cm?. 
The silicon rectifiers suffered similar 
damage except for two manufactured 
by Microwave and one manufactured 
by Bomac. These three remained in 
operation during the entire test. Their 
successful operation indicates that 
semiconductor rectifiers can be de- 
veloped (or present-type modified) 
for more severe radiation environment. 
t 2 3 oe 
Integrated Tharmal—Neutron Flux (10'%n/em? ) 
FIG. 6. Dissipation factor of paper capacitors, rises with irradia- 
Charts show effect of reactor fluxes (thermal 6.34 101! 
n/cm?/sec) on Aerovox and Sprague and Cornell-Dubilier type 
Vacuum Tubes 
Vacuum tubes vary greatly in mate- 
rials, size, complexity, and resistance to 
radiation. The most common causes 
of failure appear to be the deterioration 
of the glass envelope with subsequent 
gas problems, and cathode deteriora- 
tion, sometimes associated with the 
presence of gas in the tube. More 
evidence is needed before a positive 
statement can be made, but it appears 
that the principal problem is to keep 
gas from inside the tubes. 
Several tube types survived an irradi- 
—— 9 CBS 24 
® oe GBS. 21 
mame A SYL 17 
Current (milliamperes) 
je (3 > 
ie) I 2 3 
integrated Thermal— Neutron Flux (10!’n/cm?) i 
F sais | 
FIG. 7. Germanium rectifiers show this response to reactor radiation. Curves are for 
two CBS and one Sylvania crystal of type 1N58. 
X Reactor down 
© Reactor up 
5 6 7 8 9 
Forward currents, shown by curves 
labeled "'F,"" were measured with applied potential of 1 volt; backward currents with 
potential of 10 volts. 
Thermal-neutron flux was 0.3 X 10!2 n/cm?/sec. 
One other 
Sylvania crystal was considered destroyed at 3.05 < 10!’ n/cm? when its backward 
current rose above 5 ma 
