percentage increase was proportional to the 
amount of iron in the core and inversely pro- 
portional to the frequency range in which the 
core was designed to be operated, The induct- 
ance of the coil wound on the 75 per cent 
nickel-iron core did not change significantly as 
the pressure was increased to 8000 psig. This 
coil also showed some permanent effects and a 
very small change in inductance as the pressure 
was increased from 8000 psig to 10, 000 psig. 
A "flux-gate'' type magnetometer was 
tested under pressure with some rather pecul- 
iar results, It should be noted that whereas the 
toroidal cores for the previous test were 
essentially free from external magnetic effects, 
the ''flux-gate'' element was readily susceptible 
to external magnetic field changes, Tests with 
the '"flux-gate'’ element in the tank showed that 
a considerable change occurred as the pressure 
was increased, Similar changes were noted 
with the "flux-gate'' element taped to the out- 
side of the tank wall as the pressure was in- 
creased inside the tank. These results appear 
to indicate that considerable changes in the 
magnetic condition of the tank occur as the 
pressure in the tank is varied, 
GLASS TUBES AND ENVELOPES 
Various types of glass tubes and envelopes 
were subjected to high hydrostatic pressures, 
A type 6AL5 miniature tube (Figure 8) was 
tested and observed to fail by catastrophic 
implosion at about 2000 psig. Some subminia- 
ture types (Figure 9), however, were found to 
withstand the full 10,000 psig without mechani- 
cal or electrical failure, 
Penlight bulbs, instrument bulbs, and 
small commercial neon bulbs were tested and 
a high percentage of these were found capable 
of withstanding the full 10,000 psig without 
mechanical or electrical failure. Several 
dozens of the penlight bulbs were tested, and 
there were a few failures in each test group, 
Failure sometimes occurred by implosion and 
sometimes by oil leaks through the seal. Pen- 
light bulbs which did not fail were set aside for 
use in illuminating samples under test, 
The pressure vessel (Figure 1) used in 
these experiments has been fitted with an 
optical viewing port (Figure 10), a and b, 
Illumination from a number of penlight bulbs 
is directed on the object to be viewed within 
121 
the tank, permitting observation of mechanical 
deformation of samples under pressure, A 
picture taken through the pressure window with 
illumination from these penlight bulbs is shown 
in Figure 11. Power to operate the bulbs is 
derived from a nickel-cadmium cell (Figure 
12). The vent of the cell was removed, and a 
rubber tube partially filled with electrolyte was 
installed for pressure equalization purposes, 
This cell was tested under a heavy-duty 
charge-discharge cycle both at 0 psig and 
10, 000 psig with no significant difference in 
performance noted, While discussing the 
pressure tank, it should be mentioned that all 
the measurements are made with the tank 
filled with paraffin oil. Electrical leads are 
brought out the cover through pressure glands, 
Glass tubing of various diameters was tested 
by sealing both ends of short lengths of tubing 
and then subjecting the samples to high 
pressure, The seals consisted of surgical 
rubber tubing fitted over the glass tubing, 
The opposite ends of the rubber tubes were 
blocked with small solid cylinders of the same 
diameter as the glass tubes (see Figure 4). 
When the hydrostatic pressure increases, the 
rubber seals are squeezed tighter around the 
glass tube and the solid cylinder, Glass tubes 
with a wall thickness of 0.039 in. and an out- 
side diameter of as great as 0, 355 in, 
successfully withstood 10,000 psig. It should 
be observed that glass has a compressive 
strength comparable to that of some steels, 
These results indicate that where the need 
arises some components in glass envelopes 
may be used ina high-pressure environment, 
SEMICONDUCTORS 
Many semiconductor devices (diodes, 
tunnel diodes, rectifiers, and transistors) were 
tested under hydrostatic pressures to 10, 000 
psig. It is common practice to seal the active 
transistor element in a metal case filled with 
some inert material to prevent contamination 
of the transistor and subsequent change in 
characteristics, if not complete failure, 
Transistor cases are not constructed to with- 
stand the high pressure involved in this study, 
so most of the transistors failed the test. A 
few of the very small elements did withstand 
10,000 psig successfully, but most of the cases 
collapsed (Figure 14). Also, some early 
transistor types which were potted in an epoxy 
