1396 
III. INSTRUMENTATION 
Experimental results in this program were obtained with 
UERL Type B gauges), the initial work being done with 3/8 in. 
diameter gauges and the pend shooting with 1/4 in. gauges. These 
gauges were mounted on 5 ft lengths of wax-filled copper tubing 
chosen for low cable signal. The tubing was in turn spliced to 
75 ft lengths of copolene cable. To record the gauge signals, 
four DuMont 208 Cathode Ray Oscilloscopes were used as previous 
ly modified at this laboratory, and further modified as will be 
described below. The cameras which were used in photographing 
the oscilloscope screens are of the rotating=drum type, accomm- 
odating a 10 in. strip of 35 mm film. The associated electronic 
equipment used to fire the charge, to synchronize the oscillo-= 
scope beam brightening with the detonation, and to obtain voltage 
and timing eer a is essentially the same as has been pre= 
viously described.2 
The time resolution required in the study of small-charge 
shock waves imposed severe demands upon the above equipment, 
particularly since the surface-reflection phenomena are of 
durations as short as 10 microsec. The necessary resolution 
required a writing speed of at least 0.7 millisec per in., more 
than twice the fastest drum speed for which the equipment had 
been designed. The high speed was obtained by running the camera 
motors, which were Elinco Midget Type F=78 6-volt D.C. motors, 
from a 12=<volt supply. Variable drum speeds corresponding to 
writing speeds of from 0.7 to 1.0 millisec per in. were thus 
obtained. 
At these writing speeds further modification of the existing 
equipment was necessary to obtain readable photographic records, 
The intensifier voltage on the 5LP5 cathode ray tubes was increased 
from the 1000-volt value indicated in OSRD Report No. 6238 to 
3000 volts, giving a total voltage across each tube of 000 
volts. Although the deflection sensitivity was thus slightly 
decreased, the gain provided by the amplifiers continued to be 
more than adequate for input voltages of more than 0.5 volts. 
With increased intensity, satisfactory photography of the 
scope faces was boon ee with an f:1.4 Zeiss Biotar lens and 
Eastman Kodak PF402 green-sensitive Photoflure film. However, 
the necessity for recording a time scale simultaneously with 
the piezoelectric record imposed stricter requirements on the 
fiim, Timing marks were obtained from a crater tube (Sylvania 
type R-1130B) mounted inside each,camera hood, just as des- 
eribed for other UERL equipment.2) Because the crater-tube 
flashes are red, the Photoflure is relatively insensitive to 
them, and at the drum speeds needed here the timing pips did not 
show up at all, Therefore, it was necessary to use Eastman 
LP421 Linograph Pan recording film, which is panchromatic but 
also particularly sensttive to the blue-green cathode ray tube 
light. By force-developing the films thus obtained for 20 min=~ 
utes in D-19, readable records were obtained. 
= hes 
