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-DENSE FLINT GLASS -P2
FILM
I MICROSECOND MAGNETO OPTIC SHUTTER
PHOTOCELL TRIP
Fig. 3. Rapatronic magnetooptic camera arrangement used to photograph the argon flashlamp.
argon, that is, at the rear portion of the lamp and around the apex of the conical charge.
Figure 2 is a scaled reproduction of the oscillograms obtained on explosive flashlamps having frontal argon atmospheres 0.5, 1 and 2 cm thick. No corrections have been made for adjustment to reference oscillograms obtained with a standard 1 0 million cp lamp prior to each experimental shot. With 0.5 cm of argon the major portion of the flash was over in 1 jusec or less. The exact shape of the increasing and decreasing luminosity curve could not be ascertained on the recorded scale. The average of the three records for 0.5 cm of argon, by comparison with records of a standard 1 0 million cp lamp, reveals a peak intensity of about 225 million cp. The flashlamps with 1 cm of argon had a duration of 2 /isec for the maximum luminosity, and the initial rate of increase in luminosity appeared to be approximately that for the 0.5-cm argon layer, but there was a slightly higher maximum. The maximum intensity was 250 million cp. With 2 cm of argon the first and major portion of the luminosity increase was practically as rapid as for the two preceding spacings; however, the duration of the maximum luminosity was about 4 /usec, and the peak intensity was about 300 million cp. The uncertainty of the reference standard for this record makes the
maximum a littie more uncertain than for the others. A small, trailing luminosity was evident about 1 or 2 jusec after the main flash in all cases. This phenomenon could be attributed to a lagging luminosity at the circumference, as indicated in Fig. IB.
Discussion of Results
The oscillograms indicate that the duration of the main flash from the argon flashlamp, as measured by the writers, is about 2 ^isec for each centimeter of thickness of the argon layer. The maximum intensity is developed after one-half to three-quarters of this time interval has elapsed. The measurements cover argon layers 0.5 to 2 cm thick. The time for development of the maximum intensity probably is related to the time required for the shock wave in the argon to reach the front of the lamp.
The average peak intrinsic brilliancy of the sheet of light-radiating argon gas is calculated by dividing the peak light (225 million cp) by the area (33 sq cm). This value is 6.8 million cp/square centimeter. Flash bombs with larger output would supposedly be of larger argon area. Some care might be required to initiate the flash of all portions of the sheet of gas at the same instant.
The duration and light-intensity data of Muraour et al.2>3 closely resemble
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September 1952 Journal of the SMPTE Vol. 59