MIL-PRF-1/1049H
TABLE I. Testing and inspection - Continued.
4/ After a holding period of 672 hours, which shall not include the manufacturer's stabilizing period of at least 336 hours, the
conversion index of the tube shall not be less than 15, and shall not have slumped more than 20 percent from the initial value
measured at the end of the stabilizing period. If the conversion index has slumped more than 20 percent, but still is above the
minimum value of 15, the tube shall be held an additional 2 weeks. At the end of the 6-week period, the tube shall have a conversion
index of not less than 15 and shall not have slumped more than 30 percent of the initial value. After completing the above
conversion index test, the manufacturer shall have a period of 24 hours to screen out tubes he feels do not meet the requirements
specified herein.
5/ This test is to be performed at the conclusion of the holding period.
6/ Upon completion of the vibration (1) test specified, each tube, in a proper holder, shall be energized with 16 kilovolts for a
stabilization period of 15 seconds in a darkened room (not more than 0.01 footcandle (0.11 lux)). At the end of this period, with the
tube still energized and no incident light on the photocathode, it shall be subjected to shock impacts in the following manner:
The shock impacts shall be applied in a way to generate nominal half-sine wave pulses having a minimum of 75 G's at the
peak. The duration of each shock pulse shall be 6 ± 2 milliseconds measured between the 10 percent values of the peak
amplitude. The energy under the shock curve shall be not less than 0.25 G second and the after oscillations shall be not
greater than 15 percent of the peak amplitude of the nominal half-sine wave pulse. The tube shall be subjected to six shock
pulses parallel to, and six shock pulses perpendicular to, its longitudinal axis. Presence of flashing or electrical bursting during
more than two shocks in each direction shall be cause for rejection.
7/ The image tube shall be subjected to an irradiation surge by exposing the photocathode to radiation from a tungsten light source
(which need not be the one specified in 1/) for a period of at least 5 seconds to produce a minimum of 3.5 µA of photocathode
current. The image of the source on the screen of the tube shall not disintegrate nor shall any part of the image darken or be
blanked out during the irradiation surge.
8/ The radiation source, specified in 1/, shall be used to produce a circular image .750 inch (19.05 mm) in diameter on the center of
the photocathode. The amount of incident flux on the photocathode (prior to interposing the filter) shall be 0.01 ± 0.0005 lux. The
light output of the tube shall be read with a W eston Model 856 RRV photronic cell, or equivalent, provided with a Viscor filter or
equivalent and truncated lucite cone. The cone shall be 1.562 inches (39.67 mm) in diameter at its base, 1.125 inches (28.58 mm)
in diameter at its top, and 1.6875 inches (42.86 mm) in height. The base of the cone shall be cemented to the photronic cell
window. The cone top shall be in contact with the image screen of the tube. The photronic cell and cone shall be precalibrated from
a diffused light source. The small end of the cone shall be placed to cover the excited area of the image screen. The conversion
index is defined as:
CI = F1/F2T
F1 is the total available luminous flux emitted by the phosphor screen of the tube at the operating voltage specified.
F2 is the unfiltered flux from the 2,854°K light source incident on the photocathode of the tube.
T is the filter factor of a calibrated Corning No. 2540 (melt number 1613, .103 inch (2.61 mm) thickness) infrared filter, or
equivalent, interposed between the light source and photocathode. This filter factor is the percentage of 2,854°K hololumen
flux transmitted by the infrared filter and is determined by the following:
∞
∫ο Rλ Jλ tλ dλ
T=
∞
∫ο Rλ Jλ dλ
W here Rλ = The relative spectral response of an EIA S-1 photosurface.
Jλ = The relative spectral distribution of the 2,854°K color temperature radiation source.
tλ = The spectral transmission of the infrared filter.
dλ = The differential of the wavelength of the radiation.
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