The Visible Radiation from Helium in a Strong Shock Wave Page: 9
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The diameter of the tube was somewhat arbitrary above a minimum
value where the boundary layer effects were great enough to cause observ-
able deviations from planarity In the wave. This minimum diameter was
somewhere between 1M and 2i’\ Also, clearly, the bigger the tube the more
light produced per unit area normal to the axis of the tube.
The construction of the closed end of the tube depended on the
method of observing the spectrum. For time-Integrated spectra the 1’yrex
end plate was sealed on by a glassblower and observations were made
through this flat surface. Time-resolved spectra, however, were observed
through the cylindrical surface near the closed end, and distortion caused
by blowing the glass In this region could not be tolerated. In this case,
the end plate was cut as shown in Mg. 2 and cemented to the cylinder with
Armstrong A-l Cement.
The tuoe-explosive assembly was sealed to a glass hlgh-vacuum
system which could be evacuated to about 10 1 mm Hg. This system con-
sisted of a mercury diffusion pump and forepump with three cold traps ad-
vantageously located. A glass bulb of s «ctroscopically pure helium was
also sealed to the system In such a manner that the helium passed through
two of the Uquld-nltrogen-cooled traps on Its way to the shock tube. The
shock tube was evacuated to about 10 mm Hg, baked at about }QO*C in re-
gions remote from the explosive, flushed and evacuated again, filled to
the desired pressure, and sealed off at the constriction shown In Fig. 1.
Shock wave velocities and shapes were observed with a rotating
mirror type smear camera. The operation of the camera Is shown schematl-
c 3 a fMfc
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Seay, Glenn Emmett. The Visible Radiation from Helium in a Strong Shock Wave, report, January 1957; Los Alamos, New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc502356/m1/16/: accessed June 17, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.