X-ray source production in foil implosion machines Page: 4 of 8
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From the calculated radiated power curves shown in Figure 3, we see that there is a "weak" jet and
a "strong" jet, where "weak" and "strong" refer to the relative magnitudes of the power curves
obtained by integration over frequency of time dependent radial spectra produced
by the stagnation of the jets against the tungsten stopping blocks.
CONTOURED ELECTRODES AND TAILORED FOILS
Studies of the effects of a contoured electrode in the single jet producing configuration, shown in
Figure 4, were a continuation of the Pegasus work when radiation source development efforts were
shifted to the higher energy Procyon machine, which permits access from one side only. The
principle reasons for contouring the electrode without the axial hole were:
a) to position the hot portion of the z-pinch close to the axial hole where it would be most
accessible or produce a stronger jet,
b) to try to reduce variations in jet strength (caused by instability growth in the foil) by
compressing the imploding foil laterally,
c) and to determine if the pinch temperature could be increased by approximating a more
spherical foil implosion than that of the usual cylindrical z-pinch, thereby producing a hotter
source.
In order to begin an assessment of how sensitive jet production might be to foil perturbations when
using contoured electrode configurations, two calculations, P1 and P2, were run which used an
identical initial mass distributions along the foil but which differed only in that the orientation of the
foil with respect to the electrode hole was reversed. The foil mass distribution was one matched to
the Procyon test PDD1. Calculations corresponding to P1 and P2 with plane parallel electrodes and
a single electrode hole have not yet been run, but must be done before final conclusions can be
made. Figure 5 gives the average foil mass distribution used in the P1 calculation. It is seen that the
foil is somewhat more massive toward the electrode hole. (In calculation P2, the foil distribution
was reversed.) The powers radiated in the two cases at the stagnation plate are shown in Figure 6.
The stagnation timing and peak power amplitudes differ in the two calculations, but not extremely.
Having less mass near the electrode hole appears to create a faster jet, but having more mass there
appears to provide a stronger jet.
Two additional calculations, P3 and P4, were run to determine whether modification of the
average mass distribution along the foil length can be used to control or enhance source and jet
formation. Masses of the initial and final half centimeter of the two centimeter long foils were
increased and decreased, respectively, by ten percent, leaving the total mass unchanged, and
creating a "tapered" average mass along the foil with the perturbations relatively unchanged. A table
indicating the orientation of the foil mass distribution with respect to the hole in the electrode for
problems P1 through P4 is given below.
Figures 7 and 8 show the foil mass distributions obtained for problems P3 and P4. X-ray power
outputs from the jet stagnations of problems P1, P3, and P4 are given in Figure 9. It is seen again
that reducing the foil mass near the electrode hole (problem P3) produces an earlier but weaker
power output, while increasing this mass (problem P4) delays the onset of the x-ray output and
possibly increases the width of the power curve slightly. Additional work with tailoring of the
average foil mass distributions is needed to provide a fuller and clearer picture of the usefulness of
this procedure.
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Rich, M. & Matuska, W. X-ray source production in foil implosion machines, article, September 1, 1995; New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc620314/m1/4/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.