A review of the dense Z-pinch

Plasma Phys. Control. Fusion 53 (2011) 093001
Topical Review
Figure 85. X-ray backlighter images of 17 µm Mo-wire X-pinches taken (a) 1.1 ns before the
thermal x-ray burst, (b) 0.3 ns before, (c) 0.56 ns after, (d) 2 ns after and (e) 11.4 ns after the
thermal x-ray burst. Reprinted with permission from [567]. Copyright 2005, American Institute
of Physics.
has been developed by Douglass and Hammer [577] using five X-pinches each of four Mo
wires in the return conductors, with relative timing controlled by varying the wire diameters.
In addition to directly backlighting wire arrays [578] the X-pinch has been used by
Bott et al [579] to diagnose the low density foam on the axis of a wire array. Appartaim
and Maakuu [580] have shown that successful X-pinches can also be produced with a more
conventional long pulse (∼1 µs quarter period) capacitor bank. With the right choice of wire
material and x-ray filter, highly localized bright spots suitable for point-projection radiography
can be produced. Beg et al [581] have shown how a compact X-pinch (80 kA in 50 ns) can be
used to show phase contrast effects in a plastic capsule (1 mm diameter, 20 µm thick wall with
a80µm foam inside). The high spatial resolution and short time exposure make the X-pinch
suitable to examine the quality of cryogenic layered targets for ICF.
7.7. Z-pinch with sheared axial flow stabilization
Provided the sheared axial flow is not too great so as to cause KH instabilities, its presence
can enhance stability. A very general theoretical dispersion equation was developed from the
Vlasov equation by Wright et al [193] which included sheared rotation and axial flows and
sheared heat flows (azimuthal and axial), axial and azimuthal magnetic fields and FLR effects.
As discussed in section 3.9 sheared flow can theoretically be stabilizing, but experimental
evidence for this is sparse. In 2001 Shumlak et al [188] claimed stabilization in the ZaP flow
Z-pinch. In the transit time of the flow of only 20 µs there are nevertheless many e-folding
times for instability growth, but the plasma conditions are such that LLR stabilization [12, 14]
could also play a significant role. The m = 1 and m = 2 modes can be observed from magnetic
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