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Architecture, implementation, and testing of a multiple-shell gas injection system for high current implosions on the Z accelerator
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View: Figures


Image of FIG. 1.
FIG. 1.

Overall layout of gas puff system on Z.

Image of FIG. 2.
FIG. 2.

Cross-section view of 80-mm multiple shell nozzle mounted in MITL of Z and enlarged cross-section view.

Image of FIG. 3.
FIG. 3.

Photographs of 80-mm nozzle for first tests on Z (note absence of central jet).

Image of FIG. 4.
FIG. 4.

Photograph of 80-mm multiple-shell nozzle including central jet.

Image of FIG. 5.
FIG. 5.

Photograph of one 120-mm multiple-shell nozzle for Z.

Image of FIG. 6.
FIG. 6.

Grey scale image of Ar gas density in front of the 80-mm dual-shell nozzle for Z; 22 psi (absolute) outer and 30 psi (absolute) inner.

Image of FIG. 7.
FIG. 7.

Density vs. radius in recessed, 120-mm multiple shell nozzle, at a distance of 20 mm from nozzle face.

Image of FIG. 8.
FIG. 8.

Cross-section drawing of recessed, 120-mm multiple shell nozzle for Z.

Image of FIG. 9.
FIG. 9.

Cross-section drawing of recessed, 80-mm multiple shell nozzle.

Image of FIG. 10.
FIG. 10.

Alignment features for 80-mm multiple-shell nozzle.

Image of FIG. 11.
FIG. 11.

Sample scan of a throat plate. Other than the (nearly) full circle annular throat gaps, the other holes in each plate are for registration pins or clearance holes for mounting the nozzle pieces to the valve plate.

Image of FIG. 12.
FIG. 12.

Azimuthal “lineout” of the middle gap width (nominal 0.41 mm) versus angle. The variations with azimuth for this particular throat plate are less than ±2.5%.

Image of FIG. 13.
FIG. 13.

Frontal views of 80-mm nozzle with wire grid across face, showing a laser line-of-sight between wires (left) and along a wire (right).

Image of FIG. 14.
FIG. 14.

Chordal interferometer scans of Ar gas flow (P = 31 psi (absolute), P = 58.5 psi (absolute), and P = 0), at various axial distances from nozzle face, with laser aligned between wires (without grid, shown in green) and along a wire (with grid, shown in saffron).

Image of FIG. 15.
FIG. 15.

Areal density maps (false color scale to the right) for 80-mm nozzle with no grid (left image), grid but laser between wires (middle image), and along a wire (right image).

Image of FIG. 16.
FIG. 16.

Areal density maps (grey scale to the right) for 80-mm nozzle with grid and probe laser along (see Figure 13 right) a wire (left image) and no grid (right image).

Image of FIG. 17.
FIG. 17.

Areal density vs. radius without cathode grid (black) and with grid (red).

Image of FIG. 18.
FIG. 18.

Total mass within a given radius (normalized) without grid (black) and with grid (red).

Image of FIG. 19.
FIG. 19.

Photograph (upper) of front and rear panels of gas valve driver; lower left shows the interior of the driver; lower right shows a typical measured current into outer coil (blue trace) vs. predicted current from a simple RLC loop (red trace).

Image of FIG. 20.
FIG. 20.

Measured inductance vs. distance from base plate, outer coil.

Image of FIG. 21.
FIG. 21.

Calculated outer coil motion (red) and piezo-resistive transducer signal (blue) taken at 15 mm from nozzle exit.

Image of FIG. 22.
FIG. 22.

Pressure transducer data from 15-shot sequence with Ar gas.

Image of FIG. 23.
FIG. 23.

Pressure transducer data from 15-shot sequence with Kr gas.

Image of FIG. 24.
FIG. 24.

Enlarged view of 120-mm nozzle cross-section showing one of two breakdown pins.

Image of FIG. 25.
FIG. 25.

Equivalent electrical circuit for breakdown pins.

Image of FIG. 26.
FIG. 26.

Currents, pressure sensor signal, and breakdown pin signals for a typical shot.

Image of FIG. 27.
FIG. 27.

Histograms of breakdown pin signals from 1150 shots (top) and histogram of AND logic occurrences (bottom).

Image of FIG. 28.
FIG. 28.

Photograph of the inductive isolator on the bench.

Image of FIG. 29.
FIG. 29.

Details of gas line and electrical cable layout from nozzle section back to the inductive isolator base.

Image of FIG. 30.
FIG. 30.

Photograph of the screen box that houses the flashboard driver on the mezzanine of Z; photograph of flashboard driver pulled out of the screen box: details in text; photograph of one flashboard driver module, showing four GA31151 capacitors arranged around a common GP41B Perkin-Elmer spark gap; and view (from bottom) of driver module to show how capacitors are connected to the PE spark gap and the 40 kV isolation capacitors (red) that deliver the fast trigger (see element b in the figure) to the PE spark gap.

Image of FIG. 31.
FIG. 31.

Isometric view of intermediate trigger module for flashboards; plan view of intermediate trigger; internal view of flashboard Local Driver Control Unit (LDCU); and schematic drawing of pre-ionizer assembly in Z load region.

Image of FIG. 32.
FIG. 32.

Photograph of large diameter UV flashboards designed for pre-ionizer on Z. Lower photograph shows flashboards during a discharge with individual beads on Kapton lighting up.

Image of FIG. 33.
FIG. 33.

Vacuum feedthrough flange that allows six coaxial cables to pass through into vacuum with individual O-ring seals; epoxy potted termination of coaxial cables at flashboard end (to provide vacuum seal and avoid corona at connection); banana-plug termination of coaxial cable at driver end (for easy disassembly after each shot); and expanded view of cable termination at flashboard with clamshell clamp prior to potting with bubble-free epoxy.

Image of FIG. 34.
FIG. 34.

Measured Pearson transformer waveform (blue) and calculated (red) waveform for 20 kV charge.

Image of FIG. 35.
FIG. 35.

Measured (Rogowski coil) waveform (blue) vs. RLC theory (red) into short circuit load of 5 ft of Reynolds cable.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Architecture, implementation, and testing of a multiple-shell gas injection system for high current implosions on the Z accelerator