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Anomalous yield reduction in direct-drive deuterium/tritium implosions due to additiona)
a)Paper BI 1 3, Bull. Am. Phys. Soc. 53, 19 (2008).
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Image of FIG. 1.
FIG. 1.

permeation half-lives for each individual shell used on shot day. Error bars on shell show reproducibility of measurement.

Image of FIG. 2.
FIG. 2.

Estimated concentration at shot time based on individual leak rates of Fig. 1. Capsules contained of DT at shot time. Capsules were stored for several days in cells pressurized with to either 0, 1.26, or 6.05 atm, resulting in atomic concentrations at shot time averaging 0%, 10%, or 36%, respectively. Data points on the axis represent the concentration just before depressurization of the gas cell and are for illustrative purposes only.

Image of FIG. 3.
FIG. 3.

DT neutron and gamma yields as a function of concentration measured by nTOF (blue diamonds) and GCD (red squares), respectively. Typical absolute yield uncertainty for the nTOF is . Typical relative yield uncertainty for the GCD is also , but absolute yield uncertainty is greater due to uncertainties in GCD absolute calibration and the branching ratio.

Image of FIG. 4.
FIG. 4.

DT fusion reaction histories from the GCD (solid blue line) and the NTD (dashed pink line) show the growth of a feature near 1.25 ns as is added. Instrument response has been deconvolved from the data for both detectors. No NTD data were acquired on two shots (47873 and 47876). NTD data for shot 47877 were used to establish an absolute time base for the GCD data.

Image of FIG. 5.
FIG. 5.

Burn averaged ion temperature measured by neutron time-of-flight (nTOF) in solid black diamonds (blue online), the mean of the measurements in open black diamonds (blue online), and a clean calculation (i.e., no shell/fuel mix) in solid gray diamonds (pink online).

Image of FIG. 6.
FIG. 6.

Temporal dependence of x-ray image radius for a 36% shot from the QXI (green diamonds) and clean calculation (open blue circles) shows less compression than expected.

Image of FIG. 7.
FIG. 7.

Gaussian decomposition of deconvolved reaction histories measured using the GCD instrument for (a) 0% , (b) 10% , and (c) 36% addition. Individual deconvolved reaction histories at each concentration are shown in dashed lines. Composites of the Gaussian fits to these reaction histories are shown in solid lines for the yield components arising from shock [gray (pink online)] and compression [black (blue online)], with their sum in bold black lines labeled GCD. Vertical scale is linear with the line shown in each case by a horizontal dashed line (red online) for reference. In (d)–(f) are shown the comparisons of the composites of the GCD measured reaction histories (black solid line) and calculated [dashed line (green online)]. Calculated histories are from a 1D rad-hydro “clean” calculation convolved with a 20 ps Gaussian to simulate instrument response.

Image of FIG. 8.
FIG. 8.

Reduction in Gaussian fits into (a) peak burn rate, (b) full width at half maximum (FWHM, semilog scale), (c) bang time, and (d) neutron burn (semilog scale). Parameters from the forward-folded fit to experimentally measured reaction histories are shown in ’s and ×’s, with their averages in open symbols/solid lines (i.e., Obs) and those from the fit to calculated reaction histories assuming no mix are shown in solid symbols/dashed lines (i.e., Clean). Shock components are in black (blue online) and compression components are in gray (pink online).

Image of FIG. 9.
FIG. 9.

Ratio of observed to clean calculated yields from Fig. 8(d).

Image of FIG. 10.
FIG. 10.

YOC for (a) compression yield component normalized at 0% and (b) shock yield component normalized at 50% for the MIT study and no normalization for the current study. In both frames, the MIT -filled plastic capsules are shown in light blue downward pointing triangles for thick CH capsules and dark blue upward pointing triangles for thick CH capsules. The current study using -filled thick glass capsules are shown as solid red circles. The LANL results are for , while the MIT compression yield results in (a) are determined from DD-n and the MIT shock yield results in (b) are determined from .


Generic image for table
Table I.

As-shot conditions. Shell inner diameter and wall thickness refer to dimensions of the microballoon target. DT and pressures in the target at shot time are estimated from initial fill pressures corrected for DT and leakages based on time at room temperature and time outside of the -pressurized cell until shot time. Ion temperature and neutron yield are determined using the nTOF instrument located at 12.4 m from the target chamber center. YOC is based on measured yields divided by predicted yields calculated assuming no fuel-shell mix (i.e., a clean calculation) in a 1D rad-hydro model.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Anomalous yield reduction in direct-drive deuterium/tritium implosions due to H3e additiona)