Laser-direct-drive fusion target design with a high-Z gradient-density pusher shell

Authors

S. S. Hu, University of Rochester
L. Ceurvorst, University of Rochester
J. L. Peebles, University of Rochester
A. Mao, University of Nebraska–LincolnFollow
P. Li, University of Nebraska-LincolnFollow
Yongfeng Lu, University of Nebraska - LincolnFollow
A. Shvydky, University of Rochester
V. N. Goncharov, University of Rochester
R. Epstein, University of Rochester
K. A. Nichols, University of Rochester
R. M. N. Goshadze, University of Rochester
M. Ghosh, University of Rochester
J. Hinz, University of Rochester
V. V. Karasiev, University of Rochester
S. Zhang, University of Rochester
N. R. Shaffer, University of Rochester
D. I. Mihaylov, University of Rochester
J. Cappelletti, University of Rochester
D. R. Harding, University of Rochester
C. K. Li, Massachusetts Institute of Technology
E. M. Campbell, MCM Consulting
R. C. Shah, University of Rochester
T. J. B. Collins, University of Rochester
S. P. Regan, University of Rochester
C. Deeney, University of Rochester

Date of this Version

9-19-2023

Citation

PHYSICAL REVIEW E 108, 035209 (2023). DOI: 10.1103/PhysRevE.108.035209

Comments

Used by permission.

Abstract

Laser-direct-drive fusion target designs with solid deuterium-tritium (DT) fuel, a high-Z gradient-density pusher shell (GDPS), and a Au-coated foam layer have been investigated through both 1D and 2D radiationhydrodynamic simulations. Compared with conventional low-Z ablators and DT-push-on-DT targets, these GDPS targets possess certain advantages of being instability-resistant implosions that can be high adiabat (α ≽ 8) and low hot-spot and pusher-shell convergence (CR_hs ≈22 and CR_PS ≈17), and have a low implosion velocity (v_imp < 3 × 10⁷ cm/s). Using symmetric drive with laser energies of 1.9 to 2.5 MJ, 1D LILAC simulations of these GDPS implosions can result in neutron yields corresponding to ≳50−MJ energy, even with reduced laser absorption due to the cross-beam energy transfer (CBET) effect. Two-dimensional DRACO simulations show that these GDPS targets can still ignite and deliver neutron yields from 4 to ∼10 MJ even if CBET is present, while traditional DT-push-on-DT targets normally fail due to the CBET-induced reduction of ablation pressure. If CBET is mitigated, these GDPS targets are expected to produce neutron yields of >20 MJ at a driven laser energy of ∼2 MJ. The key factors behind the robust ignition and moderate energy gain of such GDPS implosions are as follows: (1) The high initial density of the high-Z pusher shell can be placed at a very high adiabat while the DT fuel is maintained at a relatively low-entropy state; therefore, such implosions can still provide enough compression ρR >1 g/cm² for sufficient confinement; (2) the high-Z layer significantly reduces heat-conduction loss from the hot spot since thermal conductivity scales as ∼1/Z; and (3) possible radiation trapping may offer an additional advantage for reducing energy loss from such high-Z targets.