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

Document Type

Article

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.