Double-shell implosions open new paths for fusion science

Double-shell liquid deuterium-tritium (DT) capsules provide for a new platform to study fusion plasmas under extreme conditions. Unlike single-shell capsules typically used in ignition experiments, these have two nested layers: an outer shell that delivers energy inward and a high-density inner shell that compresses the DT fuel.

Palaniyappan et al. demonstrated the first-ever liquid DT filled double-shell implosions.

“The design enables what physicists call ‘volume burn,’ in which the fuel can ignite and burn more uniformly throughout its volume,” said author Sasi Palaniyappan.

The researchers conducted a series of experiments that achieved incredible results. With laser energies up to 1.5 megajoules, the capsules produced neutron yields nearly ten times higher than initial double-shell attempts. The shots were not designed to reach ignition, but they represent a dramatic step forward in demonstrating the stability and scalability of the approach.

A key advance came from carefully engineered capsule fabrication. By adding a thin layer of gold at the outer shell joint, the team could suppress instabilities that would otherwise disrupt the implosion.

“This design innovation accounted for much of the performance gain, and future improvements will focus on increasing the efficiency of energy transfer between the shells and further refining fabrication techniques,” said Palaniyappan.

Because the inner shell is made of high-atomic number metals like molybdenum, the implosions will provide a natural way to investigate how heavy elements mix with DT fuel, how radiation is trapped and re-emitted, and how kinetic energy is partitioned at extreme pressures and temperatures.

These are fundamental questions in fusion physics, with implications for both fusion energy and astrophysical phenomena such as supernovae.

Source: “First indirectly driven liquid-DT filled double shell implosions at the National Ignition Facility,” by S. Palaniyappan, E. N. Loomis, S. D. Negussie, J. P. Sauppe, R. L. Scott, H. F. Robey, N. S. Christiansen, P. M. Donovan, C.S. Wong, L. Kot, B. M. Patterson, D. W. Schmidt, T. E. Quintana, S. J. Stringfield, M. S. Freeman, M. Durocher, K. D. Meaney, D. S. Montgomery, W. S. Daughton, A. Rasmus, Z. L. Mohamed, T. Desjardins, P. J. Adrian, M. F. Huff, A. C. Hayes, B. A. Wetherton, J. J. Kuczek, B. T. Wolfe, B. M. Haines, C. H. Wilde, C. R. Danly, D. D. Meyerhofer, D. J. Stark, D. Lonardoni, G. J. Saavedra, G. Y. Rusev, H. Geppert-Kleinrath, I. Sagert, J. F. Dowd, E. C. Merritt, P. A. Keiter, R. H. Dwyer, R. S. Lester, R. F. Sacks, S. Goodarzi, V. E. Fatherley, H. J. Jorgenson, V. Geppert-Kleinrath, Y. H. Kim, J. L. Kline, J. M. Smidt, A. Nikroo, T. M. Briggs, J. J. Kroll, C. Choate, N. T. Roskopf, N. L. Hash, N. L. Orsi, S. D. Bhandarkar, J. Crippen, H. Huang, J. Murray, M. Ratledge, R. Santana, K. Sequoia, C. Shuldberg, W. Sweet, and H. Xu, Physics of Plasmas (2025). The article can be accessed at https://10.1063/5.0271552 .

This paper is part of the Papers from the 66th Annual Meeting of the APS Division of Plasma Physics Collection, learn more here.