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Experiments on OMEGA EP Featured in Nature Physics Paper

February 06, 2023
Chien Nature Physics Paper and an illustration of a capacitor coil target driven by two long-pulse lasers.

A paper with the lead author Abraham Chien (National Laser Users Facility Ph.D. from Princeton University, 2021) titled “Non-thermal electron acceleration from magnetically driven reconnection in a laboratory plasma” was published recently in the journal, Nature Physics. This paper reports on the experimental results obtained on OMEGA EP, where the direct measurement of accelerated nonthermal electrons from magnetically driven reconnection at low β (ratio of plasma pressure to magnetic pressure ~ 0.05) were measured. Kilojoule OMEGA EP long-pulse beams were used to drive parallel currents to reconnect megagauss-level magnetic fields in a quasi-axisymmetric geometry. The angular dependence of the measured electron energy spectrum and the resulting accelerated energies, supported by particle-in-cell simulations, indicates that the mechanism of direct electric-field acceleration by the out-of-plane reconnection electric field is at work for the low-β collisionless reconnecting plasmas. Scaled energies using this mechanism show direct relevance to astrophysical observations. The work was part of Chien’s Ph.D. thesis research advised by Prof. H. Ji [Princeton University and Princeton Plasma Physics Laboratory(PPPL)] and Dr. L. Gao (PPPL). Several UR/LLE scientists (E. G. Blackman, R. K. Follett, D. H. Froula, and P. M. Nilson) participated in this research and are co-authors on the paper.