Two-stage dense plasma heating by 100 kJ E-beam

The experimental results on heating of a dense plasma by an electron beam on the GOL-3 device are presented. The relativistic electron beam is injected into a 7-meter long plasma column of a mirror machine. The beam can transfer about 20–30% of its energy into 1–10 keV plasma electrons due to collective effects. These electrons are slowed down in a 0.5–3 meter long gas cloud of a 10¹⁶–10¹⁷ cm⁻³ density (so-called two-stage heating scheme). The hot electrons ionize this cloud and heat the dense plasma due to binary collisions. The total energy deposited in the cloud is 2–4 times higher than the instantaneous energy content of the lower density homogeneous plasma. Pressure waves were observed in the plasma. The mean energy of the hot electrons was estimated from measured energy deposition along the plasma cloud. The experiment demonstrates a high efficiency of the two-stage scheme of a dense (10¹⁶–10¹⁷ cm⁻³) plasma heating.