On intense electron beam propagation through gas jets

Abstract

The structure of the ionization front created by an expanding high-intensity electron beam as it travels through ∼1atm gas is considered theoretically. The velocity of the front, Vf, on the order of a few 10∧9cm∕s, is determined by the electric field ionization process. When decreasing the gas density, the velocity Vf decreases relatively slowly up to some threshold, after which it starts rapidly falling. The magnitude of Vf is higher for argon than for helium. These findings are supported by experimental observations.

LASER-driven fast electron dynamics in gaseous media under the influence of large electric fields

“…Figure 6 shows a typical simulation result of a proton image, corresponding to a maximum electrostatic field of Ϸ10 11 V / m and a fall-off distance of Ϸ10 m. Such values are in fair agreement with the expectations from theory. 9,14,17 Of course since the total deviation depends on the line integral ͐Edx, other values of the maximum field and fall-off distance can also reproduce our images. However for too-low electric fields, it is not possible to expel all the protons from the region inside the front ͑as it happens in our case as shown in Fig.…”

“…7,14,17 In particular, we have shown that ͑i͒ the propagation velocity and propagation distance increase with gas pressure and ͑ii͒ the propagation velocity slows down with time.…”