Heavy-ion versus electron-beam excitation of an excimer laser

Abstract

A model is described for the heavy-ion pumping of an XeF(B) laser by uranium fission fragments (FF).The model is a self-consistent accounting of the generation and transport of the FF’s through the fission foils, slowing of the fragments in the gas, evolution of the secondary-electron-source function and distribution, and the XeF laser plasma kinetics. By simulating the same quantities for an e-beam-pumped plasma, direct comparisons can be made for laser performance. We found that the secondary-electron source generated by the e-beam is more energetic than that for direct ionization by FF’s due to a more favorable mass ratio for momentum transfer collisions with orbital electrons. This difference in the electron-source functions significantly affects W values and excitation fractions. The impact on laser performance, though, is not large due to the high efficiency of channeling deposited energy to the upper laser level in XeF lasers. For conditions typical of FF excitation (power deposition 1–3 kW cm−3, pulse length ≊200 μs), e-beam excitation results in 10%–15% higher gain than heavy-ion excitation.

Comments About Nuclear-Pumped Laser Research in the United States

“…In another study [34], Kushner and colleagues presented a model for the heavyion pumping of a XeF (B ! X) laser by uranium fission fragments.…”

“…More recently, studies were performed on the reactor-pumped atomic Xe laser at both 1.73 and 2.03 μm (first reported in [34]). Lasing was observed with the ACRR and SPR-III reactor facilities [37], and Rigrod experiments were performed to measure small-signal gain, saturation intensity, and non-saturable losses.…”

Nuclear-Induced Plasmas of Gas Mixtures and Nuclear-Pumped Lasers

“…Due to the large difference in masses of heavy charged particles and the electron, only a comparatively small percentage of fragment energy can be transferred to the orbital electron. The spectrum of electrons produced by ionization of heavy particles is softer compared with the spectrum produced by ionization of gas by fast electrons [22,23]. The average energy of electrons formed in neon as a result of ionization by fission fragments is 40 eV and fast electrons 150 eV [22].…”

“…The average energy of electrons formed in neon as a result of ionization by fission fragments is 40 eV and fast electrons 150 eV [22]. In the case of fission fragments, the secondary electron may provide additional one or two acts of ionization on average, while in the case of fast electrons, it is from 5 to 10 [23].…”

Electron-beam-sustained discharge revisited — light emission from combined electron beam and microwave excited argon at atmospheric pressure

“…Compared to discharges, this results in a rather similar respective EEDF at low energies, however showing a long high energy tail (compare ref. [6]), extending out to the particle energy of the incident electron beam.…”