Shine-through for hydrogen and helium beams in a plasma was measured. Shine-through for an atomic hydrogen beam with f1:f 2:f3=7%:32%:61% (where f1, f2 and f3 represent fractions of the full, half and third energy, respectively) and a full energy of 140 keV, was smaller than the value predicted by usual cross-sections without inclusion of excitation processes at an electron density (ne) above 3*1013 cm-3. A fractional beam stopping increment ( delta ), which was defined by delta =( sigma s- sigma s(0)) sigma s (0) (here sigma s was an experimental stopping cross-section and sigma s(0) was the cross-section without including multistep processes via excited states), was about 0.2 at n e=(3.1-5.0)*1013 cm-3 and Z eff=1.6-2.5. The value of delta was consistent with the calculation by Janev et al. (1989, Nucl. Fusion 29, 2125). For a 160-190 keV helium beam, the enhancement of the stopping cross-section was not observed, as expected.
ASJC Scopus subject areas
- Nuclear Energy and Engineering
- Condensed Matter Physics