ISSN:
1089-7623
Source:
AIP Digital Archive
Topics:
Physics
,
Electrical Engineering, Measurement and Control Technology
Notes:
Negative H− ion beams produced by a tandem-type H− ion source have good beam optics with a typical beam divergence angle of less than 5 mrad. However, the physical reason has not yet been made clear. To clarify the mechanism, we investigate a velocity distribution of negative ions at the extraction holes by a three-dimensional (3D) Monte Carlo transport code. In this code, surface-produced H− ion trajectories are calculated by numerically solving the 3D equation of motion for H− ions. The energy of the H− ions is relaxed through Coulomb collision with the background plasma (H+ ions), which has a low temperature of ∼1 eV in the tandem-type H− ion source. Therefore, energy relaxation by Coulomb collision plays an important role in good beam optics. © 2002 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.1431420
