Wada M, Shinto K, Shibata T, Sasao M
School of Science and Engineering, Doshisha University, Kyotanabe, Kyoto 610-0321, Japan.
J-PARC Center, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan.
Rev Sci Instrum. 2020 Jan 1;91(1):013330. doi: 10.1063/1.5128015.
The AC component of a beam current extracted from a negative hydrogen (H) ion source was detected through a 0.1 mm wide, 66.5 mm long entrance slit to observe the spatial distribution. An internal antenna type multicusp source driven by a 2 MHz radio frequency (RF) power delivered beams to an electrostatic accelerator coupled to a pair of magnetic lenses. The local beam intensity measured by a Faraday cup after the entrance slit exhibited an oscillation showing two main frequency components: the RF power supply frequency and the frequency two times the driving RF. The frequency spectrum of the detected signal showed sharp peaks at 2 MHz, 4 MHz, and 6 MHz as well as at 3 MHz and 5 MHz. A 1 mm displacement of the Faraday cup slit position from the center of the beam axis increased the oscillation amplitude, corresponding to a larger amplitude of the AC component at the beam edge.
