title: Two-frequency heating technique at the 18 GHz electron cyclotron resonance ion source of the National Institute of Radiological Sciences.
abstract: The two-frequency heating technique was studied to increase the beam intensities of highly charged ions provided by the high-voltage extraction configuration (HEC) ion source at the National Institute of Radiological Sciences (NIRS). The observed dependences on microwave power and frequency suggested that this technique improved plasma stability but it required precise frequency tuning and more microwave power than was available before 2013. Recently, a new, high-power (1200 W) wide band-width (17.1-18.5 GHz) travelling-wave-tube amplifier (TWTA) was installed. After some single tests with klystron and TWT amplifiers the simultaneous injection of the two microwaves has been successfully realized. The dependence of highly charged ions (HCI) currents on the superposed microwave power was studied by changing only the output power of one of the two amplifiers, alternatively. While operating the klystron on its fixed 18.0 GHz, the frequency of the TWTA was swept within its full limits (17.1-18.5 GHz), and the effect of this frequency on the HCI-production rate was examined under several operation conditions. As an overall result, new beam records of highly charged argon, krypton, and xenon beams were obtained at the NIRS-HEC ion source by this high-power two-frequency operation mode.
authors.affiliation: National Institute of Radiological Science (NIRS), 4-9-1 Anagawa, Inage, Chiba 263-8555, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Biri
authors.affiliation: National Institute of Radiological Science (NIRS), 4-9-1 Anagawa, Inage, Chiba 263-8555, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Kitagawa
authors.affiliation: National Institute of Radiological Science (NIRS), 4-9-1 Anagawa, Inage, Chiba 263-8555, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Muramatsu
authors.affiliation: National Institute of Radiological Science (NIRS), 4-9-1 Anagawa, Inage, Chiba 263-8555, Japan.
authors.forename: A G
authors.initials: AG
authors.lastname: Drentje
authors.affiliation: Institute for Nuclear Research (ATOMKI), H-4026 Debrecen, Bem tér 18/c, Hungary.
authors.forename: R
authors.initials: R
authors.lastname: Rácz
authors.affiliation: Graduated School of Engineering, Osaka University, 2-1 Yamada-oka, Suita-shi, Osaka 565-0871, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Yano
authors.affiliation: Graduated School of Engineering, Osaka University, 2-1 Yamada-oka, Suita-shi, Osaka 565-0871, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Kato
authors.affiliation: Accelerator Engineering Corporation (AEC), Inage, Chiba 263-0043, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Sasaki
authors.affiliation: Accelerator Engineering Corporation (AEC), Inage, Chiba 263-0043, Japan.
authors.forename: W
authors.initials: W
authors.lastname: Takasugi
mesh_terms: D000047:Academies and Institutes; D017357:Cyclotrons; D004583:Electrons; D006358:Hot Temperature; D008872:Microwaves; D011871:Radiology