Integration of 175-MHz LIPAc RF System and RFQ Linac for Beam Commissioning

• Published in: IEEE transactions on plasma science Vol. 48; no. 6; pp. 1489 - 1495
• Main Authors: Shinya, Takahiro, Weber, Moises, Fagotti, Enrico, Hayashi, Kenichi, Kubo, Naoya, Marchena, Alvaro, Moya, Ivan, Regidor, David, Scantamburlo, Francesco, Akagi, Tomoya, Antoniazzi, Loris, Bellan, Luca, Cara, Philippe, Comunian, Michele, Dzitko, Herve, Ebisawa, Takashi, Gex, Dominique, Grespan, Francesco, Hirata, Yosuke, Jokinen, Antti, Kasugai, Atsushi, Kirpitchev, Igor, Kobayashi, Hitoshi, Kondo, Keitaro, Maebara, Sunao, Mendez, Puri, Molla, Joaquin, Montis, Maurizio, de Morena, Cristina la, Nakayama, Takahide, Palmieri, Antonio, Pisent, Andrea, Sakamoto, Keishi, Shimosaki, Yoshito, Sugimoto, Masayoshi, Takayama, Ken
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-06-2020; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acceleration; Chains; Circulators; Conditioning; Deuteron beam; Deuterons; Feedback control; International Fusion Materials Irradiation Facility (IFMIF); Ion beams; Linear IFMIF Prototype Accelerator (LIPAc); Linear particle accelerator; Particle beams; Quadrupoles; Radio frequency; radio frequency quadrupole (RFQ) linac; Reflection; RF system; Steady-state; Tetrodes
• ISSN: 0093-3813; 1939-9375
• DOI: 10.1109/TPS.2020.2985020

The eight-chain RF system and radio frequency quadrupole (RFQ) linac were successfully integrated at the facility of the Linear IFMIF Prototype Accelerator (LIPAc). We achieved an unprecedented high current deuteron beam up to 55 mA in pulse operation (<inline-formula> <tex-math notation="LaTeX">300~\mu \text{s} </tex-math></inline-formula>, 1 Hz). The keys of the success were (1) understanding reflected power from RFQ to RF system, (2) tuning each RF chain individually, (3) intensive RF conditioning for holding the stable RF power in the RFQ, and (4) optimizing the beam loading compensation control. Interestingly, the reflection at the breakdown in RF conditioning was higher than an estimation and reached up to 600 kW so far. In order to avoid damage on tetrodes by the high reflection, the impedance of each circulator was accurately adjusted.