Inst High Energy Phys, Beijing 100039, Peoples R China
; KEK, High Energy Accelerator Res Org, Accelerator Div, Tsukuba, Ibaraki 3050801, Japan
The JHF/JAERI linac is an injector of a 3-GeV ring. It consists of an H- ion source, a 3-MeV radio-frequency quadrupole linac, a 50-MeV drift-tube linac, a 200-MeV separated-type drift-tube linac and a 400-MeV ACS accelerator in its normal conducting section. As an intense beam linac with an average current of 0.2 mA (first stage) and higher in the second stage, the issue of decreasing beam losses is of prime importance, The MEET between the RFQ and the DTL has been designed with a modified TRACE3-D code, aimed at perfect matching, clear chopping, a small emittance growth and sufficient space for beam measurements. The line consists of eight quadrupoles, two bunchers and two choppers with a total length of about 3 m. Multiparticle codes PARMILA and LINSAC were used to check the beam dynamics of the design, Mismatch due to errors in the elements of the MEET or the input beam was also studied. A radio-frequency deflector (RFD) is adopted in the chopper. It is characterized by a high deflecting field and compactness, The RF-deflector cavity was designed using the MAFIA code and the electromagnetic field distribution, including fringe field, is applied in TRACE3-D simulation. It illustrates the effect of the beam tube in the cavity on large deflection. A deflection initiated by the RF-deflector is amplified more than twice by the following quadrupole. Owing to this merit, the required RF field of 1.6 MV/m is rather low to generate an adequate separation of 4.3 mm between chopped and unchopped beams at the beam stopper. By means of rapid changes in the RF amplitude and phase during the rise and fall time, the chopper has an equivalent rise and fall time of less than 3.1 ns. Beam losses during the transient time of the chopper are less than 0.08% at the exit of the 50-MeV DTL. An analysis of unstable particles in the coupled RF-deflectors shows no obvious difference from the case of an independent cavity. (C) 2001 Published by Elsevier Science B.V.
Fu SN,Fu, SN,Kato, T. Design study on a medium-energy beam-transport line for the JHF proton linac[J]. NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT,2001,457(3):423-437.
傅世年,Fu, SN,&Kato, T.(2001).Design study on a medium-energy beam-transport line for the JHF proton linac.NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT,457(3),423-437.
傅世年,et al."Design study on a medium-energy beam-transport line for the JHF proton linac".NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 457.3(2001):423-437.