Fujita  M.

Okamura  H.

Orihara  H.

Shinozuka  T.

Suzuki  H.

Terakawa  A.

English

紀要類 (bulletin)departmental bulletin pape

Suzuki, H.

Terakawa, A.

Fujita, M.

Okamura, H.

Shinozuka, T.

Orihara, H.

Tohoku University Repository (TOUR) / 東北大学機関リポジトリ

Beam-bunching System for the K=110 AVFCyclotron at CYRIC著者 Suzuki  H., Terakawa  A., Fujita  M., Okamura H., Shinozuka  T., Orihara  H.journal orpublication titleCYRIC annual reportvolume 2003page range 33-35year 2003URL http://hdl.handle.net/10097/50225    33CYRIC Annual Report 2003    II. 4.  Beam-bunching System for the K=110 AVF Cyclotron at CYRIC    Suzuki H., Terakawa A., Fujita M., Okamura H., Shinozuka T., and Orihara H.*  Cyclotron and Radioisotope Center, Tohoku University Department of Electronic Engineering, Tohoku Institute of Technology*     A beam-bunching system has been constructed and installed in the beam injection line of the K=110 AVF cyclotron at CYRIC to provide a higher intensity beam for the regular experiments.  Before injection of beams into the cyclotron, the beam-buncher generates a pulsed beam from a direct current beam from the external ion source by means of the periodical acceleration and deceleration technique with electric RF field.  Beam pulses after the beam-buncher match with the RF phase acceptance of the cyclotron.   Figure 1 shows a schematic drawing of the beam-buncher.  It is located at the position of 1.8-m downstream from the median plane of the cyclotron.  Acceleration and deceleration gap is a single-type one, consisting of two parallel ring-electrodes made of oxygen-free copper (OFC) sheet.  They are insulted with ceramic called Macor.  The aperture and gap of the electrodes are 60 mm and 4 mm, respectively.  A transversely uniform electric field is generated with hexagonal meshes attached to the ring electrodes.  The beam-buncher includes a matching transformer (1:9) and a 450 Ω resister connected to the electrode.  Figure 2 shows the block diagram of the RF voltage for the buncher.  One of the two electrodes is excited by a sawtooth-like RF voltage (see Fig. 3) generated from sinusoidal RF signals with the fundamental and higher frequencies up to the third harmonics. The input signal is provided from the low level RF system1) for the cyclotron.  The amplitude and phase of the fundamental RF are stabilized with a feedback loop.  The output signal amplified by a 500 W solid-state amplifier is sent to the beam-buncher. The control system has been built using programmable logic controllers 2).    Specifications of the bunching system are listed in Table 1.  The performance for the beam-buncher is summarized in Table 2.  The typical gain in the beam intensity ranges     34from 2.3 up to 5.2.    The authors would like to thank Yokoi at NEC TOKIN CO. LTD. and Ohashi at THAMWAY CO. LTD. for technical support during the construction.  Thanks are also due to Goto, Ikegami and Kamigaito at RIKEN for fruitful discussions about the design of the beam-buncher.    References  1)  Tanigaki M. et al., CYRIC Annual Report 2000, p22. 2)  Yokogawa Electric Corporation, Musashino, Tokyo 180-8750, Japan.     (http://www.yokogawa.co.jp).   Table 1.  Specifications of the beam buncher. Fundamental input frequency  10.5-22MHz Fundamental Input level +10dBm Output voltage (max). 1200Vp-p Load impedance 450 Ω Voltage stability < 1% Phase shift 0-400 Phase stability   <1  Table 2.  Performance of the beam buncher.  Ion   Energy    [MeV]   Frequency   [MHz]  Harmonics Gain 1H+ 65 18.92 1 5.2 2H+ 40 21.02 2 4.7 4He2+ 50 16.77 2 3.9 14N3+ 44 12.80 3 2.3  Fig. 1.  The design of the beam buncher.  The upper electrode (on the side of the cyclotron) is excited by the RF.     35load(buncher)RF amp.combinerATTATT        2fphase shifter        3fphase shifter2f, 3f generator1fAGCfilter        1fphase shifterRF inmonitor1f APC and AGCfrequency multipliercombiner/dividerLO in30 mcoaxial cable  Fig. 2.  The block diagram of the RF system for the beam-buncher.       Fig. 3.  A monitor signal from the electrode.    

Beam-bunching System for the K=110 AVF Cyclotron at CYRIC

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Beam-bunching System for the K=110 AVF Cyclotron at CYRIC

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