Kota Torikai

Carbon Ion Radiotherapy at the Gunma University Heavy Ion Medical Center: New Facility Set-up

Carbon ion radiotherapy (C-ion RT) offers superior dose conformity in the treatment of deep-seated tumors compared with conventional X-ray therapy. In addition, carbon ion beams have a higher relative biological effectiveness compared with protons or X-ray beams. C-ion RT for the first patient at Gunma University Heavy Ion Medical Center (GHMC) was initiated in March of 2010. The major specifications of the facility were determined based on the experience of clinical treatments at the National Institute of Radiological Sciences (NIRS), with the size and cost being reduced to one-third of those at NIRS. The currently indicated sites of cancer treatment at GHMC are lung, prostate, head and neck, liver, rectum, bone and soft tissue. Between March 2010 and July 2011, a total of 177 patients were treated at GHMC although a total of 100 patients was the design specification during the period in considering the optimal machine performance. In the present article, we introduce the facility set-up of GHMC, including the facility design, treatment planning systems, and clinical preparations.

All-ion accelerators: An injector-free synchrotron

A medium-energy synchrotron capable of accelerating all-ion species is proposed. The accelerator employs a strong focusing lattice for ion-beam guiding and induction acceleration for acceleration and longitudinal capture, which is driven by a switching power supply. All ions, including cluster ions in their possible and arbitrary charge state, are accelerated in a single accelerator. Since the switching power supply employing solid-state switching elements is energized by a trigger signal, which is generated from a bunch monitor signal produced by a circulating ion bunch, the induction acceleration always synchronizes with the bunch circulation. This feature enables the realization of an almost injector-free synchrotron.

Switching power supply for induction accelerators

A new particle acceleration method using pulsed induction cells was introduced in the super-bunch project at KEK. Unlike conventional RF acceleration, this acceleration method separates functions of acceleration and confinement. As a result, this acceleration method is capable of accelerating a very long bunch of beam or a wide mass range of particles. However, it is necessary to give a very fast pulsed- excitation to the magnetic material to induce an electric field to accelerate particles. Switching power supplies of high voltage output with very fast pulse-operation is one of the most important key technologies for this new acceleration method. Features of switching power supply developed for induction synchrotron is reported. The 31 kW MOSFET switch performed 1 MHz continuous operation with 15 nsec rise time.

Three-dimensional and Multienergy Gamma-ray Simultaneous Imaging by Using a Si/CdTe Compton Camera

PURPOSE To develop a silicon (Si) and cadmium telluride (CdTe) imaging Compton camera for biomedical application on the basis of technologies used for astrophysical observation and to test its capacity to perform three-dimensional (3D) imaging. MATERIALS AND METHODS All animal experiments were performed according to the Animal Care and Experimentation Committee (Gunma University, Maebashi, Japan). Flourine 18 fluorodeoxyglucose (FDG), iodine 131 ((131)I) methylnorcholestenol, and gallium 67 ((67)Ga) citrate, separately compacted into micro tubes, were inserted subcutaneously into a Wistar rat, and the distribution of the radioisotope compounds was determined with 3D imaging by using the Compton camera after the rat was sacrificed (ex vivo model). In a separate experiment, indium 111((111)In) chloride and (131)I-methylnorcholestenol were injected into a rat intravenously, and copper 64 ((64)Cu) chloride was administered into the stomach orally just before imaging. The isotope distributions were determined with 3D imaging after sacrifice by means of the list-mode-expectation-maximizing-maximum-likelihood method. RESULTS The Si/CdTe Compton camera demonstrated its 3D multinuclear imaging capability by separating out the distributions of FDG, (131)I-methylnorcholestenol, and (67)Ga-citrate clearly in a test-tube-implanted ex vivo model. In the more physiologic model with tail vein injection prior to sacrifice, the distributions of (131)I-methylnorcholestenol and (64)Cu-chloride were demonstrated with 3D imaging, and the difference in distribution of the two isotopes was successfully imaged although the accumulation on the image of (111)In-chloride was difficult to visualize because of blurring at the low-energy region. CONCLUSION The Si/CdTe Compton camera clearly resolved the distribution of multiple isotopes in 3D imaging and simultaneously in the ex vivo model.

Induction System for a Proton Bunch Acceleration in Synchrotron

Recently the first induction acceleration of a single proton bunch of 2.3E10ppp was demonstrated [1], where it was accelerated from 500MeV to 8GeV in 1.9sec in KEK-PS. This paper describes the induction system for a synchrotron and a beam confinement experiment as a second step of the proof-of principle (PoP) experiments of a “induction synchrotron” [2], where a proton beam with a bunch length of 500ns was longitudinally confined by the induction barriers for 500msec, is introduced..

A POP experiment scenario of induction synchrotron at the KEK 12 GeV-PS

A scenario for the first POP experiment and crucial issues of accelerator operation with induction acceleration are discussed.

R&D works on 1MHz power modulator for induction synchrotron

A proof of principle experiment of an Induction Synchrotron is scheduled in 2003 at the KEK 12GeV-PS. Proton bunches are accelerated with a 10kV of rectangular shaped induction voltage. An accelerating system consists of four induction cavities capable of individually generating a 2.5kV of output voltage. Each cavity is driven by a solid-state power modulator, which is operated at a revolution frequency of 600-800 kHz. The modulator circuit consists of MOS-FETs as switching element. Uniformity in the voltage waveform is crucial for the stable acceleration. Ringing in the voltage waveform caused by coupling of self-inductance of circuit and output capacitance of MOS-FETs deteriorates the uniformity. With the help of circuit analysis and simulation method of minimizing the self-inductance has been developed. Ratio of numbers of MOS-FETs in series and in parallel which defines the total output capacitance is also important to design the power modulator circuit. Power loss in MOS-FET is also important for stable operation of the power modulator. By the circuit analysis, it is also found that the output capacitance contributes to the power loss.

Focusing-Free Transition Crossing in the RHIC Using Induction Acceleration

A feasibility of focusing-free transition crossing (FFTC) in the RHIC is discussed. The FFTC in a hybrid system combining a rf for the confinement and an induction accelerating system for the acceleration makes the bunch length kept sufficiently enough long to suppress e-cloud production or other undesired features, through crossing the transition energy.

Induction Acceleration of a Single RF Bunch in the KEK PS

Results of the induction acceleration of a single RF bunch in the KEK PS are reported.

Design study of 1MHz induction cavity for induction synchrotron

An induction cavity was designed for the POP experiment of induction synchrotron using the KEK 12 GeV PS. It must be operated at a repetition rate of 667-882 kHz for acceleration from the injection energy to the flat-top energy. Design issues include handling of heat deposit, minimization of voltage droop and coupling impedance, and tolerable jitter. Its Q-value on the cavity assembled following the design was obtained from the longitudinal coupling impedance measurement. Effects of the droop in the acceleration voltage on the synchrotron motion, which has been estimated from the circuit parameter measurement on R, C, and L, was analysed from a longitudinal beam dynamics point of view. The effect of the droop is given by the square of phase delay.