M. Okamura

Acceleration of high current fully stripped carbon ion beam by direct injection scheme

Acceleration of a 17mA, 100keV∕u C6+ ion beam has been successfully achieved with an radio frequency quadrupole (RFQ) linac by means of “direct injection scheme.” The C6+ beam produced by a laser ion source with a Nd:YAG laser was injected to the high current RFQ linac. It has been experimentally proved that the fully stripped carbon ion beam with a current more than 10mA was accelerated by the RFQ linac.

High current carbon beam production with direct plasma injection scheme

We have been studying a new heavy-ion production technique called “direct plasma injection scheme,” DPIS, since 2000. A new radio frequency quadrupole (RFQ) designed especially for the DPIS was commissioned in 2004 and very intense carbon beam was successfully obtained, reaching more than 60mA accelerated current from the RFQ. Most of the contents of the accelerated beam was carbon 4+ as verified by beam analysis.

Design and construction of heavy ion RFQ linac with effective acceleration structure

Abstract At the Tokyo Institute of Technology, generating a plasma with a heavy ion beam has been studied for basic research on inertial fusion and a heavy-ion pumped laser. These experiments require a high intensity and high brightness beam. An 80 MHz heavy-ion RFQ linac is being constructed to meet the requirements. This linac accelerates particles with a charge to mass ratio ( q A ) greater than 1 16 from 5 keV/amu up to 214 keV/amu. Two-dimensional (2D) machining is applied for cutting of the RFQ vane-tips. We simulated the beam optics including effects of higher order harmonies in the intervane potential (H. Deitinghoff, A. Schempp, H. Klein and O. Pan, Particle Acc. 37–38 (1992) 47; Chen Chia-Erh, Fang Jia-Xun, Li Weigo, Pan Oujia, Lu Yuanrong, Li Deshan, Wang Lishan, Yu Maolin, H. Deitinghoff, A. Schempp and H. Klein, Proc. European Particle Acc. Conf. (1992) p. 1328) for optimization of the vane parameters. In order to increase the acceleration efficiency, synchronous phase was gradually raised from −30° to −20° in the accelerator section of the cavity. The expected beam transmission is 91.8% for a beam current of 0 mA and 68.4% for 10 mA.

Development of heavy ion IHQ linac for material irradiation

Abstract We have studied an Interdigital-H type Quadrupole (IHQ) linac structure for application in heavy ion irradiation. It is possible to vary the output energy by changing the voltage between gaps only. The calculated results show that the output energy can be varied from 30 keV/amu (0.48 MeV for 16 O + ) to 100 keV/amu (1.6 MeV). The operating frequency is 30 MHz and the synchronous phase is −30° with the exception of −90° at the first gap that works as a bunching section. The cavity length and diameter are 1.04 and 2.00 m, respectively.

Acceleration test of 3.2 MeV deuteron IH linac for production of useful radio-isotopes

Abstract We are studying an IH (Interdigital-H) type linear accelerator for application as part of the international cooperative research. Acceleration of deuteron and triton by the IH linac were planned for the production of useful radio-isotopes. The plan is to accelerate deuteron to 3.2 MeV by an IH linac for PET (positron-emission tomography) application. The linac was designed to accelerate deuterons from 0.2 MeV to 3.2 MeV by TUM and TIT. The accelerator cavity was manufactured in Romania. The beam-test facility was constructed at the Research Laboratory for Nuclear Reactors, TIT. The linac has successfully accelerated the proton beam. The shunt impedance was estimated to be about 370 MΩ/m by experiment.

Analysis of laser-produced heavy ions for direct plasma injection scheme

To accelerate highly charged intense ion beam, we have developed the direct plasma injection scheme (DPIS) with laser ion source. In this scheme an ion beam from a laser ion source is injected directly to a radio frequency quadrupole (RFQ) linac without a low energy beam transport (LEBT) line and then beam losses in the LEBT can be avoided. We achieved high current acceleration of carbon ions (60mA) by DPIS with the RFQ specially designed for high current heavy ions. As the next step we will use heavier elements such as Al, Fe, and Ta as targets in laser ion source (using high power laser, for example, glass laser) for DPIS and will examine properties of laser-produced plasma for highly charged ion production.

Acceleration test of heavy ion RFQ linac at TIT

Abstract An 80 MHz heavy ion RFQ linac at Tokyo Institute of Technology (TIT) has been constructed for research on inertial fusion and plasma experiments. Equipment for beam acceleration has been fabricated and assembled to confirm the performance with low currents of the RFQ. The linac successfully accelerated He + and C 2+ ion beams to their final energies of 219 keV/u. The obtained beam transmission was more than 89% with currents of a few tens μA.

Study of a four hole ECR ion source for a HIF injector

Abstract We have designed an ECR ion source which extracts four equal beams from one chamber as a study of an ion source for an accelerator that has several RFQ channels in one accelerating cavity for a heavy ion, HIF accelerator. Solenoid coils for the mirror magnetic field were designed using the magnetic field calculation program OPERA. Extraction electrodes were designed by using particle orbital calculation program FUGUN. Based on the above, we designed and manufactured four hole ECR ion source.

Ion generation from a solidified Ne target for a laser ion source

Laser plasmas from solidified neon on a cold surface were investigated for a laser ion source application. A Nd:YAG laser could generate Ne ions with a charge state up to 6+. The ion current density reached about 1.2mA∕cm2 at 2.3m from the target. The approach is applicable for the most of gas species with at least 1Hz operation.

A study of a test APF-IH type linac as an injector for cancer therapy

Abstract We are studying a heavy-ion interdigital H (IH) type linear accelerator as an injector for a cancer therapy synchrotron. The compact IH linac accelerates C 4+ ions from 65 keV/u up to 6 MeV/u with an alternating phase focus (APF) structure. The linac cavity is 3.1 m in length and operates at a frequency of 100 MHz. A test APF-IH linac was designed to accelerate C 4+ ions from 40 keV/u to 2 MeV/u with an operating frequency of 100 MHz. From particle orbit calculations, using an energy width of ±0.2%, this linac can accept a transverse emittance of 100 πxa0mmxa0mrad, a longitudinal phase of 35° and a beam intensity of several 100 μA. The test cavity has 1.4 m in length and 56 cm in diameter. We made a basic, half-scale model cavity of this linac and plan to measure its RF characteristics. Using the results of these measurements, a final design of this linac will be determined.