K. Sasa

Conceptual design of compact heavy-ion inertial fusion driver with an r.f. LINAC with high acceleration rate

Abstract The interdigital-H-type (IH) linear accelerator (LINAC) is well known for its high shunt impedance at low and medium particle velocities. Therefore, it can be used to operate efficiently with a high acceleration gradient. The IH LINAC cavity is able to generate 10 MV m−1 (average acceleration gradient) with focusing of the particles by a superconducting solenoid and quadrupole. The LINAC can accelerate particles with a charge to mass ratio (q/A) greater than 1/250 from 0.3 MeV a.m.u.−. In a compact heavy-ion inertial fusion driver design, the total effective length of the IH LINAC cavities is about 1250 m.

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.

Compact IH-APF type linac for PIXE and RBS analyses

We studied an IH-APF type linac for PIXE and RBS analyses use. The compact (La 1.5 m) linac accelerates protons from 40 keV to 2.0 MeV. This alternating-phase-focus (APF) system cannot focus such a high intense beam, but a beam of several 100 lA is focused by the combination of Focus‐Defocus sequence. For PIXE and RBS analyses, intensity of bombard particles is several lA lower than several 100 lA. From particle orbit calculation, on energy width of a0.2%, this linac can accept transverse emittance of 113 pmm mrad, longitudinal phase of 35∞ (by using two bunchers, beam transmission gets larger than 80%) and beam intensity of several 100 lA. The linac can accelerate protons to 2.0 MeV by RF power of about 10 kW. We designed the interdigital H (IH) linear accelerator by particle-orbit calculation. All PIXE and RBS analyses systems occupy only 2 m · 3 m. A half-model cavity was designed. The model is being manufactured now for measurement of RF characteristics. ” 2000 Elsevier Science B.V. All rights reserved.

RF characteristics of IHQ linac for heavy ion implantation

Abstract At Tokyo Institute of Technology (TIT), an Interdigital-H type Quadrupole (IHQ) linac has been constructed for application in high energy heavy ion implantation. The linac can accelerate particles with charge to mass ratio greater than 1/16 from 0.24 MeV up to 1.6 MeV (for 16 O + ). As a result of the low power test, the resonant frequency is 36.26 MHz, the shunt impedance is 252 MΩ/m and therefore, the required power to accelerate 16 O + ion is 39.5 kW.

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.

Ion source of multiply charged C60 fullerene and fullerene linear accelerator

Production and acceleration system of multiply charged C60 and C70 fullerene ions are being designed for basic studies on cluster physics. Multiply charged fullerene ions are produced by electron impacts. Ions selected by the analyzing magnet are accelerated up to 100 kV through an acceleration column. The ion source generates C60+(8.4 nA), C602+(4.5 nA), C603+(1.6 nA). C60+, C602+, and C603+ are accelerated up to 100, 200, and 300 keV, respectively. The alternating phase focus (APF)-interdigital H-mode (IH) linac was designed to accelerate C60+ ion (e=1/720) and C70+ ion (e=1/840) from 0.2 to 3.2 keV/amu with an APF and an operation frequency of 10 MHz.

Compact IH-APF type linac for heavy ion implantation

Abstract An IHQ type linac for heavy ion implantation of TIT succeeded in acceleration of proton in end of March 1998. The IHQ cavity has short length (1 m), but has large diameter (2 m). The IHQ structure has necessarily long cell length for quadrupole fingertips. Therefore, acceleration frequency is low. Then, we contrived a new compact IH-linac with alternative-phase-focusing (APF) system which focuses beam by combination of focus–defocus sections alternately. APF structure is suitable to shorten cell length, and diameter of acceleration cavity can be reduced by high frequency. This linac can accelerate particles up to 100 keV/u for charge to mass ratio 1/16, with operation frequency of 70 MHz. A cold model in real scale was designed and manufactured for measurement of its RF characteristics. We studied tuning of gap-voltage by using cold model.

RFQ-Linac system for intense heavy ion beams and beam-target interaction experiments

An intense heavy ion linear accelerator system is being constructed for basic researches on HIF and heavy ion pumped laser at TIT. This accelerator system consists of an RFQ‐Linac, an ECR ion source, a fine‐focusing beam transport system and a fast beam pulsing system. By using this system, ion beams of 16O+ with currents of 7 mA and an energy of 3.5 MeV will be focused onto a small spot area of about 1 mm2. At present, the maximum beam current obtained from the TIT‐RFQ is 1.6 mA for 4He+. The overall status of this linac system and preliminary experiments with beams of 4He+ are discussed.

Fine-focusing system of intense beams for application of ion-induced plasma

Abstract For investigations of ion beam-induced plasmas we developed a fine-focusing system. An ion beam of 4He+ with an energy of 220 keV/amu after acceleration through an RFQ-Linac at TIT was focused onto a small spot area of about 1 mm2. This beam deposited a specific deposition power of about 0.17 GW/g to the target.