Noriyosu Hayashizaki

Nd-YAG laser ion source for direct injection scheme

The feasibility of a “direct injection scheme” using Nd–yttritium–aluminum–garnet laser has been studied experimentally. The relationship between charge distribution and laser power density was measured. The obtained yield rate of C6+ was 46.8% at the peak current pulse with 1.6×1011 W/cm2 laser intensity. The current dependence of the distance from the target at this intensity was measured. The peak current of C6+ will be 60 mA with φ4.8 mm extraction aperture. It was found from the input beam condition simulation by the code PTEQ–HI that high current (from 12 to 28.6 mA) can be accelerated by the TIT–RFQ.

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.

In-situ characterization of free-volume holes in polymer thin films under controlled humidity conditions with an atmospheric positron probe microanalyzer

A pulsed, slow positron beam, with a diameter of 200 μm, was extracted into air through a thin SiN window of an atmospheric positron probe microanalyzer (PPMA), and used to measure the ortho-positronium lifetimes τ in polyvinyl alcohol and polycaprolactam sub-μm-thick films. By measuring the variation of τ as a function of relative humidity, the effect of water molecules on the hole sizes, deduced from τ, was examined for the films with consideration to the chain mobility. The results demonstrate the usefulness of the atmospheric PPMA to the in-situ characterization of nanoscopic holes in thin films under practical conditions.

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.

Slow Positron Beam Apparatus for Surface and Subsurface Analysis of Samples in Air

A technique for investigating atomic-scale defects and/or nanometer (sub-nanometer)-order pores near the surface of samples mounted in air (without vacuum) by positron annihilation spectroscopy (PAS) has been developed. The method relies on the extraction of slow positron beams from the vacuum chamber to air through a thin SiN membrane vacuum window. Using a positron beam with an injection energy of 2.6 keV and a vacuum window with a thickness of 30 nm, samples mounted in air can be investigated by PAS to a depth of ~100 nm.

Carbon beam acceleration using a simple injection method into an RFQ

Abstract For medium-heavy ions, a new injection method into a RFQ linac is proposed. Laser plasma is created by an intense pulsed laser system and directly injected into the RFQ without any focusing devices. This method may eliminate complex difficulties due to space-charge effects in the low-energy transport system. Using the TITech RFQ, a verification test has been performed. From the laser ablated carbon plasma, C 4+ and C 3+ beams were captured successfully and were accelerated to the designed energy of the RFQ. The observed total current of carbon beam reached 8 mA, which exceeded the designed current of the RFQ. This method can be easily applied to existing RFQs which are used in medical and industrial accelerator systems.

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 liquid-lithium film jet-flow for the target of 7Li(p,n)7Be reactions for BNCT

A feasibility study on liquid lithium target in the form of a flowing film was performed to evaluate its potential use as a neutron generation target of (7)Li(p,n)(7)Be reaction in BNCT. The target is a windowless-type flowing film on a concave wall. Its configuration was adapted for a proton beam which is 30mm in diameter and with energy and current of up to 3MeV and 20mA, respectively. The flowing film of liquid lithium was 0.6mm in thickness, 50mm in width and 50mm in length. The shapes of the nozzle and concave back wall, which create a stable flowing film jet, were decided based on water experiments. A lithium hydrodynamic experiment was performed to observe the stability of liquid lithium flow behavior. The flowing film of liquid lithium was found to be feasible at temperatures below the liquid lithium boiling saturation of 342°C at the surface pressure of 1×10(-3)Pa. Using a proto-type liquid lithium-circulating loop for BNCT, the stability of the film flow was confirmed for velocities up to 30m/s at 220°C and 250°C in vacuum at a pressure lower than 10(-3) Pa. It is expected that for practical use, a flowing liquid lithium target of a windowless type can solve the problem of radiation damage and target cooling.