Mitsutaka Kakeno

Electrical and optical properties of ion‐irradiated organic polymer Kapton H

An organic polymer Kapton H film was irradiated with high‐energy (∼MeV) N+2 ions. The specific resistivity of the film irradiated to a dose ∼1017 N/cm2 was estimated to be ∼10−2 Ω cm, which is about 20 orders of magnitude smaller than that of the unirradiated film. With increase of dose, the irradiated region of the film became grayish silver with a remarkable metallic luster. It is suggested that the alterations of the electrical and optical properties of the film result from the decomposition and the subsequent carbonization of the polymer induced by ion irradiation. The properties of the irradiated film are compared with those of the pyrolyzed one.

Characterisation of aluminium nitride layers formed directly by 700-800 keV 15N2+ implantation into aluminium

Accelerated 15N2+ ions were implanted into polycrystal and single-crystal, Al sheets with fluences of 8*1016-1.2*1018 N+ cm-2. The depth profiles of the implanted 15N were measured by 15N(p, alpha gamma )12C and 15N(p, alpha 0)12C nuclear reactions. A change in the depth profile of the implanted 15N significant recovery of the damaged Al lattice were not observed even after annealing above 400 degrees C over a wide range of implantation dose. In the case of low-dose implantation, channelling analysis combined with nuclear reaction analysis showed that the implanted 15N was located near the tetrahedral interstitial site in the FCC Al lattice, while for high-dose hot implantation ordered structures were not observed. Direct evidence for AlN formation was obtained by ESCA. Measurements of electrical capacitance and DC resistance for the 15N2+-implanted Al sheets were also performed.

Analysis of ion‐implanted surface and interface structures by computer‐simulated backscattering spectra

Computer codes for synthesizing random and channeling backscattering spectra have been elaborated to characterize the surface and interface structures formed or modified by ion implantation. Both effects of isotopes and energy fluctuation are taken into account in the spectrum simulation. This backscattering measurement combined with the simulation method is applied to characterization of the N+‐implanted Al films and to quantitative analysis of chemical reaction and interdiffusion induced by ion‐beam mixing. An ion‐beam‐induced damage profile and its epitaxial recovery of crystallinity are analyzed by the simulation of channeling spectra from ion‐implanted Al2O3 substrates.

Universal expressions for average projected range and average damage depth in ion-implanted substrates

Abstract Substrates of Al, Si, LiF, Al 2 O 3 , GaP, and GaAs were implanted with 45 to 420 keV N, Al, Ar, Mn, Ni, Zn, Te, and Xe ions. The reduced energies cover the range from 0.1 to 5. Depth distributions of implanted ions and displaced host atoms were determined by means of backscattering (including channeling) and nuclear resonance reaction measurements followed by computer-simulated spectrum analyses. The results are compared with other experimental data and theoretical predictions given by Gibbons et al. (GJM) and Winterbon et al. (WSS). For the latter theory, optimum WSS parameters are determined to give a good fit to the experimental data. It is concluded that reduced projected range and reduced damage depth are proportional to reduced energy but cannot be expressed by unified relations for all ion-substrate combinations. However, systematic investigation reveals that introduction of a new scaling coefficient gives two universal expressions for modified reduced projected range and modified reduced damage depth as a function of average reduced energy.

1 Hz fast-heating fusion driver HAMA pumped by a 10 J green diode-pumped solid-state laser

A Ti : sapphire laser HAMA pumped by a diode-pumped solid-state laser (DPSSL) is developed to enable a high-repetitive inertial confinement fusion (ICF) experiment to be conducted. To demonstrate a counter-irradiation fast-heating fusion scheme, a 3.8 J, 0.4 ns amplified chirped pulse is divided into four beams: two counter-irradiate a target with intensities of 6 × 1013 W cm−2, and the remaining two are pulse-compressed to 110 fs for heating the imploded target with intensities of 2 × 1017 W cm−2. HAMA contributed to the first demonstration by showing that a 10 J class DPSSL is adaptable to ICF experiments and succeeded in DD neutron generation in the repetition mode. Based on HAMA, we can design and develop an integrated repetitive ICF experiment machine by including target injection and tracking.

Study of phosphorus implantation in silicon by channeling and nuclear resonance techniques

Depth profiles of 31P implanted in Si were measured nondestructively by the 31P( p,γ)32S nuclear resonant reactions. It was observed that a large amount of the implanted 31P migrated to the front surface by annealing at 600 °C for 10 min and escaped from the surface by annealing at 800 °C for 10 min in a high vacuum. Channeling analysis revealed this phenomenon to be intimately related to thermal recovery of the damaged layer introduced by high‐dose implantation. The implantation dose and energy dependence of the distributions of lattice disorder was also measured by channeling methods.

Defect trapping of deuterium implanted in aluminium

The behaviour of deuterium implanted in Al was studied by the D(3He,p)4He and the D(d,p)T nuclear reactions. Changes of the depth profiles on the deuterium after heat treatments indicated that the implanted deuterium was trapped by the defect produced during the deuterium implantation and the release probability of the trapped deuterium increased as the specimen temperature was raised. Assuming a thermal equilibrium locally in the region of high defect concentration, the trapping energy of deuterium in Al was determined to be 0.12 eV. Since the release probability for the single crystal was considerably larger than that for the polycrystal specimens, the deuterium was considered to be strongly trapped in the grain boundaries. Distributions of displaced Al atoms and the recovery of the lattice damage by annealing were measured by the channelling technique.

Neutron Generator Using Spherical Targets on a Rotating Disk Irradiated with an Ultraintense Laser at 1.25 Hz

Abstract A neutron generator is developed using 1-mm-diam spherical deuterated polystyrene targets on a rotating disk irradiated with an ultrahigh-intensity (>1018 W/cm2) diode-pumped laser. It consists of a rotating disk supplier, the targets, and a control system to irradiate the targets at 1.25 Hz. We adjusted the laser focus and position on the target to obtain the maximum neutron yield.

Heavy ion CT reconstructed from range shift distribution measured by 2D detection system

An algorithm for heavy ion CT reconstruction from residual range measurement data is presented. The experimental procedure is described, in which an intensifying screen and a TV camera with a micro-channel-plate intensifier were used for the detection of energy deposition profile for the heavy ion /sup 12/C with an initial energy of 400 MeV/u emitted from a HIMAC. A series of projection images of a water phantom with PMMA pipes were experimentally taken for various values of range shifter thickness at each projection angle. From these images the distribution of residual range was obtained and used for reconstruction of the relative stopping power. The spatial resolution of the system was estimated as less than 2 mm.

Target Monitoring and Plasma Diagnosis using 2ω probe beam for CANDY

We have developed the shadowgraph and interferometer with second-harmonic of heating pulses laser to observe target and plasma in highly-repetitive fusion reaction experiments. In the deuterated polystyrene ((C8D8)n double foil experiment, we confirm implosion plasma and plasma collision. In target injection experiment at a 1 Hz rate, we measure the position of the flying deuterated polystyrene beads at the moment of laser pulse illumination and observe the plasma generation by counter-illumination by 0.63 J, 800 nm, and 104 fs laser pulses.