Katsuhiko Sunako

High-efficiency operation of chemical oxygen-iodine laser using nitrogen as buffer gas

High-efficiency operation of supersonic chemical oxygen-iodine laser (COIL) with an advanced jet-type singlet oxygen generator using nitrogen as buffer gas was demonstrated. Laser output was remarkably increased when buffer gas was cooled with liquid nitrogen. The effects of buffer gas temperature on the characteristics of the oxygen-iodine laser medium was discussed. A net chemical efficiency of 23.4% was obtained at 405 W when the chlorine molar flow rate was 19 mmol/s.

An ion source with plasma generator

Abstract A small plasma generator has been developed using the same principle of plasma production as the Nagoya University TP-D machine in order to make an electron emitter with long lifetime for the ion source used in ion implantation and deposition techniques. The highly ionized and high density plasma flowing from the generator can be used instead of the tungsten filament of the Freeman type ion source. This paper reports the noteworthy ability of a flowing plasma to ionize a gas fed into the main discharge chamber whose ionization potential is lower than that of gas in the plasma generator. Also, the possibility of practical use as an ion source having a long lifetime is reported.

Simple hollow cathode ion source

Abstract A simple hollow cathode ion source has been developed and investigated for increasing ion source lifetime and beam current capability. The experimental results of a LaB6 cathode show that a plasma density of up to 1012/cm3 can be generated with a discharge current of 4.0 A and a pressure of 6.7 Pa, resulting in extracted ion beams that are extremely quiet and stable. The ions of non-volatile elements of cathode materials can be easily obtained by virtue of the sputtering effect of a SUS cathode. The lifetime of our ion sources can be shown to be more than 150 hours.

A concept for isotope separation in a sheet plasma by using ion cyclotron resonance heating

Abstract The concept of a novel method for separation of isotopes, the sheet plasma method, is described. A unique feature of this method is to perform isotope separation in a special kind of magnetized plasma: a sheet plasma: ions of a desired isotopic species in this plasma are selectively energized by ion cyclotron resonance heating. Owing to the unique characteristics of sheet plasmas — (i) the guiding centers of all gyrating ions he in the vicinity of the midplane of a plasma and (ii) the plasma thickness is as thin as twice the mean ion Larmor radius — extremely efficient separation of isotopes is possible.

Production of sheet plasma using a TP-D plasma source

Abstract This is a report on a method of sheet plasma production using a TP-D plasma source, which includes a detailed description of the machine. A sheet plasma is a magnetized plasma whose thickness is approximately equal to the mean ion cyclotron diameter. By this method it is possible to produce a steady-state sheet plasma characterized by its large density, high degree of ionization, and high spatial uniformity. The major conditions required for ensuring the proper operation for the machine are (1) to keep the working gas pressure high so far as circumstances permit, (2) to confine the discharge to extending only over the path between the cathode and the rim of the anode slit, (3) to prevent ions attracted to the cathode from concentrating in a limited area of the cathode, and (4) to accumplish coincidence of the central axis of the discharge path through the anode and floating-electrode system and the axis of the magnetic field. In an argon sheet plasma produced by this method, we obtained an electron temperature of about 10 eV and an electron density of the order of 10 12 cm −3 for discharge currents in the range of 5 to 20 A. It has been confirmed that the sheet plasma can be regarded as a very thin boundary-like plasma, in which the plasma space potential is far lower around the midplane of the plasma than on the boundary and a sharp potential well is formed.

Two-Dimensional Simulation of and Experiments on the Forward-Backward Modes Coupled Unstable Resonator

A new type of laser resonator, the forward-mode and backward-mode coupled unstable resonator, was two-dimensionally analyzed using a partially coherent input field. Under the optimum output power condition, the oscillating mode was annular even at the far field. The experiments with transverse electric atmospheric (TEA) CO2 laser qualitatively showed the same results as those calculated.

Isotope separation in a magnetized sheet plasma by ion cyclotron resonance

Abstract The isotope separation experiment in a sheet plasma has been studied by using ion cyclotron resonance heating. The sheet plasma flowed into two parallel plate electrodes to which an rf electric field with a frequency equal to an ion cyclotron for the desired isotopic species was applied. The observed resonance frequency is 180 kHz, however, the ion cyclotron frequency of Ar ion is 65 kHz. This discrepancy may be explained in terms of plasma space potential in the sheet plasma. The ion saturation current in a Langmuir probe gives a maximum value of 6.7 V/cm and 2.3 kG.

Production, characteristics and some applications of sheet plasmas

Abstract A strongly magnetized slab plasma with a thickness as thin as the mean ion Larmor diameter, or a sheet plasma, has been successfully produced using a TP-D type plasma source with rectangular magnetic coils and discharge electrodes. The technique of sheet plasma production is described in detail. Applications of sheet plasmas to various fields of science and technology are listed.

Off-Axis Confocal Unstable Resonator for Large-Bore High-Power Laser Chemical Pumped Oxygen–Iodine Energy Transfer Laser

An exotic resonator called the off-axis confocal unstable resonator is analyzed for large-bore low-gain high-saturation-intensity high-power lasers such as chemical pumped oxygen–iodine energy transfer laser (COIL), for which suitable resonators with high beam quality have not existed until now. The result of the calculations clearly showed that the off-axis confocal unstable resonator could produce multi-kW output with excellent beam quality for COIL.

A characteristic analysis of laser resonators

Some resonators were two-dimensionally analyzed zed using a partially coherent input field. The calculation based on the Fresnel-Kirchhoff integral formula showed the applicability of new type resonators to high-power and high-quality laser.