Seiji Takechi

Effects of Axial Magnetic Field and Faraday Shield on Characteristics of RF Produced Plasma Using Spiral Antenna

Influences of the axial magnetic field and Faraday shield on the performance of RF produced plasma using a spiral antenna are investigated. The RF power and filling pressure dependences, antenna-plasma coupling, Ar line intensities and spatial profiles of plasma parameters are studied. With the magnetic field and/or without a Faraday shield, the threshold input power for plasma initiation is lowered and the antenna-plasma coupling is improved. In addition, a collisionless heating mechanism is suggested. With the increase in the applied magnetic field, the ion saturation current increases and shows a peaked radial profile; in the low-pressure range it shows a nearly flat axial profile.

Comparison between two piezoelectric lead-zirconate-titanate detectors bombarded with high-energy xenon beam

The characteristics of piezoelectric lead–zirconate–titanate (PZT) detectors were studied by directly irradiating them with a 400 MeV/n Xe beam. The sensitivity of a multilayered detector was discussed in comparison with that of a monolayered detector. It was found that the sensitivity of the detectors depended on their structure.

Detection of high-energy heavy ions using piezoelectric lead zirconate titanate

The characteristics of a radiation detector fabricated with stacks of piezoelectric lead zirconate titanate (PZT) elements were studied by irradiating it with a 400 MeV/n xenon (Xe) beam for various beam pulse durations. This detector is referred to as the multilayered detector (MD). To understand the production mechanism behind the output voltage obtained from the MD, measurement of the spatial distribution of the output signals generated in the MD was attempted. It was found that the amplitude observed was dependent on the number of Xe ions per unit time and the amount of ionization loss energy of Xe ions in PZT.The characteristics of a radiation detector fabricated with stacks of piezoelectric lead zirconate titanate (PZT) elements were studied by irradiating it with a 400 MeV/n xenon (Xe) beam for various beam pulse durations. This detector is referred to as the multilayered detector (MD). To understand the production mechanism behind the output voltage obtained from the MD, measurement of the spatial distribution of the output signals generated in the MD was attempted. It was found that the amplitude observed was dependent on the number of Xe ions per unit time and the amount of ionization loss energy of Xe ions in PZT.

Electron Heating and Control of RF-Produced Plasma Parameters Excited by a Planar, Spiral Antenna

Electron heating in inductively coupled plasma with use of a planar, spiral antenna is investigated by measurement of the skin depth of evanescent waves and antenna-plasma coupling. It is shown that for plasma production, both a collisionless and a collisional heating mechanism play an important role in a wide range of collision frequencies. In addition, control of plasma parameters such as uniformity and density by adjustment of the antenna configuration and the external magnetic field is demonstrated.

Measurement of temperature after hypervelocity collision of microparticles in the range from 10 to 40 km/s

The temperature recorded immediately after hypervelocity collision of microparticles comprising iron and nickel with a silver-coated piezoelectric plate was analyzed using photomultipliers of different spectral response characteristics. The conversion rate between the velocity and temperature is estimated to be ∼900 K/km∕s in the velocity range of 10–40 km/s. This rate is greater than that reported earlier.

Study of the characteristics of a piezoelectric lead zirconate titanate radiation detector using a pulsed xenon source

The detector characteristics of piezoelectric lead zirconate titanate (PZT) were studied by directly irradiating a multilayered PZT detector with 400 MeV/n xenon ions. An extracted beam was processed with a rotating slit. Thus, passed through ∼103 xenon ions were available for 50 to 250 μs. The effect of polarization on the output signal was discussed, and the optimal electrode configuration was determined. The output signal appeared as an isolated pulse whose amplitude was qualitatively understood by the Bethe–Bloch formula. However, the calculated and the observed values differed depending on the rotation speed of the slit. A process that can explain the differences is presented here. The output signal appearing beyond the range of 400 MeV/n xenon ion beam was discussed. The sensitivity was compared with that obtained with hypervelocity collision of dust.

Dependence of thickness of lead zirconate titanate material used as radiation detector

The characteristics of a radiation detector fabricated with stacks of piezoelectric lead zirconate titanate (PZT) elements were studied by irradiation with a 400 MeV/n xenon (Xe) beam. The detector was designed to monitor the output voltage formed on the surface of each element. Three additional PZT elements were placed in front of the detector to increase the thickness of the PZT target. It seemed that the individual output voltage observed at a position beyond the range was dependent on the amount of strain generated by the ionization loss energy of Xe ions within the range.

Response of Lead Zirconate Titanate without Poling to High-Energy Heavy-Ion Beam

A radiation detector based on the piezoelectric effect, which is fabricated using lead zirconate titanate (PZT), has been investigated by irradiating it with a 400 MeV/n xenon (Xe) beam. To estimate quantitatively the electric charge appearing on the PZT detector, the detector made of PZT without poling was used in this study. It was found that the sensitivity of the detector without poling was reduced by ~1/20 compared with that of the detector with poling within the limits of the experimental conditions.

Position Sensitive Element for Hypervelocity Microparticles Using a Piezoelectric Plate

The propagation of transverse waves generated acoustically in a piezoelectric element by colliding it with hypervelocity microparticles was studied. The propagation times were measured by a set of multiple electrodes on the surface of the element. The coordinates that the particles struck were determined by combining the propagation times and the velocity of the waves. By using the position-sensitive element, significant deviations between the prior indicated and actually measured orbits were observed. The potential of the present element as part of a steering system is discussed.

Study of Deterioration in a Piezoelectric Lead Zirconate Titanate Radiation Detector through Measurement of the Electromechanical Coupling Factor with 400 MeV/n Zenon Ions

The variation of the electromechanical coupling factor (ECF) was measured by bombarding a piezoelectric lead zirconate titanate (PZT) element with 400 MeV/n xenon ions. The element was exposed to energies up to 104 J, during which time the ECF was observed by the resonance method. The ECF gradually decreased with the energy accumulated during irradiation, and its behavior was scaled with an empirical formula. This decrease suggests that the piezoelectric quality deteriorated; hence, the sensitivity of the PZT radiation detector was considered to be degraded as well. The variation ultimately originated in resonance-associated processes. A potential detector suitable for use in severe-radiation environments was discussed.