Hidenori Matsuzawa

High‐Tc superconducting lenses for relativistic electron beams

New types of focusing lenses for relativistic electron beams (REBs) are proposed, and preliminary experimental results are obtained. The principle of the lenses is as follows: When REBs are injected into the small apertures of cylindrical superconducting lenses, self‐magnetic fields of the REBs are perfectly confined in a region between the REBs and the wall of the lenses. The REBs are focused by those compressed fields. The superiority of superconducting lenses was shown using foilless REB diodes which were operated at 0.15‐Torr Ne and had high‐Tc , cylindrical superconductor anodes made of Y‐Ba‐Cu‐O compounds (axial lengths of 30 and 145 mm and an inner diameter of 20 mm). The focused REBs (0.8 kA, 270 keV, pulse widths of less than 5 ns) had main beam diameters less than 2 mm.

High Tc bulk superconductor wigglers

In the present letter, high Tc bulk superconductor wigglers were proposed as one of the novel applications of high Tc superconductor lenses (Supertrons). Their operation was also shown experimentally. The bismuth‐based bulk superconductor wiggler had sinusoidal surfaces with a period length of 35 mm and an amplitude of 2 mm. The wiggler deflected intense electron beams of 340 keV, 1 kA, and 10 ns of duration time with an amplitude of about 1.5 mm.

Focal Lengths of High-Tc Sintered Superconducting Lenses (Supertrons) for Intense Electron Beams

To determine the optimum dimensions of high-critical-temperature (T c) sintered superconducting lenses (Supertrons), we observed intense electron beams (~340 keV, ~1 kA, ~10 ns) which were focused using axial-length-variable Bi(2223)-based lenses, with a Faraday cup at the exit of the lenses. The lens pipes examined were 13, 28, and 50 mm long and had a wall thickness of 1.5 mm and an inner diameter of 20 mm. Among the lenses, the 50-mm-long lens exhibited the best performance and was found to have the optimum dimensions by comparing the experimental results with electron trajectories simulated for single electrons injected in parallel to the axis of the lenses under a condition of space-charge neutralization. The simulation seems to be a useful method for designing Supertrons.

Experimental Corroboration for a Ferrite-Core Model of High-Tc Bulk Superconductor Lenses (Supertrons)

High-T c bulk superconductor lenses (Supertrons) for electron beams were operated over a temperature range from 65 to 130 K. The experimental results support a ferrite-core model of the lenses: Lenses for single short electron pulses are composed of fine grains of superconductors, as are ferrite cores. The lenses examined were Y-based 945°C and 750°C-sintered powder-pressed ones, an Y-based melt-processed one, a Bi-based 850°C-sintered powder-pressed one, and copper-block-made and copper-powder-pressed ones. Both the Bi-based and the Y-based 750°C-sintered lenses realized thinner electron beams ( ~340 keV, ~10 ns, ~1.4 kA) with decreasing operation temperatures, especially below their T cs. The copper-powder pressed lens also worked better with falling temperatures, but was inferior to the Bi-based lens. These behaviors are understandable in view of the similarity in operation between ferrite cores and Supertrons.

Delayed expansions and ionization instabilities observed in the current decay phase of a SF6 spark discharge

In SF6 gas at 5–30 Torr, self‐breakdown spark discharges starting in a constricted phase expanded spatially when the discharge current decayed to a critical value. The strength of the electric field increased from 400 to 2×103 Td in E/N, where 1 Td=10−21 V m2, where E is the electric field and N is the neutral gas number density. At the same time, the optical emission from the spark increased in strength and ionization instabilities started to grow. In the decay phase of SF6 spark discharge, negative ions strongly enhanced electron diffusion in the multipolar diffusion that resulted in the expansion and the excitation of ionization instabilities.

Supertrons : high-Tc superconducting tube lenses for electron beams : a double-layered tube

Abstract As one of the lenses for focusing and guiding electron beams, high-Tc superconducting tube lenses (Supertrons) have been developed. The lenses focus electron beams with the confined self-magnetic fields of the beams themselves. In this paper, our previous proposal was experimentally confirmed for intense pulsed electron beams (∼340 keV, ∼1 kA, ∼10 ns), so that a double-layered tube consisting of an inner Bi-based sintered pipe and an outer Y-based melt-processed pipe is able to focus all types of electron beams ranging from continuous to single pulsed currents. Furthermore, the double-layered tube easily generated short electron pulses with a duration of 1.5 ns at 80 K. From a model for the pulse compression, a modified double-layered tube was proposed, which probably generates subnanosecond electron pulses.

Double-Layered High-Tc Superconducting Tube Lenses (Supertrons) for Electron Beams.

A double-layered superconducting tube lens (supertron), which was previously proposed for focusing and guiding electron beams of single short-pulsed to continuous currents, functioned properly for single pulsed electron beams (~340 keV, ~1 kA, ~10 ns). The prepared tube consisted of an inner 1.5-mm-thick bismuth (Bi)-based sintered pipe and an outer 1-mm-thick yttrium (Y)-based melt-processed pipe, of a 17-mm innermost diameter and a 55-mm total length. Operating characteristics of the tube resembled those of single Bi-based sintered tubes, and differed from those of single copper and Y-based melt-processed tubes. These experimental results can be explained by a ferrite-core model. Diffusion (penetration) velocities of magnetic fields through the tube-wall materials were of the order of 104 m/s. In addition, the tube readily compressed electron pulses to those with a full-width at half-maximum of ~1.5 ns.

Some properties of the world crystal in fractal spacetime theory.

We prove that the wave-particle duality, inertia and the Heisenberg uncertainty relation are properties of a fractal spacetime, self-structured by a gravitomagnetic background field, in the world crystal.

Cascaded High-Tc Bulk Superconductor Lenses (Supertrons) for Intense Electron Beams

Two-stage tubular lenses (Supertrons) focused and transported intense electron beams (~2 kA, ~340 keV , ~10 ns) for lens separation of ~17 mm or less. In this range the second lens focused electron beams whose angle of incidence with the axis of the lens was less than the critical value of ~34°. The first and second lenses were 40 and 13 mm long, respectively, with an inner diameter of 20 mm and a wall thickness of ~1.5 mm. The lenses were made from Bi-based powder-pressed materials. Neon gas was introduced into the diode gap and into the bore of the lenses at pressures on the order of 0.1 Torr. The experimental results suggest that adjacent lenses should be positioned closer than the value of their inner diameter, and are each sufficiently long in the axial direction if longer than the value of their radii.

1‐ns pulse‐generating, compact, low‐pressure N2 lasers

Effects of a pressurized spark switch on N2 laser output have been observed optically with quartz fibers. The output power increased with decreasing the gap of the spark switch while keeping pgd=0.51 kg/cm (pg is the N2 gas pressure in the spark switch and d is the gap distance) and pN2=40 Torr (pN2 is the pressure of the laser medium gas). One nanosecond pulses with peak powers of 120 kW have been generated for the first time for low‐pressure operating N2 lasers.