Yoshiharu Ishibashi

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.

Focusing of Intense Electron Beams with Novel High-Tc Superconducting Lenses

In this study, photographs were taken which definitely showed the focusing ability of superconducting lenses (Supertrons). High-Tc Bi- and Y-compound superconducting lenses with an inner diam of about 20 mm focused relativistic electron beams (REBs, 310 keV, 3.8 kA, with a duration time of less than 5 ns) to a diameter of 2.6 and 4.5 mm, respectively, at the exit of the lenses.

Profiles of Relativistic Electron Beams Focused with High-Temperature Superconducting Lenses (Supertrons)

Relativistic electron beams (REBs, 310 keV, 1.5 to 3.8 kA, pulse widths of about 5 ns) were focused with high-temperature Bi- and Y-compound, straight and tapered superconducting lenses (Supertrons, inner diameters of 5, 10, and 20 mm, thickness of 1.5 mm, and axial length of 40 mm) to diameters of 2 mm or less (full width at half maximum). The gently tapered Bi-compound lens showed the highest functioning in focusing REBs with current density of more than 400 A/mm2. Radial profiles of the REBs focused were visually confirmed with open-shutter photographs of fluorescence of neon gases excited by the REBs. A bent superconducting tube guided REBs as optical fibers do. To rate the focusing ability of these lenses, a figure of merit was proposed.

High-Temperature Superconducting Tl-Ba-Ca-Cu-O Lenses for Relativistic Electron Beams

Thallium-compound bulk lenses have the highest ability to focus relativistic electron beams (REBs, 0.87 kA, duration time of some nanoseconds) among the high-temperature superconducting Y-, Bi-, and Tl-compound bulk lenses (Supertrons). The REBs were focused to a diameter of less than 2 mm, the narrowest diameter ever achieved with Supertrons. The current densities on the beam axes were higher than 350 kA/mm2. A revised figure of merit was proposed to evaluate the superconducting lenses.

Jig for high‐Tc superconductor bulk wigglers

A jig is described that was used to form high Tc superconductor bulk wigglers (undulators) for intense electron beams. The wigglers are one of novel applications of Supertrons (lenses for charged particle beams) that were previously proposed and demonstrated by the authors.

Comparison between Powder-Pressed and Melt-Processed Bulk Superconductor Lenses (Supertrons) for Electron Beams

To confirm a model for operation of powder-pressed bulk superconductor lenses (Supertrons), Y-based quench-melt-growth (QMG) bulk superconductors were used to focus intense electron beams (340 keV, ~1 kA, and 5~10 ns). The lens focused the beams much less effectively than any of the Y-, Bi-, and Tl-based powder-pressed bulk lenses and even worse than a copper-made lens. These facts support the validity of the model in which powder-pressed bulk superconductors behave like ferrite cores at frequencies of some hundred MHz.

Observation of Supertron-Focused Electron Beams with a Streak Camera

Relativistic electron beams (REBs, 340 keV, about 1 kA, duration time of 5 ns) were focused in an atmosphere of 0.1-Torr neon gas with Supertrons which are bulk-superconductor-made lenses proposed by the authors. The spatial and temporal behavior of the focused REBs were observed with a conventional camera and with a streak camera (Hamamatsu C1578), respectively. The REBs were, surely, radially focused to diameters of less than 2 mm and seemed to be bunched in their axial direction with a time interval of 3 ns.

Comparison Y-, Bi-, and Tl-compound Bulk Lenses for Relativistic Electron Beams

Previously we proposed and demonstrated lenses (Supertrons) for intense electron beams (relativistic electron beams, REBs: 340 keV, 1 kA, duration time of some nanoseconds). In the present paper, the lenses made of Y-, Bi-, and Tl-compound bulks are compared as to their REB-focusing ability in terms of a figure of merit which we proposed. The Tl-compound lens showed the highest value of the figures among the lenses. These results are ascribed to the presumably highest intracurrent density of the Tl-compounds at their operation temperature (about 86 K).

Tapered Tube Lenses for Intense Electron Beams (Supertrons)

Supertrons, which were previously proposed and demonstrated to function as lenses for intense electron beams (310 keV, 1∿3 kA, a few nanosecond pulse widths), were experimentally evaluated in focusing ability for a tapered tube. The tube was made of Bi-compound and was 20 and 10 mm at the inlet and the exit, respectively, with an axial length of 31 mm. The electron beam focused was 1.7 kA and 2 mm in diam at the exit of the tube. The focusing ability of the tapered tube was better than those of straight tubes which were previously reported.