Effects of a dielectric material in an ion source on the ion beam current density and ion beam energy.
To understand a strong focusing phenomenon that occurs in a low-energy hydrogen ion beam, the electron temperature, the electron density, and the space potential in an ion source with cusped magnetic fields are measured before and after the transition to the focusing state using an electrostatic probe. The experimental results show that no significant changes are observed before or after the transition. However, we found unique phenomena that are characterized by the position of the electrostatic probe in the ion source chamber. Specifically, the extracted ion beam current density and energy are obviously enhanced in the case where the electrostatic probe, which is covered by a dielectric material, is placed close to an acceleration electrode.
Development of low-energy and high-current-density ion beam system.
A low-energy ion beam system operating at a dc voltage of less than 300 V was developed using an ion source with a multicusp magnetic field. A high-current-density ion beam of 6.9 mA∕cm(2) was successfully extracted at the electrode. The beam extraction characteristics for flat and concave electrodes were compared. In the case of a concave electrode with a designed focal length of 350 mm, it was observed that the beam profile was sharper than that obtained using a flat electrode.
Pioneer 10 Observations of the Ultraviolet Glow in the Vicinity of Jupiter
A two-channel ultraviolet photometer aboard Pioneer 10 has made several observations of the ultraviolet glow in the wavelength range from 170 to 1400 angstroms in the vicinity of Jupiter. Preliminary results indicate a Jovian hydrogen (1216 angstrom) glow with a brightness of about 1000 rayleighs and a helium (584 angstrom) glow with a brightness of about 10 to 20 rayleighs. In addition, Jupiter appears to have an extensive hydrogen torus surrounding it in the orbital plane of Io. The mean diameter of the torus is about equal to the diameter of the orbit of Io. Several observations of the Galilean satellites have also occurred but only a rather striking Io observation has been analyzed to date. If the observed Io glow is predominantly that of Lyman-α, the surface brightness is about 10,000 rayleighs.