Formation of a Diffractional Grating by Magnetic Lithograph
A new method to make an optical diffraction grating has been developed using the Bitter method. A periodic magnetic pattern like 0101 ... is written in a magnetic memory medium, and a magnetic fluid is used as magnetic toner to visualize this pattern. To enhance the contrast of the grating, an interfacial active agent in the magnetic fluid is destroyed by a certain organic solvent, and a DC magnetic bias field is applied to the memory medium to thicken the pattern. When a transparent grating is required, Au film is deposited on it as a parting agent after the formation of a magnetic toner pattern. After separation of the epoxy resin film from the memory medium, Au film is chemically etched. A sharp diffraction image is observed by projecting a laser diode onto the diffraction grating. Using this method, an optical grating can easily be made even on a convex or concave surface.
Point source diffraction and its use in an encoder.
Diffraction from a point light source (a laser diode) was studied. The diffraction images were found to be magnified without using a lens and to move corresponding to the displacement of the slit aperture. A digital encoder using this diffraction is proposed to obtain very high resolution without a lens.
Magnetic plasma confinement for laser ion source.
A laser ion source (LIS) can easily provide a high current beam. However, it has been difficult to obtain a longer beam pulse while keeping a high current. On occasion, longer beam pulses are required by certain applications. For example, more than 10 micros of beam pulse is required for injecting highly charged beams to a large sized synchrotron. To extend beam pulse width, a solenoid field was applied at the drift space of the LIS at Brookhaven National Laboratory. The solenoid field suppressed the diverging angle of the expanding plasma and the beam pulse was widened. Also, it was observed that the plasma state was conserved after passing through a few hundred gauss of the 480 mm length solenoid field.