New fabrication techniques for PASS

The Planar Array of Superheated Superconductors was introduced by the UBC group in 1990. It is a regular array of micron-sized spheres of indium or tin that acts as a detector of radiation or particles in a similar fashion to the Superheated Superconducting Granule Detector. Over the years, it was demonstrated that this device exhibited good energy sensitivity, a narrow spread of individual transition temperatures, position sensitivity, and, using line geometry, partial avalanche effects. The great difficulty, however, was to produce a detector of sufficient size. We discuss three possible approaches to this problem. The first method is to fabricate the array photolithographically in much the same way as before, but on a much larger scale. The second way is to emboss squares in a metal film with an ultrafine cutting tool before melting. The third technique involves depositing the metal on to a structured surface then melting. Some experimental tests are described.