Development of A Sintered Porous Neck Filter For Jt Cryo-Cooler

A built-in filter for a JT Cryo-cooler is a must to ensure its trouble free operation without being choked, by filtering all the gas contaminants, larger than 5μm size. The JT cooler is being developed at SSPL for cryo-cooling of a 320 × 254 IR FPA Detector. A suitable sintered porous neck filter of bronze material with 5μm pore size has been developed at NFTDC, Hyderabad. The said filters, on detailed inspection were found to be as per the desired specification. The average pore size of 5μm in the filter was confirmed from the optical micrographs as well as SEM images. Similarly the filter porosity of about 35% was confirmed by measuring its density using Archimedes water displacement method, after impregnating the filter by xylene. Thus, weighing the filter first in air and then in water leads to calculating the actual density of the filter. These filters were then assembled in the existing JT coolers, the trouble free operation of which, further confirmed the desired quality of these filters. This paper highlights the process development, characterization and evaluation of the filters.