sae. 91 obtained by the slides which we will have run off for us shortly. This ehows the nucleus of our neutron instrumentation, To your left you see a FaillaeRosel Tissue Equivalent Chamber; to your right you see a carbon dioxide filled graphite walled Lonization chanber surrounded by aluminum and down below ~-- this is the Tissue Equivalent Chamber and thie is the carbon dioxide filled graphite chamber, (Indicating) These devices are used in cone junction with vibrating electrometers, This is a BF~3 long counter, a device for measuring specifically neutrons between thermal and roughly up to three with a flat flux kind of responce, This particular vhotograph was teken at the large proton "lineal" accele erator at the University of Minnesota at that time operating at forty MEV and they are going to have it back to their full capacity of sixty-eight NEV. Can I have the next slide, please. This represents one of the practical problem