thing. This wae an older cyclotron, It happens to be -=- this is in no sense a refleotion on the cyclotron or its operators but it 1s more or less typical, This is a gmail cyclotron at the Sloan Laboratory at Yale University and right where the stone is in this picture, the level wae of the order of 200 neutrons per square centimeters per second, This happens to be a sidewalk outside the cycloe tron building, This situation has also since be rectified, ° May I have the next slide, please? Thia photoctraph is not that of some prehistoric monument. It is thrown in to represent the economic problem in the shielding against fast neutrons originating at a high energy, particularly a high energy synchro-cyclotron site, This is a shielding wall at the University of Rochester and one should note the massiveness of this type of shield, An accurate survey must point out the permissible neutron flux within a reacone able value, otherwise one 1s going to go into