“~ waves are reflected or absorbed by shielding materials and shapes may lead to better protection of valuable instruments used to record effects of detonations. An improved high-speed cathode ray oscilloscope for measuring gamma radiation in the early stages of a detonation has been developed by EG&G engineers and is being used for the first time in Operation Plumbbob, The instrument is like those used in past series except that it can record reactions within the range of less than a ten billionth of a second. i The oscilloscope is positioned in an instrumentation bunker where it can be shielded from the effects of the detonation, It consists of a long narrow tube working on the same principle as those used in television sets, The instrument receives its signal from a detector which may be located within a few feet of the nuclear device, and which relays its signal electrically by cable to the oscilloscope. Even though the detector is destroyed by the detonation, the signal already will have been transmitted and will reach the recording instrument. The newly improved oscilloscope can record events of extremely brief duration because it has greater capacity to intensify a weak electrical signal and cause it to flash brightly across the screen, There it is photographed by a pre-set camera with open shutter so a permanent record can be obtained. EG&G engineers and technicians also have developed for use in ballocn detonations in the series a light-weight firing rack, or "zero rack," which is a modification of a device that has been used in past series for tower shots. The rack, somewhat similar to an electrical switchboard in purpose, contains electrical controls and connections necessary for furnishing power for initiating associated experiments and for detonating the nuclear device. Racks used on towers contain heavy batteries for power, and weigh something like 300 pounds, The newly developed rack has no batteries, and through use of design changes such as smaller components and lighter metals, its total weight has been reduced to about OW q Lar] : 2 = - 38 - ty + 2 4 45 pounds.