To properly assess the "sensitivity" of explosives systems under impact conditions we must obtain detailed information on these mechanisms by which explosives are ignited by impact. It is necessary to know which impact conditions represent the greatest hazard to explosive materials, as well as to know for a given impact condition the relative responses of explosives of interest. I should like to describe to you a program sponsored jointly by the Department of Defense and the Atomic Energy Commission to attain this type of information. A wide variety of impact experiments have been conducted using geometrical arrangements of explosive, plastic, and metal which are relatively simple compared to complete ordnance systems. All of these tests have employed billets of explosive fabricated by standard production techniques, and the billets have been sufficiently large that ignition, once started, has something of the same opportunity to grow or decay as in full scale ordnance assemblies. From these relatively simple tests there has accrued much new useful information on the behavior of explosives under impact. With this new information providing a base from which to work, it is hoped that theoretical calculations on impact phenomena will in the future make a bigger contribution to …

In the course of modern physics research, the need frequently arises for storage of large quantities of electrical energy which can be periodically discharged at high peak power into a load. Until recently, the homopolar machine has been an intriguing device having considerable academic interest but little practical value. In recent years, successful machines have been developed to utilize liquid-metal brush systems. The liquid-metal brush overcomes all the problems associated with current collection power loss, frictional loss, and limiting peripheral velocity. Consequently, these machines are now worth serious consideration where high-current dc generation is required. The main purpose in setting up a homopolar generator test program was to establish the limits to which an essentially standard commercially available generator of this type could be pushed.

The principal types of particle accelerators are described briefly according to operation and history. Known operating particle accelerators are listed with their pertinent dimensions.

The development of high-energy charged particle accelerators such as the Bevatron and of improved nuclear-event detection devices such as the Berkeley 72-in. hydrogen bubble chamber has greatly increased the need for high-speed data reduction of nuclear events. Full exploitation of the potential of the 72-in. bubble chamber demands a very high-speed analysis system. This paper describes an approach to such a system.