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A monitor for high-energy beams of charged particles utilizing the phenomenon of secondary emission is described. The primary beam to be monitored passes through a set of foils alternately phased in voltage. The current produced by secondary electrons ejected by the beam passage is collected onto the one set of foils and measured. Results of tests with high-energy electrons are given. The monitor gives no indication of saturation up to peak current densities of 16 rna/em', and is independent of the primary beam energy in the range over which the monitor was tested .

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Power transistors delivering 8-A pulses of 2-msec width are used to drive low impedance coils in Ross and Barksdale valves. Unijunction transistors and Thyristors are used to replace all relays and lamp flasher elements in compact, reliable alarm units of new design. Life tests equivalent to many years operation at accelerator sites have been carried out. There has not yet been any failure in operation.A system is described which provides a triggering signal for a scintillation or spark chamber from a coincidence circuit. Power is supplied to label the recording film with a register number and to advance the film to a clear position. Multiple exposures of events are prevented.