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We have tried to develop systems permitting the 4 GHz oscilloscope TSN 660 and the picosecond chronometer TSN 637/8 to be used for the measurement of the synchronism of several neodyne laser beams of 50 to 100ps iuration. The oscilloscope TSN 660 is a laboratory instrument having been specially designed for the observation and analysis of ultra-rapid phenomena. It is fitted with a cathoderay tube including a helicoidal-type wave propagation line permitting verywideband deviation (4 GHz). Its input impedance is 50 ohms and its sensitivity 3 V/cm. The CRT output stage includes a microchannel wafer (electron multiplier) having a 104 gain. Each electron entering a channel produces on the P11 type screen of size 40 x 40 mm2, a spot sufficiently luminous to be recorded on 3000 ASA Polar-oid photographic emulsion. The trace has a thickness of 100 microns (30 mV/trace) and the highest scanning speed is 100 ps/cm, the temporal resolution is 5 ps. The multi-chronometer TSN 637/8 is intended for the measurement of time intervals among eight non-repetitive electric signals, with high resolution. Self-calibration is ensured by a microprocessor using an internal thermo-stat-controlled time master. That micro-processor carries out the correction of the measurements and a number of statistical calculations. The chronomenter is associated with input discriminator modules specially designed for the shaping of the very narrow electric pulses. The following performances are obtained: measuring range 16 ns; resolution: 1 ps; input signals: 9; thresholds adjustable from 50 to 500 mV; minimum duration: 200 ps. The use of an oscilloscope TSN 660 and of two optoelectronic switches of the AUSTON type has enabled the teams of the CEA/Limeil to synchronize through permutation, to within 10 ps, the eight beams of their COTAL laser. In conditions of correct saturation of the detectors, the total jitter is approximately 15 ps, and by carrying out a pseudo-statistical measurement with 15 experiments, the typical deviation obtained is + 5 ps. We have carried out several types of tests with the aid of the chrono-meter TSN 637/8 and by using RTC XA1003 photocells having a rise time of 150 ps, the output signal of which has been widened by means of passive dividers. We have also used ACSTON type optoelectronic switches in place of the photocells.
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