Precision in spark localization in magnetostriction spark chambers

NUCLEAR INSTRUMENTS AND METHODS 52 (I967) 345-346; © NORTH-HOLLAND PUBLISHING CO.

P R E C I S I O N IN SPARK L O C A L I Z A T I O N IN M A G N E T O S T R I C T I O N SPARK C H A M B E R S G. GIANNELLI, B. MARANGELLI and M. RICCO Physics Institute of the University of Bari, INFN Section of Bari, GIFCO-Section of Bari, Italy Received 21 March 1967 The precision obtainable in the spark localization in magnetostrictive wire spark chambers is discussed. The measurements on the propagation of pulses in magneto-

strictive wires previously published are elaborated and it is shown that in these experiments the spark position was determined with a precision of +0.1 mm.

In the type of wire spark chambers in which the wires themselves of the chambers are of magnetostrictive material~), the coordinate of the spark in the direction of the wires is given from the time that the elastic pulse generated at the spark's position on the wire takes to arrive to a detector placed near one end of the wire. That is this coordinate is measured with continuity and it can be expected that high precisions can be attained. In a previous paper 2) we have reported on a series of experiments on the propagation on magnetostrictive wires of elastic pulses generated by sparks. In these experiments we have measured the time elapsed between the instant the spark breaks out and the instant of arrival of the elastic pulse to a detector

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and we have compared it with the distance between the two, so that they are in fact also experiments on the precision in the localization of the sparks. A first series of experiments was performed for two values of the distance between spark and detector: 20 measurements at 10 cm distance and 19 at 63 cm distance. In fig. 1 the distribution of the deviations from the mean values are plotted for both sets of measurements, together with the best fitting Gaussian distribution. The standard deviation results to be 16 nsec, that

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corresponds to 0.09 mm in the determination of the spark's position. Other series of experiments were performed, in each series the distance between spark and receiver was varied between I0 cm and 60 cm. Six series of measurements, each on a different wire, were performed for a total of 56 measurements. Fig. 7 of l) shows the results of one series of such measurements. In fig. 2 the distribution of the distances of the measured points from the best fit straight line of each series of measurements has been plotted, together with the best fitting Gaussian distribution. The standard deviation turns out to be of 0.15 mm for the error in the determination of the spark's position. In that second type of experiments there are two sources of error: one in the measurement of the

propagation time, like in the first experiment; the second is the error in the measurement of the distance between spark and detector. That distance was measured with a cathetometer with a precision of 0.1 mm. So the error in the propagation time, turns out to be 0.I mm, also in this set of experiments. That is in all those experiments the position of a spark on a magnetostrictive wire has been determined with a precision of 0.1 mm.

References 1) V. Barbanente, M. De Blasi, C. de Marzo, G. Giannelli, B. Marangelli and M. Ricco, IEEE Trans. Nucl. Sci. NS-12 (1966) 31. 2) G. Giannelli, B. Marangelli and M. Ricco, Nucl. Instr. and Meth. 47 (1967) 151.