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cyclotron have already been reported,*^,3) we need to measure characteristics using penetrated higher energy beam which can be partly simulated to cos-mic rays. We here report performances of the PSDs for penetrated heavy ions, using RIKEN Ring

Cyclotron. The detector array shown in Fig. 1 was irradiated with an Ar-beam of 95 MeV/u. This detector array basically simulates the flight model assembly, but has smali number of signals because of the limits of the number of hvbrid-IC. Different from flight models, four signals from the third PSD are connected to one signal to get energy informa-tion only. We used no vacuum chamber to set the telescope, but lead a beam to the atmosphere through a 250 micron thick mylar window from the vacuum system. The distance from the window to the telescope was about 30 cm.

The signal Processing system including analog and digital circuits is shown in Fig. 2 for the flight model. The pulse shaping time of the main amplifier is 10 pis. In this experiment, we simulated the digital Processing part after the ADCs (telemetry part of the satellite system) by another circuit. These digital circuits have essentially no important role for the resolution of the telescope. We used two 50-m long glass fiber cables to transmit and receive signals from the beam point to the control room located just under the E-l beam site. We used a personal Computer with magneto-optical-disk to control ther telescope and to take data in the control room.

In front of the first PSD, we placed a 3-mm thick brass collimator with 1-mm (p holes on the 13 x 13 lattice points at 5 mm intervals. Since the rangę of the Ar-beam in brass is much less than 3 mm, only ions passing through the holes can hit PSDs.

In Fig. 3 we show an example of the positions observed corresponding to each hole of the collimator. The positions were calculated by a simple equation shown in Ref. 2. Apparent non-uniformity of the total counts in each hole upon the whole area of PSD depends on the beam profiles during the data taking time period of about 5 hours. In Fig. 4 we illustrate the differences between the calculated position (curve fitted center of each hole) and the real position (center of the 1 mm cp hole) of the collimator with vectors. At the lattice points where

Fig. 3. Three dimensional expression of the position data behind the collimator as described in the text.

Fig. 4. Position defomiation distribution of one PSI). Each vector represents the difference between obtained position and real position of the collimator.

there are no vector counts were too Iow to be detected owing to beam profiles.

Figurę 4 indicates a generał shrink of positions toward the center of the detector. In order to ‘de-modulate’ the observed position data in space to correct values, we should carry out similar mea-surements with various beams.

References

1)    T. Kohno: Space Sci. Rev., 51, 185 (1989).

2)    T. Kohno et al.: RIKEN Accel. Próg. Rep., 21, 152 (1987).

3)    K. Munakata et al.: ibid., 22, 168 (1988).