Munetaka Matoba

A new viewing theory on centroid finding for patterned position sensitive detectors (PPSD)

A study of a new viewing theory (surface viewing theory) on position sensing is described. The viewing that the infinite height cathode strips is based on it (linear viewing theory), limits the width of the readout channel to a severe narrow strip. Therefore, the number of channels for long length position sensing increases. The surface viewing theory, removes this limitation by shortening the heights and broadening the widths of the readout channels (cathode strips). In the surface viewing theory since the surface of the affected area is used for position determination, it is possible to broader sensing area comparing with the cathode strip, Preliminary designs and experiments show that the optimum sensing area (OPSA) based on the surface viewing theory decreases at least 10 times in number of the readout channels without any degradation in linearity comparing with the single cathode strip. Increasing the signal to noise ratio in sake of a better resolution is possible with vertical cascading of the OPSA. Two type combinations of the OPSA result in extended OPSAs that correspond to suitable patterns long length position sensitive detectors.

A novel ratio to digital converter (RDC)

A novel ratio-to-digital converter (RDC) that uses a new conversion method for its division circuit is introduced. The new ratio-to-time conversion used in the division circuit is a dynamic conversion method. The ratio-to-time response of a miniature delay chip is used in this dynamic conversion method. Majority of the methods used for the ratio-to-time conversion of conventional RDCs are static methods and start the conversion process after a long dead time for peak sensing of the signals. For the dynamic conversion method the ratio can be converted to time at any moment on leading edges of the input signals. Then, the dead time for the conversion method decreases at least five times in compare with the dead time of the static conversion method. A set of miniature delay chip, using this conversion method, is substituted for a conventional division circuit that includes many active elements. Since the miniature delay chip is a passive element, it is possible to install it within the position sensitive chambers. Using the new RDC, the signals of the Backgammon pattern in a SWPC were converted to position with a timing response of one nanosecond for one millimeter length. Position resolution about 2% of the detector length was achieved.

Severe hazards in two dimensional position sensing using wedge & strip and backgammon based patterns

The most unfavorable phenomenon in 2D position sensing is the readout dependence of the two independent dimensions (X, Y). The patterned cathodes, such as the wedge-and-strip, backgammon, chevron and triple charge division patterns, are very sensitive to the source displacement perpendicular to their position sensitive directions (X). This sensitivity results in severe dependance for the horizontal readout to the vertical readout. The predicted deviation due to vertical displacements of a given source, which Is experimentally confirmed shows that the deviation varies with the source displacement along the X axes. This deviation has a maximum value (about 10% of the full length) at the center of the pattern. Since the deviation varies along the X direction, finding a transfer function for correcting the readout is impossible. Using the patterned cathodes in multi wire proportional counters are possible if the wire spacing is a multiple of the pattern width. Also, these cathodes can be used for two dimensional position sensing, without any limitation, if the readout position in the other dimension is done using drift times of the primary electrons. Using this combination, a high resolution (0.25 mm) safe 2D ray trace type patterned telescope was manufactured for particle detection with low threshold energy.

Realization of a passive RTC (Ratio to Time Converter) using a new conversion technique for charge division readout

A dynamic conversion method is introduced to realize a novel RTC (passive RTC) for the charge division readout position sensing. Almost all the methods used for ratio to time conversion are static methods and start the conversion process after the signal peak sensing. Then, the static RTCs are monopolar input converters. The dynamic conversion performs the conversion process during the position signal forming and is based on the ratio to time responses of delay transmission lines. Then, the dynamic RTCs based on this method are bipolar converters. For the dynamic conversion method the ratio can be converted to time at any adjustable moment on the leading edges of the signals decreases the conversion dead time for on-line readouts. A delay line, using this conversion method, is substituted for a conventional RTC which includes at least 20 active elements. Since the delay line is a passive element, it is possible to install it within the position sensitive chambers. Using the dynamic conversion method, the signals of a Backgammon pattern are converted to position and position resolution of about 2% to the full length were achieved.