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 (025 mm) safe 2D ray trace type patterned telescope was manufactured for particle detection with low threshold energy

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

Any dependence of the readout positions (X) to the source vertical displacements (Y) for one dimensional position sensing results in extremely unusual phenomenon for 2D position sensing. In this paper the dependence and the problems based on the dependence is studied for position sensing methods. It is shown that severe dependence exists for one dimensional position sensing using patterned cathodes and the applications of this method must be reviewed for 2D position sensing. Many problems such as resolution degradation, double peak readout, "S" type image distortion and centroid shift for 2D position sensitive detectors are based on this unknown phenomenon. Almost all the patterns, such as the wedge-and-strip, backgammon, chevron and diamond patterns have the dependence along the wedged part. For this part the deviation due to the source vertical displacements varies with the source horizontal positions. This deviation has a maximum value (about 10% of the full length) at the center of the pattern. Using the patterned-cathodes with MWPC (multiwire proportional counters) for 2D position sensing is possible if the wire spacing is a multiple of the single 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.

Interdependence of readout positions (X, Y) for two dimensional patterned position sensitive detectors

A  new  type  of  two-dimensional  position  sensitive  gas  counter  for  transmission  cou n t er  with a  backgammon - shaped   flat electrode  has been developed.  The two dimensional  position  read-out can  be  achieved  with  the  combination  of  the  backgammon-shaped   flat  electrode  read-out . as horizontal position  and the drift time measurement  read-out  as vertical position.  The gas counter  is designed  as a transmission  trajectory counter that can be used to determined  angle of incident  charged particle  in the charged particle  detecting system.  To check the characteristics of this gas counter, test experiments are performed with a coincidence  plastic scintillation  counter  and   p - ray source of  90 Sr.

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A Two-dimensional Transmission Counter with a Backgammon-Drift Read-Out Technique

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

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.

A. Nohtomi

Papers

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

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

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