A simple technique to increase the linearity and field-of-view in position sensitive photomultiplier tubes

Conference · Tue Dec 31 04:00:00 EST 1996

OSTI ID:513079

Clancy, R L; Thompson, C J; Robar, J L; Bergman, A M ^[1]

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1. McGill Univ., Montreal, Quebec (Canada)

Crossed anode wire position sensitive photomultiplier tubes (PS-PMTs) detect the location of a light source and provide the X and Y axis coordinates of the event. These coordinates are typically generated using Anger logic, where a resistor chain divides the current flow into two signals for each coordinate (X{sup +}, X{sup -} & Y{sup +}, Y{sup -}). In the standard readout, identical resistor values are used across the entire resistor chain. While this arrangement provides a linear readout in the central portion of the photomultiplier face, the readout is non-linear and sometimes even double valued near the edges of the PS-PMT due to the truncation of the charge beyond the last anode wire. To counter this effect, we have increased the value of the resistance near the ends of each resistor chain in order to compensate for the charge lost beyond the anode wires. Measurements were made using a Hamamatsu R-3941 PS-PMT coupled to a pixellated BGO matrix of cut crystals with a 2mm pitch in each direction. After changing the end resistors, the usable field-of-view increased by 39%. This simple modification should enhance the operation of PS-PMTs in applications such as positron emission mammography, and small animal PET imaging.

• OSTI ID: 513079
• Report Number(s): CONF-961123--; CNN: Grant 36672
• Country of Publication: United States
• Language: English

Related Subjects

44 INSTRUMENTATION
INCLUDING NUCLEAR AND PARTICLE DETECTORS
CHARGE DISTRIBUTION
MODIFICATIONS
PHOTOMULTIPLIERS
POSITION SENSITIVE DETECTORS
POSITRON COMPUTED TOMOGRAPHY
READOUT SYSTEMS