DocumentCode :
1139410
Title :
A gain-programmable transit-time-stable and temperature-stable PMT Voltage divider
Author :
Liu, Yaqiang ; Li, Hongdi ; Wang, Yu ; Xing, Tao ; Xie, Shuping ; Uribe, Jorge ; Baghaei, Hossain ; Ramirez, Rocio ; Kim, Soonseok ; Wong, Wai-Hoi
Author_Institution :
Anderson Cancer Center, Univ. of Texas, Houston, TX, USA
Volume :
51
Issue :
5
fYear :
2004
Firstpage :
2558
Lastpage :
2562
Abstract :
A gain-programmable, transit-time-stable, temperature-stable photomultiplier (PMT) voltage divider design is described in this paper. The signal-to-noise ratio can be increased by changing a PMT gain directly instead of adjusting the gain of the preamplifier. PMT gain can be changed only by adjusting the voltages for the dynodes instead of changing the total high voltage between the anode and the photocathode, which can cause a significant signal transit-time variation that cannot be accepted by an application with a critical timing requirement, such as positron emission tomography (PET) or time-of-flight (TOF) detection/PET. The dynode voltage can be controlled by a digital analog converter isolated with a linear optocoupler. The optocoupler consists of an infrared light emission diode (LED) optically coupled with two phototransistors, and one is used in a servo feedback circuit to control the LED drive current for compensating temperature characteristics. The results showed that a six times gain range could be achieved; the gain drift was <0.5% over a 20°C temperature range; 250 ps transit-time variation was measured over the entire gain range. A compact print circuit board (PCB) for the voltage divider integrated with a fixed-gain preamplifier has been designed and constructed. It can save about $30 per PMT channel compared with a commercial PMT voltage divider along with a variable gain amplifier. The preamplifier can be totally disabled, therefore in a system with a large amount of PMTs, only one channel can be enabled for calibrating the PMT gain. This new PMT voltage divider design is being applied to our animal PET camera and TOF/PET research.
Keywords :
calibration; circuit feedback; digital-analogue conversion; gain control; light emitting diodes; nuclear electronics; photocathodes; photomultipliers; phototransistors; positron emission tomography; preamplifiers; printed circuits; voltage control; voltage dividers; LED drive current; PMT gain; animal PET camera; anode; calibration; compact print circuit board; critical timing requirement; digital analog converter; dynode voltage; fixed-gain preamplifier; gain-programmable transit-time-stable divider; infrared light emission diode; linear optocoupler; photocathode; phototransistors; positron emission tomography; preamplifier gain; servo feedback circuit; signal-to-noise ratio; temperature characteristics; temperature-stable PMT voltage divider; time-of-flight detection; total high voltage; transit-time variation; Anodes; Cathodes; Digital control; Light emitting diodes; Photomultipliers; Positron emission tomography; Preamplifiers; Signal to noise ratio; Timing; Voltage; PET; PMT; voltage divider;
fLanguage :
English
Journal_Title :
Nuclear Science, IEEE Transactions on
Publisher :
ieee
ISSN :
0018-9499
Type :
jour
DOI :
10.1109/TNS.2004.835776
Filename :
1344377
Link To Document :
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