Space, Time, and Energy Measuring Gamma-ray Detector

134 Space, Time, and Energy Measuring Gamma-ray Detector--Innova Laboratories, Inc., 11199 Sorrento Valley Road, Suite L, San Diego, CA 92121-1334; (619) 452-8760 Dr. Wayne Vernon, Principal Investigator Dr. George W. Webb, Business Official DOE Grant No. DE-FG03-97ER82410 Amount: $74,970 Measurement technology in the field of nuclear physics ahs approached the limits of technology. As a result, there is a need for a new gamma-ray detector that simultaneously measures gamma-ray energies and arrival times in each array element. In addition, a new type of time encoding needs to be incorporated into the dector so that arrival time measurements with sub-nanosecond accuracy will be possible when detector elements have fast charge carriers. This project will develop such a system, and will rely on pixel geometry of the detector pieces and closely associated electronics because the resulting large frequency bandwidth makes the timing measurement possible. Germanium will be used as the detector element, and photon energies from 5 to 200 thousand electron volts will be measured. Large area arrays, combined with the operating temperature requirements of the germanium detector element will require a new form of low mass cryostat. In one application, the detector system, inside of its cryostat, will have to be inserted into the vacuum tank of an experiment such as the GAMMASPHERE; low mass is essential for keeping losses of high energy gamma rays to a minimum. The goal of Phase I is to make a compact, moderate cost cryostat incorporating the above detector. Other possible problem areas such as behavior of cold silicon, verifying the time encoding scheme, and starting the investigation of data acquisition schemes will be pursued as well. This project will lead to the construction, during Phase II, of a module which has 25,600 pixels, a total area of about 80 square centimeters, and the ability to measure arrival times with better than 250 picosecond accuracy and energies to 1per cent at 200 thousand electron volts. It will be contained in a flowing gas cryostat with low masswalls. A new form of silicon chip will be developed as part of the solution. Commercial Applications and Other Benefits as described by the awardee: Pixel-based X-ray and gamma-ray detectors have applications in medical imaging; arrival time information can be very useful in PET scanning. Gamma-ray astrophysics has many areas which can use this combination of thin-walled cryostat and pixel-based detector. There are also a wide range of time-of-flight applications in materials science and chemistry where a pixel-based Time Encoder would be very valuable.