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Manufacturing avalanche diodes for detection of low energy gamma- and X-rays
Abstract
Three types of silicon avalanche detectors for low energy gamma- and X-ray counting were manufactured using planar and planar-epitaxial technology. The detectors were tested at room temperature with 57Co and 241Am. Besides the characteristic lines of the sources additional peaks were observed due to X-rays of elements included in the matrices and holders of the sources.For 6.4 keV the energy resolution is approximately 10%.
This paper briefly reviews the present status of nuclear techniques used in geology and mining and an attempt is made to identify nuclear (and atomic) data that are needed to improve these methods and to extend their possible applications. The following topics are discussed: role of nuclear techniques in chemical analysis of rocks and minerals, main fields of the geological applications, advances in the techniques and methods, status of required nuclear data.
The note demonstrates the potential capabilities for X-ray analysis by avalanche detectors with relatively thick drift regions. The experiments showed that Si AD can be used in X-ray analysis of the K lines of all elements from the first half of the Periodic Table and of the L and M lines of almost all elements. The standard planar technology used for detector manufacturing can reduce their price.
The performance of a silicon pad detector was tested at room temperature. Energy and time resolution were measured using different types of preamplifiers. An integrated circuit board was designed to handle a 20 element silicon pad detector (2×10). The results show that an energy resolution of about 6.7 keV for 320 keV electrons and a time resolution of 3.6 ns have been achieved at room temperature.
-p-π-p+ silicon avalanche diodes for the detection of heavy charged particles. Two sets of measurements of the alpha spectrum of
241Am were carried out, one without acollimator and one with acollimator. The obtained alpha spectra for all bias voltages
differ substantially from the spectrum obtained with aconventional semiconductor detector. The experiments clarified the
amplification mechanism of the type n+-p-π-p+ silicon avalanche detector for charged particles. We demonstrated that the reasons for the unconventional alpha spectra are
the mechanisms of internal amplification and also the specific detector design.
In some environmental cleanup applications, there is a need for utilizing Si PIN diodes to detect electrons, x-rays, and low-energy gamma rays with very good energy resolution. The advantage of these detectors in such particular applications when compared with others is the ease of the operation at room temperature and at much lower bias voltages. We are currently investigating the feasibility of using silicon PIN photodiodes to detect the x-rays of radioisotopes such as Cs, Eu, La, U, Th, Am, and Pu for monitoring and characterizing topsoil contamination. The design and development of this Si PIN diode array will be discussed and the results of tests and its overall performance will be presented.
The application of reach-through avalanche photodiodes (R'APD) as a photodetector for scintillator tiles has been investigated. The light collected by WLS fibers (0.84mm and 1mm diameter) embedded in the scintillator has been transmited to the 0.5mm2 active surface of APD by clear optical fibers and optical connectors. A low noise charge sensitive preamplifier (approximately 400 electrons equivalent noise charge) has been used to gain the photodiode signal. Various configurations of tile-fibre systems, suitable for CMS and LHCb experiments at LHC have been studied using cosmic muons and muon beam at SPS at CERN. In order to optimize the performance of APD, measurments in the temperature range from -10C to +25C have been done. The MIP detection efficiency and electron/MIP separation have been estimated in order to determine applicability of the readout for LHCb preshower. Comment: 20 pages,13 figures
A review on the present status of room temperature semiconductor nuclear radiation detectors including GaAs, CdTe, HgI2 and diamond detectors with their application is described.
Avalanche diodes which are sensitive enough to detect low energy x-rays and beta particles have been fabricated and tested. They operate at room temperature and their structure is based on large area avalanche photodiodes. X-ray response has been measured over the energy range of 4 keV to 26 keV. At 5.9 keV a FWHM of 10% was obtained. In addition, multi-element sensors have been fabricated. Beta particles were detected from a variety of isotopic sources including C1-36, Sr-90, C-14 and H-3. The tritium beta particles, with 5 keV average energy, were detected with a 20% counting efficiency from a calibrated source. Tritium beta particles from biological samples were also measured. The high sensitivity to low energy x-rays and beta particles makes this detector useful for many industrial, military and commercial applications, and in particular for biomedical research.
We have demonstrated the potential of large area avalanche photodiodes to complement photomultiplier tubes and conventional photodiodes in numerous applications. In particular, they are compatible with BGO scintillator crystals in important applications such as positron emission tomography and high energy physics research. The photodiodes described here have overcome the limitations in size and sensitivity which had previously prevented the use of avalanche devices in these applications. As scintillation sensors in radiation detectors, one inch diameter avalanche photodiodes have been used to obtain Cs-137, 662 keV spectra with 8.5% FWHM resolution coupled to NaI at room temperature and 24% FWHM coupled to BGO at 0°C. As low energy x-ray sensors, small devices have a 10% FWHM for 5.9 keV Mn, k x-rays. The devices are also extremely sensitive to beta particles. These attributes make them useful for detecting ionizing radiation in a wide variety of applications.