Semiconductor Radiation Detectors Research Articles

Current and voltage pulses given by semiconductor radiation detectors

Voltage and current waveforms given by different types of semiconductor detectors on various load impedances were calculated. The response of the SD equivalent circuit and its Laplace transform with zero- and pole-locations was tabulated for the four practical cases: voltage-, charge sensitive-, current-, as well as charge sensitive - and current preamplifiers. A unitary specification of detector - preamplifier ensemble was suggested. The calculated voltage and current waveforms were plotted for some particular cases.

Measurement of Diffusion of Gold in Copper by Elastic Scattering of Deuteron

A silicon semiconductor radiation detector has been used to study the diffusion of Au into Cu in the temperature range 356°~440°C by detecting elastically scattered deuterons. In the above temperature range, the measured diffusion coefficients of Au into Cu are somewhat larger than the results of Sippel's experiments, while the activation energy of the diffusion is roughly the same. Diffusion lengths as small as 2×10−7cm can be measured by the present method, which may make it possible to detect the effects of radiation damage on diffusion phenomena in metals.

A semiconductor detector cryostat

This report describes in detail the mechanical design of a multipurpose cryostat system for nonencapsulated Ge(Li) and Si(Li) semiconductor radiation detectors. We have attempted to provide a standardized system that will accept many styles and sizes of detectors, and that lends itself to many kinds of experiments.

Fast pulse pickoff with semiconductor radiation detectors

The problem is investigated of extracting a fast signal at the same time of the energy signal from a solid state detector. The effect of the charge amplifier on this waveform is accounted for. A new method is suggested for achieving fast timing with this kind of detectors.

Recording of hydrogen-ion fluxes by a semiconductor radiation detector

Recording of hydrogen-ion fluxes by a semiconductor radiation detector

Optimum energy resolution of semiconductor radiation detectors with preamplifiers using tubes, field-effect transistors and bipolar transistors

A uniform treatment of tubes, field-effect transistors (FET's) and bipolar transistor (transistors) in first stages in nuclear-detector preamplifiers is given by introducing equivalent circuits with suitable noise sources. Optimizing the system detector-pre-amplifier with respect to energy-resolution, it is feasible to obtain a rms-fluctuation of 90 electron-hole pairs with electrometer-type tubes or FET's, whereas with transistors it is feasible to achieve 900 pairs. These values correspond to ΔE fwhm, Ge = 0.6 keV and ΔE fwhm, Ge = 6 keV.

Gamma spectrometer systems employing an anti-compton annulus

The use of an annular anti-Compton mantle of NaI(Tl) in conjunction with the following scintillation spectrometer types has been investigated: direct and total absorption gamma spectrometer, anti-Compton spectrometer, summing Compton spectrometer, pair spectrometer, coincidence spectrometer employing the pair spectrometer plus an additional detector, multiple coincidence spectrometer, ordinary and sum-peak coincidence spectrometers, sum-coincidence spectrometer and a spectrometer for the detection of gammas and gamma cascades in coincidence with positons. In these spectrometers systems, the annulus functions as the principal detector or is used for coincidence or anti-coincidence gating. Suitable electronic and geometrical arrangements, shielding, collimators and antiscattering shields are described. Most of the spectrometer combinations feature high efficiency, low background and spectra with low Compton tails. Many of the results obtained are applicable also to systems containing semiconductor radiation detectors. The advantages and limitations of the various methods are discussed and a number of further application possibilities of coincidence spectrometers employing an anti-Compton mantle are suggested.

Some Recent Applications of Scintillation and Solid State Counters in Chemistry

The high resolution obtainable with semiconductor radiation detectors has extended the scope of neutron activation analysis. Illustrations are nondestructive analysis of archeological artifacts, meteorites and terrestrial rocks. A quite different new technique is the counting of tracks produced by massive energetic particles in glasses and crystals, which has been used, for example, to date ancient uranium containing glasses. The use of scintillation and proportional counters, amplitude selection, coincidence and anti-coincidence techniques, and the Mossbauer effect are discussed for various applications from X-ray crystallography to the detection of neutrino induced reactions. The anisotropic behavior or channelling in silicon detectors has opened a new field of research on the effect of crystal orientation on energy loss of penetrating particles.

Thermal Cycle Degradation of Charge Carrier Lifetime and Resistivity in Silicon

Numerous published examples of high temperature induced changes in the properties of semiconductors indicate that thermal degradation of charge carrier lifetime may be responsible for excess current and noise in diffused junction radiation detectors. By comparing the noise and current in surface barrier diodes made from silicon which had been subjected to a thermal cycle to the properties of similar diodes made from uncycled material, it is demonstrated that there can be severe degradation of the original material. The relationship between charge carrier lifetime and noise in semiconductor radiation detectors is discussed. Detailed information on changes in resistivity and etch pit density for both p- and n- type silicon from several manufacturers as a function of original resistivity and thermal cycle is presented. Information on excess diode current and noise is available only for the n-type samples. The results are consistent with the previously observed strong dependence on both maximum temperature and rate of temperature change. Large increases in diode current and noise have been observed for cycles with peak temperatures as low as 500°C.

A 4096 Channel 50 Mc/S Servo-Stabilized Analogue-to-Digital Converter

Exploitation of the high resolution and wide energy range of semiconductor radiation detectors imposes severe demands on the linearity and stability of the associated A.D. C. system. A study has been made of various alternative conversion and stabilization schemes with particular reference to their use in a computer-based data gathering system. As a result of this study a 4096 channel 50 Mc/s servo-stabilized ramp converter has been developed. Stabilization is based on a bang-bang servo scheme, the ultimate reference being a mercury double pulse generator. A feature of the design is the ability to dial the energies defining the upper and lower limits of the range of interest. In this way the converter acts as its own window amplifier, always spanning the designated range with 4096 channels. In the design particular attention has been paid to factors affecting the system linearity. Notable among these has been the importance of transient thermal effects in the transistors, and the window expansion scheme which eliminates the problems associated with biased-off amplifiers.

Radiation Measurement Utilizing Communication Theory

Various aspects of communication theory are examined to consider their applicability to radiation measurements. The continuing development of the semiconductor radiation detector with its improved energy resolution has intensified interest in obtaining more information on the fine structure of a complex radioactive decay scheme. The system design criteria discussed includes correlation functions and decision theory. Suitable assumptions, model evolution, and problems to be solved are presented. Ideally the goal is to be able to detect and measure a monoenergetic signal regardless of its energy level or proximity to other monoenergetic signals. Clearly implied in these requirements are both the capability for the minimization of noise effects to improve resolution, and the ability to reach into any existing noise to identify signals smaller than the noise.

The recording of hydrogen ion fluxes by means of semiconductor radiation detectors

The recording of hydrogen ion fluxes by means of semiconductor radiation detectors

Recent Results Obtained with High Field, Internally Amplifying Semiconductor Radiation Detectors

Characterization of the gallium diffused junctions found useful as amplifying radiation detectors indicate a rather surprising window-junction depth relationship. The window, at only the self bias of the junction, has been measured to be a micron or so although the junction depth is ~50 microns. This is a result of the unusual diffusion process used - diffusion to 75 microns with subsequent removal of the heavily acceptor doped, first 25 micron region. Because of potential for low energy detection of these structures (which require thin windows) stress is placed upon window measurements. Measurements made of the response of these structures as photon detectors in the near infrared (0.7 - 1.1 micron) wavelength region are reported. Also initial results which indicate that the x-ray cutoff for these structures lies in the 44-60 Angstrom range.

A preamplifier with 0.7 keV resolution for semiconductor radiation detectors

A preamplifier with 0.7 keV resolution for semiconductor radiation detectors

Investigation of the Anomaly in the Response of Silicon Semiconductor Radiation Detectors at Low Temperatures

Investigation of the response anomaly in silicon semiconductor radiation detectors cooled to temperatures below 40°K has been continued. Experiments with surface barrier detectors show that the mean temperature at which normally ionized impurity atoms accept electrons (as deduced from dE/dx measurement of the depletion depth) is a slowly varying function of the impurity concentration. This behavior is expected from the dependence of the Fermi level on the temperature, impurity concentration and ionization energy. Below the narrow temperature interval in which the majority of the impurity atoms accept electrons and hence become electrically neutral, particles which produce low ionization densities (beta particles) produce pulse heights with room temperature magnitudes, while particles with high ionization densities (alpha particles) produce pulse heights which are lower than those characteristic of room temperature operation and which depend on the detector bias voltage. The results of experiments conducted to investigate polarization effects in lithiumdrifted semiconductor radiation detectors are described.

International Conference on Semiconductor Radiation Detectors

International Conference on Semiconductor Radiation Detectors

A Low-Noise Charge-Sensitive Preamplifier with a Field-Effect Transistor in the Input Stage

The excellent energy resolution of semiconductor radiation detectors has generated a need for charge-sensitive transistorized preamplifiers which have low values of noise line-widths. The application of field-effect transistors in charge-sensitive configurations was investigated, and a low-noise preamplifier was consequently developed. The preamplifier has a junction field-effect transistor in the input stage. The field-effect transistor is connected in cascode with the second stage bipolar transistor which has its collector load bootstrapped by a White follower. The bias stabilization is adequate for normal operation of the preamplifier over an FET temperature range from room temperature to liquid nitrogen temperature. Measured values of the preamplifier noise line-width as a function of pulse-shaping time constants, total input capacitance, and temperature are presented. Formulas are included for the theoretical determination of the noise line-width, Application of the formulas requires knowledge of the parameters of the preamplifier and pulse-shaping circuitry and the noise characteristics of the FET. The FET noise characteristics are shown as experimentally determined graphs of narrow-band equivalent noise resistance versus frequency, temperature, and bias point. Preamplifier noise line-widths less than 1.6 kev fwhm for silicon detectors (189 rms electronic charges) and slopes less than 0.06 kev/pf (7.1 rms electronic charges per pf) were obtained when the FET was cooled to the optimum temperature which was approximately 125°K.

Silicon surface barrier radiation detectors: Some designs and applications: P. G. Salmon and F.L. Allsworth, U.K.A.A. Rep. A.E.R.E.-R-4122, April 1963

A wide range of semiconductor surface-barrier radiation detectors now being developed is described. The performance and electronic requirements of the detectors are discussed together with a general description of the techniques used in the preparation of the crystals and their subsequent encapsulation. The areas of the detectors range from a few mm/sup 2/ to a multiple detector with a total sensitive area of 14 cm/sup 2/. These detectors have wide applications in nuclear physics experiments and for radioactivity search and assay purposes, e.g., in health physics operations, and an outline is given of their practical advantages and limitations. The use of surface-barrier diodes for beta-particle detection is discussed together with details of detectors being developed for medical research purposes. (auth)

Particle identification by pulse shape discrimination in the p-i-n type semiconductor detector

When an ionizing particle enters a semiconductor radiation detector a voltage pulse is produced. The final pulse height is determined by the particle energy, while the range of the particle affects the shape of the pulse. The voltage pulse therefore contains information about the particle type. In the present paper the pulse height at a fixed time during the pulse rise time, is used as the range dependent quantity. A two-dimensional display of this quantity versus the energy of the particle showed that separation could be obtained between deuterons and α-particles with energies in the range from 8 to 26 MeV. Calculations have been made on this effect based on the results of a pulse shape analysis. The agreement between the experimental and the calculated data proves that the theoretical picture is quite adequate.

Production of Thick Semiconductor Radiation Detectors by Lithium Drifting

The application of semiconductor junction radiation detectors1 to penetrating radiation depends on the production of devices having thick depletion layers. In this connection the lithium drift technique developed by Pell2,3,4 has been employed with considerable success5,6,7,8,9. A difficulty encountered with this method is the long time required to produce compensated regions a few millimeters or more in thickness. However it can be shown that the compensated region produced by drifting at constant temperature is proportional to the cube root of the total energy dissipated in the drifting process. This indicates the importance of operating at the highest attainable power at all times, and has led to the design of a system employing a fluorocarbon liquid as a vapor phase coolant in conjunction with a pulsed constant wattage supply. Significantly improved drift rates have been achieved with this technique, which has the added advantage of being well suited to the simultaneous drifting of a number of detectors at constant power from a single power supply.