Silicon Surface Barrier Detector Research Articles

Characteristics of large area silicon surface barrier detectors

This paper presents a detailed description of an upgraded silicon surface barrier (SB) detector and analysis of X and gamma radiation and of the spectra given by it. The most frequently used application of these detectors was in measurements and analyses of alpha spectra. However, analysis of spectra gained here presented a silicon surface barrier detector showing possibilities of their wider application in various nuclear techniques and technologies. This specially referes to the feasibility of their use in the conditions that are different from those in laboratories, such as mines, surroundings of nuclear power plants etc. Recorded spectra from 57Co, show that SB detectors are very acceptable in nuclear laboratories for nuclear spectroscopy at room temperatures. On the contrary, field application in nuclear techniques connected with the protection of the environment and counting systems is much wider, and the detector temperature could reach 60 °C.

Plutonium concentration distribution in bed load sediment samples along the Romanian sector of the Danube River and the Black Sea coast

The concentrations of210Po have been determined in 12 sediment samples collected from the bed of the Romanian Danube river and the Black Sea coast during June–September 1994. After the sample preparation and the addition of the208Po tracer, polonium was coprecipitated with manganese dioxide, the precipitate was dissolved in hydrochloric acid and the polonium isotopes deposited on silver planchettes were counted by α-spectrometry. The resolution of the subsequent α-spectra was typically 40 to 60 keV full-width-half-maximum with 450 mm2 silicon surface-barrier detectors at 30% counting efficiency. The procedure is quite fast, giving chemical yields between 60 and 80%. The210Po concentrations range between 5 and 73 Bq kg−1 dry, showing for the first time the polonium contamination distribution along the Romanian sector of the Danube river and the Black Sea coast.

Channeling with 290 MeV/u C6+ ions in a Si crystal

We have developed a parallel beam suitable for channeling experiments with relativistic heavy ions at HIMAC (Heavy Ion Medical Accelerator in Chiba). To observe channeling phenomena, we used a silicon surface barrier detector (SSD) as a sample crystal and as a detector for the energy loss in itself. Further, we measured the angular spread of the beam transmitted through the SSD by a position sensitive detector (PSD) placed downstream of the SSD. Under <110> axial and (111), (220) and (004) planar channeling conditions, we observed that the energy loss of the channeled ions in the SSD became almost a half and their angular spread was also reduced.

Design of radial neutron spectrometer array for the International Thermonuclear Experimental Reactor

We designed the radial neutron spectrometer using a new type DT neutron spectrometer base on a recoil proton counter-telescope technique aiming ion temperature measurement for the International Thermonuclear Experimental Reactor (ITER). The neutron spectrometer will be installed on the well collimated neutron beam line. A large area recoil proton emitter is placed parallel to the incident neutron beam and microchannel collimating plates are inserted between the radiator and the recoil proton detectors away from the neutron beam in order to limit the scattering angle of protons to the proton detectors. Here a very thin polyethylene film and a silicon surface barrier detector are employed as the radiator and proton detector, respectively. The energy resolution and detection efficiency are estimated to be 2.5% and 1×10−5 counts neutron−1 m2, respectively, for the DT neutron through Monte Carlo calculations. Five units of the spectrometers will be installed just outside the biological shield, will include a fan array using penetrations inside the bioshield and a precollimator in the horizontal port. The lifetime of the proton detectors is estimated to be about one year in the basic performance phase of ITER by neutron transport calculations using the Monte Carlo neutron and photon transport code (MCNP).

A system for correlation measurement of fission fragments and prompt neutrons for thermal neutron induced fission

For the purpose of the correlation measurement of fission fragments and prompt neutrons for thermal neutron induced fission, a system consisting of two fragment detectors and a neutron detector was developed. In this system, one fission fragment was detected with a silicon surface barrier detector (SSBD) and the other with a specially designed parallel plate avalanche counter (PPAC). The PPAC had double structures, one for fast timing and the other for position detection. A prompt neutron emitted from a fragment with a specified mass was detected with an organic liquid scintillator (NE213) in this system. The SSBD supplied not only the energy signal of one fragment but also the start timing signal to the time-of-flight (TOF) measurements of the other fragment and the prompt neutron. We tried to carry out the fragment-neutron correlation measurement for 235U(n th, f) with this system, and succeeded in obtaining the neutron energy spectrum in the center-of-mass system and the neutron multiplicity depending on the fragment mass.

A preliminary study of internal conversion electron spectroscopy for application to neutron activation analysis

A simple internal conversion electron spectroscopical method was coupled with RNAA. High energy internal conversion electrons were measured at room temperature using a surface-barrier silicon detector and MCA. By neutron irradiation of Cd and Sn,115Cd and113Sn were produced. Their daughter nuclides,115mIn and113mIn emit intemal conversion electrons of relatively high energy. They were extracted into diethyl-ether from hydrobromic acid solution, back-extracted to water and evaporated to dryness in a stainless steel dish. The dish and silicon detector were placed in a chamber so that they were facing each others. By supplying 200 V of bias to detector, intemal conversion electrons peaks of 308.3 and 363.8 keV from115mIn and113mIn can be observed even at room temperature. The present method can be applied to RNAA such as in the detemination of Cd in metallic zinc powders.

Simulataneous profiling of hydrogen and deuterium by 2.6 MeV 4He ERDA using a ΔE - E telescope detector

For depth profiling of hydrogen isotopes by elastic recoil detection analysis (ERDA) with 2.6 MeV 4He ions a special ΔE - E telescope type detector system was tested. It allows the separation of hydrogen and deuterium recoils as well as backscattered helium particles. For particle identification from the energy loss ΔE a thin 3.7 μm silicon transmission detector was used while the residual energy was measured with a standard 100 μm PIPS silicon surface barrier detector. The depth profiles of deuterium and hydrogen were measured at plasma deposited a-C:H:D layers as well as at samples exposed to plasma discharges in the tokamak experiment ASDEX-Upgrade.

A method for emanation coefficient measurements of 222Rn and 220Rn from soils

A new method to determine emanation coefficient of 222Rn and 220Rn from soil samples is presented. The aim of the present work is to obtain a useful, rapid and noise free method to make soil sample measurements. The method is based on the measurements of specific activities of 220Rn and 222Rn in a sealed chamber using α-spectrometry and on the measurements of specific activities of 232Th and 226Ra using γ-spectrometry. The specific activities of radon isotopes are measured using the electrostatic collection of polonium isotopes on the silicon surface barrier detector mounted at the top of a chamber containing the soil sample. In the chamber volume, the process of balance has been studied and the results show that the time needed to achieve the equilibrium is shorter than in the presence of free exhalation.

A high efficiency device for the detection of radioactive xenon isotopes

A detector has been designed for the detection of sub-Becquerel amounts of the radioactive xenon isotopes 131mXe and 133Xe. High efficiency has been obtained by the condensation of the sample directly onto the surfaces of two closely spaced silicon surface-barrier detectors. The measurement of the 131mXe is based on the detection of the conversion electrons. The 133Xe measurement is obtained by detection of the 81 keV photon in a NaI detector that nearly surrounds the silicon detectors. The minimum detectable activity for 133Xe is 0.015 Bq. For a 131mXe sample with no 133Xe present, the minimum detectable activity is about 0.003 Bq.

Diamond radiation detector using a synthetic IIa type mono-crystal

A diamond radiation detector using a synthetic IIa type mono-crystal was developed. An energy resolution of 0.81%, 45 keV, was achieved for 5.486 MeV α particles in a vacuum environment. The ionization energy, ∈ Diamond, was estimated as 13.07 eV by calibration with a silicon surface barrier detector. On a preamplifier output signal, a trapping and detrapping effect on holes was observed.

Low-energy Rutherford backscattering-ion channeling measurement system with the use of several tens keV hydrogen and a time-of-flight spectrometer

We have developed a low-energy Rutherford backscattering spectrometry (RBS)-ion channeling measurement system for the analysis of thin films and solid surfaces with the use of several tens keV hydrogen ions and a time-of-flight spectrometer which was originally developed by Mendenhall and Weller. The depth resolution of our system is better than that of a conventional RBS system with MeV helium ions and silicon surface barrier detectors. This measurement system is very small in size compared to the conventional RBS-ion channeling measurement system with the use of MeV He ions, because of the small ion accelerator for several tens keV ions. The analysis of crystalline thin films which utilizes ion channeling effect can be performed with the use of this low-energy RBS-ion channeling measurement system. The in situ observation of the thermal reaction between iron and silicon substrate with the use of this measurement system is also demonstrated.

The noise reduction of silicon detectors by wafer analyses and technological procedures

The technological preparation of a front side of a surface-barrier silicon detector (SBSD) was analyzed in two different ways. At a laboratory temperature, the developed procedures made it possible to decrease the FWHM-values of monolithic circular SBSDs with detection areas within a range of 20–200 mm 2 and a minimum depleted layer of 900–1400 μm to less than 75% of the values obtained without application of the diagnostic results described.

Absolute experimental and numerical calibration of the 14 MeV neutron source at the Frascati neutron generator

The absolute neutron yield of the 14 MeV Frascati neutron generator (FNG) is routinely measured by means of the associated alpha-particle method with a silicon surface barrier detector (SSD). This paper describes the work carried out to characterize the neutron source in terms of absolute intensity and angle-energy distribution of the emitted neutrons. The development of the measuring setup and the assessment of the measurement results are also reported. A complementary calibration procedure for validating the SSD results, based on the use of fission chambers and the activation technique, is also reported. An accurate analysis of the system has been performed via the Monte Carlo neutron and photon MCNP transport code. A detailed model of the neutron source that includes ion slowing down has been inserted into the MCNP code to permit a numerical calibration of the neutron source for comparison with the experimental results. The resulting agreement among the various methods is very good considering the uncertainties, and an accuracy of ±2% is achieved for the measurement of the 14 MeV neutron yield of the FNG.

A multiple detector approach to radiological hot cell nuclear and chemical remote measurements

A remote measurement system has been constructed for in-situ gamma and beta isotopic characterization of highly radioactive nuclear material in hostile environments. A small, collimated, planar CdZnTe detector is used for gamma-ray spectroscopy. Spectral resolution of 2% full-width-at-half-maximum at 662 keV has been obtained remotely using risetime compensation and limited pulse shape discrimination (PSD). Isotopic measurement of high-energy beta emitters was accomplished with a ruggedly made, deeply depleted, surface barrier silicon detector. The primary function of the remote nuclear screening system is to provide fast qualitative and quantitative isotopic assessment of high-level radioactive material.

A beta-ray spectrometer based on a two-or three silicon detector coincidence telescope

Abstract This report describes the operation of a beta-ray energy spectrometer based on a silicon detector telescope using two or three elements. The front detector is a planar, totally-depleted, silicon surface barrier detector that is 97 μm thick, the back detector is a room-temperature, lithium compensated, silicon detector that is 5000 μm thick, and the intermediate detector is similar to the front detector but 72 μm thick and intended to be used only in intense photon fields. The three detectors are mounted in a light-tight aluminum housing. The capability of the spectrometer to reject photons is based upon the fact that the incident photon will have a small probability of simultaneously losing detectable energy in two detectors, and an even smaller probability of losing detectable energy in all three detectors. Electrons will, however, almost always record measurable events in either the front two or all three detectors. A coincidence requirement between the detectors thus rejects photon induced events. With a 97 μm thick detector the lower energy coincidence threshold is approximately 110 keV. With an ultra-thin 40 μm thick front detector, and operated at 15°C, the spectrometer is capable of detecting even 60–70 keV electrons with a coincidence efficiency of 60%. The spectrometer has been used to measure beta radiation fields in CANDU reactor working environments, and the spectral information is intended to support dose algorithms for the LiF TLD chips used in the Ontario Hydro dosimetry program.

Diurnal variation of radon progeny in indoor and outdoor air of a subtropical city

Two monitors that collect radon progeny on a 0.8 μm filter at a 150 mL/min pumping rate, and detect gross alpha counts by a silicon surface barrier detector were used to continuously measure the working levels indoors and outdoors in Kaohsiung city for 2 y. The average outdoor radon progency concentration was about 18.3 nJm −3, while the indoor average of two different sites was 57.0 nJm −3 for the basement and 47.2 nJm −3 for the ground floor. The indoor/outdoor ratio of radon progeny concentration was around 2.4. Fourier analysis, based on hourly data, showed a significant periodic cycle at 24 h. This daily cycle was significant in winter and spring but not as significant in summer and fall. There was a less significant 12-h cycle for outdoor radon progeny. The radon progeny level was high in the early morning and low in the afternoon. This phenomenon is related to the temperature of near surface air for outdoor with a correlation coefficient of −0.68. The crosscorrelation function shows a 4-h time lag between indoor and outdoor data. It may be due to the limited space for indoor radon and its progeny to disperse. The maximum correlation coefficient in the 0.3-0.4 range implies a weak correlation between indoor and outdoor radon progeny. This analysis shows the typical radon progeny profile in a city of oceanic climate in a subtropical zone.

Comparison and implications of charge collection measurements in silicon and InGaAs irradiated by energetic protons and neutrons

A variety of charge collection measurements by energetic protons and neutrons have been measured and compared. These include deposition in: small silicon junctions, large volume American and Russian silicon surface barrier detectors, and InGaAs photodiodes.

Comparison of signal rise-times in totally depleted P-type and N-type silicon surface barrier detectors

Comparison of signal rise-times in totally depleted P-type and N-type silicon surface barrier detectors

Comparison of signal rise-times in totally depleted P-type and N-type silicon surface barrier detectors

The rise-times of charge collection signals from the incidence of protons and alpha-particles of energies up to 25 MeV have been measured for totally depleted silicon surface barrier type detectors made from P-type and N-type silicon. The detectors were of similar thickness and the resistivities of the bulk materials such that their depletion voltages were comparable. The measurements show that P-type detectors can give at least as good particle identification by signal rise-time as can N-type detectors. Analyses of the experimental data show that the previous simple theory of charge collection rise-time identification has to be modified to take account of the finite internal space charge fields in the plasma columns along the particle tracks. The theory must also include contributions from the movement of holes. The velocities of electrons and holes deduced via this theory from the experimental data show a ratio which does not agree for mobility dominated velocities.

An approximate formula for the angular dependence of the residual defect in a silicon surface barrier detector

A new formula for the angular dependence of the amplitude residual defect based on the surface recombination model for charge losses is presented. Experimental results for Xe and Ni ions are compared with calculated ones. An attempt to apply this formula in a computer code to generate the energy distribution of spontaneous fission events of nuclei implanted into the detector was made.