Silicon Surface Barrier Detector Research Articles

First measurements of energetic protons in Mega Amp Spherical Tokamak Upgrade (MAST-U).

First proton production rates from the d(d,p)t reaction in the Mega Amp Spherical Tokamak Upgrade (MAST-U) are measured. The data were taken during the MAST-U experimental campaign with an upgraded version of the proton detector (PD) previously used in MAST. The new detector array consists of three collimated silicon surface barrier detectors with a depletion depth of 300μm and a collimated 120μm thick diamond detector, mounted on the MAST-U reciprocating probe arm. This array measures the energies of unconfined energetic 3MeV protons and 1MeV tritons mainly produced by beam-thermal DD reactions during neutral beam injection heating. Diamond detectors have the potential to be uniquely suited to detect charged fusion products as they promise to be much more radiation resistant and much less sensitive to temperature variations compared to silicon-based detectors. Using silicon and diamond-based detectors simultaneously allowed us to directly compare the performance of these two detector types. PD particle rates measured during different plasma scenarios are presented and compared to neutron rates measured using the neutron camera upgrade and TRANSP predictions.

Simulation of Silicon Surface Barrier Detector with PN Junction Guard Rings to Improve the Breakdown Voltage.

Silicon surface barrier detectors (SSBDs) are normally used to detect high-energy particles due to their excellent properties. For better charge collection efficiency (CCE), the SSBD device should be operated at higher reverse voltages, but this can lead to device breakdown. Therefore, we used a PN junction as a guard ring to increase the breakdown voltage of the SSBD. The structures of two SSBD devices are drawn and simulated in this work. Compared with a conventional SSBD (c-SSBD), the use of a PN junction as a guard ring for an SSBD (Hybrid-SSBD) achieves higher breakdown voltages, of over 1500 V under reverse bias. This means that Hybrid-SSBD devices can operate at higher reverse voltages for better charge collection efficiency (CCE) to detect high-energy particles. Then, we simulated the different structure parameters of the Hybrid-SSBD guard rings. Among them, the doping depth and gap width of the guard ring (between the innermost guard ring and the active area) have a greater impact on the breakdown voltage. Finally, for Hybrid-SSBD devices, the optimal characteristics of the guard ring were 1 × 1019 cm-3 doping concentration, 1 μm doping depth, and innermost guard ring width and gap width of 5 μm and 3 μm, respectively.

Study of the Elastic Scattering in the d + 11B system for EBS purposes

The implementation of boron in several fields, such as in the creation of p-type semiconductors in electronics, has created the need for the accurate quantitative determination of its depth profile concentrations in near surface layers of various matrices. In the framework of IBA techniques a combination of Elastic Backscattering Spectroscopy, along with Nuclear Reaction Analysis, has been proposed in order to address the current needs for boron depth profiling, focusing on the use of proton beams. Deuteron beams however offer superior mass resolution with similar stopping power values and simultaneous excitation of most light elements. Unfortunately, the lack of experimental datasets concerning the deuteron elastic scattering on boron impedes their use. Thus, in the present work, the first set of measurements for the 11B(d,d0) differential cross section covering the Ed,lab=1300-1860 keV energy range for the backscattering angles of 150ο, 160ο and 170ο were carried out. The study was conducted at the 5.5 MV Tandem Accelerator of the Institute of Nuclear and Particle Physics, in the National Center of Scientific Research “Demokritos”, Athens, Greece. The target was a thin, self-supporting aluminum foil, upon which a thin natB (isotopic ratio: 11B 80.1%, 10B 19.9%) layer was deposited using the sputtering technique at RBI, Zagreb, Croatia, followed by the evaporation of an ultra-thin layer of 197Au on top for normalization and wear protection purposes. The outgoing particles were detected using silicon surface barrier (S.S.B.) detectors and the differential cross sections for elastic scattering were determined from the resulting spectra via the relative technique

Differential Cross-section Measurements for 3He Elastic Scattering on 16O and 27Al

In the present work measurements to determine the differential cross section values for the elastic scattering of 3He on 16O and 27Al were carried out at the Ruđer Bošković Institute (RBI) Tandem Accelerator Facility in Zagreb, Croatia, covering the E3He,lab=3500-5600 keV energy range, using four Silicon Surface Barrier (SSB) detectors positioned at the backscattering angles of 130°, 145°, 157.7° and 165ο. The target was constructed at the facility and was comprised of a thin, self-supporting aluminum foil, upon which a thin layer of natB (isotopic ratio: 11B 80.1%, 10B 19.9%), along with 12C, 14N, 16O, was deposited using the sputtering technique. In addition, an ultra-thin layer of 197Au was evaporated on top for wear protection and normalization purposes.

Differential Cross-section Measurements for Deuteron Elastic Scattering on 11B

The implementation of boron in several fields, such as in the creation of p-type semiconductors in electronics, has created the need for the accurate quantitative determination of its depth profile concentrations in near surface layers of various matrices. In the framework of IBA techniques, a combination of Elastic Backscattering Spectroscopy (EBS), along with Nuclear Reaction Analysis (NRA), has been proposed in order to address the current needs for boron depth profiling, based on the use of a proton beam. Deuterons offer superior mass resolution with respect to protons, having similar stopping power values, but, unfortunately, the lack of experimental datasets concerning the deuteron elastic scattering on boron impedes their use. Thus, in the present work, the first set of measurements for the 11B(d,d0) differential cross sections covering the Ed,lab=1300-1860 keV energy range for the backscattering angles of 150°, 160° and 170° was carried out. The study was conducted at the 5.5 MV Tandem Accelerator of the Institute of Nuclear and Particle Physics, in the National Center of Scientific Research “Demokritos”, Athens, Greece. The target was a thin, self-supporting aluminum foil, upon which a thin natB (isotopic ratio: 11B 80.1%, 10B 19.9%) layer was deposited using the sputtering technique at RBI, Zagreb, Croatia, followed by the evaporation of an ultra-thin layer of 197Au on top for wear protection and normalization purposes. The outgoing particles were detected using 6 Silicon Surface Barrier (S.S.B.) detectors and the differential cross sections for the elastic scattering were determined from the resulting spectra via the relative measurement technique.

Experimental Study of the Pressure Effects on Stopping Power for Alpha Particles in Air

This paper is to investigate stopping power of α-particles in air at various pressure of 0 to 1 bar, using a surface barrier silicon detector. The energy loss has been obtained at a different distance from 0 to 10 cm. It was found that the energy of the passed α-particles has been decreased in a small vacuum chamber with increasing pressure. It is also studied that the amount of α-particles reaching the detector follows a decreasing behavior as the distance increases. The result of stopping power was compared with ICRU and SRIM result. Experimental, ICRU and SRIM results for stopping power are closely in good agreement.

Enhancement in energy resolution of silicon surface barrier detector at low temperature

Enhancement in energy resolution of silicon surface barrier detector at low temperature

Degradation of silicon detectors under long-term irradiation by 252Cf fission products

The response function of the recoil nuclei in detectors designed for detection of neutrinos or dark matter particles can be determined only through usage of a neutron source with a known energy spectrum. A possible solution for a compact neutron calibration source is a combination of a 252Cf neutron source and a semiconductor detector that detects fission fragments, and thus records the neutron emission moment. This work is devoted to the degradation study of the operating parameters for silicon semiconductor detectors irradiated by fission fragments of the nuclide of 252 Cf. Two types of Si detectors were under investigations - silicon-lithium Si(Li) p-i-n detectors and silicon surface barrier detectors. As a result of the measurements, the maximum permissible radiation doses for the correct operation of both types of detectors and the relation of the received radiation dose to the spectroscopic characteristics of the detectors were determined.

Measurement of the ^{232}Th(n,f) cross section with quasi-monoenergetic neutron beams in the energy range 2\u201318 MeV

The fission cross section of ^{232}Th has been measured at fast neutron energies, using a setup based on Micromegas detectors. The experiment was performed at the 5.5 MV Van de Graaff Tandem accelerator in the neutron beam facility of the National Centre for Scientific Research “Demokritos”. The quasi-monoenergetic neutron beams were produced via the ^{3}H(p,n), ^{2}H(d,n) and ^{3}H(d,n) reactions, while the ^{238}U(n,f) and ^{235}U(n,f) reactions were used as references, in order to acquire cross-section data points in the energy range 2–18 MeV. The characterization of the actinide samples was performed via alpha -spectroscopy with a Silicon Surface Barrier (SSB) detector, while Monte Carlo simulations with the FLUKA code were used to achieve the deconvolution of the ^{232}Th alpha peak from the alpha background of its daughter nuclei present in the spectrum. Special attention was given to the study of the parasitic neutrons present in the experimental area, produced via charged particle reactions induced by the particle beam and from neutron scattering. Details on the data analysis and results are presented.

Characterizing x-ray transmission through filters used in high energy density physics diagnostics.

We report on the design and implementation of a new system used to characterize the energy-dependent x-ray transmission curve, Θ(E), through filters used in high-energy density physics diagnostics. Using an Amptek X-123-CdTe x-ray spectrometer together with a partially depleted silicon surface barrier detector, both the energy spectrum and total emission of an x-ray source have been accurately measured. By coupling these detectors with a custom PROTO-XRD x-ray source with interchangeable cathodes, accurate characterizations of Θ(E) for filters of varying materials and thicknesses have been obtained. The validity of the technique has been confirmed by accurately reproducing areal densities for high-purity filters with known x-ray transmission properties. In this paper, the experimental setup is described and the results of absorption calibrations performed on a variety of different filters are presented.

Radiological baseline around the Barakah Nuclear Power Plant, UAE

Destructive and non-destructive analysis techniques were used to establish a radiological baseline around the Barakah Nuclear Power Plant area in Abu Dhabi, United Arab Emirates. The natural radioactivity concentrations of 238U (226Ra), 232Th and 40K were measured for shore, soil and bottom sediment samples, using gamma spectrometry with a high-purity germanium (HPGe) detector. Alpha spectrometry was used to measure the 234U/238U ratio for some selected samples using a silicon surface-barrier detector. The measured gamma activity concentrations in shore samples are much lower compared to those in soil and bottom samples. The average activity concentrations of 238U (226Ra) are 4.43 ± 1.12, 13.54 ± 4.16 and 4.73 ± 3.01 Bq/kg in shore, soil and bottom sediment samples, respectively. The corresponding values for 232Th are 1.68 ± 0.49, 8.31 ± 3.87 and 1.83 ± 1.67 Bq/kg, and those for 40K, are 106.30 ± 50.68, 349.72 ± 107.16 and 105.23 ± 130.14 Bq/kg. The 234U/238U activity ratios span a wide range from 0.59 to 2.24, indicating a system where the daughter/parent is out of secular radioactive equilibrium. The hazard parameters, radium equivalent and absorbed dose rates, showed low levels compared to the world average level reported by the UNSCEAR in 2000. The estimated activity concentrations in this study were lower than the world average values and lower than the levels reported in nearby countries.

PADC response to 0.3 - 3 MeV protons

Two types of Poly-Allyl-Diglycol Carbonate, the Neutrak and PN3 were investigated using track diameter distribution induced by the monoenergetic protons with energies in the range of 0.3 to 3 MeV. The energies and intensities were controlled by a silicon surface barrier detector and a nickel scattered foil placed in a 4 MV Van der Graaf accelerator. After different etching times, the etch track-sizes were scanned and measured with the optical microscope. PN3 and Neutrak track diameter responses to protons were measured, plotted, and discussed as a function of energy.

Measurement of differential cross sections of deuteron elastic scattering on 31P for EBS purposes

The 31P(d,d0)31P elastic scattering differential cross-sections were measured, for the first time, in the energy range Ed,lab=900-2400 keV, using a variable energy step, for elastic backscattering spectrometry (EBS) purposes. The measurements were performed at the 5.5 MV TN11 HV Tandem Accelerator of the N.C.S.R. “Demokritos”, implementing a high precision goniometer. The experimental setup consisted of five silicon surface barrier (SSB) detectors, placed at the laboratory scattering angles between 130° and 170° (in steps of 10°). The target used was a thin GaP layer evaporated on a self-supporting carbon foil. To validate the obtained results, benchmarking measurements were performed, using a polished GaP crystal. The determined cross-section datasets are compared with the corresponding ones using Rutherford’s formula, and similarities and discrepancies will be discussed and analyzed.

Stopping Power of Alpha Particles in Helium Gas

The stopping power and the range of alpha particles emitted from Am-241 source has been investigated in helium gas at different pressures of 0 to 1 bar, using surface barrier silicon detector in the large vacuum chamber. The energy loss has also been obtained at variable distances from 2 to 8 cm. It is observed that as the pressure in a large vacuum chamber increases, the energy loss of the alpha particle decreases. The measured energy loss of alpha particles at lower pressure of 0 bar is less, but at higher pressure of 1 bar is more. As expected from Bethe --- Bloch formula, the stopping power of charged particle in helium gas at different pressure was found to increase significantly when pressure is increased. The measured value of stopping power and range were compared with SRIM and theoretical value. The experimental value of stopping power and range was found to be very close to the SRIM and theoretical value. Then, the measured value of range was compared with experimental using the Bragg --- Kleeman's rule

Double-differential cross section measurement with low threshold detector for proton production induced by several tens of MeV protons

We have developed a low threshold detector consisting of Bragg curve counter (BCC), two siliconsurface barrier detectors (SSDs) and BGO scintillator to obtain experimental double-differential cross section (DDX) data for low energy proton production. Since the BCC offers advantage of self particle identification capability and a few μm-thick entrance window, protons produced by nuclear reactions down to 1 MeV have been identified. The capability of the detector is demonstrated in measurements using 70-MeV protons. Measured spectra are compared with calculation results of intra-nuclear cascade (INC) plus evaporation models and nuclear data library.

A method to optimize mass discrimination of particles identified in $$\Delta E$$–E silicon surface barrier detector systems

In several experiments, a system composed by two surface barrier detectors, one thin and one thicker, is used to identify the charge of a nucleus that is detected in this system. The nucleus loses part of its energy ($$\Delta E$$) in the thin detector and the remaining part (E) is left in the thick one. Since the energy loss depends on the charge, this process allows the identification of the nuclear charge. The energy loss also depends on the mass of the particle, but with a lower degree of sensitivity. Therefore, the identification of the nuclear mass is much more difficult. In this paper, we present a method to treat the data in order to optimize the mass discrimination of particles detected in $$\Delta E$$–E systems.

Low-energy-threshold detector for measuring proton spectra at several tens of MeV using Bragg curve spectroscopy

We have developed a low-energy-threshold detector comprising a Bragg curve counter (BCC), two silicon-surface barrier detectors, and a bismuth germanate scintillator to obtain experimental double-differential cross section (DDX) data on (p,p′x) reactions for incident energies of several tens of MeV. The BCC can identify particles by itself and can do so for protons down to 1 MeV. The developed detector is used to measure the DDXs of (p,p′x) reactions for incident proton energies of 40 and 70 MeV at 15–150°. The minimum energy in the DDX data is 1.3 MeV, which gives spectra of emitted particles in the whole energy range. The resultant DDXs are compared with results calculated using intranuclear cascade plus evaporation models. Below 10 MeV, the calculation results agree reasonably with measured data for the natC(p,p′x), 27Al (p,p′x), and natCu(p,p′x) reactions, but they disagree regarding energy and angular dependence for the 197Au(p,p′x) reaction.

Electrostatic separator as a source of low energy protons (32 keV – 400 keV) on Van de Graaff accelerator

IEAP of CTU operates a Van de Graaff accelerator (VDG) that provides protons and light positively charged particles with energy in the range 0.3 MeV/u–2.3 MeV/u. The purpose of this article is to describe the electrostatic separator that enables to obtain protons with the energy lower than 0.3 MeV. We let the beam of protons with the energy 1.0 MeV impact to tungsten target. The Rutherford scattering take place on the target, scattered protons then enter the electrostatic separator. Applying different high voltage between quarter-circular electrodes of the separator, we selected the energy of protons that pass the separator. We used the electrostatic separation because the control over the high voltage is simple and efficient. For the measurement of proton energy, we used the Silicon Surface Barrier Detector Ortec. We proved that the electrostatic separator can provide protons with adjustable energy from 32 keV to 400 keV, FWHM is in the range 13 keV–19 keV. The separator extends possibilities of the VDG usage. In our further research, we intend to focus on investigation of the profile of the beam getting out of the separator using a pixel detector to obtain information on 3D distribution of the beam energy.

Junction edge passivation study of silicon surface barrier detectors using organic films deposited by L–B technique

A new technique to passivate silicon surfaces using \(\hbox {SnO}_{2}\) films, produced by decomposing organic films of the octadecylamine–stannate complex, deposited by the Langmuir–Blodgett (L–B) technique, has been attempted to fabricate silicon surface barrier detectors. This method of passivation is relatively simpler and can be carried out at a much lower temperature as compared to the usual passivation method of the silicon surface by growing the \(\hbox {SiO}_{2}\) layer on it. Also, the passivating layer of \(\hbox {SnO}_{2}\) produced in this new method has a good shelf-life. The detectors fabricated with a passivating layer of \(\hbox {SnO}_{2}\) were subsequently tested for I–V, alpha spectrum and long-term performance.

Measurement of differential cross sections of deuteron elastic scattering on 31P for EBS purposes

The differential cross sections of deuteron elastic scattering on 31P were determined in the present work for the first time, in the projectile energy range Ed,lab = 900–2400 keV (in energy steps of ~10–30 keV), suitable for analytical purposes. The measurements were performed at the 5.5 MV TN11 HV Tandem Accelerator of N.C.S.R. “Demokritos”, Athens, Greece. The experimental setup consisted of five silicon surface barrier (SSB) detectors, placed at the angles between 130° and 170° (in steps of 10°) in a high-precision goniometer. The implemented target was a thin GaP layer evaporated on top of a thin carbon foil. The obtained differential cross-section datasets were benchmarked against a polished GaP crystal and the deviations from the corresponding ones using Rutherford’s formula will be discussed and analyzed.