Surface Barrier Detector Research Articles

ESTUDIO ESPACIAL DEL CARBONO ELEMENTAL PRESENTE EN LA FRACCIÓN RESPIRABLE DE LAS PM2.5 MEDIANTE ESPECTROMETRÍA DE RETRODISPERSIÓN DE RUTHERFORD EN LA ZONA METROPOLITANA DEL VALLE DE TOLUCA

Carbon originates compounds that are characterized by having atoms linked to other elements in their structure, such as oxygen, hydrogen and nitrogen. Many of them are very useful for living beings; however, others such as monoxide and carbon dioxide are considered of high risk for the populations that inhale them, in addition to their impact on climate change. Therefore, monitoring carbon concentrations in the atmosphere is vital. This research aims to determine the presence and concentration of elemental carbon in suspended particles with aerodynamic diameter equal to or less than 2.5 µm by means of the backscattering technique of Rutherford. For this, 10 samples were collected at six sites in the Toluca Valley Metropolitan Area during the sampling campaign (November 2016-November 2017) and analyzed with the Van de Graaff tandem accelerator. A proton beam was used, with energy of 2.5 MeV, which collided elastically with the atoms in the sample (target), being dispersed at a certain angle and at an energy, characterizing the mass of the dispersing center. The particles thus dispersed were registered by a surface barrier detector, obtaining an energy spectrum. The spectrum analysis was done with the SIMNRA software.

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.

Schottky barrier height inhomogeneity in 4H-SiC surface barrier detectors

Schottky barrier height of the diodes prepared on Au/Ni/4H-SiC for surface barrier detectors were studied by electrical methods of I-V and C-V measurements. Analysis of three parameters – barrier height, ideality factor and series resistance of the prepared structures showed that it was not possible to fit in the experimental curves accurately enough with an assumption of one sharp barrier height. The structures were analyzed consecutively by the methods which assumed barrier height inhomogeneity in the diodes. Two types of algorithms were used. The first one assumed that the diode patches were practically electrically independent and each one had its own series resistance. The second approach supposed one common resistance for all the diode patches. It was shown that by the assumption of independent non-interacting diode patches much better fit in experimental I-V curves was possible that was also in accordance with the fact that the diodes were prepared on highly resistive semiconductor substrates.

Neutron depth profiling using the reactions 10B (n,α)7Li and 6Li(n,α)3H induced by thermal neutrons

Samples like p-type silicon and metallic glasses containing boron, were taken and used as target to induce the reaction 10B (n,α)7Li. In addition, samples containing lithium were also irradiated with thermal neutrons to induce 6Li (n,α)3H reaction. The alpha particles emitted through the reactions lose energy while traversing through the sample from point of emission to the surface and can be detected using a surface barrier detector. The out coming alpha particle spectrum can give the depth profile of boron or lithium atoms in the sample, if the energy loss of alpha particle within the matrix is known.

A multipurpose set-up using keV ions for nuclear reaction analysis, high-resolution backscattering spectrometry, low-energy PIXE and in-situ irradiation experiments

A new chamber for material analysis and modification using energetic ions with primary particle energies in the keV regime was developed at the single stage 350 kV high-current Danfysik implanter at the Tandem Laboratory, Uppsala University. The experimental set-up allows for 11B and 18O depth profiling by Nuclear Reaction Analysis using the 11B(p,α0)8Be and 18O(p,α)15N nuclear resonances at 163 keV and at 151 keV, respectively. Additionally, a surface barrier detector with a cryogenic assembly enables High-Resolution Backscattering Spectrometry with average resolution ≈4 keV FWHM for protons. A silicon drift detector enables Low-Energy Particle Induced X-ray Emission analysis for elements with low atomic number (Z ≥ 8). The available instrumentation of the chamber assembly with its specifications are described in details with a series of applied and fundamental benchmark studies, together with some suggestions for future applications.

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.

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.

A finite element simulation of transition-edge sensor for measuring kinetic energy of fission fragments

It is necessary to accurately measure the kinetic energy of fission fragments when using the Time-Of-Flight method to determine the mass of fission fragments. The ionization chamber and the Au-Si surface barrier detector are conventional kinetic-energy detectors, but their energy resolution is not sufficient to achieve a mass resolution of 1 amu. The Transition-Edge Sensor (TES) is a cryogenic calorimeter that can be used to measure the kinetic energy by measuring the temperature variation induced by the energy of the incident particle, with a typical resolution of 0.02% of TES detector can be achieved[1]. In this article, we designed a TES to measure the kinetic energy of fission fragments, and the signals of this TES with different incident particle positions, kinetic energy, and thermal conductivity were simulated using ANSYS. Therefore, we verified the feasibility of the TES and improved the count rate of the TES to 100cps.

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.

L-shell X-ray production cross sections of Ag and Au induced by carbon ions between 2 MeV and 5 MeV

In this work, we experimentally determined Ag and Au L-shell X-ray production and ionization cross sections, induced by 2–5 MeV carbon ions. The experiment was performed using the standard measurement setup already used to measure M-Shell X-ray production cross sections. Ag and Au thin targets, were used to measure L-shell X-ray spectra with Si(Li) and SDD X-ray detectors simultaneously with backscattered carbon ions from the targets by surface barrier detector. Experimental values are compared to the data available in the literature, as well as to the theoretical predictions of PWBA, ECPSSR and ECUSAR models. The analysis of data shows that the ECUSAR predictions are good at low carbon ion energies while the ECPSSR and PWBA predictions agree at the higher incident energies.

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.

Nuclear Reactions under Irradiation of Deuterated Structures by X Rays

Measurements of emission from nuclear reaction products (neutrons and protons) have been carried out appearing in the deuterated structures of textured CVD diamond, palladium, titanium, and zirconium under irradiation with a beam of X rays using independent methods (neutron detector based on He-3 counters, Si surface-barrier semiconductor detectors and CR-39 track detector). The possibility of enhancement of both DD reaction and multi-particle deuterium fusion by the beam of X rays with energy ranging 20–30 keV in solid deuterated targets has been established. Analysis of X-ray fluorescence spectra of the target bombarded by beams of ions has revealed “additional” peaks, the occurrence of which cannot be related to any of the known elements, and requires separate study.

Testing of a Prototype Detector of Heavy Charged Particles Based on Diamond Epitaxial Films Obtained by Gas-Phase Deposition

The results of testing a prototype of a surface-barrier detector of charged particles based on single-crystal epitaxial layers of diamond are presented. Diamond films with p-type conduction with a boron concentration of (4–8) × 1014 cm–3 65 μm thick were grown using gas-phase deposition on heavily doped diamond substrates grown at high pressure and high temperature. A 17 mm2 Schottky barrier was formed by sputtering Pt with a thickness of 30 nm. When irradiated from the 238Pu α-source (the 5.499 keV line) a detector with an external bias of 90 V demonstrated a charge collection efficiency close to 100% and a FWHM high energy resolution of 0.56%. The obtained energy resolution is at the level of standard silicon detectors.

Measurement of the D2 amount in ICF targets by proton-deuterium scattering

A proton-deuterium scattering coincidence detection system (PDS) was established in Fudan University to measure D2 amount in Inertial Confinement Fusion (ICF) targets. ICF targets with a diameter of a few hundred microns were scanned with proton microbeam. Recoiled D atoms and scattered proton atoms were detected by two surface barrier detectors which were placed at 43.0° and 66.7° to the beam direction. A piece of deuterated polystyrene thin film (C8D8 film) was prepared as a reference sample. By the calibrated PDS measurement, the D2 amount in the ICF target was estimated.

The radiobiology beam line facility at the Centre for Ion Beam Applications, National University of Singapore

A new beam line facility dedicated to investigations into the radiobiology of biological single cells has been constructed at the Centre for Ion Beam Applications, National University of Singapore. This facility, which has a horizontal layout, has some novel features including post lens magnetic ion deflection and scanning and provision for a diamond exit window and confocal fluorescence microscope for high performance online investigations.The radiobiology facility uses a system of Oxford Microbeam compact magnetic quadrupole lenses enabling high demagnifications (up to 123 × 51) at the cell plane, and a relatively short lens to cell distances (22.5 cm). Beam optics and SRIM calculations have indicated a theoretical design performance of up to 450 nm for the proton spot size at the cell surface.To measure the spatial resolution of the proton beam at the cell position, we positioned a gold calibration grid inside the external cell chamber at a position normally occupied by cells. Preliminary results were obtained by scanning a 2 MeV focused beam over a grid and using a surface barrier detector to construct a STIM image of the grid we have measured an in-air spot size of sub-500 nm at the cell position.In this paper, the design of the new radiobiology beam line, preliminary results of resolution tests, as well as presenting first investigations into the damage caused by focused proton beam irradiation of human liver cancer cells by detecting DNA damage markers gamma-H2AX and 53BP1.

236U identification in the new AMS beamline at the TANDAR accelerator

236U (T1/2 = 23 My) is an excellent monitor for nuclear contamination in the environment. Indeed, spent nuclear fuels present isotopic ratios 236U/238U several orders of magnitude higher than natural samples. 236U also provides a useful fingerprint to identify and trace nuclear material for safeguards purposes. Here we describe a new beamline for the discrimination of 236U using the accelerator mass spectrometry (AMS) technique. This system comprises a Wien velocity filter and a 6.7 m long time-of-flight (ToF) path with a focusing quadrupole. The ToF is determined by a time zero detector and a surface barrier detector, which also provides an energy measurement. The capability of the system to discriminate 236U from the much more abundant isotopes 235U and 238U is shown. While sensitivity values of 236U/238U∼ 10−8 were achieved, ongoing works aim to improve this performance.

The determination of the astrophysical S-factor of the direct 18O(p,$\gamma$)19F capture by the ANC method

The depletion of 18O via the $(\mathrm{p},\gamma)$ capture competes with the $(\mathrm{p}, \alpha)$ capture during the CNO cycles in AGB stars. Despite the fact that the $(\mathrm{p}, \alpha)$ capture is dominant, the $ (\mathrm{p}, \gamma)$ can play an important role in mixing stages of the AGB star evolution. Here, we attempt to determine the astrophysical S-factor of the direct part of the 18O(p,$\gamma$)19F capture by the indirect method of asymptotic normalization coefficients (ANC). We measure the differential cross section of the transfer reaction 18O(3He, d)19F at a 3He energy of 24.6 MeV. The measurement was performed on the cyclotron of the CANAM infrastructure of NPI in Řež, Czech Republic, with the gas target consisting of the high-purity 18O (99.9%). The reaction products were measured by eight $ \Delta E$-E telescopes composed of thin and thick silicon surface-barrier detectors. The parameters of the optical model for the input channel were deduced by means of the code ECIS and the analysis of transfer reactions to 12 levels of the 19F nucleus up to 8.014 MeV was made by the code FRESCO. The deduced ANCs were then used to specify the direct contribution to the 18O(p,$\gamma$)19F capture process and were compared with the mutually different results of two works.

Dosimetry and characterization of a 25-MeV proton beam line for preclinical radiobiology research.

With the increase in proton therapy centers, there is a growing need to make progress in preclinical proton radiation biology to give accessible data to medical physicists and practicing radiation oncologists. A cyclotron usually producing radioisotopes with a proton beam at an energy of about 25MeV after acceleration, was used for radiobiology studies. Depleted silicon surface barrier detectors were used for the beam energy measurement. A complementary metal oxide semiconductor (CMOS) sensor and a plastic scintillator detector were used for fluence measurement, and compared to Geant4 and an in-house analytical dose modeling developed for this purpose. Also, from the energy measurement of each attenuated beam, the dose-averaged linear energy transfer (LETd ) was calculated with Geant4. The measured proton beam energy was 24.85±0.14MeV with an energy straggling of 127±22keV before scattering and extraction in air. The measured flatness was within±2.1% over 9mm in diameter. A wide range of LETd is achievable: constant between the entrance and the exit of the cancer cell sample ranging from 2.2 to 8keV/μm, beyond 20keV/μm, and an average of 2-5keV/μm in a scattering spread-out Bragg peak calculated for an example of a 6-mm-thick xenograft tumor. The dosimetry and the characterization of a 25-MeV proton beam line for preclinical radiobiology research was performed by measurements and modeling, demonstrating the feasibility of delivering a proton beam for preclinical invivo and invitro studies with LETd of clinical interest.

Extending the UoA Nuclear Physics Laboratory capabilities with low-γ and α spectrometers

In this project the steps taken toward the characterization, calibration and testing of two spectroscopy stations are presented. The first one is suitable for alpha spectroscopy, consisting of a large-window silicon surface barrier detector (SSB), a goniometric arm and a movable multiple source-holder inside a dark vacuum chamber. The second station contains two small-size, thin-window NaI(Tl) scintillators, and it is suitable for low-γ ray spectroscopy.