Passivated Implanted Planar Silicon Research Articles

New-designed measurement device for radon and thoron activity concentration based on gas direct detection

A new-designed measurement device for radon and thoron activity concentration is developed based on gas direct measurement to support their in-situ calibration. It consists of a 2000 mm2 Passivated Implanted Planar Silicon (PIPS) detector, a Multi-Channel Analyzer (MCA), a Micro Controller Unit (MCU), and a small electrostatic chamber with a volume of nearly 23 ml. The device records those alpha particles emitted from radon and thoron gas, and the detection efficiency and the crosstalk factor of 218Po/216Po are determined by Monte Carlo simulation. Measurement results have been compared with AlphaGUARD DF2000 in pure radon and thoron environments, respectively. Results show that the measurement results of the devices and the reference monitor agree well with each other, with an average relative deviation of 0.48% for radon gas from about 3300 Bq/m3 to 38 kBq/m3 and -3.25% for thoron gas from about 25 kBq/m3 to 70 kBq/m3. Uncertainty assessment has also been done, and a relative system uncertainty of radon is about 6.8%, while that of thoron is nearly 7.3%.

A comparison of alpha-particle and gamma-ray spectrometry methods for determination of 235U, 238U and 226Ra activity concentration in samples of coal, slag and fly-ash

In order to compare alpha-particle and gamma-ray spectrometry, the activity concentrations of 235U, 238U and 226Ra in samples of coal, slag and fly-ash from the thermal power plant “Nikola Tesla A”, Serbia, were determined by these two methods. Methods were compared and discussed from the point of view of its precision, difficulty to apply and complexity. Gamma-ray spectrometry was performed with HPGe (High Purity Germanium) spectrometer, while alpha activity was measured by PIPS (Passivated Implanted Planar Silicon) detector. For the alpha-particle spectrometry, the chemical procedures applied were chromatographic resin extraction for uranium isotopes and micro-coprecipitation for 226Ra. Thin alpha sources were prepared by electrodeposition and filtration through polypropylene membrane filter for uranium determination, while filtration technique was performed for radium sources. For the evaluation of the statistical difference between individual measurement results obtained by application of two methods Z - test was used. In order to evaluate the difference between two methods used, paired samples t-test and F-test were applied. Results show that there is no statistical difference between two methods used and that gamma-ray spectrometry is a valid alternative to time consuming alpha spectrometry.

Accuracy comparison of fitting function applied to air-borne alpha detection spectrum

The ability to detect airborne alpha particles in real time could greatly enhance the safety of workers in radioactive environments. To assist in the development of an air-borne detection system, this study sought to overcome the difficulties in spectral analysis caused by the strong interaction of alpha particles with matter. Three modified Gaussian fitting functions were applied to a radon progeny alpha spectrum and cross-referenced to counteract the overlap phenomenon produced by low-tailing of the alpha peak. The radon progeny alpha spectrum was derived using MCNP6 and a PIPS (passivated implanted planar silicon) detector. The radionuclides were determined pertaining to two cases, where case 1 included 220Rn, 216Po, and 212Bi, and case 2 included 222Rn and 218Po. The RMS (root mean square) and reduced chi-square values were compared for accuracy. The convolution of an exponential low-energy tail with a Gaussian distribution equation provided 6.68% lower relative error than when two Gaussian distribution functions were combined according to centroid conditions. The relative error was 0.84% lower than with a Gauss function, indicating a spectrum-peak Gaussian distribution. By constructing the algorithm using this equation, it was possible to obtain high-accuracy analysis data even with low-resolution spectrums in the air.

Spectral resolution evaluation by MCNP simulation for airborne alpha detection system with a collimator

In this study, an airborne alpha detection system, which consists of a passivated implanted planar silicon (PIPS) detector and an air filter, was developed. A collimator applied to the alpha detection system showed an enhancement in resolution and a degradation in detection efficiency. The resolution and detection efficiency were compared and analyzed to evaluate the performance of the collimator. Thus, the resolution was found to be more important than the efficiency as a determining factor of the detection system performance, from the viewpoint of radionuclide identification. The performance was evaluated on three properties of the collimator: hole shape, hole length, and the ratio between the hole and frame pitches. From the hole shape performance evaluation, a hexagonal collimator showed the highest resolution. Further, the collimator with a hole pitch of 14 mm was found to have the highest resolution while that with a frame pitch of 4–6 mm (i.e., 1.2–1.4 times longer than the hole pitch) showed the highest resolution.

Characterizing High-Energy Ion Beams With PIPS Detectors

The energy deposited by heavy-ion beams was measured using a passivated implanted planar silicon (PIPS) detector in different facilities. Ion beams at ultrahigh energy lead to the formation of a second, unexpected peak in the deposited energy spectrum at slightly higher energy, in addition to the expected primary peak. Monte Carlo simulations are used to shed light on the origin of this phenomenon and the underlying physical mechanisms. The importance of accounting for secondaries' production in the packaging materials of the diode and the mechanisms at play are highlighted in the discussion of the results.

Optimization of airborne alpha beta detection system modeling using MCNP simulation

Abstract An airborne alpha beta detection system using passivated implanted planar silicon (PIPS) detector was modeled with the MCNP6 code and its resolution and detection efficiency were analyzed. Simulation of the resolution performed using the Gaussian energy broadening (GEB) function showed that the full width at half maximum (FWHM) of 35.214 keV for alpha particles was within 34–38 KeV, which is the FWHM range of the actual detector, and the FWHM of 15.1 keV for beta particles was constructed with a similar model to 17 keV, which is the FWHM range of an actual detector. In addition, the detection efficiency and the resolution were simulated according to the distance between the detector and the air filter. When the distance was decreased to 0.2 cm from 0.8 cm, the efficiency of the alpha and beta particles detection decreased from 5.33% to 4.89% and from 5.64% to 4.27%, respectively, and the FWHM of the alpha and beta particles improved from 40.9 KeV to 29.84 keV and 25.76 keV–13.27 keV, respectively.

Simulation of the response of a PIPS detector using GEANT4 code

The main objective of this work is to simulate a PIPS (Passivated Implanted Planar Silicon) detector response by Monte Carlo method and its validation with experimental results. Specifically, we have calculated via simulation the counting efficiency and the energy resolution of a PIPS detector. In order to do this, we have developed a Geant4 application that includes the most relevant physics processes, the geometry, composition and radioactive content of the sample, and the geometry of the PIPS detector and the vacuum chamber. However, some parameters involved in the Monte Carlo simulation are unknown (detector dead layer or sample thickness), and it was mandatory to estimate them through comparisons between experimental and calculated detector responses in order to obtain an accurate simulation of the PIPS detector.To show the validity of the simulated results, we present a comparison of the simulated alpha particle energy spectrum with the experimental one from a uranium dioxide pellet.

239Pu alpha spectrum analysis based on PIPS detector response function and variations with vacuum and distance

Effect factors of the absorption of the source, air, entrance window, and dead layer of a detector must be considered in the measurement of monoenergetic alpha particles, along with statistical noise and other factors that collectively cause the alpha spectrum to exhibit a well-known low-energy tail. Therefore, the establishment of an alpha spectrum detector response function from the perspective of a signaling system must consider the various factors mentioned above. The detector response function is the convolution of an alpha-particle pulse function, two exponential functions, and a Gaussian function, followed by calculation of the parameters of the detector response function using the weighted least-squares fitting method as proposed in this paper. In our experiment, 239Pu alpha spectra were measured by a high-resolution, passivated implanted planar silicon (PIPS) detector at 10 levels of vacuum and 10 source-detector distances. The spectrum-fitting results were excellent as evaluated by reduced Chi-square (χ 2) and correlation coefficients. Finally, the variation of parameters with vacuum level and source-detector distance was studied. Results demonstrate that σ, τ1, and τ2 exhibit no obvious trend of variation with vacuum in the range 2000–20,000 mTorr, and at a confidence level of 95%, the values of τ1 and τ2 decline in a similar fashion with source-detector distance by the power exponential function, while the value of σ declines linearly.

Towards measuring the ground state hyperfine splitting of antihydrogen – a progress report

We report the successful commissioning and testing of a dedicated field-ioniser chamber for measuring principal quantum number distributions in antihydrogen as part of the ASACUSA hyperfine spectroscopy apparatus. The new chamber is combined with a beam normalisation detector that consists of plastic scintillators and a retractable passivated implanted planar silicon (PIPS) detector.

Investigation of X-ray spectral response of D-T fusion produced neutron irradiated PIPS detectors for plasma X-ray diagnostics

This paper describes the fusion-produced neutron irradiation induced changes in the X-ray spectral response of commercially available Passivated Implanted Planar Silicon (PIPS) detectors using the accelerator based D-T generator. After 14.1 MeV neutron irradiation up to a fluence of 3.6× 1010 n/cm2, the energy resolution (i.e. FWHM) of the detectors at room temperature is found to degrade by about 3.8 times that of the pre-irradiated value. From the X-ray spectral characteristics, it has been observed that the room temperature spectral response of PIPS detectors is too poor even at low neutron fluences. Irradiation is also carried out with Am-Be neutron source for studying the effect of scattered neutrons from the reactor walls on the detector performance. Comparative studies of the damage caused by 14.1 MeV neutrons and Am-Be source produced neutrons at the same neutron fluence are carried out by analyzing the irradiated detector characteristics. The degradation in the energy resolution of the detectors is attributed to the radiation induced changes in the detector leakage current. No considerable changes in the full depletion voltage and the effective doping concentration up to the neutron fluence of 3.6× 1010 n/cm2, are observed from the measured C-V characteristics. Partial recovery of the neutron irradiated detector characteristics is discussed.

Numerical Simulation of 14.1 MeV Neutron Irradiation Effects on Electrical Characteristics of PIPS Detector for Plasma X-Ray Tomography

Numerical simulation studies of D-T fusion produced neutron irradiation-induced changes in the electrical characteristics of commercially available Passivated Implanted Planar Silicon (PIPS) detectors (with ρ = 7.4 kΩcm) are carried out using a commercial device simulator for plasma X-ray tomography in nuclear fusion reactors. The proposed radiation damage model is validated by comparing with the experimental data of 14.1 MeV neutron irradiated PIPS detector for fluence up to 3.6 ×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> n/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The possible changes in the irradiated detector characteristics for higher neutron fluence levels are predicted. Furthermore, the simulated results for higher neutron fluence are validated by comparing with the reported experimental results. The probable deterioration in the X-ray energy response of PIPS detectors is analyzed from the changes in the electrical characteristics due to neutron irradiation. The simulated investigations are also repeated for detectors with different resistivity substrates (4 kΩ cm, and 300 Ωcm) and thin detector structures (100 μm). From the simulation studies, the possible use of the silicon detectors for the plasma X-ray tomography diagnostics is discussed.

High-resolutionαand electron spectroscopy ofCf98249

$\ensuremath{\alpha}$-particle spectra of $^{249}\mathrm{Cf}$ have been measured with a double-focusing magnetic spectrometer and with passivated implanted planar silicon (PIPS) detectors. The conversion-electron spectra of $^{249}\mathrm{Cf}$ have been measured with a cooled Si(Li) detector and with a room-temperature PIPS detector. Precise energies of $\ensuremath{\alpha}$ groups in the decay of $^{249}\mathrm{Cf}$ have been measured with respect to the known energy of $^{250}\mathrm{Cf}$. In addition, $\ensuremath{\alpha}$-electron, $\ensuremath{\alpha}\text{\ensuremath{-}}\ensuremath{\gamma}$, and $\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\gamma}$ coincidence measurements were also performed to determine the spin-parity of the previously known 643.64-keV level. From electron intensities, conversion coefficients of transitions in the daughter $^{245}\mathrm{Cm}$ have been determined. The measured ${L}_{3}$ conversion coefficients of the 333.4- and 388.2-keV transitions are found to be in agreement with the theoretical conversion coefficients for pure $E1$ multipolarity. On the other hand, the $K,{L}_{1}+{L}_{2},M$, and $N$ conversion coefficients are approximately twice the theoretical values for pure $E1$ transitions. These measurements indicate anomalous $E1$ conversion coefficients for the 333.4- and 388.2-keV transitions, as has been pointed out in earlier measurements. The measured conversion coefficient of the 255.5-keV transition gives an $M1$ multipolarity for this transition which establishes a spin-parity of 7/${2}^{\ensuremath{-}}$ and the 7/${2}^{\ensuremath{-}}[743]$ single-particle assignment to the 643.64-keV level.

Towards Alpha Radiation Detection in Aqueous Solution: VLSI Technology Development for Diamond-Silicon Hybrid Sensors

ABSTRACTIn the presented work, we have developed VLSI technology processes for new prototype sensors based on the synthesis of boron doped nanocrystalline diamond (B-NCD) and silicon based commercial detectors. The process is based on commercial passivated implanted planar silicon (PIPS) devices of PD450 and CAM450 types (CANBERRA). A layer of B-NCD of several hundred nanometers thickness and boron concentration up to 1021 atoms/cm3 is grown on the SiOx passivation layer in an ellipsoidal plasma enhanced chemical vapor deposition (PECVD) reactor at temperatures from 520-750°C, in hydrogen atmosphere. . The diamond electrode is dry chemically structured and aluminum electrodes are realized before mounting in a three-fold housing for measurements in aqueous solution. The prototype sensors show an alpha spectroscopy resolution of 100 keV for 241Am electroprecipitated from liquid solution.

Method of “Active Correlations” for DSSSD detector application

Real-time PC based algorithm is developed for DSSSD (Double Side Silicon Strip Detector) detector. Brief description of the detection system is also presented. Complete fusion nuclear reaction nat Yt + 48 Ca → 217 Th is used to test this algorithm at 48Ca beam. Example of successful application of a former algorithm for resistive strip PIPS (resistive strip Passivated Implanted Planar Silicon) detector is presented too.

Room-temperature electron spectroscopy of 239Pu and 240Pu

Passivated, implanted, planar silicon (PIPS) detectors have been used for the measurement of electron spectra. The commercially available PIPS detectors, available in thicknesses of 100μm, 300μm, and 500μm, have an energy resolution (FWHM) of ~2.2keV, which is essentially the same as that of PIN diodes. Alpha and electron spectra of mass-separated 239Pu and 240Pu sources have been measured with a 300-μm thick PIPS detector and the electron to alpha ratios for the conversion lines of the 51.62- and 45.24-keV transitions have been determined. A procedure has been developed to determine the amount of 239Pu and 240Pu in a mixed source. The α-particle emission rate of the mixed source is measured, which is the sum of individual rates. From the electron spectrum of the mixed source, measured with the same setup as the alpha spectrum, the rates of 239Pu electron lines are determined. Using the electron rate of the 239Pu line and the electron to alpha ratio measured for the pure source, the α-particle emission rate of 239Pu is determined. The difference from the total α-particle emission rate gives the α-particle emission rate of 240Pu. In addition, electron intensities and conversion coefficients of the 239Pu and 240Pu transitions have been measured.

Measurement of (n,α) reactions on 147Sm and 149Sm using a lead slowing-down spectrometer

The lead slowing-down spectrometer (LSDS) at Rensselaer Polytechnic Institute (RPI) was used to extend previous measurements of the (n,α) cross section on 147Sm and perform measurements on 149Sm over the energy range 0.1eV–10keV. A compensated detector based on passivated implanted planar silicon (PIPS) detectors was constructed. Signals from two detectors were combined in opposite polarity and digitized providing a single detector capable of discriminating against capture γ's and “γ-flash” while preserving the discrete signals produced by α events and providing a simultaneous background measurement. Extrapolating the results predicts a 0.3±0.3mbarn and 11.5±1.1mbarn thermal neutron (n,α) cross section for 147Sm and 149Sm, respectively. This measurement provides new information on (n,α) reaction cross sections. The method of measuring neutron induced charged particle emission cross sections presented here can be expanded to more isotopes of interest to reactor engineers or astrophysicists, as well as to (n,p) reactions.

Monte Carlo simulation of beta radiation response function for semiconductor Si detector

Abstract This paper describes the modeling of the Passivated Implanted Planar Silicon (PIPS) detector for the beta particles response function simulations with the MCNP-5 code. The simulated and measured energy response functions were compared and a good agreement was found in the entire range of energies. The verified model of a PIPS detector was applied in a non-destructive method that determines the activity of beta emitters in the sample with a known geometry and atomic number densities. The procedure for the identification of beta emitters in the samples was also described. Finally, the application of the proposed method for the determination of 137Cs and 90Sr activity in water samples taken from the RA reactor spent fuel storage pools and from the paper filter taken from an air monitor operated during repackaging of spent fuel elements, was presented.

On the comparison of three methods of assessing beam quality for broad beam in vitro cell irradiation

The interaction of charged particles with living matter has recently attracted increasing interest in the field of biomedical applications such as hadron therapy, radioprotection and space radiation biology. Particle accelerators are particularly useful in this area. In vitro radiobiological studies with a broad beam configuration require beam homogeneity. The goal is to produce a dose distribution given to a cell population that is as close to uniform as possible. In this paper, we compare the results of three devices used to assess the beam quality for broad beam irradiation: a passivated implanted planar silicon (PIPS) particle detector, a position-sensitive solid state detector, which is camera-like, and a solid state nuclear track detector (CR39). The first device is a PIPS detector of 300 μm nominal depletion depth and an entrance window with a thickness of about 500 Å. It is collimated with a 0.5 mm aperture and mounted in air on an XY moving table as close as possible to the exit window of the beam line. The second device is a CMOS position-sensitive detector (technological process 0.6 μm AMS CUA), 112 × 112 pixels, with 153 × 153 μm 2 pixel size. It allows the user to rapidly obtain dose uniformity over a surface of 1 × 1 cm 2. During uniformity and dose rate assessment it is placed in air at the PIPS location. For both detectors, beam profile was obtained for various proton fluxes (from ∼5 × 10 4 to 10 6 particles cm −2 s −1). Preliminary tests were made with CR39 using 4 MeV He ++ ions. Results are analysed using Poisson distribution and cell hit probability.

RAPID SCREENING AND ANALYSIS OF ALPHA- AND GAMMA-EMITTING RADIONUCLIDES IN LIQUIDS USING A SINGLE SAMPLE PREPARATION PROCEDURE

A multifaceted radiochemical testing procedure has been developed to analyze a large number of liquid samples and measure a wide range of radionuclides in a short period of time. This method involves a single, unique and fast sample preparation procedure and allows sequential/concurrent determination of analytes with accuracy and precision. The same prepared sample can be selectively analyzed by gross alpha counting, gamma-ray spectroscopy, and alpha spectroscopy. This method is especially attractive in radiological emergency events where analytical data will be needed urgently as a basis for protective action. Given the simplicity and rapidity of the method, it may be suitable for field portable laboratories, which could save time and the cost associated with the transit of samples to a fixed laboratory. A 100 mL aliquot of sample was spiked with ¹³³Ba and ⁵⁹Fe tracers and subjected to a chemical separation procedure using a combined BaSO4 and Fe(OH)3 co-precipitation scheme. Then, the gross alpha-particle activity of the prepared sample was measured with a low-background gas-proportional counter, followed by the analysis of its photon-emitters using a gamma-ray spectroscopy system with high-purity intrinsic Ge detectors. Gamma-ray determination of ¹³³Ba and ⁵⁹Fe tracers was used to assess the chemical recoveries of BaSO4 and Fe(OH)3 fractions, respectively. Selectivity of the radionuclides for co-precipitation with either BaSO4 or Fe(OH)3 components was also investigated. Alpha mass-efficiency curves were derived using ²³⁰Th and ²⁴¹Am standards as alpha-calibration sources. Various mixtures of radionuclides, including ⁵⁴Mn, ⁵⁷Co, ⁶⁰Co, ⁸⁵Sr, ⁸⁸Y, ¹⁰⁹Cd, ¹¹³Sn, ¹³⁷Cs, ¹³⁹Ce, ²⁰³Hg, ²⁰⁹Po, ²²⁶Ra, ²²⁸Ra, ²³⁰Th, ²⁴¹Am, and natural uranium were used in this study. Most were quantitatively assayed with high chemical recoveries. Alpha-isotope identification and assessment of the prepared sample was achieved by alpha spectroscopy using passivated implanted planar silicon (PIPS) detectors. It has been shown that fission products could potentially be captured and analyzed by this method.

Proton beam writing nanoprobe facility design and first test results

A second generation proton beam writing line has been installed at the Centre for Ion Beam Applications at the National University of Singapore. This system features a high demagnification lens system based on compact OM52 lenses with reduced working distance. The system can operate in a variety of high demagnification configurations, including the spaced Oxford triplet and the double-crossover Russian quadruplet. It features an electrostatic scanning system and a new collimator slit aperture design. Here we present the first results with this system operating in a spaced Oxford triplet configuration with a beam focus in one direction down to 20nm. One of the limitations of the current system is the inferior quality of the high-voltage supply driving the electrostatic scanning system. The second focus of this paper is the performance of the new collimator slit aperture design for MeV nanoprobe forming systems. Cylindrically strained electroplated Ni surfaces with a bending radius of 50mm are used as slit edges. An incident molecular beam of 2MeV H2+ ions was used for the slit scattering measurements. Any scattering by the slits resulting in dissociation of the incident molecular beam into 1MeV protons facilitated the measurements of scattered and non-scattered components by the passivated implanted planar silicon (PIPS) detector. The studies showed the expected correlation between the aperture size and scattering. The quality of the beam was satisfactory even for small aperture dimensions with a very small percentage of the beam showing energy loss.