Alpha Particle Data Research Articles

Energy straggling and an experimental investigation of Bragg's rule for 241Am alpha particles in air and its constituents

We present here energy straggling data for alpha particles from 241Am in air and its constituents, and an experimental investigation of Bragg’s rule. High resolution alpha spectroscopy system from ORTEC with an ultra-thin source, an ion implanted thin entrance window detector of small diameter, and state of the art counting electronics with a 4096 MCA is used. In the controlled experimental environment gases of 5N purity are used to measure energy straggling. Measured values are compared with the theoretical predictions of Bohr, Bethe-Livingston, Titeica and Yang et. al. An experimental investigation on using Bragg’s rule to estimate the energy straggling in air from the experimental obtained data of constituents is presented.

Pearson’s chi-squared statistics: approximation theory and beyond

Summary We establish an approximation theory for Pearson’s chi-squared statistics in situations where the number of cells is large, by using a high-dimensional central limit theorem for quadratic forms of random vectors. Our high-dimensional central limit theorem is proved under Lyapunov-type conditions that involve a delicate interplay between the dimension, the sample size, and the moment conditions. We propose a modified chi-squared statistic and introduce an adjusted degrees of freedom. A simulation study shows that the modified statistic outperforms Pearson’s chi-squared statistic in terms of both size accuracy and power. Our procedure is applied to the construction of a goodness-of-fit test for Rutherford’s alpha-particle data.

Neural network prediction of K and L-shell X-ray production cross sections

Abstract The ionization and X-ray production cross section are fundamental parameters in elemental analysis by PIXE technique. Unfortunately no exact general analytical expression exists, from which the interest of this work. In this paper, we apply the neural network technique in the evaluation of the X-ray production cross sections. The calculations are based on Mukoyama’s PWBA data. Our results are compared with experimental data for protons and alpha particles for energies ranging from hundreds KeV to tens MeV.

Alpha particles energy estimation from track diameter development in a CR-39 detector

The slight nonlinearity in temporal development of tracks diameter in CR-39 nuclear track detectors is examined with the aim of attempting to find if such nonlinearity can be directly related to the charged particle energy. Narrowly spaced etching time-diameter experimental data for alpha particles at five energy values and for one additional energy value etched at five different temperatures are obtained. Initial results show good indication that measuring such time-diameter relationship can form a useful energy estimation tool. Good consistency with other independent published results is obtained.

Criticality of Low-Energy Protons in Single-Event Effects Testing of Highly-Scaled Technologies

We report low-energy proton and low-energy alpha particle SEE data on a 32 nm SOI CMOS SRAM that demonstrates the criticality of using low-energy protons for SEE testing of highly-scaled technologies. Low-energy protons produced a significantly higher fraction of multi-bit upsets relative to single-bit upsets when compared to similar alpha particle data. This difference highlights the importance of performing hardness assurance testing with protons that include energy distribution components below 2 MeV. The importance of low-energy protons to system-level single-event performance is based on the technology under investigation as well as the target radiation environment.

Stopping power and energy loss straggling of thin Formvar foil for 0.3–2.7 MeV protons and alpha particles

Stopping power and energy loss straggling data for protons (1H+) and alpha particles (4He+) crossing Formvar thin polymeric foils (thickness of ∼0.3μm) have been measured in the energy range (0.3–2.7)MeV by using the indirect transmission technique. The determined stopping power data were compared to SRIM-2010, PSTAR or ASTAR calculation codes and then analyzed in term of the modified Bethe–Bloch theory to extract the target mean excitation and ionization potential 〈I〉. A resulting value of 〈I〉≈(69.2±1.8)eV was deduced from proton stopping data. The measured straggling data were corrected from surface roughness effects due to target thickness inhomogeneity observed by the atomic force microscopy (AFM) technique. The obtained data were then compared to derived straggling values by Bohr's and Bethe–Livingston's classical theories or by Yang's empirical formula. A deviation of ∼40%–80% from the Bohr's straggling value has been observed for all reported energies, suggesting that the Bohr theory cannot be correctly applied to describe the electronic energy loss straggling process with the used low thickness of Formvar foil. The inner-shell contribution of target electrons to energy loss process is also advanced to explain the observed deviation from experiment in case of He+ ions. Finally, the reliability of Bragg's additivity rule was discussed in case of stopping power and straggling results.

Human Lung Cancer Risks from Radon – Part I - Influence from Bystander Effects - A Microdose Analysis

Since the publication of the BEIR VI report in 1999 on health risks from radon, a significant amount of new data has been published showing various mechanisms that may affect the ultimate assessment of radon as a carcinogen, at low domestic and workplace radon levels, in particular the Bystander Effect (BE) and the Adaptive Response radio-protection (AR). We analyzed the microbeam and broadbeam alpha particle data of Miller et al. (1995, 1999), Zhou et al. (2001, 2003, 2004), Nagasawa and Little (1999, 2002), Hei et al. (1999), Sawant et al. (2001a) and found that the shape of the cellular response to alphas is relatively independent of cell species and LET of the alphas. The same alpha particle traversal dose response behavior should be true for human lung tissue exposure to radon progeny alpha particles. In the Bystander Damage Region of the alpha particle response, there is a variation of RBE from about 10 to 35. There is a transition region between the Bystander Damage Region and Direct Damage Region of between one and two microdose alpha particle traversals indicating that perhaps two alpha particle "hits" are necessary to produce the direct damage. Extrapolation of underground miners lung cancer risks to human risks at domestic and workplace levels may not be valid.

Stopping of ∼0.2–3.4MeV/amu 1H+ and 4He+ ions in polyvinyl formal

Abstract The stopping powers of polyvinyl formal resin for protons and alpha particles have been measured over the energy range ∼(0.2–3.4) MeV/amu with an overall relative uncertainty of less than 2.5% using the ion beam transmission method. The obtained results are discussed in comparison to scarce experimental data from the literature and to values calculated by the SRIM-2008 computer code assuming Bragg-Kleeman’s additivity rule of stopping powers. Departures from additivity attaining ∼5.5% and ∼3.0% for the proton and alpha particle data, respectively, are observed at moderate projectile velocities, increasingly as one evolves towards the stopping power maximum dominated by charge exchange effects. They are presumed to be mainly due to valence structure effects involving the C–H bonds of the studied polymer compound. The less pronounced deviation for alpha particles is probably due to the projectile screening effect that occurs in distant collisions tending to reduce the contribution of valence electrons in the low projectile velocity regime.

Effects of the projectile electronic structure on Bethe–Bloch stopping parameters for Ag

Abstract Energy losses of protons and alpha particles in silver have been accurately measured under the same experimental conditions over the velocity range E lab = ( 0.192 – 2.595 ) MeV/amu using the transmission method. Deduced S ( E ) stopping powers are compared to most accurate ones from the literature, to values generated by the SRIM-2008 computer code and to ICRU-49 compilation. They were analyzed in the framework of modified Bethe–Bloch theory for extracting Ag target mean excitation and ionization potential, I, and Barkas effect parameter, b. Values of ( 466 ± 5 ) eV and 1.20 ± 0.01 for these two parameters were inferred from the proton S ( E ) data while the alpha particle data yielded values of ( 438 ± 4 ) eV and 1.38 ± 0.01 , respectively. The (I, b) stopping parameters thus exhibit opposite variations as the projectile charge increases, similarly as we have found previously for nickel [6] . This can be ascribed only to an effect of the projectile electronic structure at low velocities. The obtained results are discussed in comparison to previous ones reported in the literature.

Adaptive response and human benefit: Part I. A microdosimetry dose-dependent model

Purpose: It is important to evaluate how adaptive response may be of human benefit from the risks of ionizing radiation. The purpose of this work is to develop and apply a microdosimetric dose response model capable of explicitly determining, for broad beam exposures, the threshold and progressive activation of natural spontaneous and radiation damage protective mechanisms associated with adaptive response and other cellular negative response behavior.Materials and methods: A biophysical model was developed quantifying the accumulation of Poisson distributed microdose specific energy hits to cell critical nucleus volumes. The model was applied to the adaptive response data of Wiencke et al., Redpath et al., Azzam et al. and Pohl-Ruling et al. The model was also applied to non-adaptive response data showing dose response reductions below the zero dose natural spontaneous level and to data exhibiting mid-range non-monotonic dose response plateaus.Results: We find good fits of the model to all data. For adaptive response, a significant result is, that only one or two specific energy hits of low linear energy transfer (LET) radiation in the cell nucleus activates the protective mechanisms for both the natural spontaneous and radiation damage. Several data support a dose plateau for radon progeny alpha production of chromosome aberrations in human lymphocytes. Using the model, a bystander factor of about 30 is obtained with the model for high dose rate, in vitro alpha particle data. For low dose rate in vivo, the bystander effect is minimal suggesting for alphas that the bystander effect may be dose rate dependent. There is no evidence of bystander effects in the low LET adaptive response data analysis.Conclusions: The microdosimetry model allows concise determinations of specific energy hits within the cell critical nucleus volume to activate both protective and damage mechanisms. One or two low LET hits can result in reduction of both zero dose natural spontaneous and radiation-induced, carcinogenic causing damage. The model should be useful in comparing in vitro and in vivo broad beam to single track microbeam exposure data. The model is capable of determining, to an accuracy of ± one specific energy hit, the minimum threshold for induction of radioprotective mechanisms – crucial to assessing the potential human benefit of adaptive response and other negative dose response behavior.

Effects of the projectile electronic structure on stopping parameters for nickel

The stopping powers of nickel foils for 1H+, 2H+ and 4He2+ ions have been accurately measured over the energy range E≈(0.166−2.725)MeV/amu. The data were compared to those reported in the literature and to values derived by the SRIM-2003 code. They were analysed in the framework of the modified Bethe–Bloch theory to extract the target mean excitation and ionisation potential, I, and the Barkas effect parameter, b. The values derived from the proton and the alpha particle data are {I=(311.11±2.61)eV, b=1.38±0.01} and {I=(276.12±2.84)eV, b=1.58±0.01}, respectively. They thus show opposite variations of the I and b parameters as the projectile charge increases, presumably due only to the incident ions electronic structure. Besides, the reduced stopping power data for incident deuterons show to be fully consistent with those for protons indicating no effect of the projectile isotopic structure on the target stopping parameters. These results are discussed in comparison with ones reported in the literature.

Stopping powers of havar for 0.63–5.9 MeV protons and 2.6–24 MeV alpha particles

A transmission experiment utilizing thin foil targets has been conducted in order toestablish the stopping powers of the cobalt-base alloy, havar, for 0.6–5.9 MeVprotons and 2.6–24 MeV alpha particles. The basic technique of the novelexperimental method used was to record both the projectile energy and the time offlight while alternating measurements with and without the target in place. Theuncertainties of the proton and alpha particle data sets ranged from 1.4 to 2.3%and 1.1 to 1.5%, respectively. Modified Bethe–Bloch theory was applied to themeasurements in order to ascertain values of the target mean excitation energy(I) and Barkas-effectparameter (b) for each projectile. The extracted values wereI = 304.3 ± 2.4 eV andb = 1.37 ± 0.04 for the case ofprotons, and I = 306.3 ± 2.3 eVand b = 1.47 ± 0.03 for the case ofalpha particles. The I-values are somewhat higher than the additivity-based expectation of 295.7 eV, whereas theb-values are clearly consistent with the expected range of1.4 ± 0.1. The parameter values extracted from the measurements areappraised for compatibility with recently observed trends in values ofI andof b with increasing projectile atomic number.

Microdosimetric one hit detector model for calculation of dose and energy response of some solid state detectors.

A microdosimetric one hit detector model has been applied to calculate dose response, energy response and relative efficiency of thermoluminescent LiF:Mg,Cu,P (MCP-N), CaF2:Tm (TLD-300) and ESR alanine detectors on radiation of different qualities. For each detector type two model parameters, the target size and the saturation parameter, alpha, have been derived. Using those parameters and the microdosimetric distributions in nanometre size targets calculated using Monte Carlo track structure codes TRION and MOCA-14 it was possible to predict a great variety of experimental data for photons, X rays, beta electrons, protons, alpha particles and heavy ions. Due to a good reproducibility of experimental data some solid state detectors might be useful to test biophysical models of radiation action. Furthermore, these models can give some insight into the physics of radiation action in solid state detectors such as the range of charge interaction, energy levels etc.

The microdosimetric one-hit detector model for calculating the response of solid state detectors

The microdosimetric one-hit detector model has been developed and applied to calculate the dose response, energy response and relative efficiency of thermoluminescent LiF:Mg,Cu,P and CaF 2:Tm detectors, and of the free-radical alanine dosimeter, after their exposure to radiation of different quality. The one-hit detector is described by two model parameters: the target diameter, d and the saturation parameter, α. Combining these parameters with microdosimetric distributions in nanometer-size targets calculated using Monte Carlo track structure codes TRION and MOCA-14, it was possible to describe and predict a great variety of experimental data for photon, X-ray, beta-electron, proton, alpha-particles and heavy ion irradiation. Within the framework of this biophysical model of radiation action, some mechanistic insight into the physics of radiation action in solid state detectors can be obtained.

A case history of solar and galactic space weather effects on the geosynchronous communications satellite TDRS-1

Energetic particles of both galactic and solar origin have the potential to cause state changes in memory devices used on-board spacecraft. The particular memory device used in the attitude control system of the Tracking and Data Relay System (TDRS-1) lends itself to the study of this phenomena due to its high susceptibility to such upsets. An eight-year record of TDRS-1 on-orbit upsets reflect the solar cycle variation in galactic radiation as well as radiation enhancements due to solar events. The proton and alpha particle data from the GOES space environment monitor are used to illustrate the radiation environment responsible for these upsets.

Values of modified Bethe–Bloch stopping power parameters for polysulfone extracted from stopping power measurements with light projectiles

Recent measurements of the stopping powers of polysulfone for 0.66–1.74 MeV protons and 1.04–3.20 MeV alpha particles have been analyzed in terms of the modified Bethe–Bloch theory in order to extract values of the parameters characterizing the formalism utilized. Resulting values of mean excitation energy ( I) and Barkas-effect parameter ( b), respectively, were 83.3 eV and 1.05 for proton data, and 81.1 eV and 1.38 for alpha particle data. The lower energy alpha particle data were included by employing a single effective charge parameter ( λ) evaluated at 1.63. The composite weighted value of mean excitation energy, 82.9 eV, lies some 6% above the additivity-based estimate, whereas the corresponding value of Barkas-effect parameter, 1.22, agrees quite well with the prescribed interval of 1.4±0.1.

Light charged-particle production from neutron bombardment of silicon up to 60 MeV: Role of level densities and isospin

Inclusive light charged-particle emission spectra and cross sections from neutron bombardment of silicon were measured at $30\ifmmode^\circ\else\textdegree\fi{},$ $60\ifmmode^\circ\else\textdegree\fi{},$ $90\ifmmode^\circ\else\textdegree\fi{},$ and $135\ifmmode^\circ\else\textdegree\fi{}$ over the neutron energy range from threshold to approximately 60 MeV. Source neutrons, continuous in energy, were provided by the spallation neutron source of the Los Alamos Weapons Neutron Research facility. Comparisons of our alpha-particle data with Hauser-Feshbach calculations, which include multistage emission processes and preequilibrium particle emission, indicate that the majority of alpha particles result from compound nuclear reactions. For proton and deuteron emission, direct and preequilibrium processes contribute significantly to the emission cross section. These data provide rigorous tests for the calculations while helping to guide the selection of input parameters such as nuclear level densities. The effects of assuming partial or complete isospin conservation are shown to be important for these reactions.

Radiation damage measurements in room-temperature semiconductor radiation detectors

The literature of radiation damage measurements on cadmium zinc telluride (CZT), cadmium telluride (CT), and mercuric iodide (HgI 2) is reviewed and in the case of CZT supplemented by new alpha particle data. CZT strip detectors exposed to intermediate energy (1.3 MeV) proton fluences exhibit increased interstrip leakage after 10 10 p/cm 2 and significant bulk leakage after 10 12 p/cm 2. CZT exposed to 200 MeV protons shows a two-fold loss in energy resolution after a fluence of 5×10 9 p/cm 2 in thick (3 mm) planar devices but little effect in 2 mm devices. No energy resolution effects were noted from a moderated fission spectrum of neutrons after fluences up to 10 10 n/cm 2, although activation was evident. Exposures of CZT to 5 MeV α particles at fluences up to 1.5×10 10 α/cm 2 produced a near linear decrease in peak position with fluence and increases in FWHM beginning at about 7.5×10 9 α/cm 2. CT detectors show resolution losses after fluences of 3×10 9 p/cm 2 at 33 MeV for chlorine-doped detectors. Indium-doped material may be more resistant. Neutron exposures (8 MeV) caused resolution losses after fluences of 2×10 10 n/cm 2. Mercuric iodide has been studied with intermediate energy protons (10–33 MeV) at fluences up to 10 12 p/cm 2 and with 1.5 GeV protons at fluences up to 1.2×10 8 p/cm 2. Neutron exposures at 8 MeV have been reported at fluences up to 10 15 n/cm 2. No radiation damage was reported under these irradiation conditions.

W Values in Propane-Based Tissue-Equivalent Gas

W values (mean energy required to form an ion pair after complete dissipation of incident particle energy) for electrons, protons, alpha particles and heavy ions ( 12 C, 14 N, 16 O) in propane-based tissue-equivalent gas are summarised and analytically represented. Experimental data are compared with the W values calculated from W values for pure components by applying the mixing model with the Strickler's constants. The analysis of a rather limited number of W values shows that there is a need for new data for protons and alpha particles for all energies, and for new high energy W values for electrons and heavy ions.

On the Conservativity of Hp(10)

For neutrons, numerical values for the Personal Dose Equivalent, Hp(10,alpha)_, in the ICRU TE slab phantom were recently recommended in an international standard (IEC-1323, 1995) and are intended for calibrating individual dosemeters fixed to the front of the phantom, with respect to energy and angle of incidence. These recommended conversion factors are compared with the present MCNP calculations of conversion coefficients hP_(10;E,alpha), and with calculations of Effective Dose, E (ICRP 60), and Effective Dose Equivalent, HE (ICRP 26), in the anthropomorphic ADAM phantom for monoenergetic and parallel neutron radiation (expanded field) with an angle of incidence varying from 0o (A-P) up to 75o to the left side of the phantom in the energy range from thermal up to 10 MeV. For the calculation of the conversion coefficients hp_(10;E,alpha) and the Effective Dose Equivalent, HE, in the phantom, a quality factor is applied which takes into account the revised Q(L) relationship of ICRP 60 and the new stopping power data for protons and alpha particles of ICRU Publication 49 (1993). For the calculation of Effective Dose, E, the smooth radiation weighting factor wR of ICRP 60 is used.