Energy Spectra Of Alpha Particles Research Articles

Distribution of 210Pb at endosteal surfaces of bone from Canadian Arctic caribou.

Alpha particle energy spectra were measured at femoral endosteal surfaces of Canadian Arctic caribou (Rangifer tarandus) to assess the profile of concentration with depth of 210Po supported by 210Pb. Femur samples from five caribou all showed a pronounced superficial concentration of 210Po, in a layer 1.9 - 6.4 microns thick. Within this layer 210Po was concentrated 1.5 - 10 times with respect to diffuse volume-distributed 210Po. This result is consistent with an earlier study of 210Po at human cranial bone surfaces, which showed 210Po to be concentrated about four times in a surface layer <3 microns thick. However, the present results have higher precision than the human bone data due to the much greater concentration of 210Pb and 210Po in caribou bone. The validity of using 210Po as a marker of 210Pb, and the in vivo 210Po/210Pb ratio are discussed. As a result of the measured endosteal superficial concentration of 210Po in caribou, the alpha particle dose was calculated to be enhanced by a factor of 1.06 - 1.96 (mean 1.48) for bone lining cells, and of 1.08 - 2.39 (mean 1.69) for soft tissue above the bone surface, assuming equilibrium between 210Pb and 210Po. It is suggested that an additional longer-lived compartment for bone surface lead could be incorporated into bio-kinetic models for lead.

Estimates of HZE particle contributions to SPE radiation exposures on interplanetary missions

Estimates of radiation doses resulting from possible HZE (high energy heavy ion) components of solar particle events (SPEs) are presented for crews of manned interplanetary missions. The calculations assume a model spectrum obtained by folding measured solar flare HZE particle abundances with the measured energy spectra of SPE alpha particles. These hypothetical spectra are then transported through aluminum spacecraft shielding. The results, presented as estimates of absorbed dose and dose equivalent, indicate that HZE components by themselves are not a major concern for crew protection but should be included in any overall risk assessment. The predictions are found to be sensitive to the assumed spectral hardness parameters.

Light particle emission in the reaction 144Sm(32S, fission) at Elab=838 MeV.

Energy spectra of light charged particles have been measured in coincidence with fissionlike fragments using the 4\ensuremath{\pi} charged-particle detector AMPHORA. Preequilibrium, prescission, and postscission components of emitted protons, deuterons, and alphas have been extracted from the energy spectra using a multiple source fit procedure. Including previously measured exclusive neutrons, a complete data set for light particle emission from the system $^{144}\mathrm{Sm}$${+}^{32}$S(26A MeV) is now available. Mass and excitation energy of an equilibrated composite system has been defined by application of the massive transfer model using multiplicities and apparent temperatures of the preequilibrium components. The results have been compared to statistical model computations. A fair overall agreement is observed for different parametrizations of the Fermi-gas level-density parameter with indications for a decrease of the level density parameter with increasing nuclear temperature. The correlations between slope parameter, prescission, and total particle multiplicity turned out to be a sensitive probe for the level density parameter. In the energy spectra of alpha particles a low-energy component has been observed with strong focusing into directions perpendicular to the fission axis.

Measurement of the alpha particle spectrum on the Cosmos-2044 biosatellite, using CN-85 track detectors

The energy spectra of cosmic ray alpha particles under 20 μm aluminized mylar shielding was measured in the 2–10 MeV nuc-1 energy interval on board the Cosmos-2044 biosatellite (82.3° inclination, 216–294 km altitude) using three layers of 100 μm thick CN-85 (Kodak) solid state nuclear track detectors. Overetched single surface tracks, for which the average etch-rate ratio and the particle residual range could be determined from the measurable track parameters, were selected on the top surfaces of each detector sheet for measuring and particle identification. The energy on the top surface of the top-most sheet was calculated for each alpha particle and the energy spectra determined, taking into account the energy dependence of the detection efficiency of the applied method. The densities of the alpha tracks and all the short range particle tracks are also given for each detector sheet.

Measurement of the lithium isotopic concentration

A method for determining the atomic proportions of 6Li and 7Li isotopes in enriched 6LiF, 7LiF and lithium metallic samples is presented. This study is based on measuring the energy spectra of alpha particles from proton-induced 7Li(p,α) 4He and 19F(p,α) 16O nuclear reactions and those of backscattered protons. The enriched LiF targets were obtained by thermal evaporation of thermoluminescent dosimetry chips, TLD-700 ( 7LiF) and TLD-600 ( 6LiF), onto self-supporting carbon substrates. Targets of metallic lithium were prepared in the same way. The 6Li enriched TLD-600 sample was found to contain 4.78 at.% of 7Li; however, no significant amount of 6Li was found in the TLD-700 sample. A 7.57 at.% concentration of 6Li in lithium metallic target was determined by using the TLD-700 as a 7Li isotope content standard. This value is consistent with the reported 7.5 at.% natural abundance of 6Li.

Level density of hot nuclei with A

The light charged particles emitted from hot $^{40}\mathrm{Ca}$ compound nuclei, populated at excitation energy ${\mathit{E}}_{\mathit{x}}$=94 MeV and 〈J〉=20.5\ensuremath{\Elzxh} by the reaction 130 MeV $^{16}\mathrm{O}$ on $^{24}\mathrm{Mg}$, have been studied. Energy spectra of protons and alpha particles, measured in coincidence with evaporation residues and with a selection of multiple-alpha chains, have been compared with the predictions of Monte Carlo statistical model calculations. The comparison shows that the level density of hot nuclei with A\ensuremath{\le}40, needed to account for the measured quantities, is well predicted by the Fermi-gas model using a level-density parameter ${\mathit{a}}_{\mathrm{eff}}$=A/8 ${\mathrm{MeV}}^{\mathrm{\ensuremath{-}}1}$ up to excitation energy 〈${\mathit{E}}_{\mathrm{th}}$/A〉\ensuremath{\sim}1.7 MeV. In agreement with theory, light hot nuclei do not show the transition from ${\mathit{a}}_{\mathrm{eff}}$=A/8 ${\mathrm{MeV}}^{\mathrm{\ensuremath{-}}1}$ to ${\mathit{a}}_{\mathrm{eff}}$\ensuremath{\sim}A/13 ${\mathrm{MeV}}^{\mathrm{\ensuremath{-}}1}$ evidenced in the A\ensuremath{\sim}160 mass region for the same range of excitation energies ${\mathit{E}}_{\mathrm{th}}$/A. The analysis of the alpha-particle spectra shows that the effects associated with the angular-momentum-induced deformations depend on the entrance channel characteristics and, in this case, are very small compared with those evidenced in the past for compound nuclei in the region A=50--70.

Alpha particles from the reaction12C +12C at 28.7 MeV/nucleon

A classical dynamical alpha-cluster model has been developed and applied in order to get inclusive energy spectra of alpha particles produced in the collision of12C +12C at the beam energy 28.7 MeV/A. Results of the calculations are compared with experimental data. The shapes of the experimental energy spectra and the absolute normalization at forward angles are approximately described without any free parameters. The model makes it possible to distinguish alpha particles originating from the compound system and from direct processes. The spectra at forward angles are dominated by projectile fragmentation processes. The cross section at larger angles is overestimated, which is partially due to emission of particles other than alpha particles in central collisions. The evaporation Hauser-Feshbach model predicts that alpha particles emitted from the compound nucleus constitute less than 26% of all emitted particles.

Deformation effects in the compound nucleus decay using the spin-alignment method.

Alpha-particle energy spectra and angular distributions with respect to the estimated spin direction of residual nuclei have been measured in heavy-ion fusion reactions. The spin direction was determined for each event by measuring the {gamma}-ray angular correlation patterns using the Spin Spectrometer. Measurements were made for the compound nuclear systems {sup 110}Sn{sup *}(94 MeV), {sup 114}Sn{sup *}(80 MeV), {sup 138}Nd{sup *}(82 MeV), {sup 164}Yb{sup *}(67 MeV), and {sup 170}Yb{sup *}(135 MeV) at the indicated excitation energies as a function of the alpha-particle energy and {gamma}-ray multiplicity. The anisotropy coefficients below the evaporation Coulomb barrier show distinct differences from {sup 110}Sn{sup *} to {sup 170}Yb{sup *}. These results and the shapes of the alpha-particle spectra are compared with statistical model calculations that incorporate deformation effects in the optical model transmission coefficients. The Sn{sup *} data can be explained without invoking deformation effects other than the ones included in the experimental yrast lines. However, for the heavier Yb{sup *} systems, a considerable spin-dependent deformation in the {alpha}-emission barriers is required. For these systems the {alpha} emission below the barrier is a sensitive probe for deformation that samples a broad range of excitation energies in the decay sequence.

Interplanetary energetic ions and polar radio wave absorption

This is a study of the ionization input of interplanetary (including solar flare) energetic protons and alpha particles into the south polar ionosphere over the interval 1982–1985. Energetic particle data are collected by the charged particle measurement experiment (CPME) of the Applied Physics Laboratory/Johns Hopkins University, onboard the IMP 8 satellite orbiting the Earth at 30–35 Earth radii. It is well known that interplanetary ions have full and prompt access to the polar ionosphere. The incremental ionization produced at 20–120 km. altitudes causes enhanced radio wave absorption which is observed by riometers operated by the University of Maryland, at South Pole, Antarctica. We compute the expected absorption from the vertical structure of the ionization deposited by these energetic particles and compare the computed values with the observations. The contribution of the alpha particles is found to be quite small as a percentage of the absorption except at the peak of the day 35, 1983, event, when their contribution to the absorption is about 0.6 dB out of a total of 3.4 dB. The dominant contribution to absorption at 30 MHz usually arises from protons below 10 MeV, specifically in the 2‐ to 4‐MeV interval. We have propagated the observed fluxes and energy spectra of protons and alpha particles through a seasonally adjusted slab model of the polar atmosphere. The atmospheric ionization resulting from the slowing and stopping of protons and alpha particles is used to estimate an equilibrium vertical ionization profile which is then convolved with an absorption efficiency profile to yield a calculated absorption. There is good agreement between the computed and observed absorption when the daily averaged absorption is above 0.1 dB; this shows that the interplanetary ions are the dominant contributors on those days. This set of observations constitutes the most complete and definitive illustration to date of the control by interplanetary particles of the shape and magnitude of the ionization profile in the lower ionosphere.

Range distributions of 200 keV helium in selected metals and ceramics

3He ions with an energy of 200 keV have been implanted into the metals magnesium, aluminum, titanium, vanadium, iron, nickel, zirconium and niobium and the ceramics magnesium oxide and aluminum oxide. Following these room temperature implantations, the range profile of helium in each target was measured by a technique of nuclear reaction analysis. The specific reaction used was 3He(d, α) 1H with a deuterium beam energy of 450 or 500 keV. Appropriate deconvolution of the alpha particle energy spectrum yields explicit helium range profiles. A statistical analysis was applied to these range profiles to extract the mean range, range straggling, skewness and kurtosis of the distribution. These experimental range moments were compared to theoretical models that are in current use. Measured ranges were similar to theoretical predictions; range straggling was slightly large than predicted. More significant differences between theory and measured values of higher moments were found.

An investigation of energy and emission probabilities of tritons and alpha-particles in the spontaneous fission of 252Cf

Abstract The energy spectrum of alpha-particles in the ternary fission of 252Cf has been determined by two independent methods, and that of tritons by just one. In the first method, Long Range Alpha (LRA) particles and tritons were identified by a ΔE-E telescope, and the energy spectrum and the emission probability of both tritons and alpha particles determined. In the second, combinations of the LR115 plastic and various thickness of aluminum foil were used to measure the energy spectrum of LRA particles down to a 2 MeV cut-off. The results indicate that the shape of the α-particle energy spectrum is almost Gaussian, and there is no significant variation from such a distribution in the low-energy tail.

Shell and odd-even effects on alpha-particle energy spectra from the (p,α) reaction on nuclei around neutron number 50

The energy spectra of \ensuremath{\alpha} particles emitted from (p,\ensuremath{\alpha}) reactions on $^{90}\mathrm{Zr}$, $^{92}$,94,96,98,100Mo, $^{93}\mathrm{Nb}$, $^{106}\mathrm{Pd}$, and Ag with 18 MeV protons and on some of them with 15 MeV protons have been measured in order to clarify the shell and odd-even effects in the preequilibrium processes of (p,\ensuremath{\alpha}) and (n,\ensuremath{\alpha}) reactions. From the experimental results, it was found that there exists no appreciable odd-even effect on the target nuclei in energy spectra for the preequilibrium (p,\ensuremath{\alpha}) reaction except for the spectra corresponding to the low lying states of the residual nuclei. Considerable change in the energy spectra in the energy region higher than 16 MeV has been observed for target nuclei around the magic number N=50. We have calculated the energy spectra, by using the knockout model introducing effective Q values, the pairing correlation and a modified uniform spacing model in which the uniform spacing levels have a wide spacing at the magic number. The shell effect of the gross structure of the energy spectra for the nuclei near the magic nuclei can be explained very well in terms of the present knockout model, although the fine structures of the spectra above 16 MeV which correspond to the low lying states or groups of the states of the residual nuclei cannot be explained so well.

Use of the 16O(d, α 0) 14N nuclear reaction in the analysis of oxide films

The use of the 16O(d, α 0) 14N nuclear reaction to obtain oxygen concentration profiles in surface oxide layers, up to 4000 Å thick, has been studied using incident deuterons of 900 keV and 1.08 MeV and comparisons made of the oxygen sensitivities and depth resolutions. Samples investigated include a Ta 2O 5 on tantalum standard, thermally grown silicon oxide films on silicon and two types of chromium conversion coatings on zinc electroplated panels. A nuclear reaction simulation code has been employed to reveal surface compositions from the energy spectra of the emitted alpha particles.

Refinement of the28Si (n, ?0),(n, ?1), (n, ?2), (n, ?3),and (n, ?4) cross sections for 14.1-MeV neutrons

The main problem of the present work is the refinement of the /sup 28/Si (n,alpha) /sup 25/Mg cross sections at 14.1-MeV for transitions to the ground and low-lying states of the residual nucleus by using the nonlinear method of least squares to separate the overlapping spectral lines. The alpha particle energy spectrum was measured with a lithium-drifted silicon semi-conductor detector placed in the neutron flux and being simultaneously the target and the detector. In this procedure the alpha particle spectrum integrated over the angle of emission is measured. The determination of the reaction cross section for a particular nuclear transition is essentially reduced to the measurement of the intensity of the line corresponding to this transition.

Depth distribution of fluorine in enamel teeth by19F(p, α0)16O reaction

Fluorine depth profiles have been measured into enamel of human teeth by using the nuclear reaction19F(p, α0)16O for incoming proton beam at 1350 keV. Details of fluorine distribution over a few micrometres have been obtained by comparison of the energy spectrum of alpha-particles from the reaction in teeth with that of the standard target of CrF3. The average concentration of fluorine is 1.5 mg/g in the enamel of healthy tooth, while the concentration is below 0.3 mg/g (MDL) in the caried zones. These values can reach 13 mg/g in the enamel of a fluorine tooth.

Correlations between the alpha particles and ejectiles in the reactionNb93+N14atElab=208MeV

The correlations between alpha particles and various ejectiles were investigated in the reaction $^{93}\mathrm{Nb}$+ $^{14}\mathrm{N}$ at ${E}_{\mathrm{lab}}=208$ MeV. The ejectiles were measured at a fixed angle ${\ensuremath{\theta}}_{1}=+22\ifmmode^\circ\else\textdegree\fi{}$, which was slightly more backward than the grazing angle, and the alpha particles were measured at various angles ${\ensuremath{\theta}}_{2}$ in and out of the reaction plane. The experimental results were analyzed in terms of various aspects of the correlations such as the energy and angular correlations, the projected energy spectra, and differential multiplicities. An analysis based on the three body kinematics was also made to study the features associated with the sequential ejectile breakup process. It was found that two processes contribute to the coincident alpha particles. The first process was ascribed to the sequential breakup of the excited ejectiles and was found to be dominant in the angular region of ${\ensuremath{\theta}}_{2}$ close to the ejectile detector. The coincidence cross section of the sequential breakup component can be approximately factorized as a product of the singles cross section of excited ejectiles before breakup and the excitation spectrum of the ejectiles. The other process, ascribed to a nonsequential mechanism, was dominant for the alpha particles detected on the opposite side of the ejectile detector with respect to the beam direction. This process is characterized by the following properties: (i) The energy spectra of the coincident alpha particles have shapes which are almost identical to those of the singles spectra taken at the same angles. (ii) The same is true to a lesser extent for the ejectile spectra except for the higher-energy region. (iii) In this angular region of ${\ensuremath{\theta}}_{2}$ the differential coincidence cross section can be approximately expressed in the factorization form, $\frac{{d}^{4}\ensuremath{\sigma}}{d{\ensuremath{\Omega}}_{1}d{\ensuremath{\Omega}}_{2}d{E}_{1}d{E}_{2}}=K\ifmmode\cdot\else\textperiodcentered\fi{}(\frac{{d}^{2}\ensuremath{\sigma}}{d{\ensuremath{\Omega}}_{1}d{E}_{1}})(\frac{{d}^{2}\ensuremath{\sigma}}{d{\ensuremath{\Omega}}_{2}d{E}_{2}})$. The relative contribution of the two processes was found to be roughly comparable.NUCLEAR REACTIONS $^{93}\mathrm{Nb}$($^{14}\mathrm{N}$,$\mathrm{HI}\ensuremath{\alpha}$), $E=208$ MeV; measured two-dimensional HI-$\ensuremath{\alpha}$ coincident energy and angular correlations; deduced reaction mechanisms.

Analysis of soft error in MOS dynamic RAM

AbstractThe soft error rate of a MOS dynamic RAM is strongly influenced by the energy spectrum of the incident alpha particles, the collecting processes of electric charges generated by them, and the critical charge of the device. When the collected charge distribution is Gaussian, the error rate is well approximated by a complementary error function of the critical charge, which can explain the voltage dependence of the soft error rate; the dispersion of the distribution is also obtained experimentally. The dispersion depends on the thickness of the polyimide film coated on a chip, and the coating improves the error rate by absorbing alpha particles as well as attenuating their energies. The stopping power of the polyimide film is 1.47 × 103 times as large as that of air, which is in good agreement with the calculated value.

Alpha-particle energy spectra measured at forward angles in heavy-ion induced reactions

Energy spectra have been measured for α-particles emitted in the bombardment of 159Tb, 181Ta, 197Au and 232Th nuclei by 20Ne, 22Ne and 40Ar projectiles. The reaction products emitted in the angular range (0 ± 2)° relative to the beam direction were analysed using a magnetic spectrometer and detected by means of a semiconductor ΔE- E telescope. It was found that in all cases the experimentally measured maximum α-particle energy almost amounts to the maximum possible value calculated from the reaction energy balance for a two-body exit channel. A correlation was found between the measured absolute cross section in different target-projectile combinations and the α-particle binding energy in the target nuclei. On the basis of the obtained results a conclusion has been drawn that the α-particles are emitted in the early stage of the reaction.

Excited States of 4He Observed in the 6Li+d Reaction

Energy spectra of alpha particles from the 6 Li(d, α) 4 He * reaction at 13.6 MeV were observed at extremely forward angles. Angular correlations between alpha particles and deuterons were obtained for the 6 Li(d, αd)D reaction when the alpha particles were detected at 20° using coincidence method. Energy spectrum of alpha particles shows a broad peak corresponding to the excited state of 25.52 MeV in 4 He with the width of 2.26 MeV. The spin-parity of this state is assigned to be 0 + from the facts that the angular distributions of the emitted alpha particles are reproduced with DWBA theory assuming the angular momentum transfer of 2 and that the angular correlation function shows an isotropic distribution. In the coincidence energy spectrum of alpha particles a peak corresponding to the excited state of 27.5 MeV in 4 He was observed. The angular correlation for the excited state of 27.5 MeV is consistent with the assignment of odd parity.

Geomagnetically trapped alpha particles from 18 to 70 MeV

The energy spectrum of alpha particles trapped in the magnetosphere has been measured for the first time between 18 and 70 MeV for L values from 1.85 to 2.85 at 740-km altitude. In this energy range the spectrum is described by a power law with exponent 5.5 ± 1.3. The L distributions of alphas and protons with the same energy per nucleon are similar, but at the same energy per particle, distributions are distinctly different. The alpha to proton ratio maximum is 3.5 × 10−3, an order of magnitude lower than that in the solar wind, and it falls steeply with energy.