Energy Spectra Of Charged Particles Research Articles

Study of latent and etched tracks by a charged particle transmission technique

A recently suggested technique for non-destructive investigation of inhomogeneities in thin objects, which is based on the measurement of the energy spectra of charged particles transmitted through the object, is used for the study of thermal annealing of 10–20 μm thick polyethylene terephtalate, polypropylene and polycarbonate foils irradiated with 1–10 MeV/amu heavy ions. At elevated temperature a foil linear contraction is observed on pristine and irradiated material. Also the foil roughness increases with increasing temperature. On the same foils with etched pores 0.5–1.0 μm in diameter, the thermal annealing results in gradual closing of the pores up to about 30% of their initial diameter at the temperatures of 150–175°C. At higher temperatures the pore diameter increases and achieves its initial value.

Low and high energy limits of particle spectra in QCD jets

Charged particle energy spectra in e+e- annihilation are compared with the analytical predictions from the QCD evolution equation in the Modified Leading Log Approximation. With the nonperturbative initial condition shifted down to threshold as suggested by the Local Parton Hadron Duality picture a good description of the data from the lowest up to highest available energies results. The two essential parameters in this approach are determined from a moment analysis. The sensitivity of the fit to the running of alpha_s and to the number of active flavours (including a light gluino) is demonstrated. For very high energies the theory predicts a scaling behaviour in certain rescaled variables (``zeta-scaling''). The data show an approximate behaviour of this type in the present energy range and come close to the predicted asymptotic scaling function for the small particle energies.

Artificial electron and ion beam effects: Active Plasma Experiment

The Active Plasma Experiment uses intensive electron beam emission for the study of dynamic processes in the magnetosphere and upper ionosphere. The beam energy and current are as high as 8 keV and 100 mA and the pitch angle of the emission varies in the range from 50° to 80°. The basic cycle of electron injection is formed by current pulses of different duration, intensity, and frequency. The spacecraft potential is balanced by a low‐energy xenon plasma generator during the electron beam injection. The spacecraft potential is measured by the floating probe, and the response of the environment is studied by the charged particle spectrometer working in the energy range from 0.05 to 25 keV. During the neutral or ionized Xe release without the electron gun operation the spacecraft potential remains nearly unchanged and the observed energy spectra of charged particles do not exhibit the presence of any acceleration process. The spacecraft potential during electron beam emission does not exceed 50 V if the Xe plasma or the neutral gas was released together with the electrons. The electron gun firing creates a disturbance which produces a broad spectrum of energetic electrons extending up to 1.5 keV. The acceleration process can be explained by the introduction of the electric field with intensity of about 100 V/m. This intensity is in agreement with the observed E × B drift velocity. The spatial extent of the disturbance is established to be tens of meters.

The charged‐particle fluxes at auroral and polar latitudes and related low‐frequency auroral kilometric radiation‐type and high‐frequency wideband emission

The results of simultaneous observations of charged particle fluxes within the energy range 50 eV to 20 keV (plasma energy‐angle spectrometer, PEAS experiment) and plasma waves within the frequency range 0.1 to 10 MHz (plasma radio spectrometer, PRS 3 experiment) on board the APEX spacecraft are presented. The data were obtained at polar and auroral latitudes in the dawn‐dusk and noon‐midnight time sectors. The low‐frequency (LF) sporadic emission mainly on frequencies lower than the local gyrofrequency was commonly observed within a comparatively narrow latitude interval (∼5°– 6°) of the auroral oval. The maximum of spectral wave intensity was revealed at a frequency of ∼ 200 kHz. The sporadic character of the observed emissions, the spectra, are very similar to those reported for auroral kilometric radiation (AKR), and the temporal and spatial occurrences imply its relation to the source of AKR emissions measured at the higher altitudes, with regards to our wave measurements as LF AKR‐type emissions. Comparative analysis of spatial distributions of charged particle energy spectra and variations of wave spectra at auroral oval latitudes showed that several conditions should be fulfilled for LF AKR generation. These conditions are related both to the intensity and energy of precipitating ion and electron fluxes, and to albedo electrons and the ionospheric plasma parameters. The wideband HF emission was observed together with the LF AKR‐type emission during the morning auroral oval crossing. At spacecraft apogee altitudes, in the polar cap zone intense electron precipitations and an increase of plasma noise intensity at frequencies equal or below ƒHe were observed at the period when the IMF was northward These precipitations and emissions were accompanied by the horizontal currents crossing the polar cap, the so‐called theta structure.

Design of an electronic charged particle spectrometer to measure 〈ρ𝓡〉 on inertial fusion experiments

The design and fabrication of a new diagnostic that measures the energy spectra of charged particles from targets on the Omega Upgrade are actively underway. Using seven 512×512 charge coupled devices (CCDs) and a 7.5 kG permanent magnet, this instrument will uniquely determine particle identities and measure particle energies from 1 MeV up to the maximum charged particle energies of interest for ρR measurements (10.6 MeV knock-on tritons, 12.5 MeV knock-on deuterons and 30.8 MeV tertiary protons). The resolution of the diagnostic will be better than 5%. We have tested the response of SITe back-illuminated CCDs to 1.2–13.6 MeV protons from our Cockcroft–Walton accelerator and to alpha particles from an Am241 source, and the results agree extremely well with predictions. With its high density picture elements, each CCD has 105 single-hit detectors. In the case of a low DT yield of 109 neutrons, about 100 knock-on charged particles will be detected when the spectrometer aperture is 60 cm from the implosion. Measurements of ρR up to 150 mg/cm2 can be obtained from knock-on D and T spectra, and values up to 300 mg/cm2 can be determined from secondary proton spectra. The sensitivity of the CCDs to 14 and 2.5 MeV neutrons has been experimentally determined using our Cockcroft–Walton accelerator source and indicates that by incorporating neutron shielding, the signal to neutron noise ratio at a yield of 1011 will be better than 100:1. In the development phases of this program, we plan to utilize CR-39 track detectors concurrently with the CCDs.

Modeling detector response for neutron depth profiling

In Neutron Depth Profiling (NDP), inferences about the concentration profile of an element in a material are based on the energy spectrum of charged particles emitted due to specific nuclear reactions. The detector response function relates the depth of emission to the expected energy spectrum of the emitted particles. Here, the detector response function is modeled for arbitrary source and detector geometries based on a model for the stopping power of the material, energy straggling, multiple scattering and random detector measurement error. At the NIST Cold Neutron Research Facility, a NDP spectrum was collected for a diamond-like carbon (DLC) sample doped with boron. A vertical slit was placed in front of the detector for collimation. Based on the computed detector response function, a model for the depth profile of boron is fit to the observed NDP spectrum. The contribution of straggling to overall variability was increased by multiplying the Bohr Model prediction by a ramp factor. The adjustable parameter in the ramp was selected to give the best agreement between the fitted profile and the expected shape of the profile. The expected shape is determined from experimental process control measurements.

A comparison of neutron and gamma damage effects on silica glass in a nuclear reactor radiation environment

A study of the relative damage effects of neutrons and gamma rays on silica glass in a nuclear reactor radiation environment is reported. The neutron and gamma energy spectra of the Ohio State University Research Reactor beam port #1 were applied to silica glass to obtain primary knock-on charged particle energy spectra. The resultant charged particle spectra were then applied to the polyatomic forms of the Lindhard et al. integrodifferential equation for damage energy and the Parkin and Coulter integrodifferential equation for net atomic displacement. The results show that near a nuclear reactor core the vast majority of the dose to silica is due to gamma rays (factor of roughly 40) and that neutrons cause much more displacement damage than gamma rays (35 times the oxygen displacement rate and 500 times the silicon displacement rate). However, pure silica core optical fibers irradiated in a nuclear reactor's mixed neutron/gamma environment exhibit little difference in transmission loss on an equal dose basis compared to fibers irradiated in a gamma only environment, indicating that atomic displacement is not a significant damage mechanism.

Evaporation of charged particles from highly deformed nucleus

Energy spectra of charged particles evaporated from compound nucleus have been of interest because current statistical-model codes do not reproduce the experimental results well. Deformation has been proposed as a cause of the obsered anomaly, but an adequate theoretical expression for the emission rate from deformed nucleus is as yet lacking. We present here a closed form expression for the emission width of charged particles from nuclei of arbitrary shape. In addition, we propose a new evaporation mechanism in which charged particles are emitted while leaving the residual nucleus in its fissionsaddle-point configuration. Applying this model to alpha-particle emission, we obtain a very low energy alpha-particle component which may have been observed experimentally.

Efficient energy spectrometer for charged particle detection in surface studies

We have recently built a spectrometer that efficiently collects the energy spectrum of charged particles that emerge from targets bombarded by low-flux (10−15 A) incident beams. The spectrometer is used to detect positron-induced secondary electrons and low-energy positron-stimulated Auger electron emission. Slow positrons and positron-induced secondary electrons are generated from a cold neon positron moderator deposited onto an encapsulated 22Na source. The moderated beam is magnetically transported to the target with two sets of E×B plates. The particles emerging from the target are energy dispersed by a third set of plates and are detected with a one-dimensional position-sensitive detector. The data-collection rate for the energy-distribution spectrum is ∼10–100 times faster for this experiment relative to the more common method of sweeping grids or the plates.

Reduction of charged particle energy spectra to zero target thickness

A recursive formula and a simple iteration procedure are presented for reduction of a measured charged particle spectrum to the shape it would have at zero target thickness.

Double-differential inclusive hydrogen and helium spectra from neutron-induced reactions at 27.4, 39.7, and 60.7 MeV: Oxygen and nitrogen.

Double-differential cross sections for the neutron-induced production of p, d, t, $^{3}\mathrm{He}$, and alpha particles from oxygen and nitrogen have been measured using an unpolarized neutron facility. Neutron beam energies of 27.4, 39.7, and 60.7 MeV were used. The charged particle energy spectra, at six forward laboratory angles, 15, 20, 35, 40, 45, and 65, and, where feasible, at three backward angles, 90, 130, and 150 deg, range up to the kinematic maximum, from a typical low-energy cutoff of 4 MeV for p, d, t, and alpha particles, and 8 MeV for $^{3}\mathrm{He}$. Intranuclear cascade plus deexcitation calculations were carried out. The data are compared with these calculations and with available proton-induced (charge-symmetric) reaction spectra for oxygen.

Alphas emission from π - absorption in Li using CR-39

Energy spectra of charged particles emitted after the absorption of stopped negative pions in 6,7Li have been measured using a stack of 1800μ CR-39 plastic track detectors. The main aim of the study was the search of monochromatic 4He and 3He of 55 MeV and 60 MeV which should be accompanied by a monoblock emission of three or four neutrons, respectively. Preliminary results give the yield of these reactions ≤10 -4 and <10 -5 corresponding to emission of 3n and 4n respectively. A first estimation for the continous He-spectra also was made.

The Interaction of Low-Energy Negative Pions with Nuclear Emulsion

ET6B emulsions 200 µm thick were exposed to 65 MeV and 379 MeVπ- beams, and the range-energy relations of π- in emulsion for the energy region from 50 MeV to 10 MeV were obtained. The multiplicity and energy spectra of charged particles from pion absorption in emulsion were measured with a 65 MeVπ- beam. The multiplicity of charged particles was also measured with a 379 MeVπ- beam. The experimental results were compared with calculations by the evaporation and cascade theory. The experimental setup and the conditions for the processing of the emulsion to study the pion-nucleus interaction are reported.

Double differential inclusive hydrogen and helium spectra from neutron-induced reactions on carbon at 27.4, 39.7, and 60.7 MeV

Double differential cross sections for the neutron-induced production of p, d, t, $^{3}\mathrm{He}$, and alpha particles from carbon have been measured using unpolarized neutrons. Neutron beam energies of 27.4, 39.7, and 60.7 MeV were used. The charged particle energy spectra at nine laboratory angles---15, 20, 35, 40, 45, 65, 90, 130, and 150 deg---range up to the kinematic maximum, from a lower energy cutoff of 4 MeV for p, d, t, and alpha and 8 MeV for $^{3}\mathrm{He}$. A CH target was used so that the absolute normalization was obtained simultaneously from the n-p cross sections. Intranuclear cascade plus deexcitation calculations were carried out. The data are compared with these calculations and with available proton induced (charge symmetric) reaction spectra.NUCLEAR REACTIONS $^{12}\mathrm{C}(\mathrm{n}, \mathrm{p}x; \mathrm{d}x; ^{3}\mathrm{H}x; ^{3}\mathrm{He}x; ^{4}\mathrm{He}x)$, ${E}_{\mathrm{n}}=27.4, 39.7, 60.7$ MeV; measured $\ensuremath{\sigma}(\ensuremath{\theta}; E)$, ${\ensuremath{\theta}}_{\mathrm{lab}}=15, 20, 35, 40, 45, 65, 90, 130, 150$ deg. Intranuclear cascade plus deexcitation calculations.

Energy spectra of charged particles emitted following the absorption of negative pions stopped within oxygen-containing organic compounds (radiotherapy application)

The energy spectra of charged particles (protons, deuterons, tritons, 3He, 4He, 6Li, 7Li) emitted following the absorption of stopped negative pions in oxygen-containing organic compounds (Mylar and cellulose acetate with stoichiometric C:O ratios of 2.5 and 1.5, respectively) are measured from 1.5 MeV up to the kinematical limit. Targets of different thickness are used (about 0.1 and 1.4 mm thick), in order to check the corrections to be made for particle and energy losses due to the finite target thickness. Thick target yields of biological and medical relevance are evaluated. The integrated particle yields for oxygen are determined. They are generally smaller than for carbon. It is concluded that the biological effectiveness of stopped pions is reduced in tissue compared with estimates based on the particle spectra obtained for pure carbon. The data might contribute to the understanding of radiotherapy with negative pions and have consequences for therapy planning codes at present being developed.

Decay of hot, high-spin nuclei produced inLi6-induced fusion reactions

The decay of compound nuclei formed at high excitation and angular momentum in $^{6}\mathrm{Li}$ bombardment of $^{181}\mathrm{Ta}$, $^{194,198}\mathrm{Pt}$, $^{197}\mathrm{Au}$, and $^{208}\mathrm{Pb}$ has been investigated in a coherent program of experiments and statistical model analysis. The measured decay properties include absolute cross sections for fusion and for all major competing decay modes, fission-fragment angular distributions, charged-particle energy spectra, and ($^{6}\mathrm{Li}$, $\mathrm{xn}$) residue mass distributions. The measurements are compared with highly constrained calculations in which all nuclear structure parameters are fixed to values consistent with the rotating-liquid-drop and noninteracting Fermi-gas models. Possible ambiguities in interpreting the experimental results, and the likely influence of neglected effects on the statistical model calculations, are explored. In order to obtain good quantitative agreement with all measurements it is necessary to simulate in the calculations the effects of preequilibrium nucleon emission in the early stages of the decay, and it is furthermore helpful to allow the collective enhancements of deformed-nucleus level densities to fade out with increasing temperature. Within existing uncertainties in the statistical model treatment, reproduction of the experimental results does not require any appreciable macroscopic or microscopic corrections to the nuclear structure input parameters. Several experimental methods for studying more selectively the fission and particle decay of low-excitation, high-spin nuclei, and thereby enhancing sensitivity to microscopic structure contributions, are suggested.NUCLEAR REACTIONS Fusion, fission, particle emission for $^{6}\mathrm{Li}$+$^{181}\mathrm{Ta}$, $^{194,198}\mathrm{Pt}$, $^{197}\mathrm{Au}$, $^{208}\mathrm{Pb}$, $E(^{6}\mathrm{Li})=74.8, 84.2, 94.4$ MeV; measured energy spectra, ${\ensuremath{\sigma}}_{\mathrm{tot}}$, $\ensuremath{\sigma}(\ensuremath{\theta})$ for fission and inclusive charged-particle emission, ${\ensuremath{\sigma}}_{\mathrm{tot}}$ and mass distribution of residual nuclides for ($^{6}\mathrm{Li}$, $\mathrm{xn}$) reactions; compared measurements with statistical model calculations incorporating simple macroscopic structure predictions, deformed-nucleus level densities, hot-spot simulation of preequilibrium nucleon emission; discussed theoretical uncertainties in statistical model analysis, possibilities for experiments with enhanced sensitivity to microscopic structure.

Energy spectra of charged particles emitted following the absorption of stopped negative pions in calcium

The energy spectra of charged particles (protons, deuterons, tritons, and 3,4He nuclei) emitted following the absorption of stopped negative pions in a 0.022 g cm 2 thick target of calcium are measured from the experimental threshold energy at 2 MeV (for 3He nuclei: 8 MeV) up to the kinematical limit. The experiments are carried out at the pion channel πE3 of the Swiss Institute for Nuclear Research. The data are compared with existing measurements.

Measurements of the energy spectra of charged particles within the vertical-10 rocket experiment

On December 21-st, 1981, at 18.35 hours UT from the territory of the USSR (coordinates - 49°N/L 2/) in implementation of scientific objectives and in accordance with the ‘INTERCOSMOS’ Programme, there was launched the heavy geophysical rocket ‘VERTICAL-10’. The scientific payload included a low-energy two-channel spectrometer for measuring the differential flows of electrons and protons within the energy range 0.1 to 10 keV, covered by 15 exponentially distributed energy levels.

Charged particle emission following the absorption of stopped π− in 12C, 59Co and 197Au

Energy spectra of charged particles (p, d, t, 3 He, α) emitted following the absorption of stopped π − in 12 C, 59 Co and 197 Au have been measured. The results are compared with results from neutron spectroscopy and discussed in the context of the quasi-deuteron model of π − absorption.

Energetic charged-particle spectrum followingμ−capture by nuclei

The energy spectra of charged particles (mainly protons) emitted following muon capture have been measured for targets of Al, Cu, and Pb. The intensity of the energetic (40 --70 MeV) emitted particles falls exponentially with increasing energy, I=I/sub 0/exp(-E/E/sub 0/), with exponential constant E/sub 0/ 7.5 +- 0.4 MeV (Al), 8.3 +- 0.5 MeV (Cu), 9.9 +- 1.1 MeV (Pb). The integrated yield for particles above 40 MeV was found to be (1.38 +- 0.09) x 10/sup -3/ per capture for Al, (1.96 +- 0.12) x 10/sup -3/ per capture for Cu, and (0.171 +- 0.028) x 10/sup -3/ per capture for Pb.