Proton-induced Nuclear Reactions Research Articles

Onset of multifragmentation dominance at 1 GeV proton-induced nuclear reaction for target nuclei with A ⩽ 160

The onset of the multifragmentation regime is studied by means of 1 GeV proton-induced nuclear reactions at various target nuclei. Analysing the measured longitudinal momentum transferred to the fragmenting nucleus it is found that the multifragmentation process seems to dominate over the induced fission in the mass region A ⩽ 160. The qualitative behaviour of the experimental findings is reproduced by considering a simple model.

Mass yield distributions for 1 GeV proton-induced nuclear reactions on Ni and Ag

For 1 GeV proton-induced reactions on Ni and Ag the inclusive mass spectra covering a wide range of masses are analyzed with a two-step statistical multifragmentation model which considers the secondary decay of the primordial fragments. It is found that the yield of lighter clusters can only be reproduced by considering the evaporation processes. The experimentally observed U-shaped mass spectra are described by essentially one parameter - the temperature of about 6 MeV. The power-law fit gives an exponent about one unit lower than the critical one.

LET Spectra in Low Earth Orbit

The Trapped Ions in Space (TRIS) experiment was flown on the Space Shuttle in October, 1984. It contained a stack of plastic track detectors that recorded linear energy transfer (LET) spectra behind various thicknesses of shielding in a 57 degree inclination orbit. A preliminary analysis of the data shows that behind shielding of at least 40 mils Al equivalent, the LET spectrum is dominated by galactic cosmic rays and the direct ionization of trapped protons and that it is reasonably well predicted by the CREME model. For a minimum shielding of approximately 4 mils Al equivalent, the measured LET flux exceeds the CREME predictions, especially at high LET. This is probably due to contributions from the products of proton-induced nuclear reactions in the detector and helium ions trapped in the inner radiation belt.

Activation analysis with a 9.1 MeV proton beam

Absolute thick-target γ-ray yields have been measured for a great variety of elements using an activation method. The data are used to discuss the possibilities of impurity activation analysis by means of 9.1 MeV proton-induced nuclear reactions. The most favourable absolute yields from nuclear reactions and absolute intensity values of main γ-lines are listed in the table. The tabulated results allow one to associate the impurity content in the irradiated sample with the intensity of the corresponding peaks in the gamma-ray spectrum, to determine the measurement sensitivity and to choose optimum analysis conditions.

Methods for Calculating SEU Rates for Bipolar and NMOS Circuits

Computer codes developed at Clarkson for simulating charge generation by proton-induced nuclear reactions in well-defined silicon microstructures can be used to calculate SEU rates for specific devices when the critical charge and the dimensions of all SEU sensitive junctions on the device are known, provided one can estimate the contribution from externally-generated charge which enters the sensitive junction by drift and diffusion. Calculations for two important bipolar devices, the AMD 2901B bit slice and the Fairchild 93L422 RAM, for which the dimensions of the sensitive volumes were estimated from available heavy-ion test data, have been found to be in agreement with experimental data. Circuit data for the Intel 2164A, an alpha sensitive dRAM, was provided by the manufacturer. Calculations based on crude assumptions regarding which nuclear recoils and which alphas trigger upsets in the 2164A were found to agree with experimental data.

Structural analysis of membranes by means of a nuclear reaction

A narrow nuclear resonance in low-energy proton-induced nuclear reactions in the stable isotope 18O has been utilized in a new technique for investigating the structure of biological membranes. This technique leads to a direct determination of the density profile of 18O-labelled molecules. Results with a multilayer of egg lecithin and with erythrocyte ghosts demonstrate the applicability of the method to structural analysis.

Microdosimetric Aspects of Proton-Induced Nuclear Reactions in Thin Layers of Silicon

A computer simulation model which calculates the energy deposited within a small sensitive volume embedded in a larger volume as a result of nuclear interactions anywhere in the larger volume is outlined. The model is tested by comparison with the pulse-height spectra measured in silicon surface barrier detectors as a result of exposure to protons at different energies. The model is then used to provide physical insight into the role played by the nuclear recoil in localized energy deposition about a nuclear interaction.

Proton-Induced Nuclear Reactions in Silicon

Measurements of the energy deposited in silicon surface-barrier detectors as a result of proton-induced nuclear reactions were carried out at the Harvard Cyclotron for protons with incident energies ranging from 50 to 158 MeV and detectors with thicknesses of 2.5, 4.2, 24.1, 100, and 200 ?m. The number of events in which a given threshold amount of energy is deposited in a 4.2 ?m detector varied with incident proton energy in a manner similar to previous measurements of the proton-induced soft-error cross section. The number of events in which at least a threshold amount of energy was deposited in the detector fell off in a near exponential manner with increasing threshold energy. The data were found to be in reasonable agreement with a computer simulation model developed in our laboratory. The model is used to illustrate how the mass spectra of the residual nuclear fragments shifts towards lower masses with increasing recoil energy. Lighter recoils have longer ranges and a greater chance of leaving a microscopically thin sensitive volume element before coming to their end of range.

Utilisation des réactions nucléaires induites par les protons pour l'étude des monnaies d'argent et d'or.

Modem numismatics having need of more and more precise quantitative basis, a analysis non-destructive method based on proton-induced nuclear reactions has been developped . This proton-activation analysis allows the dosage of slight quantities at the scale of the P. P. M present in silver , gold , or alloy of these metals coins.

On the Similarity of Pion- and Proton-Induced Nuclear Reactions at High Energies

On the Similarity of Pion- and Proton-Induced Nuclear Reactions at High Energies

The lattice location of fluorine in iron and nickel

Abstract The lattice location of implanted fluorine in iron and nickel crystals has been studied using the ion-beam particle channeling technique and proton-induced nuclear reactions in an attempt to determine lattice sites corresponding to measured magnetic hyperfine fields at fluorine in these ferromagnets.

Nitrogen concentration in GaP measured by optical absorption and by proton-induced nuclear reactions

A method is described for the determination of the nitrogen concentration in GaP crystals from optical absorption measurements. The method has been calibrated by measuring the absolute nitrogen concentration by nuclear reaction quantitative analysis in the same samples for which the optical absorption was measured. The relationships between the nitrogen concentration, the integrated absorption of the A line (2.3172 eV), and the optical absorption at Ax (2.3275 eV) at 4.2°K are given by [N] cm−3=8.5×1014∫αA d E=3.4 ×1016αAx, where α is measured in cm−1 and d E in meV. Previous formulas which have commonly been used to determine the nitrogen concentration in terms of optical absorption overestimate the nitrogen concentration by about a factor of 5. Also the application of these formulas has varied between laboratories. Section I describes the determination of nitrogen concentrations by nuclear microanalysis. Measurements have been made in the range from [inverted lazy s]5×1016 to [inverted lazy s]1018 cm−3 in GaP grown by the liquid encapsulated Czochralski process in a nitrogen-pressurized crystal puller and in nitrogen-doped GaP grown by liquid phase epitaxy at [inverted lazy s]1000°C. Two distinct charged-particle techniques have been employed. In crystals containing nitrogen of normal isotopic composition, the 14N concentration was determined by proton activation using the reaction 14N(p,α)11C with proton energies in the range 6–10 MeV. The reaction product, 11C, was chemically separated after irradiation. The 11C is a positron emitter, and the γ rays from the positron annihilation were measured. Boron interference through the reaction 11B(p,n)11C was independently determined by measuring the prompt α-particle emission from the reaction 11B(p,α1)8Be*→2α2 during irradiation with 685-keV protons. In 15N-doped LPE layers, the 15N concentration was determined by measuring the prompt α-particle emission from the reaction 15N(p,α)12C during irradiation with 685-keV protons. Section II describes the optical absorption measurements and the correlation with the nuclear measurements. The temperature dependence of the integrated absorption and the line shape of the A line have also been measured. For determination of the nitrogen concentration, the A-line absorption measurements should be made at a temperature at which the absorption line shape is amenable to accurate integration. The integrated absorption can then be corrected to its value at 4.2°K and the nitrogen concentration calculated from the above relationship.

Absolute gamma-ray efficiency of a 50 cm3 Ge(Li) detector

Efficiencies of a 50 cm3 coaxial Ge(Li) detector have been determined for γ rays from 122 keV to 9.17 MeV for a source to detector distance of 10 cm. Measurements were made with radioactive sources for γ-rays energies up 3.25 MeV and with γ rays from proton-induced nuclear reactions for higher energies. Absolute efficiencies determined with calibrated radioactive sources at ower γ-ray energies are in good agreement with efficiencies determined by comparison with calculated NaI efficiencies at higher energies.

Production of neutral hydrogen atoms with energies of some MeV

Abstract Experiments on proton-induced nuclear reactions and excitations in a magnetic field are often seriously hampered by the displacement and change of direction of the proton beam caused by the magnetic field. In such cases one can accelerate H2+ ions and split them by a suitable gas into H and H+. After electric or magnetic deflection of the charged particles to the wall one gets a good defined beam of neutral atoms with an intensity of over 10% of the original H2+ beam.

ACTIVATION CROSS SECTIONS FOR C12(p, pn)C11, O16(p, α)N13, and F19(p, pn)F18

The activation cross sections for proton-induced nuclear reactions were studied in the region from threshold over a range of about 10 Mev proton energy. The scattering and 180°-focussing technique for proton irradiation was employed to realize improved energy resolution.The reaction O16(p, α)N13 exhibited three large peaks at proton energies of 8.6 Mev, 11.3 Mev, and 14.6 Mev in the laboratory system. The maximum cross sections were 46 mb, 55 mb, and 45 mb respectively.Though not so pronounced as in the oxygen case, minor peaks in the cross section for C12(p, pn)C11 + C12(p, d)C11 modulated the previously smooth curve. These occurred at energies of 19.8 Mev, 20.9 Mev, and 22.2 Mev. The known excitation function for this reaction was extended from 32 Mev to 42 Mev and proved to be flat, thereby clarifying the normalization between the higher- and lower-energy regions.The irradiation of F19 with protons to produce F18 yielded a cross section which was a smooth function of energy, and thus differed in shape from the corresponding carbon curve.

Interpretation on Nitrogen- and Proton-Induced Nuclear Reactions

Excitation functions for α-, 2p- and 2α-emissions are calculated on the basis of the compound nucleus formalism for both of nitrogen-induced reactions on 12C and proton-induced reactions on 25Mg. The result are compared with the observed excitation curves in respective cases. A good agreement between the theoretical and the experimental results in (p; 2p), (p; α) and (p; 2α) reactions indicates that the evaporation theory is valid for explaining the intermediate energy reactions even in those light nuclei. The overall behaviour of observed (N; α) and (N; 2p) excitation curves is in agreement with those obtained by the calculation and suggests that some sort of compound nucleus is formed in the nitrogen induced reaction. However the large magnitude of (N; 2α) cross section cannot be explained by the successive emission of two alpha particles, if the first alpha particle emerges from the conglomorate nucleus proceeding toward the complete compound state. Hence the large (N; 2α) cross section is regarded as due to direct processes such as alpha-capture or stripping. The occurrence of direct processes may explain a small discrepancy in the shape of (N; α) excitation curve at high incident energies.

Comparison of Nitrogen- and Proton-Induced Nuclear Reactions

Excitation functions for ($p, 2p$), ($p, \ensuremath{\alpha}$), and ($p, 2\ensuremath{\alpha}$) reactions on ${\mathrm{Mg}}^{25}$ were measured with the internal 22-Mev proton beam of the 86-inch cyclotron. The results are compared with the excitation functions obtained for the reactions produced by 29-Mev nitrogen ions on carbon in the 63-inch cyclotron. Both sets of reactions may proceed via the same compound nucleus, ${\mathrm{Al}}^{26}$. After corrections for the barrier penetrations of the incident particles, the (N, $2p$) and ($p, 2p$) results are quite comparable. The corrected (N, $\ensuremath{\alpha}$) and (N, $2\ensuremath{\alpha}$) cross sections are larger than those for the corresponding proton-induced reactions by factors of about two and four respectively, indicating that processes other than conventional compound nucleus formation are involved in these nitrogen-induced reactions. The shape of the excitation functions for the nitrogen-induced reactions indicates that the protons and alpha particles are emitted from nearly spherical nuclei with charge equal to that of the compound nucleus; direct interactions such as stripping are thus excluded.