Medium Energy Proton Research Articles

Residual Radiation Studies for Medium Energy Proton Accelerators

Residual radiation levels to be encountered in medium energy proton accelerators at high beam intensity are evaluated. Excitation function data were obtained for the production of the most probable radionuclides. A computer code that takes into account the change of cross sections as the beam penetrates the target material was used to compute residual radiation dose rates for carbon, aluminum, iron, and copper as functions of bombardment time and cooling time.

Fission of Heavy Elements Induced by Medium High Energy Protons

Fissionability, mass distribution, charge dispersion and distribution, and neutron emission for fission induced in heavy targets (uranium) by protons with a few hundred MeV kinetic energy are presented and phenomenologically discussed. The results are interpreted in order to arrive at the reaction mechanisms in medium high energy induced fission.

Quasi-Free Scattering and Nuclear Structure

As you see from the title of my talks, I have narrowed down the general subject of “Nuclear Structure Effects with Proton Probes”. I understand that Dr. Beurtey will among others discuss the elastic and inelastic scattering of medium energy protons; it seems to me that the quasi-free process is the simplest reaction occurring in this field and that it is the one which has given the most significant information on the structure of the nucleus. However this may be just my personal prejudice.

Calculation of Elastic and Inelastic Proton Scattering with a Generalized Optical Model

An extension of the optical model is considered in which a state of quadrupole collective motion is strongly coupled to the nuclear ground state. The calculations include a spin-orbit potential and the simultaneous coupled differential equations of the problem are solved numerically on a high-speed computer. Experimental data on the scattering of medium energy protons from Ti, Cr, fe, Ni, and Zn are analyzed. A good average optical potential is determined and conclusions are drawn about the energy dependence of the parameters. Evidence is presented for the validity of the collective model. Nuclear deformabilities derived by fitting the inelastic differential cross sections are in agreement with those determined by electromagnetic methods. Various limitations and ambiguities of the model are discussed and possible improvements are indicated. (auth)

Range-Energy Relations for Protons and Alpha-Particles in Various Explosives

Abstract : Differential energy loss (Mev/mg/sq cm) and range (mg/sq cm) data were calculated for low and medium energy protons and alpha particles in the following eight explosives: RDX (cyclotrimeth ylene trinitramine), HMX (cyclotetramethylene tetranitramine), TNT (2,4,6-trinitrotoluene), PETN (pentaerythritol tetranitrate), tetryl (2,4,6-trinitrophenyl methyl nitramine), lead styphnate, mercury fulminate, and lead azide. The well-known Bethe theory was followed in establishing the proton ranges. Experimental proton differential energy loss data and theoret ical computations were used to establish atomic stopping number versus energy curves for the elements hydrogen, carbon, nitrogen, oxygen, and lead between 20 Kev and 25 Mev. From these curves, molecular stopping numbers were calcu lated. The alpha-particle ranges were obtained from the established proton ranges.

Recoil Studies of Reactions of Indium with Medium Energy Protons and Alpha Particles

Recoil ranges projected along the beam direction have been measured for the ( alpha , alpha gamma ), ( alpha , alpha n), ( alpha ,pn), and (p,p gamma ) reactions on In/sup 115/ and for the In/sup 113/(p,n) reaction, with 5 to 10 Mev protons and 20 to 40 Mev alpha particles. The results have been compared with values expected for compoundnucleus formation and reasonable agreement is obtained for the ( alpha ,pn), (p,p gamma ), and (p,n) reactions. The measured range for the ( alpha , alpha n) reaction agrees with calculation at the lowest energy studied but is somewhat low at the highest bombarding energy. In the case of the ( alpha , alpha gamma ) reaction the measured ranges are a factor of 3 to 6 smaller than the calculated values, indicating a direct interaction process. The recoil ranges expected for Coulomb excitation have been computed for the ( alpha , alpha gamma ) and (p,p gamma ) reactions and are substantially smaller than the experimental values. Excitation function measurements for the ( alpha ,pn) reaction are also presented. (auth)

Gamma-radiation from the medium energy proton borbardment of sodium, magnesium, aluminium, silicon phosphorus and sulphur

Measurements are presented of the gamma-radiation from the residual nuclei produced in nuclear reactions induced by 150 MeV protons on sodium, magnesium, aluminium, silicon, phosphorus and sulphur nuclei. It is found that only a small number of gamma-rays are produced strongly. This is explained as being due to the importance of comparatively simple direct reactions at this energy, combined with the way the energy level schemes of these nuclei can be understood as energy level schemes of distorted nuclei, an application of the unified model. It is shown that inelastic scattering cross-sections are determined by the same matrix elements as the corresponding radiative transitions, so that only a small number of states are excited strongly by inelastic scattering in these nuclei. The (p, 2p) and (p, pn) reactions produce the parent states of the struck ground state. It is shown that, in the unified model, the parentage of the ground state of a distorted 4n-nucleus collects into a very few states of the parent (4n-1)-nucleus, in agreement with our experimental results. The gamma-rays also show the apparent importance of interactions of the incident proton with clusters in the target nucleus. In particular we note the importance of the (p, pt) reaction on bombarding (4n-1)-nuclei and of the (p, pα) reaction on bombarding 4n-nuclei, both these reactions leaving the residual nucleus in its ground state rotational band.

Gamma Ray Angular Correlation in the Inelastic Scattering of Medium Energy Protons from the First Excited State of12C

Measurements are reported of the polarization of the first excited state of 12C produced by inelastic scattering of 150 MeV protons through several angles, the polarization being indicated by the angular correlation of the decay gamma rays. The results are analysed to obtain information about the details of the inelastic scattering interaction. In particular they show that much the same nuclear wave-functions are involved in this medium-energy proton reaction as in low-energy reactions.

The7Li(p,p') Reaction at 150 MeV

Measurements are reported of the inelastic scattering of 150 MeV protons from the first excited state of 7Li. The results are compared with other measurements of inelastic scattering from higher states of 7Li and support the identification of the low-lying negative parity states of 7Li as a rotational band in a distorted nucleus. It is remarked that measurements of the polarization of the outgoing proton from inelastic scattering of medium energy protons from 1p-shell nuclei give further support to the identification of rotational bands in these nuclei.

Gamma Radiation from the Medium Energy Proton Bombardment of Lithium, Beryllium, Boron, Carbon and Nitrogen

Measurements are presented of the gamma radiation produced when lithium, beryllium, boron, carbon and nitrogen are bombarded with 150 MeV protons, and the results are discussed with reference to the information they provide about the structure of the nuclei involved. The results include measurements of the residual states produced in (p, 2p) and (p, pn) reactions, which are, to a first approximation, measurements of the parentage of the ground state of the bombarded nucleus. These results are not consistent with a simple jj-coupling model of these nuclei and in one case where calculations are available, are consistent with an intermediate coupling model. It is shown that inelastic scattering cross sections are determined by the same matrix element as radiative transitions so that inelastic scattering is a powerful tool for picking out strong radiative transitions to nuclear ground states.

Rotational bands in the 1p-shell

Abstract It is noted that certain states of 1p-shell nuclei are strongly excited in the inelastic scattering of medium energy protons from these nuclei while other states are weakly excited. It is suggested that these observations can be understood if these nuclei are distorted, with rotational bands. The connection with other nuclear models of the 1p-shell is discussed.

Elastic and Inelastic Scattering of Protons by Oxygen in the Energy Region of 6.9 MeV to 15.6 MeV

Extensive experimental results are presented, showing the variation with energy of the absolute angular distributions for the elastic and inelastic scattering of medium energy protons on oxygen. For the elastic scattering, angular distributions between 20 deg and 160 deg were obtained for twenty incident proton energies spaced between 6.87 MeV and 15.6 MeV. The absolute angular distributions for the inelastic proton groups, leading to the excitation of about 6 MeV (6.06 and 6.14 MeV) and 7 MeV (6.92 and 7.12 MeV) states of O 16 , were measured at five energies from 11.9 MeV to 15.6 MeV. Although angular distributions vary remarkably with the incident energy, integrated cross section decreases monotonically as incident energy increases. In particular, at E p =15.6 MeV the total inelastic scattering cross section was roughly measured to be 240±40 mb. From this result and the reported results for other reaction cross sections, we may deduce that O 16 nucleus is considerably transparent even for this rather high incident energy, where the mean free path of nucleon in nuclear matter has nearly the minimum value in usual nuclei. The excitation function for the elastic scattering shows appreciably sharp resonances at energies, 7.2, 10.6 and 14.7 MeV, and its gross structure has a large scale resonance of a width about 4 MeV, at incident energy of about 13 MeV. It appears that this resonance is the f -wave giant resonance expected from the shell model.

Some Cross Sections for the Production of Radio-Nuclides in the Bombardment of C, N, O, and Fe by Medium Energy Protons

A number of nuclide formation cross sections have been measured, using the Berkeley 184-in. cyclotron, to assist in the interpretation of the data on cosmic-ray-produced nuclides in the atmosphere and in iron meteorites.Cross sections of ${\mathrm{H}}^{3}$ and ${\mathrm{Be}}^{7}$ have been measured in bombardments of organic targets containing nitrogen and oxygen by protons of energy 225-730 Mev. Semicarbazide (C${\mathrm{H}}_{5}$${\mathrm{N}}_{3}$O) targets were used to obtain cross sections in air nuclei. The targets were prepared by mixing with a few percent of aluminum dust to permit reliable monitoring of the beam. Polyethylene, aluminum lactate, and Plexigals targets provided elementary cross sections in carbon and oxygen.The cross sections for the production of the long lived isotopes ${\mathrm{Cl}}^{36}$ (3\ifmmode\times\else\texttimes\fi{}${10}^{5}$ yr) and ${\mathrm{Al}}^{26}$ (8\ifmmode\times\else\texttimes\fi{}${10}^{5}$ yr) at 730 Mev, and of a number of short lived radionuclides at 500 and 730 Mev, in iron bombardment by protons have been measured. These data and those of earlier workers suggest some modifications in empirical relations used for predicting spallation cross sections in the case of nuclides close to stability

Differential Cross Sections for the Scattering of Medium Energy Protons on Carbon

Extensive experimental results are presented showing the variation with energy of the absolute angular distributions for the elastic and inelastic scattering of medium energy protons on carbon. For the scattering with $Q=0$ and $Q=\ensuremath{-}4.4$ Mev, angular distributions between 20 deg and 170 deg were obtained for eleven incident proton energies spaced between 14.0 Mev and 19.4 Mev. Distributions for scattering leading to the excitation of the 7.7-Mev and 9.6-Mev states of ${\mathrm{C}}^{12}$ were measured at energies of 16.7, 17.8, and 18.9 Mev. The experimental results are discussed qualitatively in their relation to the predictions of the theories of nuclear reactions. The elastic scattering cross sections are roughly what one might expect from the complex potential theory, but no numerical comparisons have been made. The predominant inelastic scattering is forward, though the angular distributions corresponding to the three levels studied do not resemble each other. In no single case is one of these distributions symmetrical about 90 deg. The simple Bessel-function distributions of the first-order direct interaction theory do not agree well with the data, but only the scattering leading to the 4.4-Mev level of ${\mathrm{C}}^{12}$ is in apparently complete disagreement.Experimental differential cross sections as a function of energy are also presented for the scattering of protons on hydrogen near 90 deg (center-of-mass system).

The Study of the Diffraction of Protons of Medium Energy by Vapor Molecules

The diffraction of 15–20 kv protons by carbon tetrachloride vapor has been investigated with a low voltage arc source and electrostatic focusing with photographic registration. The principal difficulties encountered were with space charge dispersion of the beam near the ion source, and with neutralization of the beam as it passed through the vapor. The cross sections for neutralization and re-ionization of protons and hydrogen molecular ions in several gases and vapors were determined. The sensitivity of photographic film was found to diminish as the emulsion was outgassed but to increase fifteen-fold when it was treated with oil. When suitable precautions were taken to minimize the background scattering, diffraction patterns were obtained showing three maxima, the measurements of which are in satisfactory agreement with electron diffraction data.