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A long pulse, high brightness 45 MeV linear accelerator has been constructed for use as a driver for free electron laser and beam wave experiments, and as the first section of a 1 GeV injector for a high brightness electron storage ring. This contract has led to: 1. demonstration of the highest gradient and longest pulse length yet achieved in a 3 meter S-band SLAC-type travelling wave accelerator section; and 2. demonstration of the high current and high current density attainable through the use of a strong microwave field to replace the dc electric field usually used in linac electron guns.

The basic objective of this research was to determine the feasibility of the conversion of the Stanford Mark III linac to high-gradient operation to serve as an injector or driver for storage ring and single pass free electron laser experiments. The Mark III single section tests have been generally successful. In particular, it has been observed that the Mark III accelerator sections are capable of operating reliably and stably at high gradient if an appropriate vacuum is maintained in the structure, and if appropriate steps are taken to bake out the adsorbed contamination on the cavity walls. Electrons have also been accelerated in the test section to an energy in excess of 40 MeV., Personally Identifiable Information (PII) was redacted.

The cross section for elastic electron scattering from an enriched Ca48 target is measured in comparison with one for Ca40. The angular dependence of the ratio of these two cross sections is fitted by a curve calculated by phase shift analysis. The best fitting values for the changes in the parameters defining the charge distributions of these nuclei lead to the conclusion that the half-way radius increases by 4.1% and the skin thickness decreases by 12.4%, under the assumption that the charge distribution of both nuclei follow the so- called parabolic Fermi model., Prepared in cooperation with General Motors Corp., Warren, Mich. Research Labs. and Illinois Univ., Urbana. Dept. of Physics.

Elastic electron scattering cross sections have been measured for 6Li at 500 MeV and values of q sup 2, the momentum transfer squared, up to 13 f(m sup (-2)). Calculations including nucleon-nucleon correlations predict a diffraction minimum beyond the range of previous measurements for 6Li. The results for 6Li do show a diffraction minimum at q sup 2 = 8 f(m sup (-2)); they are also compared with a phase shift calculation using an empirical charge distribution. (Author), Sponsored in part by National Science Foundation, Washington, D. C.

The differential scattering cross sections have been measured for electron scattering from randomly oriented and aligned Ho165 nuclei. The alignment axis was parallel to the direction of the momentum transferred to the nucleus. Incident electron energies from 160.6 MeV to 462.2 MeV were used at a fixed polar scattering angle of 36 degrees. Available theories are unable to explain the measured difference between the aligned and non-aligned cross sections. (Author)

The electromagnetic structure of the He3 nucleus has been investigated by means of high energy electron scattering. A separation of the charge and magnetic form factors has been accomplished. The charge form factor data extend to q squared = 20 fm sup ( -2) and exhibit a diffraction minimum at q squared = 11.6 fm sup ( -2); the magnetic scattering is measured to q squared = 12.5 fm sup ( -2). The results are discussed in terms of models for the charge and magnetic distributions of the nucleuus. (Author)

High energy electron scattering has been used to deduce the nuclear charge distribution of the isotopes 142, 144, 146, 148, 150Nd. The measured cross sections have been fitted using a two- and a three-parameter Fermi shape. A significant increase of the surface thickness between 142Nd and 150Nd is observed. The data for 142Nd at high momentum transfer can only be fitted by introducing a modification on the charge distribution which is due to shell model effects. (Author)

Previous measurements of the transition probabilities for low energy excitations in Carbon-12, using high energy electron scattering techniques, required considerable extrapolation of the data to obtain the desired results. The paper reports the results of new data obtained at lower values of momentum transferred to the nucleus. Transition widths for the three lowest energy excited states in Carbon-12 were determined using the new data. The results of the experiment allow a much greater confidence in the method employed in this study for determining transition widths. (Author)

Measurements are reported of the inelastic scattering of electrons from the mirror nuclei of tritium and helium - 3. The ratio of the quasi-elastic electron-tritium and electron-helium -3 cross sections was measured to a precision of about 3% for values of the square of the four-momentum transfer, equal to 2.5 and 4.6/F sq. Detailed measurements of the shape of the entire inelastic spectra and estimates of the total inelastic cross sections were made. While these data are primarily intended to furnish additional experimental information which will be of use in determining the structure of the three-body nuclei, it is also pointed out that such data are a possible source of information on the structure of the neutron. (Author)

Using a liquid helium target a study was made of elastic electron scattering from He4 at values of q sq., the 4-momentum transfer squared, ranging from 0.5 F to the -2 power to 10.0 F to the -2 power. The results were interpreted in terms of the charge form factor of the alpha particle. Previous Stanford measurements extended up to q sq = 6.2 F to the -2 power and were consistent with a Gaussian charge distribution. The form factor values obtained recently by Repellin et al, at Orsay from a measurement of relative cross sections up to q sq. = 8 F to the -2 power indicated a deviation both from the earlier Stanford data and from the Gaussian model. The results confirm the original Stanford data but do show a deviation from the Gaussian model for q sq > 6 F to the -2 power. The qualitative trend of the deviation is the same as observed by Repellin et al, whereas the absolute form factor values are in disagreement. Among the models which have been found to fit the new data are the Modified Gaussian charge distribution, and the independent particle model using a finite square well. (Author), To be submitted to Phys. Rev. Letters.

Measurements of the ratio of the total inelastic electrondeuteron cross section to the elastic electron-proton cross section were made to an accuracy of about 3% for values of the square of the four-momentum transfer in the range 1.5 to 7.5/F-sq. These ratios were analyzed in terms of the form factors of the neutron using the 'area method', and it is concluded that the corrections necessary to the simple sum rule given by Jankus are approximately equal in magnitude to those encountered in the use of the more familiar 'peak method'. A detailed comparison was made between the shapes of the observed inelastic electrondeuteron cross sections as a function of the scattered electron momentum and the shapes expected according to a theoretical treatment due to Durand. (Author)

Measurements of magnetic (elastic) electron-deuteron cross sections at q-sq = 6.0, 7.0, 8.0, and 12.0 1/F-sq. Electric scattering was also observed at these q-sq values, as well as at one additional point (q-sq = 20.0 1/F-sq). An analysis of these data definitely indicates that ahe simple impulse approximation model of the deuteron, incorporating the best possible values for the nucleon form factors, is inadequate to explain the experimental results.

Absolute measurements of the elastic electron-proton cross section have been made with a precision of about 4% for values of the square of the four-momentum transfer, q to the second power, in the range 6.0 to 30.0 F to the minus second power and for electron scattering angles in the range 45 to 145 degrees. To within the experimental errors, it is found that the charge and magnetic form factors of the proton have a common dependence on q to the second power, when normalized to unity at 1 to the second power = 0, and than an accurate representation of the form factor behavior and that of the cross sections themselves can be given in terms of a three-pole approximation to the dispersion theory of nucleon form factors. (Author)

The electromagnetic form factors of the neutron have been measured in the q-squared range from 1.0 to 30.01/F sq. It is found that for values of q-squared greater than about 6.01/F sq the square of the neutron's charge form factor is consistent with zero to within an error of the order of 5% in the existing theoretical cross section. For values of q-squared less than 6.01/F sq it is concluded that meaningful values of the neutron form factors cannot be given until the necessary corrections to the theory are better understood. The present results on the neutron form factors are combined with recent measurements of the proton form factors to provide experimental determinations of the isotopic nucleon form factors. It is found that the omega and phi mesons provide a good approximation to the observed isoscalar form factors but that it is difficult to understand the behavior of the isovector form factors in terms of the rho meson alone. (Author)