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Interactions of the changing magnetic field of the Sun with the Earth's magnetosphere cause geomagnetic activity. We seek to understand the physical processes that affect the inputs to the terrestrial system and generate geomagnetospheric disturbances. The goal is to understand how solar activity originates, how it is expressed in the corona and interplanetary medium, and how it ultimately affects the terrestrial environment. We are working to develop tools that can, from photospheric observations, reliably forecast the solar events and solar wind conditions that cause the geomagnetic disturbances that impact human activities on and near the Earth., See also ADM002252.

Laser induced bunch lengthening has been measured on the ACO storage ring FEL. The experimental data at low current generally confirms the existing theoretical models, while the high current data is dominated by anomalous effects. As part of the LURE/Stanford Free Electron Laser Project at Orsay, France, we have developed a sensitive method to measure the laser induced change in the electron bunch length. This method is capable of measuring the absolute bunch with a precision of 1%, and fractional changes in electron bunch length as small as 1 part in 100,000. Using this system, we have measured the steady state and time dependent laser induced bunch lengthening as a function of electron current, external laser intensity, RF cavity voltage, the undulator magnetic field, and the detection frequency.

The final report for this contract consists of two articles submitted for publication in the open literature. In the first article the authors describe an approximation they have used to compute gain, saturation, and electron statistics for a free electron laser. In the second article they report the results of a Monte Carlo method one-dimensional analysis of the equilibrium energy spread, bunch length, and average energy radiated by electrons in a storage ring free electron laser. (Author)

A compact tunable hybrid undulator was built for use in a small free-electron laser. The design and adjustment procedures, as well as the results of measurements on the wiggler and lasing performance are summarized here., This article is from 'International Conference on Insertion Devices for Synchrotron Sources Held in Stanford, California on 27-30 October 1985,' AD-A176 377.

Operation of a high gain VUV/Soft X-Ray Free Electron Laser (FEL) oscillator on the Stanford X Ray Center (SXRC) storage ring is investigated. Laser energy and emittance acceptance in the high gain regime for XUV light are examined using the FEL amplifier simulation code FRED. Assuming 50% mirror reflectivity, oscillation is shown to be feasible down to 220 A with a realizable wiggler magnet placed in the 27 meter straight section of the 1 GeV SXRC ring. Laser output power and time structure are determined for a 960 A oscillator operating in both 'cw' and slow pulsed modes., This article is from 'International Conference on Insertion Devices for Synchrotron Sources Held in Stanford, California on 27-30 October 1985,' AD-A176 377.

The major activities are listed; 1. Design a single-cell accelerating cavity suitable for a modest power FEL system, and demonstrate by operation of a prototype cavity the feasibility of achieving gradients exceeding 6 MeV/m.; 2. Find a geometry for a single harmonic cavity that is suitable for use in the harmonic injector system. Operate a prototype harmonic cavity at high gradient. 3. Design an injector system incorporating harmonic acceleration and magnetic bunching; 4. Construct and test a prototype injector system incorporating harmonic acceleration with an output energy of approximately 3 MeV; and 5. Study the feasibility of a compact and efficient accelerator suitable for FEL systems that utilizes beam recirculation both for energy doubling and for energy recovery.

The first visible linac free-electron-laser (FEL) oscillator has been operated above threshold at the wavelength of 526 nm with and without a taper. Peak output power of 170KW with a macropulse average power of 1.1 watts was observed. The cavity dielectric mirrors were damaged at approximately 140KW sq cm of average power in the presents of UV from the FEL harmonics. The gain and efficiency were much less than predicted due to developed wiggler field errors., Prepared in cooperation with Stanford Univ., High Energy Physics Lab.

Laser induced bunch lengthening has been measured on the ACO Storage Ring Free Electron Laser (SRFEL) in the anomalous bunch lengthening regime. The experimental results show correlations between the appearance of coherent modes in the electron bunch and anomalous behavior in the presence of the laser. Simultaneous time resolved laser induced bunch lengthening, mode strength, bunch length, and synchrotron sideband measurements were made as anomalous thresholds were traversed several times by changing the ring laser accelerating voltage. Bunch shortening, multiple time constants, and oscillatory behavior are among the phenomena which have been observed. (Author), Presented at the Particle Accelerator Conference, Mar 83, Santa Fe, NM. Prepared in cooperation with Paris Univ. Orsay (France). Laboratoire de Photophysique Moleculaire and Deacon Research, Palo Alto, CA.

Ti02/Si02 multilayer dielectric mirrors centered around 630 mm have shown reflectivity degradation from 99.99% down to 99.0% due to UV synchrotron radiation emitted by a beam of 240 MeV electrons during a storage ring free electron laser experiment., Prepared in cooperation with Paris Univ. Orsay (France).

This document discusses current problems in storage ring laser development: optics degradation, and the low gain available on unoptimized existing electron sources. The authors introduce the field with experimental data, and conclude with the most recent results. (Author)

To improve the gain in the Orsay storage ring free electron laser experiment, the seventeen periods permanent magnet undulator was modified into an optical klystron. The author report the laser induced bunch lengthening and the gain measurement on the optical klystron and compare these to the undulator case. (Author), Prepared in cooperation with Paris Univ.-Sud, Orsay (France). Presented at International Conference on Lasers '82, New Orleans, LA, 13-17 Dec 82.

We report the results of the first gain measurements on the free electron laser being assembled on the storage ring ACO. The largest measured peak gain, averaged over the laser mode, is G = 4.3 x 10 to the -4 per pass. No laser induced bunch lengthening is observed within the experimental accuracy of 50 psec under a laser intensity of 1.6 kw/squared cm and under the conditions of strong anomalous bunch lengthening (ot/ot (I=O)) = 6.8 - 4.2. (Author), Presented at the Particle Accelerator Conference, 1981.

The study of elastic electron scattering from nuclei, at angles near 180 degrees, permits an examination of nuclear magnetic multipole distributions as well as the testing of certain aspects of quantum electrodynamics. Apparatus has, therefore, been designed to enable such experiments to be performed at the Stanford Mark III linear accelerator. The special problems connected with 180 degrees elastic scattering are discussed. In general, it is necessary to subtract from the data, contributions from ordinary charge (Coulomb) scattering. This background is mainly due to electrons which scatter at angles other than 180 degrees and yet enter the detector because of multiple scattering in the target, finite beam spread and finite solid angle. 180 degrees scattering is achieved by passivng the incident beam through a magnetic field before it strikes the target. Backward scattered electrons then pass through the field a second time, bending away from the incident beam, and enter a spectrometer. The momentum range restrictions of the magnet optics and the optimization of the solid angle are discussed. A novel method is presented of varying the scattering angle around 180 degrees without causing significant phase space restrictions. Practical details of the apparatus are discussed and an outline of the data reduction methods used in such experiments is presented. (Author)

The presence of two magnetic spectrometers in the end station of a linear accelerator has opened a new field of research in electron scattering problems. The problem of e-p coincidences in deuterium is being studied with the detection of relatively energetic protons (above 50 Mev). The neutron form factors can be obtained more easily from the measurement of the e-n coincidence (with the detection of high-energy neutron) or the coincidence e-p (with low- energy proton, less than 10 Mev). The experiment discussed here is an attempt to find a value for the proton form factors in a bound state and see if they are equal to those obtained for a free proton., Technical Report Linear Electron Accelerator Project.

The (gamma, proton) reaction in O, F. Ne, and C was studied with electrons of energies up to 36 mev. Survey studies were made of the Al, A, and B (gamma, proton) energy spectra. The studies were based on a one-to-one correspondence between electron- and photon-induced reactions. It was assumed that when analyzing electronproduction yields, the electron as associated with it a virtual-photon spectrum, similar to the real-photon bremsstrahlung spectrum. The virtual and bremsstrahlung spectra differ in the virtualphoton spectrum depends on the multipolarity of the induced transition and the angle between the incident electron beam and the emitted disintegration product. The el ctron production yields were analyzed with the use of the E-1 virtualp oton spectrum.

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.

The purpose of this paper is to report results of higher resolution measurements on O16 using the Stanford Mark II linear accelerator.

Design of a linear electron accelerator.

The photodisintegration of the deuteron has been studied at energies comparable with the second and third pion-nucleon isobars using the Stanford Mark III linear electron accelerator. No evidence has been found for any resonant behavior in the energy region of interest. (Author)

Elastic and inelastic electron scattering from C12 and O16 has been studied for various scattered electron angles, using primary beam energies from 600 to 800 MeV. These studies cover a range of the square of the momentum transferred to the nucleus. A procedure for subtracting the effects of energy loss due to radiation of the electrons is developed. With the resolution obtained in this experiment it is possible to resolve elastically scattered electrons from inelastically scattered electrons. In many instances it is also possible to resolve electrons which have excited discrete nuclear levels in C12 and O16. Inelastic electron scattering due to excitation of nuclear levels is observed from the 4.43 MeV, 2(+) and 9.6 MeV, 3(-) levels in C12; and for the 6.1 MeV levels in O16. Differential cross sections for excitation of these levels as well as for elastic scattering are determined. Absolute values of the cross sections are obtained by comparison with known absolute proton cross sections. Analysis of the data using first Born approximation shows that the root mean square radii of C12 and O16 are 2.40 + or -0.02 F and 2.65 + or -0.04 F respectively. (Author)

Measurements of the differential cross section have been made at several angles for photon energies in the range 550-1000 MeV, using the Stanford Mark 3 linear accelerator. The pi(-) were detected and momentum analyzed using a 90 degree magnetic spectrometer. (Author)

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)

Experimental results are reported about the electromagnetic properties of excited states below the giant resonance' in O16 using 180 deg inelastic scattering of electrons with incident energies of 43, 59 and 69 MeV. A comparison is made with the transverse form factors for inelastic electron scattering from 1, T = 1 states, calculated by Lewis, and from 2, T = 1 states calculated by deForest on the basis of the particle-hole model of the nucleus. Combined with known photon absorption cross sections, the interpretation of all the available data for the 13 MeV level required a 1 state to account for the photon point and the 2 state for the high q points. For the level at 17 MeV the theory is about a factor of 2 higher than the electron scattering results. The peak observed at 20.2 MeV has a transverse form factor with a q-dependence that follows within a factor of 2 the theoretical results for the strong 2 state calculated by deForest. Properties of levels at 11.00 and 12.0 MeV excitation are also discussed. (Author)

A new limit on the electron's electric dipole moment at high momentum transfer has been determined by scattering 100 Mev electrons at 180 deg, from C12 nuclei. A full discussion of the theory involved and the experimental corrections due to multiple scattering, etc, is given. Assuming that the electron possesses no spurious magnetic moment, apart from the well established Dirac and anomalous moments, its electric dipole moment is 2.3 x 10 to the -16th power e-cm at a momentum transfer of 1.0/Fermi. The result is consistent with Time-Reversal invariance in quantum-electrodynamics. (Author)

The 4.431 MeV nuclear excitation in Na-23 was observed by measuring the electron energy spectrum resulting from inelastic scattering of 58.5 MeV primary electrons through an angle of 180 degrees. It is shown that this excitation is most likely due to a magnetic dipole transition. The integrated inelastic electron scattering cross section for this level was found to be (0.48 = 0.05)10 to the (minus 32) power sq.cm./sr. (Author)

The importance of two-photon exchange in elastic electron-proton scattering was investigated by measuring the ratio of positron-proton to electron-proton scattering. Four momentum transfers as large as 0.756 (BeV/c) to the 2nd power (19.5 F to the -2nd power) were used. The data indicate that two-photon effects are 4.0 = 1.5% larger than those predicted by the radiative corrections at the highest momentum transfers attained in these experiments. The two-photon corrections predicted, using a static charge distribution, fit the data well at lower momentum transfers and forward angles but appear to be small at higher momentum transfers and backward angles. (Author)

The elastic scattering of high-energy electrons from the magnetic dipole and magnetic octupole moments of light nuclei is calculated using shell model wave functions. The results of the calculation are compared with recent experimental results for Be-9 and B-11 and the possibility of obtaining a value for the magnetic octupole moment from an analysis of these experiments is discussed. (Author), In cooperation with Institute of Theoretical Physics, Stanford Univ., Calif., Contract AF49 638 1389.

Pion photoproduction from nucleons has proved a useful tool in the study of the pion-nucleon interaction because of the dominance of the strong final-state interaction between emitted pion and recoil nucleon. There has remained, however, a noticeable lack of data at high momentum transfer in the region of the second pion-nucleon resonance. In particular, the zero angle measurement provides an important test of the hypothesis that the direct photo-electric term is responsible for the difference in position of this resonance in pi o and pi = photoproduction. The present experiment was designed to study this region using the Stanford Mark III linear accelerator. The results of the experiment establish that the discrepancy in resonance positions is not due to the photo-electric term, and also establish the possibility of a high momentum transfer enhancement of pi o photoproduction caused by crossed nucleon and nucleon isobar exchanges. The paper is divided into into five parts. In Section II, the experimental equipment and techniques are described. Section III contains an account of the data reduction, and the results are then interpreted in Section IV. Finally, in Section V, general conclusions are drawn. (Author), In cooperation with Institute of Theoretical Physics, Stanford Univ., Calif. Contract AF49 638 1389.

Presented at the 50th National Congress of the Italian Physical Society, 1964, Catania.

Using the non-relativistic wave equation, an investigation is made of the Coulomb induced change in binding energy and R.M.S. radius for a two-body, s-wave state. Exact results are given for square well attractive nuclear potentials to which Coulomb repulsion is added. Possible implications for the three-body mirror pair, He3, H3 are discussed. (Author)