Search

Polarized beam commissioning has been initiated at TJNAF. Measuring the polarization properties of the accelerator, which consists of two superconducting linacs and more than 2200 magnetic elements at its maximum energy, provide useful information about the beam energy and beam transport through the accelerator. Stability of the output beam polarization depends upon time-dependent orbit and energy oscillations. Modeling indicates that the spin transport dynamics are sensitive (∼10−2) to vertical betatron oscillations in the recirculation arcs. This sensitivity is calculated to be enhanced in the arcs where the spin tune is most nearly matched to the vertical betatron tune. Modeling also suggests that depolarization phenomena associated with the particle trajectory differences for electrons within the accelerator’s nominal transverse phase volume are too small to be measured between the injector and an experimental hall. Preliminary results from measurements obtained during polarization development runs wi...

Low energy (Ek=100 keV) Mott scattering polarimeters are ill-suited to support operations foreseen for the polarized electron injector at Jefferson Lab. One solution is to measure the polarization at 5 MeV where multiple and plural scattering are unimportant and precision beam monitoring is straightforward. The higher injector beam current offsets the lower cross-sections. Recent improvements in the CEBAF injector polarimeter scattering chamber have improved signal to noise.

The new generation of electron accelerators provides higher energies, luminosities, and/or duty factors, and presents important physics opportunities for electro‐weak interaction studies and experiments that exploit the spin degrees of freedom in electron scattering. Recent developments in polarized electron source technology promise dramatic improvements over earlier experiments. We review the status of these sources, with emphasis on those best suited for accelerator applications.

Recent theoretical and experimental investigations of the (e, e’γ) reaction show that it provides a probe of unparalleled precision and selectivity. Experiments aimed towards the isolation of multipole form factors in mixed transitions, the study of continuum excitations in nuclei, and the measurement of the response of the proton are underway at several laboratories.