[en] I discuss in this talk the physics of the Q² dependence of the G_l(x,Q²) structure function sum rule. For Q² > 3 GeV², the Q² variation is controlled by pure QCD radiative corrections. For 0.5 < Q² < 3 GeV², the twist-four contribution becomes significant, but stays perturbative. For Q² below ∼ 0.05, the sum rule is determined by low-energy theorems. The rapid change of the sum rule between 0.05 and 0.5 GeV² signals the transition between parton and hadron degrees of freedom

[en] The spin structure function g₁^p of the proton has been measured b deep inelastic scattering of polarized muons from polarized protons. The data were taken over the kinematic range 0.003 ≤ x B_j ≤ 0.7 and 1 GeV² ≤ Q² ≤ 60 GeV². The first moment Γ₁^p = ∫₀¹G₁^p(x)dx was evaluated and compared to the I Ellis-Jaffe sum rule. The consistency of existing proton deuteron and neutron data is discussed. Combination of the data allows a test the fundamental Bjorken sum rule which is confirmed at the level of 10% of its theoretical value, when high QCD corrections are considered. The contribution of the quark spins to the nucleon spin is evaluated within the quark-parton model

[en] The properties of polarimeters used in a number of Laboratories, to measure the polarization of secondaries produced in a nuclear target, in the range of energy 100 MeV to 12 GeV, are reviewed. The nature of polarization experiments will be discussed and several examples of new experiments used to illustrate the power of this technique. New development both for protons and for deuterons win be discussed in some details. Calibrations data and fits both for protons, to 2.4 GeV, and deuterons, to 700 MeV, will be presented

[en] Complete characterization of the electromagnetic nuclear current in (rvec e, e'rvec n) reactions require a decomposition of the virtual photon spin-density-matrix coupled with measurements of initial- and final-state spin polarizations. Theoretical analysis reveals a wealth of information with different amplitudes demonstrating quite different sensitivities to the various ingredients of the reaction mechanism. Recent technological advances including development of polarized targets and recoil-polarimeters have made a first generation of experiments possible. Much of the initial effort has been directed. at extracting G_En from (e,e'n) experiments on deuterium and ³He targets. The quasifree assumption underlying these experiments can itself be put to a rigorous test by performing the analogous (e,e'p) experiments. Beyond these measurements, a complete study of these elementary systems is expected to greatly enhance our understanding of two- and three-body currents which is vital for the construction of the short-range nuclear force. Scattering from single-particle orbits in complex nuclear systems provides a convenient spin-isospin filter. This can be used to study selected components of the effective interaction, providing complimentary information to on-going hadron scattering experiments. At the higher Q² of the CEBAF laboratory, one can expect that complex systems will also be used as a laboratory to study the composition and propagation of nucleons in nuclear matter. For example, polarization transfer in quasifree knockout of protons from the nuclear interior can be examined to determine if the effective G_E/G^m ratio varies from that of the free proton. One can also examine those amplitudes that vanish in the impulse approximation to see if there is a systematic weakening of the FSI at high Q², which might be a precursor for the onset of color transparency

[en] Recent developments of strained layer and multilayer semiconductor photocathodes permit reasonably reliable delivery of low average current electron beams with beam polarization of 80 percent or greater. Work is in progress at several laboratories to improve the quantum efficiency of these photocathodes, permitting operation at higher average beam current as required by facilities such as CEBAF. Developments which so promise to improve the operational reliability and open-quotes up timeclose quotes from such cathodes are also underway. The most recent operational experience with these polarized sources win be reviewed, and the improvements likely from the developmental work will be discussed

[en] Polarized targets using the method of dynamic nuclear polarization (DNP) are in use in many laboratories. The method of DNP is reviewed briefly and the technical developments presented at recent meetings are discussed. The operation of target systems at SLAC and CERN are presented as examples. The emergence of frozen HD as a possible target is discussed

[en] Aspects of the spin responses functions of protons and neutrons at low and intermediate momentum transfers and energy transfers are discussed, with emphasis on the region of the nucleon resonances. Experiments at CEBAF will use polarization to measure inclusive asymmetries A_l^p, A₂^p and A₁ⁿ in a large Q² and W range, the electric formfactor of the neutron, and resonance excitations in pion and vector meson production

[en] The deep inelastic polarized structure fimctions g₁^p,d and g₂^g,d have been recently measured at the Stanford Linear Accelerator Center (SLAC) End Station A facility by the E143 Collaboration using 29.1 GeV, 16.2 and 9.7 GeV longitudinally polarized electrons incident on longitudinally and transversally polarized ammonia (NH₃) and deuterated ammonia (ND₃) targets. Polarized electrons were produced by photemission from a strained GaAs cathode that produced beam polarizations of 85%, measured using a Moller spectrometer with coincidence and single arm detectors. The polarized target operated in a 5 T magnetic field at 1 K. Average dynamic nuclear target polarizations (at 80 nA average beam current) of 60% for protons and 30% for deuterons have been attained. The scattered electrons were detected in two spectrometers placed at 4.5 degrees and -7 degrees with respect to the incident beam.The range of the kinematic scaling variables x_Bjorken and momentum transfer Q² covered at 29.1 GeV is 0.03 to 0.76 for X_B and 1.25 GeV² to 9.7 GeV² for Q², for invariant masses W > 2 GeV/c² in the deep inelastic region. The 29.1 GeV longitudinal data has been analyzed'for protons and deuterons, and combined to extract the neutron structure. The results indicate that the extrapolated integrals of the structure functions Γ₁^p andΓ₁^d evaluated at the fixed Q² = 3 GeV² are not in agreement with the theoretical predictions by Ellis and Jaffe. The combined integral Γ₁^p - Γ₁ⁿ agrees with the Bjorken Sum Rule prediction when 3rd. order I QCD corrections are included. The methods used to evaluate the structure fimctions at a common Q² are being filrther investigated

[en] Recent experiments have begun to probe the detailed spin and flavor structure of hadrons. The status of the g₁ structure function and its implications for the polarized strange quark sea will be discussed, as well as what we hope to learn about hadronic structure from spin dependent measurements that will be carried out over the next few years

[en] Polarized or unpolarized γ's in the energy range of a few MeV to many GeV are produced using one of two methods: by Bremstrahlung radiation emitted when electrons strike a target or by Compton scattering of low energy photons from extremely relativistic electrons. Both methods can produce either linearly or circularly polarized γ's but other characteristics of the γ beams produced by the two methods differ substantially. The characteristics of beams produced by each method, the parameters of facilities using each method, and the expected capabilities of newly proposed facilities are discussed