[en] Polarized electron beams are used widely for DIS, parity violation, and other experiments. I discuss the methods and instrumentation used to measure the electron beam polarization, as well as the prospects for the future facilities. A number of recent achievements and projects are discussed. More details on the subject can be found in a 1998's review

[en] A new generation of precise Parity-Violating experiments will require a sub-percent accuracy of electron beam polarimetry. Compton polarimetry can provide such accuracy at high energies, but at a few hundred MeV the small analyzing power limits the sensitivity. Mo/ller polarimetry provides a high analyzing power independent on the beam energy, but is limited by the properties of the polarized targets commonly used. Options for precision polarimetry at 300 MeV will be discussed, in particular a proposal to use ultra-cold atomic hydrogen traps to provide a 100%-polarized electron target for Mo/ller polarimetry

[en] Published in summary form only

[en] A novel proposal of using polarized atomic hydrogen gas, stored in an ultra-cold magnetic trap, as the target for electron beam polarimetry based on Moeller scattering is discussed. Such a target of practically 100% polarized electrons could provide a superb systematic accuracy of about 0.5% for beam polarization measurements. Feasibility studies for the CEBAF electron beam have been performed. (orig.)

[en] The 12 GeV upgrade at Jefferson Lab will open a new era of precision measurement of the Transverse Momentum Dependent parton distribution functions (TMDs) through the Semi-Inclusive Deep-Inelastic Scattering (SIDIS). In this talk, we discussed the projected results on measurements of TMDs using a newly proposed large acceptance solenoid detector together with the standard Hall A polarized ³He target. The high luminosity and the large acceptance detector will allow for a precise 3-D (x, z and P_T) mapping of azimuthal asymmetries. Furthermore, the full 2π azimuthal angular coverage for the solenoid detector is essential to control the relevant systematic uncertainties in extracting the azimuthal asymmetries. With a 40 cm long transversely polarized ³He target, a total of 60 days of beam time at a beam current of 15 μA, we can determine tensor charge of d quark to 10% in a model independent way. The extracted Sivers asymmetry will provide important information to understand the correlation between the quark orbital angular momentum and the nucleon spin.

[en] We propose a measurement of the Deep Virtual Compton Scattering process (DVCS) ep → epγ in Hall A at Jefferson Lab with a 6 GeV beam. We are able to explore the onset of Q² scaling, by measuring a beam helicity asymmetry for Q² ranging from 1.5 to 2.5 GeV² at x_B∼0.35. At this kinematics, the asymmetry is dominated by the DVCS - Bethe-Heitler (BH) interference, which is proportional to the imaginary part of the DVCS amplitude amplified by the full magnitude of the BH amplitude. The imaginary part of the DVCS amplitude is expected to scale early. Indeed, the imaginary part of the forward Compton amplitude measured in deep inelastic scattering (via the optical theorem) scales at Q² as low as 1 GeV². If the scaling regime is reached, we will make an 8% measurement of the skewed parton distributions (SPD) contributing to the DVCS amplitude. Also, this experiment allows us to separately estimate the size of the higher-twist effects, since they are only suppressed by an additional factor 1/Q compared to the leading-twist term, and have a different angular dependence. We use a polarized electron beam and detect the scattered electron in the HRSe, the real photon in an electromagnetic calorimeter (under construction) and the recoil proton in a shielded scintillator array (to be constructed). This allows as to determine the difference in cross-sections for electrons of opposite helicities. This observable is directly linked to the SPD's. We estimate that 25 days of beam (600 hours) are needed to achieve this goal. (authors)

[en] An experiment is proposed to measure the cross sections for Real Compton Scattering from the proton in the energy range 3-6 GeV and over a wide angular range, and to measure the longitudinal and transverse components of the polarization transfer to the recoil proton at a single kinematic point. Together, these measurements will test models of the reaction mechanism and determine new structure functions of the proton that are related to the same non-forward parton densities that determine the elastic electron scattering form factors and the parton densities. The experiment utilizes an untagged Bremsstrahlung photon beam and the standard Hall A cryogenic targets. The scattered photon is detected in a photon spectrometer, currently under construction. The coincident recoil proton is detected in one of the Hall A magnetic spectrometers and its polarization components are measured in the existing Focal Plane Polarimeter. This proposal extends and supersedes E97 - 108 which was approved by PAC13. (author)

[en] Moeller polarimeter for measuring polarisation of electron beam with energy up to 6 GeV was elaborated in accordance with Memorandum between KhFTI (Ukraine) and Jefferson Laboratory (USA) and put into operation at the beam line TJNAF of KhFTI. It is based on measurements of Moeller scattering of polarised beam electrons on polarised target electrons. Parameters of Polarimeter and measuring method are described

[en] The results of experiments on studying spallation and the ejection of particles from the surfaces of copper and lead samples are presented. A laser interferometry method is used to detect the particle cloud velocity and the multiple spallation parameters. Angular detectors are used to detect the depth profile of the particle cloud velocity dispersion and the structure of metal spallation.

[en] This paper was published online on 20 May 2005 without several of the authors' corrections incorporated. Equation (13) has been replaced. The captions of Figs. 16-18 have also been replaced. Typographical errors on pages 4, 6, 14, 15, 18, 19, 22, and 24 have all been corrected. The paper has been corrected as of 8 June 2005. The text is correct in the printed version of the journal