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Jefferson Lab is interested in the production of positrons for nuclear physics applications but also has the capability of producing low energy positrons that could be used for positron annihilation studies. Using the LERF accelerator at the Thomas Jefferson National Accelerator Facility, it is possible to produce a high brightness source of very low-energy positrons. The accelerator requirements are well within the capabilities of the installed hardware. For these experiments, we only need run at up to 120 MeV. A challenge is the production of the positrons. The gamma converter must be able to absorb the 50 kW of beam power that the linac delivers. At this low an energy, the converter, though challenging, is feasible. The transport of the low energy positrons from the production target to the next stage, where the energy is reduced even further, must have a very large acceptance to be able to efficiently transport the flux of positrons from the positron production target to the moderator. We propose to accomplish such a transport by means of a guiding solenoidal field with a novel endcap design. Finally, it is in principle possible to produce a spin polarized beam by filtering the positrons at low energy. The layout of the proposed device will be described in this presentation. [ABSTRACT FROM AUTHOR]

Though there are many applications of low energy positrons, many experiments are source limited. Using the LERF accelerator at the Thomas Jefferson National Accelerator Facility, it is possible to build a high brightness source of very low-energy positrons. The accelerator requirements are well within the capabilities of the installed hardware. The accelerator can produce 120 kW of beam with a beam energy of up to 170 MeV. For these experiments, we only need run at up to 120 MeV. The gamma-to-positron converter must be able to absorb 20% of the beam power that the linac delivers. At this low an energy the converter, though challenging, is possible. The transport of the low energy positrons from the production target to the next stage, where the energy is reduced even further, must have a very large acceptance to be able to efficiently transport the flux of positrons from the positron production target to the moderator. We propose to accomplish such a transport by means of a guiding solenoidal field with a novel endcap design. In this presentation, we will present the proposed schemes necessary to realize such a high brightness positron source. [ABSTRACT FROM AUTHOR]

Concepts of high precision studies of the one-way speed of light anisotropy are discussed. The high energy particle beam allows measurement of a one-way speed of light anisotropy (SOLA) via analysis of the beam momentum variation with sidereal phase without the use of synchronized clocks. High precision beam position monitors could provide accurate monitoring of the beam orbit and determination of the particle beam momentum with relative accuracy on the level of 10 -10, which corresponds to a limit on SOLA of 10-18 with existing storage rings. A few additional versions of the experiment are also presented. [ABSTRACT FROM AUTHOR]

The physics of Wide Angle Compton Scattering (WACS) from the proton was addressed in a pioneering experiment performed at Cornell in 1979. The process was analyzed in the pQCD framework. The general features of pQCD predictions were found in agreement with the experiment. However, detailed calculations got a cross section smaller by a factor of five-ten than from the experiment, for most models of nucleon distribution amplitudes. This raised a question of the origin of the scaling and the appropriate mechanism of WACS. Recently WACS attracted considerable attention because of its connection to the novel concept of skewed patton distributions. The progress of theory and expected soon an experiment will allow clarification of the mechanism of WACS process at s,-t,-u in the range of 5 -10 GeV². Experiment E99-114 will be done at photon energy up to 6 GeV and large angles (from 60 up to 130 degrees in cms). In comparison with the only existing previous measurement the counting rate in our experiment will be 300 times higher. Such gain in luminosity results from a combination of the 100% duty factor of CEBAF, high segmentation and resolution of the photon detector, and successful use of the mixed photon/electron beam. The dominant mechanism of WACS will be investigated through s and t dependence of the cross section and by using polarization transfer from photon to proton. Presently, we are studying the possibility to measure the effect of photon linear polarization. [ABSTRACT FROM AUTHOR]

Neutrons with energies E below the Fermi effective potential U[sub eff] ∼0.2 µeV are called ultracold neutrons (UCN), which are totally reflected from a surface of material and thus can be stored in a bottle. The UCN in a bottle are of a great advantage for highprecision measurements in fundamental physics with neutrons, where the UCN density ρ[sub UCN] takes the key role. We have proposed a new method for the production of UCN, which is based on the repeated application of a field-gradient force on a magnetic moment realized with a spatially alternating field and the correlated spin flips. To evaluate the feasibility and performance of the method, a computer simulation of neutron decelerating and transporting processes has been performed. The result indicates that the UCN density ρ[sub UCN] in a storage bottle in the present method reaches quite large values as ρ[sub UCN] ≈ 2.2xl0³ n/cm³ in a realistic condition. An experiment to test the principle and to explore the technical ingredients of the present method is being conducted using the UCN beam from the supermirror turbine at KUR. [ABSTRACT FROM AUTHOR]