The Design and Construction of a Green Laser and Fabry-Perot Cavity System for Jefferson Lab\u27s Hall A Compton Polarimeter

A high finesse Fabry-Perot cavity with a frequency doubled green laser (CW, 532 nm) have been built and installed in Hall A of Jefferson Lab for high precision Compton polarimetry project in spring of 2010. It provides a high intensity circularly polarized photon target for measuring the polarization of electron beam with energies from 1.0 GeV to 11.0 GeV in a nondestructive manner. The IR beam (CW, 1064 nm) from a Ytterbium doped fiber laser amplifier seeded by a Nd:YAG narrow linewidth NPRO laser is frequency doubled in by a single-pass Periodically Poled Lithium Niobate (PPMgLN) crystal. The maximum achieved green power at 5 W IR pump power was 1.74 W with a total conversion efficiency of 34.8%. The frequency locking of this green light to the cavity resonance frequency is achieved by giving a feedback to Nd:YAG crystal via laser piezoelectric (PZT) actuator by Pound-Drever-Hall (PDH) technique. The data shows the maximum amplification gain of our cavity is about 4,000 with a corresponding maximum intra-cavity power of 3.7 kW. The polarization transfer function has been measured in order to determine the intra-cavity laser polarization within the measurement uncertainty of 0.7%. The PREx experiment at JLab, used this system for the first time and achieved 1.0% precision in electron beam polarization measurement at 1.0 GeV

Precision measurements of A1N in the deep inelastic regime

We have performed precision measurements of the double-spin virtual-photon asymmetry A1A1 on the neutron in the deep inelastic scattering regime, using an open-geometry, large-acceptance spectrometer and a longitudinally and transversely polarized 3He target. Our data cover a wide kinematic range 0.277≤x≤0.5480.277≤x≤0.548 at an average Q2Q2 value of 3.078 (GeV/c)2, doubling the available high-precision neutron data in this x range. We have combined our results with world data on proton targets to make a leading-order extraction of the ratio of polarized-to-unpolarized parton distribution functions for up quarks and for down quarks in the same kinematic range. Our data are consistent with a previous observation of anA1n zero crossing near x=0.5x=0.5. We find no evidence of a transition to a positive slope in(Δd+Δd¯)/(d+d¯) up to x=0.548x=0.548

Media 4: Angle-multiplexed spatial-spectral interferometry for simultaneous measurement of spectral phase and polarization state

Originally published in Optics Express on 04 November 2013 (oe-21-22-26896

Media 2: Angle-multiplexed spatial-spectral interferometry for simultaneous measurement of spectral phase and polarization state

Originally published in Optics Express on 04 November 2013 (oe-21-22-26896

Media 3: Angle-multiplexed spatial-spectral interferometry for simultaneous measurement of spectral phase and polarization state

Originally published in Optics Express on 04 November 2013 (oe-21-22-26896

Media 1: Angle-multiplexed spatial-spectral interferometry for simultaneous measurement of spectral phase and polarization state

Originally published in Optics Express on 04 November 2013 (oe-21-22-26896

High efficiency laser-assisted H^{-} charge exchange for microsecond duration beams

Laser-assisted stripping is a novel approach to H^{-} charge exchange that overcomes long-standing limitations associated with the traditional, foil-based method of producing high-intensity, time-structured beams of protons. This paper reports on the first successful demonstration of the laser stripping technique for microsecond duration beams. The experiment represents a factor of 1000 increase in the stripped pulse duration compared with the previous proof-of-principle demonstration. The central theme of the experiment is the implementation of methods to reduce the required average laser power such that high efficiency stripping can be accomplished for microsecond duration beams using conventional laser technology. The experiment was performed on the Spallation Neutron Source 1 GeV H^{-} beam using a 1 MW peak power UV laser and resulted in ∼95% stripping efficiency