HD gas purification for polarized HDice targets production at Jefferson Lab

Abstract

Frozen spin HD targets have been used in the study of photonuclear reactions at Brookhaven National Laboratory and, more recently, at Jefferson Lab. Commercially available gas contains H 2 and D 2 at levels much too high for target production. To obtain gas the required purity, low temperature distillation is employed. The relative concentrations of H 2 and D 2 in the purified HD gas are measured with a residual gas analyzer, gas chromatography, and Raman scattering. The distillation process is described and the measurement techniques and the results are summarized.

Polarization Observables from two-pion and ρ meson photoproduction on polarized HD target at JLab

“…The optimal concentrations to achieve a frozen-spin target must be two order of magnitudes smaller. For this aim, a distillation procedure has been developed at the James Madison University (JMU) [49]. The purification procedure is based on the fact that at low temperatures the vapor pressures of H 2 , D 2 and HD are different.…”

“…This sensitivity, although sufficient to verify that the distillery is working correctly, is not high enough to measure contaminants concentrations at the level of 10 −4 , necessary for producing polarized "frozen spin" targets. An example of a typical chromatogram is shown in Figure 3.5, where the comparison between the relative concentrations of H 2 and D 2 impurities in the raw gas and in the distilled gas is shown [49]. A valid approach to quantify with higher sensitivity the relative content of hydrogen isotopes is the Raman spectroscopy, which exploits the inelastic scattering of light from molecular hydrogen.…”

First Measurement of the E Double-polarization Observable for the γη to Κ⁺Σ^- with CLAS & a New Forward Tagger Hodoscope for CLAS12

“…This can however be purified further using a procedure developed by James Madison University (JMU)[94], giving impurities as low as 10 −4 .…”