Development of portable NMR polarimeter system for polarized HD target

Ohta, Takao; Fujiwara, M̄.; Fukuda, Ken; Kohri, H.; Kunimatsu, T.; Morisaki, C.; Ono, Satoshi; Tanaka, M.; Ueda, Kazuyuki; Uraki, M.; Utsuro, Masahiko; Wang, S.Y.; Yosoi, M.

doi:10.1016/j.nima.2010.12.235

Cited by 12 publications

(1 citation statement)

References 26 publications

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“…In order to monitor the relative polarization of 129 Xe inside the optical pumping cell, we designed and constructed an ultra-low field NMR spectrometer similar to those described in previous work[26–31]. The spectrometer is custom-programmed in LabVIEW and run via a National Instruments multifunction data acquisition (DAQ) card (model PCI-6110).…”

Section: Methodsmentioning

confidence: 99%

Depolarization of nuclear spin polarized 129 Xe gas by dark rubidium during spin-exchange optical pumping

Antonacci

Burant

Wagner

et al. 2017

Journal of Magnetic Resonance

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Continuous-flow spin-exchange optical pumping (SEOP) continues to serve as the most widespread method of polarizing 129Xe for magnetic resonance experiments. Unfortunately, continuous-flow SEOP still suffers from as-yet unidentified inefficiencies that prevent the production of large volumes of xenon with a nuclear spin polarization close to theoretically calculated values. In this work we use a combination of ultra-low field nuclear magnetic resonance spectroscopy and atomic absorption spectroscopy (AAS) measurements to study the effects of dark Rb vapor on hyperpolarized 129Xe in situ during continuous-flow SEOP. We find that dark Rb vapor in the optical cell outlet has negligible impact on the final 129Xe polarization at typical experimental conditions, but can become significant at higher oven temperatures and lower flow rates. Additionally, in the AAS spectra we also look for a signature of paramagnetic Rb clusters, previously identified as a source of xenon depolarization and a cause for SEOP inefficiency, for which we are able to set an upper limit of 8.3×1015 Rb dimers per cm3.

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Section: Methodsmentioning

confidence: 99%

Depolarization of nuclear spin polarized 129 Xe gas by dark rubidium during spin-exchange optical pumping

Antonacci

Burant

Wagner

et al. 2017

Journal of Magnetic Resonance

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HD gas analysis with gas chromatography and quadrupole mass spectrometer

Ohta

Bouchigny

Didélez

et al. 2011

Nuclear Instruments and Methods in Physics Research Section A:

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A gas analyzer system has been developed to analyze Hydrogen-Deuteride (HD) gas for producing frozen-spin polarized HD targets, which are used for hadron photoproduction experiments at SPring-8. Small amounts of ortho-H 2 and para-D 2 gas mixtures (∼0.01%) in the purified HD gas are a key to realize a frozen-spin polarized target. However, there was an intrinsic difficulty to measure these small mixtures in the HD gas with a quadrupole mass spectrometer (QMS) because D + and [H 2 D] + produced from the ionization of HD molecules were misidentified as H 2 and D 2 molecules, respectively, and became backgrounds for the measurement of the H 2 and D 2 concentrations. In addition, the ortho-H 2 and para-D 2 are not distinguished from the para-H 2 and ortho-D 2 , respectively, with the QMS. In order to obtain reliable concentrations of these gas mixtures in the HD gas, we produced a new gas analyzer system combining two independent measurements with the gas chromatography and the QMS. Helium or neon gas was used as a carrier gas for the gas chromatography which was cooled at ∼110 K. The para-H 2 , ortho-H 2 , HD, and D 2 are separated using the retention time of the gas chromatography and the mass/charge ratio. Although the para-D 2 is not separated from the ortho-D 2 , the total amount of the D 2 is measured without the [H 2 D] + background. The ortho-H 2 concentration is also measured separately from the D + background. It is found that the new gas analyzer system can measure small concentrations of ∼0.01% for the otho-H 2 and D 2 with good S/N ratios.

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Distillation of hydrogen isotopes for polarized HD targets

Ohta

Bouchigny

Didélez

et al. 2012

Nuclear Instruments and Methods in Physics Research Section A:

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We have developed a new cryogenic distillation system to purify Hydrogen-Deuteride (HD) gas for polarized HD targets in LEPS experiments at SPring-8. A small amount of ortho-H2 (∼0.01%) in the HD gas plays an important role in efficiently polarizing the HD target. Since there are 1-5% impurities of H2 and D2 in commercially available HD gases, it is necessary to purify the HD gas up to ∼99.99%. The distillation system is equipped with a cryogenic distillation unit filled with many small stainless steel cells called "Heli-pack". The distillation unit consists of a condenser part, a rectification part, and a reboiler part. The unit is kept at the temperature of 17-21 K. The Heli-pack has a large surface area that makes a good contact between gases and liquids. An amount of 5.2 mol of commercial HD gas is fed into the distillation unit. Three trials were carried out to purify the HD gas by changing temperatures (17.5 K and 20.5 K) and gas extraction speeds (1.3 ml/min and 5.2 ml/min). The extracted gas was analyzed using a gas analyzer system combining a quadrupole mass spectrometer with a gas chromatograph. One mol of HD gas with a purity better than 99.99% has been successfully obtained for the first time. The effective NTP (Number of Theoretical Plates), which is an indication of the distillation performances, is obtained to be 37.2±0.6. This value is in good agreement with a designed value of 37.9. The HD target is expected to be efficiently polarized under a well-controlled condition by adding an optimal amount of ortho-H2 to the purified HD gas

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Development of portable NMR polarimeter system for polarized HD target

Cited by 12 publications

References 26 publications

Depolarization of nuclear spin polarized 129 Xe gas by dark rubidium during spin-exchange optical pumping

Depolarization of nuclear spin polarized 129 Xe gas by dark rubidium during spin-exchange optical pumping

HD gas analysis with gas chromatography and quadrupole mass spectrometer

Distillation of hydrogen isotopes for polarized HD targets

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