HD gas analysis with gas chromatography and quadrupole mass spectrometer Ohta, T.; Bouchigny, S.; Didelez, J.-P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2011, Letnik:
640, Številka:
1
Journal Article
Recenzirano
Odprti dostop
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 a 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
2D
+ 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 a gas chromatograph and the QMS. Helium or neon gas was used as a carrier gas for the gas chromatograph 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 chromatograph 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
2D
+ 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 ortho-H
2 and D
2 with good
S
/
N
ratios.
The complete polarization of DT fuel would increase the fusion reactivity by 50% in magnetic as well as in inertial confinements. The persistence of polarization in a fusion process could be tested, ...using a terawatt laser hitting a polarized HD target. The polarized deuterons heated in the plasma induced by the laser can fuse producing a super(3)He and a neutron in the final state. The angular distribution of the emitted neutrons and the change in the corresponding total Cross Section (CS) can sign the polarization persistence. The polarization of solid H sub(2), D sub(2) or T sub(2) Hydrogen isotopes is very difficult. However, it has been possible to polarizeHD, a hetero-molecular form of Hydrogen, by static polarization, at very low temperature and very high field. The radioactivity of DT molecules forbids there high polarization by the static method, therefore one has to develop the Dynamic Nuclear Polarization (DNP) by RF transitions. The DNP of HD has been investigated in the past. The magnetic properties of HD and DT molecules are very similar, it is therefore expected that any polarization result obtained with HD could be extrapolated to DT.
Distillation of hydrogen isotopes for polarized HD targets Ohta, T.; Bouchigny, S.; Didelez, J.-P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2012, Letnik:
664, Številka:
1
Journal Article
Recenzirano
Odprti dostop
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-H
2 (
∼
0.01
%
) in the ...HD gas plays an important role in efficiently polarizing the HD target. Since there are 1–5% impurities of H
2 and D
2 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-H
2 to the purified HD gas.
The photoproduction of the omega meson has been studied at GRAAL from threshold up to a photon energy of 1.5 GeV. The differential cross sections and beam asymmetries have been measured precisely at ...all angles. The total cross section is also obtained. Systematic enhancements of the differential cross section at large angles and nonzero beam asymmetries at intermediate angles provide clear evidence for s- and u-channel resonant processes. The data are compared to the results of hadron and quark models.
We report on the studies of Transverse-Momentum-Dependent distributions (TMDs) at a future fixed-target experiment –AFTER@LHC– using the
p
+
or Pb ion LHC beams, which would be the most energetic ...fixed-target experiment ever performed. AFTER@LHC opens new domains of particle and nuclear physics by complementing collider-mode experiments, in particular those of RHIC and the EIC projects. Both with an extracted beam by a bent crystal or with an internal gas target, the luminosity achieved by AFTER@LHC surpasses that of RHIC by up to 3 orders of magnitude. With an unpolarised target, it allows for measurements of TMDs such as the Boer-Mulders quark distributions and the distribution of unpolarised and linearly polarised gluons in unpolarised protons. Using polarised targets, one can access the quark and gluon Sivers TMDs through single transverse-spin asymmetries in Drell-Yan and quarkonium production. In terms of kinematics, the fixed-target mode combined with a detector covering
η
lab
∈
1
,
5
allows one to measure these asymmetries at large
x
↑
in the polarised nucleon.
Beam asymmetries and hyperon recoil polarizations for the reactions $\gamma p \to K^{+}\Lambda$ and $\gamma p \to K^{+}\Sigma^{0}$ have been measured from the threshold production to 1500 MeV with ...the GRAAL facility located at the ESRF in Grenoble. These results complement the database for the beam asymmetry, covering for the first time the production threshold region. Recent theoretical analyses are presented for which the beam asymmetry data bring interesting new information and allow to better determine some resonance parameters. Most importantly, these results strengthen the need of a new D$_{13}$ state around 1900 MeV.
We outline the opportunities for ultra-relativistic heavy–ion physics which are offered by a next generation and multi-purpose fixed-target experiment exploiting the proton and ion LHC beams ...extracted by a bent crystal.
We present new Σ beam asymmetry data for η meson photoproduction on the proton, using a novel tagged, laser backscattered, linearly polarized photon beam up to 1.1 GeV. The data show large, positive ...asymmetries, at all incident photon energies. In addition to the S11(1535) and D13(1520) resonances necessary to reproduce the cross sections, P13(1720) and D15(1675) “four stars” resonances contribute to the Σ observable, but cannot reproduce the strong forward asymmetries measured at energies higher than 900 MeV. (APS)
The double pi(0) photoproduction off the proton has been measured in the beam energy range of 0.65-1.5 GeV. The total and differential cross sections and the Sigma beam asymmetry were extracted. The ...total cross section measured for the first time in the third resonance region of the nucleon shows a prominent peak. The interpretation of these results by two independent theoretical models infers mostly the selective excitation of P11- and D13-nucleon resonances.
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