Distillation of HD gas and measurement of spin–lattice relaxation times Bouchigny, S.; Didelez, J.-P.; Dubois, F. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2009, Letnik:
607, Številka:
2
Journal Article
Recenzirano
The polarization (static or dynamic) of
HD material requires very pure
HD samples, with
H
2
and
D
2
impurities concentrations smaller than 0.1%. A new distillation apparatus equipped with a mass ...spectrometer has been built. It allows reaching such a level of purity and also measurement of the
H
2
and
D
2
residual concentrations down to 0.05%. The NMR spin–lattice relaxation times
T
1
H
and
T
1
D
have also been measured. The apparatus is described as well as the distillation method.
T
1
H
and
T
1
D
data as a function of
H
2
and
D
2
concentrations are given, at 0.85
T and 1.8
K.
The double polarization (beam-recoil) observables Ox and Oz have been measured for the reaction γp → K+Λ from threshold production to E ∼ 1500MeV. The data were obtained with the linearly polarized ...beam of the GRAAL facility. Values for the target asymmetry T could also be extracted despite the use of an unpolarized target. Analyses of our results by two isobar models tend to confirm the necessity to include new or poorly known resonances in the 1900MeV mass region.
Beam asymmetry and differential cross section for the reaction gamma+p->eta+p were measured from production threshold to 1500 MeV photon laboratory energy. The two dominant neutral decay modes of the ...eta meson, eta->2g and eta->3pi0, were analyzed. The full set of measurements is in good agreement with previously published results. Our data were compared with three models. They all fit satisfactorily the results but their respective resonance contributions are quite different. The possible photoexcitation of a narrow state N(1670) was investigated and no evidence was found.
The $\Sigma$ beam asymmetry in $\eta^{\prime}$ photoproduction off the proton was measured at the GrAAL polarized photon beam with incoming photon energies of 1.461 and 1.480 GeV. For both energies ...the asymmetry as a function of the meson emission angle shows a clear structure, more pronounced at the lowest one, with a change of sign around 90$^o$. The results are compared to the existing theories that fail to account for the data.
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.
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 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.
PDF
