Recently, we have proposed an experiment to test the persistence of the polarization in a fusion process (D+D→3He+n), using a powerful laser hitting a polarized HD target. The purpose of the present ...contribution is to examine in more detail the experimental constraints, to move from a principle proposal to a doable experiment. Some of the difficulties are as follows: Production of a windowless cryogenic HD target and target cryostat vacuum breakdown, identification of thermal fusion or accelerated deuterons, inducing nuclear reactions, and finally, a clear signature of the polarization persistence of the fused deuterons must be found. Those points will be reviewed and discussed in the scope of the new results presented at this conference.
The nuclear fusion cross-section is modified when the spins of the interacting nuclei are polarized. In the case of deuterium-tritium it has been theoretically predicted that the nuclear fusion ...cross-section could be increased by a factor δ = 1.5 if all the nuclei were polarized. In inertial confinement fusion this would result in a modification of the required ignition conditions. Using numerical simulations it is found that the required hot-spot temperature and areal density can both be reduced by about 15% for a fully polarized nuclear fuel. Moreover, numerical simulations of a directly driven capsule show that the required laser power and energy to achieve a high gain scale as δ−0.6 and δ−0.4 respectively, while the maximum achievable energy gain scales as δ0.9.
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.
We propose an experiment to test the persistence of the polarization in a fusion process, using a terawatt laser hitting a polarized high density (HD) target. The polarized protons and deuterons ...heated in the plasma induced by the laser have a significant probability to fuse producing a 3He and a γ-ray or a neutron in the final state. The angular distribution of the radiated γ-rays and the change in the corresponding total cross-section are related to the polarization persistence, but the resulting signal turns out to be weak. By comparison, the neutrons are produced hadronically with a larger cross-section and it is much easier to detect them. A significant reduction of the cross-section by parallel polarization of the deuterons as well as a structured angular distribution of the emitted neutrons is reliably predicted by the theory. Therefore, it is expected that the corresponding signal on the neutron counting rate could be seen experimentally. Magnetic fields, relaxation times and possibilities of local investigations are discussed.
Inertial confinement fusion fast ignition at very high relativistic electron beam energy is systematically explored through a possible combination of various stopping mechanisms including strong ...Langmuir turbulence, elastic, and inelastic electron interactions with target particles. A specific attention is given to final state interaction through catalysis by negative pion.
The differential cross section for the reaction p(γ,ηp) has been measured from threshold to 1100 MeV photon laboratory energy. For the first time, the region of the S11(1535) resonance is fully ...covered in a photoproduction experiment and will allow a precise extraction of its parameters at the photon point. These high precision data together with the already measured beam asymmetry data will provide stringent constraints on the extraction of new couplings of baryon resonances to the η meson.
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.
We report on the opportunities for spin physics and Transverse-Momentum Dependent distribution (TMD) studies at a future multi-purpose fixed-target experiment using the proton or lead ion LHC beams ...extracted by a bent crystal. The LHC multi-TeV beams allow for the most energetic fixed-target experiments ever performed, opening new domains of particle and nuclear physics and complementing that of collider physics, in particular that of RHIC and the EIC projects. The luminosity achievable with AFTER@LHC using typical targets would surpass that of RHIC by more that 3 orders of magnitude in a similar energy region. In unpolarised proton-proton collisions, AFTER@LHC allows for measurements of TMDs such as the Boer-Mulders quark distributions, the distribution of unpolarised and linearly polarised gluons in unpolarised protons. Using the polarisation of hydrogen and nuclear targets, one can measure transverse single-spin asymmetries of quark and gluon sensitive probes, such as, respectively, Drell-Yan pair and quarkonium production. The fixed-target mode has the advantage to allow for measurements in the target-rapidity region, namely at large x↑ in the polarised nucleon. Overall, this allows for an ambitious spin program which we outline here.
PDF
