Vector-polarized Deuterons Research Articles

Deuteron frozen-spin- polarized target for nd experiments at the VdG accelerator of Charles University

A frozen-spin- polarized deuteron target cooled by the 3He/ 4He dilution refrigerator is described. Fully deuterated 1,2-propanediol was used as a target material. Deuteron vector polarization about 40% was obtained for the target in the shape of a cylinder of 2-cm diameter and 6-cm length. The target is intended for a study of 3N interactions at the polarized neutron beam generated by the Van de Graaff accelerator at the Charles University in Prague.

Relativistically invariant analysis of polarization effects in exclusive deuteron electrodisintegration process

A general formalism for the calculation of the differential cross-section and polarization observables, for the process of deuteron electrodisintegration, is developed in the framework of relativistic impulse approximation. A detailed analysis of the general structure of the differential cross-section and polarization observables for the e − + d → e − + n + p reaction is derived, using the formalism of the structure functions. The obtained expressions have a general nature and they hold in the one-photon-exchange mechanism, assuming P-invariance of the hadron electromagnetic interaction. The model of relativistic impulse approximation is introduced and the final state interaction is taken into account by means of the unitarization of the helicity amplitudes. A detailed description of the unitarization procedure is also presented. Using different parametrizations of the deuteron wave functions, the following polarization observables are calculated in the kinematical region of quasi-elastic deuteron electrodisintegration: the asymmetry for the scattering of longitudinally polarized electrons on a polarized deuteron target, the proton and neutron polarizations (for longitudinally polarized electron beam or vector-polarized deuteron target). The sensitivity to the neutron electric form factor is also thoroughly investigated. The predictions of the model are compared with the results of recent polarization measurements and a good agreement with the existing experimental data has been obtained.

Progress in the polarization of HD

The static polarization of HD samples has been achieved using “brute force”, for HD samples purified by double distillation. Proton polarization in excess of 60% and deuteron vector polarization higher than 14% have been reached. It has been demonstrated that the ageing technique allows to get relaxation times at 1.5 K and 1 T larger than a week. It is advocated that the conventional dynamic polarization of HD should be feasible for the proton and the deuteron contained in the HD molecule. This would create the possibility of polarizing DT molecules, increasing their reactivity when used as fuel in HIIF processes.

Possible method for the determination of the neutron electric form factor based on a measurement of asymmetries for the processH⃗2(e⃗,e′n)p

We generalize the recoil polarization method for the determination of the proton form factor to the case of the disintegration of vector polarized deuterons by longitudinally polarized electrons, $\vec d(\vec e, e'n)p$. We suggest to measure for this reaction, in the kinematics of quasi-elastic $en$-scattering, the ratio $R_{xz}=A_x/A_z$ of the asymmetries induced by the $x$- and $z$-components of the deuteron vector polarization. In the framework of the relativistic impulse approximation the ratio $R_{xz}$ is sensitive to $G_{En}$ in a wide interval of momentum transfer squared, whereas it depends weakly on the details of the $np$-interaction and on the choice of the deuteron wave function. Moreover, in the range $0.5\le Q^2\le$1.5 GeV$^2$, the ratio $R_{xz}$ shows a smooth dependence on $Q^2$, making the analysis simpler.

Static and dynamic polarization of HD

The static polarization of HD samples has been achieved using “brute force”, for HD samples purified by double distillation. Proton polarization in excess of 60% and deuteron vector polarization higher than 14% have been reached. It has been demonstrated that the ageing technique allows to get relaxation times at 1.5 K and 1 T larger than a week. It is advocated that the conventional dynamic polarization of HD should be feasible for the proton and the deuteron contained in the HD molecule. This would simplify considerably the machinery presently necessary to perform nuclear physics experiments with HD targets polarized by the static method.

Absolute calibration of a double-cell polarized 3He gas target

We introduce a new method for determining the polarization of the atoms in a polarized 3He target. The new method makes use of special properties of the reaction 3He(d,p) 4He. We demonstrate that for protons produced by this reaction at θ=0°, the polarization observables T 20 and C z, z are related according to 2 T 20+3C z,z=−2 . Using this result, we have made an absolute measurement of the target polarization in the Wisconsin double-cell polarized 3He target. The calibration was carried out by observing the 3He(d,p) 4He reaction with vector- and tensor-polarized deuterons of known polarization. The analyzing power T 20(0°) at energy E d=2.1 MeV was first measured with the result T 20(0°)=−0.530±0.012. The corresponding spin correlation coefficient is C z, z (0°)=−0.417±0.006. The target polarization, P t, was then determined by measuring the 0° proton asymmetry with vector-polarized deuterons. During the measurement, the relative target polarization was monitored by measuring the circular polarization P ⊙ of the 668 nm emission light from the optical pumping cell. From the measured target polarization we obtain a calibration constant K= P t/ P ⊙=11.57±0.43. This result is in good agreement with the calibrations based on other techniques.

Dependence of deuteron vector-polarization on ion source transition configurations

The deuteron vector polarization of extracted SATURNE II beam as a function of different ion source configurations was studied. In all measurements deuterons were considered as weakly bound protons and neutrons and quasielastic pp→pp+n reaction with the n as a spectator was measured. The Left–Right instrumental asymmetry of the beam polarimeter arms was determined using an unpolarized beam from the ion source Amalthée. The obtained correction factor was applied to asymmetries measured with the beam from the polarized ion source Hyperion in the vector-polarization states. The measurements were carried out at the deuteron beam kinetic energy of 0.80 GeV/nucleon, where the pp-elastic scattering analyzing power is near its maximum. The results showed that in the nominal conditions of the ion source the two so-called ‘unpolarized states’ were differently polarized, whereas the absolute values of the beam polarizations in the so-called ‘polarized states’ were approximately equal and opposite within errors. It was confirmed that the hexapole lens of the ion source produced beam polarization in the absence of any transition. A decrease of the hexapole current provides an extrema for the beam polarizations in the two ‘unpolarized’ states at different current values and slightly violates the equilibrium of polarizations for the ion source polarized states.

Transverse polarization transfer in the2H(d→,n→)3Hereaction atθ=0°

The transverse polarization transfer coefficient ${K}_{y}^{{y}^{\ensuremath{'}}}$ has been measured for the ${}^{2}\mathrm{H}(\stackrel{\ensuremath{\rightarrow}}{d},\stackrel{\ensuremath{\rightarrow}}{n}{)}^{3}\mathrm{He}$ reaction at 0\ifmmode^\circ\else\textdegree\fi{} for deuteron energies around 13 MeV, using a purely vector-polarized deuteron beam. At $0.666\ifmmode\pm\else\textpm\fi{}0.013,$ ${K}_{y}^{{y}^{\ensuremath{'}}}(0\ifmmode^\circ\else\textdegree\fi{})$ was found to be significantly larger than the values used frequently in the past to deduce the neutron polarization from the polarization of the deuteron beam.

The deuteron D-state probability

A method of direct determination of the deuteron D-state probability from the experiment, based on the d ↑ p → ppn reaction analyzis is suggested. Using the known results on the vector analyzing power in elastic NN-scattering, the values of the overall nucleon polarization and the deuteron vector polarization have been obtained. The probability of the deuteron D-state is estimated to be w D = 0.078 ± 0.046.

Breakup of 3He with 59.6 MeV vector-polarized deuterons at dp quasifree-scattering conditions

Abstract The 3 He breakup reaction has been studied with 59.6 MeV vector-polarized deuterons at dp quasifree-scattering (QFS) conditions. In the coincidence energy spectra, large bumps corresponding to the QFS were observed. The calculation in the simple plane-wave impulse approximation (PWIA) qualitatively reproduces the energy spectra, but for the absolute cross sections, the ratio of the experimental values to the calculated values in the PWIA is about 0.27. As for the analyzing powers, the experimental values are greatly reduced as compared with the dp elastic-scattering data. The multiple-scattering effect has been investigated by a calculation taking account of the effects of double-scattering terms on the cross sections and the analyzing powers.

Single-particle strengths measured with 48Ca( [formula omitted], p) 49Ca reaction at 56 MeV

Single-particle states in 49Ca have been investigated through the 48Ca( d , p) 49Ca reaction initiated by vector-polarized deuterons of E d = 56 MeV. Thirty-six levels were observed up to 8 MeV excitations. Transferred l, j values were deduced for these levels by measured angular distributions of cross section and analyzing power. We observed many additional states and corrected some previous j π assignments. The total values of spectroscopic factors C 2 S obtained with zero-range distorted-wave-Born-approximation (DWBA) calculations are almost unity for the shells 2p 3 2 , 2p 1 2 and 1f 5 2 , and no 1f 7 2 states are observed. It is confirmed that 48Ca has a good closed-shell structure, the feature of which is consistent with occupation probabilities predicted from an extended second RPA theory.

The distribution of proton-hole strengths in the (2s, 1d)-shell of 35Cl, 37Cl and 39Cl

A vector-polarized deuteron beam of 52 MeV was used to excite proton-hole states via the ( d , 3He) reaction on 36Ar, 38Ar and 40Ar. From the measured angular distributions of differential cross sections σ(θ) and analyzing powers iT 11( θ) we determined spins and parities J π = 1 2 + , 3 2 + 5 2 + and 1 2 − of a number of isolated levels in 36Cl, 37Cl and 39Cl and the complete 1d hole strength distribution in the continuum region. Relative proton occupancies, single-particle energies, the shape of the Fermi surface and spreading widths were obtained from a combined analysis with proton stripping reactions on even argon isotopes. The deduced Id spin-orbit splitting is found to be consistent with the recently observed dependence on main quantum number n and mass number A. The mass excess of 39Cl was determined to be (−29798 ± 2.8) keV compared to a value of (−29804 ± 19) keV as given in the mass tables.

Global properties of proton-hole strengths in mass 54 to 70 nuclei.

A vector-polarized deuteron beam of 52 MeV was used to excite proton hole states via the [sup 66]Zn([ital [rvec d]],[sup 3]He)[sup 65]Cu reaction. From the measured angular distributions of differential cross sections [sigma]([Theta]) and analyzing powers [ital iT][sub 11]([Theta]) we determined spins and parities of a number of individual low-lying levels in [sup 65]Cu and the hole strength distribution for [ital E][sub [ital x]][lt]19 MeV. Relative proton occupancies, single-particle energies, the shape of the Fermi surface, and spreading widths for various orbitals are presented as a result of combined analysis with proton stripping reactions on [sup 66]Zn. A corresponding analysis of previous proton pickup and stripping experiments on [sup 54,56,58]Fe, [sup 58,60,62,64]Ni, [sup 64]Zn, and [sup 70]Ge shows systematic [ital A]-dependent features of these integral properties of the spectra.

Complete spectroscopy of 90Y via the 89Y(n, γ) and 89Y( [formula omitted], p) reactions

The γ-ray spectrum emitted after thermal-neutron capture in 89Y was studied at the ILL high-flux reactor using a pair and Compton suppressed germanium detector. A total of 893 transitions were assigned to the decay of 90Y, 392 of which, representing more than 90% of the obtained flux, were placed in a level scheme of sixty states. The neutron binding energy of 90Y was determined as 6857.02 (17) keV. The reaction 89Y( d , p) was studied using a 22 MeV vector-polarized deuteron beam and the Munich Q3D spectrometer. Angular distributions of the vector-analyzing power and differential cross section for nearly all states up to 5 MeV excitation were taken and analyzed within the DWBA formalism. For some eighty states the transferred total and orbital angular momenta, spectroscopic factors and spins were deduced. The results of both measurements are compared and discussed in the scope of the statistical model, the shell model and the quasiparticle RPA-model.

The 60Ni( [formula omitted], 3He) 59Co reaction and the proton strengths distributions in even nickel isotopes

A vector-polarized deuteron beam of 52 MeV was used to excite proton hole states via the 60Ni( d , 3He) 59Co reaction. From the measured angular distributions of differential cross sections σ(Θ) and analyzing powers iT 11( Θ) we determined spins and parities of a number of individual low lying levels in 59Co and the complete hole strength distribution for E x < 19 MeV. The total (2s, 1d) and (1f, 2p) proton strengths are accounted for. Relative proton occupancies in various orbitals, single-particle energies, the shape of the Fermi surface and spreading widths are the results of a combined analysis with proton stripping reactions on 60Ni. A corresponding analysis of proton pick-up and stripping experiments on 58Ni, 62Ni and 64Ni shows systematic A-dependent features of these integral properties of the spectra.

The deuteron optical potential at low energies

The elastic scattering of vector-polarized deuterons has been measured near E d = 20 MeV on a variety of nuclei to investigate the effective deuteron-scattering potential at low energies. The analysis of the data has been performed within the conventional optical model as well as in the framework of the model-unrestricted Fourier-Bessel method. Whereas both methods result in scattering potentials which agree in their bulk properties, only the latter method leads to a statistically relevant description of the data with χ 2/ F≈1. The Fourier-Bessel potentials show features similar to those observed at 52 MeV: in contrast to what is expected from static folding, the real central potential has a small skin thickness comparable to that of nucleon potentials. In the absorptive potential the breakup contribution amounts to about 20%, in agreement with theoretical predictions. The empirical potentials are interpreted by single- and double-folding calculations.

Spin transfer, Kss in the pp → d π+ reaction

We have measured the vector polarization of deuterons at center-of-mass angles from 20° to 155° produced in the p p → dπ + reaction by a 507 MeV beam of sideways-polarized protons. Our results for sideways-to-sideways polarization transfer confirm the partial-wave amplitude fit of Bugg et al. Various model calculations are in qualitative agreement with our results. Our results are consistent with the corrected sideways-to-sideways spin transfer results obtained at 515 MeV by the University of Geneva group.

Break-up of deuteron by vector-polarized deuterons at 60 MeV

The reaction was studied experimentally at 60 MeV. Angular dependences of the cross sections and the analyzing powers for the quasi-free scattering resembled those for freed-p scattering. The experimental results were compared with a Born approximation calculation on the basis of the three-body scattering theory by Alt, Grassberger, and Sandhas.

Neutron electric form factor in inelastic scattering of polarized electrons by polarized deuterons

The asymmetries for the disintegration of vector-polarized deuterons by longitudinally polarized electrons are calculated. The sensitivity to the neutron electric form factor and the deuteron wave function is discussed.

Hole-strength distributions from the 34S(, 3He)33P and 34S(, t)33S reactions

Abstract A vector-polarized deuteron beam of 52 MeV was used to excite proton and neutron hole states via the 34S( d , 3He)33P and the 34S( d , t)33S reactions. From the measured angular distributions of differential cross sections σ(θ) and analyzing powers T11(θ) we determined the spins of 9 states in 33P and of 13 states in 33S. The comparison of proton and neutron pick-up spectra yields isospin assignments for 33S states (T = 1 2 , 3 2 ). Spectroscopic factors deduced from a DWBA analysis were used to determine the lowest moments of the strengths distributions in 33P and 33S. Combined with proton and neutron stripping data we calculate ground state occupancies and single-particle energies for 34S and determine the Fermi surfaces for protons and neutrons. This information allows the application of a recently published sum rule to predict Gamow-Teller strengths S+ and S−. Combined with previous data the extracted single-particle energies exhibit systematic features which we parametrise as linear functions of mass number A and isospin To for target nuclei with 28 ⩽ A ⩽ 52. The parameters are closely related to effective particle-hole interactions.