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Polarization observables in nuclear reactions with stable beams have provided important information concerning structural properties of nuclei and reaction mechanisms and hold great promise in the context of exotic nuclei. We report on the development of a polarized target based on plastic foils of 20–200 μm thickness to be used with radioactive ion beams. The operation of such a target requires a moderately high magnetic field and very low temperatures. The plastic foil is placed inside a chamber attached to the mixing chamber of a 3He–4He dilution refrigerator. Cooling of the foil is achieved via a superfluid film of 4He that can be supplied through two capillaries. The chamber has two thin, highly uniform silicon nitride windows. An NMR coil is attached to the target to monitor the polarization. Results of a first test to characterize the target system, using the elastic scattering of 38 MeV 12C by protons in inverse kinematics are presented.

An intensive program of n-p measurement of spin observables in elastic and pion production reactions has been performed at the Paul Scherrer Institute taking advantage of the high intensity polarized neutron beam. In the elastic reaction 16 different spin observables have been measured for kinetic energies from 210 to 590 MeV with the centre of mass angular range from 60 to 180 degrees. This will allow to perform direct reconstruction in the model independent way of the isospin I=0 scattering amplitudes in elastic NN interaction. Three body final state process \(\vec np - pp\pi ^ - \) with polarized neutrons in exclusive experiment has been investigated.

The kinetic energy spectrum and the polarization of the PSI neutron beam produced in the reaction 12C(p,n)X at 0° with 590 MeV polarized protons were investigated. A strong energy dependence of the neutron beam polarization is observed which was not expected at the time the neutron beam was built.

The analyzing power, $A_{oono}$ , and the polarization transfer observables $K_{onno}$ , $K_{os''so}$ and $K_{os''ko}$ have been measured in neutron-proton elastic scattering at 260, 318, 386, 472 and 538 MeV for c.m. scattering angles between 64° and 160°. The data were obtained at PSI with a polarized neutron beam and a polarimeter analyzing the transverse polarization of the outgoing proton. They make a significant impact on the knowledge of the Isospin I = 0 nucleon-nucleon scattering.

We have measured the tensor analyzing power of d- 4 He elastic scattering at θ d = 150° in the energy range from 30 to 52 MeV. In this region the analyzing power is large, and the process can be employed as a standard to calibrate the tensor polarization of deuteron beams.

Cross-section and vector-analyzing-power data for three star configurations of the ${}^{2}\mathrm{H}(p\ensuremath{\rightarrow},pp)n$ breakup reaction at ${E}_{p}^{\mathrm{lab}}=65$ MeV were measured in a kinematically complete experiment. They are compared to rigorous Faddeev calculations involving five realistic charge-dependent nucleon-nucleon potentials: Argonne ${v}_{18},$ CD Bonn, Nijmegen 93, Nijmegen I, and Nijmegen II. A general satisfactory agreement between theory and experiment has been found. However, there exist also a few minor discrepancies in cross sections in some regions of phase space. The experimental data are compared also to the calculations including the (\ensuremath{\pi}-\ensuremath{\pi}) Tucson-Melbourne three-body force. Their effects are either negligible or increase the disagreement with the experiment.

Kinematically complete breakup cross section and proton analyzing power data for four different collinearity configurations (neutron at rest in the c.m. system) have been measured in the reaction [sup 2]H([ital [rvec p]],[ital pp])[ital n] at [ital E][sub [ital p]][sup lab]=65 MeV. The experimental data are compared with rigorous solutions of the Faddeev equations using the Argonne AV14, Bonn B, Nijmegen, and Paris potentials. While the overall agreement is quite good there exist distinct discrepancies between theoretical and experimental cross section and analyzing power data in some regions of phase space.

A polarized neutron beam at PSI has been used to measure the spin-dependent neutron-proton total cross sections Δσ L and Δσ T from 140 to 590 MeV. The results are compared with recent phase-shift calculations.

To take full advantage of a low velocity beam in the production of intense polarized hydrogen atomic beams a new sextupole magnet system has been developed and installed on the atomic beam apparatus of the ETH polarized ion source. Both practical considerations and theoretical investigations provided the criteria for the general design of the two-magnet system. The pole pieces are designed in a modular way, which allows to match the two-magnet system to various geometries of the apparatus and to different beam temperature. A new method was used which is based on the calculation of acceptance diagrams in order to investigate an optimal configuration of the whole system (diaphragms, magnets, drift spaces, ionizer). The efficiency of the beam transportation, defined as the ratio of the mean atomic density in the ionizer to the density at the skimmer location, is calculated to be one order of magnitude larger than in the previous source at room temperature.

The surface recombination of atomic hydrogen occurring during the cooling process in the production of a high density hydrogen atomic beam is treated. Several types of material, coatings and cryogenic layers have been investigated in order to find a good recombination inhibiting surface at low temperature. Adding a small amount of N2 gas to the hydrogen gas in the dissociator was found to reduce strongly the recombination rate in a range of a few degrees around 35 K. From the density measurements of the atomic beam it was possible to extract the behaviour of the recombination coefficient γ as a function of the temperature. Comparing this behaviour with theoretical models allows the determination of the adsorption energy of H on the actual surface of the accommodator. Without the addition of N2 the density behaviour is mostly characterized by the recombination probability of H on H2O. The deduced value of the adsorption energy of H on H2O is 470 K, which agrees with previous results. The adsorption energy of H on a cryogenic layer of N2 is determined for the first time and found to be 180 K.

At PSI a polarized neutron beam facility has been set up and was used to measure neutron-proton total cross section differences ΔσL and ΔσT in the energy range from 140 to 590 MeV.

We have measured polarization transfer observables Ky′y (θ), Kx′x (θ) and Kx′z(θ) for proton-proton scattering at 25.68 MeV with an accuracy of 0.007–0.012. Phase shift analyses of these data together with differential cross section and analyzing power data at the same energy yield an essentially model independent determination of the 1S0, 3PJ and e2 parameters at this energy. These parameters provide a test of nucleon-nucleon potential models and favour Paris and Nijmegen potentials.

The polarization-Transfer observables Kyy1(θ), Kxx1(θ) and Kzx1(θ) for proton-proton scattering have been measured at Ep = 25.68MeV. A simultaneous phase-shift analysis of these new data with differential cross section and analyzing power data at the same energy resulted in a very accurate determination of the p-wave phase-shift combinations ΔC, ΔLS and ΔT and of the 3F2−3P2 mixing parameter ϵ2. With this complete set of high precision data a critical test of microscopic NN-potential models has been performed.

The polarization transfer in p-d elastic scattering was shown to be sensitive to the details of the tensor force in the N-N interaction. Therefore measurements of the polarization transfer coefficients in this scattering have been carried out at an incident proton energy of 22.7 MeV. The data are compared to rigorous Faddeev calculations using different N-N potentials. The observable most sensitive to details of the potentials is the nucleon-nucleon polarization transfer coefficient K y y′ (Wolfenstein’s depolarization parameter D). The agreement of the K y y′ data with the calculations using the Bonn A potential is much better than with the Paris or Bonn B potentials. Results of recent measurements of K z x′ are presented and compared to the calculations. Measurements of the polarization transfer to the recoil deuterons are in progress.

Differential cross sections, vector and tensor analysing powers of deuterons elastically scattered by 40 Ar at 9.0, 10.75 and 12.0 MeV have been measured. The results have been analysed in terms of an optical potential containing complex central, spin-orbit and tensor terms. It is found that not only could all five observables be fitted very well but the parameters found also give excellent predictions for the excitation function of the cross section and T 20 at 175°, as well as for the 15 MeV vector analysing power data.

Precision measurements of the angular distributions of the vector and the three tensor analysing powers of the mirror reactions 2 H(d, p) 3 H and 2 H(d, n) 3 He are compared betwen 1.5 and 15.5MeV incident deuteron energy. Large and complex differences are observed over the whole energy range. After applying approximate Coulomb corrections, the discrepancies are essentially constant above 4 MeV deuteron energy. Although at present calculations which treat the Coulomb interaction in an exact way cannot be made, there is strong evidence for charge symmetry violation in these mirror reactions.

An investigation of states of maximum possible polarization in dα elastic scattering has been carried out between 3 and 43 MeV deuteron energy. Two different types of such maxima were found. In the first type, analyzing power components reach their theoretical maximum values. A second type does not generally yield observables with maximum possible values, but has parameters that lie well within the range allowed. It is a particular combination of values that constitutes a state of maximum possible polarization. The search for the two types of maxima was made with the aid of a phase-shift analysis. Several maxima of both kinds were found in the elastic scattering under investigation. The energies and scattering angles for these points have been determined. In most cases a state of maximum polarization indicates a resonant state in the compound system.

We have measured angular distributions of the analyzing powers A/sub y/, A/sub x/x, A/sub y/y, and A/sub x/z for the /sup 2/H(d,p)/sup 3/H reaction at deuteron lab energies E/sub d/ of 13.39 and 17.00 MeV. These distributions do not show the symmetry or antisymmetry about 90/sup 0/ (c.m.) expected on the basis of a simple direct-neutron-transfer reaction mechanism. In a companion experiment, we have measured the same four analyzing powers for both the /sup 2/H(d,p)/sup 3/H reaction and its charge-symmetric partner /sup 2/H(d,n)/sup 3/He at E/sub d/ = 15.50 and 17.00 MeV in a restricted angular range. These latter data were obtained by simultaneously detecting the tritons and helions. Only small differences were observed in the respective analyzing powers for the two reactions, which suggests a weakening of the mechanism responsible for the larger differences found by others at lower energies.

Six polarization transfer coefficients of the d-α elastic scattering have been measured at an incident deuteron energy of 11.9 MeV and a scattering angle θlab = 37.3°. Together with earlier data on cross section and analyzing powers, a complete set of measurements allows to deduce the d-α M-matrix directly from experiment.

The reaction 12 C( d , p) 13 C was investigated with polarized deuterons of 12 MeV energy. The differential cross sections and all analyzing powers T kq were measured for the ground state and for 3 bound and 4 unbound excited states of the residual nucleus 13 C. The results are compared to a finite-range DWBA calculation.

We describe the design and the calibration of a high-efficiency polarimeter which is sensitive to the deuteron tensor polarization t 20 and capable of working in a high background. The polarimeter is based on the 3 He(d,p) 4 He reaction, calibrated in the energy range between 10 and 36 MeV; it has an average efficiency of 0.7 × 10 −4 and an average analyzing power of T 20 = −0.5. The use of this polarimeter to measure the tensor polarization t 20 of the recoil deuterons in π + -d elastic scattering is described.

An evaluation of polarization measurements on the 3 He ( d , p ) 4 He reaction shows that the experimental values of the analysing powers A y and A yy reach nearly unity between 9 and 10 MeV. A search for A y = 1 and A yy = 1 values in this energy region was performed experimentally. The precise energies and angles for the maxima were found by interpolation of the experimental data. The value of the A yy maximum found is compatible with 1 within the experimental error. No A y = ±1 point could be detected.

The differential cross section and the analyzing power A/sub y/ for /sup 9/Be(t,t)/sup 9/Be and /sup 12/C(t,t)/sup 12/C elastic scattering have been measured at 15 and 17 MeV over the angular range theta/sub lab/ = 17.5--165.0/sup 0/. The data in the forward hemisphere have been analyzed with a standard optical model. A large depth and conventional geometry parameters for the spin-orbit potential have been found. The results of the present analysis are in general agreement with previous work involving polarized tritons scattered from heavy target nuclei and show important differences from investigations of the scattering of polarized helions on light nuclei.

Angular distributions of the analyzing power and differential cross section for /sup 3/He(t,t)/sup 3/He elastic scattering are reported for triton bombarding energies of 9.02, 11.00, 13.02, 15.02, 16.00, and 17.02 MeV, over a c.m. angular range from 25degree to 155degree. Excitation functions for the analyzing power are presented for the energy range 14.42--17.22 MeV. Problems in the phase-shift analysis of the data are discussed.

An investigation of the conditions for which the vector analysing power or a component of the tensor analysing power reaches its theoretical maximum value has been carried out. For d-α elastic scattering, a search for Ayy = 1 and Ay = −1 was made with the aid of a phase shift analysis. Three such points for Ayy and one possible point for Ay were found in the energy range between 3 and 17 MeV. The precise energies and angles for the maxima of Ayy were found experimentally using an interpolation method. The practical interest in using the results to calibrate polarized deuteron beams is discussed. A time reversal invariance test in connection with the findings of this investigation is proposed.

Angular distributions of the differential cross section and analyzing power At have been measured for 1H( t , t)1H scattering at center-of-mass energies Ec.m. = 1.26, 1.68, 2.19, 2.70, 3.21 and 3.71 MeV. At the highest energies, large differences are observed between At and the analyzing powers Ap for 3H( p , p)3H scattering. It is shown that the experimental results can yield detailed information on the odd-l spin-orbit and odd-l tensor nucleon-nucleon forces.

For 22 bombarding energies in the Ep = 2.0–46.3 MeV region p-d differential cross sections were continued to the neutron transfer pole in the cosθ plane with correct handling of the three-particle state Coulomb effects. The extracted value of the deuteron S-state asymptotic normalization constant AS is A S = 0.8781 ± 0.0044 fm −1 2 . The relation to other determinations is also discussed.

The design and performance of a double-scattering apparatus with a large solid angle acceptance for polarization experiments is described. It allows, by magnetic focusing of a scattered beam to a small spot of a few mm in diameter, the use of highly efficient polarimeters for protons and deuterons in the energy range between 2.5 and 30 MeV. The maximum solid angle is 20 msr. The scattering angle can be varied between −20° and 150°.

Cross-section and tensor analyzing power data of d—p elastic scattering in the deuteron energy region between 5 and 45 MeV are used to determine the asymptotic D- to S-state ratio ϱ D of the deuteron wave function. The data obtained at ten different deuteron energies give consistent results. An averaged value of ϱ D = 0.0259 ± 0.0007 was found.

The differential cross section, the vector- and the tensor-analyzing powers of the reaction 2 H( d , p) 3 H have been measured. The polarization data were obtained at 11 energies between 1.0 and 13 MeV at lab angles between 5° and 160°. The data were fitted with Legendre polynomials and the resulting coefficients analyzed for resonances in 4 He. Overwhelming evidence for a 1 − level at 24.1 MeV and a strong indication of a 4 + level at 24.6 MeV excitation energy have been found.

Angular distributions for the cross section and the analyzing powers iT 11 , T 20 , T 21 and T 22 in the angular range 20°–175° (lab) have been measured for 12 MeV deuterons scattered elastically from several medium-heavy, spin-zero target nuclei. The data have been analysed using an optical model including complex spin-orbit and tensor terms. With a few exceptions, excellent fits have been obtained to all the measured quantities, yielding a set of global parameters. The depths of the central part of the optical potentials are correlated and depend on the structure of the target nuclei. Contrary to the results for selenium, which exhibit clear shell-closure effects that are well reproduced by optical-model calculations, the data for N = 28 nuclei were found to be very difficult to describe. Irregularities in the optical-model parameters and problems in fitting the measurements are discussed. Possible ways of improving the theoretical description of deuteron scattering are suggested.

Between 0.32 and 5.0 MeV deuteron energy a phase-shift analysis of 3He(d, d)3He crosssection and deuteron analyzing-power data has been made. Expressions relating the analyzing powers to the scattering amplitudes are derived and an energy-independent parametrization of threechannel scattering matrices is given. The analysis includes spin-orbit splitting, mixing of states and loss of flux to reaction channels. Excellent fits have been obtained. However, the data set has proved to be too incomplete to permit a unique determination of the relevant parameters. At low energies continuum ambiguities have been found and explored. Common properties of the solutions point to the existence of several broad highly excited states of the 5Li nucleus.

An analysis is made of the possible use of an electron-cyclotron-resonance (ECR) discharge as an ionizer for a slow beam of nuclear-spin-polarized H 0 or D 0 atoms. Previous concerns that the nuclear polarization would be lost because inside the ECR discharge are found likely to be wrong. Further analysis of experience gained with ECR sources for other applications indicates that an ECR ionizer may achieve absolute ionization efficiencies for H 0 and D 0 beams substantially better tha present electron-bombardment ionizers, and perhaps as high as 20%. The output ion beam should have energy spreads ⩽ 5 eV. Suggestions are then made for the best design of such an ECR ionizer for a badly needed experimental test of these ideas.

A new general method for the precise calibration of beam polarization or analyzing power in spin-12-spin-0 elastic scattering has been developed. This absolute calibration method uses the double scattering technique in connection with modern polarized ion source technology. It is based on an incident beam with at least two different polarization states and is independent of beam energy and scattering angle. The application to p-α elastic scattering at 25.68 MeV and a lab, angle of 117.5° is described. The result is a new determination of the analyzing power to an accuracy of better than 1%, i.e. Ay = 0.8119 ± 0.0076. Systematic errors are extensively discussed.

Complete angular distributions of the differential cross section σ, the vector analyzing power Ay and the tensor components Ayy and Axx of the 4He( d ,3He)3H reaction were measured at Ed = 32.1, 35.15, 39.6, 44.9 and 49.7 MeV. The angular distribution of the tensor analyzing power Axz was measured at 35.15 MeV. The measurements have been carried out with high precision and the polarization data have been calibrated by the dα elastic scattering. The results have been analyzed in terms of Legendre polynomials. Charge symmetry breaking effects have been investigated by observing the deviations from the forward/backward angular symmetry.

A monitor for polarized proton beams at energies above 3 MeV is described. It provides information on intensity and polarization profiles of the beam as well as on characteristics of beam modulations. Extensive experience with this monitor has been obtained at E p = 5 MeV. Results are discussed in the context of a parity violation experiment using a 5 MeV polarized proton beam. Accurate new measurements of the 12 C( p , p) 12 C analysing power show the usefulness of this monitor at other energies.

Angular distributions of cross section and analyzing power A y of protons scattered on deuterium were measured between 8.5 and 22.7 MeV. For the corresponding energy of incident deuterons scattered from hydrogen, angular distributions of the deuteron vector and tensor analyzing powers A y d , A yy and A xx were measured at 6 energies between 17 and 45.4 MeV. The proton and deuteron data together with corresponding data at lower energies are analyzed in terms of Legendre polynomials. The energy dependence of the resulting coefficients are discussed.

Measurements of three vector-to-vector and seven vector-to-tensor polarization transfer coefficients of the 2 H 1 H elastic scattering at E p = 10 MeV are reported in the angular range between θ cm = 92° and 180°. These second-order observ are compared with Faddeev calculations. It is shown that the vector-to-tensor components depend largely on the details of the N-N P-wave interaction.

The polarization transfer coefficients K x x ′ , K z x ′ , and K y y ′ for 3 He(p, p) elastic scattering (Wolfenstein parameters R , A and D ) were measured at incident energies of 6.82, 8.82 and 10.77 MeV at up to four angles. Polarized protons scattered by a liquid nitrogen cooled 3 He cell were focussed by a magnetic quadrupole lens into a high pressure polarimeter filled with 4 He. The measured values compare satisfactorily with values calculated from previously determined phase shifts, from an R -matrix analysis of p- 3 He scattering and from microscopic calculations based on an approximate nucleon-nucleon potential.

An atomic beam apparatus producing a polarized neutral atomic beam is described. The beam intensity, its diameter and the mean velocity of the atoms are measured. The results of the investigation of the dependence of various parameters are presented. The results are used to optimize all parameters involved. An optimum atomic beam intensity of 1.8 × 10 16 atoms per second is measured within a beam diameter of 10 mm.

The mechanisms of isospin violation in the reaction 4 He ( d , 3 He ) 3 H is studied, in the framework of a microscopic model. To describe realistically the intermediate 6Li nucleus and the fragment states we use the refined resonating group model (RRGM). A detailed analysis of the matrix elements responsible for the asymmetry of cross sections and vector analyzing powers is presented. The isospin violation is found typically of the order of 5–10% and arises mainly from coupling to intermediate “5 + 1” structures in a two-step mechanism. The agreement with the experimental data is fair.

The parity nonconserving asymmetry A γ in the decay of polarized 19 F ∗ (110keV) nuclei has been measured. A value of A γ = − (6.83 ± 2.11) · 10 −5 (total error) was found. Systematic errors are extensively investigated and found to be small. The absolute normalization is given by the 19 F ∗ polarization, which is found to be P F = −0.52 ± 0.08 in a separate experiment, using a calibrated Compton polarimeter. The new result A γ ( 19 F) is compared to earlier experiments and recent theoretical calculations. From an analysis including 18 F and 21 Ne results, constraints on the weak meson-nucleon coupling constants ƒ π and h 0 ρ are deduced. Agreement with calculations based on the standard electroweak theory and QCD is found.

The tensor analysing power T 20 for the 3 He ( d , p ) 4 He reaction at 0° has been measured between 0.34 and 11.60 MeV. Absolute calibrations of the measurements have been carried out at 6.69 MeV with the aid of the 16 O d ,α 1 14 N ∗ reaction and at 3.92 and 11.56 MeV with the 4 He ( d , d ) 4 He scattering. Excitation functions of the vector analysing power iT11 for d-α elastic scattering have been measured between 2.38 and 13.60 MeV at θlab = 37.5° and 45° and calibrated absolutely at 4.57 and 11.88 MeV.

Differential cross sections and vector and tensor analysing powers of deuterons elastically scattered by 40Ar, 40Ca and 60Ni have been analysed in terms of an optical potential containing tensor terms. The effect of two optical potential tensor terms on the various analysing power components have been investigated. It was found that the quantity T20 at 180° is particularly sensitive to the optical potential tensor parameters. Although the differential cross section and the vector analysing power data were already well reproduced without any tensor interactions in the optical potential, the inclusion of tensor terms improved greatly the fits to the tensor analysing power data, resulting in a fairly satisfactory agreement.

The differential cross sections, dσ(θ) dΩ , and the vector analysing powers, iT 11 ( θ ), for 12 MeV vector polarized deuterons scattered elastically from 40 Ar, 46,48,50 Ti, 52,54 Cr, 54,56 Fe, 58,60 Ni, 76,78,80,82 Se and 90 Zr were analysed assuming two-channel, 0 1 + −2 1 + , coupling. In contrast with the results of conventional optical model analysis for the same isotopes, the two-channel potential parameters are found to be described well without B (E2; 0 + −2 + ) dependence.