P.W. Lisowski

Polarization transfer in the 2H(d,n)3He reaction at θ = 0°

Abstract The vector polarization transfer coefficient K y y ′ and the tensor analyzing power A zz have been measured for the 2 H( d n ) 3 He reaction at θ = 0° over an incident deuteron energy range from 1 to 15 MeV in 0.5 MeV steps. The results agree with the previous 2 H( d n ) 3 He measurements of Simmons et al. and are nearly identical to the 2 H( d n ) 3 H measurements of Clegg et al. in the region of overlap. The present results provide an accurate and complete set of the observables necessary to use the 2 H( d , n ) 3 He reaction as a source of polarized neutrons.

Four-nucleon studies: (III). Measurement of the 2H(d, p)3H polarization via the 3H(→, d)2H reaction and comparison to polarization in 2H(d, n)3He

Abstract Accurate angular distributions of the analyzing power in the 3 H ( p , d ) 2 H reaction were measured at eight energies from 6.7 to 14.7 MeV. By reciprocity, these analyzing powers are the same as the proton polarizations of the 2 H ( d , p ) 3 H reaction from 2.0 to 14.0 MeV. The products P1 (θ)σ(θ) were fitted with a series of even-order associated Legendre functions, and two terms in the series were found to be sufficient to describe the reaction up to 14 MeV. Comparisons are made with the polarizations from the mirror reaction 2 H ( d , n ) 3 He , and good agreement is found when the reactions are compared at the same exit-channel energies. The implications of this are discussed in the light of other recent comparisons which suggest that differences in these mirror reactions may be a violation of charge symmetry of nuclear forces.

The tensor analyzing power Azz AT θ = 0° for the 3He(d, p)4He reaction

Abstract The tensor analyzing power f zz has been measured for the 3 He( d , p) 4 He reaction at 0 = 0° over an incident deuteron energy range E d = 6.6–15.8 MeV in steps of 0.5 MeV. The present results agree with and extend the previous measurements of Gruebler et al . The present results indicate that this reaction is a very good tensor analyzer for polarized deuteron beams with energies up to 15.8 MeV.

Scattering of polarized neutrons from 3He

Abstract Angular distributions of the asymmetry produced by scattering 8.0, 12.0 and 17.1 MeV polarized neutrons from 3 He have been measured. The 2 H ( d , n 3 He reaction at θ = 0° was used as the source of polarized neutrons. The n + 3 He polarizations were evaluated using the measured asymmetries and the incident neutron polarization. The latter was calculated from a knowledge of the polarization transfer properties of the 2 H ( d , n 3 He reaction and the incident deuteron beam polarization. The resulting 8.0 and 12.0 MeV 3 He ( n , n ) 3 He polarization angular distributions are quite similar to those obtained in the 3 H ( p , p ) 3 H reaction, but disagree with earlier 3 He ( n , n ) 3 He results. The present data as well as other n + 3 He observables between 1.0 and 23.7 MeV were parameterized in terms of complex phase shifts.

Four-nucleon studies: (IV). Analyzing powers in the elastic scattering of protons from tritium

Abstract Analyzing powers with statistical uncertainties of approximately 0.005 have been measured for 3 H ( p , p ) 3 H elastic scattering using a proton beam from a polarized-ion source. Angular distributions with about twenty points for angles from 25° to 160° were obtained for E p = 9.4, 10.7, 12.0, 13.4 and 14.7 MeV. Partial distributions for the range from 110° to 160° were obtained for E p = 6.7, 7.4, and 8.0 MeV. The data have been parameterized in terms of complex phase shifts.

Four-nucleon studies: (II). Determination of the 2H(d, n)3He neutron polarization using a 16 to 22 MeV pulsed deuteron beam from the cyclograaff

Abstract The neutron polarization from the 2 H ( d , n ) 3 He reaction has been measured at 45° c.m. for incident deuteron energies between 16 and 22 MeV. In addition, a polarization angular distribution was measured at 18 MeV. The results show that the 45° c.m. polarization remains above 0.35 in this energy range, but the peak polarization has shifted to near 40° c.m. The usefulness of 2 H ( d , n ) as a source of 10 to 22 MeV polarized neutrons is discussed.

Analyzing power measurements for n-p scattering between 13.5 and 16.9 MeV

The analyzing power Aγ(θ) for neutron-proton scattering has been measured for θ = 90°(c.m.) from 13.5 to 16.9 MeV and from θ = 50° to 145°(c.m.) at 16.9 MeV. Extensive Monte Carlo calculations have been made to correct for multiple scattering effects. Overall uncertainties are about ± 0.002. All the Aγ(θ) data, but primarily those at 16.9 MeV, disagree with predictons based on the phase-shift sets which have been derived previously by way of global analyses of nucleon-nucleon scattering data. Data for the product σ(θ)Aγ(θ) have been fitted with an expansion of the form (sin θ)(a0 + a1 cos θ + a2 cos 2θ). For the first time the need for a non-zero a2 has been illustrated for energies below 20 MeV. This parameter is shown to be related to the nucleon-nucleon F-state spin-orbit phase parameter. In addition, the P, D, and F spin-orbit phase parameter values derived from the present data differ significantly from the ones based on the Yale-IV and Liver-more-X global analyses. The derived D and F spin-orbit phase parameters also differ from those obtained in the recent analysis of nucleon-nucleon scattering data by Arndt et al.

Comparison of analyzing power and polarization in the reaction 3H(p, n)3He: (II). New polarization results below 4 MeV

Abstract The polarization P y for the 3 H(p, n) 3 He reaction was measured for energies between 2 and 4 MeV. Special care was given to minimizing the effects of background and to interpreting the experimental spectra. The new values for P y are significantly higher than previous values, and comparison to the available data for the analyzing power A y for the same reaction now shows that in this energy range P y and A y are equal within experimental uncertainties. This equality negates earlier conclusions that sizeable differences existed between these observables. In particular, our new results demonstrate that in this reaction the effects of charge symmetry breaking on differences between these observables must be small.

A pulsed beam time pickoff system for nanoampere beams

Abstract A method has been developed for using fast plastic scintillators to provide a direct timing reference signal for pulsed beams in the MeV energy range. The system works well for both slow and fast risetime pulses and has been used for pulsed beams of 200 pA average intensity.

Polarization transfer effects in (p, n reactions on light nuclei at θ = 0°

Abstract Transverse polarization transfer coefficients K y y ′ have been measured at a reaction angle of 0° for the reactions 9 Be ( p , n ) 9 B , 11 C and 13 C ( p , n ) 13 N . In the energy range covered by these measurements, i.e., from about 7 to 15 MeV, the K y y ′ (0) values are generally positive. The polarization transfer excitation functions all show considerable structure which we largely attribute to compound nucleus effects.