The angular correlation between the beta electron and antineutrino in nuclear beta decay is characterized by the dimensionless parameter a. The value of a for free neutron decay, when combined with other neutron decay parameters, can be used to determine the weak vector and axial vector coupling constants gV and gA and test the validity and self-consistency of the Electroweak Standard Model. Previous experiments that measured a in neutron decay relied on precise proton spectroscopy and were limited by systematic effects at about the 5% level. We present a new approach to measuring a for which systematic uncertainties promise to be much smaller.

We have measured the scintillation efficiency of organic, mineral-oil-base scintillator (NE 235) as a function of applied magnetic fields smaller than 50 G. Below a threshold of 1 G, this scintillator is insensitive to magnetic fields (less than 10−5/G change in scintillation efficiency). Above this threshold, the efficiency of the scintillator rises rapidly, the increase in efficiency reaches 1.5% at 40 G, and saturates around 100 G to a value of 1.8%.

The quasielastic p-p scattering in the deuteron has been studied at 145 Mev. Cross sections and asymmetries in a polarized beam have been measured. No deviation has been found from the simple impulse approximation predictions for the asymmetries. For the cross section, deviations of up to a factor of two have been found for cases where the struck particle had a large momentum before collision. It is shown that the extrapolation procedure suggested by Chew and Low can be qualitatively used to relate the results. The use of the extrapolation procedure in other similar cases is discussed.

Measurements have been made of the polarization and differential cross section in elastic $p\ensuremath{-}\ensuremath{\alpha}$ scattering at 147 and 66 Mev, in the laboratory angular ranges of 2\ifmmode^\circ\else\textdegree\fi{}-165\ifmmode^\circ\else\textdegree\fi{} and 10\ifmmode^\circ\else\textdegree\fi{}-45\ifmmode^\circ\else\textdegree\fi{}, respectively. These have been compared with recent calculations which relate the scattering amplitudes to nucleon-nucleon results. Because these calculations take into account the angular variation of the nucleon-nucleon amplitudes, better agreement is obtained than heretofore. A comparison of the polarization with that observed in inelastic scattering from several levels of a variety of spin-zero nuclei indicates a strong similarity between the elastic and inelastic data, which can be explained theoretically.

The angular distribution of the differential cross section and polarization in proton-proton scattering have been measured at 147, 118, 95, and 66 Mev; at the highest energy the angular range was 4° to 112° (center of mass), while at the other energies the region considered fell between about 20° and 80°. In each case the differential cross section is a few percent higher at 40° than at 90°, in disagreement with the recent results of Taylor at Harwell. The angular distribution of PdσdΩ indicates the necessity for F-waves in describing the interaction at 147 Mev, although these are not required at the lower energies. Measurements of the polarization at 45°, taken at 10-Mev intervals between 46 and 147 Mev, yield results about 20% higher than predicted by Gammel and Thaler.

The regenerative deflector system applied to the Harvard synchrocyclotron is described. The theory of LeCouteur has been extended to include the initial radial oscillations, and it is shown, both theoretically and experimentally, that only partial monochromatization of the beam occurs during regeneration. However, it is possible to internally limit the energy width of the regenerated beam at the expense of intensity. The theory is in good accord with experiment. The application of these results to the production of an intense external proton beam and more monoenergetic neutron and polarized proton beams is described.