Dynamic polarization work at A. E. R. E., Harwell

In proton-proton scattering, when both incident and target protons have polarizations of P 1 and P 2 respectively in a direction normal to the plane of scattering, the differential cross-section, σ, at angle θ is given by σ( θ ) = σ 0 ( θ ) {1 + ( P 1 + P 2 ) P 3 ( θ ) + P 1 P 2 C NN ( θ )}. P 3 ( θ ) and C NN ( θ ) are the polarization and spin-correlation parameters of proton-proton scattering, and are functions of incident proton energy and scattering angle. The Harwell synchrocyclotron provides a choice of two proton beams at an energy of 142MeV ( a ) high intensity P 1 = 0, and ( b ) low intensity P 1 = ±0.48. P 3 ( θ ) is a well-known quantity, and the two remaining unknowns, P 2 and C NN ( θ ) can be obtained by comparing differential cross-sections measured with beams ( a ) and ( b ). Somewhat higher precision is obtainable in such a measurement of the target polarization P 2 than by either of the existing solid-state methods (Schmugge & Jeffries 1962; Abragam, Borghini & Chapellier 1962).