Speaker
Description
The sparsity of spin dependence data in nuclear collision physics is due to the experimental inconvenience of center of mass (CM) particle kinetic energies (KEs) required to be in the range from 100 KeV to 1 MeV in order to be comparable with Coulomb potential energy barrier heights. Small compared to all nucleon rest masses, the lab frame and the CM frame then coincide.
Particles in the 100's of KeV energy range are easily produced in vacuum, but their ranges are negligibly small in matter, and too low in energy for study in any magnetic storage ring.
To study spin dependence in nuclear scattering, one must cause the scattering to occur in what is at least a weakly relativistic moving frame of reference.
This is possible, using a predominantly electric storage ring E&m-SR with weak magnetic bending superimposed. The presence of magnetic bending makes it possible for two beams of different velocity (owing to their different particle type) to circulate in the same direction, at the same time, in the same storage ring.
The presence of ``rear-end'' collisions between two particles co-moving with substantial, but slightly different velocity in the laboratory, allows their CM KEs to be in the several 100 KeV range, yet all incident and scattered particles have convenient laboratory KEs, two orders of magnitude higher, in the tens of MeV range.
This permits incident beams to be established in pure spin states and the polarization of scattered particles measured with high analyzing power and high efficiency.
With careful tuning of E and B, certain baryon bunch pairs of different particle type, such as d and h (helion) or p and d, to have appropriately different charge, mass, and velocity such that their rigidities are identical; both beams can then co-circulate indefinitely, with different velocities.
By design, all nuclear collisions will then take place in a coordinate frame moving at convenient semi-relativistic speed in the laboratory, with CM KEs comparable with Coulomb barrier heights.
One proposed configuration has d and h beams circulating concurrently in the same storage ring,with parameters arranged such that, in the (maximally exothermic, 18.3 MeV per transmutation event) process d+h -> p+alpha, rear-end collisions always occur at an intersection point (IP) which detects the events.
