Non-Invasive Spin Polarization Monitoring

High quality spin polarization is an expectation for many users of Nuclear physics facilities. Accelerator operators and designers currently do not have real time, non-invasive polarization monitors, and no direct way to automate polarization quality optimization. The Thomas Jefferson National Laboratory (JLAB), Cornell’s Laboratory of Elementary-Particle Physics (LEPP) and, Electrodynamic, have joined together in a collaboration dedicated to finding solutions to this recognized need. Two radically different potential solutions have distilled from this collaboration, one for monitoring longitudinal spin polarization, and another for monitoring transverse spin polarization. This Phase I SBIR will determine the feasibility of both approaches by developing custom hardware and electronics necessary for their evaluation on the CEBAF beamline. The longitudinal spin polarization design is based on Lenz’s law, that an electron bunch with longitudinal spin polarization passing through a small metal ring will induce a current that generates a force that opposes its passage. Two techniques will be developed to enhance the power exchange between the beam and the ring, one passive and one active. The passive technique involves locating the ring within a resonant cavity that reinforces and builds the Lenz current increasing power extraction from the beam. The active solution will involve externally driving an enhanced Lenz current to increase the oppositional forces on the passing bunches and increase the power extracted. A sensitive low-noise direct conversion I/Q demodulating receiver amplifies the power extracted from the beam and determines north/south, or south/north longitudinal polarization of the electron bunches by comparing the phase of the signal to the accelerators clock signal. The transverse polarization monitor measures small polarization dependent transverse deflections of the beam as it traverses in-place quadrupole magnets. A symmetric coaxial cavity resonator that is sensitive to the deflection will be connected to a low-noise phase sensitive receiver and provide a means determine the transverse bunch polarity direction. While both potential solutions are different, they both will require sensitive low noise receivers to be designed and constructed and they both require hardware to interact with the beam. Both the hardware and electronics will be delivered to Jlab during Phase I. Commercial Applications: Low-noise phase sensitive receivers have many applications in charged particle acceleration including polarimetery and high resolution beam position monitoring. The hardware in development has applications in several facilities.