Transverse RF Spin Rotatorfor the n-3He experiment

Christopher CrawfordUniversity of Kentucky

for the n-3He Collaboration

n-3He Technical Review

ORNL, TN 2013-01-08

Transverse RF spin rotator

Resonant RF spin rotator• P-N Seo et al., Phys. Rev. S.T.

Accel. Beam 11, 084701 (2008)

Properties suitable for n-3He expt.• Transverse horizontal RF B-field• Longitudinal or transverse flipping• No fringe field - 100% efficiency• Real, not eddy currents along outside

minimizes RF leaked outside SR• Doesn’t affect neutron velocity• Compact geometry• Matched to the driver electronics

of the NPDGamma spin flipper

Construction• Development in parallel with similar

design for nEDM neutron guide field• Few-winding prototype built at Uky;

Real RFSF being built now

field linesend cap windings

NPDGammawindings

n-3Hewindings

Inner / outer coil design

Windings calculated using scalar potential• Uniform transverse RF field inside• Zero leakage field enforced by B.C.’s• Copper wires run along equipotentials

1. Inner region:

2. Intermediate:

3. Outer region:

4:1 inside / outside winding ratio• By choosing

appropriate radii• Perfect cos theta

windings inside & out• 48 inner loops of

18 AWG wire

Status

Waiting for winding grooves to be machined in nylon forms

Alternate winding patterns

Three possibilities all give same field in high-frequency limitINNER INNER/OUTER OUTER

easiest to wind no eddy currents no copper in beam

All three wound using same grooves

R&D: test RF fields of each winding

Holding field:

Resonant frequency:

Inductance: 4.5 mH

Capacitance: 7.5 nF

Resistance: 5.1 Ω

Maximum voltage:

Stored energy:

Dissipated power:

Quality factor: Q=151

Electrical specifications

•RF field strength depends time spent in RFSF.

•High energy neutron beams (~20 meV) will be travelling upwards of 1000 m/s

•These neutrons will spend approximately 398 microseconds inside the RFSF and need to rotate π-radians

•Flip rate:

•The maximum value of the required rotational field is then,

•The maximum value of the required RF field is exactly twice this,

•To produce this field, we calculate the maximum value of required current given the winding spacing of the inner coils.

•Proportionally Constant:

Electrical specifications