Final Specifications for STELLA Permanent-Magnet Prebuncher Wiggler

Final Measured Specifications for STELLA Permanent-Magnet Prebuncher Wiggler

Quantity	Target Value	Actual Value	Comment
Period	33.0 mm	33.0 mm	Based on existing hardware
Overall length	~34 cm	33.0 cm	Based on existing hardware
Pole material	Pure iron	Pure iron	Based on existing hardware
Magnet material	NdFeB	NdFeB	Based on existing hardware
Number of poles	20	20	Based on existing hardware
Number of full strength poles	16	16	First two magnets at start and end of wiggler at 84% and 41% average partial strength
Wiggler parameter, K	2.86	2.91	Target value corresponds to matching with 45 MeV e-beam and 10.6 mm laser beam
Effective field	0.928 T	0.9452 T	Actual resonance energy is 45.65 MeV^†
Actual peak field	TBD	0.9862 T	Corresponds to actual K
Magnetic gap (fixed)	~8.5 mm est.	8.14 mm	Corresponds to actual K
First integral, B_x and B_y	<75 G-cm	B_x = -0.2 G-cm B_y = 19 G-cm	Ambient field subtracted out of final measured values
Internal trajectory, B_x and B_y	<1,500 G-cm²	B_x not measured -860 £ B_{y £} +790 G-cm²	Actual value corresponds to <± 60 m m at 45 MeV for all z, wiggle averaged
Second integral, B_x and B_y	<1,500 G-cm²	B_x not measured B_y = -900 G-cm²	Actual value corresponds to <60 m m displacement at 45 MeV for all z, wiggle averaged
Integrated quadrupole, normal and skew	<100 G	Normal = 15 G Skew = 12 G	15 G corresponds to <1.5 G-cm steering variation across 1 mm extent of laser beam, and negligible beam rotation
RMS optical phase error	<10 deg.	2.6 deg.	10 deg is more than adequate for simple velocity modulation
Mech. shimming toler-ance for taper and cant	~ few mils	No shimming necessary	Need y-z full angle < ~0.2 mrad, x-z full angle < ~1.0 mrad
Wiggler array weight	TBD	75 lbs

^{† Resonance energy increases
by 1.8%/mm when e-beam is displaced from center of gap perpendicular
to poles.}