I replaced the monolithic Fe/Si analyzer with the Pi192 Co/Ti supermirror test piece in the analyzer solenoid of the NSE. The test piece was positioned with its long axis (200 mm) along the field (and beam) direction and its short axis (64 mm) vertical. The long axis of the test piece was reported by Ian Anderson to be the easy axis for magnetization. The leading edge of the test piece was located at the center of the coil (4056 mm from the sample position). A boroflex/Cd mask with a 4mm gap was placed against the leading edge of the test piece (see Fig. 1). For a 10A current through the polarizer coil, the field varied over the test piece from 62G down to 49G (see Fig. 1).
The current in the analyzer solenoid was raised momentarily to 48A and then reduced to 9.6A. A measurement in the direct beam gave a polarization P = 0.826(3) (see Fig. 2), which after 90 minutes was not significantly different P = 0.820(2). With a current of 45A in the analyzer coil (minimum field on sample is then 220 G), the measured polarization was 0.848(3).
The polarization was also measured to be P = 0.901(1) at the edge of the main beam by moving the second arm of the detector by 3cm from the beam center position (see Fig. 3). As well, the beam polarization measured from a coherently scattering sample was 0.863(3), confirming my earlier analysis that the center of the main beam is contaminated by a low-divergence unpolarized component transmitted through the polarizer.
The performance observed for this Co/Ti polarizer is acceptable for the operation of the NSE spectrometer.
This document was generated using the LaTeX2HTML translator Version 99.1 release (March 30, 1999)
The command line arguments were:
The translation was initiated by Nicholas Rosov on 2000-04-26