As a part of the upcoming APS Upgrade, a group of APS Users has requested an undulator that is capable of producing x-rays with a variety of polarizations, including left- and right-circular, and horizontal and vertical linear polarizations.  The x-rays produced will be used for magnetic studies of materials.  For such studies, lower-energy photons are needed.  The requested photon energy range is 400 eV to 2000 eV.

The undulator also needs to be capable of rapid switching between left- and right-handed circular polarizations.  The magnetic signals of interest are weak – 10^4 or 10^5 times weaker than the main signal – so lock-in detection becomes essential for adequate sensitivity to the magnetic part of the signal.  A switching frequency of 10 Hz is requested; a frequency below ~5 Hz is too slow to be useful.

APS_1428594 EMVPU First Review