First measurements and observations from the new permanent magnet undulator at the SRC

Abstract

In December of 2000 the University of Wisconsin Synchrotron Radiation Center (SRC) installed a new, state-of-the-art undulator in long straight section 2 of the Aladdin storage ring. This undulator replaced the first Aladdin undulator, which was on loan from the Stanford Synchrotron Radiation Laboratory and had been in use since 1986 [K. Halbach et al., IEEE Trans. Nucl. Sci. NS-28, 3136 (1981); H. Winick et al., Nucl. Instrum. Methods Phys. Res. A 208, 127 (1983); M. A. Green et al., Nucl. Instrum. Methods Phys. Res. A 266, 91 (1988)]. The new undulator was designed, constructed, and tested by Danfysik (Danfysik A/S, Moellchaves 31A, DK-4040 Jyllinge, Denmark). The undulator uses NdFeB permanent magnets for the magnetic structure and is 3.52 m long with 50 periods, each of 68.3 mm. The new undulator is intended to provide high flux from 7.8 to 500 eV. To cover this wide energy range we use the first through ninth odd harmonics. The magnetic structure has been phase-corrected to better than 2° rms and should provide fidelity better than 90% through the ninth harmonic. The resulting undulator flux will support an extreme ultraviolet nano-lithography beamline, a low energy Wadsworth beam line, and a high energy VLS-PGM beam line. Some coherence experiments are also anticipated. The undulator radiation has been analyzed using an existing HTM [M. C. Hettrick, Nucl. Instrum. Methods Phys. Res. A 266, 404 (1988)] monochromator, a durable filter-pinhole detector, and computer controlled, cooled, scanning apertures. We present measurements of the undulator harmonic content, energy and spatial structure of the undulator beam, and undulator beam position stability.