ANL, Argonne, Illinois, USA
The IEX beamline at the APS is currently in the commissioning phase. The energy resolution of the beamline was not meeting original specifications by several orders of magnitude. The monochromator, an in-focus VLS-PGM, is currently configured with a high and a medium-line-density grating. Experimental results indicated that both gratings were contributing to the poor energy resolution and this led to venting the monochromator to investigate. The initial suspicion was that a systematic error had occurred in the ruling process on the VLS gratings, but that proved to not be the case. Instead the problem was isolated to mechanical constraints used to mount the gratings into their respective side-cooled holders. Modifications were made to the holders to eliminate problematic constraints without compromising the rest of the design. Metrology performed on the gratings in the original and modified holders demonstrated a 20-fold improvement in the surface profile error which was consistent with finite element analysis performed in support of the modifications. Two gratings were successfully reinstalled and subsequent measurements with beam show a dramatic improvement in energy resolution.
ANL, Argonne, Illinois, USA
To provide independent operation of the two 2-ID beamline experimental stations, a new canted beamline design is being developed. The constraint of keeping the existing front end limits the canting angle. The optimal canting angle was determined to be 400 urad and is achieved by using a permanent magnet. A coil is added to the canting magnet to provide a steering adjustment of maxi-mum 40 to 50 urad. In order to increase the beam separation as well as to provide power filtering and higher harmonics rejection for the downstream optics, a dual mirror system with focusing capability is used as the first optic at approximately 28 m from the center of the straight section. The inboard mirror (2.6 mrad) reflects the inboard beam outboard while the outboard mirror (4.1 mrad) reflects the outboard beam inboard. The beam presented to the dual mirror system is defined by two 1 mm x 1 mm apertures. The maximum power absorbed by each mirror is 200 W. Two vertically deflecting monochromators with minimum offset of 17 mm are located in the First Optical Enclosure on the outboard branch. The monochromator for the inboard branch is located in the corresponding experimental station.