To accommodate the very high heat load of this new, brighter source, the old swappable A2 monochromators have been retired, and replaced by a dedicated double-bounce diamond system behind a removable white-beam vertical-focus mirror. The front-end has been entirely rebuilt, and is now window-less from CESR all the way to the hutch. The new beamline is extremely versatile, delivering bright monochromatic x-ray beams at any incident energy between 5 keV and 70 keV. The combination of narrow band-pass of dE/E ~ 10-4 with a delivered flux of over 1012 ph/s/mm2 over a wide range of energies is ideal for the mission of A2: high-resolution diffraction studies of crystals, thin-films and powders, under dynamic “operando” conditions and in extreme environments. Additional upgrades during the spring of 2015 down will allow for a complementary white-beam configuration at A2, extending the range of possible experiments to include transmission Laue diffraction and white beam topography on very short timescales. The inaugural A2 undulator experiments have been selected from peer-reviewed competition and are currently underway during the fall 2014 run. We are now soliciting proposals for user experiments for 2015 which aim to fully exploit this fantastic new capability at CHESS. Potential users are encouraged to contact Jacob Ruff with inquiries.
A2: Out with the wigglers; in with the undulators
The CHESS West wiggler source was removed over the summer. In its place are two custom 1.5m CHESS Compact Undulators which now feed the A-line/G-line endstations.
Figure 1: Undulator harmonics measured at A2: Here we show a portion of the spectrum of delivered flux to the A2 endstation. The 1.5m CHESS compact undulator was positioned near the maximum deflection parameter for this measurement, with the fundamental harmonic at 2.25 keV. This plot shows the 3rd, 4th, 5th, 6th, and 7th harmonics. The full energy range of A2 is much greater than shown, spanning a range from 5 keV to 70 keV.