C-Line Windowless Operation: Very successful…well done CHESS! Easier alignment More light at lower energy Slit stage allows for a lot of flexibility and experiments which will lead to more accurate fitting functions. TASLITX= +46 : wide open NO filter +31.4 : 171 micron, no filter +21.4 : 105 micron, no filter +10.8 : 58 micron, no filter + 0.8 : 35 micron, no filter -9.45 : open, diamond filter (fine tuned position) -19.0 : 35 micron, diamond -29.4 : 105 micron, diamond -39.63 : open, Molybdenum filter (fine tuned position) ( Straight through - No horizontal limit at optic )

Why are we doing this? In the simplest case, the Coded Aperture fitting function depends on the aperture sizes and positions. It also depends on gold thickness which determines the transparency and phase shift (January 2012), and on the x-ray energy spectrum (power distribution) seen by the optic (everything other than the gold). We have been largely guessing the power distribution which is determined by… synchrotron radiation ( electron energy, bending radius and Jackson ) absorbers: silicon, diamond, and protective layers on the diode diode junction energy dependent efficiency . The relative pulse height transmission with the application of the diamond, or molybdenum, absorber is a additional guide (along with the image shape) to understanding the effective x-ray energy spectrum. The diamond absorber low energy cut-off (50% of high energy transmission) at about 1.6 keV. The Coded Aperture “transparent” silicon substrate blocks out much of the power between 1.8 – 2.4 keV. The molybdenum absorber has a peak at 2.5 keV, but also a high energy tail. The diamond absorber, with the silicon substrate, causes significantly more power loss below 1.8 keV, than above 2.4 keV.

For example Application of the diamond filter to Pinhole and Coded Aperture at 2.085 GeV indicates that the energy spectrum should be push to a lower average energy. However, the shape between the main peaks in the CA image indicates a strong high energy component, >3 keV. The image calculator now includes the energy dependent filtering. Improved fitting functions will come in the next few weeks. diamond transmission with Pinhole no diamond, affected by detector only run 23661, G=15, Ibeam= 0.59, area= 925 σ (image) = 1.28 pixel filtering with Diamond run 23660, G=15, Ibeam= 0.61, area= 508 σ (image) = 1.05 pixel Diamond transmission = 0.53 for energy spectrum without silicon filtering; a significant fraction of the energy spectrum is below 1.6 keV. diamond transmission with Coded Aperture filtering with Silicon and Gold run 23648, G=8, Ibeam= 0.64, area= 2919 filtering with Silicon and Gold and with Diamond run 23649, G=8, Ibeam= 0.53, area= 1481 Diamond transmission = 0.61 for energy spectrum pre-filtered by Silicon and Gold; there is still a significant fraction of the energy spectrum below 1.8 keV.