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Step-by-step guide

Femtosecond timing in sample chamber 1 (SC1) at CXI.

  1. Install a fast diode and mirror (roughly at 45 degrees with respect to the beam) on the SC1 sample_x stage
  2. Roughly align the fast diode and mirror using the reference laser at the time tool (-4 mm in position but this will soon be changed to 0 mm.   If the "out" position is 92 mm, then -4 mm, if 96 mm, then 0 mm).
  3. Insert a nozzle rod with both a clear YAG and a frosted YAG. 
    1. At CXI, the clear YAGs are typically thinner, around 20 um, whereas the frosted YAGs are thicker, around 50 um
  4. Align the laser with crosshairs on the inline cameras that represent the location of the X-ray beam
    1. In the image below, the bright spot is the laser spot at the interaction point (IP) visualized using a frosted YAG.  The frosted YAG is on the upper half of the image.  There is a small gap followed by the bottom 1/4 of the image having a clear YAG.
    1. The laser needs to be repointed using Pico X (CXI:LAS:PIC:03) and Pico Y (CXI:LAS:PIC:02). These PVs can be changed and chich of the tow motors does pitch and yaw can change so these are not set in stone.
  5. When the laser is roughly centered on the X-ray spot (the laser should be on the order of 100-150 um), the X-ray beam needs to be made similar in size at the interaction point to the laser.  In order to do this at CXI, insert Be lenses at the DG2 location to focus the beam upstream of SC1 and produce a larger, divergent beam at the IP.
    1. The DG2 lens screen is found in the DG2 section of CXI home
  6. The Be lenses will need to be aligned in both x and y using the DG2 PIM and then the DG2 slits will need to be closed to stop any intensity outside the Be lenses aperture
    1. Beam on DG2 without lenses
    2. Beam on DG2 with lenses but without slits aligned
    3. Beam on DG2 with lenses and with DG2 slits aligned
    4. The DG2 slits need to be closed such that there is no beam intensity outside the lens aperture.  If intensity remains outside of the lens aperture it will be focused to the 1.3 um spot size in the IP and damage the YAG at full intensity
  7. Open all gate valves and remove objects upstream of SC1 before bringing the beam to the IP. 
    1. Since the beam is being refocused upstream of SC1 to make the larger beam, we could inadvertently place the focused beam on upstream diamond windows or other objects and damage them
  8. Look at the beam on the clear YAG in SC1
    1. The beam should be similar in size to the laser beam or the signal used for timing in SC1 will be low

    2. Optional: Use the large beam at SC1 to align the DSB slits, SC1 jaws, and SC1 ap0 and ap1 motors to be roughly centered.  it is easy
  9. Hello

 

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