XOX: The X-Ray-Optical Cross-Correlator

One day this device might live up to its name. In the meantime it houses a ‘pulse arrival monitor’ or ‘timing tool’ that measures the relative arrival times of x-ray and optical laser pulses. The measurement is based on THz emission from ferromagnetic material irradiated by the x-ray pulse. The emitted Thz pulse is detected by the optical laser pulse via spectrally-encoded electo-optic sampling.

Downstream of the Thz emission sample is a filter holder and downsteam of that is the origal XOX imager, which can be used to align the x-ray beamline, as always.

Vacuum

Venting

  • Isolate XOX by closing and disconnecting beamline gate valves GV5 and GV3 to DPS2 and KBS respectively.
  • Stop turbos pumping. One is in Karabo, the other is local.
  • Open the supply of dry nitrogen to the manual venting valve and check it can be heard escaping from the overpressure valve.
  • Close the fast- and slow roughing valves.
  • Slowly open the venting valve while observing the pressure on PCC10. The valve requires about 1 turn before any increase in pressure is observed. Don’t be tempted to increase as the pressure rises - it is in the pressure range above about 1 mbar that damage to samples and filters will occur.
  • Loosten the screw on the fast access door to avoid overpressure.

Pumping down

  • Make sure the chamber is closed
  • Close the manual venting valve and shut off the supply of nitrogen
  • Open the slow roughing valve.
  • Go for coffee, or lunch, make a Karabo scene, or write documentation. But don’t rush.
  • Once the pressure reaches 1 mbar, open the fast roughing valve and close the slow one.
  • Start the turbo pumps.
  • Check the pressure is going down.

Interlocks

The XOX is different from most chambers in that its turbo pump is directly connected to the vacuum, without a valve in between, or even before. We want to isolate the XOX if the turbo pump makes problems, or the pressure goes high.

We close both the upstream valve GV5 and the downstream valve GV3. The systematic name for the downstream valve should be GV6, but this is in the KB loop so we cannot easily switch it from here. As the KB has no vacuum interlocks, it’s easier to put them here.

No Device Op Value
c1 SCS_BLU_XOX/TPUMP/TP1.state.RPM80 EQ FALSE
c2 SCS_BLU_XOX/GAUGE/P31.Value GT 1e-2
c3 SCS_BLU_XOX/GAUGE/PCC10.Value GT 1e-6
No Logic Action
a1 c1 or c2 or c3 CClose