Instructions for using and running the Wavelength Monitor of SCAnCAn
This document is on Michele’s pink memory stick; it is named “ALICE Wavelength Monitor-datetime”. Please do add/modify as appropriate.
ALICE Wavelength Monitor
Start-Up:
1. Using ALICEDELL4 (above Cryo monitor) in control room: start Teamviewer. Connect to PC in
Diagnostics room. Log in (PW: 3r!pc0~1).
2. Start Matlab2014a (32 bit).
3. At top right of MatLab window click tab ‘ALICE wavelength DR’ to refresh the directory.
Click ‘Monitor’ to start the Wavelength Monitor
4. To start data acquisition click ‘Start DAQ’. Similar for stop.
5. When running, to keep the wavelength fixed (eg. For a SNOM scan) make sure the two tick
boxes ‘Enable grating control’ and ‘Update control room’ are ticked.
SNOM Imaging:
1. Make sure wavelength stabilisation software is turned off (ctrl-C ).
2. Set the spectrometer grating using the ALICE Wavelength Monitor window and
‘Spectrometer Wavelength Setting’ box.
3. Set the Undulator gap (using ‘FEL undulator gap drive’ window) to the nominal gap required
according to general calibration
4. Check power of the FEL using the Power meter in the Hall (move mirror MB1).
5. Tweak the gap to give the correct peak wavelength. Use ‘FEL beamline window’ and the
‘Downstream mirror: Trans’ button – use right/left mouse clicks while monitoring the power
level to just go off the peak, then move back to a stable position deemed to be 0.6 times the
peak power seen on the power meter. Be careful not to click on the other buttons next to
the ‘Trans’ button – keep the mouse very still!
6. Move mirror MB1 to send beam from power meter to diagnostics room.
7. Read off the actual wavelength from ALICE Wavelength Monitor window. Adjust the gap by
small increments to match the actual wavelength to the desired wavelength.
8. Make sure an appropriate channel is chosen for the Io signal – that is, at some wavelengths
there are absorption features present in the FEL spectra; these should be avoided. To
change channels move the BNC cable on the breakout box to the appropriate channel.
9. Ask the 1st commissioner if they want to check anything on ALICE.
10. Immediately before starting the scan check the ‘Save Data’ box in the Wavelength Monitor
11. Start the SNOM scan.
12. At the end of the scan, uncheck the ‘Save Data’ box in the Wavelength Monitor.
13. Ask 1st commissioner to grab a screenshot of ALICE console 2 showing the feedback to EPICS
over 1 hr.
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Readying I0 for SNOM
Boxcar (BC) integrator converts signal from single element pyro array to Volts.
Roaming scope: may be necessary to unplug single element pyro array signal from CH2. Connect the
BNC from ‘pyro array breakout box’ into CH2 on scope.
Set signal delay and dwell time (under display) on BC using screwdriver. Good set up has delay
(purple trace in figure below) near peak of the pulse and the dwell (green) at the end where the
signal is level with the pre-pulse level, as shown:
Remove the BC integrator BNC’s at scope from CH3 and 4. Connect the output I0 from the BC to CH4
scope. Examine the signal, may be necessary to open/close the slits on the spectrometer to regulate
the intensity of the signal.
Measurement 3 on scope is the mean of CH4.
Before starting SNOM scan, connect I0 BNC from CH4 on scope to the extension BNC cable nearby
(labelled) which then connects to ADC3 on the SNOM.
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