Switch the Undulator

The two undulators cannot be used simultaneously!!! When one of them is in use (gap below 100 mm) the other must be at the maximum gap (100 mm) and zero phase and zero tapering. If both gaps are below 100 mm a beam dump will occur and all beamlines will loose the beam!
. Check here (The Beamline) the Energy Ranges of the two Undulators

8.1 HE
ID081 gap < 100 ID082 gap= 100 ENT slit-Y=-5.5

PREVER-Pitch=about 150 (this value may be different!!)
8.2 LE OPERATIONAL ID082 gap < 100 ID081 gap= 100 ENT slit-Y=+117.1
PREVER-Pitch=about -50 (this value may be different, but -200 is the typical shift from HE to LE)

Moving ENT slit Y

In case the GEFRAN encoder - BCS communication  is not working properly, follow these insctructions:
  1. Go to BCS web page which controls the ENT slit Y diggital stepper motor. Select '(7MVREL) Y axis relative move'.
  2. Go to the Entrance slit chamber and check its position.
  3. Move the motor by a few steps to be sure it is going to the right direction. When going from HE to LE, move by -200 steps.
  4. Go with small steps (max 5000) to the desired position. Both LE and HE positions are marked by red lines. Use small steps (500) in the central part, where the movement is not very smooth.
  5. Going from HE to LE takes about -60000 steps, from LE to HE +60000 steps.
  6. Go to the rack with the GEFRAN of the encoder and check the reading. Move the Ent slit Y by a few steps until the GEFRAN displays 132.1 for LE, 9.5 for HE setup.

DETAILED PROCCEDURE. FROM HE TO LE (Ask the assistance of a beamline scientist the first time you need to do this procedure!!!):

1 FEopenclose.VI. Close FE
2 082BACH Connect to Firefox and select the link ( 082BACH ) in the Bookmark Toolbar. As a fist action, open the gap of the undulator you are using (8.1) to 100 mm. Refresh the internet browser from time to time to follow the opening.

NOTE: Only when both Undulators are at 100 mm, you can close the gap of the undulator that you want to use (8.2) to 50 mm. Check in Firefox Bookmark Toolbar link 082BACH that the undulator has been switched. NOTE: after the injection the Control room closes the gap of the last used undulator. Therefore if you change the undulator during the injection, you will need to open again to 100 mm the undulator you were using!!!! A general rule is ALWAYS CHECK what is the gap of the 2 undulators before trying to move the gap with a Labview VI (e.g. SetEnergy&Undulator.VI).

3 Main Panel
Motor control.VI
Note that the following procedure is working only if the encoder electonics is working properly. If it is not the case, follow the alternative procedure described above (Moving ENT slit Y).

Select: Element: Entrance slit and Action: Y
Read. You should read User Units=-4.2 and Encoder=+9.7 for the HE undulator 8.1. Set the value: +117.5 (if you want to switch to the LE undulator 8.2) in the Go to position (User units) box and press Move.

Read. If there is some message Overwrite or restore, check if the two values are close (e.g. saved value 114 read value 116 and press Overwrite in this case, which is the most likely case.) If the two values are very different then press restore.
Read again. If the vaue is not 117.5 move again Entr Slit Y to 117.5. Tou should read User Units=+117.5, Encoder=+131.4 for the LE undulator 8.2

4 Set PreVERT PITCH.  Set a value which is 200 lower than the pitch you have read and you were using for first harmonics with HE und.
5 SetEnergyandUndulator.VI Change in the menu HEund to LEund and eventually also the mono grating if you previously changed also mono grating. Set the energy you need with Set energy and Undulator using 1st harmonic. Press => and then press Calculate, before pressing move. If everything works you should read a value between 19.01 and 50.

IMPORTANT! Before pressing MOVE ALWAYS CHECK what is the gap of the 2 undulators at this link BACH082): Both undulators should be at 100, especially the undulator you are NOT using MUST BE at 100, because SetEnergyandUndulator.VI will close the new undulator you are using). If by mistake the gaps of both undulators are closed below 100 mm a beam dump will occur!!!

IMPORTANT! Before pressing MOVE ALWAYS check that In Mono grating number.VI the right MONO grating is selected, especially if the compuer was restared (in thius case you will find EMPTY) or you have changed the grating.

6 Open FE. Change the scale of the keithley Io-7
7 ScanEnergyGALIL TEST.VI Select YES and Scan energy around the value you set.
8 Check that teh energy is on top of the harmonic or set it there
9 Optimize PREVert
Set PreVERT at the maximum value
Last Updated on Wednesday, 08 November 2023 19:40