Beamline control
Starting beamline control panel; changing photon energy and polarization; adjusting Rx of SMU
Last updated
Starting beamline control panel; changing photon energy and polarization; adjusting Rx of SMU
Last updated
Usually the window of beamline control panel is always open on the left monitor. If it was closed you can find the golden star icon in the taskbar. Alternatively you can use the icon for BLC on the left screen:
Main menu displays the outline of all beamlines coming from UE112 undulator:
Switching Mirror Unit (SMU) is used to switch beam between two main branches, our branch is PGM2. Click on "SMU" button to open the control panel and make sure that circle in front of "PGM2" is green:
If it is not, then make sure that:
your neighbors at PGM1 finished their work
the beamshutter is closed
After that press the square button in front of "PGM2" to get the light and wait until "PGM2" indicator turns green.
If beam is directed to a wrong branch, beamshutter will not open.
SMU_2 switches beam between 1-Squared (dsl) and 1-Cubed (dsr) endstations.
Last letter in dsl/dsr means "left" or "right" if you look from the ring towards the endstation.
Click on SMU_2 in the main menu and make sure that the green circle is in front of dsl (1^2):
If it is not, then make sure that:
your neighbors at 1-Cubed finished their work
the beamshutter is closed
After that press the square button in front of "dsl" to get the light and wait until "dsl" indicator turns green.
After finishing your shift it is a good tone to switch the beam to your neighbors, this way you tell them that you finished and they will not need to worry about step #1.
Open the blue panel by pressing UE112-PGM2 button in the main menu, insert the required value of photon energy in the field Energy (eV). While inserting values cursor should remain inside the field. Press enter. After that monochromator will be set to the specified photon energy and undulator gap will be adjusted according to the loaded ID table (ID=Insertion Device).
ID tables are different for each light polarization! Make sure that you are using the right one (see section about light polarization for more details).
In the top left button you should see ID On, if ID is Off, then only monochromator will move resulting in a very low intensity.
If you see error "ID is local" please check this section.
After changing the photon energy beam will deflect from optimal trajectory and start hitting one of the beamline slits (one can see it on the top-right monitor). To fix this and recover full intensity of the beam go to SMU112_1 panel and press SMU/experts -> PGM2.
! Important !
Use only SMU112_1 that is closer to the ring! Not SMU112_2! If you moved wrong SMU, it is not critical for operation, but don't forget to tell the beamline scientist, then correct parameters can be recovered.
The following panel will appear:
Use only the middle parameter (M3 Left Rx) and change the value using + or - until you reach maximum photoemission intensity.
Use step 1000 for large changes in photon energy and 200 for fine tuning.
Actual value of Rx is shown on the left (in the picture it is 203300, not 191200), you can write it down for you favourite energies. Value in the box is just what you entered last time.
Press button "!" on the right from "Select ID table" in the blue panel. After some time the following panel should appear:
Choose one of the options in the drop-down menu "Select Light:" and press button "Do it!". After it says "Done!" go to blue monochromator panel, click inside the energy field and press enter (even if you did not change the photon energy value). This will start movement of monochromator and undulator with respect to the new table. Movement can take some time, wait until blue panel shows "Ready".
To check the actual status of undulator press the big button UE112 on the very left of the main menu. This panel is mainly useful for troubleshooting. First of all, "ID control:" should be remote. Sometimes after machine group restores the beam they need to open undulator gaps and they control IDs "locally", i.e. from the control room. After the beamshutters are open again, the "ID control:" may remain in "local" status, then you must change it to "remote" using this panel.
You can also directly check the gap value and the values of undulator shifts that are used to control light polarization (linear horizontal polarization should correspond to shifts of 0).
Rules of thumb about the directions: If you increase , the Rx value should be reduced and vice-versa. If you see the beam to the right from the slit, you need to increase Rx and vice-versa.
Tip: circular polarisation can be used to suppress the second harmonic signal (e.g. if you see core levels in the valence band or above the Fermi level, they are most probably coming from the synchrotron radiation with doubled energy ).
