Axis of the polar rotation is generally not passing through the sample surface. Because of this during the rotation the sample will move away from the focus of the analyzer (and the beam). This can strongly affect polar maps measured in large angular range, especially for small samples.

A way to cope with this problem is to adjust the sample's X/Y position for each new polar angle. To find the correct X,Y for each angle you can first optimize sample position manually for a set of polar angles inside the range of interest and then use them as a reference with interpolation in between (see ).

Theoretically it is possible to do good manual optimization only for one point (in the middle of region of interest) and calculate all other X/Y positions based on this point and the position of polar rotation axis.

To do that find the following icon on the desktop:

You can also find the file . This will create polar corrections for +-40 degrees from the point with good optimization and with step of 2 degrees. Press "Save".

Finally in MultiAx Polar corrections tab press Load File button and select the file "XY-correction" (it should be on top if files are sorted by date).

Analyzer slit

Before starting the measurement select a proper analyzer slit (black knob on the analyzer).

Narrow slit: + better k-resolution perpendicular to the slit - more difficult to focus and less counts. Curved slit: + flat Fermi level and constant energy surfaces - makes a curved cut in k-space Straight slit: + makes a straight cut in k-space - curved Fermi level (energies need to be corrected programmatically).

In case of problems with communication between the MultiAx program and the manipulator it can happen that calibration of the axes is not correct anymore. It may happen, for example, if you see that coordinate values in the MultiAx window are changing while motors are not actually moving.

To recalibrate one axis go to Settings tab and type in the password (provided by the beamline scientist), then press the Unlock button.

Select the axis and press begin calibration. Set the actual position as determined from the rulers on the motors or visually from the camera image.

• Move x and y to 4 mm on the rulers --> recalibrate x=0, y=0; Alternatively, read the values on the rulers (arrows mark positiove direction, 4mm mark is 0)

• Recalibrate z according to the value on the z ruler;

• Use tilt to position back side of the manipulator head vertically --> recalibrate tilt=0;

• Align the 2 vertical wires (left camera screen) by polar (correct for backlash) --> polar=0;

• Rotate the sample towards the camera by polar and use azimuthal rotation to make sample holder top edge horizontal (correct for backlash) --> azimuth=0.

Press confirm.

After this axis coordinate will be saved and calibration panel will be locked automatically.

After recalibration your saved positions will not be very precise anymore because of the errors in determination of the positions. Center of rotation for polar map XY correctons may be also slightly shifted.

Starting

Find the SES icon in the taskbar:

Allow windows to run the program.

Press Test connection, you should see a reply in the MultiAx log panel (at the bottom of the window). Press OK.

Again press Test connection and see the reply. If reply did not appear, there is a communication error, please contact beamline scientist for further instructions. Press OK.

SES window should appear.

Setting up

Go to Run - Setup menu. Specify region of measurements parameters.

Known bugs and errors in SES

Current bugs

A map will always start with a number of regions twice as big as the number of points. This causes an error message in the end of the map. When it asks "Discard and proceed?" press No.

Setting up a mapping region

P-axis should be selected as major, otherwise polar angle values will not be written in the datafile.

Scale fields should be identical to P-axis fields, otherwise polar angle values in the datafile will be wrong.

Map doesn't start

Problem: cannot start a map because SES immediately shows an error. If this cannot be cured by restarting SES, then measure one single spectrum and let it finish (not a "Manipulator scan" region, but "Normal"). After that it should be possible to measure a map again.

Bugs that didn't appear for a long time (and hopefully will not anymore)

Map is not saved

Sometimes after mapping you can get not a usual "Out of bounds", but another error about some DLL with "AddData" in it's name. In this case file is probably not saved. To fix this issue restart the program.

Wrong number of steps when starting a map

If number of polar angle steps was changed or a new mapping region was created, map has to be started, stopped and restarted again. Otherwise it will measure a wrong number of polar angles (see left bottom corner of the measurement window, for map with N steps it should show "1/N", if it shows e.g. "1/1" - it will stop after 1 sweep)

Access violation

From time to time the following or similar error message may appear:

Access violation at address 004ED730 in module 'SES.exe'. Read of address 06D7C5EC.

Usually it can be fixed by stopping the experiment and restarting SES program.

If it doesn't help (outdated)

While SES is closed try to unplug and plug again the black USB cable from the USB-RS422 adapter with yellow sticker that goes to measurement PC (you can find it behind the monitors, see photo below).

No contact with 7048 processor

Error "12001: no contact with 7048 processor at adress 0" Trying to shutdown SES programm causes it to freeze.

Solution: try to unplug and plug back the cable from USB-RS422 adapter (see above).

Starting the program

...

Moving between Preparation and Analysis chambers

There are two special positions stored in the "Positions" tab: TransferPrep and TransferAn, these are standard positions in Preparation and Analysis chambers, respectively. Automatic movement of manipulator between these two positions is considered safe.

To move from Preparation to Analysis chamber first move to TransferPrep, then after all axis have moved, move to TransferAn position. And vice-versa for opposite direction.

Polar corrections

Troubleshooting

Sudden change in all coordinates, manipulator starts to move by itself

If this happens, first thing to do is to press the emergency stop red button. It will cut the power from motors.

Then call the beamline scientist to help. Solution of this problem is currently not available for users.

In our beamline the beam moves away from the optimal path when the photon energy is changed. To compensate for this effect one can move one of the SMU mirrors by hand to bring the beam back.

Now there is an automated procedure that can control the beam position and keep it optimal.

To start it (for example after PC was rebooted) you will need to do the following:

1. Open powershell (or open a new tab in the existing one, e.g. the one used for beamline control).

2. Type in ssh melmak2 and press enter to execute (this is to connect to the Raspberry Pi)

3. Execute caMonitor vxi-11/psdutil/pvNames.txt (to monitor mono status)

4. Open another tab in powershell and also execute ssh melmak2

5. Execute psdControl bruecke13,1,4 lcmAB (this will start the main script that does the adjustment)

6. If you want to stop it, type in q and press Enter. The error message "Error opening /dev/ttyUSB0: No such file or directory" will appear, this is normal.

General info about how it works

//maybe a figure with explanation will help

There is a special device inside the beamline at the position of the slit that is monitored by a camera. Beam hits both plates and one can measure photocurrent from each of them, this is done by two Keithley ampermeters located on top of the rack of 1^3 beamline (see photo below). These two currents change monotonously as a function of beam position (one increases and another one decreases) and the optimal position is calibrated to be at the point where the currents are equal. To avoid electrons excited from one plate to reach the other one (which would lead to erroneous measurements) there is a bias voltage of 100 V applied between the plates.

The current signals from Keithleys are passed to a Raspberry Pi which (if current is large enough) will move the SMU M3 in decreasing steps until the currents are equal.

There are two beamline branches using the same technique, and at the moment (May 2025) users need to switch a pair of cables manually to change the controlled branch from 1-Squared to 1-Cubed. One pair of cables is labeled with roman numerals (I, II) and another with arabic (1, 2). Arabic one is for 1-squared, roman — for 1-cubed. They should go to corresponding Keithleys (currently 1 is on the left-bottom, 2 is on the left-top, but if the configuration has changed you can just swap 1<->I and 2<->II cables). Always switch both cables and make sure that the connected cables belong to the same pair.

Troubleshooting

If the terminal was closed without quitting the beam control procedure correctly by q it could happen that the procedure will not do anything next time. In this case try to quit the procedure with q, then switch two Keithley devices off and on again, then start the procedure again.

After restarting Keithleys you will need to press OPER button on the Keithley #2, it will activate bias voltage of 100V between the plates. You should see an LED switching on and "Vsource:+100.000V" on the screen. If it shows zero, enter 100 manually using the arrows under "voltage source".

In the worst case, you can switch it off and .

The screws on the manipulator head (left photo) can be tightened to provide a better thermal contact while cooling for the samples that require lowest possible temperatures. Vacuum screwdriver is located in the Preparation Chamber, close to the heater (right photo).

To tighten the screws:

• Move manipulator to preparation chamber;

• Close the valve between the chambers;

• Go to a saved position "screwdriver" or rotate manually tilt and polar angles;

• Do not apply force! Just screw until the end without making it too tight;

• Return to "Transfer_PREP" position.

To take your sample out later you will need to loosen the screws by ca. 2 full turns.

First you need to make sure that auto beam-position control is working.

To perform an automated photon energy scan:

• In the MultiAx window open tab "Mono corrections"

• Tick activate

• In the CommPort | MONO block check that COM2 is selected and click Connect

• Check the current photon energy, the value should appear in the yellow box (Position [eV])

• In the SES window create a new CIS region, press Edit, set start/fin values of hv and step

Before starting a scan make a test run and make sure that the intensities are reasonable at all photon energies in the range.

1. Open the valve between Preparation and Analysis chambers;

2. Bring sample into measurement position in the Analysis chamber;

3. Make sure that beam is not used and beamshutter is closed;

4. Take the beam using ;

5. Switch on the ;

6. Set , , [width of apertures (optional)];

7. Check that suitable and are being used;

8. (data types, folder, sample name, etc.);

9. Switch on analyzer electronics by tumbler and open the beamline valves (starting from Experiment);

10. Open in the SES menu "Calibration" -> "Voltages" and set kinetic energy where you expect to see the bands;

11. Find signal from the sample using joystick and camera images. Sticker roughly marks position of the beam (camera image under the sticker should be in focus).

12. Fine tune the position using "Manual/Steps" or "Virtual axes" tabs. Y direction is along the beam (use for focusing).

13. Have a lot of nice measurements!

Beamline control software (BLC)

Taking the beam

Usually the window of beamline control panel is always open on the left monitor. If it was closed you can find it by pressing Start button and typing "BLC". Alternatively you can use the icon in the taskbar:

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:

1. your neighbors at PGM1 finished their work

2. 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.

SMU_2 switches beam between 1-Squared (dsl) and 1-Cubed (dsr) endstations.

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:

1. your neighbors at 1-Cubed finished their work

2. 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.

Changing photon energy

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).

Manually adjusting SMU for different photon energies (now it's done !)

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). Therefore beam position has to be adjusted for each photon energy. This procedure has been automated (see details ).

If you still need to fix this manually, go to SMU112_1 panel and press SMU/experts -> PGM2.

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. Please refer to the dedicated camera image of the horizontal apertures for guidance. Both apertures are covered with phosphorus thus UV radiation is visible. In the adjusted position the 90% of the beam should come through the gap between the apertures and only some shoulders are visible on the phosphorus.

Changing light polarization

In the blue monochromator panel press button "Monochromator experts" (top-left corner). In the pop-up menu select "Undulator". After some time a panel with a graph will appear, press "Related panels" in the top-left, in the pop-up menu press "Select Table".

Press the button in the right-bottom and select one of the four tables (Linear Horizontal, Linear Vertical, Elliptic +/-). Now the table is selected, but undulator and monochromator did not move yet!

Go again to the blue monochromator panel, click inside the energy field and press enter (even if you did not change the photon energy value). This will start the movement of monochromator and undulator with respect to the new table. Movement can take some time, wait until blue panel shows "Ready".

Controlling undulator status

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, in linear vertical parallel shift is 56 mm).

1. Check that helium line is deep inside the dewar, ca. 5 cm above the bottom.

2. Check that Helium pump is running (see panel inside the frame from the side of the load lock):

3. Check that black valve below the frame is open:

4. Make sure that helium recovery line is connected to a He return port on the wall-panel.

5. Use ladder and open the needle valve 1 full turn. Rotate counter clockwise if you look from below.

6. Wait until temperature reading starts to steadily go down by 0.01 K. If this doesn't happen in 10 minutes - it is likely that there is a problem (*).

7. When sample temperature reaches ca. 40K start closing needle valve in small steps and wait for the temperature to stabilize. Try to close as much as possible to reduce helium consumption, but don't let temperature to go up.

8. The lowest sample temperature reading is currently ~26 K (condition on Jan 2025).

Dynamics of manipulator cooling

Troubleshooting:

(*) As a first step try to disconnect helium recovery line from the wall (see Fig. 1) and check if there is a flow of gas coming out of it.

1. Make sure that Contol A LED is on (the coldfinger temperature will be used as a reference).

2. On the Lakeshore TC press Setpoint button (6).

3. Dial in the desired temperature for coldfinger (A)*. Sample temperature will be ~10 deg higher.

4. Press Enter.

5. Press Heater Range button and select power. Start with low, if it is not enough - try medium.

6. Press Enter.

Find below an approximate table of correspondence between A and B temperatures.