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 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:

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).

Adjusting SMU for different photon energies (now it's done automatically)

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 here).

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).

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).

We usually start with 400.

Beamline exit slit

Beamline (BL) exit slit vertical width is controlled manually with a knob behind the electronics rack.

With a smaller slit you improve energy resolution, but get less counts.

Plateau area (~140um) is a good starting point.

Beamline resolution for a given BL exit slit and photon energy can be estimated using an Igor script provided below (beamline parameters correspond to 1^2):

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).

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.

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.

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.

Mounting samples

Samples should be attached to the sample holder in a way that guarantees electric connection between sample surface and the sample holder, e.g. (depending on the sample type): with conductive glue, conductive scotch tape, spot welding of pieces of metallic foil, mechanically with screws and nuts, etc.

Sample holders: Omicron flag-type (molybdenum, copper, for some samples stainless steel is also OK, but not recommended).

Standard conductive silver glue: EPO-TEK H21D. Mix by weight 10 A : 1 B, recommended cure 150$^{\circ}$C / 1 hour (see more details).

Sample holders of several types and mounting options described above are generally available directly at the beamline. If you want to prepare your samples in advance, please check the following.

It is recommended to use sample holders with "ears" (see Fig. 1 "ears" are protrusions on the sides at the top edge of the sample holder). Without them sample holders will fall through the sample positions in the sample magazine under the heater. Except for this limitation, it is still possible to use sample holders without "ears", there is no fall-through problem neither in the load-lock nor in the manipulator.

Areas on the sides of the sample holder should remain clear, area available for sample mounting is shown with a red rectangle in Fig. 1. The sample itself and all holding/fixing components (e.g. glue, foils, screws etc.) have to be within this area.

Red cross marks ideal sample position. Thickness of the plate d is also very important (0.95 mm <= d <=1.05 mm).

For annealing at temperatures above 800C one should use high-temperature heating stage, in this case sample holder should have additional holes on the edges (red circles in the Fig. 1).

After all the modifications, especially if holes were drilled or screws used for sample mounting, check the back side of the sample holder. It should remain flat, nothing should stick out of it.

To avoid dropping top posts in the analysis chamber use a short piece of thin conductive wire and glue (or fix) its one side to the holder and another to the top post.

Available sample positions

Load-lock has a passive magazine with 3 sample slots mounted on a magnetic transfer rod. It can simultaneously accommodate up to: 2 samples with long (up to 10 mm) top-post OR 1 sample with long top post (10 mm) and 2 samples with short top-posts (5 mm)

There's a sample magazine for 3 sample slots in the preparation chamber. You can store there only sample holders with "ears". Magazine is mounted at certain angle, in order to fit the pitch angle of the wobble stick, and sample without notches will simply fall through.

Liquid Helium cooling

If your experiment requires low temperatures, don't forget to order enough liquid helium (LHe) for the beamtime at least 2 weeks in advance. Consult your beamline scientist and order via lhe-order@helmholtz-berlin.de.

1. Close all valves connected to the turbo pump: to exchangeable ports, to gas line and to load lock.

2. Make sure that the valve between load lock and preparation chamber is fully closed.

3. Stop turbo pump by pressing on-off button. Leave the prepump (membrane pump) running.

4. Close the valve between the turbo pump and load lock (VLL).

5. Check the pressure of N2 bottle inside the cabinet. The pressure of should be positive and non-zero (*).

6. Loosen the screw on the load lock door. Vent load lock by opening the valve, at some point door should open by itself. Leave the valve open to keep some gas flow.

7. Insert your samples in the load lock transfer rod (using e.g. long pliers). Rotate samples hook-up!

8. Close the valve properly.

9. Make sure the viton ring on the load lock door is clean and then close it.

10. Check that turbo pump has stopped completely. Slowly open the valve between pump and load lock. Air should be quickly pumped by the working membrane pump.

11. Wait for pressure to reach 5 mbar (**), and then start turbo pump.

12. Wait for pressure to reach at leastmbar (usually after ~60 minutes).

13. Close the VLL, and open the valve to the preparation chamber.

14. Check that nothing is on the way of the load lock’s rod, and then move the rod to the chamber.

15. Transfer your sample to the chamber using the , retract the rod, and close the valve between chamber and load lock.

16. If you want later to remove your sample from the chamber, then do not forget to open the VLL, to leave the load lock pumping.

17. Check what else should be pumped and don't forget to re-open the respective valves that were closed at the step #1.

18. Enjoy the experiments!

Troubleshooting:

* If pressure in bottle is 0 or negative.

Check that the valve on top of the gas bottle is open. If nothing helps and user support is out of reach, you can close the valve and vent load lock to air by opening the door by force (e.g. using a screwdriver).

** If pressure does not reach 5 mbar after few minutes, check that the door and valve are properly closed.

1. Open the valve between Preparation and Analysis chambers;

2. 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!

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 MultiAx polar corrections tab).

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 here. 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).

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, 2 is on the top-right, but you can just swap 1<->I and 2<->II cables if the configuration has changed). 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.

In the worst case, you can switch it off and correct the beam position manually.

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.

After manipulator went crazy

! Press red button immediately !

1. Close connection in MultiAx (tab Settings)

2. Manipulator -> OFF (button on the back panel, next to LL vacuum gauge)

3. Release the red button

4. Wait 30 seconds

5. Manipulator -> ON

6. Watchdog -> OFF. You will need admin password for this.

7. Open connection in MultiAx

8. Recalibrate axis

9. Watchdog -> ON.

Top-post: How to connect it to the sample holder Scotch-tape: How to prepare a tape with a wire

Cleaving in the analysis chamber

For sensitive samples it is preferrable to cleave in the analysis chamber. There is a wobble-stick without a clamp from the side of the load-lock. Use a saved position called "Cleave". It should first move sample away from analyzer lens, then rotate it to -60 deg polar angle. Check in the camera that manipulator doesn't hit the lens! In this position it should be possible to cleave sample with the wobble-stick. After cleave use saved position "After cleave", it will first rotate polar back and then move x,y.

1. ❗ DANGER: Close the valve between the two chambers and make sure that it is closed.

2. Sample can be sputtered either in the manipulator or in the low-temperature heater. Set the sample in the sputtering position by placing the manipulator/heater in the center of the chamber, usually surface should be at 45° relative to the ion gun.

3. Check that there is a gas bottle with argon connected to a leak valve that goes into the ion gun. Before inserting Ar, make sure that gas line has been flushed several times, in order to prevent oxygen contamination on sample surface. See the checklist for flushing the gas line.

4. Insert Ar by slowly opening the leak valve ($p=1\times10^{-5}$ mbar).

5. Switch on the power supply (SPECS IQE-11A, see photo below), check that the Energy knob is at 0 keV and set Mode knob to Operate. Check that the error LED "Filament fail" on the left is not on.

6. Slowly increase the electron energy to the required value (up to 3 keV) for the sputtering. Check that the LED for “HV Fail” is not on.

7. Finally, set the emission current knob to 10 mA.

8. After the sputtering cycle is finished repeat the steps 4-6 in reverse order: reduce Energy to 0 keV, put Mode to Stand by and close the leak valve.

TROUBLESHOOTING (???):

If it is not possible to raise the energy above 0.6 keV in the Sputtering Power Controller, check if the Extractor pin is grounded (towards external shield of the ion gun). It should not be grounded! If a finite resistance is present, let some current flow through this pin and ground until it is again isolated. ASK BEAMLINE SCIENTST FOR ASSISTANCE!

1. Switch off analyzer electronics and close the beamline valves (starting from Beamshutter). For a short break (e.g. while changing samples) it is enough to close experimental valve and beamshutter;

2. ;

3. Close valve between the chambers;

4. Close the needle valve of liquid helium transfer line;

5. Open the valve on the helium dewar to helium recovery line (or connect it);

6. Stop helium pump ("FP Helium" button on the panel at the back side of 1^2 frame);

If you are leaving:

1. Remove all the unnecessary marks on the screens

2. Remove sample names from the magnets on the wall

3. Remove files from desktop to your User folder

4. ...

...

The most general information about the station can be obtained by the following links:

Beamline flux(hv) dependence

Data is available as Igor waves (fluxw vs fluxe):

Old calculated beamline flux(hv) dependence can be found here:

Focal spot measurement:

These pages are accessible only from inside the HZB network.

Optical scheme

1. Check that both LEED cables are connected, and make sure that LEED has been degassed.

2. Make sure that LEED is retracted and there is nothing in the way, then move sample to a saved LEED position (if available). Insert LEED while looking inside the chamber.

3. Open the LEED shutter gently, and fix it by turning the screw on the shutter handle.

4. Cover all the windows of the prep chamber with aluminum foil and cover the outer LEED window with a black cap (it has a small hole in the middle for eye or camera, see the picture below). Additionally one can switch off the vacuum gauge in the prep chamber (top AML controller).

5. Switch on the LEED power supply (SPECS). Press down the Cathode knob and rotate clockwise until it clicks. Set cathode current to 2.4 A.

6. Slowly turn the Screen knob to the operating voltage (6 kV).

7. Start Camera (see below). Roughly find sample position. Adjust the offsets of L1 and L2 lenses if needed until you see sharp LEED pattern.

8. Set the desired electron beam energy with Energy knob.

9. When you finish reduce the Screen HV to 0V and reduce the filament current to 0 (until it clicks). Switch off the power switch.

Using camera to capture LEED images

To view and save LEED images one can use 1. Pylon Viewer or 2. RHEED Igor procedure.

1. Pylon viewer (for fast view, not recommended for data acquisitions)

• Find Pylon Viewer in Start menu (Win button + "Pylon")

• Switch on camera acA1440-73gmNPE (Pay attention that the acA1440-73gm is the electron analyzer camera. If the SES software is running, the Pylon software produce the error message that the camera is used by another application. ) // here goes screenshot of the program with arrows showing the switch-on and camera button

• Use Analog control menu and optimize exposure using Gain to get optimal image quality.

• Press the button with camera to show live view image.

• Press icon with a floppy-disc to save last image to your folder.

//Insert screenshots with camera settings

2. RHEED Igor procedure

• Start new IGOR instance

• Select from the top menu in Igor tab RHEED and open RHEED panel

• In the popup menu select camera name : "Basler acA1440-73gmNPE#..."

• Press the green button to start live image view.

• Adjust camera Gain, Exposure time and Gamma to get optimal intensity and avoid overexposure

• Switch panel to Data Acquisition tab to record the image.

• Press "Record Image" button to start accumulating the signal. When desired statistics is achieve press "Stop recording" to save the image.

• The data are saved as: "root:packages:RHEEDPanel:RHEEDData"

• Modify data name as desired. By default program overwrites the wave if it exists. Keep track on changing the names to not loose the data.

• Save IGOR experiment and export images if needed.

...

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.

When you move anything in the chamber, it is a good rule to always look inside at the thing you are moving.

Be gentle and don't apply too much force. If you have to pull/push too hard - you are doing something wrong. If sample holder is not sliding into/out-of the position with minimal force, it means that most probably the angle is not perfect. Try to adjust manipulator/heater positon and repeat.

//photos of good and bad positioning of the sample

If sample got stuck and it looks like photo 2, try to push the hook from below with a flat side of the wobble-stick (method 1). If this helps to release the bottom front corner of the sample holder, you will be able to pull the sample out.

If this doesn't help, one can try to follow the procedure below:

1. Wait for sample to cool down. Check if you can pull it out (try method 1).

2. Try to reach high T quickly, e.g. put 3A (max T should be ca 650C).

3. While it's heating hold the hook and give it a short but strong pull every ca. 5 sec.

4. At some point sample will jump out, be careful not to drop it! Ideally movement should be short enough so that sample holder stays partially in the heater. Wobble-stick clamps can open! Try to pull not too strong and try to keep pull vector in the horizontal plane (small deviations to left and right could help, but don't move up and down).

Measurements

How to transfer between the chambers?

How to azimuth-rotate the sample based on the map?

How to connect to User data folder remotely to copy files? One has to be connected to local WiFi or cable network. Then a network drive \\x-meteor.usd.bessy.de\UserData\ (???) can be added.

Misc

Where to eat around BESSY? During the day: Fastest option is Saida falafel kiosk. Other popular places include University mensa, Bagel company, Esswirtschaft (german), Mr Wu (chinese) and several others (google maps). During the night: Immergrün works until 8 p.m.. You can also order from Lieferando directly to BESSY (some places are open until 23-24). After midnight you can go to S-bahn station Adlershof to get a döner at Ibo's kebap. Or use vending machine in the cafeteria (but it eats money sometimes!). There is a kitchen at cafeteria and another kitchen in the building 15.8 (close to workshop).

How to get a key from the user fridge? Ask user office. (?)

1^2 team Maxim Krivenkov Office + cellphone redirection: 12345 Private + WhatsApp/Telegram: +49 176 94911008

Andrei Varykhalov Office: 14888

Urgent support (disasters, shutter, external equipment, etc.)

Hallendienst Office: 12984 Organization (badges, guesthouse, etc.)

User office Office: 12931

Dimar Spectra

Icon of the program

A tool for modelling of XPS peak positions, can be found on the desktop of the measurement PC.

hv, list of elements and work function -> peak positions on kinetic energy scale.

Modeled "intensities" correspond to tabulated ionization cross-sections.

Click on one peak to show information.

Click on one peak, then on another one while holding Shift -> get energy distance.

To see lines of all possible elements, write "all" in the list of elements.

Temperature log

On the desktop of the right PC there is an Igor experiment called "T log v ... .pxp" that can plot temperatures A and B of the cold finger and sample in real-time.

BL energy resolution from hv and BL exit slit

Generate XY polar corrections file

You can generate XY polar corrections manually. To do this you need to know the coordinates of a one good spot on the sample and the coordinates of the center of manipulator rotation (one needs to calculate them once precisely and then they should not change until next dismounting or recalibration of manipulator). This functionality is included in the current version of MultiAx, but in certain cases Igor version can be useful. It saves generated file in the "saves" folder of MultiAx from where it can be loaded into MultiAx. More info can be found here.

Center of rotation for XY corrections from N points

• Make a precise manual XY correction, saving several snaps (minimum 2). Ideally use a small sample or some small feature that you can easily identify (e.g. corner of the sample). Mainly the polar range and precision of each snap influence the precision of the fitting result.

• Save snaps as an ._xy file.

• Use command LoadXY() to load table of (p,x,y) values from the ._xy file as waves (wp,wx,wy).

• Use command Calculate(wx,wy,wp)

The results of the fit will be printed in the command line and circle in the figure should be updated.

Links

Download the Igor procedure here (later can be a link to repository):

Extract everything in the same place, then load InclAll.ipf and compile it. We recommend to use a separate Igor experiment for maps and load this procedure first. After it is loaded, you can drag and drop the wave containing the map inside the experiment window. After the wave is loaded a three-panel interactive window should appear:

1. energy -vs- slit angle ("front-view");

2. energy -vs- polar angle ("side-view");

3. slit angle -vs- polar angle ("top-view")

In the top row of the panel there are boxes (with up-down arrows), the values in these boxes control the third coordinate for each corresponding panel.

Rotation of azimuth based on the map to orient the sample

Use cursors (Ctrl+i) and put them in "top-view" image to determine the high-symmetry direction that you want to be parallel to the slit. The following code will give you the angle of rotation.

Some often used features

1) Conversion to k-space:

From the Igor command line you can call function kWarp(w, Ek0, alpha) wave w // name of your map-wave (3D (phi, Ek, theta) wave) variable Ek0 // kinetic energy at which k-range boundaries are defined variable alpha // tilt angle in degrees You can put Ek0 equal to max. kinetic energy and alpha should be equal to the angular position of Г point along the slit. Normal emission is supposed to be at polar angle = 0, if it is not the case, you can shift it by changing the Start value of the polar angle axis of the map wave. The converted wave will have the same name as the original one, but with "kw" on the end, you can plot it using Macros -> "Create Slice Panel ..." -> select this wave.

2) Compressing maps measured in fixed mode:

Maps measured in fixed mode have very small step in energy, which makes it difficult to work with them. It is possible to "condense" such maps summing up the values in each N energy steps to one single point. This can be done from Igor command line with function condensefixed(wname, Nrows, Ncolumns, Nlayers) It will condense the wave corresponding number of times along three directions. Rows=angle along slit; Columns=kinetic energy; Layers=polar angle. Example: condensefixed(w001r,1,10,1) will condense wave w001r 10 times along energy axis while keeping two other directions intact. The Slice Panel with condensed wave should appear. The condensed wave will have the same name as the original one, but with "rdx" on the end.

3) Extracting slices in specific directions:

Press Ctrl+I when Slice Panel is in focus to show the cursors panel. Put A and B cursors in the first image to specify energy range that you are interested in (for example somewhere at the top and somewhere at the bottom to have full range). Right-click the cursors panel -> "Show cursors pair" -> "C D". Put C and D cursors in the third ("top-view") image to specify the cut direction. After that in Igor command line write ExtractCsrSlice() This should produce a window with spectrum extracted along C-D in energy range specified by A-B.

Deposition of sub-atomic layers of alkali metals provides a method of continuous charge doping of the sample surface. In certain cases it allows to reach otherwise unaccesible in photoemission electronic states above the Fermi level (but not too far above, usually ~0.1-0.3 eV).

There is a permanently installed evaporator of potassium from the side of the wobble-stick. Other alkali metals, such as Na, Li and Cs are also available, but their installation should be discussed with the beamline scientist in advance.

Usage:

There are two installed inside the evaporator, their common point is grounded. Evaporator feedthrough has 3 contact pins: one on top and two at the bottom. The top contact is not used! Lower two correspond to two dispensers (K1 and K2). You need to connect "+" cable of the power supply to one of the lower contacts and "-" cable to the ground (e.g. any screw on the chamber).

Standard current is 5.7 A, which corresponds to a rate of ca. 1 monolayer in 2-3 min. Exact rate can be monitored by placing close to the sample during deposition, this should be done very carefully to avoid collision!

Intro

Igor data files are called "waves". This is a quite universal format to store data that can be one-, two- or more-dimensional. The wave is more than just a multidimensional matrix with numbers, it also stores the units and dimensions for each axis, so for ARPES data you can operate directly in terms of energy and angle values instead of constantly referring to point numbers.

A lot of useful info can be found in Igor Help files.

Loading procedures

First open Igor Pro (64-bit), then drag and drop the procedure files (click and hold mouse button on the icon, then move it to the Igor window while keeping the mouse button pressed). In the procedure window press "Compile", if compilation process is successful, "Compile" button will become inactive. Then you can either fold procedure windows or press cross to close them and (when asked), select "Hide" (not "Kill"!).

Loading data

After you have all the necessary procedures, you can drag and drop waves into Igor window. Some of the waves may be automatically displayed.

Useful keyboard shortcuts

• Ctrl+I: brings graph cursors, you can use them to measure features' sizes in the image/graph. (First click on the window you want to work with)

• Ctrl+J: brings the command line panel

• Ctrl+B: brings data browser panel

• Ctrl+A: Reset image view to see the whole image (to reverse zooming in)

• Ctrl+D: duplicates a wave in the Data Browser (e.g. if you want to try to modify the wave, but keep the original as a backup)

Simple calculations

To calculate something you can use command print in the command line, e.g.:

Working with images:

• To zoom-in to a certain area: select it by drawing a rectangle with left mouse button, then right-click in this area and press "Expand". You can also use "Horiz Expand" ("Vert Expand"), then it will keep vertical (horizontal) scale without change.

• To select a different colormap: right-click on the image -> modify image. Recommended map is grays, however for posters and presentations with white background it is better to tick "Reverse colors". Other options to try are Mocha (reversed), CyanMagenta, Green, Mud, Terrain, etc. Play with it, but please use something with monotonous change in colors.

• To change image dynamic range: Top menu -> ImageProcs -> Image Range... Useful e.g. to highlight some weak features

• To take a line profile: Top menu -> ImageProcs -> Image Line Profiles... Select proper width, direction (Horizontal or Vertical) and position (one can drag blue line in the image by mouse to put it in the right place or change position value). Press "Checkpoint" to save the profile, it will appear in the Data Browser window on the left as a new 1D wave with "_Prof1" in the end of the name.

• To change axis labels and style: double click on the axis (cursor should look like a double-sided arrow). E.g. to rotate tick labels go to tab "Label Options" and then change label rotation

Fitting:

How to find the Fermi level (Quick fitting):

Create a line profile at the area where Fermi level can be seen well (without sharp bands crossing Ef). You can increase the width to get a smoother result. Use Ctrl+I and put cursor on your 1D graph to select the fitting area (only part between the cursors will be fitted). Go to Top menu -> Analysis -> Quick Fit -> Sigmoid (Sigmoid definition in Igor Pro is analogous to a Fermi-Dirac distribution function.) In the command line panel (Ctrl+J) you will see all the fitting parameters printed out. xhalf value is the position where sigmoid curve takes it half-maximum value, i.e. chemical potential at the given temperature (close to the Fermi level).

Multi-peak fitting:

Click in the window with 1D graph that you would like to fit to bring it in focus. Go to Top Menu -> Analysis -> Packages -> Multi-peak fitting Tick "From Target" to automatically select waves from the target graph. Press "Start Set". Then "Add or Edit peaks" to add peaks manually. You can select Gauss for peak type and draw peaks by mouse starting by clicking approximately at the apex of each peak. After all peaks are added (not necessarily very precise) press "Done" and then "Do Fit". You can see all the fitting parameters for each peak by pressing plus symbol next to the peak name.

Misc

If the Igor file with data analysis (so-called "experiment") was made on a large screen, then on a smaller screen some of the panels will be out of reach. You can bring them back by Top menu -> Windows -> Control -> Retrieve all windows.

Helpful procedures

It can be difficult to keep up with the stream of ARPES data coming from a synchrotron beamline. There are several useful procedures written in our department that can help, you can find them on the desktop of the right PC:

LoadLastWaveMenu, All IP rocedures, DimPages, ... .

We recommend to load all of them directly after creating a new Igor experiment and press compile.

LoadLastWaveMenu

Creates an additional menu that allows to select current experimental folder once and after that load and plot the last measured wave with one click. You can plot raw data, derivative or second derivative, also you can plot directly angle-averaged spectrum (useful for XPS measurements).

All IP Procedures

Old style Igor Image Processing procedures. This is required for LoadLastwavemenu to work.

DimPages

Creates an analog of browser tabs for Igor, you can have as many pages as you need to structure your data. Pages can be renamed and sorted.

Mapping

For analysis of ARPES maps we recommend to create a separate experiment file and load there DimPages and procedure files.

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