Before floating the foils, it is recommended to cut of a few mm from the upper and lower edges of the foil, as this allows easier detachment of the foil from the small glass frame they are initially attached on. You require:

• A sharp razor blade
• A support pad (i. e., wood or plastic)
• A ruler, or a long, straight edge to cut along

1. Carefully take the foils out of the styrofoam casing (see Fig. 1). In any case DO NOT TOUCH the side of the frame with the carbon. Usually, the glass frames have a label (for instance "1C"), which is written on the glass side without the carbon, so you want to place the frame with the glass side on the support pad (compare Fig. 2).





2. Now place the ruler on the upper side of the foil and cut of a few mm (the less material is cut off, the less will float around in the water basin later and potentially catch the main foil, which could destroy it!) and repeat the procedure on the lower end of the foil. If the foil has evident tears on either of the long edges, you may want to cut along those sides as well. Otherwise, you can leave them as they are.

Before floating foils, be sure to be in an environment with minimal air movement (ideally a clean lab, but avoid areas with strong air circulation). The foils are extremely fragile, so never touch them or breath on them.

The setup as shown in Fig. 3 consists of:

• a big water basin on a steady table
• two smaller basins, which act as a flow regulator to slowly adjust the water level
• an adjustable stand to place one basin on a higher level
• a heavy cylinder (or something similar) to weight down one small basin which is placed inside of the large basin
• an elbow shaped piece to balance the glass frame in a 45° angle
• a small block to hold the elbow into place
• a plate, with one bend edge to hold the glass frame into place
• a razor blade and dish soap
• a pair of latchable tweezers/forceps to catch the foil
• a frame with Ni-mesh
• a carbon "foil" on glass

To float the foils follow these steps:

1. Place one of the small basins in the big water basin and the other basin on the adjustable stand so that it is on a higher level. Then mount the flow control under the table using a clamp (compare Fig. 4)



2. Fill the big basin, including the small basin with water up to the edge of the small basin. Fill the basin on the adjustable stand with water. Note, that while floating the foil, the upper basin, has to be refilled several times. Make sure to fill it up before the hose sucks air in. The upcoming air bubbles can cause the carbon foil to rip apart!
3. Place the plate across the small basin and place the elbow piece on the plate. Support the elbow with the block (compare Fig. 5 (top))



4. Place the foil in a 45° angle on the elbow. Be careful and make sure to place the glass side on the elbow and the foil side up!
5. Have a razor blade and detergent ready. The blade (with a very thin coat of detergent on its tip) can be used to gently move the foil (without touching it!) in a desired direction.
6. Make sure not to shake the table while the foil is in the water, again do not touch it, or breath on it!
7. Now you can start raising the water level very slowly ,so that the lower edge of the foil barely touches the water level. This will be enough to start detaching the foil. Give it some time and increase the water level further (again, very SLOWLY!). Watch out for pinholes, as the foil is likely to tear on those spots. Sometimes the foil becomes lose on one side but is stuck on the other. In that case, wait for several minutes. Eventually the foil will come off (compare Fig. 5, bottom). If not, there is the option to slowly lower the water level again and then raise the level again. However, be aware that this procedure can cause the foil to fold itself up, which likely destroys it.





8. Once you managed to float the complete foil (usually takes up to 20 - 30 min, depending on quality of the foil and experience), it will float on the water surface (compare Fig. 5)

1. Once the foil floats on the water surface, you have to carefully remove the glass plate, the elbow and the block from the basin, as you need space to catch the foil. Never make any sudden movements in the water. The foil tends to be drawn in the direction of objects on the water surface, unless, they have detergent on it. This step is very critical, and you're most likely to destroy the foil now if you're not careful.
2. Hold the MCP frame with the latchable tweezers in one corner in one hand and hold the razor blade dipped in detergent in the other hand so you can simultaneously direct the foil with it if required.
3. Very slowly bring the frame under the water surface (holding it 90° to the water surface, see Fig.6). You may need to "steer" the foil away, while doing this. Then position the upper edge of the frame in a 90° angle underneath on edge of the foil.



4. Slowly lift the frame (keep the 90° angle), while catching the foil. Once you caught it on the upper edge, it cannot go anywhere anymore and simply move (slowly!) the frame all the way up and you should have the entire foil (hopefully intact) on the mesh (compare Fig. 7). Note that foils with holes or tears on the outer part of the foil are still usable. Only holes in the middle of the foil, where one expects the beam spot are critical.
5. Start turning/rotating (very slowly, you do not want sudden air movements to destroy the surface!) the frame (along the edges) with the foil to remove the water.
6. After a few minutes, place the foil in a styrofoam casing (see Fig. 8), with one open side and let it dry for at least a day before you install it.

1. Make sure all voltages are off, and the MCPs are OUT of the beamline. Then follow the instructions to slowly vent the FSB (even if one foil is broken and needs to be replaced, the other might be intact) and remove the flange on the East side of the FSB (which one depends on which MCP foil is being replaced).
2. Wear gloves when reaching inside the FSB. To remove the MCP foil holder some experimenters prefer to move the foil into the OUT positions, others find it easier when the MCP foil is in the IN position. IN position is recommended here. The foil holder has two holes (one on the top right corner looking downstream, and one on the bottom left corner diagonally across from each other; see Fig.9 and 10) to attach the holder to the mirror assembly. Grab the holder at the handle and slightly lift the frame up before sliding it off the 2 screws that hold the frame in position. Be careful with the hole assembly, you don't want to accidetally destroy fragile mirror wires.









3. Take the holder to a clean working surface, and detach the plates on either side, held by 2 phillips head screws each (see Fig.10).
4. Carefully lift up the MCP frame with a small screw driver (only touching the frame, not the mesh) at one of the 4 corners, and place the frame in one of the styrofoam boxes.
5. Install the new MCP frame (The side with the carbon foil needs to face upwards, otherwise you destroy it) by carefully placing it into the indent. Reattach the plates. Now the holder + frame is ready to be installed again. Note, for MCP0 the holder has been designed differently (see Fig.11).
6. Slowly walk over to the FSB and reinstall the holder in the same orientation as before. It's a bit tricky, as it's really hard to see the holes or the mounting points at the assembly. It's probably wise to practise this without a foil first.
7. Once the holder is in securely in place, clean the O-ring surface, inspect and clean the O-ring + groove and reattach the flange, move foils to OUT position and follow the procedure for slow pump-down. It might take until the following day before the vaccum is good enough to start biasing the MCPs again.