1) Ensure that filament and HT are off (Ideally the night before)

2) Switch of the camera cooling and the camera (ideally the night before)

3) Move the lift stopper to the moving position. Screws can be removed by hand)

4) Vent the electron gun chamber by pushing the “Gun Air” button in Microscope Controller Panel. Button will light up green.

5) Wait 5 Minutes

6) Lift the gun by pushing the “Gun lift” button in the microscope controller panel. Button will light up green.

7) Move the stopper into the “rest” position

8) Cover the electron gun chamber with aluminium foil to prevent dust entering the chamber.

9) Make sure that the grounding rod is in contact with the Wehnelt cup. Important: Make sure that the Wehnelt is cool enough to touch.

10) Put on clean cotton or nylon gloves.

11) Detach the wehnelt cylinder by counterclockwise turning.

12) Pull down the Wehnelt.

13) Disassemble the Wehnelt by first removing the filament using the three Allen screws (see picture)

14) Remove the cap and the ring spring from the filament attaching stage

15) Clean the Wehnelt cap and especially the area of the small hole.

A) Use a small amount of cotton around a toothpick and wet it with a minimal amount of pure isopropanol. Dip the cotton in a very small amount of Aluminiumoxide.

B) Clean carefully the inside of the small Wehnelt cap hole. Important: Too much will damage the metal. Use it only in the rough cleaning stage!

C) Do the fine cleaning and polishing by having polish at the tip of the cotton. Make sure that the whole cap will be very shiny (aka clean). Note: This can take a few hours.

D) Finally remove any polish left on the cap by cleaning with pure isopropanol.

16) Insert a new filament in the filament attaching stage and screw it tight with the three Allen screws.

17) Reassemble the Wehnelt by putting the ring spring on the filament attaching stage and screw the cap in for 1-2 turns.

Image before the cap is added

18) Screw the cap until the tip of the filament is aligned with the hole on the cap.

19) Turn the cap back by 1 and 4/5th turns (max 2 turns)

20) Insert the Wehnelt back into the microscope.

21) Screw the cup back onto the Wehnelt.

22) Clean the O-ring in the lower electron gun chamber. No dust or dirt should be left. There should be some vacuum grease left on the ring.

23) Remove the lower screw of the lift stopper and move the gun to the left until it stops

24) Turn on the “Gun Lift” button in the microscope controller panel. Button will go dark. Hint: Make sure that the gun seals properly.

25) Turn on the “Gun Air” button in the microscope controller panel. Button will go dark.

26) The system should start to evacuate. Wait until all vacuums did recover.

27) Aligning the new tip [ADAM)