An electron beam catcher for velocity modulated electron tubes which is formed as a two multi-stage collector comprising a plurality of catcher electrodes 1 and 2 surrounding the electron beam and mounted so that one follows the other in the direction of the electron beam axis and the catcher electrodes are electrically insulated from each other and are surrounded by a metallic outer envelope 3. A plurality of semicylindrical insulating parts 4 and 4' extended in the axial direction and are mounted between the catcher electrodes 1 and 2 and the outer metallic cover or vacuum envelope 3 which is heated to cause it to expand and is then shrunk onto the insulator parts 4 and 4' such that the oblong insulator parts 4 and 4' are pressed against the catcher electrodes 1 and 2 and are tightly held by the metallic outer vacuum envelope 3. The electron catcher 15 particularly useful in high powered travelling wave tubes.