A magnetron includes a cathode and a vacuum envelope in which the cathode extends. The vacuum envelope includes a portion extending radially relative to the axis of the cathode. A pair of electrically conducting support arms for supporting the cathode are in electrical connection with cathode supply terminals. The support arms have free ends connected to the cathode by leads. A wall extends across an area of the radially-extending portion. The wall is positioned along the radially-extending portion nearer to an end of the radially-extending portion that is adjacent to the cathode than to an end that is remote from the cathode and the support arms are mounted in the wall.
1. A magnetron, comprising:
a cathode having an axis,
a vacuum envelope in which the cathode extends, the vacuum envelope including a portion extending radially relative to the axis of the cathode;
cathode supply terminals;
a pair of electrically conducting support arms for supporting the cathode and in electrical connection with the cathode supply terminals, the support arms having free ends connected to the cathode by leads; and
a wall extending across an area of the radially-extending portion, wherein the wall is positioned along the radially-extending portion nearer to an end of the radially-extending portion that is adjacent to the cathode than to an end that is remote from the cathode, and the support arms are mounted in the wall.
2. The magnetron as claimed in claim 1 , wherein each support arm has two parts secured together, one part being mounted in the wall and having a greater diameter than the other part which is connected to the cathode lead.
3. The magnetron as claimed in claim 2 , wherein the parts mounted in the wall comprise one of tungsten, molybdenum, copper, nickel, or alloys thereof.
4. The magnetron as claimed in claim 2 , wherein the parts connected to the cathode leads comprise one of tungsten, molybdenum, or alloys thereof.
5. The magnetron as claimed in claim 1 , wherein the wall is formed integrally with the part of the radially-extending portion that is remote from the cathode.
6. The magnetron as claimed in claim 5 , wherein the part of the radially-extending portion that is adjacent to the cathode is connected to the part remote from the cathode by sealing material.
7. The magnetron as claimed in claim 5 , wherein the wall has openings that receive the support arms, and a vacuum-tight seal is created by brazing to metallisation applied to the wall.
8. The magnetron as claimed in claim 7 , further including sleeves surrounding the support arms to reduce the electric field strength in the vicinity of the metallisation.
9. The magnetron as claimed in claim 8 , wherein the sleeves surrounding the support arms include flared regions.
10. The magnetron as claimed in claim 8 , wherein the sleeves surrounding the support arms comprise quarter wavelength RF chokes.
11. The magnetron as claimed in claim 1 , wherein the radially-extending portion of the vacuum envelope comprises ceramic material.
12. The magnetron as claimed in claim 1 , further comprising an anode having a profile with an interior, wherein the support arms terminate outside the profile of the interior of the anode.