Wide band cryogenic ultra-high vacuum microwave absorber

DETAILED DESCRIPTION What is claimed is: 1.
A mode absorber for absorbing unwanted higher order modes of microwave energy from rectangular wave guides, comprising: an absorber having a leading end and a trailing end capable of absorbing unwanted higher order modes of microwave energy over a wide frequency range having a cross section area as measured transverse to the centerline of the wave guide in which it is to be mounted that varies from a very small area at the said leading end of said absorber to a maximum cross section area towards said trailing end of said absorber, and said absorber being shaped so said leading end is positioned in one corner of the rectangular wave guide and tapering downstream to said maximum cross section area with the center of said maximum cross section being located in the approximate vicinity of the longitudinal center line of the wave guide in which the absorber will be mounted.
2.
The mode absorber of claim 1, wherein the height of said absorber is less than the maximum width of the wave guide in which it is to be located.
3.
The mode absorber of claim 1, wherein said absorber is triangular in shape.
4.
The mode absorber of claim 1, wherein said absorber is a combination of first and second flat generally triangular tiles, and said first tile being a main absorber and said second tile being an absorber which supports said first absorber and both tiles being joined together in a manner that permits good heat conduction from said first tile to said second tile.
5.
The mode absorber of claim 4, wherein said first tile absorber has a knife-edge leading end.
6.
The mode absorber of claim 4, wherein said second tile is mounted in a thermal conducting manner on a high conductivity endpiece adapted to be attached to wave guide.
7.
The mode absorber of claim 6, wherein said endpiece has two cavities connected by a bridge with said second tile mounted on said bridge.
8.
The mode absorber of claim 6, wherein said second tile has an orifice through the tile; an elongated safety member positioned in said orifice with a substantial surrounding clearance and with ends protruding beyond said second tile; and mounting means for fastening said protruding ends to said endpiece