Penning type vacuum pumps

Claim 1

AN IMPROVED ELECTRICAL VACUUM GETTER PUMP OF THE TYPE PROVIDED WITH (A) AN ELECTRODE ASSEMBLY COMPRISING (1) TWO SUBSTANTIALLY PARALLEL SPACED CATHODES AND (2) AN ANODE OF GRID CONSTRUCTION DISPOSED BETWEEN SAID CATHODES, AND (B) MEANS FOR IMPRESSING A MAGNETIC FIELD ACROSS SAID ELECTRODE ASSEMBLY IN A DIRECTION SUBSTANTIALLY NORMAL TO THE CATHODE PLANES TO CAUSE ELECTRONS MOVING IN THE SPACE WITHIN SAID ASSEMBLY FOLLOW SPIRAL PATHS BETWEEN THE SAID CATHODES BEFORE BEING CAPTURED, THE IMPROVEMENT RESIDING IN THE FACT THAT (C) EACH OF SAID CATHODES HAS A SURFACE MADE UP OF AN ALTERNATE ARRAY OF RAISED AND DEPRESSED POLYGONAL SECTIONS JOINED BY SAID WALLS DISPOSED TO RECEIVE SPUTTERED MATERIAL FROM SAID DEPRESSED SECTION, THE AREA OF EACH RAISED AND DEPRESSED SECTION AND THE AREA OF EACH GRID APERTURE OF SAID ANODE ARE APPROXIAMTELY EQUAL, THE DISTANCE BETWEEN SAID DEPRESSED SECTIONS AND SAID RAISED SECTIONS MEASURED IN A DIRECTION AT RIGHT ANGLES TO THE CATHODE PLANES IS NOT LARGER THAN THE DISTANCE BETWEEN ADJACENT RAISED SECTIONS, AND SAID SIDE WALLS OF EACH SAID CATHODES ARE DISPOSED SUBSTANTIALLY OPPOSITE THE GRID OUTLINE OF SAID ANODE.