Diffusion pump cold trap

Claim 1

IN AN ULTRAHIGH VACUUM PUMPING SYSTEM COMPRISING A VERTICALLY ARRANGED TUBULAR DIFFUSION PUMP WITH ITS INLET END CONNECTED TO A VACUUM CHAMBER VIA A TUBULAR COLD TRAP COAXIALLY ALIGNED WITH AND MOUNTED OVER THE DIF FUSION PUMP IN END-TO-END RELATION HEREWITH AND MEANS FOR EFFECTING A ROUGH REDUCTION IN BACKSTEAMING FROM THE DIFFUSION PUMP AN IMPROVED COLD TRAP COMPRISING A VERTICALLY EXTENDING TUBULAR WALL, A BAFFLE ASSEMBLY OF RADIALLY SPACED APART CONCENTRIC ANNULAR CHEVRON BAFFLES INCLUDING AN OUTERMOST CHEVRON BAFFLE AND INNERMOST CHEVRON BAFFLE LOCATED SUBSTANTIALLY IN A HORIZONTAL PLANE, SAID CHEVRON BAFFLES BEING INCLINED WITH RESPECT TO THE VERTICAL AXIS OF THE COLD TRAP AND SAID HORIZONTAL PLANE TO DEFINE AT LEAST ONE ANNULAR GAS CONDUCTANCE PATH BETWEEN ADJACENT CHEVRON BAFFLES, SAID GAS CONDUCTANCE PATH BEING OPTICALLY DENSE WITH RESPECT TO THE INLET OF THE DIFFUSION PUMP, SAID BAFFLE ASSEMBLY FURTHER COMPRISING A CENTRAL HOLLOW SHELL LOCATED SUBSTANTIALLY IN SAID HORIZONTAL PLANE AND ALONG THE AXIS OF THE TRAP SPACED FROM AND ENCOMPASSED BY SAID INNERMOST CHEVRON BAFFLE SO THAT IT IS SURROUNDED BY SAID ANNULAR CHEVRON BAFFLES, THE INNERMOST CHEVRON BAFFLE AND SHELL BEING CONSTRUCTED AND ARRANGED TO DEFINE THEREBETWEEN AN ANNULAR GAS CONDUCTANCE PATH WHICH IS OPTICALLY DENSE WITH RESPECT TO THE INLET OF THE DIFFUSION PUMP, RIB MEANS CONSTRUCTED AND ARRANGED WITHIN SAID TRAP FOR TRANSFERRING HEAT BY CONDUCTION BETWEEN SAID CHEVRONS AND SAID SHELL, MEANS FOR CONDUCTING CRYOGENIC FLUID TO AND FROM THE INTERIOR OF SAID SHELL, THE COLD TRAP FURTHER COMPRISING AN ANNULAR SUPPORTING DISK ASSEMBLY PHYSICALLY UNITED AT ALL POINTS OF ITS PERIPHERY TO AND EXTENDING SUBSTANTIALLY HORIZONTALLY FROM THE TUBULAR VERTICALLY EXTENDING WALL OF SAID COLD TRAP TO THE SAID BAFFLE ASSEMBLY TO SUPPORT THE BAFFLE ASSEMBLY FROM THE WALL, THE DISK ASSEMBLY CONSISTING OF INNER AND OUTER ANNULAR DISK ARRANGED HORIZONTALLY AND OVERLAPPING EACH OTHER WITH THE OUTER DISK UNITED AT ALL POINTS OF ITS OUTER PERIPHERY TO THE VERTICALLY EXTENDING WALL OF SAID TRAP AND THE INNER DISK UNITED TO THE OUTERMOST EXTENDING BAFFLE AT ALL POINTS OF THE INNER PERIPHERY OF THE INNER DISK TO DEFINE A COMPLETE ANNULAR SEAL AT THE JUNCTION OF SAID INNER DISK AND OUTERMOST CHEVRON BAFFLE, AND MEANS CONSTRUCTED AND ARRANGED WITHIN SAID COLD TRAP FOR CLAMPING SAID DISK TOGETHER AT THEIR OVERLAPPING PORTIONS SO THAT THE SUPPORTING DISK ASSEMBLY PRESENT AN ANNULAR IMPENETRABLE BARRIER SO THAT FLUID FLOW THROUGH THE COLD TRAP IS CONFINED TO SAID ANNULAR GAS CONDUCTANCE PATHS.