Cryopump with regenerative shield

Claim 1

IN A VACUUM PUMP OF THE TYPE INCLUDING AN OUTER HOUSING, THE HOUSING HAVING AN OPEN END, A HOLLOW SHIELD OF HIGH THERMAL CONDUCTIVITY MATERIAL MOUNTED WITHIN AND IN THERMAL ISOLATION FROM THE OUTER HOUSING, THE SHIELD HAVING AN OPEN END A FIRST SUPPLY OF CRYOGEN COUPLED TO REFRIGERATE THE SHIELD, COLD PLATE MEANS MOUNTED WITHIN AND THERMALLY ISOLATED FROM THE HOLLOW SHIELD, A SECOND SUPPLY OF CRYOGEN COUPLED TO REFRIGERATE THE COLD PLATE, THE CRYOGEN OF THE SECOND SUPPLY HAVING A LOWER BOILING POINT THAN THE CRYOGEN OF THE FIRST SUPPLY, AND THE COMBINATION THEREWITH OF: A BAFFLE ASSEMBLY HAVING A PLURALITY OF LOUVER PLATES MOUNTED IN ADJACENT PLANES AT PROGRESSIVE DISTANCES FROM THE COLD PLATE FOR BLOCKING RADIANT HEAT; A PLURALITY OF HEAT TRANSFER MEANS EACH CONNECTED TO AN INDIVIDUAL ONE OF SAID LOUVERS, EACH OF THE SAID HEAT TRANSFER MEANS BEING THERMALLY ISOLATED FROM THE SAID HEAT TRANSFER MEANS OF THE ADJACENT LOUVERS; AND A GAS TRANSFER MEANS CONNECTED TO VENT BOILED OFF CRYOGEN GAS OF THE SECOND CRYOGEN SUPPLY FROM THE VACUUM PUMP, SAID GAS TRANSFERMEANS BEING COUPLED TO TRANSFER AVAILABLE REFRIGERATION FROM THE CRYOGEN GAS TO THE LOUVERS IN A SERIAL SEQUENCE FROM THE INNER PLANE OF LOUVERS TO THE ADJACENT OUTER PLANE OF LOUVERS.