CONTINUOUS CRYOSORPTION VACCUM PUMPING FOR FUSION APPLICA- TIONS

FUSION ENERGY POWER REACTORS WILL REQUIRE HIGH SPEED VACUUM PUMPS TO EXHAUST REACTION PRODUCTS FROM THE PLASMA. CRYOGENIC PUMPS, WHICH FREEZE GASES ON A LOW TEMPERATURE SURFACE, ARE POTENTIALLY VERY ATTRACTIVE FOR THIS TASK. HOWEVER, THEY MUST BE REMOVED PERIODICALLY FROM SERVICE TO BE REGENERATED (DEFROSTED), OTHERWISE THEY EITHER SATURATE OR ACQUIRE AN UNACCEPTABLY HIGH INVENTORY OF RADIOACTIVE TRITIUM. THE DEVELOPMENT EFFORT IN THIS PROJECT WILL SOLVE THIS PROBLEM WITH A PUMP BASED ON THE SNAIL HIGH THROUGHPUT CONTINUOUS CRYOPUMP, WHICH REGENERATES THE CRYOPUMPING SURFACES CONTINUOUSLY DURING NORMAL OPERATION WITH A SPECIALHEAD THAT MOVES OVER AND CLEANS THE FROZEN GASES FROM THE CRYOPUMPING SURFACES. THE RESEARCH WILL EXTEND THE SNAIL CONCEPT TO THE CRYOSORPTION PROCESS. THIS WILL PRODUCE TWO SIGNIFICANT PRACTICAL ADVANTAGES OVER THE CRYOCONDENSATION PUMP. FIRST IS THE ABILITY TO CONTINUOUSLY PUMP HELIUM, THEREACTION PRODUCT OF THE BASIC FUSION PROCESS. SECOND IS THEABILITY TO PUMP BOTH HELIUM AND THE HYDROGEN ISOTOPES AT MUCH HIGHER TEMPERATURES, THEREBY ELIMINATING THE NEED TO USE LIQUID HELIUM AS A REFRIGERANT. THE PHASE I EFFORT WILLESTABLISH THE TECHNICAL FEASIBILITY OF SUCH A PUMP. TECHNIQUES OF FABRICATING A SMOOTH COCONUT CHARCOAL SURFACE WILL BE DEVELOPED, AND THE PUMPING AND REGENERATION PROPERTIES OF SAMPLE SUBSTRATES WILL BE MEASURED. ENCOURAGING RESULTS WILL LEAD TO A PHASE II EFFORT TO BUILD ONE OR MORE CONTINUOUS CRYOSORPTION PUMPS THAT COULD BE TESTED AT A DOE TRITIUM FACILITY.