Cryopump with peripheral first and second stage arrays
In a cryopump, a primary cryopumping array having adsorbent and cooled by a second refrigerator stage extends along radiation shield sides. That array is shielded by a condensing cryopumping array that extends along the primary cryopumping array. The primary cryopumping array may be a cylinder with adsorbent on an inwardly facing surface, and the condensing cryopumping array may comprise an array of baffles having surfaces facing the frontal opening. A raised surface such as a conical surface at the base of the radiation shield redirects molecules received from the frontal opening toward the primary cryopumping array. The refrigerator cold finger may extend tangentially relative to the radiation shield or connect to the base of the radiation shield.
1. A cryopump comprising:
a cryogenic refrigerator comprising a cold stage and a colder stage;
a radiation shield having sides, a closed end, a frontal opening free of cryopumping surfaces opposite to the closed end, and a central volume free of cryopumping surfaces, the radiation shield being thermally coupled to and cooled by the cold stage;
a primary cryopumping array spaced from but close to and extending along the radiation shield sides, the primary cryopumping array supporting adsorbent material and being coupled to and cooled by the colder stage;
a condensing cryopumping array extending along the primary cryopumping array between the primary cryopumping array and the central volume so as to surround the central volume.
2. The cryopump as claimed in claim 1 wherein the primary cryopumping array is a cylinder having adsorbent on an inwardly facing surface.
3. The cryopump as claimed in claim 1 wherein the condensing cryopumping array comprises an array of baffles having surfaces facing the frontal opening.
4. The cryopump as claimed in claim 1 wherein the condensing cryopump array is in the path of all straight lines from the frontal opening of the radiation shield to the primary cryopumping array.
5. The cryopump as claimed in claim 1 wherein the radiation shield closed end comprises a raised surface that redirects molecules from the frontal opening toward the primary cryopumping array.
6. The cryopump as claimed in claim 5 wherein the raised surface rises to a point along the center axis of the radiation shield.
7. The cryopump as claimed in claim 5 wherein the raised surface is conical.
8. The cryopump as claimed in claim 1 having at least a 20% capture probability of hydrogen.
9. The cryopump as claimed in claim 1 wherein a radiation load to the primary cryopumping array is less than 3%.
10. The cryopump as claimed in claim 1 wherein a radiation load to the primary cryopumping array is less than 2%.
11. The cryopump as claimed in claim 1 wherein a radiation load to the primary cryopumping array is less than 1%.
12. The cryopump as claimed in claim 1 wherein the cryogenic refrigerator comprises a cold finger, having the cold stage and the colder stage, that extends tangentially relative to the radiation shield.
13. The cryopump as claimed in claim 1 wherein the radiation shield is thermally coupled to and cooled through a shield that is coupled to the cold stage and that surrounds the colder stage of the cryogenic refrigerator.
14. The cryopump as claimed in claim 1 wherein the cryogenic refrigerator comprises a cold finger, the colder stage of the refrigerator is coupled to a base of the primary cryopumping array, a raised surface that redirects molecules from the frontal opening toward the cryopumping array is provided on a floor above the base of the primary cryopumping array, and the condensing array and the floor are coupled to the cold stage of the refrigerator through struts that pass through the base of the primary cryopumping array.
15. The cryopump as claimed in claim 1 further comprising a vacuum vessel having a mounting flange about a flange opening, the vacuum vessel, radiation shield and primary cryopumping array each having a diameter greater than a diameter of the flange opening.