Evaluation of CBA (Colliding Beam Accelerator) First String Full Cell Vacuum System

摘要

The CBA (Colliding Beam Accelerator, formerly known as ISABELLE) Full Cell Magnet System consisting of six superconducting dipole magnets and two superconducting quadrupole magnets requires two separate vacuum systems. One, known as beam vacuum operates below 3 x 10 exp -11 Torr and the other, known as insulating vacuum, operates at less than 10 exp -7 Torr to isolate cryo circuits from atmosphere and from the uhv beam tubes. The uhv bore tube is isolated from the 4.0 exp 0 K magnet by thirty-six (36) layers of superinsulation and insulating vacuum. Heat load measurements on the bore tube have been completed and found to agree with data obtained in smaller controlled experiments. Measurements of helium, accumulated on cryogenic pumped charcoal panels over many weeks, have verified sensitive helium mass spectrometer leak detection methods for vacuum integrity, providing sound design of the welded complex. The Full Cell was assembled and operated under conditions that would exist in the completed machine. Pressures below 2 x 10 exp -11 Torr beam vacuum requirement and below 2 x 10 exp -7 Torr insulating vacuum, were routinely achieved during all phases of the Full Cell operation and support systems testing. (ERA citation 09:001086)