Evaluation of the colliding beam accelerator first string full cell vacuum system

The CBA (colliding beam accelerator, formerly know 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 3×10−11 Torr and the other, known as insulating vacuum, operates at less than 10−7 Torr to isolate cryocircuits from atmosphere and from the UHV beam tubes. The UHV bore tube is isolated from the 4.0 K magnet by 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, proving sound design of the welded complex. The full cell was assembled and operated under conditions that would exist in the completed machine. Pressures below 2×10−11 Torr beam v...