AVS 51st International Symposium
    Vacuum Technology Wednesday Sessions
       Session VT-WeM

Paper VT-WeM9
Development of Horizontal NEG Coating Cathode for Long Accelerator Beam Tubes

Wednesday, November 17, 2004, 11:00 am, Room 303D

Session: Contamination Control, Outgassing and Modeling
Presenter: D. Weiss, Brookhaven National Laboratory
Authors: D. Weiss, Brookhaven National Laboratory
H.C. Hseuh, Brookhaven National Laboratory
R. Todd, Brookhaven National Laboratory
P. He, Brookhaven National Laboratory
Correspondent: Click to Email
The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) is a superconducting heavy ion collider with two rings of 3.8 km circumference for high energy and nuclear physics research. As ion beam intensity increases so do pressure rises at RHIC room temperature ultrahigh vacuum (UHV) regions that limit further intensity gains. The pressure rises are associated with electron multi-pacting, electron stimulated desorption and ion desorption. NEG coated beam pipes have been proven effective to combat pressure rises in synchrotron radiation facilities and will be added to a significant portion of the UHV room temperature regions of RHIC. Standard stainless steel RHIC beam pipes have been NEG coated by vendors. Some special beam pipe assemblies in the RHIC experimental regions are made of beryllium and will be NEG coated at BNL. A NEG coating cathode, similar to the cathode in the low cost high yield cylindrical magnetron sputtering system developed by BNL for titanium nitride coating, has been developed to coat these special beam pipes. This cathode can accommodate chambers with lengths up to 4 meters. This system features a hollow, liquid cooled cathode that can achieve continuous sputter rates of several amps per meter. The stiffness and support of the cathode allows chambers to be coated in a horizontal position. The cathode comprises a hollow titanium tube partially covered with zirconium and vanadium ribbons. The ribbons are arranged to provide a uniform sputtering distribution and results in an acceptable NEG mixture deposited on the substrate. Vacuum performance of the NEG coated pipes was measured and coating properties analyzed with auger electron spectroscopy and scanning electron microscopy. The system design, development, and analysis results are presented.