A Vacuum Cold Bore Test Section at the CERN ISR
A 2 m helium cooled vacuum test section has been inserted into the CERN ISR to investigate problems which could be encountered in future cold bore proton machines. The UHV bore is cooled from the helium bath via a variable pressure gas filled space which enables operation at any temperature between 2.5 K and ambient. Temperature and degree of surface contamination can be remotely controlled. First observations from nominally clean and from hydrogen contaminated surfaces operating at temperatures close to 4.2 K are presented.
Vacuum for particle accelerators and storage rings
Abstract Accelerator vacuum systems must be measured in kilometres rather than metres and operate down to or below 10−8 Pa. Vacuum requirements and design constraints are reviewed for different machines using, as examples, the intersecting storage rings (ISR) for protons, the large electron positron (LEP) machine for electrons and the ‘cold-bore’ large hadron collider (LHC) again for protons. Various dynamic interactions between the particle beam and the vacuum system which are specific to accelerators are described. This is followed by a general discussion on pumping, especially distributed NEG pumping, cold-bore design and certain operational aspects of large systems.
Nuclear spin-lattice relaxation in transition metal compounds with local tetragonal symmetry.
We report on the various contributions to the total spin-lattice relaxation rate in metallic materials with local tetragonal symmetry. The analytical formulae are given in the tight-binding approximation. The calculations show the relation between various partial electron densities of states and corresponding contributions to the relaxation rates. The presented formulae can be used to compare theoretically calculated electron band structure parameters with those obtained from NMR spin-lattice relaxation time measurements.