Tailored Vacuum Chambers for AC Magnets
The proposed LAMPF-II accelerator has a 60-Hz booster synchrotron and a 3-Hz main ring. To provide a vacuum enclosure inside the magnets with low eddy-current losses and minimal field distortion, yet capable of carrying rf image currents and providing beam stabilization, we propose an innovative combination pipe. Structurally, the enclosure is high-purity alumina ceramic, which is strong, radiation resistant, and has good vacuum properties. Applied to the chamber are thin, spaced, silver conductors using adapted thick-film technology. The conductor design can be tailored to the stabilization requirements, for example, longitudinal conductors for image currents, circumferential for transverse stabilization. The inside of the chamber has a thin, resistive coating to avoid charge build-up. The overall 60-Hz power loss is less than 100 W/m.
Penetration of the Field of a Bunched Beam through a Ceramic Vacuum Chamber with Metallic Coating
The penetration of the electro-magnetic field of a bunched beam through a ceramic vacuum chamber with a metallic coating on the inside is investigated. It is shown that the field will only penetrate the chamber if the thickness of the metallic coating is small as compared to the square of the skin depth in the metal, divided by the thickness of the ceramics. If, in addition, the chamber is surrounded by ferrite, as used in beam monitors, the field penetration is further reduced. The field outside of the chamber and the power losses in the metallic layer are calculated. It turns out that these losses can be larger by orders of magnitude than the, losses in a pure metallic vacuum chamber.
Operating Experience with LAMPF Main Beam Lines Instrumentation and Control System
Instrumentation and control (I&C) for the Los Alamos Clinton P. Anderson Meson Physics Facility (LAMPF) main beam line is based upon central computer control through remote stations which provide input and output to most devices. Operating experience shows that the ability of the computer to give high-quality graphical presentation of the measurements enhances operator performance and instrument usefulness. Experience also shows that operator efficiency degrades rapidly with increasing instrument response time, that is, with increasing delay between the time a control is changed and the result can be observed. For this reason, instrumentation upgrade includes speeding up data acquisition and display times to under 10 s. Similarly, television-viewed phosphors are being retained where possible since their instantaneous response is very useful. Other upgrading of the instrumentation system is planned to improve data accuracy, reliability, redundancy, and instrument radiation tolerance. Past experience is being applied in adding or relocating devices to simplify tuning procedures.