Superconducting Cavity Beam Test in CESR
The first use of a superconducting accelerating structure in a storage ring is described. Two 5-cell 1500 MHz ''muffin tin'' superconducting niobium cavities (1 m active length) were operated in the Cornell 8 GeV e/sup +/e/sup -/ storage ring, CESR. A 6.1 mA beam was captured and stored at 3.5 GeV using only the superconducting cavity. Up to 12.5 kW was transferred to the beam by the cavity. Single bunch currents up to 12 mA were reached in conjunction with the normal 500 MHz RF. Beam induced higher order mode (HOM) powers of 290 W were carried to room-temperature loads by four couplers and waveguides; no HOM-induced cryogenic dissipation was detectable. Q's of the 76 most prominent resonances were measured. Transverse and longitudinal beam instabilities were studied by mechanically sweeping the tune of the cavities; current thresholds are compared to theory. The cavity exhibited the ability to survive breakdown at high incident power without degradation.
Operating experience with β=0.16 superconducting resonators
The ATLAS heavy‐ion accelerator at Argonne National Laboratory was completed in early 1985. This paper discusses early operating experience with the ATLAS linac, with particular attention to performance of the new β=v/c=0.16 resonators. The average operating field level achieved for these resonators on line is 3.2 MV/m. Results of off‐line tests of the β=0.16 resonators are also presented.
In search of optimum chest radiography techniques.
A nation-wide study of chest radiography in Sweden had previously revealed a large variation in the physical and technical factors involved, in particular the radiation dose. In this study the image quality could not be assessed unambiguously. The aim of the present study was to try to establish a correlation between visual grading of radiographs and physical and technical factors in order to find the optimum chest X-ray system. The physical and technical performance of 24 chest units was evaluated. Radiographs were taken of an anthropomorphic chest phantom supplied with test structures simulating various pathologies. Image quality was assessed by visual grading analysis of the radiographs. The physical and technical parameters of the units rated best were used to exemplify good radiographic practice. The results were in agreement with the recommendations issued by the Commission of the European Communities (CEC). It was also shown that low radiation dose is compatible with high-quality radiographic imaging of the chest.