No abstract available

[en] The gas loads of the SFC vacuum system decreased from 5.3 Pa·L/s to 0.47 Pa·L/s and the work-period of the cryogenic pump prolonged also from 3 days to 34.8 days when the PIG ion source was replaced by ECR ion source. It has been realized that the vacuum machine group consisting of the oil-diffusion pump and the boost pump is replaced by the cryogenic pump and the turbo-molecular pump. The pollution of the oil vapour in the vacuum chamber has been eliminated efficiently. The degree of vacuum is about (3-5) x 10^-5 Pa. The accumulation time has reached 14000h since the new vacuum system went into operation

[en] This paper describes a new large cryopump, not using liquid nitrogen, developed for the Lanzhou cyclotron. It consists of a cold head, a modified single and a standard two-stage miniature refrigerator. The pumping speed was measured as 24000 Is^-1 for nitrogen and 26000 Is^-1 for hydrogen. The ultimate pressure of 5 x 10^-6Pa in the 100m³ vacuum chamber has been obtained by using eight new cryopumps. (author)

[en] The vacuum chamber of the Separated Sector Cyclotron (SSC) for Heavy Ion Research Facility Lanzhou (HIRFL) to have been built is described. It is a large monolithic ultra-high vacuum vessel with 10 m in diameter and 4.5 m high, weighing 65 tn. The total volume is about 100 m³. There are 234 ports on it for various purpose. The mechanical analysis of the vacuum chamber is completed using a finite element method by means of the procedure SAP-5C on a computer. Uddholm 316 L super-low carbon stainless steel made in Sweden was selected as a structure material. Because of very big size, the monolithic vacuum chamber is divided into eight bigger and several smaller pieces to fabricate in the factory. Then it is transported by a train and a truck to the institute. Finally it is welded as a single vessel and machined in situ. In the interests of economy, the manual electric arc welding is the best choice in our case. It is paid great attention to strict technological process during welding. Owing to high requirements for ultrahigh vacuum, all of tight welded seams are inspected and checked by liquid peretration testing, X-ray examination and helium mass spectrometer detecting. All of the flanges are machined before welding as far as possible at the factory. Some big flanges are cut by special way in situ. The pressure of 8 x 10^-6 Pa for sufficient beam transmission in the vacuum chamber is obtained in September of 1986

No abstract available

[en] According to the problems found in the period of running for more than 10 years in the injector SFC (Sector Focusing Cyclotron) of Heavy Ion Research Facility in Lanzhou, an extensive improvement included vacuum pressure, distribution of magnetic field as well as RF system was carried out in recent years. The practice in beam tuning and operation for more than half year indicated that the status of SFC is improved obviously. (authors)

No abstract available