Suping Zhang

Emittance improvement efforts on the 15-20 mA dc H- multicusp source.

A 15 mA beam from the 15-20 mA dc H(-) multicusp source has been obtained at China Institute of Atomic Energy. In order to improve the emittance of extracted beam from this new multicusp source, some measures have been taken, i.e., increasing the length of the ion source body, improving the vacuum in the extraction area, injecting cesium vapor into the ion source, etc. The hardware, including the lengthened source body, the improved back cover and cesium heating system, and the extraction vacuum box, will be described. Initial results for these efforts aimed at emittance improvement will also be given in the paper.

Design, Construction, Installation, Mapping, and Shimming for a 416-ton Compact Cyclotron Magnet

The construction of a 100-MeV high-intensity cyclotron, from which proton beam will be extracted through stripping to several proton beam lines for different users, has been completed at China Institute of Atomic Energy. Given that it is the H-ions that are to be accelerated in the machine, the peak field is only 1.35 T. To simplify the fabrication, the pole adopts straight sector instead of the spiral one. Meanwhile, vertical focusing should be sufficiently high to obtain high-current proton beam. All these demands make it particularly difficult for the design and fabrication of the main magnet, which is heavy in weight and challenging to meet precision requirement in fabrication. In the process, we have developed a high-performance parallel computation PIC code for beam dynamics of high-current cyclotrons and for FFAGs, which can be used for beam dynamic simulation at a very precise level. The result is then applied to guide the design, fabrication, installation, magnetic mapping, and shimming of the 416-ton main magnet with a precision requirement up to 0.05 mm. Another challenge is due to the deformations of the magnet without/with the vacuum. The whole map measured in the vacuum has to be completed in such a big machine for the first time in the world. The result shows that all requirements, including the isochronous field, vertical focusing, and imperfection fields, have been satisfied properly. The first beam and the stable beam for an 8-h commissioning test had been achieved on July 4 and July 25, 2014, respectively.