Research On Several Problems In Heavy Ion FFAG Accelerator And C-ADS Particle Transporting

China-accelerator driven system (C-ADS) is a promising solution proposed for growing energy needs and secure disposal of nuclear waste produced by the running (or planning to build) nuclear power plants. ADS have some capabilities to provide clean nuclear energy, transmute nuclear waste and breed nuclear materials. Moreover, ADS have advantages including inherent safety to eliminate the possibility of nuclear criticality accident, high resources utilization, very little nuclear waste produced. So, ADS is widely thought to have a high economic benefit. The safe running of the C-ADS assembly, mainly consisting of high-power proton accelerator (HPPA), spallation target and sub-critical transmuter, puts forward high performance requirements firstly for high-power proton beam, secondly for high energy beam transport line (HEBT) connecting the accelerator exit and neutron target/beam dump.ADS HPPA has energy more than700MeV and beam power exceeding10MW, and also has high reliability, high availability and high maintainability. Fixed-field alternating gradient (FFAG) accelerator now increasingly development is a circular accelerator and has many merits such as high repetition frequency, high average beam intensity, small volume and low cost, so it may be considered as in theory one candidate for ADS HPPA. On the other hand, there is now no effective solution for helium embrittlement affecting microstructure performance of fusion reactor envelope material. Therefore, He2+beam need to be provided for further researches. By means of He2+FFAG accelerator, the feasibility of FFAG applied to ADS will be explored. He2+FFAG accelerator employs eight super-period with radial scaling triplet (DFD), affords2-36MeV beam, has radial orbit excursion0.5m and ring circumference11.42m for injection (14.51m for the maximum energy extraction). In view of low energy and high revolution period (1163.60ns-350.90ns), induction accelerating with four cavities and cavity voltage5kV is adopted. Two accelerating waveforms with energy spread constraining and simultaneously beam longitudinal focusing, namely double platform and head-tail restraint, are designed for particles longitudinal tracking. A2.45GHz microwave ion source, producing15mA He+and soon afterwards30mA He2+obtained by stripping from He+, and a high pressure platform or small booster are preliminary considered as injector assemblies.Beam optics design and beam distribution transformation are two aspects of C-ADS HEBT research. For a conveniently layout, a straight section connecting linac exit is inside a linac tunnel, followed by horizontal bending section placed in the transport line private tunnel, and the rest part is in a transmuter hall. The beam is climbed up first and then bended down to hit target for convenient installation of some related system and space rational use, and also the section is the smallest possible in the horizontal direction to simplify the design of shielding system. Two schemes of beam optics design aiming at different beam transformation methods are given in this doctoral thesis. For the first scheme, hurling magnet is horizontal followed by some quadruple magnets and vertical bending up achromatic section, and a φ20mm double-waist is designed10.43m upstream of target for conveniently installing a collimator. For the second scheme, three transport lines for different energies are shown to cater to C-ADS progress schedule, and some ample space are reserved for installing and debugging beam distribution transformation system.Beam distribution transformation is one of some problems for ADS, spallation neutron source and material irradiating effects, and two schemes are given. The first scheme adopts hurling magnet, producing rotating radial dipole field with amplitude modulation (AM) frequency kHz and sine-wave frequency more than kHz. When appropriate beams cross hurling magnet and downstream dipole/quadruple magnet, a φ300mm round beam with uniformity better than80%can be seen on target, which basically meets target requirements. The second scheme adopts nonlinear antisymmetric high order field. A simplified dodecapole field magnet (SDFM), well focusing particles in beam halo to inner layer of beam halo or beam core, is first propounded and is applied for national patent (201210334199.2). The combination of SDFM and antisymmetric sextupole, octupole, decapole magnet can theoretically get approximate uniformly distributed round beam with slightly larger size.The design of He2+FFAG accelerator and C-ADS HEBT are shown above. The conceptual design of He2+FFAG accelerator can be used to verify the feasibility of FFAG applied to ADS as well as to provide He2+beam. The preliminary design of C-ADS HEBT could be a reference for the later further optimization and engineering design of transport line, and also two schemes of beam distribution transformation basically meet the target requirements in tracking simulation or in theory.