Preparation And Research Of High Intensity High Charge State Cocktail Ion Beams

Impact of intense neutron irradiation on structural materials presents a challenge for the development of future advanced nuclear energy systems.Using heavy ion multi-beam irradiation to simulate and study the combined effects of material displacement damage,hydrogen and helium is an important new research development.Many scientific research institutions have developed multiple-ion-beam devices to simulate the radiation damage process more realistically in materials used in nuclear energy systems.However,these facilities have certain shortcomings,such as high cost,and limited beam energy and current intensity,which make the development of structural materials for fusion reactors an extremely time-consuming process.Therefore,to facilitate research on the synergistic effect of nuclear materials,new mixed-beam（cocktail-beam）irradiation technology has been developed utilizing the transmission,acceleration and precise regulation of mixed ion beams,which provides new opportunities for applying the multi-beam irradiation technology.This dissertation used the ECR+LEBT+RFQ accelerator structure of low-energy high-current heavy ion linear accelerator facility（LEAF）located at the Institute of Modern Physics,Chinese Academy of Sciences,to produce mixed ion beams comprising several types of ions of equal energy as single nucleons.To precisely control a cocktail beam,the multiple sub-system synchronous trigger,RFQ phase switching,and cocktail beam edge modulation and diagnosis technologies have been developed.Using the above techniques,the transmission and acceleration of 100 eμA⁴He⁺&⁵⁸Ni¹⁵⁺and ⁴He⁺&¹⁶O⁴⁺cocktail beams of single energy have been successfully realized.The resulting beam compositions were measured using different techniques.The results show that the obtained cocktail beams had high beam intensities,short switching time,low cavity ion loss rates and adjustable ion ratios.Irradiation experiments were carried out on SIMP steel using a ⁴He²⁺&¹H₂⁺cocktail beam output by the LEAF device.The results show that the materials irradiated with the cocktail beam exhibited more pronounces surface,swelling and hardening changes compared with those irradiated with single-ion beams.An energy modulator system for modulating ion energy was developed on the basis of the original LEAF device to satisfy the requirements of nuclear material irradiation experiments.The required physical parameters of the cavity were determined by beam dynamics simulations and its internal structure by electromagnetic simulations,while offline tests,such as cavity processing,assembly and cold molding,were also carried out.The experiments demonstrated that the main parameters of the cavity agreed with the simulation results.An energy modulation experiment was carried out with an 100eμA ¹⁸O⁵⁺beam,in which an original 0.5Me V/u single beam was successfully modulated into a beam with continuously adjustable energy of 0.3-0.7 Me V/u.The synergistic cocktail beams with variable energies were transmitted and accelerated using the combined ECR+LEBT+RFQ+energy modulator.According to the requirements of nuclear material irradiation experiments,with the help of the cocktail beam technology and the energy modulation system,0.65 Me V/u He⁺&0.5Me V/u Ni¹⁵⁺and 0.6 Me V/u He⁺&0.58 Me V/u Fe¹⁴⁺beams have been prepared.The composition,energy and beam ratio have been measured and analyzed by the diagnostic system.Compared with the conventional multi-beam irradiation technology,the synergistic cocktail beams prepared and studied in this dissertation not only have all the characteristics of the non-coordinated cocktail beams but also have adjustable ion energies,which can be used for controlling the deposition depth of ions in materials.