Production Of High Intensity High Charge State Ion Beams And Development Of High Performance ECR Ion Sources

ECR（Electron Cyclotron Resonance）ion source is one of the most effective devices for producing high intensity high charge state ion beams.Due to its long-term reliability,stability,repeatability,and excellent beam quality,ECR ion source has become the preferred choice for most heavy ion accelerator injectors.With the development of heavy ion application devices and dedicated research equipment,there is a growing need for more stable,reliable,and high-performance ECR ion source as the injector.This dissertation describes in detail the design,development,and experimental research of two types of high-performance ECR ion sources.One is the18 GHz room temperature ECR ion source LECR5（Lanzhou ECR ion source No.5）based on traditional room temperature magnet technology,and another one is a hybrid superconducting ECR ion source HECRAL（Hybrid ECR ion source with Advanced design in Lanzhou）based on a combination of superconducting coils and permanent magnet.The development of high-performance 18 GHz room-temperature ECR ion source is described.This second-generation room-temperature ECR ion source with excellent performance,stability,and reliability,is widely used in heavy ion accelerator devices.Based on the requirements of the 300 Me V proton heavy ion accelerator in the Space Environment ground Simulation Research Infrastructure of Harbin Institute of Technology,the characteristics of high-performance 14.5 GHz and 18 GHz room-temperature ECR ion sources are systematically studied,which is the theoretical basis for a new room-temperature ECR ion source LECR5 development that enables its stable operation at 18 GHz microwave frequency.The ion source is designed to operate in a mode with high magnetic field,high microwave power density,and large plasma chamber volume.The ion source uses a combination of high-current density copper coils cooled by high-pressure deionized water and a high magnetic field hexapole permanent magnet to generate an 18 GHz microwave plasma confinement magnetic field.The axial magnetic mirror field is generated by three sets of independent solenoidal pancakes,with a highest current density of 12 A/mm²,and efficient cooling of the coils is realized through an independent cooling water pressurization system（20kg/cm²）.The soft iron structure is optimized to enhance the magnetic mirror fields,resulting in an injection peak magnetic field of 2.6 T.An independent intermediate coil is designed to achieve precise control of the ECR region,thereby adjusting the plasma heating and confinement conditions over a wide range,resulting in production of intense ion beams of highly charged ions from H₂⁺to Bi³²⁺.The radial hexapole permanent magnet uses a Halbach structure with 36 fan-shaped blocks and high-performance Nb Fe B permanent magnet materials to produce a radial magnetic field of over 1.2 T on the plasma chamber wall with a diameter of（?）80 mm.The overall structure of the ion source adopts an integrated installation design,reducing the concentricity error of the axial and radial magnetic fields,and improving the collimation characteristics and beam quality of the extracted ion beam.The successfully developed LECR5 can produce high intensity high charge state ion beams,represented by 2.12 em A O⁶⁺,62 eμA Ar¹⁶⁺,81 eμA Bi³²⁺,and 34 eμA U³³⁺under the high microwave power conditions of dual-frequency 14.5+18 GHz,demonstrating it is one of the best performing room-temperature ECR ion sources.LECR5 has been deployed on the 300 Me V proton heavy ion accelerator,the CAFE2 facility dedicated for superheavy element synthesis research,and the heavy ion single particle effect research device,which has indicated good beam quality,stability,and repeatability during online operation.The development of a novel hybrid superconducting ECR ion source is presented.Based on the successful development of the high-performance 18 GHz room-temperature ECR ion source LECR5,to produce em A-level C⁴⁺and 10 pμA-level medium mass M/Q～3 ion beams,this dissertation design and develop the first high-performance hybrid superconducting ECR ion source HECRAL in China.To achieve the similar performance of high intensity ion beams of medium and high charge states as all-superconducting ECR ion sources in the frequency range of 18～24 GHz.HECRAL further enhances the concepts of the high magnetic field,high microwave power density,and large plasma chamber volume established in LECR5.The axial magnetic field of the ion source uses Nb Ti superconducting coils to generate a 3.4 T at source injection,1.7 T at source extraction,and a wide range minimum magnetic mirror field flexibility inside a（?）260 mm warm bore.The radial magnetic field is generated by a hexapole permanent magnet,using a new Non-Halbach structure that produces a radial magnetic field of over 1.4 T on the plasma chamber wall with a diameter of（?）100mm.In terms of magnet structure,this work solves the problem of strong magnetic field forces between hybrid magnets and demagnetization of permanent magnets.The cold body suspension of the axial coil uses titanium alloy rods to ensure the safety and structural stability of the cold body under strong magnetic fields at 24 GHz and the force of the hexapole magnetic field.To solve the demagnetization problem of the permanent magnet under its self-produced field and strong external fields,precise demagnetization analysis for each component magnet block and designing a set of large aperture high magnetic field hexapole permanent magnets with some various high-performance Nb Fe B permanent magnet materials for high magnetic fields,high reliability,and safety.The dissertation discusses in detail many engineering and technical problems,such as magnet structure design,complex magnetic force problems,and the design and development of high magnetic field anti-demagnetization hexapole permanent magnet,and so on.HECRAL has been successfully tested at 18 GHz,and the ability to produce high charge state ion beams is very close to that of all-superconducting ECR ion sources at the same frequency,represented by 723 eμA O⁷⁺,543 eμA Ar¹²⁺,360 eμA Kr¹⁹⁺,430 eμA Xe²⁶⁺,1.02 em A C⁴⁺,and 158 eμA Ca¹⁴⁺,which can meet the needs of the HIAF for early beam commissioning,high intensity metal ion beam for CAFE2,and also other needs from heavy ion accelerators for heavy ion beam applications.HECRAL ion source is currently the best-performing hybrid superconducting ECR ion source in the world.As described above,this work has successfully developed two high-performance high charge state ECR ion sources,which have demonstrated they are the best performing machines in comparison with other similar ECR ion source.The key technical challenges,such as the design and processing of high magnetic field permanent hexapole magnet,the design and development of large warm bore high magnetic field hybrid superconducting magnet,and the production of high reliability,high stability,and high repeatability high intensity high charge state ion beam,have been handled with successful solutions.The developed devices have been gradually applied to routine operation with heavy ion accelerators and have achieved good operating results.