A Diagnostics of Ion Beam from 28ghz Electron Cyclotron Resonance Ion Source

A neutron radiography facility utilizing a 28 GHz superconducting electron cyclotron resonance (ECR) ion source and a heavy ion accelerator is now under construction at Korea Basic Science Institute (KSBI). In order to generate a proper energy distribution of neutron, a lithium ion beam is considered. It will be accelerated up to the energy of 2.7 MeV/u by using a radio frequency quadrupole (RFQ) and drift tube linear (DTL) accelerator. The 28 GHz superconducting ECR ion source, which is the state of the art of an ion beam injector, has been built to produce the lithium ion beam. The ion beam of 12 keV/u would be extracted to low energy beam transport (LEBT) system, which is comprised of several types of electromagnets to focus and deliver the beam, effectively. After transporting an ion beam through LEBT, RFQ once accelerates the ion beam from 12 to 500 keV/u. Finally, we can achieve the final beam energy after accelerating at the DTL. Before the ion beam is delivered to accelerator, the requirements should be satisfied to confirm the status of beam. For this, we developed the instruments in the diagnostic chamber in the middle of LEBT system to observe the beam dynamics. An analyzing electromagnet, slits, wire scanners and faraday cup will be used to perform a diagnosis of ion beam characteristics. We will present and discuss the experimental results of ion beam profile and the current after selecting are required charge state. INTRODUCTION For the research facility based on accelerator technology at KBSI, a 28 GHz superconducting ECR ion source, a LEBT system, and linear accelerators are under development [1]. Recently, ECR plasma ignition was successfully implemented using 28 GHz superconducting ECR ion source [2]. Since then, a ion beam extraction from ECR ion source is scheduled to experiment. In the ion beam extraction test, the beam properties will be measured using various diagnostic technique. Figure 1 shows the layout of the KBSI Accelerator research facility. The first application to the KBSI accelerator research facility is neutron radiography. For the generation of neutron, the inverse kinematics technique is considered. In this method, a lithium beam accelerated up to 2.7 MeV/u will impact the hydrogen gas target, then the neutron will be generated. In order to accelerate lithium beam, radiofrequency quadrupole and drift tube linear accelerator will be used. Figure 1: The layout of the KBSI accelerator research facility. Also, for the beam transmission from ECR ion source to RFQ a LEBT system is designed. The schematic of LEBT system is showed in Figure 2. Figure 2: The schematic of LEBT system. ___________________________________________ #[email protected] Proceedings of IBIC2014, Monterey, CA, USA WEPF12 General Diagnostics ISBN 978-3-95450-141-0 561 Co py rig ht © 20 14 CC -B Y3. 0 an d by th er es pe ct iv ea ut ho rs The details of the LEBT system are presented next section. LOW ENERGY BEAM TRANSMISSION SYSTEM In order to satisfy the requirement for the input beam of RFQ, the LEBT system is designed. The whole LEBT system consists of a dipole magnet, three pair solenoids, three quadrupole magnets, four steering magnets, and two diagnostic chamber (1 spare). For the LEBT design, the TRANSPORT code is used[3]. The initial beam parameters are shown in table 1.The results of beam transport simulation are shown in the Figure 3. The abbreviation of Sol, D, BM, DG, QM is pair solenoid, drift tube, dipole magnet, diagnostic chamber, and quadrupole magnet, respectively. In Figure 3, the total length of the LEBT is 7 m and the calculated maximum beam size is around 4 cm. The elements of the LEBT are fabricated based on the results. Table 1: The Initial Beam Parameters