Beam Profile Measurements with a Slit-faraday Cup and a Wire Scanner for a Newly Developed 18 Ghz Superconducting Ecr Ion Source and Its Lebt*

In this presentation we show results of beam profile measurements by a slit-Faraday cup and a wire scanner. Argon 8+ beams were generated in a new liquid heliumfree superconducting electron cyclotron resonance ion source (ECRIS). The ECRIS, named SMASHI, was successfully developed at the National Fusion Research Institute in 2014, and in the future it will be dedicated for highly charged ions matter interaction research facility (HIMIRF). Before designing HIMIRF terminals after low energy beam transport (LEBT), it is necessary to characterize the beam properties of the source and its LEBT line. The beam profile measurements have been done after an analyzing dipole magnet (DM). The slitFaraday cup and the wire scanner were installed at 25 cm and 120 cm from the exit flange of the DM, respectively. Between the two diagnostics an Einzel lens was positioned to control the focusing of diverged beams. Here, with the measurements we checked the present beam alignments in the LEBT, and studied the dependence of beam profile variation on the operations of beam optics such as steering magnets and Einzel lens. INTRODUCTION A new superconducting 18 GHz electron cyclotron resonance ion source and its low energy beam transport were developed at the National Fusion Research Institute in South Korea [1]. The source, named SMASHI (Superconducting Multi-Application Source of Highlycharged Ions), will be dedicated for future application of highly charged ions in the area of matter interaction, diagnostic imaging, and probing. In this proceeding, we briefly describe SMASHI and its LEBT. Then, we show preliminary results of beam charge spectra of He, O, Ar, Xe ion beams. In order to characterize the beam properties in the LEBT, we also measured beam profiles by a slit-FC system and a wire scanner, by which the beam alignments of the source and the LEBT are checked. Variations of beam profiles are studied with respect to different settings of ion optics in the LEBT. SOURCE DESCRIPTION Figure 1 shows the overall section view of SMASHI. As an ECRIS for generating multiply/highly-charged ions, SMASHI has following main features: twofrequency heating(18, 18+Δ GHz), high power-capable plasma chamber, remotely-positional variable gap extraction system, capability to generate a wide range of ion elements from gas to metal, and two diagnostic ports for the extraction region. All these features are highly oriented to the generation of diverse highly charged ions (HCI). Most of all, due to the helium-free SC magnet, SMASHI can be more economically operated with low power consumption, which therefore enabling the full system of ECRIS operated on a high-voltage platform. Microwave Injection In Fig. 1, the microwave injection side can be viewed. Normally, the injection electrode is located at the maximum position of the axial magnetic field, and depending on the source condition it can be moved to other optimum positions by adjusting the bellows. In the injection electrode two WR62 waveguide ports, an onaxis sputtering hole, a centered-perforated biased disk, two diagnostic/oven holes, and one gas hole were arranged [1]. The WR62 ports, placed well out of the plasma pattern, are separated by 120◦ from each other. The biased disk is shaped as a triangle with a thru-hole in its center, into which the on-axis sputtering target is inserted. The sputtering target system is remotely positional and designed to easily exchange different materials. Extraction System The extraction system, shown in Fig. 1, is a pullerEinzel lens system consisting of 3 electrodes. Each electrode is supported and guided by 4 rods fixed to the extraction chamber. The distance between electrodes can be adjusted when necessary. The whole extraction system is remotely positional by a motor-driven-control, where the gap between the plasma electrode and the puller electrode is adjustable by 20–50 mm. Table 1 summarizes the extraction conditions and beam characteristics. The resulted rms emittance for Ar was calculated by using IGUN with the inclusion of the magnetic field and charge state distribution (CSD). The resulting beam radius and the momentum of Ar beam are 33 mm and 41 mrad, respectively. Table 1: Extraction Conditions and Beam Characteristics Extraction voltage 30 (10-30) kV Gap distance 33 (20-50) mm Einzel lens (negative) 30 (10-30) kV Rms emittance for Ar at 500 mm from plasma electrode 48 mm mrad (Rmax=33 mm, Amax=41 mrad) ___________________________________________ *This work was supported by R&D Program of ‘Plasma Convergence & Fundamental Research’ through the National Fusion Research Institute of Korea (NFRI) funded by the Government funds #[email protected] Proceedings of IBIC2015, Melbourne, Australia MOPB035 Overview and Commissioning ISBN 978-3-95450-176-2 113 C op yr ig ht © 20 15 C C -B Y3. 0 an d by th e re sp ec tiv e au th or s Figure 1: A sectional layout of the NFRI 18 GHz superconducting ECR ion source (SMASHI) & its LEBT. Magnetic Structure The magnet system of SMASHI consists of four superconducting(SC) coils sets and a permanent hexapole. The SC coils is designed to be cooled by a single cryocooler (1.5W at 4.2 K) and give axial mirror fields of Binj = 2.0 T and Bext = 1.4 T, where Binj and Bext are the peak fields in the microwave injection region and the beam extraction region, respectively. The hexapole is created by 36 pieces of permanent magnets and gives a radial mirror field of Brad = 1.3 T. Figure 2 shows the magnet design, and Table 2 summarize the main parameters of the magnet. The more detailed design, cooling, and excitation results are found in references [2, 3] Table 2: Main Parameters Of The Magnet System