High Performance Electron Cyclotron Resonance Research Articles

Numerical simulation of magnetic field influence on plasma and electron extraction of electron cyclotron resonance neutralizer

Electron cyclotron resonance (ECR) neutralizer is a key component of electron cyclotron resonance ion thruster (ECRIT) with a diameter of 10 cm, which plays an important role in maintaining the spacecraft potential balance and neutralizing the ions in the plume region. Optimizing magnetic field distribution is an important way to improve the performance of neutralizer. At the same time, the uniformity of the magnetic field and the position of the magnetic trap can affect the magnetic field characteristics, plasma performance, electron extraction process, and beam current. Previous experimental researches showed that the beam current extraction performances of the two ECR neutralizers with different magnetic field uniformity and different magnetic trap locations are significantly different. However, it is difficult to reveal the physical phenomena and causes only through experiments, so numerical simulation is needed. Therefore PIC/MCC codes for the ECR neutralizers with different uniformity of magnetic field and different positions of magnetic trap are established. Under the given electron extraction potential, numerical simulations are accomplished to study electron extraction procedure and analyze its influence on the performance of the neutralizer. The simulation results show that when the magnetic field uniformity is low and the magnetic trap is located upstream of extraction orifice, the migration of electrons from the magnetic trap to the outlet is limited by the magnetic field and the electric field, thus a higher potential energy is needed to extract the electrons. Otherwise, when the magnetic field uniformity is high and the magnetic trap is located at the downstream of extraction orifice, electrons will be more likely to migrate towards the magnet trap. After the electrons reach the magnetic trap, under the action of the anode potential, the external potential is higher, and the external weak magnetic field almost fails to hold these electrons, Therefore a large number of electrons can be extracted at low extraction potential. This research will lay an important foundation for the development of high-performance ECR neutralizer.

Superconducting Magnets for High Performance ECR Ion Sources

Modern heavy ion accelerators require intense heavy ion beams with high charge state. Electron cyclotron resonance (ECR) sources are the primary tool for generating such beams, making them indispensable devices for heavy ion physics research. Remarkable performance advancements were obtained during the last decades. At present, state of the art “third generation” ECR ion sources are based on magnets built with NbTi conductor. However, future nuclear physics facilities will require significant improvement in beam intensity and quality, which can only be met by ECR sources operating at higher frequency and field. These fourth generation machines will need to incorporate a sophisticated sextupole magnet built with high performance Nb3Sn or NbTi conductor. In this paper, we review the technical challenges and worldwide progress in developing high performance superconducting ECR ion sources, and discuss the development of both third and fourth generation ECR ion source magnets at IMP.

Split Magnet for Efficient Electron Cyclotron Resonance Ion Sources Developments

The development of high performance Electron Cyclotron Resonance Ion Sources (ECRIS) greatly depends on the feasibility of sophisticated magnetic structures with high field gradients. The most powerful ECRIS are based on superconducting technologies. The application of high magnetic field techniques like split polyhelices permits to build low cost prototypes with a short development time, this is a key issue to develop a Research and Development program in ion sources science. We describe here the first ECRIS cusp prototype we have built with this technology. A 5 T field gradient on a 90 mm distance have been measured on the main axis of the helices for a 15000 A current intensity applied. This contribution summarizes the latest experimental achievements with the split polyhelix magnetic structure.

Low energy beam transport for facility for rare isotope beams driver linear particle accelerator

The driver linac for the facility for rare isotope beams (FRIB) will provide a wide range of primary ion beams for nuclear physics research. The linac will be capable of accelerating a uranium beam to an energy of up to 200 Mev∕u and delivering it to a fragmentation target with a maximum power of 400 kW. Stable ion beams will be produced by a high performance electron cyclotron resonance ion source operating at 28 GHz. The ion source will be located on a high voltage platform to reach an initial beam energy of 12 keV∕u. After extraction, the ion beam will be transported vertically down to the linac tunnel in a low energy beam transport (LEBT) system and injected into a radio frequency quadrupole (RFQ) operating at a frequency of 80.5 MHz. To meet the beam power requirements, simultaneous acceleration of two-charge states will be used for heavier ions (≥Xe). This paper presents the layout of the FRIB LEBT and the beam dynamics in the LEBT. In particular, simulation and design of the beam line section before charge state selection will be detailed. The need to use an achromatic design for the charge state selection system and the advantage of an ion beam collimation system to limit the emittance of the beam injected into the RFQ will be discussed in this paper.

Measurement of the high energy component of the x-ray spectra in the VENUS electron cyclotron resonance ion source

High performance electron cyclotron resonance (ECR) ion sources, such as VENUS (Versatile ECR for NUclear Science), produce large amounts of x-rays. By studying their energy spectra, conclusions can be drawn about the electron heating process and the electron confinement. In addition, the bremsstrahlung from the plasma chamber is partly absorbed by the cold mass of the superconducting magnet, adding an extra heat load to the cryostat. Germanium or NaI detectors are generally used for x-ray measurements. Due to the high x-ray flux from the source, the experimental setup to measure bremsstrahlung spectra from ECR ion sources is somewhat different from that for the traditional nuclear physics measurements these detectors are generally used for. In particular, the collimation and background shielding can be problematic. In this paper, we will discuss the experimental setup for such a measurement, the energy calibration and background reduction, the shielding of the detector, and collimation of the x-ray flux. We will present x-ray energy spectra and cryostat heating rates depending on various ion source parameters, such as confinement fields, minimum B-field, rf power, and heating frequency.

Measurement of the high energy component of the x-ray spectra in the VENUS electron cyclotron resonance ion source (abstract only)

High performance electron cyclotron resonance (ECR) ion sources, such as VENUS (versatile ECR for nuclear science), produce large amounts of x rays. By studying their energy spectra, conclusions can be drawn about the electron heating process and the electron confinement. In addition, the bremsstrahlung from the plasma chamber is partly absorbed by the cold mass of the superconducting magnet adding an extra heat load to the cryostat. Germanium or NaI detectors are generally used for x-ray measurements. Due to the high x-ray flux from the source, the experimental setup to measure bremsstrahlung spectra from ECR ion sources is somewhat different than for the traditional nuclear physics measurements these detectors are generally used for. In particular, the collimation and background shielding can be problematic. In this paper we will discuss the experimental setup for such a measurement, the energy calibration and background reduction, the shielding of the detector, and collimation of the x-ray flux. We will present x-ray energy spectra and cryostat heating rates in dependence of various ion source parameters such as confinement fields, minimum B-field, rf power, and heating frequency.

Brief review of multiple charge state ECR ion sources in Lanzhou

Electron Cyclotron Resonance (ECR) ion sources have been under development in Institute of Modern physics (IMP) for more than 25 years. With these years’ study, we have done a lot in this field and developed many outstanding high performance ECR ion sources including the 10GHz LECR1 (Lanzhou ECR ion source No.1), 14.5GHz LECR2, the double-frequency heating ECR ion source-LECR3 and the latest being developed fully superconducting source-SECRAL (Superconducting ECR ion source with Advanced design at Lanzhou), which is supposed to be a higher performance source with an innovative magnet design. Apart from the solenoidal coils type ECR ion sources we have also constructed some all permanent ECR ion sources, such as the LAPECR1 (Lanzhou All Permanent ECR ion source No.1) and LAPECR2. These sources mentioned above work together to deliver intense multiple charge state ion beams for HIRFL (Heavy Ion Research Facility at Lanzhou) accelerators’ injection and atomic physics research. In this paper, we will have a brief review on the IMP ECR ion sources and the typical results of the gaseous element ion beams and also the metallic ion beams. The application of the ion beams on accelerators and atomic physics research will be briefly introduced.

Electron cyclotron resonance ion source developments in RIKEN (invited)

We have constructed four high performance electron cyclotron resonance (ECR) ion sources in RIKEN and produced a variety of intense beams of heavy ions (e.g., 2 emA of Ar8+, 0.6 emA of Kr13+, 0.3 emA of Xe20+). During the improvement of their performance, we found that several key parameters play essential role on increasing the beam intensity. The parameters are plasma electrode position, magnetic field configuration, property of the chamber wall material and position of a biased disk. To investigate how the parameters influence on the beam intensity, we made a systematic study using the laser ablation method. In these experiments, we observed that Bmin influences the electron density and confinement time of ECR plasma.

High intensity metal ion beam production with ECR ion sources at the Lawrence Berkeley National Laboratory

The large number of different experiments performed at the 88 Inch Cyclotron requires great variety and flexibility in the production of ion beams. This flexibility is provided by the two high performance electron cyclotron resonance (ECR) ion sources, the LBL ECR and the AECR-U, which can produce beams of ions as light as hydrogen and as heavy as uranium. With these two sources, up to six different metals can be preloaded using two types of ovens. The ovens are mounted radially on the ion sources and inject the metal vapor though the open sextupole structure into the plasma chamber. For the superconducting ECR ion source VENUS, which is under construction at Lawrence Berkely National Laboratory, the use of radial ovens is no longer possible, because the magnetic structure is closed radially. Therefore, we are developing two new axial oven types for low and high temperature applications. Metal ion beam production in ECR ion sources using the oven technique is discussed. The design of the axial oven is presented. Finally, the efficiency of the axial oven is compared with the radial oven for the production of Ca.

General purpose high-performance electron cyclotron resonance ion source for production of multicharged ions

There is a growing interest for high performance electron cyclotron resonance ion source (ECRIS) working in various environments and dedicated to various purposes. In this article we will present three typical machines using classical FeNdB radial magnets and coils. The first one, called “SuperNanogan II,” is a fully permanent magnet machine, copying exactly the ECR4 magnetic structure. Here the purpose consists in producing high currents of high charge state ions on a high voltage platform (up to 250 μAe of Ar10+40 and Ca11+48). The second one, called “Super n+,” is a very high magnetic field machine dedicated to be used as high performance charge booster for the 1+/n+ ISN/GANIL program. The source is built around a ∅ 9 cm minimum |B| structure closing a maximum closed magnetic line of 1.8 T, so allowing functioning points from 2.45 to 35 GHz. The third one is a hybrid machine using an existing 4 T superconducting mirror field, where it is possible to place inside a well optimized 1.6 T FeNdB multipole. This machine can be used as a classical 6.4 to 35 GHz ECR ion source or just as an “ECR ion trap” in order to optimize the trapping of hydrogenlike ion for spectroscopic purpose.

Design and construction of a superconducting magnet system for an Electron Cyclotron Resonance (ECR) ion source

The cyclotron accelerator at Laboratorio Nazionale del Sud in Catania, Italy will be equipped with a high-performance ECR ion source. This source which is presently under construction comprises a so-called Minimum-B magnetic bottle of 130 mm diameter and 480 mm length. The specified magnetic field values are 2.7 T, 1.6 T and 0.37 T respectively for the axial component at the two ends and at the center. The transverse field component is required to reach 1.4 T at the cylindrical boundary. The complex field configuration is produced by means of a compound superconducting coil system whose essential parts are an approximately 800 mm long sextupole and three coaxial solenoids surrounding the sextupole. All windings will be made from NbTi composite conductors and impregnated with epoxy resins. Bath cooling at 4.5 K for all coils will be provided by a warm-bore type cryostat with horizontal axis. The paper presents design and construction of the coil system, its support structure and the cryostat.

High Performance Electron Cyclotron Resonance Plasma Etching with Control of Magnetic Field Gradient

It is shown that high-performance Electron Cyclotron Resonance (ECR) plasma (hyper-ECR) is effective as a dry etching technique for fabrication of VLSI devices. The gradient of the magnetic field is one of the most important parameters for a uniform high etch rate. The Si etch rate and the ion current density can rise with decreasing magnetic field gradient. The high uniformity of the etch rate is achieved with highly uniform distribution of the magnetic field gradient. The density distribution of plasma is also improved by the hyper-ECR, so the drift instability is stabilized and a no-microloading etching process is produced.