High Performance Electron Cyclotron Resonance Ion Sources Research Articles

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.

Limitation of the ECRIS performance by kinetic plasma instabilities (invited).

Electron cyclotron resonance ion source (ECRIS) plasmas are prone to kinetic instabilities due to anisotropic electron velocity distribution. The instabilities are associated with strong microwave emission and periodic bursts of energetic electrons escaping the magnetic confinement. The instabilities explain the periodic ms-scale oscillation of the extracted beam current observed with several high performance ECRISs and restrict the parameter space available for the optimization of extracted beam currents of highly charged ions. Experiments with the JYFL 14 GHz ECRIS have demonstrated that due to the instabilities the optimum Bmin-field is less than 0.8BECR, which is the value suggested by the semiempirical scaling laws guiding the design of ECRISs.

Review of highly charged heavy ion production with electron cyclotron resonance ion source (invited)

The electron cyclotron resonance ion source (ECRIS) plays an important role in the advancement of heavy ion accelerators and other ion beam applications worldwide, thanks to its remarkable ability to produce a great variety of intense highly charged heavy ion beams. Great efforts over the past decade have led to significant ECRIS performance improvements in both the beam intensity and quality. A number of high-performance ECRISs have been built and are in daily operation or are under construction to meet the continuously increasing demand. In addition, comprehension of the detailed and complex physical processes in high-charge-state ECR plasmas has been enhanced experimentally and theoretically. This review covers and discusses the key components, leading-edge developments, and enhanced ECRIS performance in the production of highly charged heavy ion beams.

Metal-dielectric structures for high power electron cyclotron resonance ion source

Metal-dielectric (MD)-structures in electron cyclotron resonance ion source (ECRIS) devices (partially) restore the plasma ambipolarity and supply cold electrons to the plasma. Both effects lead to an enhancement of the plasma electron density and temperature and significantly increase the performance of this type of ion source. At the same time, MD-structures are well suited to reduce the heat load on cold masses by Bremsstrahlung radiation. Here, we report on experiments at high microwave powers to test the practical use of MD-structures for new, high performance ECRISs with their much higher power densities. The comparatively long conditioning times can be shortened by covering only those parts of the source with MD-structures, which are essential for the improvement.

36-segmented high magnetic field hexapole magnets for electron cyclotron resonance ion source

Two high magnetic field hexapoles for electron cyclotron resonance ion source (ECRIS) have successfully fabricated to provide sufficient radial magnetic confinement to the ECR plasma. The highest magnetic field at the inner pole tip of one of the magnets exceeds 1.5 T, with the inner diameter (i.d.)=74 mm. The other hexapole magnet provides more than 1.35 T magnetic field at the inner pole tip, and the i.d. is 84 mm. In this article, we discuss the necessity to have a good radial magnetic field confinement and the importance of a Halbach hexapole to a high performance ECRIS. The way to design a high magnetic field Halbach structure hexapole and one possible solution to the self-demagnetization problem are both discussed. Based on the above discussions, two high magnetic field hexapoles have been fabricated to be utilized on two high performance ECRISs in Lanzhou. The preliminary results obtained from the two ECR ion sources are given.

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.

Innovative ion sources for accelerators: the benefits of the plasma technology

The most important developments in the field of ion sources at INFN-LNS, Catania, have been based on the generation of warm plasmas by means of microwaves at different frequencies ranging from 2.45 GHz to 28 GHz. Different Electron Cyclotron Resonance Ion Sources (ECRIS) have been designed and built, in particular SERSE and CAESAR are working for the Supereonducting Cyclotron at LNS, at the operating frequency of 14, 18 and 28 GHz. The design of an innovative source to be operated at 28 or 35 GHz, named GyroSERSE, has been completed, with the aim to provide mA beams of highly charged heavy ions. This kind of design is particularly suited for the beam injectors of accelerator facilities to be built in the next decade. Three different 2.45 GHz microwave discharge ion sources (MDIS) have also been built for different purposes: to obtain high efficiency ionization for RIB production or to produce high current proton beam for Accelerator Driven System (ADS). A fourth compact one, with permanent magnets, is under construction. The description of these equipments will be carried out, along with the results of the hybrid ion source, consisting of a laser-generated plasma source coupled to the SERSE high performance ECRIS.

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.