Development Of Ion Source Research Articles

The development of the 17F beam at the Holifield radioactive ion beam facility

This report details some of the key technological developments employed at the Holifield Radioactive Ion Beam Facility (HRIBF) to produce beams of 17F using the 16O(d, n) 17F reaction. The oxide fiber target material used at the HRIBF is described and a comparison is made between the 17F yield achieved using light (Al) and heavy (Hf) metal oxide fibers. The development of the Kinetic Ejection Negative Ion Source (KENIS) employed in this work is also discussed along with the operational principles of the source. Finally, a detailed description of the HfO 2 target configuration used to produce 10 7–10 8 17F ions/s for over 850 hours of operation is provided. To date, seven nuclear physics experiments using accelerated beams of 17F and 18F produced using this apparatus have been performed over an energy range of 10–170 MeV.

Particle Beam Application-Present Status and Future Prospects. Particle Beam Applications for Nuclear Fusion Research. Development of Ion Sources for IFMIF.

Ion sources for the International Fusion Materials Irradiation Facility (IFMIF), an accelerator-based high intensity neutron source to test and develop materials for fusion machines, are developed. The required specifications of the ion source are 100 keV, and 155 mA of D+ with CW operation. This report presents an overview of the IFMIF and the current status of the ion source development.

Development of negative ion sources for the ITER neutral beam injector

A vacuum insulated beam source (VIBS), where all the components including the negative ion source and the acceleration grids are immersed in the vacuum, has been designed at Japan Atomic Energy Research Institute. The beam source is characterized by high gas flow conductance that reduces stripping losses of negative ions in the accelerator and improves the acceleration efficiency. The gas flow in VIBS was calculated using a 3-D Monte-Carlo code. At a typical operating pressure of 0.3 Pa in the negative ion source, the stripping loss of D − ions in VIBS is about 23%, which is about half of stripping loss in the gas insulated beam source (GIBS) that was designed in the ITER-FDR design. The acceleration efficiency is improved from 84 to 94%. To enhance the acceleration efficiency further, the possibility for reducing the operating pressure was experimentally studied. It was found the negative ion production in the KAMABOKO source adopted for ITER is dominated by surface production, therefore, the operating pressure can be reduced by improving plasma confinement. It is predicted that the operating pressure in KAMABOKO source can be reduced to 0.15 Pa, where the stripping loss and the acceleration efficiency in VIBS are improved to be 13 and 97%, respectively.

Progress in the development of a large RF negative ion source for fusion

A large area RF source for negative ion-based injection systems has been developed and for the first time H −-current densities have been extracted which are comparable to those produced by conventional arc sources. This paper describes the design of the source and gives the results of H −-extraction experiments. A feature of this RF source is an increase of extracted ion current by up to a factor of four if noble gases are added to the hydrogen discharge. By this effect, a current density of 9 mA/cm 2 at 0.65 Pa has been achieved in volume production. With caesium seeding up to 20 mA/cm 2 could be extracted at 1 Pa source pressure with the addition of argon and a hot plasma grid. Recently, the RF source has been modified for long pulse operation by the installation of a Faraday screen.

Recent developments of long pulse RF ion sources for NBI systems

For the new radial injector of the Wendelstein 7-AS stellerator, two medium size 40 kW RF sources (‘W7-AS RF source’) have been built and tested. A positive hydrogen ion beam of 28 A at 50 kV with a proton fraction of 60% has been extracted. For future injection systems, in particular those based on negative ions, large area beam extraction and long pulse capability up to cw operation are envisaged. At IPP two different design concepts of RF sources are being investigated in order to meet these requirements: in the first one, the plasma is generated in one or two small circular RF sources (‘drivers’), which are mounted onto the back plate of a 30 l expansion volume (‘bucket’) with magnetic multi-cusp confinement of the plasma (‘Type 6-1’ and ‘Type 6-2’ respectively). In the second concept the plasma is generated inside the bucket by an internal RF coil, which is insulated by a quartz tube (‘Type 5’). In both cases the applicability for negative as well as for positive ion production is being tested. The next application will be in the positive ion based injectors in the third injector of JET and in the W7X stellerator.

Atomic spectrometry update. Atomic mass spectrometry

The review this year is dominated by the large number of publications on AMS, ICP-MS and SIMS. The increasing number of new AMS installations bears witness to the increasing interest in the technique now that smaller and simpler systems are becoming more widely available. Although high-energy systems still have an important role to play, each of the new systems was compact and of relatively low-energy. The development of ion sources that can accept gaseous samples has lowered the sample size requirement for radiocarbon analysis such that it is now little more than the background level. Contamination therefore has become a major issue. The numerous papers on improvements to SIMS analysis demonstrate the important role the technique plays in materials science. Unlike for most of the techniques covered, fundamental studies on SIMS analysis abound with particular attention being paid to understanding the ionization processes and the representativeness of the measured ion beam. Quantum chemistry calculations have been used to determine the fundamental processes occurring in cell ICP-MS. This approach contrasted with the empirical studies that are normally undertaken. Although many applications are still being published using collision and/or reaction cell ICP-MS, there were fewer novel or fundamental studies than in previous years. This suggests that cell ICP-MS is becoming a more routine method of analysis. The same can probably also be said of hyphenated ICP-MS methods for speciation, which continues to grow in importance but which is very much at the applied end of the spectrum. Speciation is notable in that it cuts across a number of MS techniques and conventional organic MS techniques are increasingly being investigated for structure determination of organometallic species. Each year seems to find further expansion of MC-ICP-MS into ‘non-traditional’ isotope analysis. This was the year for Ti isotope analysis. This Update is the 21st and last annual review on atomic mass spectrometry and follows the same format as last year's.1 Although an attempt is made to consider all relevant refereed papers, conference abstracts, reports, book chapters and patents for inclusion, the content of the review is highly selective. The selection of papers is based on criteria applied to focus sharply on the most significant developments in instrumentation and methodology or improved understanding of the fundamental phenomena involved in the MS process. The main ruling criterion for all speciation papers is that the work should involve or be intended for the study of natural systems. For example, the study of synthetic metal clusters is generally not included whereas the determination of organometallic compounds in environmental samples is. Applications of atomic MS are not covered in this Update and readers are referred to the Updates on Industrial Analysis: Metals, Chemicals and Advanced Materials,2 Environmental Analysis3 and Clinical and Biological Materials, Food and Beverages.4 Other, fundamental, reviews appear on X-ray fluorescence spectrometry5 and atomic emission, absorption and fluorescence spectrometries.6 Throughout this review, the term molecular ion will be restricted to denote only the positive or negative radical ion formed by removal or capture, respectively, of an electron. In contrast, addition of a proton or cation to a neutral molecule gives molecular adduct ions. Deprotonated molecules are considered as fragments. Although reproducibility or precision is a key figure of merit in MS, there is no agreed format for quoting it. The reader can assume that values of precision given in this Update as a percentage correspond to the RSD unless otherwise specified. For isotope ratios, however, values of precision are generally given as the SD of a permil value. It is a widespread phenomenon that analytical techniques in general and MS in particular spawn a large number of abbreviations and acronyms. A glossary of all abbreviations used in this Update appears at the end of the review. Most abbreviations are not defined in the text but those which are unlikely to be commonly known are defined in the text when used first and again in the glossary. It should be noted that throughout the text the letter C denotes the element carbon and not the unit of charge, the coulomb. The writing team would welcome feedback from readers of this review and invite you to complete the Atomic Spectrometry Updates questionnaire on http://www.asureviews.org.

Ion sources and injectors for HIF induction linacs

Ion source and injector development is one of the major parts of the HIF program in the USA. Our challenge is to design a cost effective driver-scale injector and to build a multiple beam module within the next couple of years. In this paper, several current–voltage scaling laws are summarized for guiding the injector design. Following the traditional way of building injectors for HIF induction linac, we have produced a preliminary design for a multiple beam driver-scale injector. We also developed an alternate option for a high current density injector that is much smaller in size. One of the changes following this new option is the possibility of using other kinds of ion sources than the surface ionization sources. So far, we are still looking for an ideal ion source candidate that can readily meet all the essential requirements.

Studies of low-energy electron attachment at surfaces

Studies of the formation of negative ions at heated metal surfaces are reported under two experimental conditions: (1) laser desorption/ablation ionization and (2) heated metal wires in the presence of fluorine gas. In condition (1), nanoclusters of boron nitride/graphite are first produced by laser ablation of boron nitride mixed with graphite in a heated (∼1100 °C) rare gas followed by laser desorption negative ionization to yield a wide variety of cluster anions. The negative ion mass spectra for laser ablation/desorption ionization of small cluster ions from fullerenes, graphite, or most carbon containing metals (e.g. stainless steel) show common features (C n − for n = 1 to ∼10, with even > odd alternation). The laser serves to heat the surface, produce clusters, and provides free and “quasifree” electrons for attachment and to dissociate larger negative ions/neutrals to produce low-mass cluster anions. Laser desorption of C 60H 36 and C 60F 48 at high laser power results in intense H − and F − ion signals, respectively. In the case of C 60H 36, the H − ion production is attributed to dissociative electron attachment, i.e. e + C 60H 36 → C 60H 35 + H −. For the case of C 60F 48, both dissociative attachment and photodissociation of C 60F 48 − are believed responsible for the F − ion yield. These observations form the basis for the development of intense pulsed ion sources of H − and F − ions for use in energy production (fuel injection into fusion reactors), spallation neutron devices, lithography, and other applications. In condition (2), heated metal wires of Al, Au, Au/Pd, Nb, Ni/Cr, Pt, Re, Ta, Ti, V, W, and Zr are “burned” in a low pressure vapor of fluorine gas (∼10 −4 Torr) resulting in a wide variety of molecular anions (e.g. Al 2F 9 −; AuF 2,3 −; NbF 6 −; ReF 5,6 −; TaF 6 −; Ti 4,5 −; VF 4,5 −; WF 5,6 −; ZrF 5 −, and Zr 2F 9 −) of varying intensity. Also of interest are the occurrences of F 3 − and the “impurity” ion Na 2F 3 −.

Photodetachment diagnostic techniques for measuring negative ion densities and temperatures in plasmas

Photodetachment diagnostic techniques can help determine densities and temperatures of negative ions in a variety of scientific devices in which these ions are one of the major charged particle species. This method has been extensively used in the development of hydrogen negative ion sources as well as other devices. In order to obtain spatial resolution, a photodetachment diagnostic technique is used with an electrostatic probe that detects the currents of photodetached electrons.

On-line combustion of samples for AMS and ion source developments at ORAU

Each stage in the handling of radiocarbon samples provides an additional opportunity for contamination and increased cost. For large samples, graphitization is worthwhile since it allows precise AMS measurements to be made in a short time. Some samples, however, do not require high precision. These include small samples, for which high precision is impossible, and samples for which only an approximate date is required. In these cases, there is an advantage in burning the samples and then introducing the CO 2 directly into a gas ion source. ORAU has developed a system for performing on-line combustion, which is being tested for routine use. This paper presents the performance characteristics and explains the main design features. Such systems are expected to be useful for small samples in radiocarbon dating, the pre-screening of radiocarbon ages and in biomedical applications. The hybrid (graphite and CO 2) ion source at Oxford has also been upgraded to incorporate a 40-target sample changing mechanism. This can be used both for graphite samples and for the targets required for measurements on CO 2.

Development of ECR ion sources in China (invited)

Recent development of electron cyclotron resonance (ECR) ion sources in China is reviewed. Emphasis is put on high charge state ECR ion sources which have been mainly developed in China by Institute of Modern Physics (IMP). Presently two ECR ion sources built by IMP for highly charged ion beams are put into operation for cyclotrons and atomic physics research. The development of high charge state ECR ion sources at IMP has progressed with a new magnetic field configuration, better condition for extraction of highly charged ions, high mirror magnetic field, large plasma volume, and special techniques to provide extra cold electrons. These techniques greatly enhance the production of highly charged ions from IMP ECR ion sources. So far more than 185 eμA of Ar11+ and 50 eμA of Xe26+ were produced by the IMP ECR ion sources. The metallic ion beam production was tested and the first beam Ca11+40 was provided to the cyclotrons at IMP. The beam intensity of Ca11+40 could reach 130 eμA. The next part of this article will report the latest progress of 2.45 GHz ECR ion sources in China. A 2.45 GHz compact permanent magnet proton ion source was designed and constructed by IMP. A new microwave feeding system is applied on this ion source. The ion source is able to deliver 90 mA of mixed ion beam (H1++H2++H3+) after preliminary commissioning. The article also mentions a small 2.45 GHz ECR ion source which was built by Sichuan University and used for industry applications. The dependence of plasma density and electron temperature on radio frequency power, neutral gas pressure, and different microwave windows was measured by a Langmuir probe on this ion source.

Negative hydrogen ion source development for large helical device neutral beam injector (invited)

Large-scaled hydrogen negative ion source development is reviewed for a negative ion based neutral beam injector (NBI) in the large helical device (LHD) fusion machine. The target performance of the ion source is characterized by a high current of 30–40 A with a relatively low energy of 120–180 keV. A series of negative ion source development is conducted with a one-dimensionally reduced size of ion sources which still have a large beam area of 25 cm×26 cm or 50 cm with multi apertures. We employed a cesium-seeded volume production source with an external magnetic filter for the source development. Improvement of the arc plasma confinement is effective to produce a high-current negative ion of 16 A with a current density of 31 mA/cm2 at a low operational gas pressure below 0.4 Pa. Suppression of the accelerated electrons is achieved both by strengthening the magnetic field at the extraction grid and by shaping the inside of the extraction grid aperture to shield the secondary electrons against the acceleration electric field. Multi beamlets delivered from a large area are finely focused with the aperture displacement technique applied to the grounded grid. Based on these results, the LHD-NBI negative ion source was designed and fabricated with a beam area of 25 cm×125 cm. The LHD-NBI source produced 25 A of negative ions with an energy of 104 keV at a low gas pressure of 0.3 Pa. A long-pulse negative ion beam of 81 keV–1.3 MW was produced for 10 s. Four sources were installed to the LHD-NBI system, and around 4 MW of neutral beams were injected into the LHD plasmas with an energy of 100–110 keV in the first period for the NBI experiments. The LHD-NBI ion source is still being developed to improve its performance, and the key issues for the improvement are discussed.

Development of a compact multicusp ion source of He+

A filament-type helium ion source has been developed for the purpose of alpha particle diagnostics and as a test beam for electrostatic quadrupole transport experiments. We have obtained preliminary results of He+ beam current, ∼60 mA/cm2. The normalized brightness of this beam is ∼1010 A/(m rad)2. The normalized emittance (90%) measured by multislit faraday cup emittance meter is ∼0.6 mm mrad below 100 V, 10 A arc discharge. The effects of plasma parameters in the source on the beam emittance and on the beam perveance are discussed.

Status report on electron cyclotron resonance ion source operation at the Flerov Laboratory of Nuclear Reactions (Joint Institute for Nuclear Research) cyclotrons

Two electron cyclotron resonance (ECR) sources, DECRIS-14-2 and ECR4M, are presently in permanent operation at the Flerov Laboratory of Nuclear Reactions cyclotrons, U400M and U400, respectively. A wide range of ions of gases from He up to Xe was delivered by the sources and accelerated in the cyclotrons. Major efforts were made in the production of high current stable ion beams of solids with relatively low melting points in mass ranges from Li up to Bi. Both the evaporator and the MIVOC technique were used. Among the solids a beam as exotic as Ca48 was produced at the U400 cyclotron with high efficiency. The main results on production of ion beams of gases and solids are reported. For further development of ECR ion sources a test bench was designed and built. The test bench is equipped with the new DECRIS-3 ion source. The parameters of the test bench and ECR source are described.

Negative ion sources for high energy accelerators (invited)

Due to the development of reliable H− ion sources, charge-exchange injection into circular accelerators has become routine. For preacceleration of heavy ions tandem generators with a stripping foil are used in order to double the energy with the same high voltage. This article reviews recent developments in negative hydrogen ion sources. The underlying physics, operating parameters, and beam characteristics of selected sources will be described and compared.

The contribution of the INFN-LNS to the development of electron cyclotron resonance ion sources (invited)

The study of the axial injector for the superconducting cyclotron of the Laboratori Nazionali del Sud (LNS) began in 1989, with the aim of replacing the radial injection from a 15 MV Tandem with the injection by a modern electron cyclotron resonance ion source (ECRIS) which could be able to produce beams of highly charged ions to the same extent. The design of a superconducting ECRIS, named SERSE, was established in the two following years and funded since 1993, 2 yr before the extraction of the first beam from the cyclotron; the construction took more than 4 yr and in August 1997 SERSE, was ready in the test bench of CEA/DRFMC in Grenoble. The source was moved to LNS in May 1998 and since then it is operating with excellent results. During 1993–95, the concept of High B mode, on which SERSE was based, was tested at MSU-NSCL and the results have been applied to other sources, including the room temperature CAESAR that will share with SERSE the duty of the production of ions for the cyclotron. Even though the performances of this source are not comparable to the ones of SERSE, CAESAR is able to perfectly fulfill the ordinary request of our accelerator complex. The last project of LNS concerns the design of a scaled version of SERSE with higher field, to be operated at the gyrotron frequency (28 GHz or higher). The results of the existing sources will be reviewed, along with the main features of the new project.

Development of a steady-state microwave ion source with large spherical electrodes for geometrical focusing

A steady-state electron cyclotron resonance ion source with large spherical electrodes has been developed to study the plasma wall interaction, erosion mechanism, and hydrogen retention of first wall materials in a nuclear fusion reactor. Discharge characteristics of the ion source were studied in terms of microwave power, magnetic field configuration, and gas (H2) pressure. Ion saturation current density Jis of about 21 mA/cm2 near the electrodes (target value is 20 mA/cm2) was achieved with microwave power of 3.0 kW and magnetic field of 2.3 kG at an optimal gas pressure. The measurement of Jis was made by a Langmuir probe. It was found that the dependence of ion saturation current density on the magnetic field was different between high (>5 mTorr) and low (<5 mTorr) pressure. The change of the gas inlet position from the center of the plasma production chamber to near the microwave input window gave higher ion saturation current density.

Development of a high-current laser ion source for induction accelerators

We have developed a high-current laser ion source that can provide low-charge-state ions for induction accelerators. A frequency-doubled Nd:YAG laser (λ=532 nm) irradiated a copper target with relatively low intensities of 108–109 W/cm2. The laser-produced plasma supplied a large number of Cu+ and Cu2+ ions over 1014 ions/cm2 at a distance of 10 cm from the target. We have successfully extracted high-current copper beams over 0.1 A/cm2 using an inductive acceleration module. The beam emittance measured by a pepper-pot method was about 40 πmm mrad. © 2000 American Institute of Physics.

Development of the compact electron cyclotron resonance ion source for heavy-ion therapy

Carbon–ion cancer treatment is successfully being made at the Heavy Ion Medical Accelerator in Chiba (HIMAC). Design philosophy for the ion sources for medical facilities are as follows: (1) sufficient beam intensity, a few hundred e μA; (2) long lifetime with good stability; (3) easy operation and easy maintenance; and (4) compactness. In order to develop such source for future heavy-ion facilities, we have tested compact electron cyclotron resonance (ECR) ion sources using permanent magnets both for axial and radial confinement of hot electrons. Since the yield of C2+ ion in the first developed source (2.45 GHz ECR) was 15 e μA and far below the medical requirement (∼150 e μA for the HIMAC), a new source has been proposed, having a frequency of 10 GHz. The extracted intensity of C4+ (and C2+) ions is expected to be higher than 200 e μA.

Metal vapor vacuum arc ion source development at GSI

The status of experimental research, ongoing development, and upgrade of the high current metal vapor vacuum arc ion source is presented. By applying a magnetic field in the cathode region of the vacuum arc ion source it is possible to shift the charge state distribution to higher mean charge state. The combination of a magnetic field and small metal meshes in the plasma drift region is used to decrease the beam noise and to improve the ion beam stability. The results of experiments on the beam stability with different magnetic fields, cathode materials, and mesh are presented and discussed.