High-intensity Ion Source Research Articles

Overview of high intensity ion source development in the past 20 years at IMP.

Ion source development over the last 20 years at the IMP is reviewed. For versatile purposes, several types of ion sources have been involved in the research and development work at the IMP, i.e., the highly charged ECR (Electron Cyclotron Resonance) ion source, intense microwave ion source or the 2.45 GHz intense beam ECR ion source, and laser ion source (LIS). In the development of ECR ion sources, SECRAL (Superconducting ECR ion source with Advanced design in Lanzhou), Lanzhou ECR ion source, and Lanzhou all permanent magnet ECR ion source series have been made, which can cover the operation microwave frequency range of 10-28 GHz. The LIS with an Nd:YAG laser with a maximum output energy of 8 J in 8 ns pulse duration has been developed for very intense short pulse ion beams from solid materials such as C, Ti, Ni, Ag, and so on. Microwave ion sources have been built to produce intense pulsed or direct current beams from several mA to 100 mA for either high intensity accelerators or applications. This paper will give an overview of the high intensity ion source development at the IMP, especially on the recent progress and new results, such as the status of the fourth generation ECR ion source (first fourth generation ECR ion source), the production of recorded highly charged ion beams with SECRAL sources, key technology research studies, and so on.

Review of high intensity ion source development and operation.

The Electron Cyclotron Resonance Ion Source (ECRIS) has transformed the nuclear physics research field over the last 47 years. Today, the performance of ion sources is the first parameter that defines the design performance of existing facilities as well as the design approach and performance of new facilities. In this paper, I will review the current "state of the art" performance capabilities for ECRISs as well as other ion sources and how those current capabilities form the primary design criteria for new nuclear physics facilities and set the limiting performance for existing facilities. I will close with a short-term look into the future for these ion sources and other competing types.

Development of high intensity D-T fusion neutron generator HINEG

The high intensity D–T fusion neutron generator (HINEG) has been developed at Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences/FDS Team, which will be a significant neutronic experimental platform for research and development of nuclear technology and safety, including the validation of neutronic method and software, radiation protection, material activation, and irradiation damage as well as neutronic performance of components. Its application can also be extended to nuclear medicine, radiotherapy, neutron imaging, and other nuclear technology applications. HINEG consists of two phases: the first phase, named HINEG-I, aims to have the intensity of 1012 n/s in order of magnitude, and the second phase, HINEG-II, is designed to reach a neutron yield of 1014–1015 n/s via high-power tritium target system and high-intensity ion source. HINEG-I has been completed and commissioning with the intensity produced of 1.1 × 1012 n/s, while the feasibility of HINEG-II has been preliminarily demonstrated. This paper will summarize all the latest progress and future plans for the research and development of HINEG. © 2016 The Authors. International Journal of Energy Research published by John Wiley & Sons Ltd.

Injection of auxiliary electrons for increasing the plasma density in highly charged and high intensity ion sources

Different electron guns based on cold- or hot-cathode technologies have been developed since 2009 at INFN for operating within ECR plasma chambers as sources of auxiliary electrons, with the aim of boosting the source performances by means of a higher plasma lifetime and density. Their application to microwave discharge ion sources, where plasma is not confined, has required an improvement of the gun design, in order to "screen" the cathode from the plasma particles. Experimental tests carried out on a plasma reactor show a boost of the plasma density, ranging from 10% to 90% when the electron guns are used, as explained by plasma diffusion models.

Focusing and transport of high-intensity multi-MeV proton bunches from a compact laser-driven source

Laser ion acceleration provides for compact, high-intensity ion sources in the multi-MeV range. Using a pulsed high-field solenoid, for the first time high-intensity laser-accelerated proton bunches could be selected from the continuous exponential spectrum and delivered to large distances, containing more than ${10}^{9}$ particles in a narrow energy interval around a central energy of 9.4 MeV and showing $\ensuremath{\le}30\text{ }\text{ }\mathrm{mrad}$ envelope divergence. The bunches of only a few nanoseconds bunch duration were characterized 2.2 m behind the laser-plasma source with respect to arrival time, energy width, and intensity as well as spatial and temporal bunch profile.

Note: Emittance measurements of intense pulsed proton beam for different pulse length and repetition rate

The high intensity ion source (SILHI), in operation at CEA-Saclay, has been used to produce a 90 mA pulsed proton beam with pulse length and repetition rates suitable for the European Spallation Source (ESS) linac. Typical r-r(') rms normalized emittance values smaller than 0.2π mm mrad have been measured for operation in pulsed mode (0.01 < duty cycle < 0.15 and 1 ms < pulse duration < 10 ms) that are relevant for the design update of the Linac to be used at the ESS in Lund.

Automatic generation of IGUN(C) input files for enhanced mesh resolution at the plasma meniscus

The plasma-beam interface (meniscus) is highly nonlinear and its correct simulation needs a mesh resolution of the order of the Debye length. In high intensity ion sources, the plasma density is usually too high and the Debye length is too small for a sufficient mesh resolution. A well established method to overcome this dilemma is the use of a field line and an equipotential line to be created in a first run, in order to dissect the simulation problem into a plasma part with much higher mesh resolution and a transport part with usual resolution. In the past many users of IGUN have found it difficult to perform this dissection. Therefore, a new feature has been added to IGUN to automatically write new input files for the dissected areas. For this a field line starting point needs to be defined as well as the potential of a pseudo electrode. The field line then is used for the plasma part as a slanted and curved Neumann boundary, while the pseudo electrode will act as the extraction electrode. The trajectory end data then are used in the automatically generated concatenating run as ion starting input without any need for the user to adjust for positions or different mesh resolutions. Here we show as an example the simulation of the well-known CHORDIS ion source, the calculated field line, the pseudo equipotential line, and the resulting simulations for the automatically generated input files for the plasma and the transport parts.

Design of RF Power System for CPHS

Abstract The Compact Pulsed Hadron Source (CPHS) system has been proposed and designed by the Department of Engineering Physics of Tsinghua University in Beijing, China. It consists of an accelerator front-end—a highintensity ion source, a 3 MeV radiofrequency quadrupole linac (RFQ), and a 13 MeV drift-tube linac (DTL), a neutron target station, and some experimental stations. In design of our RF power supply, both RFQ and DTL share a single klystron which is capable of 2.5 MW peak RF power and a 3.33% duty factor. The 325 MHz klystron contains a modulating anode and has a 100 kW average output power. Portions of the RF power system, such as pulsed high voltage power supply, modulator, crowbar protection and RF power transmission are all presented in details in this paper.

Development of high intensity ion sources for a Tandem-Electrostatic-Quadrupole facility for Accelerator-Based Boron Neutron Capture Therapy

Several ion sources have been developed and an ion source test stand has been mounted for the first stage of a Tandem-Electrostatic-Quadrupole facility For Accelerator-Based Boron Neutron Capture Therapy. A first source, designed, fabricated and tested is a dual chamber, filament driven and magnetically compressed volume plasma proton ion source. A 4 mA beam has been accelerated and transported into the suppressed Faraday cup. Extensive simulations of the sources have been performed using both 2D and 3D self-consistent codes.

The Compact Pulsed Hadron Source: A Design Perspective

During the past. decades, large-scale national neutron sources have been developed in Asia, Europe, and North America. Complementing such efforts, compact hadron beam complexes and neutron sources intended to serve primarily universities and industrial institutes have been proposed, and some have recently been established. Responding to the demand in China for pulsed neutron/proton-beam platforms that are dedicated to fundamental and applied research for users in multiple disciplines from materials characterization to hadron therapy and radiography to accelerator-driven sub-critical reactor systems (ADS) for nuclear waste transmutation, we have initiated the construction of a compact, yet expandable, accelerator complex-the Compact Pulsed Hadron Source (CPHS). It consists of an accelerator front-end (a high-intensity ion source, a 3-MeV radio-frequency quadrupole linac (RFQ), and a 13-MeV drift-tube linac (DTL)), a neutron target station (a beryllium target with solid methane and room-temperature water moderators/reflector), and experimental stations for neutron imaging/radiography, small-angle scattering, and proton irradiation. In the future, the CPHS may also serve as an injector to a ring for proton therapy and radiography or as the front end to an ADS test facility. In this paper, we describe the design of the CPHS technical systems and its intended operation.

High-intensity ion sources for accelerators with emphasis on H− beam formation and transport (invited)

This paper lays out the fundamental working principles of a variety of high-current ion sources for accelerators in a tutorial manner, and gives examples of specific source types such as dc discharge-driven and rf-driven multicusp sources, Penning-type, and electron cyclotron resonance-based sources while discussing those principles, pointing out general performance limits as well as the performance parameters of specific sources. Laser-based, two-chamber, and surface-ionization sources are briefly mentioned. Main aspects of this review are particle feed, ionization mechanism, beam formation, and beam transport. Issues seen with beam formation and low-energy transport of negative hydrogen-ion beams are treated in detail.

A new secondary ion mass spectrometry (SIMS) system with high-intensity cluster ion source

Secondary ion mass spectrometry (SIMS) with gas cluster ion beams (GCIB) was investigated with experiments and molecular dynamics (MD) simulations. A new cluster SIMS system with high-intensity cluster ion source has been developed. Ar cluster ion beam with the average size of 2000 was utilized as a primary ion beam. The beam diameter is less than 1 mm at the target position, and a current density of 10 μA/cm 2 is obtained. The etch rate of Si with this current density is more than 20 nm/min, which is far beyond the etch rate in recent low energy SIMS system. The secondary ion intensity linearly increases with the acceleration voltage. A threshold voltage of a few keV for secondary ion emission was found. These results are consistent with previous sputtering experiments.

Characterization of a high-intensity unipolar-mode pulsed ion source with improved magnetically insulated diode

A magnetically insulated ion diode (MID) with an improved external-magnetic field system has been developed and installed onto a TEMP-6-type high-intensity pulsed ion source in order to produce a high-intensity pulsed ion beam (HIPIB) for surface modification of materials. The external-magnetic field MID is operated in unipolar mode based on dielectric high-voltage flashover, and a double coaxial pulse-forming line (PFL) powered with a Marx generator is used to form the unipolar pulse of nanosecond width. A specially designed cathode has been constructed with a forked connection to two symmetrically installed transformers to improve the effect of the magnetic field and thus increase the stability of generation and propagation of the ion beam. It was found that the efficient generation of HIPIB mainly depended on the magnetic field strength, the gas pressures in reverse and output switches of PFL, and the anode–cathode (A–K) gap of the external-magnetic field MID. A proper magnetic field strength was found with magnetic field power system at dc charging voltage of 8 kV. The proper A–K gap distance is not uniform with the value varied from 6 to 8 mm. Suitable gas pressures for reverse and output switches were about 1.2 and 2.4 atm, respectively, at a charging voltage of 40 kV to the Marx generator. The most efficient plasma generation and ion extraction led to a maximum output of HIPIB with a peak ion current density of 300 A cm−2 and a beam pulse width of 80 ns (full width at half maximum), at an accelerating pulse of 300–350 kV with a pulse width of 70 ns.

Characterization of a high-intensity bipolar-mode pulsed ion source for surface modification of materials

A high-intensity pulsed ion source of TEMP-type series, operating in bipolar mode, has been developed as a unique pulsed energy source to produce a high-intensity pulsed ion beam (HIPIB) for surface modification of materials. To generate the ion beam, a specially shaped bipolar pulse, consisting of a first negative pulse and a second delayed positive pulse both of nanosecond width, is formed by a double coaxial pulse-forming line (PFL) powered with a Marx generator and supplied to a magnetically insulated ion diode (MID) by a self-magnetic field. It is found that the efficient generation of a HIPIB is mainly dependent on the delay time of the bipolar pulse, adjusted by pressure ratio in the two gas switches of a PFL, and the anode–cathode (A–K) gap distance in the self-magnetic field MID. The delay time determines the effective area on the anode surface for plasma generation and the A–K gap distance ensures the stability of the process. A proper delay time and a proper A–K gap distance are obtained by a series of experimental investigations. Under delay time from 30 to 280 ns and several different A–K gap distances, the typical wave forms of the bipolar pulses at a dc charging voltage of 45 kV to Marx generator are illustrated to clarify the effects of delay time and A–K gap distance on the ion beam generation. The proper A–K gap distance is not uniform, varied from 6 to 8 mm, and the corresponding proper delay time is 250 ns. The most efficient plasma generation leads to a maximum output of HIPIB with a peak ion current density of 350 A cm−2 and a beam pulse width of 75 ns (full width at half maximum), at an accelerating pulse of 220 kV with a pulse width of 100 ns.

Ion-source modeling and improved performance of the CAMS high-intensity Cs-sputter ion source

The interior of the high-intensity Cs-sputter source used in routine operations at the Center for Accelerator Mass Spectrometry (CAMS) has been computer modeled using the program NEDLab, with the aim of improving negative ion output. Space charge effects on ion trajectories within the source were modeled through a successive iteration process involving the calculation of ion trajectories through Poisson-equation-determined electric fields, followed by calculation of modified electric fields incorporating the charge distribution from the previously calculated ion trajectories. The program has several additional features that are useful in ion source modeling: (1) averaging of space charge distributions over successive iterations to suppress instabilities, (2) Child’s Law modeling of space charge limited ion emission from surfaces, and (3) emission of particular ion groups with a thermal energy distribution and at randomized angles. The results of the modeling effort indicated that significant modification of the interior geometry of the source would double Cs + ion production from our spherical ionizer and produce a significant increase in negative ion output from the source. The results of the implementation of the new geometry were found to be consistent with the model results.

Time resolving diagnostic of the compensation process of pulsed ion beams at high-intensity light ion source

Time-resolved measurements of the compensation process have been performed at the (high-intensity light ion source)-low-energy beam transport test stand (CEA-Saclay) using an 92 kV; 73 mA proton beam. A residual gas ion energy analyzer was used to measure the potential distribution as a function of time. To measure the radial density profile of the ion beam a charge coupled device camera has been used to perform time-resolved measurements and to estimate the rise time of compensation. Both measurements in combination allow an investigation of the space-charge compensation process due to the residual gas ionization and the experimental study of the rise of compensation. A numerical simulation of selfconsistent equilibrium states [J. Pozimski, Il Nuovo Cimento 106, A.N.11 (1993)] of the ion beam has been used to determine plasma parameters such as the density and the temperature of the electrons from the measured data. An interpretation of the acquired data and the achieved results is given.

Last results of the continuous-wave high-intensity light ion source at CEA-Saclay

The high-intensity light ion source (SILHI) is designed to be a prototype source for high power linear accelerators. The goal is to produce a 100 mA proton or a 140 mA deuteron ion beams at 95 keV with rms normalized emittance lower than 0.2 π mm mrad. A 108 mA total beam (J=215 mA/cm2) was extracted in April 1997 (85% H+, 12% H2+, and 3% H3+ fractions) with two electron cyclotron resonance (ECR) zones located at both plasma chamber extremities simultaneously. First beam measurements indicate a 0.17 π mm mrad rms normalized emittance for a 80 mA proton beam at 80 keV. In these conditions, a 96% availability was obtained during an 8 h working day. An intermediate electrode is placed in the accelerator gap to minimize emittance distortions as shown by simulations. Beam analysis were made as a function of the intermediate electrode voltage, the gas flow, the magnetic field, and the 2.45 GHz rf power. First rf plasma coupling observations indicated that the magnetron was too highly coupled with the load (plasma chamber). By adding a second circulator and locking the oscillator with an external signal, this dependence was decreased. Measurements then clearly show that the output spectrum is completely independent of the load phasing. All these results will be presented.

A compact multi-sample high-intensity negative ion source

A high-intensity cesium sputter negative ion source was designed for accelerator mass spectrometry. The source was developed and built in Triumf and is currently being used at the Rehovot pelletron tandem. The source features an internal cesium oven and simplified target insulation. A pneumatically actuated sample changer contains a 28-target wheel but allows manual loading of a single target as well. Negative ion beam currents obtained match or exceed those of ion sources of similar designs; the current remains constant for hours and low memory effects are observed as the targets are cycled.

Space-charge compensation of highly charged ion beam from laser ion source

The problem of matching an ion beam delivered by a high-intensity ion source with an accelerator is considered. The experimental results of highly charged ion beam transport with space-charge compensation by electrons are presented. A tungsten thermionic cathode is used as a source of electrons for beam compensation. An increase of ion beam current density by a factor of 25 is obtained as a result of space-charge compensation at a distance of 3 m from the extraction system. The process of ion beam space-charge compensation, requirements for a source of electrons, and the influence of recombination losses in a spacecharge-compensated ion beam are discussed.

41Ca measurements at the Zurich AMS facility

With a half-life of (104±5) kyr, which lies between the one of 14C and 36Cl, 41Ca is of interest for studies of the irradiation history of extraterrestrial materials. The determination of 41Ca by activity measurement is not easy because it purely decays via electron capture with K-X-rays of 3.3–3.6 keV. A better way to measure the 41Ca content is to use accelerator mass spectrometry (AMS). Our main goal is to study the production cross-sections of 41Ca and to analyze samples of extraterrestrial material. In order to obtain absolute 41Ca 40Ca ratios a new standard reference material has been produced by irradiating 40CaCO 3 in the DIDO reactor of KFA Jülich and measuring the 41Ca activity with liquid scintillation spectroscopy at the PTB. As the use of CaH 3 − ions minimizes the 41K background CaH 2 targets have been produced. For the AMS measurements of 41Ca the first attempts with our tandem accelerator with only 6 MV are shown. A high-intensity ion source and final identification with the dE dx technique and a time-of-flight measurement has been used. At the present status of the experiment blank values of 41Ca 40Ca ratios of 10 −13 have been reached, just limited by the detection efficiency.