Duoplasmatron Source Research Articles

Influence of oxygen/argon duoplasmatron synergistic modification on the mechanical properties of UHMWPE/vinyl ester composites

AbstractThis study reveals double plasma modification of ultra‐high molecular weight polyethylene (UHMWPE) fibers by oxygen/argon duoplasmatron source to investigate the synergistic effect of double plasma mixture on the mechanical performance of UHMWPE/vinyl ester laminated composites. The single‐factor experiment was used to determine the preparation process parameter range. The modified fiber was characterized and mechanical properties of UHMWPE/vinyl ester composites were evaluated. The results showed that the UHMWPE fiber modified by double plasma treatment with oxygen/argon duoplasmatron source exhibited more hydroxyl groups than untreated fiber and the single plasma‐modified fiber with oxygen source, and the surface water adsorb capacity was significantly improved, which contributed to the combination of resin and fiber surface. The tensile strength of the composite with double plasma modification increased to 380.48 MPa, which was higher than untreated and oxygen plasma treated samples by 36.9% and 18.9%, respectively. The GIC value was even 78.1% higher than that of oxygen plasma‐treated sample, and the interlaminar shear strength was increased by 19%. In terms of low‐velocity impact response, the absorbed energy of double plasma modified composites was increased, confirming that the mechanical resistant performance was enhanced by the modification with oxygen/argon duoplasmatron source.

Design and optimization study of a duoplasmatron ion source for high-intensity proton beam

Nanjing Proton Source (NPS) is a high-intensity superconducting accelerator large-scale scientific facility proposed by Nanjing University. As the advanced research project, a low-energy injector is going to be set up at the first stage. In consideration of stable performance and low cost, a duoplasmatron ion source is chosen to provide 50 keV, 40 mA proton beam for the downstream RFQ matching by a low-energy beam transport (LEBT). The duoplamatron is designed based on the existing plasma reservoir structure and optimized for low RMS emittance. The paper mainly describes the design work about the plasma generation system and the optimization study of a triode extraction system for minimizing the normalized RMS emittance. The simulation shows that a slightly concave plasma meniscus contributes to improving beam qualities. At present, the duoplasmatron source and beam diagnostics have been set up, and the source prototype is on commissioning.

Optimization and analysis of a low-energy injector for high-intensity proton beam

Nanjing University and local government are pushing ahead with a high-intensity proton linac project called Nanjing Proton Source (NPS). At the first stage, a low-energy injector including an ion source and a low-energy beam transport (LEBT) will be set up to provide 65 keV, 28 mA proton beam. A duoplasmatron source with triode electrodes and a two-solenoid magnetic focusing LEBT is our favorable choice. As we know, the most important role of the LEBT is to minimize the emittance growth and optimize the Twiss parameters into radio frequency quadrupole (RFQ). This paper clearly introduces the optimization procedure that sets effective solenoid fields as two free parameters to search for the minimum rms emittance and the best-matched Twiss parameters by plotting contour maps. The detailed LEBT layout and solenoids design are completed based on the optimization. The robustness and stability of the LEBT are also analyzed in the end. The beam phase-space distribution and beam qualities are discussed under a range of space charge compensation degrees and different initial beam distribution types. Besides, the LEBT is designed to eliminate the vast majority of beam contaminants by using two collimators.

High-spatial-resolution measurements of iron isotopes in pyrites by secondary ion mass spectrometry using the new Hyperion-II radio-frequency plasma source.

Iron isotopic signatures in pyrites are considered as a good proxy for reconstructing paleoenvironmental and local redox conditions. However, the investigation of micro-pyrites less than 20 μm in size has been limited by the available analytical techniques. The development of a new brighter radio-frequency plasma ion source (Hyperion-II source) enhances the spatial resolution by increasing the beam density 10 times compared with the Duoplasmatron source. Here we present high-spatial-resolution measurements of iron isotopes in pyrites using a 3 nA-3 μm primary 16 O- beam on two Cameca IMS 1280-HR2 ion microprobe instruments equipped with Hyperion sources at CRPG-IPNT (France) and at SwissSIMS (Switzerland). We tested analytical effects, such as topography and crystal orientation, that could induce analytical biases perceptible through variations of the instrumental mass fractionation (IMF). The δ56 Fe reproducibility for the Balmat pyrite standard is ±0.25‰ (2 standard deviations) and the typical individual internal error is ±0.10‰ (2 standard errors). The sensitivity on 56 Fe+ was 1.2 × 107 cps/nA/ppm or better. Tests on Balmat pyrites revealed that neither the crystal orientation nor channeling effects seem to significantly influence the IMF. Different pyrite standards (Balmat and SpainCR) were used to test the accuracy of the measurements. Indium mounts must be carefully prepared with a sample topography less than 2 μm, which was checked using an interferometric microscope. Such a topography is negligible for introducing change in the IMF. This new source increases the spatial resolution while maintaining the high precision of analyses and the overall stability of the measurements compared with the previous Duoplasmatron source. A reliable method was developed for performing accurate and high-resolution measurements of micrometric pyrites. The investigation of sedimentary micro-pyrites will improve our understanding of the processes and environmental conditions during pyrite precipitation, including the contribution of primary (microbial activities or abiotic reactions) and secondary (diagenesis and/or hydrothermal fluid circulation) signatures.

Performance and application of heavy ion nuclear microbeam facility at the Nuclear Physics Institute in Řež, Czech Republic

The Tandetron Laboratory of the Nuclear Physics Institute of the Czech Academy of Sciences is equipped with five beam lines associated with a 3 MV tandem electrostatic accelerator model 4130 MC from High Voltage Engineering Europa B.V. This accelerator is coupled with two duoplasmatron sources and a single sputter ion source and provides ions from hydrogen to gold. One of these lines is a nuclear microbeam facility, utilizing ion beams of micro- and sub-micro sizes for materials research by use of particle induced x-ray emission spectroscopy, particle induced gamma emission, Rutherford back-scattering spectroscopy, and scanning transmission ion microscopy methods as well as for ion beam writing. The major advantage of the presented microprobe is a possibility of 3D structure creation not only in polymer materials using light ions but also in other materials such as glass, ceramics, etc. by use of heavy ions. The focusing system allows focusing of charged particles with a maximum rigidity of 11 MeV amu/q2. The usual resolution in high and low current modes is 2 × 3 µm2 for a 100 pA and 0.3 × 0.5 µm2 for the 2000 ions/s of 2 MeV protons, respectively. A detailed facility description is given in the paper. The applications of focused beams of heavy ions as well as examples of light ions utilizing are also presented in the article.

Transport characteristics of space charge-dominated multi-species deuterium beam in electrostatic low-energy beam line

The transport characteristics of a space charge-dominated multi-species deuterium beam consisting of $$ D_{1}^{ + } $$ , $$ D_{2}^{ + } $$ , and $$ D_{3}^{ + } $$ particles in an electrostatic low-energy beam line are studied. First, the envelope equations of the primary $$ D_{1}^{ + } $$ beam are derived considering the space charge effects caused by all particles. Second, the evolution of the envelope of the multi-species deuterium beam is simulated using the PIC code TRACK, with the results showing a significant effect of the unwanted beam on the transport of the primary beam. Finally, different injected beam parameters are used to study beam matching, and a new beam extraction system for the existing duoplasmatron source is designed to obtain the ideal injected beam parameters that allow a $$ D_{1}^{ + } $$ beam of up to 50 mA to pass unobstructed through the electrostatic low-energy beam transport line in the presence of an unwanted ( $$ D_{2}^{ + } $$ , $$ D_{3}^{ + } $$ ) beam of 20 mA; at the same time, distortions of the beam emittance and particle distributions are observed.

High spatial resolution and high brightness ion beam probe for in-situ elemental and isotopic analysis

A high spatial resolution and high brightness ion beam from a cold cathode duoplasmatron source and primary ion optics are presented and applied to in-situ analysis of micro-scale geological material with complex structural and chemical features. The magnetic field in the source as well as the influence of relative permeability of magnetic materials on source performance was simulated using COMSOL to confirm the magnetic field strength of the source. Based on SIMION simulation, a high brightness and high spatial resolution negative ion optical system has been developed to achieve Critical (Gaussian) illumination mode. The ion source and primary column are installed on a new Time-of-Flight secondary ion mass spectrometer for analysis of geological samples. The diameter of the ion beam was measured by the knife-edge method and a scanning electron microscope (SEM). Results show that an O2- beam of ca. 5 µm diameter with a beam intensity of ∼5 nA and an O- beam of ca. 5 µm diameter with a beam intensity of ∼50 nA were obtained, respectively. This design will open new possibilities for in-situ elemental and isotopic analysis in geological studies.

A New Radio Frequency Plasma Oxygen Primary Ion Source on Nano Secondary Ion Mass Spectrometry for Improved Lateral Resolution and Detection of Electropositive Elements at Single Cell Level.

An important application field of secondary ion mass spectrometry at the nanometer scale (NanoSIMS) is the detection of chemical elements and, in particular, metals at the subcellular level in biological samples. The detection of many trace metals requires an oxygen primary ion source to allow the generation of positive secondary ions with high yield in the NanoSIMS. The duoplasmatron oxygen source is commonly used in this ion microprobe but cannot achieve the same quality of images as the cesium primary ion source used to produce negative secondary ions (C(-), CN(-), S(-), P(-)) due to a larger primary ion beam size. In this paper, a new type of an oxygen ion source using a rf plasma is fitted and characterized on a NanoSIMS50L. The performances of this primary ion source in terms of current density and achievable lateral resolution have been characterized and compared to the conventional duoplasmatron and cesium sources. The new rf plasma oxygen source offered a net improvement in terms of primary beam current density compared to the commonly used duoplasmatron source, which resulted in higher ultimate lateral resolutions down to 37 nm and which provided a 5-45 times higher apparent sensitivity for electropositive elements. Other advantages include a better long-term stability and reduced maintenance. This new rf plasma oxygen primary ion source has been applied to the localization of essential macroelements and trace metals at basal levels in two biological models, cells of Chlamydomonas reinhardtii and Arabidopsis thaliana.

Design and fabrication of a duoplasmatron extraction geometry and LEBT for the LANSCE H⁺ RFQ project.

The 750-keV H(+) Cockcroft-Walton at LANSCE will be replaced with a recently fabricated 4-rod Radio Frequency Quadrupole (RFQ) with injection energy of 35 keV. The existing duoplasmatron source extraction optics need to be modified to produce up to 35 mA of H(+) current with an emittance <0.02 π-cm-mrad (rms, norm) for injection into the RFQ. Parts for the new source have been fabricated and assembly is in process. We will use the existing duoplasmatron source with a newly designed extraction system and low energy beam transport (LEBT) for beam injection into the RFQ. In addition to source modifications, we need a new LEBT for transport and matching into the RFQ. The LEBT uses two magnetic solenoids with enough drift space between them to accommodate diagnostics and a beam deflector. The LEBT is designed to work over a range of space-charge neutralized currents and emittances. The LEBT is optimized in the sense that it minimizes the beam size in both solenoids for a point design of a given neutralized current and emittance. Special attention has been given to estimating emittance growth due to source extraction optics and solenoid aberrations. Examples of source-to-RFQ matching and emittance growth (due to both non-linear space charge and solenoid aberrations) are presented over a range of currents and emittances about the design point. A mechanical layout drawing will be presented along with the status of the source and LEBT, design, and fabrication.

Ion Beam Transport Simulations for the 1.7 MV Tandem Accelerator at the Michigan Ion Beam Laboratory

The Michigan Ion Beam Laboratory houses a 1.7 MV tandem accelerator. For many years this accelerator was configured to run with three ion sources: a TORoidal Volume Ion Source (TORVIS), a Duoplasmatron source and a Sputter source. In this article we describe an application we have created using the SIMION® code to simulate the trajectories of ion beams produced with these sources through the accelerator. The goal of this work is to have an analytical tool to understand the effect of each electromagnetic component on the ion trajectories. This effect is shown in detailed drawings. Each ion trajectory simulation starts at the aperture of the ion source and ends at the position of the target. Using these simulations, new accelerator operators or users quickly understand how the accelerator system works. Furthermore, these simulations allow analysis of modifications in the ion beam optics of the accelerator by adding, removing or replacing components or changing their relative positions.

Experimental optimization of beam quality extracted from a duoplasmatron proton ion source.

The LANSCE accelerator facility operates with two independent ion injectors for H(+) and H(-) particle beams. The H(+) ion beam is formed using a duoplasmatron source followed by a 750 keV Cockroft-Walton accelerating column. Formation of an optimal plasma meniscus is an important feature for minimizing beam emittance, and maximizing beam brightness. A series of experiments were performed to find the optimal combination of extraction voltage and extracted current for the H(+) beam. Measurements yielded the best ratio of beam perveance to Child-Langmuir perveance of 0.52 for maximizing beam brightness.

Use of a duoplasmatron ion source for negative ion generation

The use of electronegative species as primary ions considerably enhances the emission of positive secondary ions in SIMS. Considering furthermore that negative primary ions can be required due to instrumental configurations (e.g. the Cameca NanoSIMS 50 requires an opposite polarity of the primary and secondary ions), O − ion bombardment is employed in SIMS analysis. These O − ions are typically created in a duoplasmatron source, which suffers however from its low brightness and which is thus not suited for high resolution imaging applications. The development of new (electro)negative ion sources is thus necessary to optimize the analysis of electropositive elements in terms of lateral resolution and sensitivity. In this paper, we present the performance of a duoplasmatron ion source generating F −, Cl −, Br − and I − ion beams. In particular, we experimentally determine on a dedicated test bench the brightness of the source in the F −, Cl −, Br − and I − modes as a function of the gas pressure, the magnetic field strength and the arc current in the source. The obtained results are compared to the performances of the duoplasmatron in the standard O − mode. In this context, a five times higher brightness was found for F − (200 A/cm 2 sr) compared to the standard O − (42 A/cm 2 sr).

A zero-to-few-hundred eV proton beam for calibrations of neutron β decay experiments

We have constructed a system using a duoplasmatron source to produce a beam of low-energy (0 – few hundred eV) protons with the principal goal of testing and calibrating detectors used to detect protons from neutron β decay. The system is stable and produces beams by simply turning on the associated power supplies without the need of careful tuning. As an example we show data from calibration of a surface barrier detector in the emiT apparatus. Protons from the system were scattered from an Al target and used to calibrate detectors in the emiT apparatus.

New developments for shallow depth profiling with the Cameca IMS 6f

A new ion optical system has been developed for the duoplasmatron source of the Cameca IMS 6f instrument. This system improves performance at low impact energies. It consists of a new primary ion extraction system operating in acceleration/deceleration mode and an additional lens. It provides better source emittance matching with the primary column acceptance and a minimization of the space charge effect in the source plasma. The primary beam density in the sub-kilo-electron-volt impact energy range (down to 500 eV) is therefore improved. This article describes the new extraction system, the performance improvements are discussed in terms of beam intensity and density as a function of impact energy, and application examples for B and P shallow profiles are provided. Results demonstrating the benefits of the sample rotation technique for B depth profiling in silicon with low impact energy O2+ beam and oxygen flooding are also presented.

Angular and energy dependence of the ion beam oxidation of Si using oxygen ions from a duoplasmatron source

Oxygen ions with energy in the range 4–15 keV O+ were used to synthesize surface oxide layers by bombarding Si samples at different angles of incidence with respect to the surface normal. High-resolution Rutherford backscattering spectroscopy and channelling were used to determine both the stoichiometry and thickness of the surface oxides. In particular, the effect of energy on the critical angle for the formation of SiO2 was determined. The thickness of the oxide layers were also simulated using the PROFILE and TRIM codes. A stoichiometric oxide was obtained for angles of incidence of <25°, irrespective of the ion energy used. The critical angle for oxide formation was found to be largest for the highest ion energy. The thickness of SiO2 varies linearly with the ion energy, and correlates very well with PROFILE and TRIM code simulations. Copyright © 1999 John Wiley & Sons, Ltd.

Duoplasmatron source modifications for He+3 operation

A duoplasmatron ion source is used to produce 25 mA of He+3 with a pulse width of ∼80 ms at 360 Hz for acceleration to 10.5 MeV. At this energy, He3 striking water or carbon targets can produce short lived isotopes of C11, N13, O15, and F18 for medical positron emission tomography (PET). A duoplasmatron ion source was chosen originally since it is capable of a sufficient singly charged helium beam with an acceptable gas consumption. Stable long-term operation of the source required a change in the filament material to molybdenum, and a careful understanding of the oxide filament conditioning, operation and geometry. Other improvements, particularly in the electronics, were helpful to increasing the reliability. The source has operated for many months at ∼2.5% duty factor without significant problems and with good stability. We report here the effort that was done to make this source understandable and reliable.

Efficient negative-ion sources for tandem injection (invited)

Tandem-accelerator operation requires a source of negative ions. The earliest negative-ion sources were based on charge exchange of positive ions from a rf or duoplasmatron source. The development of the sputter-ion source in the 1970’s produced a revolutionary change in the number of negative-ion beams for Tandem operation. This article will review operational characteristics of sputter-ion sources coupled to large Tandem accelerators. These characteristics and matching of the ion source to the accelerator are determining factors for the production of useful beam intensities for physics experiments. A new approach using a 2.45 GHz microwave ion source to produce a high-quality, positive-ion beam coupled to a charge-exchange canal is being developed at Chalk River Laboratories, and some results of this development program will be presented. Plans for future development include the investigation of direct extraction of negative ions from a microwave-driven plasma.

Duoplasmatron ion source for proton and deuteron intense beams at low energy (abstract)

The duoplasmatron source was specially designed as a component of the hydrogen and deuterium negative polarized ion source, of Lamb–Shift type, for equipping the FN–Tandem Accelerator in Bucharest. The source can operate long-term at an arc power of 2.5 kW with an intensity of the arc current of 10–11 A. The duoplasmatron source anode is of a special construction in order to allow a strong cooling and a quick adaptation of some cups for the plasma expansion. Three variants of the extraction ion-optics configuration have been analyzed by computer and then experimentally carried out and tested. All the extraction ion-optics configurations employ plasma expansion cups and the process of deacceleration of the beam down to energies of 500–1000 eV is taking place inside of a magnetic lens. The proton and deuterium beam intensity obtained beyond the magnetic lens may exceed 10 mA, function of the discharge conditions in the arc and the ion-optics configuration employed. The ion composition of the beam (H1, H2, H3) function of the discharge parameters in the arc, has also been analyzed and the results showed that the percentage of the atomic ions is higher than 70%.

Review of high brightness ion sources for microlithography (invited)

The state of the art of high brightness ion beam production for microlithography and trends of research and development in this field of activity is reviewed. High brightness and low-energy spread are crucial to the success of ion-beam lithography. Features of field emission liquid metal, melted dielectric, and cryogenic gaseous ion sources for fine focused beam production are discussed. Growth of energy spread and the drop in brightness by intrabeam interaction of ions are estimated. Limitation of positive ion-beam characteristics in plasma sources such as duoplasmatron, multicusp, rf, and microwave discharges sources are examined. Features of negative ion formation in surface plasma sources with cesium catalysis are discussed. Possibilities for ions cooling down to 1 eV in high-density beams are estimated. High-precision beam diagnostics will be discussed.

The emerging plasma beam from a duoplasmatron source and the potential for material sputtering

The UMIST duoplasmatron provides high plasma particle emission rates in excess of 5*1017 S-1 and energetic stream conditions. Plasma ions are ejected with supersonic velocities. The expansion of the emerging hydrogen plasma and subsequent ion acceleration to mean energies of over 130 eV are modelled using a simple fluid description. A technique for exchanging hydrogen ions for argon in the expanding beam is demonstrated, giving energetic, heavy-ion stream conditions. The potential for using the duoplasmatron as a source of ions for direct sputtering of insulating materials is discussed.