Continuous Ion Beam Research Articles

Effective beam separation schemes for the measurement of the electric Aharonov–Bohm effect in an ion interferometer

We propose an experiment for the first proof of the type I electric Aharonov–Bohm effect in an ion interferometer for hydrogen. The performances of three different beam separation schemes are simulated and compared. The coherent ion beam is generated by a single atom tip (SAT) source and separated by either two biprisms with a quadrupole lens, two biprisms with an einzel-lens or three biprisms. The beam path separation is necessary to introduce two metal tubes that can be pulsed with different electric potentials. The high time resolution of a delay line detector allows to work with a continuous ion beam and circumvents the pulsed beam operation as originally suggested by Aharonov and Bohm. We demonstrate that the higher mass and therefore lower velocity of ions compared to electrons combined with the high expected SAT ion emission puts the direct proof of this quantum effect for the first time into reach of current technical possibilities. Thereby a high detection rate of coherent ions is crucial to avoid long integration times that allow the influence of dephasing noise from the environment. We can determine the period of the expected matter wave interference pattern and the signal on the detector by determining the superposition angle of the coherent partial beams. Our simulations were tested with an electron interferometer setup and agree with the experimental results. We determine the separation scheme with three biprisms to be most efficient and predict a total signal acquisition time of only 80s to measure a phase shift from 0 to 2π due to the electric Aharonov–Bohm effect.

Time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) using an ionic‐liquid primary ion beam source

An orthogonal acceleration time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) system has been developed using a prototype vacuum‐electrospay primary beam source that is capable of producing continuous ion beam of an ionic liquid. As a primary ion beam, an imidazolium ionic liquid, 1‐ethyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl) amide (EMI‐TFSA), was electrosprayed at pressures around 2 × 10−4 Pa and a flow rate of 50 nL/min. Using the TOF‐SIMS system, three samples were analyzed: (i) EMI‐TFSA, (ii) an ammonium ionic liquid, N,N‐diethyl‐N‐methyl‐N‐(2‐methoxyethyl)ammonium bis(trifluoromethanesulfonyl) amide (DEME‐TFSA), and (iii) a polyethylene glycol (PEG300). Preliminary data showed that the vacuum electrospray of the ionic liquid was applicable to a primary ion beam source for SIMS. Nevertheless, irradiation of the ionic‐liquid beam caused deposition as well as sputtering. The deposition would result from larger m/z components of ionic‐liquid charged droplets. This is because projectile energy per nucleon of the larger m/z components seems too low to sputter materials. Because m/z values of charged droplets decrease with decreasing flow rate, it is required to reduce the flow rate of the ionic liquid so as to suppress the deposition of the ionic‐liquid beam. Copyright © 2014 John Wiley & Sons, Ltd.

Spatiotemporal lipid profiling during early embryo development of Xenopus laevis using dynamic ToF-SIMS imaging

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging has been used for the direct analysis of single intact Xenopus laevis embryo surfaces, locating multiple lipids during fertilization and the early embryo development stages with subcellular lateral resolution (∼4 μm). The method avoids the complicated sample preparation for lipid analysis of the embryos, which requires selective chemical extraction of a pool of samples and chromatographic separation, while preserving the spatial distribution of biological species. The results show ToF-SIMS is capable of profiling multiple components (e.g., glycerophosphocholine, SM, cholesterol, vitamin E, diacylglycerol, and triacylglycerol) in a single X. laevis embryo. We observe lipid remodeling during fertilization and early embryo development via time course sampling. The study also reveals the lipid distribution on the gamete fusion site. The methodology used in the study opens the possibility of studying developmental biology using high resolution imaging MS and of understanding the functional role of the biological molecules.

Serial mode combined polishing of high-quality flat mirror

In order to obtain high-quality flat mirror, a serial mode combined polishing technology, consisting of continuous polishing (CP) and ion beam figuring (IBF), is presented. The function of CP technology is to get certain figure accuracy and meet the requirements of the surface roughness of the flat mirror. The final high figure accuracy of the flat mirror is achieved by the IBF technology. We introduce the polishing principles of CP and IBF and then, the polishing experiment and material removal function of IBF are studied. Finally, a 160 mm flat mirror is polished by a serial mode combined polishing technology. After serial mode combined polishing, the surface error and roughness of the flat mirror are 2.06 and 0.42 nm RMS, respectively. The experiment results indicate that the serial mode combined polishing technology is effective for polishing ultra-precise flat mirror.

纳米级面形精度光学平面镜加工

In order to polish optical flat mirror with nanometer surface error efficiently,a consisting of new polishing technology traditional continuous polishing( CP) and advanced ion beam figuring( IBF) is presented in this paper. The polishing principles of CP and IBF are introduced. The polishing experiment and material removal function of IBF are studied. A Ф150 mm optical flat mirror is polished by the combined polishing technology. After polishing,the surface error and roughness of the flat mirror are 1. 217 nm RMS and0. 506 nm RMS,respectively. The experiment results indicate that the combined polishing technology is effective for polishing optical flat mirror with nanometer surface error.

Modulation of continuous ion beams with low drift velocity by induced wakefield in background plasmas

AbstractTwo-dimensional particle-in-cell simulations are performed to investigate the propagation of low energy continuous ion beams through background plasmas. It is shown that the continuous ion beam can be modulated into periodic short beam pulses by the induced wakefield, which can be adopted as a method to produce ultrashort ion beam pulses. Furthermore, the transport of the continuous ion beam in plasma with density gradient in the beam propagation direction is proposed and an enhanced longitudinal compression by density gradient is found due to the phase lock of ion pulses in the focusing regions of wakefield and reduced heating of plasma electrons.

Comparison of C60 and GCIB primary ion beams for the analysis of cancer cells and tumour sections

We have implemented a gas cluster ion beam (GCIB) system developed by Ionoptika Ltd (Southampton, UK) with sufficient control to allow us to exploit the unique capabilities of our J105 instrument for imaging and depth profiling. The J105 allows us to use the GCIB as continuous primary ion beam, thereby overcoming the issues associated with pulsing these slow moving, mixed species beams. We have performed a direct comparison with C60 ions on the same samples in the same instrument. The GCIB beams are more difficult to focus than the C60+ ion beam, making single‐cell imaging difficult, although spot sizes of 15–20 µm are readily obtainable for Ar1000 and Ar2000, providing good resolution for larger area imaging on tissue section/biopsy samples. In this paper, we present results from the assessment of these new beams as primary ions for the analysis of ‘real’, complex biological systems. Initial spectra and those following increased primary ion bombardment were compared for in vitro cultured cells deposited on silicon and cryo‐sectioned tumour samples originating in vivo. Ar1000+ and Ar2000+ showed increased persistence of the signals from intact molecular ions of phospholipids and a reduction in the accumulation of chemical background noise compared with C60+ analysis. Copyright © 2012 John Wiley & Sons, Ltd.

Time‐of‐Flight secondary ion mass spectrometry (TOF‐SIMS) using the metal‐cluster‐complex primary ion of Ir4(CO)7+

AbstractAn orthogonal acceleration Time‐of‐Flight Secondary Ion Mass Spectrometer (TOF‐SIMS) system has been developed with a metal‐cluster‐complex ion source. The ion source can produce ion beams of massive molecules called metal‐cluster‐complexes such as Ir4(CO)12, which has a molecular weight higher than 1000 u. Using the system, TOF‐SIMS of a contaminated silicon substrate and a room temperature molten salt (i.e. an ionic liquid) was performed. The ionic liquid N,N‐diethyl‐N‐methyl‐N‐(2‐methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide, which has a molecular weight of 426 u, consists of a polyatomic cation, [C8H20ON]+, and a polyatomic anion, [C2F6NO4S2]−. During SIMS analysis, an analytical sample was bombarded with a continuous primary ion beam of either Ir4(CO)7+ or Ar+ in a beam energy of 10 keV at an incident angle of 45°. It was confirmed that the use of Ir4(CO)7+ ions enhanced secondary ion intensity compared with that of Ar+ ions. Also, experimental results showed that the bombardment of Ir4(CO)7+ caused less fragmentation. In the case of the ionic liquid, cation‐attached ionic‐liquid molecules were observed in addition to the cation of the ionic liquid. Copyright © 2010 John Wiley & Sons, Ltd.

The response of silicon detectors to low-energy ion implantation

Studies of electrical transients in single-crystal silicon induced by discrete low-energy(sub-20 keV) ions have been carried out at 90 K, with ionization measurements and damageaccumulation in the sample being investigated. Ionization studies reveal a discrepancybetween experimental results and predictions from the widely used SRIM (stopping andrange of ions in matter) code, one which increases with decreasing energy: a result whichhas previously been suggested from studies with continuous ion beams. Damageaccumulation studies of the sample also demonstrate that current models of damagebuild-up in silicon are inadequate at such low energies, with experiments indicatingthat individual ions create a much larger region of decreased charge collectionefficiency outside of the small amorphous cores known to be formed by such impacts.

Enhanced Ion Utilization Efficiency Using an Electrodynamic Ion Funnel Trap as an Injection Mechanism for Ion Mobility Spectrometry

Conventional ion mobility spectrometers that sample ion packets from continuous sources have traditionally been constrained by an inherently low duty cycle. As such, ion utilization efficiencies have been limited to <1% in order to maintain instrumental resolving power. Using a modified electrodynamic ion funnel, we demonstrated the ability to accumulate, store, and eject ions in conjunction with ion mobility spectrometry (IMS), which elevated the charge density of the ion packets ejected from the ion funnel trap (IFT) and provided a considerable increase in the overall ion utilization efficiency of the IMS instrument. A 7-fold increase in signal intensity was revealed by comparing continuous ion beam current with the amplitude of the pulsed ion current in IFT-IMS experiments using a Faraday plate. Additionally, we describe the IFT operating characteristics using a time-of-flight mass spectrometer attached to the IMS drift tube.

Time-of-flight radio-frequency mass separator for continuous low-energy ion beams

A novel concept for a time-of-flight radio-frequency mass separator for low-energy beams is investigated. The concept is based on two sets of deflectors with sinusoidally-varying applied voltage and at least one Einzel lens. Results of analytical calculation and numerical simulation are presented and compared. Potential advantages of such a scheme include a resolving power similar to that of simple electromagnetic separators while at lower costs, as well as the possibility to incorporate the scheme relatively easily into existing electrostatic beam transport systems.

Compact Ultrafast Orthogonal Acceleration Time-of-Flight Mass Spectrometer for On-Line Gas Analysis by Electron Impact Ionization and Soft Single Photon Ionization Using an Electron Beam Pumped Rare Gas Excimer Lamp as VUV-Light Source

Orthogonal acceleration time-of-flight mass spectrometers (oaTOFMS), which are exhibiting a pulsed orthogonal extraction of ion bunches into the TOF mass analyzer from a continuous primary ion beam, are well-suited for continuous ionization methods such as electron impact ionization (EI). Recently an electron beam pumped rare gas excimer lamp (EBEL) was introduced, which emits intensive vacuum UV (VUV) radiation at, e.g., 126 nm (argon excimer) and is well suited as the light source for soft single photon ionization (SPI) of organic molecules. In this paper, a new compact oaTOFMS system which allows switching between SPI, using VUV-light from an EBEL-light source, and conventional EI is described. With the oaTOFMS system, EBEL-SPI and EI mass spectral transients can be recorded at very high repetition rates (up to 100 kHz), enabling high duty cycles and therefore good detection efficiencies. By using a transient recorder card with the capability to perform on-board accumulation of the oaTOF transients, final mass spectra with a dynamic range of 106 can be saved to the hard disk at a rate of 10 Hz. As it is possible to change the ionization modes (EI and SPI) rapidly, a comprehensive monitoring of complex gases with highly dynamic compositions, such as cigarette smoke, is possible. In this context, the EI based mass spectra address the bulk composition (compounds such as water, oxygen, carbon dioxide, etc. in the up to percentage concentration range) as well as some inorganic trace gases such as argon, sulfur dioxide, etc. down to the low ppm level. The EBEL-SPI mass spectra on the other hand are revealing the organic composition down to the lower ppb concentration range.

Chemical modification of the poly(vinylidene fluoride-trifluoroethylene) copolymer surface through fluorocarbon ion beam deposition

Classical molecular dynamics simulations are used to study the effects of continuous fluorocarbon ion beam deposition on a poly(vinylidene fluoride-trifluoroethylene) [P(VDF-trFE)] surface, a polymer with electromechanical properties. Fluorocarbon plasma processing is widely used to chemically modify surfaces and deposit thin films. It is well accepted that polyatomic ions and neutrals within low-energy plasmas have a significant effect on the surface chemistry induced by the plasma. The deposition of mass selected fluorocarbon ions is useful to isolate the effects specific to polyatomic ions. Here, the differences in the chemical interactions of C3F5+ and CF3+ ions with the P(VDF-trFE) surface are examined. The incident energy of the ions in both beams is 50eV. The CF3+ ions are predicted to be more effective at fluorinating the P(VDF-trFE) surface than C3F5+ ions. At the same time, the C3F5+ ions are predicted to be more effective at growing fluorocarbon thin films. The simulations also reveal how the d...

Thermal Lensing in a Supercritical Water Medium

A pulsed, two-beam, thermal lensing experiment was performed to determine the concentration of aqueous solutes above the critical point of water. Despite a very significant mirage effect due to thermal gradients in the cell and absorption by water itself, the thermal lensing signal strength for aqueous benzoic acid in supercritical water was found to be linear with concentration in the sub-millimolar range. Although thermal lensing experiments in aqueous media are notoriously insensitive, the sharp density gradient near the critical point considerably improves the signal intensity. In this study a short-pulse pump 266 nm YAG laser and continuous low-power probe Ar ion beam were both focused into a supercritical water cell, giving a lensing signal whose strength could be maximized by changing the overlap of the two beams.

The LPCTrap facility: A novel transparent Paul trap for high-precision experiments

A trap system has been built to perform high-precision β -decay experiments. The system is coupled to the low-energy beam line of the SPIRAL source at GANIL. The continuous ion beam from SPIRAL with energies between 10 and 20 keV is slowed down by means of a buffer-gas-filled RFQ trap and ejected thereafter as short ion bunches into a novel transparent Paul trap. Two pulsed cavities located downstream from the RFQ reduce the energy of the ion bunch down to about a hundred eV for an efficient capture in the Paul trap. We describe here the complete system along with the first results obtained with stable He + 4 , Cl + 35 and Ar + 36 , 40 ions from the SPIRAL ECR source. An overall efficiency of 8.7 ( 8 ) × 10 - 4 is achieved for 4 He + ions under specific conditions.

Development of a ToF version of the desktop MiniSIMS utilising a continuous primary ion beam

The Millbrook MiniSIMS remains a unique concept in SIMS instrumentation. An upgraded version of the MiniSIMS based on a time-of-flight (ToF) mass spectrometer has now been developed. Unlike the vast majority of ToFSIMS instruments, the ToF MiniSIMS uses a continuous primary ion beam and a pulsed secondary ion beam. The instrument has the usual ToF attributes of parallel mass detection, extended mass range and higher mass resolution, but also features a high duty cycle. The result is very fast data acquisition, especially in imaging mode. Moreover, in depth profiling, a continuous beam allows all sputtered material to contribute to the analysis by eliminating the requirement for cycling between etching and analysis modes. The combination of a ToF spectrometer and a continuous primary beam is thus ideally suited to the MiniSIMS concept of a high-throughput instrument able to acquire spectra, images and depth profiles. The higher performance opens up new applications for the MiniSIMS instrument in the identification of organic materials and small area analysis, especially for materials with largely unknown composition or depth distribution.

Negative ion yield in long pulse operation of the KAMABOKO III source

In Cadarache development on negative ion sources is being carried out on the KAMABOKO III ion source on MANTIS in collaboration with JAERI, Japan. The target performance indicated in the ITER R&D task description is to accelerate a D − beam, with a current density of 200 A/m 2 and <1 electron extracted per accelerated D − ion, at an injected power ranging between 1 and 2 kW l −1 of source volume, and a source pressure of 0.3 Pa. For ITER a continuous ion beam must be assured for pulse lengths of up to 3600 s. Experiments on MANTIS have shown 1000 s operation, however the current density was lower than anticipated, with transmission to the calorimeter as low as 50%. Investigations into the effect of the temperature of the plasma grid on the negative ion yield have been carried out, with increases of ≤40% observed during long pulse operation, substantially below the expected 100%, demonstrated in short pulse operation. A model of the dynamic behaviour of the Cs in the source was proposed and subsequently investigated. Results from these experiments suggest that the Cs injected into the source is rendered unusable due to its “burial” under tungsten evaporated from the filaments.

Ge/Si quantum dot nanostructures grown with low-energy ion beam-assisted epitaxy

Scanning tunneling microscopy (STM) and reflection high-energy electron diffraction (RHEED) experiments were performed to study growth modes induced by hyperthermal Ge + ion action during molecular beam epitaxy (MBE) of Ge on Si(100). The continuous and pulsed ion beams were used. These studies have shown that ion beam bombardment during heteroepitaxy leads to decrease in critical film thickness for transition from two-dimensional (2D) to three-dimensional (3D) growth modes, enhancement of 3D island density, and narrowing of island size distribution, as compared with conventional MBE experiments. Moreover, it was found that ion beam assists the transition from hut- to dome-shaped Ge islands on Si(100). The crystal perfection of Ge/Si structures with Ge islands embedded in Si was analyzed by Rutherford backscattering/channeling technique (RBS) and transmission electron microscopy (TEM). The studies of Si/Ge/Si(100) structures indicated defect-free Ge nanopaticles and Si layers for the initial stage of heteroepitaxy (five monolayers of Ge) in pulsed ion beam action growth mode at 350 °C. Continuous ion beam irradiation was found to induce dislocations around Ge clusters. The results of kinetic Monte Carlo (KMC) simulation have shown that two mechanisms of ion beam action can be responsible for stimulation of 2D–3D transition: (1) surface defect generation by ion impacts, and (2) enhancement of surface diffusion.

Advances in coated conductor development at SRL-Nagoya Coated Conductor Center

In order to fabricate long and high critical current coated conductors, new facilities for a continuous ion-beam assisted deposition (IBAD) and a pulsed laser deposition (PLD) were installed at SRL-Nagoya Coated Conductor Center (NCCC). We found a PLD-CeO 2 cap layer deposited on an IBAD Gd–Zr-oxide (GZO) layer realized quite high grain alignment as well as much higher deposition rate than the conventional IBAD process, and we call this phenomenon “self-epitaxy”. Thus, the CeO 2 cap layer enables an IBAD-buffer layer to be thinner, resulted in faster production speed than the conventional IBAD process. Using these facilities, we have accelerated the development of long coated conductors. A 105-m long IBAD tape and a 55-m long CeO 2 cap layer with high grain alignment were fabricated. A high critical current density of 0.96 MA/cm 2 at 77 K was obtained in the continuously deposited YBCO films with a reel-to-reel process on the self-epitaxial PLD-CeO 2 capped IBAD-GZO layers as well as those in short samples. Long YBCO conductor fabrication using the reel-to-reel PLD equipments is now undergoing.

MODIFICATION OF GROWTH MODE OF Ge ON Si BY PULSED LOW-ENERGY ION-BEAM IRRADIATION

Scanning tunneling microscopy (STM) and reflection high-energy electron diffraction (RHEED) experiments were performed to study growth modes induced by hyperthermal Ge + ion action during molecular beam epitaxy (MBE) of Ge on Si (100). The continuous and pulsed ion beams were used. These studies have shown that ion-beam bombardment during heteroepitaxy leads to decrease in critical film thickness for transition from two-dimensional (2D) to three-dimensional (3D) growth modes, enhancement of 3D island density and narrowing of island size distribution, as compared with conventional MBE experiments. The crystal perfection of Ge / Si structures with Ge islands embedded in Si was analyzed by Rutherford backscattering/channeling technique (RBS) and transmission electron microscopy (TEM). The results of Kinetic Monte Carlo (KMC) simulation have shown that two mechanisms of ion beam action can be responsible for stimulation of 2D–3D transition. They are: (1) surface defect generation by ion impacts and (2) enhancement of surface diffusion.