Multiple Charged Ions Research Articles

New development of laser ion source for highly charged ion beam production at Institute of Modern Physics (invited)

A laser ion source based on Nd:YAG laser has been being studied at the Institute of Modern Physics for the production of high intensity high charge state heavy ion beams in the past ten years, for possible applications both in a future accelerator complex and in heavy ion cancer therapy facilities. Based on the previous results for the production of multiple-charged ions from a wide range of heavy elements with a 3 J/8 ns Nd:YAG laser [Zhao et al., Rev. Sci. Instrum. 85, 02B910 (2014)], higher laser energy and intensity in the focal spot are necessary for the production of highly charged ions from the elements heavier than aluminum. Therefore, the laser ion source was upgraded with a new Nd:YAG laser, the maximum energy of which is 8 J and the pulse duration can be adjusted from 8 to 18 ns. Since then, the charge state distributions of ions from various elements generated by the 8 J Nd:YAG laser were investigated for different experimental conditions, such as laser energy, pulse duration, power density in the focal spot, and incidence angle. It was shown that the incidence angle is one of the most important parameters for the production of highly charged ions. The capability of producing highly charged ions from the elements lighter than silver was demonstrated with the incidence angle of 10° and laser power density of 8 × 10(13) W cm(-2) in the focal spot, which makes a laser ion source complementary to the superconducting electron cyclotron resonance ion source for the future accelerator complex especially in terms of the ion beam production from some refractory elements. Nevertheless, great efforts with regard to the extraction of intense ion beams, modification of the ion beam pulse duration, and reliability of the ion source still need to be made for practical applications.

Statistical mechanics of dust charging in a multi-ion plasma with negative and positive ionic species

On the basis of statistical mechanics and charging kinetics, the charge distribution over uniform size spherical dust particles in a multi-ion plasma comprising of multiple charged negative and positive ions is investigated. Two specific situations where the complex plasma is viz., (i) dark (no emission from dust) and (ii) irradiated by laser light (causing photoemission from dust) have been taken into account. The analytical formulation includes the population balance equation for the charged dust particles along with number and energy balance of the complex plasma constituents. The departure of the results for multi-ion plasma from that in case of usual singly charged positive ion plasma is graphically illustrated and discussed. In contrast to electron-ion plasma, significant number of particles is seen to acquire opposite charge in case of pure positive-negative ion plasma, even in the absence of electron emission from the dust grains. The effects of various plasma parameters viz., number density, particle size, and work function of dust on charge distribution have also been examined.

Gravitational radiation as radiation same level of electromagnetic and its generation in pulsed high-current discharge

The notion of gravitational radiation as a radiation of the same level as the electromagnetic radiation is based on theoretically proved and experimentally confirmed fact of existence of stationary states of an electron in its gravitational field characterized by the gravitational constant K = 1042G (G is the Newtonian gravitational constant) and unrecoverable space-time curvature A. This paper gives an overview of the authors' works [1, 2, 3, 4], which set out the relevant results. Additionally, data is provided on the broadening of the spectra characteristic radiation. The data show that this broadening can be explained only by the presence of excited states of electrons in their gravitational field. What is more, the interpretation of the new line of X-ray emission spectrum according to the results of observation of MOS-camera of XMM-Newton observatory is of interest. The given work contributes into further elaboration of the findings considering their application to dense high- temperature plasma of multiple-charge ions. This is due to quantitative character of electron gravitational radiation spectrum such that amplification of gravitational radiation may take place only in multiple-charge ion high-temperature plasma.

Nanosecond laser induced energetic ion formation from a nanoparticle: The origin of ion detection loss in a single particle mass spectrometry

Here we study the interaction of a nanosecond laser pulse with a nanoparticle to explore the mechanism of energetic ion formation and in particular the particle size dependence. Multiphoton ionization and the subsequent electron impact ionization accompanied by inverse Bremsstrahlung process are determined appropriate for generation of multiple charged ions. The Coulomb expansion of a positive ion cloud is then calculated with molecular dynamics simulations, resulting in temporal evolution of ions, a radial distribution of kinetic energy of ions, and size-dependency of the ion kinetic energy. A mass spectrum peak of ion simulated by the present model is found comparable to the experimental data. Alternatively, a direct measurement of kinetic energy is also explained by the model.

Design study of electron cyclotron resonance-ion plasma accelerator for heavy ion cancer therapy

Electron Cyclotron Resonance-Ion Plasma Accelerator (ECR-IPAC) device, which theoretically can accelerate multiple charged ions to several hundred MeV with short acceleration length, has been proposed. The acceleration mechanism is based on the combination of two physical principles, plasma electron ion adiabatic ejection (PLEIADE) and Gyromagnetic Autoresonance (GYRAC). In this study, we have designed the proof of principle machine ECR-IPAC device and simulated the electromagnetic field distribution generating in the resonance cavity. ECR-IPAC device consisted of three parts, ECR ion source section, GYRAC section, and PLEIADE section. ECR ion source section and PLEIADE section were designed using several multi-turn solenoid coils and sextupole magnets, and GYRAC section was designed using 10 turns coil. The structure of ECR-IPAC device was the cylindrical shape, and the total length was 1024 mm and the maximum diameter was 580 mm. The magnetic field distribution, which maintains the stable acceleration of plasma, was generated on the acceleration center axis throughout three sections. In addition, the electric field for efficient acceleration of electrons was generated in the resonance cavity by supplying microwave of 2.45 GHz.

Thermonuclear Plasma Steady States Generation

This report is a systematic and complemented summary of the earlier published works by the authors [1-4]. The concept of gravitational radiation as a radiation of one level with the electromagnetic radiation is based on theoretically proved and experimentally confirmed fact of existence of electron’s stationary states in own gravitational field, characterized by gravitational constant K = 1042 G (G—Newtonian gravitational constant) and by irremovable space-time curvature. The received results strictly correspond to principles of the relativistic theory of gravitation and the quantum mechanics. The given work contributes into further elaboration of the findings considering their application to dense high-temperature plasma of multiple-charge ions. This is due to quantitative character of electron gravitational radiation spectrum such that amplification of gravitational radiation may take place only in multiple-charge ion high-temperature plasma.

Multispecies focused ion beam lithography system and its applications

The authors present a focused ion beam lithography (IBL) instrument and its extension toward using different ion species beyond gallium. The base instrument utilizes a lithography architecture and an ion source and column dedicated to nanofabrication. This includes large area navigation and patterning by a laser interferometer stage, long-term beam to sample positional as well as beam current stability and automation capabilities. Since the ion type can have dramatic consequences on the resulting nanostructures, the authors have extended the gallium IBL tool's ion column and source toward the stable delivery of multiple species for a nanometer scale focused ion beam based on a liquid metal alloy ion source. The IBL system is equipped with an E × B mass filter capable of selecting different single and multiple charged ion species, simultaneously originating from the same source. The authors investigated different AuSi or AuGe based sources and in particular an ion source delivering Au, Si and Be focused ion beams regarding beam current stability, beam diameter and patterning performance. Depending on the ion species and the interaction with the sample material, the authors achieved sub-20 nm results both for beam diameter and minimum line width by direct milling. The alloy ion sources show stability comparable to gallium during measurements over 10–20 h and a lifetime of several months. Initial and potential applications in the field of selective graphene synthesis, membrane and nanopore patterning as well as photonics and plasmonics are discussed.

Algorithm-based modelling of fractional ion abundance and rates of ionization and recombination for tungsten plasmas

The fractional ion abundance and rates of ionization and recombination of multiple charged tungsten ions in magnetic fusion plasmas are investigated using a collisional radiative model. Using a computer algorithm to generate a set of atomic states to be included in the collisional radiative model, the dominant dielectronic recombination and excitation autoionization channels are determined by a systematic convergence analysis of the level population and ion abundance with respect to the size of the model. The atomic data, such as energy levels and rates of the radiative decay as well as autoionization, are obtained by the ab initio calculation using the Hebrew University Lawrence Livermore Atomic Code. The calculations are carried out in the temperature range of 100 eV–5 keV, and the ratio between the abundances of W44 + and W45 + ions agrees well with an experimental result obtained without any artificial adjustment of the atomic rates.

Salicylaldehyde azine cluster formation observed by cold‐spray ionization mass spectrometry

We installed a cold-spray ionization (CSI) source on a mass spectrometer to investigate the self-assembly behavior of an aggregation-induced emission enhancement system. Using a CSI source and the three-dimensional platform, a self-assembly system of a salicylaldehyde azine (SAA) was studied in mixture solution. This method permitted the determination of the structural information of the solution state, which cannot be detected by conventional mass spectrometry. In addition to the [M+H](+) ion (M is the SAA molecule), many major ion clusters such as [2M+Na](+) at m/z 503, [3M+Na](+) at m/z 743, [4M+Na](+) at m/z 983 and higher order aggregates were observed in the CSI mass spectra. However, many fragment ions, with the exception of cluster ions, appeared with high abundance when the ESI ion source was used due to the desolvation chamber temperature, suggesting that some aggregation can be detected at low temperatures. To investigate the effect of solvent on the aggregation, the CSI-mass spectrometry (MS) experiments of SAA in absolute ethanol solution and ethanol/water (good/poor solvent) mixture solution were conducted. The most abundant ion peak was protonated SAA (m/z 241) in absolute ethanol, but many cluster ions and some multiple charged ion peaks were observed after adding a small amount of water into the ethanol solution. The results showed good agreement with that inferred by the combinational analysis of scanning electron microscope and fluorescence microscopy, indicating that CSI-MS is capable of providing self-assembly information of labile molecules in the solution state.

Matrix Assisted Ionization Vacuum (MAIV), a New Ionization Method for Biological Materials Analysis Using Mass Spectrometry

The introduction of electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) for the mass spectrometric analysis of peptides and proteins had a dramatic impact on biological science. We now report that a wide variety of compounds, including peptides, proteins, and protein complexes, are transported directly from a solid-state small molecule matrix to gas-phase ions when placed into the vacuum of a mass spectrometer without the use of high voltage, a laser, or added heat. This ionization process produces ions having charge states similar to ESI, making the method applicable for high performance mass spectrometers designed for atmospheric pressure ionization. We demonstrate highly sensitive ionization using intermediate pressure MALDI and modified ESI sources. This matrix and vacuum assisted soft ionization method is suitable for the direct surface analysis of biological materials, including tissue, via mass spectrometry.

Construction of a collisional radiative model of complex multiple charged ions for mid- to high-Z elements

A method of constructing a compact and complete collisional radiative model of multiple charged ions of mid- to high-Z elements is proposed, for studying radiative properties of the plasmas. The proposed tungsten model, which is based on atomic data calculated by the HULLAC code, incorporates a computer algorithm to identify well-populated atomic states and dielectronic recombination channels that have a significant effect on the ionization balance. The model is validated by investigating the convergence of the mean charge and radiative power loss with respect to the size of the model, and by comparing results with other calculations presented at the nLTE kinetics workshop.

Method of Forming Stable States of Dense High-Temperature Plasma

The concept of gravitational radiation as a radiation of one level with the electromagnetic radiation is based on theoretically proved and experimentally confirmed fact of existence of electron’s stationary states in own gravitational field, characterized by gravitational constant K = 1042 G (G-Newtonian gravitational constant) and by irremovable space-time curvature. The received results strictly correspond to principles of the relativistic theory of gravitation and the quantum mechanics. The given work contributes into further elaboration of the findings considering their application to dense high-temperature plasma of multiple-charge ions. This is due to quantitative character of electron gravitational radiation spectrum such that amplification of gravitational radiation may take place only in multiple-charge ion high-temperature plasma. In elaboration of the authors’ works [1-4], an essential instantiation of the concept of fusion plasma’s steady states formation (as the last paragraph outlines) and boundary conditions refinement in the electron’s stationary-states-in-proper-gravitational-field problem are appended to this article.

Validation of Collisional Radiative Model of High-Z Multiple Charged Ions at NLTE Code Comparison Workshops

We develop a collisional radiative (CR) model of high-Z multiple charge ions based on computational atomic data. We use an algorithm to determine a set of atomic energy levels in the model with significant population in the plasmas and contribute to the dielectronic recombination (DR) processes. The model is validated through participation to the non-LTE kinetics workshops. At the nLTE workshop, an alternative method for the analysis of the spectrum from plasmas based on genetic algorithm (GA) is also discussed. An application of the present model to calculate the ion abundance and radiative power loss of Gd and Nd plasmas is also shown.

The fundamental determining factor of angular emission of multiple charged ions ejected by laser ablation of different metals and their binary alloys

Ions up to ionization state q = 4, emitted from laser produced plasma of Al, Ti, Ti50Al50 and Ti75Al25 targets ablated by Srivastava et al. (2006), are distributed angularly in the form of a cone, and for each ionization state the angular distribution has been shown to follow the cosine power-law: F = Focosnθ. It is found that the value of exponent n of cosnθ distribution function increases with the increase in ionization state. For each target, the value of exponent n of individual ionization states as well as total charge exhibits an excellent linear correlation with the room temperature Debye–Waller thermal parameter B or the mean-square amplitude of the atomic vibrations <u2> of the targets. It is further reported that the FWHM of ion distribution with Gaussian function fitting done by Srivastava et al. (2006) also depends linearly on B rather better than its dependence on the atomic mass of pure metal targets or average atomic mass in the case of their binary alloy targets. The FWHM of ion distribution for Al, Ti, Cu, Mo, W and their alloys Ti25Al75, Ti34Al66, Ti50Al50, Ti75Al25, W60Cu40, W80Cu20, W90Cu10 and Mo70Cu30 laser ablated by Srivastava and Rohr (2005) are also found to have much better correlation with the room temperature Debye–Waller thermal parameter B as compared to the atomic mass of the target.

Laser Radiation Effects on Adenine

Laser interaction whitthe gas phase nucleobase adenine is studied. A linear TOF mass spectrometer is utilized for measurements that require high mass resolution, high sensitivity, and sufficient ion yields of low mass fragment cations. The ion mass spectra are discussed at different laser energy intensities and two temperatures. In contrast to previous studies a number light ion is present in the mass spectra. The ion formation curves for 23 different ions are measured for the laser energy range from about 109 to 1010 W cm–2 and masses between 1 and 43 besides mass 57 which was present in the mass spectra and will be discuss. Data were taken heating the sample at 235 Co. The number of 355nm absorbed photons was calculated accordingly to Keldysh theory and similar results were found using adenine -Ar mixture. Our results are compared with those reported formed by protons, electrons or multiple charged ions interactions. Different ions were found indicating the possible effect of multiphoton absorption.

Boundary-Activated Dissociation in a Low Pressure Linear Quadrupole Ion Trap in the Presence of Nonlinear DC Fields

Boundary-Activated Dissociation (BAD) of multiple charge ions has been investigated in a low pressure linear ion trap (LIT) in the presence of nonlinear DC fields. Nonlinear DC fields allowed ions to be stored for a long duration at working points beyond the βy = 0 stability boundary of the regular quadrupole fields. The ions reached large stable radial amplitude trajectories gaining high kinetic energies from the drive RF field. This led to collision activation and the formation of fragments. Experimental and simulation data showed that the degree of fragmentation was strongly dependent on the q value, Mathieu stability parameter, and the strengths of nonlinear fields. In the absence of the nonlinear fields the fragmentation efficiency was 0% at q = 0.23 and 17% at q = 0.4. In the presence of nonlinear fields BAD efficiency increased to up to 94% at q = 0.23 and 84% at q = 0.4. The broadening of the stability diagram at the βy = 0 boundary also enabled the observation of fragment ions with higher mass-to-charge ratios (m/z) than the m/z of the precursor ions thus overcoming a major drawback of BAD of multiple-charged ions.

Source for extreme ultraviolet lithography based on plasma sustained by millimeter-wave gyrotron radiation

An extreme-ultraviolet (EUV) source based on a low-pressure discharge sustained in a magnetic trap by the high-power millimeter-wave radiation under electron-cyclotron-resonance (ECR) conditions is discussed. Multiple charged ions are efficiently generated and excited in such a discharge (tin ions injected into the trap from a vacuum-arc discharge were used) and emit line radiation in the desired wavelength range. A radiation power of 50 W into a solid angle of 4π sr in a wavelength range of 13.5 nm±1% and an efficiency of about 1% for the conversion of the microwave radiation absorbed in the plasma to the extreme ultraviolet radiation were achieved in the preliminary experiments. The article describes in detail the method of measuring EUV light emission power and background radiation. The emissivity of the plasma heated by gyrotron radiation with frequencies of 170 and 300 GHz is calculated. The proposed scheme can reduce the size of the emitting region up to ∼ 1 mm. The source can operate in both continuous and in pulsed mode.

Use of carbohydrase to enhance protein extraction efficiency and antioxidative properties of oat bran protein hydrolysates

In this study, medium oat bran samples were treated with four cell wall carbohydrases degrading enzymes (viscozyme® L, α-amylase, amyloglucosidase, celluclast®). Their effects on protein extraction efficiency and, on antioxidant properties of obtained protein isolates and resulting alcalase hydrolysates were investigated. The results showed that sample pre-treated with amyloglucosidase (8 units/g) had the higher protein content (82%) while celluclast (5–60 endo-glucanase units (EGU)/g) pre-treated samples had protein content similar to that of control (54%). In the oxygen radical absorbance assay (ORAC) all samples of protein isolates had significantly higher peroxyl radical scavenging activity than the control. The sample pre-treated with alpha-amylase (2300 units/g) displayed the highest activity with an ORAC value of 165±16μM Trolox Equivalents (TE)/g. Proteins were hydrolyzed with alcalase and radical scavenging activities of hydrolysates assessed by ORAC and HO• radical assays. Sample pre-treated with viscozyme 1.5 Fungal Beta-glucanase Units (FBU)/g was the more active in both assays: ORAC value 521±53μM TE/g and HO• radical inhibition 26.3±1.5%. A tandem mass spectrometric analysis of multiple charged ions within the hydrolysates allowed the identification of four new peptides.

15N-D-labeled ionic probes for mass spectrometry

An effective 15N- and deuterium (D)-labeled 2,6-bis(oxazolin-2-yl)pyridine (pybox)–La complex based probe ionization method that produces a distinct isotopic shift was developed. The distinct isotopic shift was detected by using the newly synthesized 15N-D-labeled pybox complexes. Moreover, O-[3-(tetramethylpybox)-propyl]-hydroxylamine (oxime–TMpybox) was prepared for attachment to the carbonyl group of the target molecule. Distinct isotopic shifts and multiple charged ions were detected for various compounds having amino, thiol, carboxyl, and carbonyl groups and fullerenes, using the TMpybox ionic probe series in cold-spray ionization mass spectrometry.

The ion–aerosol interactions from the ion mobility and aerosol particle size distribution measurements on January 17 and February 18, 2005 at Maitri, Antarctica – A case study

A case study for the ion–aerosol interactions is presented from the simultaneous measurements of mobility spectra of atmospheric ions in the mobility range of 2.29 to 2.98 × 10 − 4 cm2 V − 1 s $^{-1}$ (diameter range 0.41–109 nm) and of size distribution of atmospheric aerosol particles in the size ranges of 4.4–700 nm and 500–20,000 nm diameters made at Maitri (70°45′52′ ′S, 11°44′2.7′ ′E; 130 m above mean sea level), Antarctica, on two days January 17 and February 18, 2005, with contrasting meteorological conditions. In contrast to January 17, on February 18, winds were stronger from the morning to noon and lower from the noon to evening, atmospheric pressure was lower, cloudiness was more, the land surface remained snow-covered after a blizzard on February 16 and 17 and the airmass over Maitri, descended from an altitude of ~3 km after an excursion over ocean. On these days mobility spectra showed two modes, corresponding to intermediate ions and light large ions and an indication of additional one/two maxima for small/cluster ions and heavy large ions. The small ions generated by cosmic rays, and the nucleation mode particles generated probably by photochemical reactions grew in size by condensation of volatile trace gases on them and produced the cluster and intermediate ion modes and the Aitken particle mode in ion/particle spectra. Particles in the size range of 9–26 nm have been estimated to grow at the rate of 1.9 nm h − 1 on February 18, 2005. Both, ions and aerosol particles show bimodal size distributions in the 16–107 nm size range, and comparison of the two size distributions suggests the formation of multiple charged ions. Attachment of small ions to particles in this bimodal distribution of Aitken particles together with the formation of multiple charged ions are proposed to result in the light and heavy large ion modes. Growth of the nucleation mode particles on February 18, 2005 is associated with the passage of the airmass over ocean. In contrast, though the ion size distributions were not much different, the aerosol size distributions did not show a dominant peak for the formation and growth of nucleation mode particles on January 17. More measurements are needed before the conclusion of this case study is generalized.