Pulsed Ion Research Articles

Molecular-Dynamics Simulation of the Interaction Processes of Pulsed Ion Beams with Metals

The molecular-dynamics method is used to model the interaction processes of pulsed ion beams with metal targets. The main parameters of a pulsed ion beam interacting with a target are the ion energy, pulse duration, and charge density per unit area of the target. Using averaged values of these parameters of ion beams published for various types of accelerators, a numerical study of the dependence of the dynamics of thermal and structural processes in irradiated targets upon a change in the size and heterogeneity of the structure is performed. Simulation of the irradiation processes and estimates of the distribution of beam ions in the volume are carried out in the range of beam ion energies of 1–2 keV using the concept of a shock wave. The results are important for developing the model of a pulsed ion beam and classifying the types of structural changes in the irradiated material depending on the model parameters.

Ion Mobility Spectrometry with High Ion Utilization Efficiency Using Traveling Wave-Based Structures for Lossless Ion Manipulations.

Ion packets introduced from gates, ion funnel traps, and other conventional ion injection mechanisms produce ion pulse widths typically around a few microseconds or less for ion mobility spectrometry (IMS)-based separations on the order of 100 milliseconds. When such ion injection techniques are coupled with ultralong path length traveling wave (TW)-based IMS separations (i.e., on the order of seconds) using structures for lossless ion manipulations (SLIMs), typically very low ion utilization efficiency is achieved for continuous ion sources [e.g., electrospray ionization (ESI)]. Even with the ability to trap and accumulate much larger populations of ions than being conventionally feasible over longer time periods in SLIM devices, the subsequent long separations lead to overall low ion utilization. Here, we report the use of a highly flexible SLIM arrangement, enabling concurrent ion accumulation and separation and achieving near-complete ion utilization with ESI. We characterize the ion accumulation process in SLIM, demonstrate >98% ion utilization, and show both increased signal intensities and measurement throughput. This approach is envisioned to have broad utility to applications, for example, involving the fast detection of trace chemical species.

Gas cell studies of thorium using filament dispensers at IGISOL

Filament-based dispensers of thorium have been investigated at the IGISOL facility, Jyväskylä, for potential use as a thorium ion source for future collinear laser spectroscopy experiments. Several different filaments were manufactured in the Institute of Atomic and Subatomic Physics of TU Wien, with 232Th and 229Th prepared on tantalum substrates either by drying thorium nitrate solution or via molecular plating, while adding a layer of zirconium for oxide reduction. The filaments were characterized in a helium-filled gas cell by performing selective and efficient in-gas-cell resonance laser ionization and by analyzing the resulting ion beams by mass spectrometry. Additionally, the in-gas-cell laser ionization process of thorium was further characterized by wavelength scans, saturation measurements and by recording the temporal behavior of extracted ion pulses. Although an ion source was successfully created with mass-separated intensities over 106 ions/s, the required high filament temperature resulted in significant contributions from interfering impurities and deterioration of the filament structure.

Generation of ultrashort ion pulses in the keV range: Numerical simulations

In order to gain a direct experimental access to the ultrafast dynamics induced by an impact of an energetic particle onto a solid surface, we set out to utilize a pump–probe technique using an ultrashort ion pulse as a stimulus (“pump”) in combination with a synchronized and time delayed analysis (“probe”). As a necessary prerequisite, we have recently developed a concept to generate ultrashort ion pulses with (sub-)picosecond temporal duration in the keV ion energy range which is interesting in many applications of ion–solid interactions. Here, we present further numerical simulations, where we focus on identifying pathways to decrease the space charge broadening of pulses containing more than one ion. As a result, we find that the influence of space charge can be significantly decreased using a defocused and properly shaped laser beam, thereby allowing to generate picosecond pulses containing up to ∼100 ions.

Direct measurement of fast ortho-para conversion of molecularly chemisorbed H2 on Pd(210)

Ortho-para conversion of molecularly chemisorbed ${\mathrm{H}}_{2}$ on a Pd(210) surface at a surface temperature of 50 K is reported. A combination of a pulsed molecular beam, photostimulated desorption, and resonance-enhanced multiphoton ionization techniques was used for probing the change in the rotational states of molecularly chemisorbed ${\mathrm{H}}_{2}$ on the surface. Our result shows that fast ortho-para conversion of chemisorbed ${\mathrm{H}}_{2}$ occurs. The conversion time was experimentally determined to be about 2 s, which is in good agreement with a previous theoretical calculation. This agreement supports that the ortho-para conversion mechanism of the molecularly chemisorbed ${\mathrm{H}}_{2}$ on Pd(210) is a two-step process based on the hyperfine-Coulomb excitation.

CORROSION BEHAVIOR OF Ti–Al–N COATING MODIFIED ON CARBON STEEL PREPARED AT DIFFERENT TEMPERATURES

In this paper, pulsed arc ion plating was applied for preparing Ti–Al–N coatings. The effects of different process parameters on the structure and corrosion resistance properties of Ti–Al–N coating were studied by changing the temperature. The microstructures, morphology features and the corrosion resistance of the different temperatures of Ti–Al–N coating were investigated to simulate the corrosion conditions of seawater. All the samples (prepared at [Formula: see text]C, [Formula: see text]C, [Formula: see text]C and [Formula: see text] were measured in 3.5[Formula: see text]wt.% NaCl solution at [Formula: see text]C and characterized by potentiodynamic polarization curves, scanning electron microscopy (SEM) combined with analyzed by X-ray diffraction (XRD). The corrosion resistance of carbon steel was improved by the coating modification. The results showed that the sample prepared at [Formula: see text]C possesses excellent corrosion resistance where corrosion current density can only reach to 11.176[Formula: see text][Formula: see text]A/cm2, Meanwhile, SEM images also revealed that the microstructure of the sample is much smoother and nearly no defects can be observed.

Characterization of a supersonic gas jet via laser-induced photoelectron ionization

We describe the characterization of a pulsed supersonic rare gas beam which is intended to serve as an ultracold neutral atom target for the production of an ultrashort ion pulse via femtosecond photoionization. The velocity distribution of atoms entrained in the beam is measured and characterized by temperatures TII and T⊥ in directions along and perpendicular to the beam propagation, respectively. It is shown that T⊥ values in the mK regime are achieved at distances of the order of 1000 mm from the nozzle. Moreover, the center beam density at this position is measured to be of the order of 1011 atoms/cm3. Both findings are essential for the intended application and confirm the targeted beam specifications. Comparison with theoretical estimates reveals the well-known skimmer interference effect, which is found to reduce the beam density by more than one order of magnitude.

Quantification of oxygenates, sulphides, thiols and permanent gases in propylene. A multiple linear regression model to predict the loss of efficiency in polypropylene production on an industrial scale

This research developed a new methodology using a gas chromatograph, a pulsed discharge helium ionization detector (PDHID), and two mass spectrometric (MSD) detectors. The detectors worked simultaneously, using 8 columns and 7 valves. This new proposal for simultaneous analysis, with a single injection and analysis time of 36 min, allowed the quantification of 10 oxygenated compounds (alcohols, ketones and carboxylic acids), 3 permanent gases, 3 sulphides and 4 thiols, which are aggressive inhibitors of the Ziegler-Natta catalytic systems. The RSD (n=6) for repeatability of the peak area of the 20 compounds analyzed, and the retention time were less than 0.59 and 0.23% respectively. The RSD (n=6) for intermediate precision for the peak area was less than 0.85% and, for the retention time, less than 0.35%. 95% of the inhibitors analyzed showed relative errors inter and intra-day less than 3%. The inhibitors detected and quantified were: formic acid (2 to 45.32 ppm), acetic acid (1 to 25.32 ppm), acetone (5 to 72.67 ppm), methanol (1 to 39.93 ppm), isopropyl alcohol (2 to 74.88 ppm), ethanol (0.1 to 57.51 ppm), 1-propanol (0.1 to 92.36 ppm), 1-butanol (5 to 92.36 ppm), 2-butanol (5 to 95.15 ppm), tert-butanol (5 to 90.22 ppm), CO2 (0.5 to 5.0 ppm), CO (0.002 to 5.049 ppm), O2 (0.5 to 6.5 ppm), CH3(CH2)3SH (0.025 to 2.238 ppm), CH3CH2SH (0.025 to 1.595 ppm), COS (0.025 to 1.477 ppm), CH3SH (0.025 to 1.223 ppm), CH3(CH2)2SH (0.025 to 1.880 ppm), CS2 (0.025 to 1.929 ppm), H2S (0.025 to 0.847 ppm) and tert-butylmercaptan (0.025 to 2.283 ppm). These compounds generated reductions of between 5 and 20% in polypropylene production, representing losses of several million dollars. Therefore, a multilinear regression model was developed to predict this percentage of production loss in a fluidized bed reactor, based on the quantified inhibitors. The model has a correlation coefficient of 0.91 and a standard deviation of 1.12, allowing comparisons between actual and predicted experimental values. P values are less than 0.05, indicating that each inhibitor has a statistically significant effect on the model.

High-intensity pulsed ion beam treatment of amorphous iron-based metal alloy

The results of intense pulsed ion beam (IPIB) treatment of the soft magnetic amorphous alloy of a FINEMET-type are presented. Foil produced from the alloy was irradiated with short (about 100 ns) pulses of carbon ions and protons with energy of up to 300 keV and an energy density of up to 7 J/cm2. X-ray diffraction, Mössbauer spectroscopy and magnetic measurements were used to investigate structural and magnetic properties of irradiated foils. It is shown that the foil remains intact after the treatment, and the crystal structure still amorphous. Spontaneous magnetization vector is found to lie almost along perpendicular to the foil plane after irradiation, whereas for the initial amorphous foil it belongs to the plane. The magnetic properties of the foil undergo changes: the coercive force decreases, the saturation induction increases slightly, and the magnetization curve has shallower slope.

Triggering of Pressurized Gas Switches With a Class I Laser

The use of lasers to initiate the closure of high-power gas switches was initially explored soon after the development of suitable high-power pulsed lasers in the 1960s. The low jitter, excellent triggering range, and galvanic isolation provided by laser triggering have been extensively exploited in the triggering of megavolt switches in large pulsed power machines. The fact that the lasers and optical systems used in these machines are very large, complex, and expensive and have led to the perception that these are unavoidable characteristics of laser triggered gas switches, leading to a reluctance among the directed energy and compact pulsed power community to consider their use in compact pulsed power systems. The Advanced Pulsed Energy, Ionization, and Discharge Center (APERIODIC) Research Group at The University of New Mexico (UNM), Albuquerque, NM, USA, has been investigating novel triggering technologies for compact pulsed power. One of the technologies under investigation is a system we have named the microintegrated laser switch (MILS) [1]. This system holds the potential to overcome the limitations of traditional laser triggering of gas switches in compact applications. As part of the preliminary work on developing the MILS concept, UNM has collaborated with MegaWatt Lasers, Hilton Head Island, SC, USA, to conduct laser triggering experiments using a commercial off-the-shelf (COTS) erbium-doped glass passively Q-switched microlaser. This 28 mm × 9 mm laser produces 4-ns pulses at 1535 nm with an average energy per pulse of 244 μJ. One of the principal advantages of this laser is that, due to the wavelength and energy, it is a class 1 laser and can be operated without the stringent controls necessary for the lasers typically used for laser triggering.

Absorption of 1535-nm Laser Pulses in Insulating Oils

The Applied Pulsed Energy, Ionization, and Discharge Center (APERIODIC) research group at The University of New Mexico, Albuquerque, NM, USA, has been investigating the use of low-energy diode-pumped solid-state (DPSS) passively q-switched lasers operating at a wavelength of 1535 nm to trigger gas switches. This wavelength was chosen due to the improved eye safety and ready supply of commercial microlasers at this wavelength. Laser triggering of switches in a pulsed power system often presents challenges in beam transport from the laser to the switch optics. In many cases, it is most convenient if the beam transport can be accomplished directly through the insulating medium of the device. It is also possible that this laser wavelength could be used to trigger an oil-insulated spark gap switch. Thus, the absorption of the laser wavelength in insulating oils is of interest. In this work, the absorption coefficient of the 1535-nm laser pulses has been measured for various common insulating oils. The results indicate that beam transport through oil at this wavelength will likely be impractical due to relatively high absorption. However, the absorption is low enough that the use of this wavelength to trigger an oil-insulated gap could be possible.

Properties of heavy ion beams produced by a PW sub-picosecond laser

The paper reports the results of numerical studies on the generation of heavy ions from a sub-micrometre gold target irradiated by a high-energy (60 J) high-intensity (∼ 2 × 1020 W/cm2) sub-ps laser pulse. The properties of the heavy ion beam produced from a 0.5-μm gold target with and without hydrogen contaminants are investigated using a multi-dimensional (2D3 V) particle-in-cell code. It was found that in the case of the pure (without the contaminants) target, the ion beam contains over 20 ion species with a charge state > 30 and a total number of high-energy (> 20 MeV) ions reaching values well above 1012. The ion energy spectrum is broad, with maximum energies > 1 GeV and mean energies > 100 MeV . At a distance ∼ 1 mm from the target, the intensity of the ion beam is ∼ 1015 W/cm2, the ion fluence reaches ∼ 1016 ions/cm2, and the ion pulse duration is ∼ 100 ps. The contaminants significantly reduce the ion beam parameters and both the mean ion energy and the intensity and fluence of the ion beam generated from the contaminated gold target are almost an order of magnitude lower than those produced from the pure target. Heavy ion beams with the parameters obtained in the case of the pure gold target are barely achievable in conventional RF-driven accelerators, so they can open the door to new areas of research, in particular in high energy-density physics.

Radiation Power Control of the Industrial CO<sub>2</sub> Laser Excited by а Nonself-Sustained Glow Discharge by Changing the Frequency of Ionization Pulses

The article describes radiation power control of industrial CO2 lasers of Lantan series excited by а nonself-sustained glow discharge in the automatic mode. These lasers are closed-cycle fast gas-transport lasers excited by a nonself-sustained glow discharge with ionization by periodic-pulsed capacitively coupled auxiliary discharge. In this case, ionization and conductivity are provided by periodic-pulsed capacitively coupled discharge. The energy contribution to molecular oscillations is provided by the passage of the main discharge current through the plasma with electron density given by ionization. This permits easy laser power control, provides excellent optical homogeneity and stability of an active volume together with high laser efficiency. A system of a nonself-sustained glow discharge with ionization by periodic-pulsed capacitively coupled auxiliary discharge, the stages of creation and brief characteristics of the Lantan series lasers is presented. The method of controlling the power of laser radiation by changing the frequency of the ionization pulses is determined. This control method allows operating of the laser in continuous and in pulse-periodic modes with adjustable pulse ratio and pulse duration, and also provides switching from one mode to another. In the continuous mode, the radiation power is controlled by changing the frequency of ionization pulses, which are high voltage pulses with duration of 100 ns, given with the frequency of 1-5 kHz. Pulse-periodic radiation control is performed by modulating ionization pulses that consists of pulses being delivered in batches. The frequency of the pulses in a batch determines the radiation power in a pulse. The frequency of the batches following is the frequency of the pulse mode, and the length of the batch determines the pulses duration. Based on the experimental data, the dependence of the radiation power on the ionization pulses frequency was determined. An experimental system is presented and the measuring accuracy of the laser radiation power and the frequency of ionization pulses is determined. Data acquiring and processing of experimental results were performed using the NI 6008 USB data acquisition device in the LabVIEW programs of National Instruments. To study the dependence of the laser power on Мехатроника, автоматизация, управление, Том 21, № 4, 2020 231 the frequency of the ionization pulses, a regression analysis method was applied. Studies have shown that the dependence of the laser power on the ionization pulses frequency is linear in a wide range of parameters. The equation of the direct regression is calculated. The confidence estimates of the coefficients of the direct regression and the confidence estimates of the deviation of the theoretical direct regression from the empirical one are calculated with a confidence level of 95%.

Design of target irradiation and diagnostic chamber to study ps-laser generated plasma as a source of singly charged ions for external injection into an electron beam ion source.

High repetition-rate (∼10 kHz) ps-lasers are becoming available on the market with reasonable cost and may offer several advantages compared to ns-lasers by generating nearly continuous beams of singly charged ions appropriate for the "slow" injection mode into the Electron Beam Ion Source (EBIS). To evaluate these advantages, we will perform studies of a ps-laser generated plasma using a laser with a pulse duration of 8 ps and energy up to 5 mJ per pulse. A vacuum chamber equipped with a 3D target positioner, a focusing lens, and a Faraday Cup has been designed and built for this study. Lens-to-target distance variations have been measured using a laser tracker over the whole range of horizontal and vertical translation for all five targets we will use. The variations were found to be within ±150 µm. This degree of "target flatness" should be acceptable for our experimental conditions. Ion currents and ion pulse durations of various elements (from Al to Ta) will be measured for different target irradiation conditions (focal spot size and laser pulse energy). The results obtained will allow us to specify all parameters and geometry of a laser ion source based on a ps-laser to provide external ion injection into the relativistic heavy ion collider EBIS.

Pulsed Nano-Electrospray Ionization with a High Voltage (4000 V) Pulse Applied to Solutions in the Range of 200 ns to 1 ms.

To initiate electrospray, it is necessary to accumulate excess charges on the liquid surface until the outward electrostatic pressure (PE) overwhelms the inward pressure Pγ originating from the surface tension of the liquid droplet. In this report, electrospray mass spectrometry for solutions of gramicidin S (G), ubiquitin (U), and cytochrome c (C) in H2O/CH3OH (1/1) was performed as a function of the high voltage (4000 V) pulse width in the range of 200 ns to 1 ms using a 4 μm i.d. glass capillary. Multiply protonated ions for all three samples started to be detected with the 300 μs pulse width. Denaturation of C and U proceeded with an increase of the pulse width. When the bias voltage of ∼880 V that was lower than the threshold voltage for the generation of continuous electrospray (∼1000 V) was applied to the solution, multiply protonated G, U, and C were detected with the 200 ns pulse width. After the depletion of excess charges in 200 ns, it took 10-100 μs to regenerate electrospray.

Coupling IR-MALDESI with Drift Tube Ion Mobility-Mass Spectrometry for High-Throughput Screening and Imaging Applications.

Because of its high degree of selectivity and chemical resolution, mass spectrometry (MS) is rapidly becoming the analytical method of choice for high-throughput evaluations and clinical diagnostics. While advances in MS resolving power have increased by an order of magnitude over the past decade, advances in sample introduction are still needed for high-throughput screening applications where the time frame of chromatographic separation would limit the duty cycle. Infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) is an ambient ionization source that has been shown to be applicable for direct analyses and mass spectrometry imaging (MSI) of complex biological samples in a high-throughput manner. To increase a range of detectable features in IR-MALDESI experiments, we integrated the home-built ion source with a commercially available drift tube ion mobility spectrometer-mass spectrometer (IMS-MS) and analyzed small polar molecules, lipids, carbohydrates, and intact proteins. We also describe in detail how the pulsed ionization source was synchronized with IMS-MS.

Времяпролетная оптическая диагностика мощных импульсных ионных пучков

Ablation of a thin surface contamination layer is used to control fluencies of intense pulsed ion beams. The layer is self-restored after each ion pulse. An optical time-of-flight spectrometer measures velocities of the lightest components of the ablation plasma, hydrogen and carbon, to determine the ion fluence.

Effects of slant angle of sharp plasma-vacuum boundary on electron injection in laser wakefield acceleration

Plasma wakefield acceleration driven by ultra short ultra intense laser pulse interacting with gas target has been studied for almost four decades. Monoenergetic electron beams with central energy of multi-giga electron-volt have been achieved in a centimeter-scale acceleration distance. Currently, the highest energy of electrons accelerated by laser wakefield is 8 GeV. In order to further improve the quality of such electrons, many kinds of electron injection schemes have been proposed such as density gradient injection, colliding pulse injection and ionization injection. Electrons under the suitable conditions can be trapped by the strong plasma wakefield. Those trapped electrons are then accelerated in the wakefield. In a nonlinear regime, the wakefield shows a “bubble” structure. Electrons with transverse momentum can oscillate in the wakefield and produce considerably betatron radiation in the ultraviolet and X-ray region. In this paper, we study the electron injection around the sharp plasma-vacuum boundary. The effects of the slant angle of the boundary on the final electron quality are investigated in detail. Our results show that with optimal slant density transition around the vacuum plasma boundary, both the beam quality and the injection charge in the second “bubble” can be improved. Two-dimensional particle-in-cell simulations show that the injection charge in the second wake bucket can be increased three times when an optimal slant angle is used compared with a vertical boundary. The driving pulse’s polarization also affects the injection charge. When the polarization is in the injection plane the injection charge in the first bucket can be triply increased compared with the case when the polarization is out of the plane. The reasons for the enhanced injection charge and transverse oscillation are found by tracing the initial injection positions and trajectories of the electrons. These studies would benefit the electron acceleration and its applications, such as compact betatron radiation source.

АППАРАТУРА ДЛЯ ИССЛЕДОВАНИЯ ПРОЦЕССОВ ДЕЛЕНИЯ

This article is devoted to the study of the principles of operation of a pulsed ionization chamber, in which particles emitted from a target create a sequence of well-isolated current pulses (the distance between pulses is several times greater than their width). Firstly, using the Ramo-Shockley theorem, the mechanisms of forming signals on the electrodes of an ionization chamber with Frisch nets are considered, then it is shown how information on energy and spatial orientation of particles can be extracted from such signals using modern electronic pulse digitizers.

The Influence of Injected Fluids on Microscopic Pore Structures in the Intersalt Dolomitic Shale Oil Reservoirs

Given their low porosity and permeability, intersalt dolomitic shale oil reservoirs need to be developed via large-scale hydraulic fracturing to achieve economic effects. However, various lithologies and salt materials make these reservoirs vulnerable to salt mineral dissolution and recrystallization and salt plugging during development. This study investigated the variation rules of pore structures, porosity, and permeability of intersalt dolomitic shale oil reservoirs under the influence of hydraulic fracturing fluid. Correspondingly, a series of experiments (i.e., high-temperature and high-pressure soaking experiments, focused ion beam scanning helium ion microscope analyses, and porosity and pulse permeability tests) is performed on the Qian 34-10 rhythmic intersalt dolomitic shales. Results show that distilled water dissolves the salt crystals inside the matrix pores to improve the reservoir permeability. However, the distilled water-rock interaction will cause the massive migration of salt minerals. By contrast, the supercritical CO2 can disperse salt particles, dredge the channels, and enlarge pores by expansion, but it has an overall weak capability of changing the pore structure and matrix permeability. To simulate the supercritical CO2 composite fracturing, the mixed solution of supercritical CO2 and distilled water favors the salt dissolution effect in the water-based fracturing fluid and recovery enhancement by CO2. This solution can remarkably improve the reservoir porosity and permeability and avoid massive salt mineral migration and salt crystallization damage. This study is theoretically and practically important to the effective and enhanced development of intersalt dolomitic shale oil reservoirs.