Ion Loss Research Articles

Alpha particle loss measurements and analysis in JET DT plasmas

Burning reactor plasmas will be self-heated by fusion born alpha particles from deuterium-tritium reactions. Consequently, a thorough understanding of the confinement and transport of DT-born alpha particles is necessary to maintain the plasma self-heating. Measurements of fast ion losses provide a direct means to monitor alpha particle confinement. JET’s 2021–2022 second experimental DT-campaign offers burning plasma scenarios with advanced fast ion loss diagnostics for the first time in nearly 25 years. Coherent and non-coherent alpha losses were observed due to a variety of low frequency MHD activity. This manuscript will present the loss mechanisms, spatial and pitch dependencies, scalings with plasma parameters, correlations with wall impurities, and magnitude of DT-alpha born losses.

Inhibiting efflorescence of alkali-activated slag mortar by improving its hydrophobicity with methyl-terminated polydimethylsiloxane (PDMS): Evidences showing the remained PDMS

This paper proposes to prepare hydrophobic alkali-activated slag (AAS) mortars with methyl-terminated polydimethylsiloxane (PDMS), a hydrophobic polymer with low surface energy, to minimize its water sorptivity and efflorescence. To depict the efflorescence process of PDMS-modified AAS mortars, visual inspections of efflorescence features, the leaching behavior of sodium ions, water absorption characteristics of mortars and contact angle tests were conducted. Additionally, the hydration process, microscopic morphology, and chemical structure of PDMS-modified AAS mortars and pastes were examined by compressive strength, isothermal calorimetry, TEM, SEM, FT-IR, 29Si NMR, enabling the explanation of PDMS working mechanisms. The results demonstrated that the addition of PDMS successfully mitigated esthetic issues and the spalling of mortars caused by efflorescence. Furthermore, PDMS reduced the risk of long-term durability issues of AAS mortars by restricting the loss of sodium ions after efflorescence. At the same time, the introduction of PDMS with dosage below 5 % did not significant retarder the hydration reaction process or the development of strength of AAS. However, it did alter the micromorphology and chemical structure of the hydration product. PDMS linked to the hydration products through covalent bonds and acted as a bridging role to alter the micromorphology of the hydration products. The resulting multi-structured material exhibited micropapillary and nano-coating layers with hydrophobic methyl functional groups, imparting hydrophobicity to the PDMS-AAS hydration product.

Validation of a synthetic fast ion loss detector model for Wendelstein 7-X

We present the first validated synthetic diagnostic for fast ion loss detectors (FILDs) in the Wendelstein 7-X (W7-X) stellarator. This model has been developed on, and validated against experimental data from, a FILD provided by the National Institute for Fusion Science (NIFS-FILD), with potential future applicability to the existing Faraday Cup FILD (FC-FILD) on W7-X as well as the scintillating FILD (S-FILD) currently under development. A workflow combining Monte Carlo codes BEAMS3D and ASCOT5 is used to track fast ions produced by neutral beam injection from the moment of ionization until they are thermalized or lost from the last closed flux surface, and from there to a virtual plane which serves as a projection of the entrance aperture to the FILD. Simulations in ASCOT5 are analyzed via a geometric method to determine the probability of transmission through the FILD aperture and onto the detector as a function of normalized momentum, pitch angle, gyrophase, and position at the virtual plane. This probability is then applied to the simulated ions arriving from the plasma, producing a simulated signal from a computationally tractable number of simulated fast ions. Simulated signals are presented for two W7-X experiments with neutral beam injection and quantitatively compared with experimental measurements from the NIFS-FILD diagnostic. An estimate of the frequency of charge-exchange with neutral particles in the edge is performed, and it is found that this process may have a significant impact on the measured signals.

Simulation of charge-exchange induced NBI losses on EAST

The neutral beam injection is widely adopted in tokamaks as a key heating tool, playing a crucial role in generating burning plasmas. However, the loss of beam ions can damage the first wall and reduce the heating efficiency, resulting in failure to maintain steady-state conditions. In this work, the effect of neutral particles in the edge on fast ions generated by NBI in the Experimental Advanced Superconducting Tokamak (EAST) device is studied using the particle tracer code (PTC). The poloidal distribution of neutral particles is calculated by edge plasma simulation code SOLPS-ITER. In this simulation, four beam lines in EAST are considered: co-current tangential (co-tang), co-current perpendicular (co-perp), counter-current tangential (ctr-tang) and counter-current perpendicular (ctr-perp). It is shown that, in the absence of neutral particles, the loss fraction of ctr-injection is considerably higher than that of the co-injection. When considering the neutral particles, it is found that the ctr-perp injection demonstrates a significant variation in particles loss fraction (ranging from 18.56% to 25.42%) compared to the other three injection configurations. In terms of the loss fraction induced by neutral particles, ctr-injection exceeds co-injection, and perpendicular configuration exceeds tangential configuration. Furthermore, the difference of charge exchange ratios of three different energy (full energy, half energy, one third energy) of the four injections can be attributed to variations in the poloidal trajectories associated with each of these injections. Moreover, approximately half of fast ions which undergo neutralization directly lose to the first wall while the rest re-enter the bulk plasma and re-ionize. Except for the ctr-tang injection, the reionization ions from the other three injections exhibit effective confinement.

Unraveling the delithiation mechanism of air-stabilized fluorinated lithium iron oxide pre-lithiation material

Integrating pre-lithiation materials into the cathode to compensate for the irreversible loss of active lithium ions due to the anodes is one of the essential technologies for achieving high-energy lithium-ion batteries. Li5FeO4 (LFO) has emerged as an appealing candidate for its high initial charge specific capacity, cost-effective, and suitability for the solvents/binders. Unfortunately, suffering from notorious degradation while in storage hinders its large-scale application. Furthermore, the delithiation mechanism and the impacts of oxygen species during charging remain elusive. Herein, a fluorinated LFO, featuring the F-doped carbon layer on the surface and gradient fluorination in the bulk, is synthesized to overcome the above obstacles. Surface modification enhances the air stability in storage and prevents oxygen species from attacking the electrolyte upon charging. The introduction of fluorine is proposed to lower the migration barrier of Fe from the tetrahedral interstitial site to the octahedral one and narrow the band gap, thus maintaining a stable phase transition at high charge density. As a result, the fluorinated LFO possesses excellent air stability (541.9 mAh g−1 after humid air exposure of 24H) and exhibits attractive initial charge specific capacity (703.4/580.5 mAh g−1 at 0.05/1.0C rate) as well as slight electrolyte decomposition during the charging process. This work opens up an alternative avenue to developing industry-applicable pre-lithiation materials for high-energy batteries.

Synchrotron-based x-ray diffraction analysis of energetic ion-induced strain in GaAs and 4H-SiC

Strain engineering using ion beams is a current topic of research interest in semiconductor materials. Synchrotron-based high-resolution x-ray diffraction has been utilized for strain-depth analysis in GaAs irradiated with 300 keV Ar and 4H-SiC and GaAs irradiated with 100 MeV Ag ions. The direct displacement-related defect formation, anticipated from the elastic energy loss of Ar ions, can well explain the irradiation-induced strain depth profiles. The maximum strain in GaAs is evaluated to be 0.88% after Ar irradiation. The unique energy loss depth profile of 100 MeV Ag (swift heavy ions; SHIs) and resistance of pristine 4H-SiC and GaAs to form amorphous/highly disordered ion tracks by ionization energy loss of monatomic ions allow us to examine strain buildup due to the concentrated displacement damage by the elastic energy loss near the end of ion range (∼12 μm). Interestingly, for the case of SHIs, the strain-depth evolution requires consideration of recovery by ionization energy loss component in addition to the elastic displacement damage. For GaAs, strain builds up throughout the ion range, and the maximum strain increases and then saturates at 0.37% above an ion fluence of 3×1013 Ag/cm2. For 4H-SiC, the maximum strain reaches 4.6% and then starts to recover for fluences above 1×1013 Ag/cm2. Finally, the contribution of irradiation defects and the purely mechanical contribution to the total strain have been considered to understand the response of different compounds to ion irradiation.

Improvement in ion confinement time with multigrid configuration in an inertial electrostatic confinement fusion device.

Improvement in the functionality of an inertial electrostatic confinement fusion (IECF) device has been investigated through kinetic simulation. Previously, we achieved a neutron generation rate of 10^{6} neutrons per second, but higher rates and better plasma confinement are necessary for broader applications. We compared a traditional single-grid IECF device with a triple-grid variant to evaluate the benefits of using multiple grids for ion confinement. Our computational models, using the 2D-3V xoopic code, suggest that the triple-grid device, with its optimized potentials, could significantly enhance ion confinement. The models show that the triple-grid design directs ion beams more effectively to the center, in contrast with the more scattered ion distribution in the single-grid design. This results in longer ion lifetimes in the triple-grid system due to its modified electrostatic fields. In the standard single-grid IECF device, the primary reasons for ion loss are chaotic ion trajectories and interactions with residual gases. By operating the triple-grid device under very low background gas pressure and with a focused field structure, we expect to achieve improved ion confinement.

Numerical analysis of fast ions transport induced by magnetic islands in HL-2A

The transport of beam ions in the presence of single/multiple tearing modes (TMs) under HL-2A geometry has been investigated by test particle method. Simulation results show that there exists a threshold behavior in the number of lost beam ions in the plasma under perturbation of a (2,1) TM with amplitude α0 : when the amplitude α0 is over a critical value, the number of lost beam ions increases linearly with α0 at a much faster pace. Further analysis finds that the lost beam ions have relatively higher percentage of high energy at α0 around the critical value. It also finds that the distribution of lost beam ions which is initially concentrated on the high field side expands gradually toward the low field side as the perturbation amplitude α0 increases. From the phase space analysis, it shows that the enhanced outward transport of fast ions in the presence of magnetic islands results from orbit stochasticity, which is due to the overlap of the drift islands in the interaction of fast ions with TMs. When two TMs are simultaneously present, the stochastic threshold of fast ion orbit is found to be lower than that in their individual TM case. The phase space analysis shows that in the presence of two modes with the same toroidal mode number, the modes increase the loss of fast ions when they are out of phase; however, such the effect of strengthening transport of fast ions turns to weaken when they are in phase. In contrast, when two modes each with a different toroidal mode number, their phase difference phase hardly has any effect on the transport of fast ions.

THz vs NIR laser-assisted atom probe tomography of LaB6 samples

Terahertz (THz) radiation with low-energy photons (meV) is used in a wide range of applications, such as microscopy, sensing, and spectroscopy. However, recently, high amplitude THz pulses of MV/cm have been generated and used for electron emission and ion evaporation from field emitters, opening up the possibility of using high amplitude THz pulses for material imaging by THz-assisted atom probe tomography (APT). In this work, we compare the APT analyses of lanthanum hexaboride (LaB6) samples using a femtosecond near-infrared laser with those obtained using high-amplitude single-cycle THz pulses. The atomic-scale characterization of stoichiometric LaB6 is challenging in laser-assisted APT due to the detection losses of boron ions. Here, we show that the THz radiation reduces the emission of molecular ions and multiple detection events, and it increases the charge state of the emitted ions. All these effects result in an improvement in boron detection. Furthermore, the emission dynamics of boron and lanthanum ions differ in their evaporation times when using THz radiation. This work emphasizes the ability of high-amplitude, single-cycle THz pulses to well control material analysis in APT, leading to better results on chemical composition. It also paves the way for the use of this radiation for material manipulation.

Mitigating self-discharge in supercapacitors through strategic mesoporous structural modification of NiCo layered double hydroxides

Nickel - Cobalt layered double hydroxide (NiCo LDH) based supercapacitors suffer from severe self-discharge due to their uneven charge distribution, which affects the application of supercapacitors (SCs) in real life. In this paper, three-dimensional self-supported mesoporous NiCo layered double hydroxide mesoporous on nickel foam (NF) (NiCo LDHMs/NF) was prepared by H2O2 etching. The self-discharge phenomenon of supercapacitors assembled using the reaction-derived NiCo LDHMs/NF as the positive electrode and activated carbon as the negative electrode is significantly suppressed. Comparing with the original NiCo LDH devices, the successful construction of mesoporous structures in NiCo LDH resulted in slower open-circuit voltage (OCV) decay (0.93 V vs. 0.59 V in the range of open-circuit voltage of 1.8 V for the same time of 7200 S), and lower leakage current (0.09 mA vs. 0.18 mA at 1.8 V). Due to the formation of mesoporous structure, the charged ions adsorbed on the electrode have more storage sites. Which reduces the movement or loss of charged ions to inhibit the charge redistribution, so it has a high specific capacitance and the self-discharge phenomenon has been greatly reduced.

Simulation of a scintillator-based fast ion loss detector for steady-state operation in Wendelstein 7-X (invited).

A quantitative theoretical framework has been created to model neutral beam injection and fast ion losses in the Wendelstein 7-X (W7-X) stellarator, including a novel method to develop synthetic diagnostics for fast ion loss detectors (FILDs) of many types, such as scintillating and Faraday Cup FILDs. This is the first time that this has been done in stellarator geometry with this level of fidelity, providing a way for fast ion losses to be predicted more precisely in future stellarator experiments and in W7-X. Simulations of the signal seen by a Faraday Cup FILD have been completed for multiple W7-X plasmas and show close agreement with the measured signals. This method is now applied to an actively water-cooled, scintillator-based FILD, which is currently in development to measure the fast ion loss distribution in W7-X in greater detail. The design makes use of a double slit to measure energy-and-pitch-angle-resolved losses of both co-going and counter-going fast ions. The diagnostic, which can be inserted to different radial positions, has been designed to withstand steady-state heat fluxes of up to 120 kW/m2 along with additional transient heat loads of 100 kW/m2 lasting for up to 20s at a time. Simulations of W7-X standard magnetic configuration show up to 8 × 1013 (s-1 cm-2) ion fluxes onto the sensor from each neutral beam source and no signal from the counter-going slit. These simulations will help inform experimental proposals for future W7-X campaigns after installation of this diagnostic.

OPTEMIST: A neutral beam for measuring quasi-omnigenity in Wendelstein 7-X

A new neutral beamline (OPTEMIST) uniquely capable of exploring the predicted improvement of fast ion confinement in Wendelstein 7-X (W7-X), which comes with increasing plasma beta, is proposed. As the plasma beta increases in the W7-X device, the high mirror magnetic configuration has drift orbits that begin to close, enhancing the confinement of the deeply trapped particles. The existing neutral beam system is found to produce particle populations that do not adequately probe the deeply trapped orbits. Fast tritons generated by thermal deuterium–deuterium fusion reactions are found to probe the necessary conditions for demonstrating this effect. However, it is found that diagnostically measuring this effect will be difficult. A scoping study of a neutral beamline that directly populates the trapped orbits is performed. It is found that a monoenergetic population of 120 kV injected protons provides the largest confinement enhancement in the fast ion population as the plasma beta is increased. The necessity to raise plasma density to increase plasma beta results in blinding of spectroscopic beam measurements by bremsstrahlung. An array of novel fast ion loss detectors that would adequately assess the confinement of these particles is proposed.

Manipulating polarization attenuation in NbS2–NiS2 nanoflowers through homogeneous heterophase interface engineering toward microwave absorption with shifted frequency bands

Homogeneous heterogeneous (heterophase) interfaces regulated with low energy barriers have a fast response to applied electric fields and could provide a unique interfacial polarization, which facilitate the transport of electrons across the substrate. Such regulation on the interfaces is effective in modulating electromagnetic wave absorbing materials. Herein, we construct NbS2–NiS2 heterostructures with NiS2 nanoparticles uniformly grown in NbS2 hollow nanospheres, and such particular structure enhances the interfacial polarization. The strong electron transfer at the interface promotes electron transport throughout the material, which results in less scattering, promotes conduct ion loss and dielectric polarization relaxation, improves dielectric loss, and results in a good impedance matching of the material. Consequently, the absorbing band may be successful tuned. By regulating the amount of NiS2, the heterogeneous interface is finely alternated so that the overall wave-absorbing performance is shifted to lower frequencies. With a NiS2 content of 15 ​wt% and an absorber thickness of 1.84 ​mm, the minimum reflection loss at 14.56 ​GHz is −53.1 ​dB, and the effective absorption bandwidth is 5.04 ​GHz; more importantly, the minimum reflection loss in different bands is −20 dB, and the microwave energy absorption rate reaches 99% when the thickness is about 1.5–4.5 ​mm. This work demonstrates the construction of homogeneous heterostructures is effective in improving the electromagnetic absorption properties, providing guideline for the synthesis of highly efficient electromagnetic absorbing materials.

Electromagnetic ion cyclotron emission from ion-scale magnetic holes

Ion-scale magnetic holes are nonlinear plasma structures commonly observed in the solar wind and Earth's magnetosphere. These holes are characterized by the magnetic field depletion filled by hot, transversely anisotropic ions and electrons and are likely formed during the nonlinear stage of ion mirror instability. Due to the plasma thermal anisotropy within magnetic holes, they serve as a host of electromagnetic ion cyclotron waves, whistler-mode waves, and electron cyclotron harmonic waves. This makes magnetic holes an important element of the Earth's inner magnetosphere, where electromagnetic waves generated within may strongly contribute to energetic ion and electron scattering. Such scattering, however, will modify the hot-ion distribution that is trapped within magnetic holes and responsible for the magnetic field stress balance. Therefore, hot ion scattering within magnetic holes likely determines the hole lifetime. In this study, we investigate how ion scattering by electromagnetic waves affects the stress balance and lifetime of magnetic holes. For illustration, we used typical characteristics of magnetic holes, ion populations, and ion cyclotron waves observed in the Earth's magnetosphere. We have demonstrated that ion distribution isotropization via scattering by waves does not change significantly magnetic hole magnitude, but ion losses due to scattering into the atmosphere may limit the hole life-times to 10–30 min in the Earth's inner magnetosphere.

Melting of W/Cu flat type component for main limiter and its impact on plasma operation in EAST experiments

A type of actively cooled W/Cu flat-type component with high heat exhaust capacity was installed as limiter during the EAST spring plasma campaign in 2022, aiming to support the long pulse operation. Unfortunately, severe melting phenomena with obvious droplets ejection of the flat-type W/Cu limiter was repeatedly monitored by CCD and IR cameras, which not only induced the failure of component but also seriously influenced plasma operation. The high temperature around midplane of W/Cu flat-type main limiter is identified to be closely connected with ICRF induced fast ions loss. Indeed, the surface temperature of W/Cu flat-type main limiter was too high to ignore. The damage of flat-type structure, however, usually started between the joint interface of W plates and CuCrZr heat sink material. Such damage would in turn lead to the gradual increase of surface temperature which eventually would cause melting of W plates. Once melting events occurred on the W/Cu flat-type main limiter, the vast majority of cases would result in plasma disruption. Moreover, the damage of main limiter would rapidly deteriorate. Hence, more attention should be paid to how to improve the fatigue lifetime of the joint interface. Such test results of flat-type W/Cu component for limiter are important references for the improvement and application of W/Cu flat-type component for high heat flux area in fusion devices.

Пигментная система нитчатых цианобактерий в условиях аккумуляции ионов свинца

The effect of Pb (CH3COO)2 solutions with Pb2+ concentrations equal to 0.02, 0.1, 0.2 and 0.4 mM to strain of cyanobacteria (CB) Leptolyngbya sp. SK was studied. The duration of exposure of the culture with solutions was 21 days. During the experiment, measured the loss of lead ions in the solution; the increase in the biomass of CB was assessed as an indicator of culture adaptation; determined the content of photosynthetic pigments as indicators of maintaining the viability of the culture. The content of lead ions decreased in all variants, the maximum decrease was 96.2% – in the medium with a Pb2+concentration of 0.4 mM. An increase in the biomass of CB was observed in the presence of Pb2+ of all concentrations, the maximum increase in a solution with a Pb2+ concentration of 0.1 mM was up to 7.5 times. There was a decrease in the content of chlorophyll a in the biomass of CB, in comparison with the control, by 67.0–94.2% with an increase in the concentration of Pb2+ in the solution. Under the influence of solutions with Pb2+ concentrations of 0.02, 0.1, and 0.4 mM, the content of carotenoids in the biomass of cyanobacteria decreased by 48%, 75% and 92%, respectively; the concentration of Pb2+0.2 mM caused an increase in the content of carotenoids by 1% with the control. The inhibitory effect of all investigated concentrations of Pb2+ was noted on the complex of phycobilin pigments. The accumulation of lead ions from solutions with Pb2+ concentrations up to 0.4 mM, an increase in CB biomass in the presence of 0.1 mM Pb2+ and an increase in the synthesis of carotenoids at 0.2 mM Pb2+ may indicate adaptation of the studied culture to lead acetate.

Self-consistent calculation of the optical emission spectrum of an argon capacitively coupled plasma based on the coupling of particle simulation with a collisional-radiative model

We report the development of a computational framework for the calculation of the optical emission spectrum of a low-pressure argon capacitively coupled plasma (CCP), which is based on the coupling of a particle-in-cell/Monte Carlo collision simulation code with a diffusion-reaction-radiation code for Ar I excited levels. In this framework, the particle simulation provides the rates of the direct and stepwise electron-impact excitation and electron-impact de-excitation for 30 excited levels, as well as the rates of electron-impact direct and stepwise ionization. These rates are used in the solutions of the diffusion equations of the excited species in the second code, along with the radiative rates for a high number of Ar-I transitions. The calculations also consider pooling ionization, quenching reactions, and radial diffusion losses. The electron energy distribution function and the population densities of the 30 excited atomic levels are computed self-consistently. The calculations then provide the emission intensities that reproduce reasonably well the experimentally measured optical emission spectrum of a symmetric CCP source operated at 13.56 MHz with 300 V peak-to-peak voltage, in the 2–100 Pa pressure range. The accuracy of the approach appears to be limited by the one-dimensional nature of the model, the treatment of the radiation trapping through the use of escape factors, and the effects of radiative cascades from higher excited levels not taken into account in the model.

Analysis of fusion alphas interaction with RF waves in D-T plasma at JET

This work studies the influence of radio frequency (RF) waves in the ion cyclotron resonance heating (ICRH) range of frequencies on fusion alphas during the recent JET D-T campaign. Fusion alphas from D-T reactions are created with energies of about 3.5 MeV and therefore have significant Doppler shifts enabling synergistic interactions between them and RF waves at a broad range of frequencies, including the ones foreseen for future fusion machines in ITER (Schneider et al 2021 Nucl. Fusion 61 126058) and SPARC (Creely et al 2020 J. Plasma Phys. 86 865860502). Resonant interactions between RF waves and alphas, also called synergistic effects, will modify the alpha distribution and ultimately will have an impact on alpha orbit losses and heating. Data from JET 3.43 T/2.3 MA pulses based on the hybrid scenario (Hobirk et al 2023 Nucl. Fusion; Hobirk et al 29th IAEA FEC23 Conf. (16–21 October 2023); Challis et al 48th EPS Conf. on Plasma Physics (27 June–1 July 2022) during the DTE2 campaign (Maggi et al 2023 Nucl. Fusion)) were used for the analysis in this study. The impact of synergistic effects on alpha orbit losses and alpha heating are assessed. The conclusions are based on the analysis of experimental data for fast alpha losses, i.e. measurements from neutral particle analyser (NPA), fast ion losses scintillator detector, Faraday cups (FCs), and TRANSP (Hawryluk et al 1980 Physics of Plasmas Close to Thermonuclear Conditions vol 1 (CEC) pp 19–46) simulations. Experimental data and TRANSP analysis indicates that there are indeed changes in the alpha distribution function (DF) due to interaction with RF waves. Data from the NPA show increased 4He flux in the range from a few hundred keV up to 800 keV for pulses with RF power, while TRANSP clearly shows modifications in the fast alpha DF for these energies. Data from the scintillator detector and the FCs were compared for pulses with and without ICRH power and versus cases with enhanced alpha losses due to MHD activity. The trends from these diagnostics consistently show no additional alpha losses due to interaction with RF waves. TRANSP predictions for the impact of ynergistic effects on alpha heating show up to a 42% increase in alpha electron heating and up to a 25% increase in alpha ion heating. These effects, however, become negligibly small, less than 1%, when alpha heating is compared to the total auxiliary heating power in the investigated JET pulses.

Studying Cation Exchange in {Cr7Co} Pseudorotaxanes: Preparatory Studies for Making Hybrid Molecular Machines.

In the design of dynamic supramolecular systems used in molecular machines, it is important to understand the binding preferences between the macrocycle and stations along the thread. Here, we apply 1H NMR spectroscopy to investigate the relative stabilities of a series of linear alkylammonium templated pseudorotaxanes with the general formula [H2NRR'][Cr7CoF8(O2CCH2 tBu)16] by exchanging the cation in solution. Our results show that the pseudorotaxanes are able to exchange threads via a dissociative mechanism. The position of equilibrium is dependent upon the ammonium cation and solvent used. Short chain primary ammonium cations are shown to be far less favourable macrocycle stations than secondary ammonium cations. Collision-induced dissociation mass spectrometry (CID-MS) has been used to look at disassembly of the pseudorotaxanes in a solvent-free environment and stability trends compared to those in acetone-d6. The energy needed to induce 50 % of the precursor ion loss (E50) is used and shows a similar trend to the equilibria measured by NMR. The relative stabilities of these hybrid inorganic-organic pseudo-rotaxanes are different to those of host-guest compounds involving crown ethers and this may be valuable for the design of molecular machines.

Numerical Analysis and Quantification of Transfer Efficiency Coupled with Capillary and Quadrupole Ion Guide in an API-MS System.

Ion trajectory simulation is a significant and useful tool for understanding ion transfer mechanisms within the first vacuum region of the atmospheric pressure ionization mass spectrometer (API-MS). However, the complex dynamic gas field and wide pressure range lead to inaccurate simulation and huge computational costs. In this work, a novel electrohydrodynamic simulation called the statistical diffusion-hard-sphere (SDHS) mixed collision model was developed for characterizing the ion trajectories. For the first time, the influence of the dynamic pressure on the ion trajectory is considered for simulation, which helps to avoid an intolerable computational cost. Comparing with the conventional Monte Carlo collision model, the SDHS method helps to improve the calculation accuracy of ion trajectories under the first vacuum region and reduce the computational cost for at least 12-folds. Simulation results showed that the maximum ion loss came from the gap of the electrodes. The distance of the capillary-quadrupole ion guide was also a non-negligible factor. The trend of quantitative experimental results matches the SDHS simulation results. The maximum ion transfer efficiencies of quantitative experiment and simulation were 55% and 52%, respectively. Moreover, three ions, caffeine, reserpine, and Ultramark 1621, were measured for evaluating the applicability of SDHS in real API-MS. The trend of experimental results showed good agreement with that of computation. And the results of caffeine further illustrated the reason that the small mass ion transfer efficiency decreased with increasing radio frequency voltage. SDHS method is expected to be useful in the design of ion guides for further improvement of the sensitivity of API-MS.