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Selective laser photodetachment of anions is a novel technique for isobar suppression in Accelerator Mass Spectrometry (AMS). Ion-laser interaction times on the order of ms required for near-complete isobar suppression are achieved by retarding the ions in a gas-filled radio frequency quadrupole cooler. Inside this RFQ, the cooled anion beam is overlapped collinearly with an intense cw-laser beam. Within the Ion Laser InterAction Mass Spectrometry (ILIAMS) project at the University of Vienna, a dedicated injector beamline has been coupled to the VERA-AMS facility to explore and develop this method. In this work, experimental investigations on ion beam transmission, stability and elemental selectivity of the new setup are presented. A 532 nm laser at 10 W transmitted power provides suppression factors larger than ten orders of magnitude for S− and MgO− under AMS conditions with simultaneous beam transmission for the ions of interest of up to 80%. The excellent ion identification capabilities of the subsequent AMS system also facilitate the study of destruction and formation of molecular anions inside the ion cooler. These kinetic and chemical reactions with the buffer gas provide additional elemental selectivity in certain cases, whereas others constitute a source of background. [ABSTRACT FROM AUTHOR]

• Photoelectron spectra (PES) of 2-hydroxypyridine/2-pyridone dimer anions were taken. • The PES showed a vertical detachment energy (VDE) of 1.21 ± 0.05 eV. • Density functional theory (DFT) results closely matched the measured VDE. • DFT showed that electron-induced proton transfer (EIPT) had occurred. • All combinations of neutral dimers showed EIPT between the neutral and its anion. Anion photoelectron spectroscopy and density functional theory computations were conducted on the 2-hydroxypyridine/2-pyridone tautomeric dimer anion system. Their experimentally-measured, composite vertical detachment energy (VDE) of 1.21 ± 0.05 eV compares well with their theoretically-determined VDE values of 1.15 eV and 1.20 eV, supporting our conclusion that intermolecular electron-induced proton transfer (EIPT) has taken place in these dimer anions. [ABSTRACT FROM AUTHOR]

High energy Neutral Beam Injection (NBI) is one of the methods being considered to heat EU DEMO plasma. A major issue of present NBI systems is the limited efficiency of the gas neutralizer (for ITER NBI ˜55%), which impacts on the overall system efficiency. An attractive method, but still undemonstrated at full performance, is the photo-neutralization of the negative D-ion beam, with an expected neutralization efficiency for a full-scale DEMO NBI up to 90%. A possible scheme for photo-neutralization is named RING (Recirculation Injection by Nonlinear Gating) where a laser second harmonic is generated and trapped within a non-resonant optical cavity. A mockup of the optical cavity is being operated in Consorzio RFX with a low repetition rate Nd:YAG laser (f = 10 Hz, λ = 1064 nm) to study the feasibility of the RING concept and its potentiality for a full-scale NBI photo-neutralizer. The 2nd harmonic generation efficiency has been measured using a set of 3 Lithium Triborate (LBO) crystals in a disk configuration, confirming the non-linearity of the process with the total crystal thickness. Losses during the 2nd harmonic recirculation in the cavity have been quantified, and the number of 2nd harmonic roundtrips has been estimated with photodiode measurements in order to evaluate the optical cavity performance. Further improvements are considered to increase the optical cavity photon accumulation. [ABSTRACT FROM AUTHOR]

The ITER Heating Neutral Beam injector (HNB) will be equipped with a beam source that will provide a negative beam of 40A (H or D). The R&D activities undertaken in Europe to pursue this challenging goal comprise three experiments: -ELISE – the half size ion source experiment operating in IPP Garching -SPIDER – the full size ion source experiment at Neutral Beam Test Facility (NBTF) site in Padua -MITICA - the full size full energy ITER injector prototype being also established at the NBTF The procurement of the beam source for SPIDER started in October 2012, when a contract between Fusion for Energy and Thales, Microwave & Imaging Sub-Systems (as group leader of a Consortium created with CECOM Srl, Galvano-T GmbH and Zanon SpA) was signed. The scope of the contract has been completed in October 2017 with the delivery of the SPIDER beam source at the NBTF site in Padova Italy. A review of the fabrication of the main parts and of the aspects of their assembly is reported in the paper, with a focus on some of the major issue encountered and the achievement of tight alignment tolerances of the accelerator. [ABSTRACT FROM AUTHOR]

An experimental study of 14 keV O− ions transmission through a tapered glass capillary with the inlet diameters of 580 μm, an outlet diameter of 68 μm and a length of 45 mm, has been performed in this work. It indicates that the O − ions transmitting through the tapered capillary had a density enhancement of about 5.5 times with the tilt angle of 0°. It was found that more than 97% of the transmitted and focused ions remained their initial charge state in central area. It's the first time that focusing effect was observed and was reported in experiment for negative ions. The angular distribution of transmitted ions was narrow. These results clearly indicated that the focusing effect can be achieved in the transmission process of keV O− ions through a tapered glass capillary. [ABSTRACT FROM AUTHOR]

Abstract The possibility of the current increasing of negative hydrogen ions H− extracted in the longitudinal direction from gas-feed-free Penning type ion source with metal hydride cathode by the electric cathodes bias has been investigated. The separation of negative ions from the extracted flux of charged particles was performed by an electromagnetic filter, which consists of a magnetic coil for electron diverting and a grid under positive potential for positive ion reflection. The optimum for the effective extraction of H− ions has been determined. The H− ion current of 10 μA was obtained at an input power of 6 W. Highlights • Hydrogen desorption in excited state from metal hydride increases the efficiency of H− formation in the plasma volume. • To increase the H− current one should supply a negative bias on a metal-hydride cathode. • The optimal value of the electric bias depends on the temperature of plasma electrons. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Pure lanthanide triiodides and their mixtures were studied by KEMS. • LnI4– and Ln2I7– ions were identified as charged vapor constituents. • Enthalpies of ion-molecular reactions were calculated. • Standard formation enthalpies of ions were determined. Abstract Ion-molecular equilibria LaI 4 – + LnI 3 = LnI 4 – + LaI 3 , Ln 2 I 7 – = LnI 3,cr + LnI 4 – (Ln = Ce, Pr, Gd, Tb, Tm, and Lu), and 3LaBr 4 – + 4LaI 3 = 3LaI 4 – + 4LaBr 3 in vapors over the LaI 3 -CeI 3 -PrI 3 -GdI 3 , LaI 3 -GdI 3 -TbI 3 -TmI 3 , and LaI 3 -LaBr 3 mixtures and the pure lanthanide triiodides were studied in the temperature range of 700–1050 K by Knudsen effusion mass spectrometry. The equilibrium constants were measured and the reaction enthalpies were calculated by the techniques of the second and third laws of thermodynamics. The standard formation enthalpies of ions, Δ f H °(298.15 K) (in kJ mol–1), were determined to be –832 ± 21 (LaI 4 –), –834 ± 23 (CeI 4 –), –834 ± 25 (PrI 4 –), –812 ± 24 (GdI 4 –), –813 ± 25 (TbI 4 –), –817 ± 23 (TmI 4 –), –806 ± 25 (LuI 4 –), –1399 ± 45 (La 2 I 7 –), –1402 ± 46 (Ce 2 I 7 –), –1417 ± 47 (Pr 2 I 7 –), –1356 ± 47 (Gd 2 I 7 –), –1365 ± 47 (Tb 2 I 7 –), –1366 ± 46 (Tm 2 I 7 –), and –1322 ± 47 (Lu 2 I 7 –). [ABSTRACT FROM AUTHOR]

Highlights • Modular concept of an RF-driven ion source with racetrack drivers. • Insights to the plasma flow in the source via a fluid code. • Caesium dynamics and consumption in the ion source. • Negative ion density above various materials as alternative to caesium. • Proof-of-principle experiments on laser neutralization and its challenges. Abstract Based on the requirements for heating and current drive of a DEMO (tokamak) device a neutral beam injection (NBI) system faces several challenges, from which the achievement of high wall-plug efficiency is the driving parameter for the beam line design. For boosting the wall-plug efficiency of the ITER NBI system from about 0.25 to target values around 0.4 (pulsed DEMO) or 0.5–0.6 (steady state DEMO), the standard gas neutralizer concept has to be modified or replaced by the innovative laser neutralizer concept for which the modular concept of the ion source allows for adaption. The technology developments of ITER's high power RF-driven ion source are continued by optimization of the RF-driver geometry and the resulting overlap of the driver plasmas in a large expansion chamber. Insights in the caesium evaporation and distribution in the ion source could allow for a reduction of the caesium consumption. On the other hand, the caesium dynamics influences the temporal source performance and the beam uniformity such that investigations on alternatives to caesium became an R&D task. Finally, the status of proof-of-principle experiments on the laser neutralization technique and its challenges for up-scaling from a lab scale experiment to a beam line are discussed. [ABSTRACT FROM AUTHOR]

Negative ion sources are fundamental components of neutral beam injectors (NBI), one of the main heating systems for fusion reactors. SPIDER is the full-scale prototype negative ion source for ITER NBIs. It is hosted in Padua as part of the Neutral Beam Test Facility (NBTF). It aims to extract up to 330 A m−2 of negative hydrogen ions from an inductively coupled plasma, generated inside 8 cylindrical drivers. The negative ion production is enhanced by caesium evaporation inside the source. In caesium-seeded negative ion sources, negative ions are produced close to the extraction apertures, and they are mainly generated by surface conversion of neutral atoms and positive ions impinging on the ion source walls, particularly on the plasma grid. The conversion yields depend on the energy distribution of these precursors, and so does the energy of those particles which are reflected as negative ions. The positive ion flow in the extraction region may also impact on the extraction probability of negative ions, via momentum transfer. Besides, in giant multi-driver RF sources such as SPIDER, a gradient of plasma potential is present in the expansion region Sartori et al. (2021), affecting the positive ion transport towards the caesiated plasma electrode and their energy. To approach this complex problem, a 3D test-particle Monte Carlo code for tracing plasma motion in SPIDER was developed. Positive ions species are generated in different positions within the plasma source volume and are tracked under the influence of electric and magnetic fields. Then, Monte Carlo collisions are used to simulate the interaction with predetermined backgrounds of plasma and neutrals, with profiles derived from experimental data. The particles are traced until they hit the ion source walls. Finally, the energy distribution of the different particle species impinging on the plasma grid (PG) are determined, and used to assess the generation and the energy distribution of the produced H −. • A 3D test particle Monte Carlo code was developed to track particles in SPIDER plasma. • Energy distributions at the plasma grid are valued for different boundary conditions. • Contributions to H − production yield are computed for ion and neutral species. [ABSTRACT FROM AUTHOR]

Compounds of lithium oxide, hydroxide and carbonate, mixed with silver, were prepared for use as a cathode in caesium-sputter ion source. The intention was to determine the procedure which would produce the highest intensity negative lithium beams over extended period and with maximum stability. The chemical composition and properties of the samples were analysed using mass-spectrometry, optical microscopy, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Analyses (EDX) and Raman spectroscopy. These analyses showed that the chemical transformations with components resulted from pressing, storage and bake out were qualitatively in agreement with expectations. Intensive negative lithium ion beams >1 μA were delivered using cathodes fabricated from materials with multicomponent chemical composition when the following conditions were met: (i) use of components with moderate enthalpy of formation; (ii) low moisture content at final stage of cathode production and (iii) small concentration of water molecules in hydrate phase in the cathode mixture. [ABSTRACT FROM AUTHOR]

The Ion Laser InterAction Setup (ILIAS) project at the University of Vienna aims at the exploration of negative ion beam filtering by selective laser photodetachment for applications in accelerator mass spectrometry (AMS). A gas-filled radio frequency quadrupole (RFQ) is used to decelerate and cool negative atomic and molecular ion beams with intensities of up to several hundred nA, and overlap them collinearly with a continuous wave (cw) laser beam. Ion-laser interaction times ranging from 500 μs to several ms allow for highly efficient, selective photodetachment depletion of disturbing ion species within these beams. The elemental selectivity of this technique is based on the differences in electron affinities, and therefore does not depend on relative differences in atomic numbers. It may therefore provide sufficient isobar suppression for new trace isotopes, which are not accessible with existing AMS techniques. The ILIAS RFQ cooler was characterized at a purpose-built test bench with respect to ion beam transmission, ion cooling capabilities and ion residence times as a function of injected ion current to assess its suitability for future AMS use. A 63 Cu − test beam of 600 nA was photodetached with more than 99.999% efficiency with a 532 nm laser at 10.8 W power. At the same time, ions of interest having electron affinities higher than the photon energy passed the cooler unaffected. Total ion losses were thus found to be below 50% of the sputter source output. Finally, first photodetachment experiments in connection with 26 Al detection demonstrated selective isobar suppression of MgO − vs. AlO − by more than 4 orders of magnitude. Currently, the RFQ cooler is moved to a new injector beamline at the Vienna Environmental Research Accelerator (VERA) for first applications of this novel technique at a state-of-the-art AMS facility. [ABSTRACT FROM AUTHOR]

A comparative investigation into the chemical reactions of a series of fluorinated fullerenes (C 60 F 18 , C 60 F 36 and C 60 F 48 ) with a variety of activated metal surfaces is reported. New ways of generating intense beams of metal fluoride anions are demonstrated: either in reactions of fluorinated fullerene vapours with hot W and Mo metal surfaces in a plasma ion source or by laser desorption/ionisation (LDI) of solid fluorinated fullerenes from various metal substrates (Al, Fe, Cu, Pt, W). In both cases, the resulting metal fluorides and their anions are formed in the highest oxidation state, yielding molybdenum and tungsten hexafluoride anions (plasma ion source), aluminium and iron tetrafluoride anions, and copper trifluoride anions (LDI). No reactions were observed with Pt and W in LDI. The reactivity of the metals towards fluorination correlates with their positions in the metal activity series. Relative yields of bare metal cations are dictated by their ionisation energy. The yield of metal fluoride anions is strongly dependent on the fluorine content of the fluorofullerenes. [ABSTRACT FROM AUTHOR]

• Heat loads calculations for the accelerator of the ITER HNB have been performed with fully 3D codes. • A different focal point was found for the beam halo, and thus a different heat load repartition among the grids. • The total heat load on each grid was confirmed to be within the acceptable range. • New scenarios were considered: out of perveance conditions and larger temperature for the negative ions. Among the heating and current drive system which are being developed for the ITER experimental reactor, 2 neutral beam injectors with a power of 16.5 MW each will be based on the acceleration of H −/ D − ions up to the energy of 870 keV / 1 MeV. Dealing with an accelerated beam power up to 40 MW, beam divergence, aiming and homogeneity have to be optimized to avoid damaging the beamline components or the grids of the accelerator. The design of the ITER HNB prototype, MITICA, was based on the coupling of several codes starting from experimental inputs available at that time. Heat loads, in particular, were estimated by the 2D version of the code Monte Carlo particle tracing code EAMCC. In the last years, a 3D version of the same code was developed and the operation of negative ion sources for fusion increased the knowledge concerning those parameters which are fundamental to estimate the expected heat loads. In this work, calculations are performed by EAMCC3D and the role of different source and accelerator parameters, such as the negative ion temperature and the beam halo, is highlighted. [ABSTRACT FROM AUTHOR]

Neutral Beam Injectors (NBI) for post-DEMO-like reactors must achieve a neutralization efficiency (fraction neutrals/ions) above 70%. To reach this, NBIs based on negative ions are necessary and an innovative concept of this type of injector is based on photo-neutralization. In this context, RAID (Resonant Antenna Ion Device), a linear helicon system located at the Swiss Plasma Center (SPC) in the Ecole Polytechnique Fédérale de Lausanne (EPFL), aims to study the production of negative ions (D− and H−) in the plasma volume. RAID is routinely operated with a single resonant birdcage antenna, located on one end of the vacuum chamber (1.4 m long and 40 cm diameter) at 0.3 Pa of pressure in D 2 and H 2 discharges. This antenna, excited at 13.56 MHz with a RF power up to 10 kW, generates helicon driven plasma beams extending all along the chamber when a DC axial magnetic field (standard value 200 G) is applied. Typical electron densities at the center of the column are 1–2.5 × 1018 m −3 and the electron temperature of 4–6 eV. In order to improve the symmetry as well as the homogeneity of plasma parameters along the axis, a second source was installed at the opposite end of the vacuum vessel and a complementary coil for the DC magnetic field was added. Axial profiles and 2D mappings of plasma density and temperature have been measured with a Double Langmuir Probe (DLP). Interestingly, for most phases, the relative RF phase of the two antennas influences the plasma causing very low frequency (few Hz) beating. In the future, other plasma diagnostics will be developed such as Thomson scattering, LIF (Laser Induced Fluorescence) and B-dot measurements to characterize in detail the wave propagation in RAID with two antennas and to understand better some phenomena observed during the test campaign described in this article. [ABSTRACT FROM AUTHOR]

The Gothenburg ANion Detector for Affinity measurements by Laser PHotodetachment (GANDALPH) has recently been built for measurements of electron affinities (EA) of radioisotopes. A first measurement campaign is aimed towards the determination of the EA of astatine, the rarest naturally occurring element on earth. In this work we present several upgrades of GANDALPH which have been implemented in order to facilitate EA measurements of radioisotopes where only low intensity ion beams (<1 pA) can be produced. [ABSTRACT FROM AUTHOR]

This contribution describes the design of a movable Langmuir probe system to be permanently installed in the SPIDER negative ion source. This diagnostic aims at measuring the axial profiles of plasma density, electron temperature and floating potential in both the driver and the expansion region, with a view to further investigate the positive ion dynamics. Furthermore, a deeper understanding of the plasma formation mechanism and of the RF coupling can be provided, e,g. via the estimation of the Electron Energy Distribution Function (EEDF) inside the driver. Thermal analyses were performed to define both the allowable duration of the probe exposure to the plasma and the extent of the voltage sweep. The maximum exposure time for the probe shaft is 10 s, thus a fast manipulation system is included in the design. The integration in the SPIDER source is described, considering all the limitations due to the space availability, the presence of the RF generators and the vacuum-compatibility requirements. To comply with all the constraints, several solutions are proposed for the probe head design. • Negative ion sources are necessary for high energy neutral beam injectors. • The beam optics are strongly related to the source plasma parameters. • It is necessary to investigate the source plasma properties with diagnostics. • A permanently installed movable Langmuir probe is designed for the SPIDER source. • Several technical aspects (vacuum-compatibility, RF noise) need to be addressed. [ABSTRACT FROM AUTHOR]

In sputter-type negative ion sources, the negative ion currents and ionization efficiencies are very dependent upon the creation of a sputter crater and formation of an intense plasma glow. This effect has many similarities with the well-known phenomena of hollow cathode discharges (HCDs). This paper discusses the phenomenological model related to conventional HCDs, including modes with injection of external energetic particles. We propose that HCDs play a major role in sputter-type negative ion sources. In this study, we evaluate the phenomenology of a discharge with a hollow cathode and derive an analytical formula that defines the neutral particle density inside the cathode cavity and substantiates how the classic HCD occurs in sputter-type negative ion sources. The cathode pit geometry was revealed by optical microscopy. Volt–ampere characteristics were investigated in order to compare it to typical discharges with hollow cathodes. In sputter-type negative ion sources, known as SNICS, discharge characteristics and observed light glow inside the cathode pit after its formation were very similar to data published on HCDs. The HCD phenomenon explains how the cathode current increases by orders of magnitude after creation of the cathode pit. The HCD effect in SNICS and similar sputter sources compliments existing mechanisms of negative ion production, especially ion pair production close to the cathode surface due to low energy ionization based on the collision–radiation model. The wealth of information accumulated over the last century on HCDs can be used to describe and explain the phenomenology of physics and operation of sputter negative ion sources. • Phenomenology of discharge with hollow cathode has been associated with Caesium sputter negative ion source SNICS. • Understanding processes in the SNICS is imperative to continuous development of this device and improving its efficiency. • The wealth of information on HCD can be used to explain the phenomenology of physics of sputter negative ion sources. [ABSTRACT FROM AUTHOR]

We have formed the Al(I)-containing molecule, benzophenone-aluminum, i.e., Ph 2 COAl, and studied it by conducting density functional theory calculations on both its neutral and anionic forms and by measuring the photoelectron spectrum of its anion. Our calculations identified two nearly iso-energetic anion isomers, (Ph 2 COAl) − , the vertical detachment energies (VDE) of which are in excellent agreement with our photoelectron spectrum. Natural population analysis (NPA) of Ph 2 COAl found the Al moiety to be positively charged by +0.81 e , indicating a strongly ionic bond between Al and Ph 2 CO, i.e., Ph 2 CO − Al + . [ABSTRACT FROM AUTHOR]

Using a static sector magnetic mass spectrometer MI-1201B, modified to record negative ions for resonant electron capture by molecules, the ion extraction time from the ionization chamber combined with this apparatus was measured up to several hundred microseconds. It was shown that the values obtained are anomalously great and they arise from the fact that part of the formed in the ionization chamber ions are adsorbed onto the chamber's surface. Those of them that were produced initially in the gas phase, namely the transient negative ions, with a finite lifetime (∼1 μs and greater), transform themselves, on the surface, into ‘infinitely living’ (stable) ions. As a result, the contribution of the stable ions to the total ion beam falsifies the ion's lifetime measurements performed with this instrument. [ABSTRACT FROM AUTHOR]

A new experimental system was recently developed to measure the mobility of both positive and negative ions: the Dual-Polarity Ion Drift Chamber (DP-IDC). This system is intended to better understand the transport properties of ions in gases relevant for the performance of large volume gaseous detectors like the Negative Ion Time Projection Chambers (NITPCs). In this work, we present a description of the experimental setup and technique used, and the initial studies carried out in Xe–S F 6 mixtures, whose interest has attracted attention as a possible alternative in searches for the neutrinoless double-beta decay. [ABSTRACT FROM AUTHOR]

There are number of ways in which weak electrification can affect the microphysics of clouds, with consequences for cloud lifetime, radiative properties, and precipitation efficiency. Kauffman [2011] suggested ions produced by direct current generators will add to and enhance the catalysing effects that cosmic ray ions are now known to produce in among other things, lowering nucleation barriers, stimulating charged particle growth and stability and increasing the scavenging rate in clouds. Thus to electrify the atmosphere ions can be generated artificially in abundance along with large electric field. Ions can be generated by the corona effect using Atmospheric electrifiers (a device used to generate negative ions) which makes use of corona discharge phenomenon to charge the air particles. Exact assessment of electric field and charge density distributions and the flow dynamics inside the electrifiers is essential to understand the particle behaviour inside the electrifiers. In this paper, a novel model of governing equations to evaluate the space charge density, electric field intensity and velocity of ionized airflow is suggested as a function of applied voltage. The Poisson and charge conservation equations are derived and hence can be used to estimate the electric field and charge density distributions. Navier stokes equation can be used to get the velocity of ionized airflow because of electric force on the air. Simulation is carried out to validate the proposed model and verify that velocity is function of input voltage and is proportional to it. [ABSTRACT FROM AUTHOR]

In the present paper the processes of resonant electron attachment by trifluoroacetic acid molecules (CF 3 COOH) and its deuterated analog (CF 3 COOD) leading to formation of fragment negative ions have been investigated by negative ion mass spectrometry. Inverse or small direct isotope effect was detected for majority of negative ions. It is expressed both in difference between cross-section of ion formation, and in resonance peak displacement over energy scale for isotopically substituted ions from CF 3 COOH and CF 3 COOD. Isotope effect of maximal magnitude σ (H) / σ (D) ≈ 19 was registered for (M−H/D) − ions at electron energy 0.73 eV, and formation of these ions was explained by the mechanism of tunneling predissociation. [ABSTRACT FROM AUTHOR]

A non-linear computational modelling of ions from the ground station for electrifying the atmosphere to make feasibility study of artificial rainfall system is proposed and analyzed. The model considers generation of intermediate ions and ionized airflow velocity. The governing electro hydrodynamic (EHD) equations of the model shows that the space charge density, electric field intensity and velocity of the ionized airflow are function of high input voltage applied to generate the ions. The number of ions generated and their velocity is proportional to the applied ion generator voltage. These artificial ions will be introduced in the atmosphere which will act in a similar manner as cosmic rays. These ions will ionize the aerosols and catalyze nucleation processes and thus electrify the atmosphere which will form cloud droplets to get artificial rain. The mathematical model to study the feasibility of artificial rainfall is also validated under favourable conditions. [ABSTRACT FROM AUTHOR]

B3LYP/6-311 + G(d,p) calculations of ground and electronically excited states of ethylene, chloroethylene, 1,1-dichloroethylene, 1,2-dichloroethylene- cis , 1,2-dichloroethylene- trans trichloroethylene and tetrachloroethylene molecules have been performed. Molecular orbitals images and orbital correlation diagram are given. The calculation results for chloroethylenes electronically excited states were compared with experimental data from the energy-loss spectra obtained and generally considered previously by C.F. Koerting, K.N. Walzl and A. Kupperman. Several new additional triplet and singlet transitions were pointed out in these spectra considering the calculation results. The finding of the additional transitions was supported by the UV absorption spectrum of trichloroethylene recorded in big cuvette (10 cm), where the first three triplet and two low-intensive forbidden singlet transitions were registered. The first triplet of this compound was recorded to be at the same energy as was found with the energy-loss spectroscopy. [ABSTRACT FROM AUTHOR]

Highlights: [•] Electron transfer. [•] Aliphatic amino acids. [•] Negative ion formation. [Copyright &y& Elsevier]

Highlights: [•] Low energy electrons trigger a variety of decomposition reactions in gas phase acetone and perfluoroacetone via dissociative electron attachment. [•] The reactivity of the isolated gas phase molecules is strongly suppressed on going to homogeneous clusters of acetone and perfluoroacetone. [•] Acetylene decomposes into C2 − and C2H−. [Copyright &y& Elsevier]

Highlights: [•] We investigated electron attachment to platinum(II) bromide. [•] Only Br− is observed upon electron capture by the molecule. [•] Two resonances are ascribed to Br− +PtBr and Br− +Pt+Br dissociation channels, respectively. [Copyright &y& Elsevier]

The operation in pulsating regime of gas-feed-free Penning-type H− ion source with metal hydride cathode and extraction in the longitudinal direction has been investigated. Hydrogen is stored in metal hydride in atomic state followed by the formation of rovibrationally excited H 2 * molecules due to the process of nonequilibrium desorption. It impacts on a Penning discharge ability to emit negative hydrogen ions in the longitudinal direction and provides local gas injection to the discharge without any external gas supply. The AC power input of 65 W during τ ≈ 15 μs was performed against the background DC one of 5 W. The extracted axial flux of charged particles was separated in an electromagnetic filter followed by the registration of H− current. The H− ion current of about 0.22 mA was obtained. In the DC regime it was only 5uA, which is order of magnitude below the current obtained with the present pulsating regime of source implementation. • Hydrogen uptake from metal hydride is the way of gas-feed-free ion sources creation. • Pulsating regime of discharge operation safely increases hydrogen desorbtion rate. • Metal hydride hydrogen activation results in efficient volume H− ions production. • Longitudinal extraction of H− ions from Penning-type ion source is possible in case of metal hydride cathode application. [ABSTRACT FROM AUTHOR]

Highlights: [•] We perform absolute photodetachment cross section measurements for HfF5 and WF5. [•] High precision is achieved with the animated beams method. [•] Isobar suppression using optical filtering is feasible for the case of WF5 with respect to HfF5. [ABSTRACT FROM AUTHOR]

Abstract: Numerical simulations of the multi-fluid equations are utilized to study the sheath structure in an acetylene plasma consists of electrons, different species of positive and negative ions, and charged nanosize dust particles. It is found that in the presence of negative ions spatially periodic fluctuations are developed in the profiles of the plasma and dust parameters. The fluctuations are enhanced with increasing the electronegativity, ion Mach number and neutral number density, while they are suppressed with increasing the dust Mach number. As the electronegativity increases, the incident dust flux on the wall decreases, whereas the positive ion flux increases. The sheath width is a descending function of the electronegativity, plasma number density, ion Mach number, and dust radius but increases monotonically with the neutral number density. [Copyright &y& Elsevier]

Abstract: The Cassini spacecraft Radio and Plasma Wave Science (RPWS) Langmuir Probe (LP) provides in-situ measurements of Titan's ionosphere. We present here data from 47 deep flybys in the time period October 2004–July 2012 of charge densities of positive and negative ions as well as electrons. These densities have been mapped with respect to altitude and solar zenith angle (SZA) in an altitude range of 880–1400km. The inferred electron number densities are consistent with earlier presented observational results. Negative ion charge densities exhibit a trend that exponentially increases towards lower altitudes within the covered altitude range. This is especially evident on the nightside of Titan (SZA >110°). The negative ion charge densities at the lowest traversed altitudes (near 960km) are inferred to be in the range 300–2500cm−3. The results show that very few free electrons (n e /n i ∼0.1–0.7) exist in the deepest regions (880–1050km) of Titan's nightside ionosphere. Instead the deep nightside part of Titan's ionosphere is dominated by both negatively and positively charged heavy (>100amu) organic ions. We therefore believe a dust/aerosol-ion plasma exists here, similar to what is found in noctilucent clouds in Earth's mesosphere. [Copyright &y& Elsevier]

Abstract: Negative corona discharge in wire to plane geometry was investigated by ion mobility-orthogonal acceleration TOF mass spectrometry (IMS-oaTOF). The formation of the ions in CD in synthetic air was studied under different gas flow, temperature and discharge current conditions. In standard flow mode we have detected formation of NO2 −·(HNO3), NO3 −·(HNO3) and NO3 −·(HNO3)2 ions even at relatively low water concentration (5ppm) and determined their reduced ion mobilities of 2.11, 2.02 and 1.75cm2 V−1 s−1. We have determined the lifetime of the NO3 −·(HNO3)2 ion at 295 and 308K of 7.0(±1.0)ms and 2.5(±1.0)ms respectively. In the reverse flow the CD in wire to plane geometry different negative ions were detected, dominated by O2 −(H2O) n (n =0,1,2) with reduced ion mobility of 2.27cm2 V−1 s−1 and additional ions NO3 − (2.29cm2 V−1 s−1) and N2O2 − (2.37cm2 V−1 s−1) present in the spectrum. [Copyright &y& Elsevier]

Abstract: To unravel the mechanisms of ion formation in the Middleton type cesium sputter negative ion source, we have acquired and analyzed the spectrum of the light emitted from the source region during sputtering of three different cathode materials; carbon, aluminum and copper. All cathodes were analyzed under the same source settings but with different total current output. The cathode region was observed from a distance of 3m and the emitted light was analyzed by a fiber coupled spectrometer with a wavelength range from 350 to 1100nm. The spectra showed clear differences depending on the cathode material. The emitted light from the carbon cathode consisted almost entirely of lines from neutral cesium and no lines from ionized cesium. Both metallic cathodes additionally displayed several lines originating from positively ionized cesium. A weak, broad feature between 470 and 510nm was also seen in the carbon spectrum. This feature was not present in spectra from the two metallic cathodes. These results may suggest different mechanisms of negative ion formation in the ion source depending on the cathode material. As a side effect of the measurement it proved relatively easy to determine the source temperature, in the range 1020–1215K depending on source settings, to an accuracy of ±30K from the black body radiation. [Copyright &y& Elsevier]

Abstract: The ITER [1] fusion device is expected to demonstrate the feasibility of magnetically confined deuterium–tritium plasma as an energy source which might one day lead to practical power plants. Injection of energetic beams of neutral atoms (up to 1MeV D0 or up to 870keV H0) will be one of the primary methods used for heating the plasma, and for driving toroidal electrical current within it, the latter being essential in producing the required magnetic confinement field configuration. The design calls for each beamline to inject up to 16.5MW of power through the duct into the tokamak, with an initial complement of two beamlines injecting parallel to the direction of the current arising from the tokamak transformer effect, and with the possibility of eventually adding a third beamline, also in the co-current direction. The general design of the beamlines has taken shape over the past 17 years [2], and is now predicated upon an RF-driven negative ion source based upon the line of sources developed by the Institute for Plasma Physics (IPP) at Garching during recent decades [3–5], and a multiple-aperture multiple-grid electrostatic accelerator derived from negative ion accelerators developed by the Japan Atomic Energy Agency (JAEA) across a similar span of time [6–8]. During the past years, the basic concept of the beam system has been further refined and developed, and assessment of suitable fabrication techniques has begun. While many design details which will be important to the installation and implementation of the ITER beams have been worked out during this time, this paper focuses upon those changes to the overall design concept which might be of general interest within the technical community. [Copyright &y& Elsevier]

Abstract: The interaction of 16keV Cu− ions with Al2O3 nano-capillaries of 50nm diameter and 10μm length was studied. The angular and charge state distributions of the transmitted particles were measured by a position-sensitive microchannel plate detector. It shows that transmitted particles appear as two peaks and consist of three charge states, Cu−, Cu0 and Cu+. As the tilt angle increases, more Cu− ions lose electrons resulting in the formation of Cu0 and Cu+ during multiple collisions with the capillary walls. Unlike previously reported results on highly charged ions, keV-energy Cu− ions undergo significant charge exchange processes with the inner walls of the capillaries. This indicates that the guiding effect is absent in the negative ion transmission under the very low ion current conditions. [Copyright &y& Elsevier]

Abstract: Titan tholins generated by complex processes (including ion–molecule reactions) in a laboratory plasma were investigated by ultrahigh resolution MS and tandem MS/MS measurements. Titan has a special interest in astrobiology because “in situ” measurements by the Cassini–Huygens spacecraft indicate the presence of complex organic molecules of prebiotic interest. The present work focuses on negatively charged ions that have not been systematically studied by ultrahigh resolution MS and MS/MS. The negatively charged ions were generated from a tholin sample by both laser desorption ionization (LDI) and electrospray ionization (ESI). The chemical compositions determined for the negatively charged ions clearly indicate the presence of highly unsaturated (H/C<1) species with high nitrogen content (presumably related to multiple cyano functionalities). This is characteristically different from the previously analyzed positively charged ions that are more saturated and contain amino and imino functionalities. Based on tandem MS/MS experiments and quantum chemical calculations we propose characteristic structural features for selected ions. They include open chain (C6N3 −) and aromatic ring structures (C10N5 −). The basic non-aromatic structural unit C2N3 − seems to play an important role and several structural “families” can be derived as HCN, HCCH and H2 “adducts” of this ion. [Copyright &y& Elsevier]

Abstract: In aqueous biological environment DNA is typically deprotonated. The metastable deprotonated DNA nucleobases are important reaction intermediates in low-energy electron induced damage to DNA. By comparing the metastable decay of small deprotonated DNA building blocks (thymine, thymidine, d-ribose, d-ribose 5-monophosphate) with the metastable decay of thymidine 5′-monophosphate and the hexameric oligonucleotide dT6 we show that the most intense fragmentation pathways of the individual components are inherited to their next larger compositions of one step further in complexity, i.e., from thymine and ribose to thymidine, from thymidine and 2-deoxyribose 5-monophosphate to thymidine 5′-monophosphate, and from thymidine 5′-monophosphate to thymine oligonucleotides. However, fragmentation channels that are dominant in the smaller, principle building blocks such as d-ribose and thymidine do not necessarily prevail beyond their composition, i.e., in thymidine 5′-monophosphate and thymine oligonucleotides. The comparison of the metastable decay mass spectra of molecules of increasing complexity reveals detailed fragmentation mechanisms and shows that the individual fragmentation pathways are determined by the initial deprotonation sites. [Copyright &y& Elsevier]

Abstract: Using a quadrupole mass spectrometer combined with an energy analyser, we have investigated the in-situ energy distribution of highly energetic ions generated during reactive sputtering of In–Sn alloy (IT) targets and non-reactive sputtering of Sn-doped In2O3 (ITO) ceramic targets. Ar+, In+, O+, O−, O2 −, InO− and InO2 − ions with kinetic energies greater than 40eV were clearly observed. Upon increasing the O2 flow ratio for reactive sputtering, the surface of the IT target changes from metal (metal mode) to oxide (oxide mode) via a state of mixed metal and oxide (transition region). O− ions with the kinetic energy corresponding to cathode voltage are generated at the oxide layer, which expands upon the target surface with increasing O2 flow ratio in the metal mode and the transition region. In contrast, the flux of 60-eV Ar+ ions decreases with increasing O2 flow ratio. The presence of 125- and 200-eV In+ ions is attributed to the dissociation of InSnO2 − and InO2 − with the kinetic energy corresponding to cathode voltage, respectively, while the presence of 40- and 150-eV O+ ions is attributed to the dissociation of InO2 − and O2 − with the kinetic energy corresponding to cathode voltage, respectively. [Copyright &y& Elsevier]

Abstract: This paper reviews the on-going design, R&D and procurement activities, mostly conducted within the ITER framework, on-going in Europe under the co-ordination of Fusion for Energy (F4E), in co-operation with the European Fusion Associations and aimed at the establishment of the ITER Heating Neutral Beam (HNB) system. [Copyright &y& Elsevier]

Abstract: This study deals with O2 − generation in corona discharge (CD) in point to plane geometry for single flow ion mobility spectrometry (IMS) with gas outlet located behind the ionization source. We have designed CD of special geometry in order to achieve the high O2 − yield. Using this ion source we have achieved in zero air conditions that up to 74% all negative ions were O2 − or O2 −(H2O). It has been demonstrated that the non-electronegative nitrogen positively influences the efficiency of O2 − generation in O2/N2 mixtures. The reduced ion mobility of 2.27cm2 V−1 s−1 has been measured for O2 −/O2 −(H2O) ions in zero air. Additional ions detected in zero air (less than 200ppb CO2) using the mass spectrometric and IMS technique were, NO2 −, N2O2 − (2.37cm2 V−1 s−1), NO3 −, N2O3 − and N2O3 −(H2O). The CO3 − and CO4 − ions have been detected after the introduction of 5ppm CO2 into zero air. [Copyright &y& Elsevier]

Abstract: Low energy electron attachment to gas phase carbonyl fluoride, F2CO, has been performed by means of a crossed electron-molecular beam experiment in an electron energy range from 0 to 30eV with an energy resolution of ∼0.5eV. The most intense signal is observed at 19amu due to F− and two other anionic species with lower intensities at 38 and 47amu assigned to F2 − and COF−, respectively. Anion efficiency curves of the three anions have been measured. Product anions (F− and COF−) are observed mainly in the low energy region arising from simple bond breaking, while F2 − is being produced from two bond cleavages with further structural and electronic rearrangement. Quantum chemical calculations on the electronic properties of F2CO have been performed in order to complement the experimental results. [Copyright &y& Elsevier]

Abstract: Low-energy 0⩽ E ⩽1.0eV electron elastic scattering from ground and excited Tm, Lu and Hf atoms has been investigated. Both total and differential cross sections have been calculated; the latter at the scattering angles θ =0°, 90° and 180°. The recent Regge-pole methodology has been used for the calculations. In the method the crucial electron–electron correlation effects are accounted for through the Mulholland formula. We find that the total cross sections are characterized generally by shape resonances, Ramsauer-Townsend minima and dramatically sharp long-lived resonances from which we extract the binding energies of the negative ions. Our extracted binding energy of the Hf− negative ion from the total cross section is compared with that of Pan and Beck . [Copyright &y& Elsevier]

Abstract: The use of electronegative species as primary ions considerably enhances the emission of positive secondary ions in SIMS. Considering furthermore that negative primary ions can be required due to instrumental configurations (e.g. the Cameca NanoSIMS 50 requires an opposite polarity of the primary and secondary ions), O− ion bombardment is employed in SIMS analysis. These O− ions are typically created in a duoplasmatron source, which suffers however from its low brightness and which is thus not suited for high resolution imaging applications. The development of new (electro)negative ion sources is thus necessary to optimize the analysis of electropositive elements in terms of lateral resolution and sensitivity. In this paper, we present the performance of a duoplasmatron ion source generating F−, Cl−, Br− and I− ion beams. In particular, we experimentally determine on a dedicated test bench the brightness of the source in the F−, Cl−, Br− and I− modes as a function of the gas pressure, the magnetic field strength and the arc current in the source. The obtained results are compared to the performances of the duoplasmatron in the standard O− mode. In this context, a five times higher brightness was found for F− (200A/cm2 sr) compared to the standard O− (42A/cm2 sr). [Copyright &y& Elsevier]

Abstract: We investigated dissociation dynamics of positive and negative ions of gaseous SiCl4 and SiCl4 adsorbed on Si(100) at ∼90K following Cl 2p core-level excitations. The Cl 2p →8a 1 * excitation of SiCl4/Si(100) leads to a significant enhancement of the yields of Cl+ and Cl−. Excitation of Cl 2p electrons to Rydberg orbitals near the Cl 2p ionization thresholds of gaseous SiCl4 enhances the production of anionic fragments Si− and Cl−. [Copyright &y& Elsevier]

Abstract: The effect of negative ions on the modulational instability properties of nonlinear dust acoustic (DA) waves in the electronegative dusty plasmas was investigated by considering Boltzmann-distributed electrons, negative ions, positive ions as well as positively charged dust grain under the ultraviolet irradiation. It is shown that the modulational instability properties of the DA waves were strongly affected by the temperature and proportion of negative ions. The modulational instability can occur only if the proportion of negative ions was smaller than critical value. The instability growth rate has a maximum value when the proportion of negative ions was a critical one in the unstable region. The effect of photoelectron generated by ultraviolet irradiation on the modulational instability of dust acoustic waves was also discussed by numerical method. [ABSTRACT FROM AUTHOR]

Abstract: Inner-shell photodetachment of negative ions has been investigated using the photon–ion merged beam technique for atomic and small cluster systems. The case of atomic systems is illustrated by reporting on the first measurements of the absolute cross-sections for the formation of Pt+, Pt2+, and Pt3+ following 4f and 5p inner-shell photoexcitation and detachment of Pt− 4f 145d 96s 2 2 D. The Pt3+ production channel is dominated by 4f detachment and allows for the first observation of a d-wave Wigner threshold law following single-photon absorption. Our measurements show that promoting a 5p electron into the 5d orbital produces a shape resonance, while promoting a 4f electron produces Feshbach resonances, demonstrating the importance of core–valence interactions. The photodetachment of small cluster systems is illustrated with the measurement and the calculation of K-shell photodetachment of size-selected B2 − and B3 − clusters. The experimental absolute photodetachment cross-sections exhibit bound resonances below threshold and two shape resonances above the K-shell threshold. Similar results were obtained for all of the cationic products observed, B+ and B2 + from B2 −, as well as B+, B2 + and B3 + from B3 −. The overall agreement between measured and calculated photodetachment cross-sections is very good. [Copyright &y& Elsevier]

Abstract: Using eclipse laser photo-detachment in conjunction with Langmuir probing, the density of O− ions in a reactive pulsed magnetron (100kHz, 55% duty) plasma has been determined at different times during the pulse period at a set of positions along the centre line axis of the discharge. The magnetron was operated at a fixed average power of 400W with an oxygen partial pressure of 10% of the total pressure 1.33Pa. The results show the plasma is weakly electro-negative, with a negative ion-to-electron density ratio α up to a maximum of 0.63. During the plasma on-phase (at all chosen measurement positions) the O− density was found to reach a maximum directly after initiation of the voltage pulse decreasing weakly during the rest of the on-phase. On the transition from on-to-off phases of the pulse the negative ion density was found to fall (by 60% both close and far from the target but only 10% near the discharge centre), with the O− density remaining almost constant during the rest of the afterglow. The spatial structure of the O− density reveals a distinct peak 75mm from the target close to but not at the position of the null in the magnetic field, falling by a factor of eight for increasing distances up to 30mm both towards and away from the target. The highest O− density recorded at this position was 1×1016 m− 3, at a time of 2.12μs into the pulse. From a comparison between on- and off-phase densities and using an intuitive model of the plasma, the results indicate that most negative ions are created in the bulk plasma. The density of target-borne O− ions is estimated to be about 1×1015 m− 3 varying little with position, possibly forming a beam-like structure. [ABSTRACT FROM AUTHOR]

Abstract: The interaction of 35ps laser pulses with methyl iodide clusters in the intensity region of 1012–3×1013 W/cm2 is studied at λ =266, 532 and 1064nm by means of time-of-flight mass spectrometry. At λ =532 and 1064nm the multielectron dissociative ionization (MEDI) of clusters results in highly charged atomic fragment (up to I7+) ion production of high kinetic energy. The explosion of the multiple charged cluster ions is found to be isotropic, while an asymmetric charge distribution prior to their fragmentation is observed. Moreover, negative ion formation is observed. The MEDI of clusters exhibits a dependence on laser polarization and the intensity thresholds for the observation of the fragment ions are determined for linear and circular laser polarization. These intensity thresholds are found to be about three orders of magnitude lower than those reported by experiments with 35ps laser pulses on CH3I monomers. For the observed MEDI of (CH3I) n clusters a mechanism is proposed. According to this mechanism, the clusters are initially single ionized by multiphoton absorption and an internal electric field is created within the cluster, which distorts the potential barriers. This distortion increases the probability for electron tunneling even at relatively low laser intensities, giving thus rise to the formation of negatively charged moieties within the clusters, which prevent the cluster elongation and facile further the tunneling process. This procedure results in a higher distortion of the internal barriers and an increased ionization of the clusters, which, due to increased repulsive forces, finally fragment leading to multiple charged high kinetic energy fragment ion production. [Copyright &y& Elsevier]

Abstract: Using the closed orbit theory, we give a clear physical picture description of the photodetachment of H− in the magnetic field near a metal surface. The photodetachment cross-section of this system is also derived and calculated. It is found that the effect of the metal surface can be considered as a varying electric field. The detached electron''s motion and the cross-section are similar to the case of the photodetachment of H− in parallel electric and magnetic fields. For a given ion-surface distance, the cross-section depends sensitively on the magnetic field strength. As the magnetic field strength is weak, the cross-section is the same as the photodetachment of H− near a metal surface. With the increase of the magnetic field strength, the number of the closed orbits increases and the photodetachment cross-section becomes much more complicated. This study provides a new understanding on the photodetachment process of negative ions in the presence of external fields and surfaces. [Copyright &y& Elsevier]