RF discharge-based plasma emitter

An injector of hydrogen atoms for plasma diagnostics in modern tokamaks has been developed at the Budker Institute of Nuclear Physics (Novosibirsk). The ion source of the injector produces a proton (helium ion) beam with a current of up to 2 A (1 A), an ion energy of up to 55 keV, a beam divergence of ～0.6\deg, and a pulse duration of up to 10 s. An RF discharge-based plasma emitter, which is one of the main parts of the ion source, is described. The emitter diameter is 72 mm, the ion current density is 120 mA/cm², and the inhomogeneity of the current density is ±6%. The beam is formed by a four-electrode ionoptical system with 163 round apertures. At a current of 2 A, the ion beam consists of 67% protons, 18% H ₂ ⁺ ions, and 15% H ₃ ⁺ ions, the total content of heavier ions in the beam being no higher than 2–3%.     

Experimental study of the dynamics of neutron emission from the GOL-3 multimirror trap

In experiments on the plasma heating and confinement in the GOL-3 multimirror trap, a deuterium plasma with a density of ～10¹⁵ cm^?3 and an ion temperature of 1–2 keV is confined for more than 1 ms. The plasma is heated by a relativistic electron beam. The ion temperature, which was measured by independent methods, reached 1.5–2 keV after the beginning of the beam injection. Since such a fast ion heating cannot be explained by the classical energy transfer from electrons to ions through binary collisions, a theoretical model of collective energy transfer was proposed. In order to verify this model, a new diagnostics was designed to study the dynamics of neutron emission from an individual mirror cell of the multimirror trap during electron beam injection. Intense neutron bursts predicted by this model were detected experimentally. Periodic neutron flux modulation caused by the macroscopic plasma flow along the solenoid was observed. The revealed mechanism of fast ion heating can be used to achieve fusion temperatures in the multimirror trap.     

Experimental study of the evaporation and expansion of a solid pellet in a plasma heated by an electron beam

Results are presented from experiments on the injection of solid pellets into a plasma heated by an electron beam in the GOL-3 device. For this purpose, two pellet injectors were installed in the device. The target plasma with a density of ～10¹⁵ cm^?3 was produced in a solenoid with a field of 4.8 T and was heated by a highpower electron beam with an electron energy of ～1 MeV, a duration of ～7 s, and a total energy of 120–150 kJ. Before heating, the pellet was injected into the center of the plasma column transversely to the magnetic field. The injection point was located at a distance of 6.5 or 2 m from the input magnetic mirror. Polyethylene pellets with a mass of 0.1–1 mg and lithium-deuteride pellets with a mass of 0.02–0.5 mg were used. A few microseconds after the electron beam starts to be injected into the plasma, a dense plasma bunch is formed. In the initial stage of expansion, the plasma bunch remains spherically symmetric. The plasma at the periphery of the bunch is then heated and becomes magnetized. Next, the dense plasma expands along the magnetic field with a velocity on the order of 300 km/s. A comparison of the measured parameters with calculations by a hydrodynamic model shows that, in order to provide such a high expansion velocity, the total energy density deposited in the pellet must be ～1 kJ/cm². This value substantially exceeds the energy density yielded by the target plasma; i.e., the energy is concentrated across the magnetic field onto a dense plasma bunch produced from the evaporated particle.     

Suppression of longitudinal losses in a gas-dynamic trap by using an ambipolar mirror

The efficiency of utilizing ambipolar mirrors for suppression of longitudinal losses of particles and energy in a gas-dynamic trap (GDT) was investigated. An additional relatively small axisymmetric mirror cell was installed in one of the facility ends. Hydrogen or deuterium atomic beams with an energy of 22 keV and equivalent current density of up to 1 A/cm² were injected into the additional cell at an angle of 90° to the facility axis. Trapping of the beams with a total power of 800 kW by the plasma in the additional cell leads to the formation of a hot ion population with an anisotropic velocity distribution, a mean energy of 13 keV, and a density of up to 4.5 × 10¹³ cm⁻³. It is shown that the confinement of hot ions in the additional cell is determined by classical processes, such as charge exchange on the beam atoms and collisional deceleration by electrons, in spite of the onset of Alfvén ion-cyclotron instability at fast ion densities higher than 2.5 × 10¹³ cm⁻³. The effect of ambipolar confinement manifests itself in that, at hot ion densities higher than 3 × 10¹³ cm⁻³, the flux density of ions escaping from the trap in the mode with beam injection decreases fivefold as compared to that without injection. In this case, the density of the Maxwellian plasma component in the central cell is about 2.5 × 10¹³ cm⁻³. The efficiency of suppression of longitudinal particle losses by the ambipolar mirror substantially exceeds estimates obtained for both collisional (gas-dynamic) and collisionless (adiabatic) confinement modes. Qualitatively, this is because, in the GDT experiments, the mode of warm plasma confinement is transitional between the gas-dynamic and adiabatic modes and the use of an ambipolar mirror facilitates a transition from the lossy gas-dynamic mode into a nearly adiabatic one.     

Applicability of TOF-SIMS for the assessment of lipid composition of cell membrane structures

Langmuir–Blodgett lipid films and plasma membranes of glioma cells were analyzed using timeof-flight secondary ion mass spectrometry (TOF-SIMS). Bi₃ ⁺ primary ion beam was determined to be most efficient in various experimental setups. TOF-SIMS was shown to be applicable for a quantitative analysis of model lipid structures, as well as plasma membranes of glioma cells U87MG in vitro. A combination of atomic-force microscopy and scanning electron microscopy yielded the depth resolution of ~10–20 nm for cell surface scanning by primary ion beam.     

Relation between electron exchange and nuclear vibrations in the H 2 + +H 2 + → H 3 + +p exothermic ion-molecular reaction

The effective cross section for the H ₂ ⁺ +H ₂ ⁺ → H ₃ ⁺ +p reaction in the energy range 5.7–11.5 eV is measured by the split beam method. The maximum of the cross section at an energy of ～8 eV is related to the production of the H ₄ ⁺⁺ compound system. The reaction threshold W _thr≈5 eV provides evidence in favor of the classical model of the H ₂ ⁺ ion with the charge fixed on one of the nuclei throughout the collision event.     

Characteristic features of energy transfer in the wall region of a lithium vapor discharge

A series of experiments with a fully ionized turbulent lithium plasma is described. Discharges with a heat flux density onto the wall of 1–3 kW/cm² and an electron density of ～10¹⁵ cm^?3 are obtained. The energy can be transferred to the wall by both Li⁺ and Li⁺⁺ ions. The measurements show that the photon flux corresponding to the main resonant transition of lithium atoms is a factor of 10⁴–10⁵ less than it could be if all the ions arriving at the wall recombined there. A mechanism is proposed for energy transfer onto the wall via the recombination of Li⁺⁺ ions to Li⁺ ions in the cold wall region of the discharge and the subsequent energy emission by Li⁺ ions.     

Production of H 3 + ions in low-energy collisions between hydrogen molecular ions

The effective cross section for the H ₂ ⁺ + H ₂ ⁺ → H ₃ ⁺ + p reaction in the energy range 5.7–11.5 eV is measured by the split beam method. The cross-section maximum at an energy of ～8 eV is related to the production of the H ₄ ⁺⁺ compound system. The reaction threshold W _thr ≈5 eV provides evidence in favor of the classical model with the H ₂ ⁺ ion charge fixed on one of the two nuclei during the entire collision event.     

pH-stat experiments in proximal renal tubules

Summary The pH-stat technique has been used to measure H⁺ fluxes in gastric mucosa and urinary bladder in vitro while keeping mucosal pH constant. We now report application of this method in renal tubules. We perfused proximal tubules with double-barreled micropipettes, blocked luminal fluid columns with oil and used a double-barreled Sb/reference microelectrode to measure pH, and Sb or 1n HC1-filled microelectrodes to inject OH^– or H⁺ ions into the tubule lumen. By varying current injection, pH was kept constant at adjustable levels by an electronic clamping circuit. We could thus obtain ratios of current (nA) to pH change (apparent H⁺-ion conductance). These ratios were reduced after luminal 10^–4 m acetazolamide, during injection of OH^–, but they increased during injection of H⁺. The point-like injection source causes pH to fall off with distance from the injecting electrode tip even in oil-blocked segments. Therefore, a method analogous to cable analysis was used to obtain H⁺ fluxes per cm² epithelium. The relation betweenJ _H ⁺ and pH gradient showed saturation kinetics of H fluxes, both during OH^– and H⁺ injection. This kinetic behavior is compatible with inhibition ofJ _H by luminal H⁺. It is also compatible with dependence on Na⁺ and H⁺ gradients of a saturable Na/H exchanger. H⁺-ion back-flux into the tubule lumen also showed saturation kinetics. This suggests that H⁺ flow is mediated by a membrane component, most likely the Na⁺–H⁺ exchanger.     

The plasma-membrane H+-ATPase from beet root is inhibited by a calcium-dependent phosphorylation

Several plasma-membrane proteins from beet root (Beta vulgaris L.) have been functionally incorporated into reconstituted proteoliposomes. These showed H⁺-ATPase activity, measured both as ATP hydrolysis and H⁺ transport. The proton-transport specific activity was 10 times higher than in plasma membranes, and was greatly stimulated by potassium and valinomycin. These proteoliposomes also showed calcium-regulated protein kinase activity. This kinase activity is probably due to a calmodulin-like domain protein kinase (CDPK), since two protein bands were recognized by antibodies against soybean and Arabidopsis CDPK. This kinase phosphorylated histone and syntide-2 in a Ca²⁺-dependent manner. Among the plasma-membrane proteins phosphorylated by this kinase, was the H⁺-ATPase. When the H⁺-ATPase was either prephosphorylated or assayed in the presence of Ca²⁺, both the ATP-hydrolysis and the proton-transport activities were slower. This inhibition was reversed by an alkaline-phosphatase treatment. A trypsin treatment (that has been reported to remove the C-terminal autoinhibitory domain from the H⁺-ATPase) also reversed the inhibition caused by phosphorylation. These results indicate that a Ca²⁺-dependent phosphorylation, probably caused by a CDPK, inhibits the H⁺-ATPase activities. The substrate of this regulatory phosphorylation could be the H⁺-ATPase itself, or a different protein influencing the ATPase activities. Received: 1 May 1997 / Accepted: 25 June 1997     

Study of the plasma in a preformed Z-pinch constriction

The development of a preformed constriction in cylindrical agar-agar loads at currents of up to 3 MA is studied experimentally. The loads 3–5 mm in diameter have a mass density of 0.1 g/cm³ and are filled with different materials. Due to the implosion of the constriction to a minimum size of 40–70 μm, a hot dense plasma (with the electron density n _e=10²² cm⁻³, electron temperature T _e=0.8–1.5 keV, and ion temperature T _i=3–12 keV) is produced. It is found that the ion temperature substantially exceeds the electron temperature. The lifetime of the high-temperature plasma determined from the FWHM of a soft X radiation (SXR) pulse is shorter than 5 ns, the radiation power of photons with energies of ≥1 keV is higher than 0.5×10¹⁰ W, and their total energy attains 50 J. High-speed photography in the VUV, SXR, and optical spectral regions indicates the protracted generation of the high-temperature plasma. Calculations by the two-dimensional ideal MHD model of the Z-pinch show that the most important consequence of the protracted plasma generation in the constriction region is that the current is intercepted by a freshly produced plasma. In the course of plasma generation, the current near the axis inside the region of radius 50 μm is at most one-half of the total current. After the plasma generation comes to an end, almost the entire current is concentrated in this region for several nanoseconds; this process is accompanied by a sharp increase in the plasma temperature. __________ Translated from Fizika Plazmy, Vol. 27, No. 12, 2001, pp. 1101–1110. Original Russian Text Copyright ? 2001 by Bakshaev, Blinov, Vikhrev, Gordeev, Dan’ko, Korolev, Medovshchikov, Nedoseev, Smirnova, Tumanov, Chernenko, Shashkov.     

Ion-molecule condensation reactions: A mechanism for organic synthesis in ionized reducing atmospheres

The CH₃ ⁺ ion, formed in ionized methane, undergoes consecutive eliminative condensation reactions with methane to form the carbonium ions C₂H₅ ⁺, i-C₃H₇ ⁺ and t-C₄H₉ ⁺. AtT<500°K, \(N_{CH_4 } \) ?10¹⁶ cm^?3 these ions react with NH₃ in competitive condensation-H⁺ transfer reactions, e.g. $$\begin{gathered} C_2 H_5 ^ + + NH_3 \xrightarrow{M} C_2 H_5 NH_3 ^ + \hfill \\ - - - \to NH_4 ^ + + C_2 H_4 \hfill \\ \end{gathered} $$ At particle densities of \(N_{CH_4 } \) <10¹⁶ cm^?3 proton transfer is the only significant reaction channel. At \(N_{CH_4 } \) >10¹⁷ cm^?3 condensation constitutes 5–20% of the overall reactions. The product of the condensation reaction further associates with CO₂ to form C₂H₅NH₃ ⁺·CO₂; the atomic composition of this cluster ion is identical with the protonated amino acid alanine. The carbonium ions i-C₃H₇ ⁺ and t-C₄H₉ ⁺ condense also with HCN to yield protonated isocyanides. HCNH⁺ also appears to condense with HCN atT>570°K, and form cluster ions with HCN at lower temperatures. The rate constants of the condensation reactions vary with temperature and pressure in a complex manner. Under conditions similar to those on Titan at an altitude of 100 km (T=100–150°K, \(N_{CH_4 } \) ≈10¹⁸ cm^?3), with a methane atmosphere containing 1% H₂ and traces of NH₃ and H₂O, ion-molecule condensation reactions followed by H⁺ transfer are expected to lead to the atmospheric synthesis of C₂H₆, C₃H₈, CH₃OH, C₂H₅OH and the terminal ions NH₄ ⁺, CH₃NH₃ ⁺ and C₂H₅NH₃ ⁺. At higher temperatures (250°K<T<400°K), the synthesis of i-C₄H₁₀, i-C₃H₇OH and t-C₄H₉OH and of the ions i-C₃H₇NH₃ ⁺ and t-C₄H₉NH₃ ⁺ is also expected. Electron recombination of the terminal ions may yield amines, imines and nitriles. Cycles of protonation and dissociative recombination of the alkanes and alcohols produced in condensation reactions will also produce unsaturated hydrocarbons, ketones and aldehydes in the ionized atmosphere.     

Nitric Oxide Mediates Root K+/Na+ Balance in a Mangrove Plant,Kandelia obovata,by Enhancing the Expression of AKT1-Type K+ Channel and Na+/H+ Antiporter under High Salinity

It is well known that nitric oxide (NO) enhances salt tolerance of glycophytes. However, the effect of NO on modulating ionic balance in halophytes is not very clear. This study focuses on the role of NO in mediating K⁺/Na⁺ balance in a mangrove species, Kandelia obovata Sheue, Liu and Yong. We first analyzed the effects of sodium nitroprusside (SNP), an NO donor, on ion content and ion flux in the roots of K. obovata under high salinity. The results showed that 100 μM SNP significantly increased K⁺ content and Na⁺ efflux, but decreased Na⁺ content and K⁺ efflux. These effects of NO were reversed by specific NO synthesis inhibitor and scavenger, which confirmed the role of NO in retaining K⁺ and reducing Na⁺ in K. obovata roots. Using western-blot analysis, we found that NO increased the protein expression of plasma membrane (PM) H⁺-ATPase and vacuolar Na⁺/H⁺ antiporter, which were crucial proteins for ionic balance. To further clarify the molecular mechanism of NO-modulated K⁺/Na⁺ balance, partial cDNA fragments of inward-rectifying K⁺ channel, PM Na⁺/H⁺ antiporter, PM H⁺-ATPase, vacuolar Na⁺/H⁺ antiporter and vacuolar H⁺-ATPase subunit c were isolated. Results of quantitative real-time PCR showed that NO increased the relative expression levels of these genes, while this increase was blocked by NO synthesis inhibitors and scavenger. Above results indicate that NO greatly contribute to K⁺/Na⁺ balance in high salinity-treated K. obovata roots, by activating AKT1-type K⁺ channel and Na⁺/H⁺ antiporter, which are the critical components in K⁺/Na⁺ transport system.     

Gastric acid secretion in the chicken: Effect of histamine H2 antagonists and H+/K+-ATPase inhibitors on gastro-intestinal pH and of sexual maturity calcium carbonate level and particle size on proventricular H+/K+ ATPase activity

• 1.1. Cimetidine was more potent 4hr after a single injection of 25 or lOOmg/kg body wt in increasing gastric pH than other H₂ receptor antagonists, ranitidine and famotidine but was less efficient than H⁺/K⁺-ATPase inhibitors. Omeprazole rose proventricular and gizzard pH at a lower dose than SCH 28080 and Ro 18-5364 (30, 50 and 200 mg/kg body wt, respectively).
• 2.2. Proventricular and gizzard pH values were maximal 1 and 4 hr after a single injection of 7.5 μmol/kg body wt omeprazole. Inhibition of acid secretion was maintained for 24 hr after an injection of 100 μmol/kg.
• 3.3. H⁺/K⁺-ATPase activity in vitro was 10μimol P_i/hr/mg protein in the microsomal fractions of the proventriculus. It was doubled by nigericine and inhibited by SCH 28080. However, western blots by high specific H⁺/K⁺-ATPase monoclonal antibody 95-A3 and 95–111 recognized a 42kDa band but hardly exhibited the specific 95 kDa band recognition.
• 4.4. Chickens and immature pullets showed a higher H⁺/K⁺ -ATPase activity than laying hens. Calcium level of the diet did not affect the enzyme activity but coarse particles of calcium fed to pullets or laying hens enhanced the H⁺/K⁺-ATPase activity when compared with ground particles.

     

Functional Identification of H<Superscript>+</Superscript>-ATPase and Na<Superscript>+</Superscript>/H<Superscript>+</Superscript> Antiporter in the Plasma Membrane Isolated from the Root Cells of Salt-Accumulating Halophyte <Emphasis Type="Italic">Suaeda altissima</Emphasis>

A membrane fraction enriched in plasma membrane (PM) vesicles was isolated from the root cells of a salt-accumulating halophyte Suaeda altissima (L.) Pall. by means of centrifugation in discontinuous sucrose density gradient. The PM vesicles were capable of generating ΔpH at their membrane and the transmembrane electric potential difference (Δψ). These quantities were measured with optical probes, acridine orange and oxonol VI, sensitive to ΔpH and Δψ, respectively. The ATP-dependent generation of ΔpH was sensitive to vanadate, an inhibitor of P-type ATPases. The results contain evidence for the functioning of H⁺-ATPase in the PM of the root cells of S. altissima. The addition of Na⁺ and Li⁺ ions to the outer medium resulted in dissipation of ΔpH preformed by the H⁺-ATPase, which indicates the presence in PM of the functionally active Na⁺/H⁺ antiporter. The results are discussed with regard to involvement of the Na⁺/H⁺ antiporter and the PM H⁺-ATPase in loading Na⁺ ions into the xylem of S. altissima roots.     

ATP-dependent and ionophore-induced proton translocation in pea stem microsomal vesicles

The presence of an electrogenic pump in pea stem microsomal vesicles has already been demonstrated, but no evidence on the nature of the electrogenic ion has been presented (Rasi-Caldogno, F., De Michelis, M.I. and Pugliarello, M.C. (1981) Biochim. Biophys. Acta 642, 37–45). In this work we tested the usefulness of the ΔpH probe Acridine orange to monitor both ATP-dependent and ionophore-induced H⁺ fluxes in pea stem microsomal vesicles. The H⁺/K⁺ exchanger nigericin causes a marked uptake of protons into the vesicles that can be followed, with similar results, both as Acridine orange absorbance changes and pH changes of the external medium. ATP induces an uptake of Acridine orange into the vesicles which is reversed by FCCP and abolished by the presence of Triton X-100 in the incubation medium, thus indicating an inward, ATP-driven, H⁺ translocation. The ATP-dependent acridine orange uptake is Mg²⁺-requiring and KCl-stimulated. Such activity is inhibited by two specific ATPase inhibitors, dicyclohexylcarbodiimide and diethylstilbestrol, while it is unaffected by oligomycin and Na₃VO₄. These results show that Acridine orange is a useful probe to measure pH gradients in our membrane system and are consistent with the hypothesis that an ATPase of plasmalemma may act as a proton pump.     

Generation of dense multicharged ion flows from an ECR plasma confined in a quasi-gas-dynamic magnetic cusp trap

The possibility of generating dense multicharged ion beams with a current density as high as ～1 A/cm² from an ECR plasma confined in a quasi-gas-dynamic cusp trap is studied both theoretically and experimentally. The most important advantages of this type of ion source are that the plasma in the cusp is stabile against MHD perturbations and that a trap intended to operate at fairly high pump-field frequencies (above 30 GHz) is relatively inexpensive. A theoretical model of confinement of a high-density nonequilibrium ECR plasma (T _e ? T _i ) in an open magnetic trap is proposed and results are presented from model experiments with an ～30-cm-long cusp trap (here, by the cusp length is meant the volume of a paraxial magnetic tube divided by the area of its cross sections in magnetic mirrors) pumped by a pulsed microwave field with a frequency of 37.5 GHz and power of 100 kW. The possibility of achieving a quasi-gas-dynamic regime of plasma confinement of an ECR plasma in a cusp trap is demonstrated. Ion beams with a average ion charge number of 2–4 (depending on the sort of working gas) and current densities unprecedented for ECR sources are obtained. Good agreement between theoretical and experimental results makes it possible to reliably predict the ion beam parameters that can be achieved at even higher microwave frequencies.     

Methodology in the radiolysis of biochemical compounds with cyclotron beams at low flux densities.

A modification of the standard beam-optics of the LBL 88-Inch Cyclotron now makes it practicable to use cyclotron radiations in the detailed study of the effects of linear energy transfer (LET) in the radiation chemistry of organic compounds in the solid state. Dosages and dose-rates are comparable to those employed in conventional γ-ray studies. The modification involves passing the focused beam through a pair of “beam-sweeping” electromagnets so that a circular target area up to 10 cm in diameter can be uniformly irradiated with beams in the nanoamp range. Yield data are given for the radiolysis of the Fricke dosimeter with beams of H⁺, H⁺², Be⁺⁴, C⁺⁶ and Ne⁺¹⁰ at ～10 MeV per nucleon. Preliminary data on the effects of LET in the radiolysis of solid glycine are reported.     

An efficient method for extracting plasma ions in laser isotope separation systems

The possibility of using a Hall-current accelerator to extract ions from a partially ionized plasma produced by selective laser isotope photoionization of atomic vapor is examined. A mechanism for ion acceleration is investigated using one-dimensional time-dependent equations of two-fluid magnetohydrodynamics. The current cutoff due to the ion space charge is prevented by electron emission. It is shown that, at an accelerating voltage of 25–50 V and emission current density of several mA/cm², the ion component is accelerated throughout the entire plasma volume up to a velocity of ～10⁵ cm/s in a few microseconds. The influence of resonant charge exchange and secondary ionization by electrons on both the acceleration dynamics and selectivity degradation is taken into account. It is shown that the Hall-current extractor allows one to avoid selectivity degradation even when the plasma size exceeds the charge-exchange mean free path by one order of magnitude.