Microwave-accessibility conditions estimated by plasma parameters obtained experimentally on electron cyclotron resonance ion source.

We insert two probes in the upstream and the downstream regions with respect to the electron cyclotron resonance (ECR) zone which is formed at the center of mirror fields. We measure simultaneously plasma parameters in those regions by each of them under the same operating condition. We measure ion saturation currents Iis and electron energy distribution functions at two positions. We obtain measurement results that suggest the more efficient ECR on the side closer to the microwave-launchings than those on the other side. It is consistent with the accessibility condition of the right-hand polarization wave. We also compare the charge state distributions of Ar ion beams extracted in the case of launching microwaves from the coaxial semi-dipole antenna and those from the rod antenna. We observe the higher multicharged ion beam currents at the low microwave powers in the case of the rod antenna than those in the case of the coaxial semi-dipole antenna. We also confirm stable increasements of ion beam currents at considerably high microwave powers in the case of the coaxial semi-dipole antenna. Based on the experimental results, we propose a new microwave-launching method, "dual-ECR heating" and report its preferable preliminary experimental results in this paper.

Coaxial semi-dipole antenna microwave feeding on electron cyclotron resonance multicharged ion source.

How to produce multicharged ions efficiently on an electron cyclotron resonance ion source (ECRIS) has been investigated at Osaka University. Notably, in recent years, we have focused on heating by new resonance superimposing to electron cyclotron resonance (ECR) plasma. To evaluate its efficiency, we need to know the maximum efficiency of heating with ECR alone, and then, further optimization of ECR heating is required. In consideration of wave propagation, we installed the coaxial semi-dipole antenna on the mirror end along the geometrical axis of the vacuum chamber. We aim at exciting the strength of right-hand polarization (RHP) waves for efficient ECR because RHP waves give rise to ECR. We measure plasma parameters by Langmuir probes and charge state distributions (CSDs) of the extracted ion beams and investigate their qualitative tendencies to incident microwave powers and pressures. We compare the qualitative trend of ion beams and their CSD on microwave power in the case of both the microwave feeding system by the coaxial semi-dipole antenna and that by the rod antenna. Differences between the microwave feeding system before improving and then after upgrading are made clear.

Improving transport and optimizing deceleration of ion beams from electron cyclotron resonance multicharged ion sources.

Electron cyclotron resonance ion sources (ECRISs) are widely applied for ion beam applications, e.g., plasma processing, cancer therapy, and ion engine of an artificial satellite. In our ECRIS, we aim at producing and extracting various ion beams from this device, in particular, Xeq+ ion beams at low energy. In the aerospace engineering field, there are problems of accumulated damages on various component materials caused by low energy of Xe ions from the engine. There are not enough experimental sputtering data for satellite materials at the Xeq+ in the low energy region. Then, we are trying to investigate the sputtering yield experimentally by irradiating the low energy Xe ion beams. To perform this experiment, it is necessary to acquire a certain amount of beam current with low energy. Then, we generate the low energy ion beams by the following steps: First, the ion beams are extracted from the ECRIS at high voltage. Next, these are transported to an ion beam irradiation system (IBIS). Finally, the ion beams are decelerated by the deceleration voltage in the IBIS. We adjusted the beamline. We measure the characteristics of the transport efficiency and decelerated ion beam currents. In this paper, we describe the experimental setup using an existing ECRIS for decelerated heavy ion beams and the results of decelerated ion beam currents.

Upper hybrid resonance heating experiments by X-mode microwaves on electron cyclotron resonance ion source.

We have considered the accessibility condition of electromagnetic and electrostatic waves propagating in an electron cyclotron resonance (ECR) ion source (ECRIS) plasma and then investigated experimentally their correspondence relationships with production of multicharged ions. It has been clarified that there exists an efficient configuration of ECR zones for producing multicharged ion beams and has been suggested that a new resonance, i.e., upper hybrid resonance (UHR), must have occurred. We have been trying to perform advanced experiments with 4-6 GHz X-mode microwaves to the 2.45 GHz ECRIS plasma, and we have succeeded in enhancing the production of multicharged ions by launching X-mode microwaves of these bands. Furthermore, at the same time, we have observed sharp increases in electron energy distribution functions in the ECRIS plasma by means of probe methods. It has been concluded that the UHRs must have occurred when applying multiplex microwaves with their frequencies away from those frequencies for ECR in the ECRIS. In this paper, we will describe in brief the theoretical background and the results of these new experiments.

Improving multipole magnets and background vacuum conditions on electron cyclotron resonance ion sources.

Electron cyclotron resonance ion sources (ECRISs) are used in various fields such as accelerator physics, engineering, cancer therapy, and ion engines in the satellite. We are aiming to improve the production of multicharged ions efficiently at the point of view from the length of multipole magnets and vacuum conditions in the ECRIS. The diameter of the connection pipe between the main chamber and diffusion pump was made larger to improve vacuum conductance. Moreover, the length of multipole magnets with the direction along the geometrical axis in the ECRIS was extended. The effects of these improvements are investigated experimentally to measure the pressure in the vacuum chamber, beam intensity, charge state distributions of extracted ion beams, and plasma parameters. The purity of extracted ion beams and magnetic confinement have been enhanced. These results are expected to have positive effects on the production of various species and synthesized ion beams, e.g., production of iron endohedral fullerene in the future experiments in the ECRIS.

Strict in-plane alignment control of block-copolymer-templated mesostructured silica films using an alignment-controlling agent.

An alkoxysilane with an alkyl chain is introduced as an alignment-controlling agent of a block-copolymer-templated mesostructured silica film. Use of the alkylalkoxysilane achieves the alignment of the mesochannels of a triblock-copolymer-templated film by an intermolecular interaction with a rubbing-treated polyimide film. Co-use of an alkoxysilane with a hydroxymethyl group as a hydrophobicity reducing agent improves the alignment close to that of the film prepared using an alkyl surfactant. This concept widens the range of the structural period of aligned mesoporous films and thus widens the useful range of the anisotropic optical properties.

Lattice matching in the epitaxial formation of mesostructured silica films.

Crystallographic orientation of mesostructured silica films on a substrate drastically changes when the substrate is modified with an anisotropic surface. The [01] axis of a two-dimensional (2D) hexagonal structure of the film prepared on a polyimide surface using C(22)EO(20) as a structure-directing agent changes from perpendicular to parallel with respect to the substrate after a rubbing treatment of polyimide, which is accompanied by the simultaneous unidirectional alignment of the cylindrical pores in the plane of the film. The normal direction of the film is [21¯], which has never been observed in the mesostructured silica films reported so far including those with controlled in-plane alignment of the mesochannels. The change of the orientation with respect to the substrate can be explained by the increased lateral distance between the adjacent surface micelles, which is caused by the elongation of the alkyl chains of the surfactant molecules induced by the adsorption onto the polymer surface with a molecular-level anisotropy. These results show that the total structural orientation of the mesostructured silica film is determined by the matching of the intrinsic lattice constant of the mesostructured silica with that of the surface micelle structure on a substrate.

Exceptionally strong Bragg diffraction from a mesoporous silica film pretreated with chlorotrimethylsilane toward application in X-ray optics.

Exceptionally strong Bragg diffraction from a mesoporous silica film is achieved by exposing the as-deposited film to vapor of chlorotrimethylsilane (Me(3)SiCl) before extracting the surfactant. The intensity of the X-ray diffraction peak increased 7 times after the surfactant removal and it approached 30% reflectivity. This large increase of diffraction intensity cannot be explained simply by the improved contrast of the electron density, and rearrangement of the pore wall during the Me(3)SiCl vapor treatment is suggested. It is shown by infrared spectroscopy that Me(3)SiCl with a high grafting reactivity effectively caps the silanol groups and prevents the following condensation, which causes the structural degradation. The substitution of the hydrogen atom of hydroxyl groups with trimethylsilyl groups should help the improvement of the structural regularity by reducing the hydrogen bonds in the pore wall. The achieved strong diffraction opens the gate for the application of these regular mesoporous films prepared by a self-assembly process to optical elements in the X-ray region.

Remarkable birefringence in a TiO2-SiO2 composite film with an aligned mesoporous structure.

Mesoporous titania-silica composite films with highly aligned cylindrical pores are prepared by the sol-gel method using a substrate with structural anisotropy. The strong alignment effect of a rubbing-treated polyimide film on a substrate provides a narrow alignment distribution in the plane of the film regardless of the fast condensation rate of titania precursors. The collapse of the mesostructure upon the surfactant removal is effectively suppressed by the reinforcement of the pore walls with silica by exposing the as-deposited film to a vapor of a silicon alkoxide. The existence of a silica layer on the titania pore wall is proved from the distributions of Ti and Si estimated by the elemental analysis in high resolution electron microscopy. The obtained mesoporous titania-silica composite film exhibits a remarkable birefringence reflecting the highly anisotropic mesoporous structure and the high refractive index of titania that forms the pore wall. The Δn value estimated from the optical retardation and the film thickness is larger than 0.06, which cannot be achieved with the conventional mesoporous silica films with uniaxially aligned mesoporous structure even though the alignment of the pores in the films is perfect. These inorganic films with mesoscopic structural anisotropy will find many applications in the field of optics as phase plates with high thermal/chemical/mechanical stabilities.

Epitaxial-like growth of anisotropic mesostructure on an anisotropic surface of an oblique nanocolumnar structure.

Tetrahedral amorphous carbon (ta-C) films with nanoscale structural anisotropy, which are obliquely deposited on a substrate by a filtered cathodic vacuum arc deposition (FAD) technique, allow anisotropic growth of mesostructured silica films thereon. The ta-C films have a uniformly tilted nanoscale columnar structure, which is caused by the self-shadowing effect during the oblique deposition, and consequently, the surface of the film can be morphologically anisotropic when the deposition angle is large enough. When silica films with a two-dimensional hexagonal mesostructure are grown under hydrothermal conditions on these ta-C films, the cylindrical mesochannels are aligned perpendicularly to the deposition direction of ta-C. The distribution of the in-plane alignment direction of the mesochannels can be controlled by the deposition angle of ta-C; it becomes narrower with the increase of the deposition angle and the consequent increase of the surface roughness. The observed alignment of the mesochannels is caused by the anisotropic accommodation of the surfactant molecules on the structurally anisotropic surface of the ta-C films, which is consistent with the fact that the ta-C films prepared at small deposition angles with smoother surface morphology have little alignment controllability. The ta-C film can be removed with the surfactant by calcination, allowing the formation of an aligned mesoporous silica film directly on a substrate. In contrast to this, obliquely evaporated SiO(2) films with a distinct tilted columnar structure and an anisotropic surface morphology provide neither continuous film formation nor controlled alignment of mesochannels even after providing hydrophobicity by a silylation process. This suggests the specificity, in particular, intrinsic strong hydrophobicity, of the ta-C films for the aligned mesostructured silica film formation.

Formation of multinuclear metal-terpyridyl complexes covalently bound to carbon substrates.

Multinuclear complexes consisting of metal ions and a bis(terpyridyl) ligand were covalently bound to carbon substrates. The bonding of the complexes is initiated by the bonding of phenylterpyridine (PT) on the substrates using its in-situ-generated diazonium derivative, followed by stepwise coordination of the metal ions and the ligand on it. The bonding of the PT and the formation of the multinuclear complexes were confirmed by XPS, AFM, and CV measurements. The heterogeneous rate constant (k) at the Co complex-substrate interface was evaluated by chronoamperometry (CA). The estimated high k = (2.9-3.6) x 10(3) s(-1)) would be attributed to the C-C bond at the interface without interrupting the conjugation. These multinuclear complexes bound to the carbon substrates can facilitate electron transfer from redox species such as enzymes.

Dye-sensitized TiO2 solar cells using imidazolium-type ionic liquid crystal systems as effective electrolytes.

A novel ionic liquid crystal (ILC) system (C(12)MImI/I(2)) with a smectic A phase used as an electrolyte for a dye-sensitized solar cell (DSSC) showed the higher short-circuit current density (J(SC)) and the higher light-to-electricity conversion efficiency than the system using the non-liquid crystalline ionic liquid (C(11)MImI/I(2)), due to the higher conductivity of ILC. To investigate charge transport properties of the electrolytes in detail, the exchange reaction-based diffusion coefficients (D(ex)) were evaluated. The larger D(ex) value of ILC supported that the higher conductivity of ILC is attributed to the enhancement of the exchange reaction between iodide species. As a result of formation of the two-dimensional electron conductive pathways organized by the localized I(3)- and I- at S(A) layers, the concentration of polyiodide species exemplified by I(m)- (m = 5, 7, ...) was higher in C(12)MImI/I(2). However, as the increment of the concentration of polyiodide species is less than that of D(ex), the contribution of a two-dimensional structure of the conductive pathway through the increase of collision frequency between iodide species was proposed. Furthermore, a quasi-solid-state ionic liquid crystal DSSC was successfully fabricated by employing a low molecular gelator. Addition of the 5.0 g/L gelator to ILC improved light-to-electricity conversion efficiency through the increase of J(SC) due to the enhancement of the conductivity in C(12)MImI/I(2)-gel.

In situ gelling pectin formulations for oral drug delivery at high gastric pH.

The aim of the study was to compare the gelation and drug release characteristics of formulations of pectin with high (31%) and low (9%) degrees of methoxylation over a wide pH range (pH 1.2-5.0). Dilute solutions of pectin (1.5%, w/v) containing complexed calcium ions formed gels in vitro at low pH (pH<2.5) as a consequence of cross-linking of the galacturonic chains by calcium ions released from the complex, but the efficiency of gelation was significantly reduced with increase of pH because of incomplete release of complexed Ca(++). Gelation of formulations of pectin with a degree of esterification of 9% (DE9) was observed over the pH range 2.5-5.0 in the presence of 1.6mM Ca(++), but was incomplete in formulations of pectin with a degree of esterification of 31% (DE31). A sustained release of ambroxol was observed following oral administration of pectin DE9 formulations to gastric-acidity controlled rabbits at pH 5.5-5.7 and visual observation of the stomach contents of these rabbits confirmed in situ gelation of these formulations. There was no evidence of in situ gelation of pectin DE31 formulations under these conditions and a rapid initial drug release was observed. Differences in gelling characteristics in this pH range were attributed to the greater susceptibility of low methoxylated pectin to cross-linking by di- and tri-valent ions present in the gastric juice. It is concluded that formulations of pectin with a low degree of esterification have potential application as in situ gelling vehicles for the sustained delivery of drugs following oral administration under conditions of high gastric pH.

The influence of gastric acidity and taste masking agent on in situ gelling pectin formulations for oral sustained delivery of acetaminophen.

Dilute solutions of pectin containing complexed calcium ions form gels when these ions are released in the acidic environment of the stomach. The aim of this study was to examine the influence of a variation of gastric pH and the addition of a taste masking agent on the gelation of the pectin solutions and on the in vitro and in vivo release of acetaminophen from the gels. Increase of pH above 2.5 and addition of 10% (w/v) D-sorbitol significantly affected the ability of 1.5% (w/v) pectin solutions to form coherent gels in vitro. Gelation of sorbitol-free formulations was observed at pH 1.2 and in vitro release of acetaminophen from the gels followed diffusion-controlled kinetics; in vitro gelation of these formulations, however, was incomplete at pH 3.0 resulting in poor sustained release characteristics. Inclusion of 10% (w/v) D-sorbitol in the formulations inhibited the in vitro gelation of the 1.5% (w/v) pectin sols and poor sustained release properties were noted from these formulations even at pH 1.2. The bioavailability of acetaminophen from gels formed in the stomach of gastric-acidity controlled rabbits following oral administration of the liquid formulations was not, however, significantly affected either by the inclusion of 10% (w/v) D-sorbitol or increase of pH to 3.6. Visual observation showed in situ gelation of 1.5% (w/v) pectin formulations containing D-sorbitol at pH 4.3 suggesting that normal variations of gastric acidity in the fasting state will have no effect on the bioavailability of acetaminophen when delivered using these formulations.

The influence of variation of gastric pH on the gelation and release characteristics of in situ gelling pectin formulations.

The aim of this study was to examine the influence of variation of gastric pH over the range 1-3 on the gelation of liquid formulations of pectin and on the in vitro and in vivo release of paracetamol and ambroxol from the resultant gels. The formulations were dilute solutions of pectin containing complexed calcium ions that form gels when these ions are released in the acidic environment of the stomach. Gels suitable as vehicles for sustained delivery of these drugs were formed in vitro at pH<3 from pectin solutions of concentrations 1.0-2.0% (w/v). Very weak gels were formed at pH 3.0 resulting in poor sustained release characteristics compared with those at pH 1.2; no significant in vitro gelation was observed at pH 3.5. The bioavailabilities of paracetamol and ambroxol from gels formed in the stomach following oral administration of the liquid formulations were investigated using gastric-acidity controlled rabbits. Visual observations showed in situ gelation of 1.5% (w/v) pectin formulations under conditions of both high (pH 1.0-1.6) and low gastric acidity (pH 3.3-3.6). The bioavailabilities of these drugs were not significantly different when released from gels formed at the two pH limits suggesting that normal variations of gastric acidity in the fasting state will have no effect on the bioavailability of these drugs when delivered using this vehicle.

Oral sustained delivery of theophylline and cimetidine from in situ gelling pectin formulations in rabbits.

The aim of this study was to evaluate the potential of an in situ gelling pectin formulation as a vehicle for the oral sustained delivery of theophylline and cimetidine. In vitro studies demonstrated diffusion-controlled release of theophylline from 1, 1.5, and 2% w/v pectin gels. Release of this drug from 1.5% w/v pectin gels formed in situ in rabbit stomach was sustained over a period of 12 hours giving a theophylline bioavailability some seven fold higher than when administered from a commercial syrup. In contrast, interactions between cimetidine and pectin led to weak gelation of the pectin sols that prevented any meaningful determination of in vitro release characteristics. Similarly, in vivo release profiles from pectin formulations containing cimetidine were similar to that from a solution of this drug in buffer, indicative of weak gelation. Examination of the content of the rabbit stomach 5 hours after administration of 1.5% w/v pectin sols containing drug confirmed gel formation, but gels containing cimetidine were noticeably softer than those containing theophylline.

The effect of taste masking agents on in situ gelling pectin formulations for oral sustained delivery of paracetamol and ambroxol.

The aim of this study was to examine the influence of polyhydric alcohols (taste masking agents) on the rheological properties of in situ gelling pectin formulations and on the in vitro and in vivo release of paracetamol and ambroxol from these formulations. Gelation of orally administered pectin solutions containing calcium in complexed form occurred on release of calcium in the acidic environment of the stomach. Inclusion of 10% (w/v) sorbitol in 2% (w/v) pectin sols reduced the viscosity and ensured Newtonian flow properties. Xylitol and mannitol in similar concentrations were less effective in reducing viscosity; sucrose increased viscosity and caused non-Newtonian flow. The in vitro release of paracetamol from 2% (w/v) pectin gels formulated with 10% (w/v) of sorbitol, erythritol, xylitol or mannitol, and of ambroxol from 2% (w/v) pectin gels containing 10% (w/v) sorbitol, followed diffusion-controlled kinetics. Pectin gels (2%, w/v) containing sorbitol (10%, w/v) sustained the release of paracetamol in the rat stomach and bioavailabilities of approximately 90% of those from an orally administered paracetamol syrup were achieved. Sustained release of ambroxol from in situ gelling formulations was achieved with pectin concentrations of 1.5 and 1% (w/v) and a sorbitol concentration of 10% (w/v).

Ionic liquid crystal as a hole transport layer of dye-sensitized solar cells.

Use of a new ionic liquid crystal, 1-dodecyl-3-methylimidazolium iodide, and iodine as an electrolyte of dye-sensitized solar cells leads to a high short circuit photocurrent density and a high light-to-electricity conversion efficiency, due to a self-assembled structure of the imidazolium cations, resulting in high conductivity of the electrolyte.

Role of electrolytes on charge recombination in dye-sensitized TiO(2) solar cell (1): the case of solar cells using the I(-)/I(3)(-) redox couple.

Performance of dye-sensitized solar cells (DSCs) was investigated depending on the compositions of the electrolyte, i.e., the electrolyte with a different cation such as Li(+), tetra-n-butylammonium (TBA(+)), or 1,2-dimethyl-3-propylimidazolium (DMPIm(+)) in various concentrations, with and without 4-tert-butylpyridine (tBP), and with various concentrations of the I(-)/I(3)(-) redox couple. Current-voltage characteristics, electron lifetime, and electron diffusion coefficient were measured to clarify the effects of the constituents in the electrolyte on the charge recombination kinetics in the DSCs. Shorter lifetimes were found for the DSCs employing adsorptive cations of Li(+) and DMPIm(+) than for a less-adsorptive cation of TBA(+). On the other hand, the lifetimes were not influenced by the concentrations of the cations in the solutions. Under light irradiation, open-circuit voltages of DSCs decreased in the order of TBA(+)> DMPIm(+) > Li(+), and also decreased with the increase of [Li(+)]. The decreases of open-circuit voltage (V(oc)) were attributed to the positive shift of the TiO(2) conduction band potential (CBP) by the surface adsorption of DMPIm(+) and Li(+). These results suggest that the difference of the free energies between that of the electrons in the TiO(2) and of I(3)(-) has little influence on the electron lifetimes in the DSCs. The shorter lifetime with the adsorptive cations was interpreted with the thickness of the electrical double layer formed by the cations, and the concentration of I(3)(-) in the layer, i.e., TBA(+) formed thicker double layer resulting in lower concentration of I(3)(-) on the surface of the TiO(2). The addition of 4-tert-butylpyridine (tBP) in the presence of Li(+) or TBA(+) showed no significant influence on the lifetime. The increase of V(oc) by the addition of tBP into the electrolyte containing Li(+) and the I(-)/I(3)(-) redox couple was mainly attributed to the shift of the CBP back to the negative potential by reducing the amount of adsorbed Li cations.

Roles of electrolytes on charge recombination in dye-sensitized TiO(2) solar cells (2): the case of solar cells using cobalt complex redox couples.

Dye-sensitized solar cells (DSC) were prepared from nanoporous TiO(2) electrodes with two different cobalt complex redox couples, propylene-1,2-bis(o-iminobenzylideneaminato)cobalt(II) {Co(II)(abpn)} and tris(4,4'-di-tert-buthyl-2,2'-bipyridine)cobalt(II) diperchlorate {Co(II)(dtb-bpy)(3)(ClO(4))(2)}. The performances of the DSCs were examined with varying the concentrations of the redox couples and Li cations in methoxyacetonitrile. Under 1 sun conditions, short-circuit currents (J(sc)) increased with the increase of the redox couple concentration, and the maximum J(sc) was found at the Li(+) concentration of 100 mM. To rationalize the observed trends of J(sc), electron diffusion coefficients and lifetimes in the DSCs were measured. Electron diffusion coefficients in the DSCs using cobalt complexes were comparable to the previously reported values of nanoporous TiO(2). Electron lifetime was independent of the concentration of the redox couples when the concentration ratio of Co(II)(L) and Co(III)(L) was fixed. With the increase of Li(+) concentration, the electron lifetime increased. These results were interpreted as due to their slow charge-transfer kinetics and the cationic nature of Co complex redox couples, in contrast to the anionic redox couple of I(-)/I(3)(-). The increase of the lifetimes with Li(+) was interpreted with the decrease of the local concentration of Co(III) near the surface of TiO(2). The addition of 4-tert-butylpyridine (tBP) with the presence of Li(+) increased J(sc) significantly. The observed increase of the electron lifetime by tBP could not explain the large increase of J(sc), implying that tBP facilitates the charge transfer from Co(II)(L) to dye cation, with the association of the change of the reorganization energy between Co(II) and Co(III).