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Various probing beams have been developed and used for plasma diagnostics in thermonuclear fusion research for magnetic confinement The required beam current, beam size, energy, beam characteristics such as divergence, energy spread, and emittance, etc., as well as ion species are different depending on the purpose of diagnostics, target plasma size and parameters. Hydrogen beams are used for charge-exchange recombination spectroscopy (CHERS) and motional stark effect (MSE) spectroscopy. Suitable beam energy for CHERS ranges in the area of 50 keV/amu, and a small beam divergence is required for MSE measurements. Heating beams are often used as diagnostic beams by sharing. Neutral lithium probing beams have been used as effective tools for measurement of density and fluctuations. A heavy ion beam probe (HIBP), made from alkali metal ions, is injected directly without neutralization to measure plasma potential and density, as well as their fluctuations. Recent progress in magnetic fusion experiments has resulted in advancement of the development of negative ion sources, such as He¯ and Li¯ sources for alpha-particle measurement, because of their advantages with regard to efficient neutralization in the high-energy region, and an Au¯ source for HIBP with the application of tandem acceleration. [ABSTRACT FROM AUTHOR]

The phase space distribution of a strongly focused He+ ion beam source equipped with concave multiaperture electrodes was measured using a pepper-pot plate and a Kapton foil. The substructure of 301 merging He beamlets was clearly observed on a footprint of pepper-pot hole at the beam waist, where the beam density was 500 mA/cm2. The position and the width of each beamlet substructure show the effect of interference of beamlets with surrounding one. [ABSTRACT FROM AUTHOR]

An apparatus capable of measuring the angle-resolved energy distribution function of ions produced by backscattering at metal surfaces is designed and tested. To exclude noise due to other impurity ions and electrons from the signal of target ions, a water-cooled magnetic deflection-type momentum analyzer is installed on a rotating table in a vacuum chamber. In addition to the beam forming and beam diagnostics components, work function monitoring equipment and an ion source for surface cleaning are installed. Preliminary tests of the apparatus was conducted to measure He[sup +] emission from neutral He beam injection onto a Mo surface. With an improvement of the signal-to-noise ratio, the apparatus can be used to measure the angle-resolved energy distribution function of He[sup -] produced at a metal surface by He beam injection. [ABSTRACT FROM AUTHOR]

Examines pepper-pot method and two slit-and-collector type techniques for their applicability to measure the emittance of low energy ion beams. Exposure of Kapton foil; Negative ion beam measurement; Comparison of emittance results.

Active control of beam trajectories using four sets of sweep plates is proposed for a heavy ion beam probe (HIBP) system on helical plasma, such as torsatron, stellarator, etc., in order to solve problems arising from the complicated beam trajectories in its nonaxisymmetrical magnetic field. By this method, a series of the probing beam trajectories giving a whole potential distribution can be managed to pass at a particular point (detector aperture) with the same angle. An equation is introduced as a guiding principle to simplify the optimization process of geometrical configuration of the HIBP system, which will be adjusted for different magnetic configurations by only changing the sweep plate voltages. [ABSTRACT FROM AUTHOR]

The characteristics of light output by ion beam irradiations under high ion fluxes have been measured for three kinds of scintillators: ZnS:Ag deposited on the glass plate, Y3Al5O12:Ce powder stiffened with a binder, and Y3Al5O12:Ce ceramics sintered at high temperature. The ion beam flux in the range from 1012 to 1013 ions/(cm2 s) is irradiated to simulate the burning plasma experiments. The decrease of light output has been observed by long time ion irradiation. The deterioration of ZnS:Ag deposited scintillator is most serious. The deterioration has been improved for the scintillators of Y3Al5O12:Ce with a binder and that sintered. Their applications to ITER lost alpha diagnostics are discussed. [ABSTRACT FROM AUTHOR]

Attempts to measure spatial distributions of the current density of the ion beams extracted from an electron-stimulated-desorption-type powdery sample ion source. Localized ion emission at the powder surface; Deflection of the beam in the horizontal direction.

Describes a method of producing electron cyclotron resonance plasma for neutralizing negative ion beam. Capability of the method of generating dense plasmas; Obtainment of a high-density plasma with a low frequency microwave; Use of the electron cyclotron wave in producing the plasma.

Positive and negative hydrogen ion reflections from surfaces by injecting singly charged hydrogen ion beams show a clear difference between atomic and molecular ion injections at low energy and grazing incidence. The intensity ratio of reflected negative to positive ions H−/H+ increased as the incident beam energy per nucleon decreased only when molecular ion beams are injected. It implies that negative ions are more produced upon beam-surface interaction when molecules are injected. A possible reason was discussed in terms of difference in the negative ion production processes between atomic and molecular ions. [ABSTRACT FROM AUTHOR]

In this study, a hydrogen ionic plasma with relatively low residual fractional electron concentration (ne/n+ ∼ 10−2) is generated using an aluminum plasma grid for the production of negative hydrogen ions and a control grid for negative ion extraction and electron removal. The ionic plasma is composed of negative and positive ions, containing molecular ions. Negative ions are in part produced using positive ions with several electron volts. A positive ion beam with 50 eV or more contributes to increase the density of the ionic plasma. The positive ion beam energy and the control grid bias voltage are tuned in such a way that a high-density ionic plasma is maintained. [ABSTRACT FROM AUTHOR]

Using an electrostatic double probe, profiles of the ion beam current density, electron density, and electron temperature were measured in the background plasma that appears by injecting a hydrogen ion beam into low-pressure hydrogen gas in a propagation chamber. The hydrogen ion beam is extracted using concave-shaped electrodes at extremely low energies (Eib = 60–120 eV). Focusing of the beam occurs when Eib exceeds a certain threshold. One probe electrode P3 is far from the beam source and is set in the shadow of another electrode in the beam trajectory. The ion saturation current in P3 is then estimated without considering the beam contribution. The measured electron densities are much larger than those of the ion beam density, the electron temperatures are very low (<1 eV), and the ion beam current densities exhibit fairly good agreement with those measured by Faraday cups. The profiles of the space potential are also estimated by measuring the potential of P3 with respect to ground with a voltage divider having an extremely high resistance. The space potentials obtained are quite low at <10 eV with focusing and ∼23 eV without focusing. The data with and without focusing are compared and conditions for focusing are examined. Focusing achieved through additional electron beam injection in the ground electrode is also examined. The results obtained indicate that a large electron source is required to balance the ion charges. Secondary electron emissions and/or small electron beam injection are effective sources. [ABSTRACT FROM AUTHOR]

Abstract: We measured the characteristics of the reflected particles from a carbon nanowall (CNW) deposited on a W surface following the injection of 1–2keV H+ and O+ ions. The reflected ion energies and intensities indicated a contribution from multiple scattering in the target. The reflection angular dependence of the reflected ion intensities reached the maximum around the mirror angle and showed a sharp distribution, which may be attributable to the effect due to the aligned structure of the CNW. The energies and intensities of the reflected ions decreased with the time of ion bombardment. The intensities and energies of the reflected ions were, however, recovered to some degree by baking the sample, indicating the surface modification due to retention of the injected particles during the injection. We used the Monte Carlo simulation code ACAT (Atomic Collision in Amorphous Target) to study these processes theoretically and the calculated results supported the experimental results. [Copyright &y& Elsevier]

The most critical demand for high-brightness ion beams emerged from the realm of industrial applications of focused ion beams and it was met by using liquid metal ion source technology. Although recognized as a successful technology, liquid metal ion sources have major limitations in view of beam species. Noncontaminating ion beam species with beam brightness comparable to liquid metal ion source, i.e., ∼ 106 A cm¯² sr¯¹ and energy spread of ∼ 1 eV will be ideal for many cutting-edge applications including ion beam milling, mask repair, and imaging studies. This paper attempts to bring out the essential points in the development of high-resolution probe forming beams. With this specific objective in view, this study is based on an analysis of point sources and then a variety of other sources, under the general classification of "broad" source (primarily plasma sources), are discussed. Several sources in this category including a Penning-type source, a multicusp source, and new-generation high-charged state sources seem to have merits for circumventing the limitations of liquid metal ion sources, although further re- search is needed to improve the beam brightness and advance the state-of-the art. [ABSTRACT FROM AUTHOR]

Abstract: We have developed an experimental system to study systematically the interaction of low energy beams with materials. The angular distributions and energy spectra of positive and negative ions reflected from a polycrystalline Mo surface bombarded by a beam of low energy (1–3keV) ions and neutrals of H, H2, H3, He, and O have been measured with this system. The experimental results show that the charge state of outgoing particles yields a pronounced difference in the reflection coefficient and some weaker effect upon the energy distribution. The reflected beams usually showed maximum intensities at around the angle of mirror reflection of the incident beams. A carbon coated Mo sample prepared in a separate plasma chamber was also tested. [Copyright &y& Elsevier]

The total momenta of the particles emitted by a target intensely sputtered with heavy noble-gas ions with an energy of E[sub 0] ≈ 0.5 keV are measured. For liquid Ga targets and Ga targets at the premelting temperature, the measured momenta are close to the expected values for the sputtered metal atoms and reflected ions, whereas for Cu and Zr targets, the measured momenta are significantly higher. It is assumed that these excessive momenta are related to the sputtering of the noble gas atoms implanted into the target. The average energy of these atoms is estimated as 〈E〉 ≈ 20 eV. When gallium is irradiated, the implanted atoms diffuse predominantly to the surface and then are desorbed. [ABSTRACT FROM AUTHOR]

Human cancer cells are irradiated by laser-driven quasimonoenergetic protons. Laser pulse intensities at the 5×1019 W/cm2 level provide the source and acceleration field for protons that are subsequently transported by four energy-selective dipole magnets. The transport line delivers 2.25 MeV protons with an energy spread of 0.66 MeV and a bunch duration of 20 ns. The survival fraction of in vitro cells from a human salivary gland tumor is measured with a colony formation assay following proton irradiation at dose levels of up to 8 Gy, for which the single bunch dose rate is 1×107 Gy/s and the effective dose rate is 0.2 Gy/s for 1 Hz repetition of irradiation. Relative biological effectiveness at the 10% survival fraction is measured to be 1.20±0.11 using protons with a linear energy transfer of 17.1 keV/μm. [ABSTRACT FROM AUTHOR]

Abstract: Polycrystalline ceramics of Ce-doped Y3Al5O12 (Ce: YAG) is characterized as a candidate scintillator for a lost alpha particle measurement on a thermo-nuclear fusion experiments such as ITER. The luminescence intensity for polycrystalline Ce: YAG ceramics is investigated under MeV energy ion irradiation with the ion flux up to ∼6.7×1016 m−2 s−1 and with the ion fluence of ∼1.0×1019 m−2. The luminescence has a good linearity up to ion flux mentioned above. In view of the fluence, the luminescence degradation is observed, but it is found to be a tolerable level. In neutron and gamma ray irradiation experiments at a fission reactor, the defect such as blobs is appeared in irradiated samples. It is found that the thermal annealing is effective for the recovery of the luminescence as well as the contraction of the defect. [Copyright &y& Elsevier]

Abstract: Full orbit-following calculations for the final orbit of lost alpha particles in an ITER equilibrium are performed using a Lorentz orbit code LORBIT [M. Isobe, et al. Rev. Sci. Instrum. 70 (1999) 827] to obtain parameter dependence of the footprint of alpha particle bombardment on the first wall. Determination of the poloidal location for the footprint is dominated by the pitch angle at the starting point. Toroidal distribution of the footprint location is inhomogeneous even for equipartitioned starting points because of the shadow of the magnetic field line on the first wall surface. Due to a hopping motion of an alpha particle on the surface of the first wall, a lined footprint is generated. Energy deposition is found to be dispersed along the line. [Copyright &y& Elsevier]