Balmer-α spectrum measurements of the LHD one-third ion source.

Wavelength spectra of Balmer-α light from plasmas in the extraction region of the Large Helical Device-R&D negative ion source, or the LHD one-third ion source have exhibited a blue shift as a negative bias voltage was applied to the plasma grid. The blue shift increased as the negative bias voltage with respect to the local plasma potential was increased. The measured spectra were compared with the velocity distributions of surface reflected hydrogen atoms calculated by atomic collisions in amorphous target code. The arc power and the source H2 pressure also affected the shift and broadening in the observed Balmer-α spectra. The possibility of identifying the negative hydrogen ions produced at the low work function plasma grid surface by high resolution spectroscopy is discussed.

Angular distributions of surface produced H(-) ions for reflection and desorption processes.

A numerical simulation code, Atomic Collision in Amorphous Target, has been run to clarify the effects due to the incident angle of hydrogen flux onto surface collision cascade in the subsurface region of a Cs covered Mo plasma grid. The code has taken into account the threshold energy for negative hydrogen (H(-)) ions to leave the surface. This modification has caused the shift of energy distribution functions of H(-) from that of hydrogen atoms leaving the surface. The results have shown that large incident angle of hydrogen particle tilt the angular distribution of reflection component, while it caused a small effect onto the angular distribution of desorption component. The reflection coefficient has increased, while the desorption yield has decreased for increased angle of incidence measured from the surface normal.

Hydrogen negative ion production in a 14 GHz electron cyclotron resonance compact ion source with a cone-shaped magnetic filter.

The plasma electrode structure of a 14 GHz ECR ion source was modified to enlarge the plasma volume of low electron temperature region. The result shows that the extracted beam current reached about 0.6 mA/cm(2) with about 40 W microwave power. To investigate the correlation between the volume of the low electron temperature region and the H(-) current, a vacuum ultraviolet (VUV) spectrometer had been installed to observe light emission in the VUV wavelength range from the plasma. From the results of the negative ion beam current and that from VUV spectrometry, production rate of vibrationally excited hydrogen molecule seems to be enhanced by increasing the volume of low electron temperature region.

Effects of roughness and temperature on low-energy hydrogen positive and negative ion reflection from silicon and carbon surfaces.

Angle-resolved energy distribution functions of positive and negative hydrogen ions produced from a rough-finished Si surface under 1 keV proton irradiation have been measured. The corresponding distribution from a crystalline surface and a carbon surface are also measured for comparison. Intensities of positive and negative ions from the rough-finished Si are substantially smaller than those from crystalline Si. The angular distributions of these species are broader for rough surface than the crystalline surface. No significant temperature dependence for positive and negative ion intensities is observed for all samples in the temperature range from 300 to 400 K.

Extraction of negative hydrogen ions from a compact 14 GHz microwave ion source.

A pair of permanent magnets has formed enough intensity to realize electron cyclotron resonance condition for a 14 GHz microwave in a 2 cm diameter 9 cm long alumina discharge chamber. A three-electrode extraction system assembled in a magnetic shielding has formed a stable beam of negative hydrogen ions (H(-)) in a direction perpendicular to the magnetic field. The measured H(-) current density was about 1 mA∕cm(2) with only 50 W of discharge power, but the beam intensity had shown saturation against further increase in microwave power. The beam current decreased monotonically against increasing pressure.

Effects of adsorption and roughness upon the collision processes at the convertor surface of a plasma sputter negative ion source.

Atomic collision processes associated with surface production of negative hydrogen ions (H(-)) by particle reflection at molybdenum surface immersed in hydrogen plasma have been investigated. To calculate sputtering yields of Cs, as well as energy spectra and angular distributions of reflected hydrogen atoms from molybdenum surface by H(+) ion and Cs(+) ion bombardments, a Monte Carlo simulation code ACAT (Atomic Collision in Amorphous Target) was run with the corresponding surface conditions. A fractal surface model has been developed and adopted to ACAT for evaluating the effect due to roughness of target material. The results obtained with ACAT have indicated that the retention of hydrogen atoms leads to the reduction in sputtering yields of Cs, and the surface roughness does largely affect the sputtering yields of Cs.

Erosion of accel grids of ion engine due to sputtering.

The erosion rates of extraction electrodes of ion sources due to ion beam irradiation are largely affected by amount of projectiles retained in the electrodes. A Monte Carlo simulation code ACAT has been used to calculate sputtering yields and reflection coefficients by simulating the accumulation effect of projectiles in a target material. The results for Xe projectiles-C target combination have indicated that both sputtering yields and reflection coefficients are largely enhanced by Xe retention, particularly at larger incident angle for the surface normal with low incident energy.

Time-of-flight analyzer system to detect reflected particles from a solid surface following low-energy particle injection.

We have developed a time-of-flight analyzer to measure energy distributions of reflected particles from solid surfaces bombarded by low-energy (1-2 keV) ions. The analyzer yields energy distributions of neutrals which can be compared with the energy distributions of charged particles measured by a magnetic deflection-type momentum analyzer. We have tested the system to measure the angular dependence of energy and intensity for neutrals reflected from a polycrystalline W target. The energies of the reflected neutrals are much smaller than the incident ion energies, suggesting multiple scattering in the target. No angular dependence is observed under the condition that the sum of the incident and reflected angles is constant. The intensity of the reflected neutrals takes the maximum around the mirror angle. We compare these characteristics of neutral particle reflections with those of reflected ions.

[Investigation of papillary insufficiency in dogs by monitoring the manometry of the biliary tract with the saline perfusion method].

In order to establish the animal model of papillary insufficiency, 10% formalin solution (0.5-1.0 ml) was injected into duodenal papillae just after cholecystectomy in ten dogs. The bile duct pressure of the dogs was monitored by the manometer utilizing the saline perfusion system. Persistent dilatation of the bile duct was observed postoperatively. Two weeks after operation, the maximum dilatation of the bile duct was observed. The bile duct pressure of the dogs showed several characteristic changes: 1) the perfused pressure increased rapidly just after saline perfusion and then became stable, 2) the dumping time was shorter than that of the control dogs, 3) the residual pressure was lower than that of the control dogs. A metal sound, 4mm in diameter, was passed through the duodenal papillae of the dogs with ease. After injection of 10% formalin solution, macroscopic findings of the duodenal papillae revealed the diminish of their protrusions. These results demonstrated that the pathophysiology of the duodenal papillae treated with 10% formalin solution in this animal model is quite similar to that of human papillary insufficiency.