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The acceleration characteristics of H− beam have been investigated using a single beam let accelerated up to 100 keV. The H− beam is extracted from a large negative ion source operated with Cs seeding and is accelerated by a single‐stage accelerating system. The currents and the spatial profiles of the H− beams are measured calorimetrically. The beam divergent angles are obtained by means of Gaussian fitting to the measured plots. A minimum divergent angle of 5 mrad is achieved with an H− current densities of 32 mA/cm2 and the beam energy of 94 keV. A ratio of acceleration current to H− current increases suddenly at the region where the H− current begins to saturate due to a space charge limitation. This is considered to be caused by emission of secondary electrons at an extraction electrode by collisions of the divergent H− beams. The dependence of the divergent angle on the acceleration voltage is measured, and an optimum ratio the electric fields for H− extraction and for the acceleration is determined...

High current hydrogen negative ion source development has been intensively carried out for neutral beam injector for Large Helical Device (LHD), in which ion source capable of delivering a negative ion beam of 45 A at a beam energy of 125 keV is required. A multicups ion source of 1/3 scale of the prototype source in NBI for LHD and a large rf ion source has been studied for negative ion production, beam extraction and acceleration. A total H− current of 16 A is obtained at the 1/3 scale source with Cs seeding operation. The H− ion current is proportional to the input arc power. A 13.6 A of H− ion beam is accelerated to 125 keV at the two stage acceleration. A divergent angle of 9 mrad is obtained at multi beam. Preliminary experimental results of r.f. ion source are described.

Fabrication of a 15 MW, 10 sec. negative‐ion‐based neutral beam injection system has been started for Large Helical Device (LHD). The system is composed of two tangential beam lines. Each beam line has two ion sources which are designed to deliver 40 A of negative hydrogen ions at the beam energy of 180 keV. The beam line has two vacuum chambers and a long gas neutralizer of 3.5 m between them. The first chamber is used as a gas expansion chamber of ion sources, and its gas pressure is controlled to keep the optimum line density for neutralization. The second chamber includes a magnetic bending system to deal with residual ions. The design is based on the results of our RD the high density negative hydrogen ion production, high power beam extraction, and low beam divergence. The commissioning of the system will start in 1997, and the operation is scheduled in 1998.

Present status of the hydrogen negative ion source development is reported for an NBI system in the Large Helical Device. An external-filter type negative ion source has produced a 16.2 A of H - ion beam with the energy of 47 keV at the arc efficiency of 0.1 A/kW and at the operational gas pressure of 3.8 mTorr. The H - ion beam of 13.6 A was successfully accelerated to 125 keV with two-stage acceleration. A rod-filter type negative ion source has also produced a 16 A of H - ion beam with the current density of 45 mA/cm 2 . A vacuum-immersed negative ion source has demonstrated stable operation on condition that the ion source is shielded from the beam-induced plasma. For the future long-lifetime operation, an RF-driven negative ion source has been developed, where an induction coil antenna is placed inside a metal-walled magnetic multicusp source.

Electron density measurements of a large-scaled negative ion source were carried out with a surface wave probe. By comparison of the electron densities determined with the surface wave probe and a Langmuir probe, it was confirmed that the surface wave probe is highly available for diagnostic of the electron density in H(-) ion sources. In addition, it was found that the ratio of the electron density to the H(-) ion density dramatically decreases with increase of a bias voltage and the H(-) ions become dominant negative particles at the bias voltage of more than 6 V.

We report on the characteristics of the electronegative plasma in a large-scale hydrogen negative ion (H(-)) source. The measurement has been made with a time-resolved Langmuir probe installed in the beam extraction region. The H(-) density is monitored with a cavity ring-down system to identify the electrons in the negative charges. The electron-saturation current decreases rapidly after starting to seed Cs, and ion-ion plasma is observed in the extraction region. The H(-) density steps down during the beam extraction and the electron density jumps up correspondingly. The time integral of the decreasing H(-) charge density agrees well with the electron charge collected with the probe. The agreement of the charges is interpreted to indicate that the H(-) density decreasing at the beam extraction is compensated by the electrons diffusing from the driver region. In the plasmas with very low electron density, the pre-sheath of the extraction field penetrates deeply inside the plasmas. That is because the shielding length in those plasmas is longer than that in the usual electron-ion plasmas, and furthermore the electrons are suppressed to diffuse to the extraction region due to the strong magnetic field.

Characteristics of multibeamlets are investigated by means of beamlet monitoring technique. The beamlets are extracted from an accelerator with multislot grounded grid and the profiles are observed as infrared images of temperature distributions on a cold isostatic pressed graphite plate exposed by H-beamlets. The optimal horizontal and vertical divergence angles of single beamlet are estimated at 4.1 and 6.1 mrad, respectively.

The beam profiles, port-through, rates and injection powers obtained with an improved accelerator with the multislot grounded grid are described. The accelerator has a combination of a steering grid with racetrack shaped aperture and multislot grounded grid to improve the beam optics. The optimal beam optics is obtained at the voltage ratio of 16.5-16.8, and the profiles are well fit by superposing multibeamlets with the divergent angles of 5.0 and 7.2 mrad along the direction parallel to the long and short axes of the slots of grounded grid. By adopting the racetrack shaped steering grid, the port-through rate increases from 34% to 38%, and the maximum injection power reaches 6 MW/187 keV.

A multiantenna rf ion source is studied. The new antenna system is developed to reduce the rf voltage on the antenna compared to that of the conventional loop antenna, which can reduce high voltage rf breakdown on antennas. The antenna was installed in a 1/6 scale ion source for the neutral beam injector (NBI) (H−) used in large helical devices. The characteristics of the ion density current of the plasma produced by using the segmented antennas were studied. A dense plasma with ion saturation current density of 92 mA/cm2 was generated at 45 kW of rf power at 9 MHz for the two-antenna system. At around 10 kW of rf power the plasma density jumped and became a high density mode. The threshold power for the density jump seems to be shifted by the antenna segments and the rf frequency. The current density of the positive ion beam with a small accelerator voltage is 26 mA/cm2 for 10.3 keV of extraction energy, 45 kW of rf power, and 0.16 Pa of plasma source pressure of hydrogen. This multiantenna rf source cou...

The velocity spectra of the negative-ion-(H−) based neutral beams are studied in high-performance large-area ion sources during injection into large helical device fusion plasmas. We are conducting systematic observations in standard neutral beam injection to correlate beam spectra with source operating conditions. Almost all of the transmitted beam power was at full acceleration energy (∼170keV). The small stripping beam component which was produced in the extraction gap was evaluated to be about 9%–22% by amplitude of the measured spectra for the sources in beam lines 1 and 2. H− production uniformity from the spectrum profile was 86%–90% for three sources. For the longest pulse injection during 74 and 128 s, a full energy component tended to decrease with time, while the accelerator gap stripping tail tended to increase slightly with time, which is attributed to beam-induced outgassing in the accelerator. A higher conductance multislot ground grid accelerator appeared to show little growth in the accel...

A new multiantenna system for large area radio-frequency H− ion source using a filamentless ion source was tested to extract ions from dense plasmas with high rf input power. A 1∕6 scale large helical device ion source was equipped inside a plasma chamber with four linear antenna rods. Positive-ion extraction with a single hole extractor was studied in detail, while a negative one only showed preliminary results. The positive-ion current density of 34mA∕cm2 to the collector plate was achieved with a new multiantenna after optimization of the antenna number and source gas pressure, where the number of the antennae was 2 with ∼36kW of rf input power and with a gas pressure of ∼0.1Pa with H2. If the external magnetic filter optimized for negative-ion production in the multifilament discharge source is taken off, the current density is estimated to reach about 120mA∕cm2. This corresponded closely to the value measured with a Langmuir probe near the center. Two antennae appear to be required to generate unifor...

The injection duration has been extended beyond 100 s with a high-power hydrogen negative-ion source in a negative-ion-based neutral beam injector of the Large Helical Device superconducting fusion machine. The ion source is a cesium-seeded source with a thermally insulated plasma grid (PG), and optimized for a short-pulse operation of 2?3 s. The negative-ion production efficiency is strongly dependent on the PG temperature, and in the long-pulse operation it exceeds an appropriate temperature range of 200?300 °C, at which the optimum cesium coverage is formed on the PG surface. By making the PG temperature rise slower with a reduced arc power, the injection duration was extended to 110 s with an injection power of 110 kW. To extend the injection duration further with a higher injection power, stainless-steel cooling tubes have been mechanically attached to the PG for suppression of the PG temperature rise in the long-pulse operation. As a result, a long-pulse injection with an injection power of 200 kW was extended to 128 s until it was manually stopped due to the plasma collapse. However, the beam duration could be limited to around 3 min because the PG temperature rise was not saturated due to a low thermal conductivity with the thickness of the stainless-steel tube determined so that the short-pulse operation is also possible. On the other hand, the longitudinal beam distribution in a grid area of 25×125 cm^2 is observed to be more uniform than that with the uncooled PG. The temperature distribution of the individual grid parts becomes more uniform with the cooled PG, which should contribute to the improvement of the beam uniformity.

The purpose of the experiment was to analyse a dynamic type of Vernier acuity in the visual prediction of the trajectory of linear apparent motion. The subjects were shown a single moving dot, which moved from the left end to the right end of a CRT. The change in dot position between two successive frames was 0.15 deg. Midway through the trajectory the dot moved behind an amodal occluding square, thus being invisible in this area. The vertical position where the dot re-emerged from behind the occluding square was varied, with 14 conditions for deviations both above and below the ‘correct’ locus of straight movement. A unit step of the deviation was 0.029 deg. There were three SOA conditions (13 ms, 21 ms, and 26 ms). In a 2AFC paradigm, the subjects had to report on which of two presentations the dot reappeared in the ‘correct’ position. We applied Probit analysis to fit a cumulative normal distribution to the result of each SOA condition and each deviation direction. We defined a value giving 75% correct response as a threshold value. Within each SOA condition, there was no difference between the threshold for deviations above or below the correct position, nor did threshold values between three SOA conditions show significant differences (ANOVA). We compare and discuss Vernier-acuity thresholds with and without amodal occlusion of the locus.

T-1982 (cefbuperazone) was given intravenously to 21 children with the following acute bacterial infections; 13 cases of bronchopneumonia, 2 cases of urinary tract infection, 1 case of subcutaneous abscess, 1 case of cervical purulent lymphadenitis and acute tonsillitis, and 4 cases of acute bronchitis. Clinical effectiveness was obtained in 20 cases out of 21 cases and bacteriological effectiveness in 7 cases out of 8 cases. As for the side effects, 1 patient had asymptomatic eosinophilia, but no other laboratory abnormalities were observed. Above results suggest that T-1982 is a useful antibiotic for treating pediatric patients with various kinds of bacterial infections.

A 35-year-old woman tuffering from gastric cancer associated with disseminated carcinomatosis of the bone marrow is reported. Total gastrectomy combined with splenectomy and distal pancreatectomy was performed. The patient was treated with mitomycin C, FT-207, OK-432, and PSK. But serum ALP (alkaline phosphatase) and CEA (carcinoembryonic antigen) values showed gradual elevations followed by deterioration of the patient's general condition. Consequently, chemotherapy program consisting of 5-fluorouracil, Adriamycin (intra-arterially), and cisplatin (intravenously) was initiated. Serum CEA and ALP values were considerably improved, and patient was restored to a better condition. She survived 17 months and died of disseminated intravascular coagulation.

Ampicillin suppository (KS-R1) was given to 16 children with the following acute bacterial infection; 4 cases of acute pharyngitis, 2 cases of acute tonsillitis, 5 cases of acute bronchitis, 4 cases of bronchopneumonia, 1 case of group A beta-streptococcal infection. Out of 16 patients, good clinical responses were obtained in 16 patients, and bacteriological effectiveness was seen in all 3 cases. Side effects with KS-R1 were observed in 4 cases: 3 cases were perianal redness, and 4 cases were soft stool. From the above clinical results, KS-R1 is useful antibiotic suppository for treating the pediatric patients with various kinds of bacterial infections.

Fabrication of a 15 MW, 10 sec. negative-ion-based neutral beam injection system has been started for Large Helical Device (LHD). The system is composed of two beam lines. Each beam line has two ion sources which are designed to deliver 40 A negative hydrogen ions at the beam energy of 180 keV. The beam line has a long gas neutralizer and a magnetic bending system to deal with residual ions. The beam line has also a bending system for accelerated electrons, which we think necessary. Special attention is paid to reduce ferromagnetic materials in the beam line, because helical systems are sensitive to the error magnetic field. The design is based on the results of our R&D on the large negative hydrogen ion source, high density negative hydrogen ion production, high power beam extraction and low beam divergence.

Large-scaled hydrogen negative ion source development is reviewed for a negative ion based neutral beam injector (NBI) in the large helical device (LHD) fusion machine. The target performance of the ion source is characterized by a high current of 30–40 A with a relatively low energy of 120–180 keV. A series of negative ion source development is conducted with a one-dimensionally reduced size of ion sources which still have a large beam area of 25 cm×26 cm or 50 cm with multi apertures. We employed a cesium-seeded volume production source with an external magnetic filter for the source development. Improvement of the arc plasma confinement is effective to produce a high-current negative ion of 16 A with a current density of 31 mA/cm2 at a low operational gas pressure below 0.4 Pa. Suppression of the accelerated electrons is achieved both by strengthening the magnetic field at the extraction grid and by shaping the inside of the extraction grid aperture to shield the secondary electrons against the acceler...