We present a method to both precisely and continuously control the average diameter of single-walled carbon nanotubes in a forest ranging from 1.3 to 3.0 nm with ~1 Å resolution. The diameter control of the forest was achieved through tuning of the catalyst state (size, density, and composition) using arc plasma deposition of nanoparticles. This 1.7 nm control range and 1 Å precision exceed the highest reports to date.

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We report the fundamental dependence of thermal diffusivity and electrical conductance on the diameter and defect level for vertically aligned single-walled carbon nanotube (SWCNT) forests. By synthesizing a series of SWCNT forests with continuous control of the diameter and defect level over a wide range while holding all other structures fixed, we found an inverse and mutually exclusive relationship between the thermal diffusivity and the electrical conductance. This relationship was explained by the differences in the fundamental mechanisms governing each property and the optimum required structures. We concluded that high thermal diffusivity and electrical conductance would be extremely difficult to simultaneously achieve by a single SWCNT forest structure within current chemical vapor deposition synthetic technology, and the "ideal" SWCNT forest structure would differ depending on application.

We report an inverse relationship between the carbon nanotube (CNT) growth rate and the catalyst lifetime by investigating the dependence of growth kinetics for ∼330 CNT forests on the carbon feedstock, carbon concentration, and growth temperature. We found that the increased growth temperature led to increased CNT growth rate and shortened catalyst lifetime for all carbon feedstocks, following an inverse relationship of a fairly constant maximum height. For the increased carbon concentration, the carbon feedstocks fell into two groups where ethylene/butane showed an increased/decreased growth rate and a decreased/increased lifetime indicating different rate-limiting growth processes. In addition, this inverse relationship held true for different types of CNTs synthesized by various chemical vapor deposition techniques and continuously spanned a 1000-times range in both the growth rate and catalyst lifetime, indicating the generality and fundamental nature of this behavior originating from the growth mechanism of CNTs itself. These results suggest that it would be fundamentally difficult to achieve a fast growth with a long lifetime.

We report a new direction for highly efficient carbon nanotube (CNT) synthesis where, in place of conventional highly reactive carbon feedstocks at low concentrations, highly stable carbon feedstocks at high concentrations were shown to produce superior yields. We found that a saturated hydrocarbon that is considered to possess a low reactivity, delivered at high concentrations, could achieve an extremely high growth yield (2.5 times that when using ethylene). This result stems from the unique behavior where the CNT yield linearly increased with carbon concentration, in contrast to more reactive carbon feedstocks, where the yield peaks. We propose that the mechanisms for the growth kinetics for high- and low-reactivity carbon feedstocks are fundamentally different, where the latter benefits from a longer catalyst lifetime because of a relatively low production rate of carbon impurities.

Ripple enhanced banana drift loss of fast ions is studied on the basis of heat load measurements at the first wall near the outer equatorial plane in JT-6OU. Hot spots in the ion cyclotron range of frequency (ICRF) and neutral beam injection (NBI) heating are observed at the outboard wall by using an infrared camera. In ICRF heating, the total heat load to the wall is around 5% of the injected ICRF power when the plasma-wall clearance gap is less than O.lm. The heat flux on the wall increases with the ICRF power and decreases strongly with the plasma density, which is consistent with Fokker-Planck calculations. In NBI heating, hot spots are observed at almost the same positions, and the heat flux and position agree with the banana drift loss as predicted by an orbit following Monte Carlo code.

We report the mutually exclusive relationship between carbon nanotube (CNT) yield and crystallinity. Growth conditions were optimized for CNT growth yield and crystallinity through sequential tuning of three input variables: growth enhancer level, growth temperature, and carbon feedstock level. This optimization revealed that, regardless of the variety of carbon feedstock and growth enhancer, the optimum conditions for yield and crystallinity differed significantly with yield/crystallinity, preferring lower/higher growth temperatures and higher/lower carbon feedstock levels. This mutual exclusivity stemmed from the inherent limiting mechanisms for each property.

The absolute efficiencies of a microchannel-plate detector for He+ and He0 were measured in the energy range of 1 to 10 keV. There was no difference between He+ and He0 incidences regarding efficiency, and the efficiency was constant in the above energy range. This value indicates that almost all the particles hitting the entrance wall of the MCP pores were detected.