[en] Initial results from a novel device to detect dust particles settling on remote surfaces are presented. Dust particle inventories are a concern in next-step fusion devices. The increase in duty cycle will lead to a scale-up in the amount of particles generated by plasma material interactions. These particles will be chemically and radiologically hazardous and it will be important to establish that the in-vessel particle inventory is within regulatory limits. The detection device consists of two interlocking combs of closely spaced conductive traces on a Teflon circuit board. When a DC bias is applied impinging dust creates a transient short circuit between the traces. The increase in bias current generates a signal pulse that is counted by standard nuclear counting electronics. We present data on the response of the device in air and vacuum to carbon particles

[en] The scale-up of deposition in next-step devices such as ITER will pose new diagnostic challenges. Codeposition of hydrogen with carbon needs to be characterized and understood in the initial hydrogen phase in order to mitigate tritium retention and qualify carbon plasma facing components for DT operations. Plasma facing diagnostic mirrors will experience deposition that is expected to rapidly degrade their reflectivity, posing a new challenge to diagnostic design. Some eroded particles will collect as dust on interior surfaces and the quantity of dust will be strictly regulated for safety reasons - however diagnostics of in-vessel dust are lacking. We report results from two diagnostics that relate to these issues. Measurements of deposition on NSTX with 4 Hz time resolution have been made using a quartz microbalance in a configuration that mimics that of a typical diagnostic mirror. Often deposition was observed immediately following the discharge suggesting that diagnostic shutters should be closed as soon as possible after the time period of interest. Material loss was observed following a few discharges. A novel diagnostic to detect surface particles on remote surfaces was commissioned on NSTX

No abstract available

[en] For experiments at VICKSI 1981 as in the preceding year about 600 foil targets were fabricated. A third of these targets consisted of isotopic pure material of fourty different isotopes. About 100 of these isotope targets were rolled. (HSI)

[en] Short communication

[en] Recent research on the high-field, high-density diverted Alcator C-MOD tokamak has focused on the plasma physics and plasma engineering required for ITER and for attractive fusion reactors. Experimental campaigns over the past two years have focused on understanding the physical mechanisms that affect the plasma performance realized with all-molybdenum walls versus walls with low-Z coatings. RF sheath rectification along flux tubes that intersect the RF antenna is found to be a major cause of localized boron erosion and impurity generation. Initial lower-hybrid current drive (LHCD) experiments (PLH < 900 kW) have demonstrated fully noninductive current drive at I_p ∼ 1.0 MA with good efficiency, I_drive = 0.4P_LH/n_eoR (MA,MW, 10²⁰ m^-3,m). Disruption mitigation via massive gas-jet impurity puffing has proven successful at high plasma pressure, indicating this technique has promise for implementation on ITER. Pressure gradients in the near SOL of Ohmic L-mode plasmas are observed to scale consistently as I_p², and show a significant dependence on X-point topology. Modeling of H-mode edge fueling indicates high self-screening to neutrals in the pedestal and scrape-off layer (SOL), and reproduces experimental density pedestal response to changes in neutral source. Detailed measurements of the temperature and density profiles in the near sol and fast framing movies of the turbulent structures provide improved understanding of the mechanisms that control transport in the edge region.

[en] A fast ion detector based on secondary electron emission from an aluminium surface is described. The secondary electrons are accelerated by 1.2 kV and detected by two microchannel plates in cascade configuration. Applying channel plates to the secondary electrons leads to the same detector efficiency as with the channeltron but at a much higher counting rate. The efficiency of the detector for 150 keV protons was measured as a counting rate of 0.8 at 1 MHz. (author)

[en] Short communication

[en] Al-Shuaiba Lagoon area locates along the eastern Red Sea coast, south of Jeddah city, Saudi Arabia. Its soil profile consists mainly of coarse-grained saline sabkha soil. Based on the vertical variations of grain size, the studied Al-Shuaiba Lagoon soil profile was subdivide into three zones A: saline sandy gravels, B: calcareous sandy silts and C: well-graded sands. According to the SPT-N₆₀ values, these soil zones were classified into stiff, medium stiff and very stiff soil-type. The soil zone B has C_C values vary from 0.234 to 0.279 thus it classifies into loose and very high compressible soil. Consequently, based on the exchangeable sodium percentages vs. cation exchange capacity (CEC) classification chart, the soil zone B was classified into medium dispersive potential soil-type. The studied soil samples contain a relatively higher TDS values and high concentration of calcium carbonates, sulfates, and chlorides. Thus, these salts can play an essential harmful effectiveness on the durability of concrete when reacted with cement alkalis.

[en] Short communication