Investigation of boron distribution and material migration on the W7-X divertor by picosecond LIBS

One set of horizontal target elements of the Test Divertor Units (TDU), retrieved from the Wendelstein 7-X (W7-X) vessel after the end of second divertor Operation Phase (OP1.2B) in Hydrogen (H), were investigated by picosecond Laser-Induced Breakdown Spectroscopy (ps-LIBS). The Boron (B) distribution, H pattern and the material erosion/deposition pattern on these target elements were analyzed with high depth resolution and mapped in the poloidal direction of W7-X. From the spectroscopic analysis, B, H, Carbon (C) and Molybdenum (Mo) were clearly identified. A non-uniformly distributed B pattern on these divertor target elements was determined by the combination of B layer deposition during the three boronizations and W7-X plasma operation with multiple erosion and deposition steps of B. Like the TDU, the analyzed target elements are made of fine grain graphite, but have two marker layers which allow us to determine the material migration via the ps-LIBS technique. Two net erosion zones including one main erosion zone with a peak erosion depth of 6.5 μm and one weak erosion with a peak erosion of 1.3 μm were determined. Between two net erosion zones, a net deposition zone with width of 135 mm and a thickness up to 3.5 μm at the peak deposition location was determined by the ps-LIBS technique. The B distributions are correlated with the erosion/deposition pattern and the operational time in standard magnetic configuration of W7-X in the phases after the boronizations. The thickness of the containing B layer on these target elements also correlates with the erosion/deposition depth, in which the thickness of the containing B layer varies spatially in poloidal direction between 0.1 μm and 6 μm. Complementary, Focused Ion Beam combined with Scanning Electron Microscopy (FIB-SEM) was employed also to verify and investigate the deposition layer thicknesses at typical net erosion and net deposition zones as well as to identify the three boronizations in depth.

Sustainable and Stable Clay Sand Liners over Time

The washout of fine materials from liners consisting of clay–sand mixtures is expected to influence the hydraulic conductivity. Clay sand liners must be assessed for efficiency when initially subjected to flood or standing water as the wetting under a hydraulic gradient can cause fine material to move and migrate away from the mixture. During wetting and drying complex expansion and shrinkage, changes take place. These changes affect the hydraulic conductivity and are likely to go out of the design range set out for the facility. The research covers the behavior of two clay sand liners tested over an extended time. The hydraulic conductivity measured under a specific hydraulic gradient was measured continuously following the establishment of the test set-up. Self-recording sensors were used to measure the temperature during the tests. The results indicated that the hydraulic conductivity reduces after an initial period of increase and fluctuation caused by the loss of mass because of fine material migration and swelling initiated due to the high content of smectite minerals. The testing and monitoring continued for more than 400 days. The permanent reduction in the hydraulic conductivity occurs after the initial period of repeated rise and fall. The extent of the initial period for the two tested mixtures is subject to the fine content mass and the clay mineralogy. The continuous reduction in the hydraulic conductivity after the initial period is due to the rearrangement of particles and compression in the sand–clay mixture.

The spatiotemporal migration process of Cd content and the theory developed

According to the survey data of Jiaozhou Bay water body from 1984 to 1988, this paper analyzed and explored the data of Cd content each year, and studied the sources, water quality, distribution and migration conditions of Cd content in the waters of Jiaozhou Bay from the perspectives of volume, horizontal distribution, vertical distribution, seasonal distribution, regional distribution, structural distribution and tendency distribution. On the time scale, there are five migration processes of Cd content in the waters of Jiaozhou Bay. The author proposed five material migration theories to present the dynamic migration process of material in the water body. These rules, processes and theories not only provide solid theoretical bases for the migration of Cd content in the waters, but also provide enlightenment for the study of the migration of other substances in water bodies.

Complications of Endovascular Treatment of Intracranial Dural Arteriovenous Fistulas

Aims: To report the endovascular treatment and complications of intracranial and spinal dural arteriovenous (AV) fistulas. Methods: A retrospective analysis of 863 cases with dural AV fistulas was completed in the nationwide registry study of the Japanese Society of Neuroendovascular Therapy. Results: Treatments included transarterial/transvenous embolization (TAE/TVE), open surgery, stereotactic radiation, and their combinations. Modified Rankin Scale 0 (mRS-0) of the patients before and after treatment were 21% and 68%, and mRS 0-1were 69% and 86%, respectively. Mortality rate after treatment was 0.6%. Major complications of TAE and TVE were cranial nerve palsy and cerebral infarction. Conclusions: Major complications resulted from occlusion of vasa nervosum and material migration via dangerous intracranial and extracranial arterial anastomosis.

Effect of sintered electrode on microhardness and microstructure in electro discharge deposition of magnesium alloy

In this study, an endeavour have been made to depositing the electrode materials over the surface of the magnesium alloy using electrical discharge machining (EDM) with WC-Cu powder compacted sintered electrode. Various process parameters such as compaction load, discharge current and pulse on time are selected to carry out the experiment in order to attain the maximum material migration rate (MMR) or deposition rate and microhardness (MH). It was concluded that the MMR and MH increased with increase in discharge current and pulse on time at low compacted electrode but it is decreased at lower discharge current and pulse on time. Highest MMR and MH were attained successfully at partial sintered low compaction load electrode. Microstructure evaluation has been carried out on deposited surface using scanning electron microscopy (SEM) and presence of electrode element in the deposited surface was confirmed by energy dispersive spectroscopy (EDS). Defects mechanism such as globules and craters are formed during EDC with high current and pulse on time respectively, which diminishes the surface roughness. It was observed that the compaction load is the influence parameter on the MMR and MH.