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•Modelling in preparation for future deuterium campaign.•The goal is to study tritium burn-up.•Modelling restricted to high energy neutrons.•Model for assessing Scintillating Fibre ...neutron detector diagnostics.•Detailed CAD based geometry based on unstructured mesh.
In this work, a Serpent 2 neutronics model of the Wendelstein 7-X (W7-X) stellarator is prepared, and an response function for the Scintillating-Fibre neutron detector (SciFi) is calculated using the model. The neutronics model includes the simplified geometry for the key components of the stellarator itself as well as the torus hall. The objective of the model is to assess the 14.1 MeV neutron flux from deuteron-triton fusions in W7-X, where the neutrons are modelled only until they have slowed down to 1 MeV energy. The key messages of this article are: demonstration of unstructured mesh geometry usage for stellarators, W7-X in particular; technical documentation of the model and first insights in fast neutron behaviour in W7-X, especially related to the SciFi: the model indicates that the superconducting coils are the strongest scatterers and block neutrons from large parts of the plasma. The back-scattering from e.g. massive steel support structures is found to be small. The SciFi will detect neutrons from an extended plasma volume in contrast to having an effective line-of-sight.
Free-Floating Atmospheric Pressure Ball Plasmas v. Wurden, Caroline J.; Wurden, G. A.
IEEE transactions on plasma science,
2011-Nov., 2011-11-00, 20111101, Volume:
39, Issue:
11
Journal Article
Peer reviewed
Ball plasmas were created in a laboratory, using an electric arc discharge (4-250 A at up to 5 kV) from points of metal onto a water surface. The rising plasmas were studied with still and video ...cameras, photodiodes, power meters, and spectroscopy. The plasma consists of positive salts from the solution and center electrode material, and negative hydroxyl radicals. Various salts (CuSO 4 , CuCl 2 , NaCl, LiCl, and CaCl 2 ) and copper or aluminum center cathode materials were tried. The color is characteristic of the metal from solution. While observing with an Ocean Optics USB 2000 spectrometer, it was confirmed that the material in the cooling (~0.3-eV) plasma, comes from the water and not the surrounding air.
Two applications of microparticles (micron-size particles) for laboratory plasma diagnosis are discussed. The first application is about injecting hypervelocity microparticles (HDI) for hypervelocity ...dust injection for internal magnetic field measurement in high-temperature plasmas. Since the concept of HDI has already been examined in details in our previous works, the primary focus here is to compare different schemes of microparticle acceleration. A new design of HDI based on plasma-dynamic accelerator is described to inject multiple microparticles to velocities around 10 km/s simultaneously. The other application is about using microparticles to measure plasma flow (mPTV) for microparticle tracer velocimetry. Directions of plasma flow at multiple locations can be measured simultaneously using mPTV because ion drag dominates over other forces inside laboratory plasmas of order 10/sup 19/ m/sup -3/ in density and a few electron volts in temperature. In addition to complex interactions between a microparticle with plasma, the magnitude of plasma flow may not be obtained directly from the microparticle velocity because of the time it takes for each microparticle to relax to local plasma velocity. In summary, microparticles are naturally small objects in all three dimensions and can, therefore, become useful diagnostics for laboratory plasmas with minimal perturbation.
Multiple spectroscopy diagnostics have been fielded on the FuZE-Q sheared-flow-stabilized (SFS) Z-pinch to measure plasma impurities, flow velocity, temperature, and density. The spectroscopy ...diagnostics currently cover the wavelengths from extreme ultraviolet (EUV) in the 5-40 nm (30-250 eV) range, ion Doppler spectroscopy (IDS) in the 225-233 nm range, to compact broadband spectroscopy (UV/VIS) in the 220-1050 nm range. Spectral databases and collisional-radiative (CR) modeling have been used to identify impurities and estimate plasma parameters. Many emission lines from deuterium (D), carbon (C), and oxygen (O) have been identified, at this time. Current line-emission spectroscopy is sensitive to relatively low temperatures characteristic of the edge plasma, outside the fusion core. Temperature estimates using O as an EUV spectroscopic tracer have been compared to IDS estimates using C. EUV and IDS spectra find evidence of an ensemble of edge plasma temperatures in device-commissioning shots. Modeling line pairs involving B-like, Be-like, Li-like, and He-like O yielded electron temperatures from 16 to 155 eV. This profile is comparable to ion temperatures observed by IDS from Doppler broadening of Be-like C (34 eV) and He-like C (298 eV). Deposition and debris from within FuZE-Q have been analyzed with scanning electron microscope (SEM) energy dispersive X-ray spectroscopy (EDS) and find evidence of C, O, Si, W, Al, Cu, Fe, and Cr. Synthetic spectra from CR modeling, informed by plasma numerical simulations, can be compared to experimental spectra and thereby benchmark the calculations. Measurements of the edge plasma provide insight into plasma-wall interactions. Impurity identification is vital for radiative power and scientific <inline-formula> <tex-math notation="LaTeX">{Q} </tex-math></inline-formula> calculations.
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