The Optical Penning (or Species-Selective Penning) Gauge technique is used for the measurement of the H2/D2/T2 fuel isotopic composition and He/D2 concentration in the neutralized particle exhaust of ...fusion devices. An Optical Penning detection system has already been used in JET during its first deuterium-tritium campaigns (DTE1) and has been chosen by ITER. Recent improvements to the sub-divertor diagnostic suite as well as the optical instrumentation, in preparation for the next DT campaign, have improved the optical throughput of the measurement and enabled 3He/D2 detection down to 0.1 %. For the first time, the 3He/4He isotopic ratio can be measured simultaneously with the H/D/T ratio. This technique is of particular interest for ion cyclotron resonance frequency (ICRF) heating scenarios.
Self-ion irradiation of pure tungsten with 2 MeV W ions provides a way of simulating microstructures generated by neutron irradiation in tungsten components of a fusion reactor. Transmission electron ...microscopy (TEM) has been used to characterize defects formed in tungsten samples by ion irradiation. It was found that tungsten irradiated to 0.85 dpa at relatively low temperatures develops a characteristic microstructure dominated by dislocation loops and black dots. The density and size distribution of these defects were estimated. Some of the samples exposed to self-ion irradiation were then implanted with deuterium. Thermal Desorption Spectrometry (TDS) analysis was performed to estimate the deuterium inventory as a function of irradiation damage and deuterium release as a function of temperature. Increase of inventory with increasing irradiation dose followed by slight decrease above 0.1 dpa was found. Application of Positron Annihilation Spectroscopy (PAS) to self-irradiated but not deuterium implanted samples enabled an assessment of the density of irradiation defects as a function of exposure to high-energy ions. The PAS results show that the density of defects saturates at doses in the interval from 0.085 to 0.425 displacements per atom (dpa). These results are discussed in the context of recent theoretical simulations exhibiting the saturation of defect microstructure in the high irradiation exposure limit. The saturation of damage found in PAS agrees with the simulation data described in the paper.
Pure Tungsten (W) will be used as plasma facing component in fusion devices due to its high melting point, good thermal conductivity and low sputtering yield. However, its structural application as ...plasma facing component (PFC) is still restricted by its low fracture toughness associated with the high ductile to brittle transition temperature (DBTT).
In the present study tungsten‑titanium (W-Ti) samples were produced by Ti implantation at room temperature and 500 °C with a constant fluence of 2 × 1021 at/m2 and an energy of 100 keV. In order to understand the fundamental mechanisms which govern the behavior of defect dynamics in tungsten under reactor conditions, W-Ti materials were implanted at room temperature with 10 keV of He+ with a constant fluence of 5 × 1021 at/m2 and 5 keV of D+ with fluences in the range of 0.1 × 1021–5 × 1021 at/m2. Surface structure and morphology changes were investigated by scanning electron microscopy and X-ray diffraction. Rutherford backscattering spectrometry, nuclear reaction analysis and thermal desorption spectroscopy methods were used to provide information about the distribution of Ti, He and D on W.
No changes in the microstructure were observed after Ti implantation in the W plates. NRA analysis showed that D retention in the W-Ti samples is higher after sequential He and D implantation when compared with single D implantation. The diffractogram of W-Ti samples implanted with He evidence a broadening of the W peaks. This effect is believed to be associated with the high volume fraction of the bubbles that may cause internal stress fields inducing extended defects like dislocations which distort the crystal lattice.
•D retention in the W-Ti samples is higher after sequential He and D implantation when compared with single D.•D retention decreasing by about 40–50% for Ti implanted at 500 °C•TDS show the presence of two retention mechanisms: dislocations or grain boundaries and vacancy's.
•ITER radiation hardness assurance policy was recently revised calling for stricter neutron exposure limits for the electronics in systems critical to plasma operations.•ITER DRGA system requires QMS ...sensors to be placed near plasma in high radiation environment in port cell.•Adding a novel, si electronics-free, RF-matching circuit on the port cell side removes 15 m earlier cable-length limit allowing QMS electronics to be placed in neutron-free environment.•QMS with the extended 80 m cable solution was shown in the laboratory to even better resolve fusion-relevant mass species than present commercial equivalent used on JET.•This improved performance with extended 80 m cable has been demonstrated on JET in pre-DTE2 plasma operations.
Strict limits recently imposed on neutron exposure to electronics for critical diagnostic systems on ITER, the fusion reactor demonstration facility under construction in the south of France, has led to the development of a quadrupole mass spectrometer with an exceptionally long cable. An 80 m cable exceeds the last state-of-the art limit of 15 m, imposed by the normally required proximity of the RF supply to the analyzer, and will allow locating the electronics in a neutron safe environment. This breakthrough, a joint development of ORNL with Hiden Analytical Ltd., was enabled by the use of an intermediate, RF-matching unit, free of silicon-based electronics, and using only vacuum tubes and an air-core transformer, rendering it resilient both to ionizing radiation and to fringing magnetic fields. After successful testing of the prototype unit, both at ORNL and Hiden's laboratories, the unit was installed on the JET tokamak, as part of a multi-sensor, divertor effluent gas analysis system, similar to one also under design for ITER. As such, the prototype will be tested both before and during the next nuclear (D-T) operation of JET, planned for mid-2021. In this paper, the prototype development, laboratory testing and first results from non-nuclear plasma pulse testing on JET are presented. The latter include not only successful detection of fusion fuel cycle and impurity species, but also improved resolution and stability over the state-of-the-art, 15m-cable units on the same analysis station.
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