The paper provides data on the peculiarity of change in the structure, structural phase changes and destructions in beryllium resulting from interaction with a near-wall plasma of fusion facilities. ...Beryllium resistance under conditions of ITER operation was evaluated, which considers factors leading to possible partial melting and erosion of panels of the ITER first wall. It presents the modelling of a heat s distribution in element (”finger”) of the first wall at ”normal” and ”increased” heat flux of the ITER operation.
Negative ion sources for fusion are high densities plasma sources in large discharge volumes. There are many challenges in the modeling of these sources, due to numerical constraints associated with ...the high plasma density, to the coupling between plasma and neutral transport and chemistry, the presence of a magnetic filter, and the extraction of negative ions. In this paper we present recent results concerning these different aspects. Emphasis is put on the modeling approach and on the methods and approximations. The models are not fully predictive and not complete as would be engineering codes but they are used to identify the basic principles and to better understand the physics of the negative ion sources.
•Through years of research, it is found the main factor affecting the rate and the sensitivity of HHLT facility is the hydrogen released from the vacuum-facing materials at high temperature.•By ...adopting a series of measures, the background leakage rate was successfully reduced by one and a half order of magnitude to 1.17×10−10 Pa•m3/s at 253℃, and the system sensitivity was improved by more than one order of magnitude to reach the order of 10−12Pa·m3/s, even down to 9.85×10−13Pa·m3/s at the temperature..•The research results greatly reduce the difficulty of HHLT, greatly improve its applicability, and can be applied to fusion reactors to improve the overall sealing performance of vacuum vessel and reduce the leakage risk during reactor operation.
Hot Helium Leak Test (HHLT) can realize more reliable leak tightness assessment than the conventional cold helium leak testing for components that run at elevated temperatures. To ensure successful operation of the International Thermonuclear Experimental Reactor (ITER), the in-vessel components are required to ensure high vacuum sealing performance by HHLT. The biggest challenge for the HHLT is that the background leak rate and sensitivity of the test system can hardly meet the requirements of high accuracy at high temperature. Through years of research, it is found the main factor affecting the rate and the sensitivity of HHLT facility is the hydrogen released from the vacuum-facing materials at high temperature. By adopting a series of measures, the background leakage rate was successfully reduced by one and a half order of magnitude to 1.17×10−10 Pa·m3/s at 253℃, and the system sensitivity was improved by more than one order of magnitude to reach the order of 10−12 Pa·m3/s, even down to 9.85×10−13 Pa·m3/s at the temperature.
The magnetic field immunity test is a qualification procedure for all types of electrical and electronic equipment located in ITER Tokamak areas where the static magnetic induction is higher than 5 ...mT. To perform the magnetic field immunity tests, a large-scale high-intensity magnetic field coil system required by ITER organization was developed and tested. The designed test coil system is capable of generating a homogeneous magnetic field with a maximum magnetic flux density of 275 mT in a cubic test zone with a side-length of 1 m. Since the scale and intensity of the test field are high, it is important to ensure the stability of the test coil system. In this paper, we report the engineering analysis and test results of the ITER test coil system. First, the water cooling analysis and design based on the finite element method (FEM) were performed to ensure the thermal stability. Then, the equivalent stress and deformation of the coil system under rated condition and seismic event were analyzed to verify the structural stability. Further, the inductance frequency characteristic of the coil system was analyzed through partial element equivalent circuit (PEEC) method to support the control strategy design of the power supply. In addition, a speeding-up inductance matrix calculation method was brought forward, which avoids redundant computation and significantly improves computational efficiency. At last, resistance, inductance, and temperature rise tests were completed to verify the design of the test coil.
Abstract
Only recently, plasma edge simulations up to the wall have been enabled with SOLPS‐ITER. This requires dedicated gridding techniques to reconcile grid alignment with the magnetic field and ...refinement toward the wall as grid quality is primordial to ensure fast and reliable convergence. Therefore, the gridding approach for the grids up to the wall is analyzed and improved. A truncation error analysis is performed on the discrete operators of the discretization scheme in SOLPS‐ITER, resulting in indicators of grid properties that are undesired. Based on these indicators, grid adaptation and grid smoothing algorithms are developed to reduce truncation errors and improve the overall grid quality. The resulting methods are applied on an AUG single‐null case. Here, the impact of the new gridding strategy is examined on the divertor heat load, a typical quantity of interest for plasma edge simulations. The new gridding methods allow to mitigate spurious numerical spikes in the target heat load profiles, reduce the convergence time with a factor 30, and improve the accuracy of the heat load with a factor 3 compared to original grids with similar total number of cells.
The fourth CS Module (CSM#4) of the ITER Central Solenoid was tested in November/December 2022 at the premises of General Atomics, Poway, US. During the measurement campaign, the CSM#4 was submitted ...to dumps of the transport current from different initial values (from 0 to 40 kA) to 0 kA. The tests were performed both in virgin conditions and after 10 slow current cycles. This work analyses the experimental dumps of the CSM#4 to determine the losses in the CICC via the measurement of the energy deposited in the supercritical helium. The losses in the magnet are presented pointing out the impact of the slow current cycles. The latter also allow one measuring the hysteresis losses of the magnet. In the previous module tests, as well as in the tests of a single layer solenoid (referred to as CS Insert), it was very difficult to retrieve reliable values of the hysteresis losses in the CS conductor. However, the knowledge of hysteresis losses is crucial for a correct heat inventory of the magnet in operation. This study reports the results of their measurement, which represents a relevant added value of the CSM#4 tests. Finally, the experimental data are compared with the results of analytical models developed for the loss computation.
•Accounting for spatial distribution of the stray radiation energy flux, including ports and cryopumps during start-up in the first plasma operation and later.•Distribution of stray radiation energy ...flux originating from 1 MW 60 GHz diagnostic gyrotron.•Calculation of the effective wall reflectivity for the power balance studies and radiation losses through ECE.
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Here we re-evaluate the stray radiation loads due to electron cyclotron resonance heating and diagnostic gyrotrons in ITER, as well as compute the stray radiation energy flux due to electron cyclotron emission. Microwave loads due to stray radiation were assessed in the past. We give here more comprehensive estimates, including spatial variations in the machine. We show that for the start-up phase in the First Plasma campaign the threshold of 100 kW/m2, which diagnostics have to be able to withstand, is not exceeded. For the later campaigns, the stray radiation energy flux during start-up and burnthrough will exceed 450 kW/m2. Stray radiation from electron cyclotron emission and from a diagnostic 60 GHz gyrotron can contribute to more than 140 kW/m2 combined.
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.
Feeder-type joint assembly is identified as a non-conventional process that require robust qualification not only on the process, but also on the skill of the operators so as to grant an access to ...construction site. The joint assembly qualification sample underwent a test program in regards to different operation conditions in various magnetic fields, currents and helium mass flows, etc. The results support the proven process of the joint assembly performed by knowledgeable personnel who service s the operator training and qualification. It is also aimed to report that the test performance of the qualification sample reaffirms the previous test result. Further verification on the joint characteristics was performed. The first-of-a-kind assembly on the segmented superconducting busbars is being prepared using an approach where risks are identified, assessed and prioritized. On-site assembly readiness on the busbar joint assembly process through an operator qualification program is addressed.
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