Ion Beam Test Facility Research Articles

Latest achievements of the negative ion beam test facility ELISE

The negative ion source test facility ELISE represents an important step in the European R&D roadmap for the neutral beam injection (NBI) systems of ITER. Its aim is to consolidate the design and to gain early experimental experience with a large and modular Radio Frequency (RF) negative ion source and an ITER like extraction system of the same width but half the height of the ITER source (0.9 × 1 m2). H− and D− beams can be extracted and accelerated up to 60 kV for 10 s every ∼150 s out of the continuously operating plasma source.For short plasma pulses (10 s), the extracted negative ion current densities in hydrogen have almost reached the ITER requirement (329 A/m2 H‾, 286 A/m2 D‾). Also the required long pulse source operation up to 1000 s (H-)/3600 s (D-) could be demonstrated on ELISE with repetitive beam blips, but with reduced current densities. The main limitations are the amount and temporal stability of co-extracted electrons, especially in deuterium operation. This co-extracted electron current has to remain below the extracted ion current to avoid thermal overloading of the extraction grid. Magnetic field configurations, electric potentials of source surfaces close to the extraction system and caesium management are under investigation as tools for source performance optimization. Furthermore RF issues such as heating of source components, RF breakdowns and RF matching have been solved for high power source operation.

Installation of spectrally selective imaging system in RF negative ion source.

A spectrally selective imaging system has been installed in the RF negative ion source in the International Thermonuclear Experimental Reactor-relevant negative ion beam test facility ELISE (Extraction from a Large Ion Source Experiment) to investigate distribution of hydrogen Balmer-α emission (Hα) close to the production surface of hydrogen negative ion. We selected a GigE vision camera coupled with an optical band-path filter, which can be controlled remotely using high speed network connection. A distribution of Hα emission near the bias plate has been clearly observed. The same time trend on Hα intensities measured by the imaging diagnostic and the optical emission spectroscopy is confirmed.

Commissioning and first results of the ITER-relevant negative ion beam test facility ELISE

The test facility ELISE which was constructed in the last three years at the Max-Planck-Institut für Plasmaphysik (IPP), Garching, is an important intermediate step of the development of the neutral beam system for ITER. ELISE allows gaining an early experience of the performance and operation of large RF driven sources for negative hydrogen ions and will give an important input for the commissioning and the design of the SPIDER and MITICA test facilities at Padua and the ITER neutral beam system. ELISE has gone recently into operation with first plasma and beam pulses. The experiments aim at the demonstration of an ion beam at the required parameters within 2 years of operation until end of 2014, the end of the service contract with F4E for the establishment and exploitation of ELISE.

First results of the ITER-relevant negative ion beam test facility ELISE (invited)

An important step in the European R&D roadmap towards the neutral beam heating systems of ITER is the new test facility ELISE (Extraction from a Large Ion Source Experiment) for large-scale extraction from a half-size ITER RF source. The test facility was constructed in the last years at Max-Planck-Institut für Plasmaphysik Garching and is now operational. ELISE is gaining early experience of the performance and operation of large RF-driven negative hydrogen ion sources with plasma illumination of a source area of 1 × 0.9 m(2) and an extraction area of 0.1 m(2) using 640 apertures. First results in volume operation, i.e., without caesium seeding, are presented.

Thermal shock behaviour of tungsten after high flux H-plasma loading

Previous studies have shown that transient thermal shock loads induce crack networks on tungsten samples especially at low base temperatures. To achieve test conditions which are more relevant for the performance of tungsten-armoured plasma facing components in next step thermonuclear fusion devices tungsten tiles were exposed to high flux hydrogen-plasma in the linear plasma generator Pilot-PSI and the high heat flux ion beam test facility MARION. Subsequently, the cyclic transient heat load tests were done in the electron beam facility JUDITH 1. The induced damages after these combined tests were examined by microscopically means, profilometry and metallography. The comparison of the obtained results and damage characteristics with those obtained after thermal shock loading show that the preloading of tungsten targets with high flux hydrogen-plasma has significant influence on the thermal shock behaviour of tungsten in terms of crack distance, width, and depth as well as cracked area. Furthermore the plasma parameters, in particular pulse duration and sample temperature during loading, have strong impact on the damage pattern after thermal shock loading.

New options for material testing at the material ion beam test facility MARION

Within the development of new fusion devices like ITER and DEMO, material testing becomes more and more relevant. The material ion beam test facility MARION which was primarily designed for beam source development and commissioning is also used for high heat flux testing up to 120MW/m2 power density. In order to improve this second field of activity the concept of MARION is adapted to material testing. To increase the flexibility and to decrease the costs for material testing operation the vacuum system has been changed by excluding the cryogenic pumps combined with an enhancement of the conventional vacuum pumping part. The reduction in pumping capacity has made a new optimization of the operation parameters necessary.The experimental results of this optimization can be used as calibration base for future heat load tests. They are shown in this paper, combined with the changes in operation range for this new, additional mode.

Upgrade of the material ion beam test facility MARION for enhanced requirements of JET and ITER

The high heat flux ion beam test facility MARION (Material Research ION Beam test Stand) has been used for ion source conditioning and material testing within the IEK-4 for several years. Mainly small samples have been tested in the past by perpendicular irradiation. In these experiments only 25% of the available power density of MARION (>80 MW/m 2) was used so far. The activation of these resources for material testing was realized in the first test phase of the new tungsten divertor element for the JET tokamak. The enhancement of MARION by a new protection scraper is shown. During the last experiments the need of a more flexible handling of the sample itself and of the facility became clear. Based on those experiences an upgrade concept was developed to prepare MARION for future demands allowing the handling of much bigger prototypes. Additionally main emphasis is given to the access to improved (surface) diagnostics for all orientations of the target.

Development of water-cooled solid breeder test blanket module in JAEA

One of the most important missions of ITER is to provide a test bed for breeding blanket modules, which are called as test blanket module (TBM). JAEA has been extensively developing a water-cooled solid breeder test blanket module (WCSB TBM) for ITER. JAEA developed fabrication technology of F82H rectangular cooling tubes, and has successfully fabricated the near-full scale first wall mock-up of WCSB TBM by hot isostatic press (HIP) technique, which is fully made of F82H. The mock-up has been high-heat flux tested in the DATS facility in JAEA, which is an ion beam test facility. The inlet temperature of the cooling water is about 280 °C with 15 MPa, which is almost the same as the WCSB TBM design conditions. The mock-up has endured a heat load of 0.5 MW/m 2, 30 s for 80 thermal cycles. Neither hot spots nor thermal degradation have been observed.

High heat flux tests of the WENDELSTEIN 7-X pre-series target elements: Experimental evaluation of the thermo-mechanical behaviour

The high heat flux (HHF) testing of WENDELSTEIN 7-X pre-series target elements is an indispensable step in the qualification of the manufacturing process. A set of 20 full scale pre-series elements was manufactured by PLANSEE SE to validate the materials and manufacturing technologies prior to the start of the series production. The HHF tests were performed in the ion beam test facility GLADIS. All actively water-cooled elements were tested for about 100 cycles at 10 MW/m 2 (10–15 s pulse duration). Several elements were loaded with even higher cycle numbers (up to 1000) and heat loads up to 24 MW/m 2. Hot spots were, observed at the edges of several tiles during the HHF tests indicating local bonding problems of the CFC. The thermo-mechanical behaviour under HHF loading has been evaluated and compared to the FEM predictions. The measured temperatures and strains confirm the chosen FEM approach. This allows a component optimisation to achieve a successful series production of the W7-X divertor target elements.

Design, performance and construction of a 2 MW ion beam test facility for plasma facing components

A new facility for the testing of plasma facing components (PFC) under high heat fluxes is presently under construction at IPP Garching. The aim of this facility is to provide thermal testing capabilities for high heat loaded divertor components which have both active water cooling and large outer dimensions. The water-cooled test chamber is equipped with two ion sources for positive ion beam production. Initially, only one of the two individually controlled RF ion sources with 1.1 MW maximum beam power will be used for heat loading tests within an operating regime from 5 to 65 MW/m 2 at the target position. This paper presents the details of the technical characteristics and the systems for vacuum generation, cooling, power supply, control, target diagnostics and data acquisition.

Manufacturing and Testing of Actively Cooled Test Limiters for TEXTOR Made of an LPPS Tungsten-Coated TZM Heat Sink

To investigate the erosion and redeposition phenomena of fusion-related materials under stationary conditions, actively cooled test limiters were developed for the Tokamak Experiment for Technology Oriented Research (TEXTOR). The test limiters allow experiments under stationary conditions within a plasma pulse length of 10 s. Heat loads of typically 10 MW/m2 are removed by pressurized water; the volume flow is 10 m3/h, the pressure is 15 bar, and the minimum coefficient of heat transfer is nearly 70 000 W/m2·K. The limiters were manufactured as low-pressure plasma-spraying thermally sprayed tungsten-coated heat sinks made of the molybdenum alloy TZM. The required properties of the tungsten coating were developed by the use of a statistically based optimization routine. Optimized, actively cooled limiters were successfully tested in Forschungszentrum Jülich’s Material Research Ion Beam Test Facility (MARION) with hydrogen beams. Maximum heat loads of up to ~17 MW/m2 were applied without any failure of either the heat sink or the cooling system. The steady state of the surface temperature was measured within 2 s. Analytical and numerical models describing the effects of heat load distribution and spatial temperatures were found to be in excellent agreement with numerical predictions. In an additional experiment, loss of coolant was simulated. Transition boiling was generated, and after repeated heat loads higher than 10 MW/m2, cavitational damage of the heat sink occurred. Concerning the material selection for heat sinks of hypervapotrons and other cooling systems based on enhanced boiling of the cooling liquid, this result might be of special interest.

Manufacturing and testing of actively cooled test limiters for TEXTOR made of the brazed joint SEPCARB-N11/TZM

To investigate the erosion and redepositon phenomena of fusion-related materials under stationary conditions, actively cooled test limiters were developed for TEXTOR (Tokamak Experiment for Technology Orientated Research). They allow experiments under stationary conditions within the plasma pulse length of 10 s. Heat loads of typically 10 MW m −2 are removed by pressurised water: volume flow is 10 m 3 h −1, pressure 15 bar and the minimum coefficient of heat transfer is about 75 000 W m −2 K. Prototype limiters were built as brazed composites of a C/C material (SEPCARB-N11) and a TZM substrate. The samples were successfully tested in screening tests in the ion beam facility MARION (Material Research Ion Beam Test Facility) with hydrogen beams. Maximum heat loads of up to 22 MW m −2 were applied without any failure of the cooling system. Steady state of the surface temperature was measured within 5 s. An advanced brazing technique enabled the joining of hemispherically shaped C/C shells to a TZM heat sink without failure. An optimised test limiter was tested in TEXTOR. Analytical and numerical models describing the effects of the heat load distribution, spatial temperatures and stresses were experimentally verified.

High Heat Flux Test of CVD-Tungsten Coated Cu Heat Sink Divertor Mock-Up

CVD-tungsten coated divertor mock-ups were fabricated and tested in an ion beam test facility in JAERI. The mock-up consisted of a 2 mm thick CVD-tungsten on a 30 wt% Cu infiltrated tungsten skeleton heat sink. For the thermal fatigue tests, the heat load of 15 MW/m{sup 2}, 0.3 s was applied to simulate the bonding interface temperature under a steady heat load of 5 MW/m{sup 2}. The mock-up successfully endured a heat load of 15 MW/m{sup 2}, 0.3 s for more than 1000 thermal cycles. No cracks were observed at the bonding interface by optical microscope observation. Screening tests were also performed to evaluate the performance limit of the mock-up. The mock-up endured up to a heat load of 20 MW/m{sup 2}, 10 s without failure. 9 refs., 4 figs., 1 tab.

High-speed surface temperature measurements on plasma facing materials for fusion applications

For the lifetime evaluation of plasma facing materials in fusion experimental machines, it is essential to investigate their surface behavior and their temperature responses during an off-normal event such as the plasma disruptions. An infrared thermometer with a sampling speed as fast as 1×10−6 s/data, namely, the high-speed infrared thermometer (HSIR), has been developed by the National Research Laboratory of Metrology in Japan. To evaluate an applicability of the newly developed HSIR on the surface temperature measurement of plasma facing materials, high heat flux beam irradiation experiments have been performed with three different materials under the surface heat fluxes up to 170 MW/m2 for 0.04 s in a hydrogen ion beam test facility at the Japan Atomic Energy Research Institute. As for the results, HSIR can be applicable for measuring the surface temperature responses of the armor tile materials with a little modification. It is also confirmed that surface temperatures measured with the HSIR thermometer show good agreement with the analytical results for stainless steel and carbon based materials at a temperature range of up to 2500 °C. However, for aluminum the HSIR could measure the temperature of the high dense vapor cloud which was produced during the heating due to lower melting temperature. Based on the result, a multichannel arrayed HSIR thermometer has been designed and fabricated.

High sensitivity detectors for measurement of space potential fluctuations

A detection technique yielding an order of magnitude increase in the sensitivity of a Proca-Green type energy analyzer to beam energy fluctuations has been demonstrated. A sensitivity of <1 part in 10/sup 6/ is possible. The technique can be used to increase the sensitivity of a Heavy Ion Beam Probe (HIBP) to space potential fluctuations in a plasma. The increase in sensitivity is achieved by splitting the detected ion beam into 10 smaller beamlets and summing the signals produced by the beamlets. Experimental results from an ion beam test facility are presented along with the projected results if implemented on the 2 MeV HIBP on the TEXT-Upgrade tokamak.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

High heat flux performance of actively cooled divertor mock-ups

Abstract For the divertor of NET, actively cooled brazed CC/refractory metal mock-ups with an active length of 320 mm have been manufactured by Metallwerk Plansee, Austria, in order to evaluate the high heat flux performance of such structures. Seven tiles of CC material, 26 × 44.5 × 9 mm 3 , are brazed to an “interlayer” of TZM with a Zr braze. Subsequently this interlayer is brazed to a TZM body with a CuPd alloy. Inside the TZM body a tube of MoRe provides active cooling. In the ion beam test facility at KFA Julich two test series were performed. In order to determine the maximum tolerable heat load, the applied power density was increased stepwise at constant pulse lengths of 30 s in screening tests. The thermal fatigue behaviour of the divertor components was investigated by thermal cycling.

Performance of plasma sprayed B 4C coatings under high heat loads

In order to investigate the behaviour of B 4C coatings under thermal loading, a variety of substrates (fine grain graphite, carbon-carbon composite and the molybdenum alloy TZM) was covered with a coating of B 4C by low pressure plasma spray in an inert gas atmosphere. The thickness of the coating was varied between 125 and 250 μm. Mechanical tests proved good adhesion of the B 4C layer on all substrates. Tiles of the coated materials, 50 × 50 mm 2 and 50 × 25 mm 2 in size, were then exposed to high thermal fluxes in an ion beam test facility. The power densities applied on the specimens was varied between 3 and 10.5 MW/m 2 at pulse lengths up to 10 s (passively cooled specimens only). During thermal loading the surface temperature of the specimens was registered by means of optical pyrometers. Additionally, surface modifications of the specimens were observed with a video camera, and each pulse was recorded on tape. The results showed that already at surface temperatures below 2000°C crack formation in the B 4C coating and delamination occurred in particular for thick coatings (approximately 250 μm in thickness). On graphite substrates no melting of the B 4C-layer was observed up to more than 2100°C (melting temperature of B 4C ≈ 2400°C).

High Heat Flux Ion Beam Test Facility for Material Research and Development

The high heat flux ion beam test facility at Forschungszentrum Julich can produce peak power densities of 0.14 to 12 kW/cm2 for pulse lengths of 10 ms to 15 s. Longer pulses up to steady-state oper...