Location via proxy:   [ UP ]  
[Report a bug]   [Manage cookies]                
Skip to main content

    T. Scherer

    Karlsruhe Institute of Technology (KIT) is doing research and development in the field of high power gyrotrons for W7-X, ITER, and, towards a future DEMOnstration fusion power plant. While the initial installation of the ECRH system at... more
    Karlsruhe Institute of Technology (KIT) is doing research and development in the field of high power gyrotrons for W7-X, ITER, and, towards a future DEMOnstration fusion power plant. While the initial installation of the ECRH system at W7-X is finished and operating very successfully, KIT is still involved in the development of gyrotrons for ITER. This work is coordinated by F4E and ongoing in frame of EGYC. Moreover, as part of EUROfusion, KIT is investing in the research for advanced fusion gyrotrons of future EU DEMO. The target is to develop gyrotrons which will fulfil the need for RF sources operating at a frequency above 200 GHz, an RF output power above 2 MW and a total efficiency above 60 %. Aditionally, multi-purpose/multi-frequency operation and frequency step-tunability are requested. That requires the research and development on advanced gyrotrons, test environments and control techniques. This contribution provides a view over ongoing and planned activities in the field of gyrotron development at KIT.
    ABSTRACT The ITER Electron Cyclotron Heating and Current Drive (ECH&CD) Upper Launcher, whose preliminary design was approved in 2009, is on its way towards the final design. The design work is being done by a consortium of... more
    ABSTRACT The ITER Electron Cyclotron Heating and Current Drive (ECH&CD) Upper Launcher, whose preliminary design was approved in 2009, is on its way towards the final design. The design work is being done by a consortium of several European research institutes in tight collaboration with F4E. The main focus is the finalization of the design of all components for the First Confinement System (FCS), which forms the vacuum and Tritium barrier. The FCS comprises structural components as well as the external waveguide components in the port cell. Structural components of the FCS include the flange seal, backend frame and closure plate. The external waveguide components include the isolation valve, CVD diamond windows, miter bends and straight waveguides. Because finalizing of the design of these components is directly influenced by the layout of many in-vessel components, the design work includes also further development of the entire launcher. This paper summarizes the most recent status of the design work on the structural components of the launcher FCS, which are the support flange, the socket, the closure plate and feed-throughs for waveguides and cooling pipes. The design work includes the engineering layout of these components in accordance with system requirements, load specifications and Quality and Safety classification. An outline of the overall design of the launcher will be presented. The design progress was based on a set of related analyses, of which particular results are given. Also the integration of the associated mm-wave components, assembly strategies, neutronic aspects and the design of the shielding components will be described.
    Four ECH Upper Port Plugs are foreseen at ITER for counteracting plasma instabilities based on the injection of up to 20 MW mm-wave power at 170 GHz into the plasma. The required targeting of flux surfaces will be achieved by angular... more
    Four ECH Upper Port Plugs are foreseen at ITER for counteracting plasma instabilities based on the injection of up to 20 MW mm-wave power at 170 GHz into the plasma. The required targeting of flux surfaces will be achieved by angular steering in the poloidal direction. The paper describes the main components of the mm-wave and structural system for the
    ABSTRACT The design of the ITER Electron Cyclotron Heating and Current Drive (ECH&CD) Upper launcher is recently in the first of two final design phases. The first phase deals with the finalization of all FCS (First... more
    ABSTRACT The design of the ITER Electron Cyclotron Heating and Current Drive (ECH&CD) Upper launcher is recently in the first of two final design phases. The first phase deals with the finalization of all FCS (First Confinement System) components as well as with specific design progress for the remaining In-vessel components. The most outstanding structural In-vessel component of an ECH&CD Upper launcher is the Blanket Shield Module (BSM) with the First Wall Panel (FWP). Both of them form the plasma facing part of the launcher, which has to meet strong demands on dissipation of nuclear heat loads and mechanical rigidity. Nuclear heat loads from 3 MW/m3 at the First Wall Panel’ surface, decaying down to a tenth in a distance of 0.5 m behind of it will affect the BSM and the FWP. Additional heating of maximum 0.5 MW/m2 due to plasma radiation must be dissipated from the FWP. To guarantee save and homogenous removal of such extensive heat loads, the BSM is designed as a welded steel-case with specific cooling channels inside its wall structure. Attached to its face side is the FWP with a high-power cooling structure. Based on computational analysis the optimum cooling channel geometry has been investigated. Specific pre-prototype tests have been made and associated assembly parameters have been determined in order to identify optimum manufacturing processes and joining techniques, which guarantee a robust design with maximum geometrical accuracy. This paper describes the design, manufacturing and testing of a full-size mock-up of the BSM. The study was carried out in an industrial cooperation with MAN Diesel and Turbo SE.
    ABSTRACT RSFQ-toggle-flipflops with a SFQ-trigger circuit a Josephson transmission line at the input and a SFQ/dc-circuit at the output of each stage are implemented in the Nb–Al2O3–Nb Josephson junction technology on a single chip having... more
    ABSTRACT RSFQ-toggle-flipflops with a SFQ-trigger circuit a Josephson transmission line at the input and a SFQ/dc-circuit at the output of each stage are implemented in the Nb–Al2O3–Nb Josephson junction technology on a single chip having coplanar wave guides at input and output. The counter is tested successfully at 4.2K via coplanar/coaxial transitions using a bit pattern generator and a digital oscilloscope at room temperature up to fI≈2GHz pulse repetition frequency at the input. The highest test frequency fI is limited by the available pattern generator.
    ABSTRACT In this paper, we present first measurements, carried out at microwave wavelengths, aiming to characterize the dielectric properties of large size single crystalline diamond (SCD) wafers. While the sizes of the SCD wafers are... more
    ABSTRACT In this paper, we present first measurements, carried out at microwave wavelengths, aiming to characterize the dielectric properties of large size single crystalline diamond (SCD) wafers. While the sizes of the SCD wafers are still not sufficient for practical use, we obtained good optical properties results. The sample with both sides polished shows a dielectric loss tangent tanδ as low as or possibly lower than a polycrystalline diamond sample with high quality. Results show the importance of surface treatment, especially on the boundaries of the composed SCD chips even without any graphitic component in the diamond wafers.
    ABSTRACT
    The multi-frequency Electron Cyclotron Heating (ECRH) system at the ASDEX Upgrade tokamak employs depressed collector gyrotrons, step-tunable in the range 105-140 GHz. The system is equipped with a fast steerable launcher allowing for... more
    The multi-frequency Electron Cyclotron Heating (ECRH) system at the ASDEX Upgrade tokamak employs depressed collector gyrotrons, step-tunable in the range 105-140 GHz. The system is equipped with a fast steerable launcher allowing for remote steering of the ECRH beam during the plasma discharge. The polarization can be controlled in a feed-forward mode.
    A multi-frequency Electron Cyclotron Heating (ECRH) system is in operation at the ASDEX Upgrade tokamak, currently employing three depressed collector gyrotrons, operating at 105 and 140 GHz. The system offers a high flexibility for a... more
    A multi-frequency Electron Cyclotron Heating (ECRH) system is in operation at the ASDEX Upgrade tokamak, currently employing three depressed collector gyrotrons, operating at 105 and 140 GHz. The system offers a high flexibility for a variety of plasma heating and current drive experiments including remotely controlled fast beam steering and modulation.
    ... They can be integrated easily in rf circuits and allow acceptable properties at 77 K [8,9]. The phase shifter allows for rather large tolerances of the maximum Josephson current and can therefore be implemented with the present state... more
    ... They can be integrated easily in rf circuits and allow acceptable properties at 77 K [8,9]. The phase shifter allows for rather large tolerances of the maximum Josephson current and can therefore be implemented with the present state of technology. Fabrication ...
    ABSTRACT
    ABSTRACT A device on a single 2"-LaAlO 3 wafer for a four bit instantaneous frequency measurement between 9.5 GHz and 10.5 GHz has been developed with coplanar Y 1 B 2 Cu 3 O 7-d d delay lines and power dividers. Compared to... more
    ABSTRACT A device on a single 2"-LaAlO 3 wafer for a four bit instantaneous frequency measurement between 9.5 GHz and 10.5 GHz has been developed with coplanar Y 1 B 2 Cu 3 O 7-d d delay lines and power dividers. Compared to known triplate strip lines, coplanar delay lines are easier to fabricate monolithically and allow for a greater flexibility in the circuit design. Simulated and measured results are in good agreement. I. INTRODUCTION A 5 bit instantaneous frequency measurement (IFM) subsystem for a bandwidth of 500 MHz and a center frequency of 4 GHz has already been implemented with Y 1 Ba 2 Cu 3 O 7-d delay lines on LaAlO 3 substrates [1]. The 5-way power divider and each of the 5 discriminators have been fabricated separately and placed in 6 massive aluminum subpackages. Delays up to 16 ns have been achieved with striplines in dual-spiral form comprising two 508 m thick LaAlO 3 substrates pressed together. Each discriminator had a microstrip Wilkinson power divider [2] an...
    CVD diamond is a well known excellent low loss material (tan δ ≤ 10−5) for microwave transmission e.g. in fusion reactors for the ECRH&CD system. Laser processing of diamond discs allows the artificial formation of grooves on diamond disc... more
    CVD diamond is a well known excellent low loss material (tan δ ≤ 10−5) for microwave transmission e.g. in fusion reactors for the ECRH&CD system. Laser processing of diamond discs allows the artificial formation of grooves on diamond disc surfaces. A potential application is the design of windows with a surface finish offering an increased bandwidth. As grooves with sharp edges and corners might lead to local stress accumulation beyond tolerable limits, the method has been checked by FEM analyses. The results are here summarized.
    Research Interests:
    Ultra low mm-wave loss CVD diamond windows with loss tangent tan delta < 2 × 10-5 have been manufactured. The status of the window design is reviewed. The fabrication of the prototypical window unit is qualified for the selected... more
    Ultra low mm-wave loss CVD diamond windows with loss tangent tan delta < 2 × 10-5 have been manufactured. The status of the window design is reviewed. The fabrication of the prototypical window unit is qualified for the selected diamond grades by a dielectric characterisation carried out by low power measurement (FZK). The high power RF performance is quantified by
    During ITER operation malfunctions of the control system due to excessively large perturbations and for special configurations can lead to vertical displacement events (VDE), where a vertical plasma movement is followed by a fast or slow... more
    During ITER operation malfunctions of the control system due to excessively large perturbations and for special configurations can lead to vertical displacement events (VDE), where a vertical plasma movement is followed by a fast or slow plasma current quench. As a result during the plasma breakdown induced eddy and halo currents cause severe loads on the in-vessel components. For the
    ABSTRACT
    ABSTRACT
    Summary form only given. The candidate materials for high power mm-wave window materials like sapphire, boron nitride, high-resistivity silicon, CVD-diamond and silicon carbide will be presented and the production technology briefly... more
    Summary form only given. The candidate materials for high power mm-wave window materials like sapphire, boron nitride, high-resistivity silicon, CVD-diamond and silicon carbide will be presented and the production technology briefly described. The material parameters will be discussed which are most relevant for high power operation. Experimental data of absorption values in selected grades of window materials will be reported
    ABSTRACT Chemical vapor deposition (CVD) diamond windows are a crucial component in heating and current drive (H&CD) applications. In order to minimize the amount of reflected power from the diamond disc, its thickness must match... more
    ABSTRACT Chemical vapor deposition (CVD) diamond windows are a crucial component in heating and current drive (H&CD) applications. In order to minimize the amount of reflected power from the diamond disc, its thickness must match the desired beam wavelength, thus proper targeting of the plasma requires movable beam reflectors. This is the case, for instance, of the ITER electron cyclotron H&CD system. However, looking at DEMO, the higher heat loads and neutron fluxes could make the use of movable parts close to the plasma difficult. The issue might be solved by using gyrotrons able to tune the beam frequency to the desired resonance, but this concept requires transmission windows that work in a given frequency range, such as the Brewster window. It consists of a CVD diamond disc brazed to two copper cuffs at the Brewster angle. The brazing process is carried out at about 800°C and then the temperature is decreased down to room temperature. Diamond and copper have very different thermal expansion coefficients, therefore high stresses build up during the cool down phase that might lead to failure of the disc. Considering also the complex geometry of the window with the skewed position of the disc, analyses are required in the first place to check its feasibility. The cool down phase was simulated by FEM structural analyses for several geometric and constraint configurations of the window. A study of indirect cooling of the window by water was also performed considering a HE11 mode beam. The results are here reported.
    ABSTRACT Seven gyrotrons are currently in operation in the ASDEX Upgrade Electron Cyclotron Resonance Heating (ECRH) system delivering a total of 3.9 MW to the plasma at 140 GHz. The 3 new gyrotrons are capable of 2-frequency operation... more
    ABSTRACT Seven gyrotrons are currently in operation in the ASDEX Upgrade Electron Cyclotron Resonance Heating (ECRH) system delivering a total of 3.9 MW to the plasma at 140 GHz. The 3 new gyrotrons are capable of 2-frequency operation and may heat the plasma alternatively with 2.1 MW at 105 GHz.
    ABSTRACT In the frame of the new grant signed in November 2011 between Fusion for Energy (F4E) and the ECHUL-CA consortium, the development process of the Electron Cyclotron Heating and Current Drive (EC H&CD) Upper Launcher (UL)... more
    ABSTRACT In the frame of the new grant signed in November 2011 between Fusion for Energy (F4E) and the ECHUL-CA consortium, the development process of the Electron Cyclotron Heating and Current Drive (EC H&CD) Upper Launcher (UL) in ITER has moved a step towards the final design phase. The Blanket Shield Module (BSM) is a plasma facing component located at the tip of the launcher. The structure consists of a first wall panel (FWP) and a shell both with embedded cooling channels. A flange on the rear part allows the BSM to be connected by bolts to the main frame of the UL. Being a plasma facing component, the BSM is subjected to severe heat loads due to both thermal and nuclear irradiation. The current baseline value of surface heat load during normal plasma operation is 0.5 MW/m2, while the volumetric nuclear heating is responsible for a total generation of about 160 kW. The temperature gradients resulting from the abovementioned heat loads have been assessed by FEM analyses. The temperature distributions are then transferred to a structural model for calculation of the induced thermal stresses. The surface heat load is applied to the FWP as a constant flux. The nuclear loads, instead, were assessed by MCNP calculations and are provided by means of a mesh tally with a grid step of 1 cm. The results have shown that the temperature reaches 260 °C at the FWP and at the flange of the BSM. As a consequence of large temperature gradients, high stresses (in the order of 200 MPa) are also induced at the inner cooling channels of the BSM's structure.
    ABSTRACT
    A 26 MW Electron Cyclotron Heating and Current Drive (EC H&CD) system is to be installed for ITER. The main objectives are to provide, start-up assist, central H&CD and control of MHD activity. These are achieved by a combination... more
    A 26 MW Electron Cyclotron Heating and Current Drive (EC H&CD) system is to be installed for ITER. The main objectives are to provide, start-up assist, central H&CD and control of MHD activity. These are achieved by a combination of two types of launchers, one located in an equatorial port and the second type in four upper ports. The physics applications are partitioned between the two launchers, based on the deposition location and driven current profiles. The equatorial launcher (EL) will access from the plasma axis to mid radius with a relatively broad profile useful for central heating and current drive applications, while the upper launchers (ULs) will access roughly the outer half of the plasma radius with a very narrow peaked profile for the control of the Neoclassical Tearing Modes (NTM) and sawtooth oscillations. The EC power can be switched between launchers on a time scale as needed by the immediate physics requirements. A revision of all injection angles of all launchers is under consideration for increased EC physics capabilities while relaxing the engineering constraints of both the EL and ULs. A series of design reviews are being planned with the five parties (EU, IN, JA, RF, US) procuring the EC system, the EC community and ITER Organization (IO). The review meetings qualify the design and provide an environment for enhancing performances while reducing costs, simplifying interfaces, predicting technology upgrades and commercial availability. In parallel, the test programs for critical components are being supported by IO and performed by the Domestic Agencies (DAs) for minimizing risks. The wide participation of the DAs provides a broad representation from the EC community, with the aim of collecting all expertise in guiding the EC system optimization. Still a strong relationship between IO and the DA is essential for optimizing the design of the EC system and for the installation and commissioning of all ex-vessel components when several teams from several DAs will be involved together in the tests on the ITER site.
    NTRODUCTION J u n c ti o n s a l o n g a g r a i n bo u n d a r y o f t h e s u b s t r a t e a r e v e r y p r o mi s i n g f o r f
    To counteract plasma instabilities, Electron Cyclotron launchers with a total Millimeter-wave power of 20 MW are installed into four of the ITER Upper Ports. Each Mm-wave-system consists of eight transmission lines; a quasi-optical... more
    To counteract plasma instabilities, Electron Cyclotron launchers with a total Millimeter-wave power of 20 MW are installed into four of the ITER Upper Ports. Each Mm-wave-system consists of eight transmission lines; a quasi-optical focusing mirror system and two steerable front mirrors to be capable of injecting the beams over the range plasma instabilities are susceptible to occur. The Mm-wave-systems are
    ABSTRACT After approval of the preliminary design of the ITER EC H&CD Upper Launcher, ECHUL-CA, a consortium of several European research institutes, was founded to pool resources for approaching the final design. At the end of... more
    ABSTRACT After approval of the preliminary design of the ITER EC H&CD Upper Launcher, ECHUL-CA, a consortium of several European research institutes, was founded to pool resources for approaching the final design. At the end of 2011 the consortium has signed a 2 years contract with F4E to go ahead with the work on the launcher. The contract deals with design work on both the port plug, forming the structural system, and the mm-wave-system, which injects the RF-power into the plasma. Within the period of this contract all components being part of the Tritium confinement, of which the closure plate, the support flange, the diamond windows and the waveguide feed-throughs are the most outstanding ones, will get the status of the final design.Important steps to be done for the structural system are the optimization of the mechanical behavior of the launcher, leading to minimum deflections of the port plug during plasma disruptions and optimum seismic resistance. To reduce the effect of halo currents it was decided to recess the first wall of 100 mm compared to the regular blanket tangent. This recess requires substantial changes of the cooling system and the thermo-hydraulic design of the launcher. Also the layout of the shielding arrangement and the integration of the mm-wave system need significant revision. Moreover manufacturing aspects and enhanced remote handling capability are taken into account.For the final design also quality aspects must be considered; thus the design is elaborated with respect to applicable codes and standards, material specifications, risk analyses and the RAMI (reliability, availability, maintainability and inspectability) analysis to guarantee maximum performance of the device.This paper outlines the present status of the structural system of the EC H&CD upper launcher and represents the most recent steps towards its final design.

    And 8 more