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Sample records for divertor cooling loop

  1. Liquid metal cooled divertor for ARIES

    SciTech Connect

    Muraviev, E.

    1995-01-01

    A liquid metal, Ga-cooled divertor design was completed for the double null ARIES-II divertor design. The design analysis indicated a surface heat flux removal capability of up to 15 MW/m{sup 2}, and its relative easy maintenance. Design issues of configuration, thermal hydraulics, thermal stresses, liquid metal loop and safety effects were evaluated. For coolant flow control, it was found that it is necessary to use some part of the blanket cooling ducts for the draining of liquid metal from the top divertor. In order to minimize the inventory of Ga, it was recommended that the liquid metal loop equipment should be located as close to the torus as possible. More detailed analysis of transient conditions especially under accident conditions was identified as an issue that will need to be addressed.

  2. Optimal thermal-hydraulic performance for helium-cooled divertors

    SciTech Connect

    Izenson, M.G.; Martin, J.L.

    1996-07-01

    Normal flow heat exchanger (NFHX) technology offers the potential for cooling divertor panels with reduced pressure drops (<0.5% {Delta}p/p), reduced pumping power (<0.75% pumping/thermal power), and smaller duct sizes than conventional helium heat exchangers. Furthermore, the NFHX can easily be fabricated in the large sizes required for divertors in large tokamaks. Recent experimental and computational results from a program to develop NFHX technology for divertor coolings using porous metal heat transfer media are described. We have tested the thermal and flow characteristics of porous metals and identified the optimal heat transfer material for the divertor heat exchanger. Methods have been developed to create highly conductive thermal bonds between the porous material and a solid substrate. Computational fluid dynamics calculations of flow and heat transfer in the porous metal layer have shown the capability of high thermal effectiveness. An 18-kW NFHX, designed to meet specifications for the international Thermonuclear Experimental Reactor divertor, has been fabricated and tested for thermal and flow performance. Preliminary results confirm design and fabrication methods. 11 refs., 12 figs., 1 tab.

  3. Closed loop steam cooled airfoil

    SciTech Connect

    Widrig, Scott M.; Rudolph, Ronald J.; Wagner, Gregg P.

    2006-04-18

    An airfoil, a method of manufacturing an airfoil, and a system for cooling an airfoil is provided. The cooling system can be used with an airfoil located in the first stages of a combustion turbine within a combined cycle power generation plant and involves flowing closed loop steam through a pin array set within an airfoil. The airfoil can comprise a cavity having a cooling chamber bounded by an interior wall and an exterior wall so that steam can enter the cavity, pass through the pin array, and then return to the cavity to thereby cool the airfoil. The method of manufacturing an airfoil can include a type of lost wax investment casting process in which a pin array is cast into an airfoil to form a cooling chamber.

  4. Fabrication of a He-cooled divertor module for DEMO reactor

    NASA Astrophysics Data System (ADS)

    Gervash, A.; Giniyatulin, R.; Ihli, T.; Krauss, W.; Makhankov, A.; Mazul, I.; Norajitra, P.; Yablokov, N.

    2007-08-01

    One current design of the divertor for a fusion reactor like DEMO uses He-cooled thimble-like tungsten, which is covered by sacrificial tungsten tile. Each thimble has to be connected with a supporting unit made from ferritic steel. This paper describes the development of joining techniques between tungsten thimbles and steel supporting units. Paper also provides an evaluation of simple geometries up to more complex conical interlocks filled with cast copper. Four candidates tungsten alloys (WL10, W-single crystal, W-Cu composite and chemical vapour deposited (CVD) tungsten) were experimentally checked by 'non-isothermal' heating to characterize the thermal gradient in the range 600 °C (for joint) and more than 1000 °C (for thimble top) using a special testing procedure. Basing on the test results, several mock-ups were manufactured for future high heat flux testing in a helium loop.

  5. Design and analysis of the DII-D radiative divertor water-cooled structures

    SciTech Connect

    Hollerbach, M.A.; Smith, J.P.; Baxi, C.B.; Bozek; Chin, E.; Phelps, R.D.; Redler, K.M.; Reis, E.E.

    1995-10-01

    The Radiative Divertor is a major modification to the divertor of DIII-D and is being designed and fabricated for installation in late 1996. The Radiative Divertor Program (RDP) will enhance the dissipative processes in the edge and divertor plasmas to reduce the heat flux and plasma erosion at the divertor target. This approach will have major implications for the heat removal methods used in future devices. The divertor is of slot-type configuration designed to minimize the flow of sputtered and injected impurities back to the core plasma. The new divertor will be composed of toroidally continuous, Inconel 625 water-cooled rings of sandwich construction with an internal water channel, incorporating seam welding to provide the water-to-vacuum seal as well as structural integrity. The divertor structure is designed to withstand electromagnetic loads as a result of halo currents and induced toroidal currents. It also accommodates the thermal differences experienced during the 400 {degrees}C bake used on DIII-D. A low Z plasma-facing surface is provided by mechanically attached graphite tiles. Water flow through the rings will inertially cool these tiles which will be subjected to 38 MW, 10 second pulses. Current schedules call for detailed design in 1996 with installation completed in March 1997. A full size prototype, one-quarter of one ring, is being built to validate manufacturing techniques, machining, roll-forming, and seam welding. The experience and knowledge gained through the fabrication of the prototype is discussed. The design of the electrically isolated (5 kV) vacuum-to-air water feedthroughs supplying the water-cooled rings is also discussed.

  6. Design and analysis of the DIII-D radiative divertor water-cooled structures

    SciTech Connect

    Hollerbach, M.A.; Smith, J.P.; Baxi, C.B.; Bozek, A.S.; Chin, E.; Phelps, R.D.; Redler, K.M.; Reis, E.E.

    1995-12-31

    The Radiative Divertor is a major modification to the divertor of DIII-D and is being designed and fabricated for installation in late 1996. The Radiative Divertor Program (RDP) will enhance the dissipative processes in the edge and divertor plasmas to reduce the heat flux and plasma erosion at the divertor target. This approach will have major implications for the heat removal methods used in future devices. The divertor is of slot-type configuration designed to minimize the flow of sputtered and injected impurities back to the core plasma. The new divertor will be composed of toroidally continuous, Inconel 625 water-cooled rings of sandwich construction with an internal water channel, incorporating seam welding to provide the water-to-vacuum seal as well as structural integrity. The divertor structure is designed to withstand electro-magnetic loads as a result of halo currents and induced toroidal currents. It also accommodates the thermal differences experienced during the 400 C bake used on DIII-D. A low Z plasma-facing surface is provided by mechanically attached graphite tiles. Water flow through the rings will inertially cool these tiles which will be subjected to 38 MW, 10 second pulses. Current schedules call for detailed design in 1996 with installation completed in March 1997. A full size prototype, one-quarter of one ring, is being built to validate manufacturing techniques, machining, roll-forming, and seam welding. The experience and knowledge gained through the fabrication of the prototype is discussed. The design of the electrically isolated (5 kV) vacuum-to-air water feedthroughs supplying the water-cooled rings is also discussed.

  7. THE COOLING OF CORONAL PLASMAS. IV. CATASTROPHIC COOLING OF LOOPS

    SciTech Connect

    Cargill, P. J.; Bradshaw, S. J.

    2013-07-20

    We examine the radiative cooling of coronal loops and demonstrate that the recently identified catastrophic cooling is due to the inability of a loop to sustain radiative/enthalpy cooling below a critical temperature, which can be >1 MK in flares, 0.5-1 MK in active regions, and 0.1 MK in long tenuous loops. Catastrophic cooling is characterized by a rapid fall in coronal temperature, while the coronal density changes by a small amount. Analytic expressions for the critical temperature are derived and show good agreement with numerical results. This effect considerably limits the lifetime of coronal plasmas below the critical temperature.

  8. Numerical Simulation on Subcooled Boiling Heat Transfer Characteristics of Water-Cooled W/Cu Divertors

    NASA Astrophysics Data System (ADS)

    Han, Le; Chang, Haiping; Zhang, Jingyang; Xu, Tiejun

    2015-04-01

    In order to realize safe and stable operation of a water-cooled W/Cu divertor under high heating condition, the exact knowledge of its subcooled boiling heat transfer characteristics under different design parameters is crucial. In this paper, subcooled boiling heat transfer in a water-cooled W/Cu divertor was numerically investigated based on computational fluid dynamic (CFD). The boiling heat transfer was simulated based on the Euler homogeneous phase model, and local differences of liquid physical properties were considered under one-sided high heating conditions. The calculated wall temperature was in good agreement with experimental results, with the maximum error of 5% only. On this basis, the void fraction distribution, flow field and heat transfer coefficient (HTC) distribution were obtained. The effects of heat flux, inlet velocity and inlet temperature on temperature distribution and pressure drop of a water-cooled W/Cu divertor were also investigated. These results provide a valuable reference for the thermal-hydraulic design of a water-cooled W/Cu divertor. supported by the National Magnetic Confinement Fusion Science Program of China (No. 2010GB104005), Funding of Jiangsu Innovation Program for Graduate Education (CXLX12_0170), the Fundamental Research Funds for the Central Universities of China

  9. Development of a helium-cooled divertor: Material choice and technological studies

    NASA Astrophysics Data System (ADS)

    Norajitra, P.; Boccaccini, L. V.; Gervash, A.; Giniyatulin, R.; Holstein, N.; Ihli, T.; Janeschitz, G.; Krauss, W.; Kruessmann, R.; Kuznetsov, V.; Makhankov, A.; Mazul, I.; Moeslang, A.; Ovchinnikov, I.; Rieth, M.; Zeep, B.

    2007-08-01

    Within the framework of the EU power plant conceptual study (PPCS), a He-cooled divertor concept has been investigated at Forschungszentrum Karlsruhe in cooperation with the Efremov Institute. The design goal is to remove a high heat load of at least 10 MW/m 2. The design is based on a modular construction of cooling finger unit that helps reduce thermal stresses. The divertor finger unit, which is cooled by high pressure helium, consists of a tungsten tile as thermal shield and sacrificial layer, and a thimble made of tungsten alloy. The success of this design depends strongly on the effectiveness of the cooling technology and on the availability of appropriate structural materials such as tungsten alloy and oxide-dispersion-strengthened (ODS) steel as well as the related fabrication and joining technology. Results of this investigation are discussed in the paper.

  10. TRANSVERSE OSCILLATIONS OF A COOLING CORONAL LOOP

    SciTech Connect

    Morton, R. J.; Erdelyi, R. E-mail: Robertus@sheffield.ac.u

    2009-12-10

    Here we present an investigation into how cooling of the plasma influences the oscillation properties (e.g., eigenfunctions and eigenfrequencies) of transverse (i.e., kink) magnetohydrodynamic (MHD) waves in a compressible magnetic flux tube embedded in a gravitationally stratified and uniformly magnetized atmosphere. The cooling is introduced via a temperature-dependent density profile. A time-dependent governing equation is derived and an approximate zeroth-order solution is then obtained. From this the influence of cooling on the behavior of the eigenfrequencies and eigenfunctions of the transverse MHD waves is determined for representative cooling timescales. It is shown analytically, as the loop cools, how the amplitude of the perturbations is found to decrease as time increases. For cooling timescales of 900-2000 s (as observed in typical EUV loops), it is shown that the cooling has important and relevant influence on the damping times of loop oscillations. Next, the theory is put to the test. The damping due to cooling is fitted to a representative observation of standing kink oscillation of EUV loops. It is also shown with an explicit approximate analytical form, how the period of the fundamental and first harmonic of the kink mode changes with time as the loop cools. A consequence of this is that the value of the period ratio P {sub 1}/P {sub 2}, a tool that is popular in magneto-seismological studies in coronal diagnostics, decreases from the value of a uniform loop, 2, as the temperature decreases. The rate of change in P {sub 1}/P {sub 2} is dependent upon the cooling timescale and is well within the observable range for typical EUV loops. Further to this, the magnitude of the anti-node shift of the eigenfunctions of the first harmonic is shown to continually increase as the loop cools, giving additional impetus to the use of spatial magneto-seismology of the solar atmosphere. Finally, we suggest that measurements of the rate of change in the

  11. Mars Pathfinder mechanically pumped cooling loop

    NASA Technical Reports Server (NTRS)

    Birur, G. C.

    2001-01-01

    A mechanically pumped single-phase cooling loop was successfully flown on the Mars Pathfinder (MPF) Spacecraft which safely landed on the Martian surface on July 4, 1997. One of the key technologies that enabled the mission to succeed was an active heat rejection system (HRS) used to cool the electronics on the spacecraft during its seven-month cruise from Earth to Mars.

  12. Experimental and numerical investigation of the thermal performance of gas-cooled divertor modules

    NASA Astrophysics Data System (ADS)

    Crosatti, Lorenzo

    Divertors are in-vessel, plasma-facing, components in magnetic-confinement fusion reactors. Their main function is to remove the fusion reaction ash (alpha-particles), unburned fuel, and eroded particles from the reactor, which adversely affect the quality of the plasma. A significant fraction (˜15 %) of the total fusion thermal power is removed by the divertor coolant and must, therefore, be recovered at elevated temperature in order to enhance the overall thermal efficiency. Helium is the leading coolant because of its high thermal conductivity, material compatibility, and suitability as a working fluid for power conversion systems using a closed high temperature Brayton cycle. Peak surface heat fluxes on the order of 10 MW/m2 are anticipated with surface temperatures in the region of 1,200 °C to 1,500 °C. Recently, several helium-cooled divertor designs have been proposed, including a modular T-tube design and a modular "finger" configuration with jet impingement cooling from perforated end caps. Design calculations performed using the FLUENTRTM CFD software package have shown that these designs can accommodate a peak heat load of 10 MW/m2. Extremely high heat transfer coefficients (˜50,000 W/(m2•K)) were predicted by these calculations. Since these values of heat transfer coefficient are considered to be "outside of the experience base" for gas-cooled systems, an experimental investigation has been undertaken to validate the results of the numerical simulations. Attention has been focused on the thermal performance of the T-tube and the "finger" divertor designs. Experimental and numerical investigations have been performed to support both divertor geometries. Excellent agreement has been obtained between the experimental data and model predictions, thereby confirming the predicted performance of the leading helium-cooled divertor designs for near- and long-term magnetic fusion reactor designs. The results of this investigation provide confidence in the

  13. Relationship of edge localized mode burst times with divertor flux loop signal phase in JET

    SciTech Connect

    Chapman, S. C.; Dendy, R. O.; Todd, T. N.; Webster, A. J.; Morris, J.; Watkins, N. W.; Calderon, F. A.

    2014-06-15

    A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM.

  14. Current state-of-the-art manufacturing technology for He-cooled divertor finger

    NASA Astrophysics Data System (ADS)

    Norajitra, P.; Antusch, S.; Giniyatulin, R.; Mazul, I.; Ritz, G.; Ritzhaupt-Kleissl, H.-J.; Spatafora, L.

    2011-10-01

    A divertor concept for DEMO has been investigated at Karlsruhe Institute of Technology (KIT) which has to withstand a heat flux of 10 MW/m 2. The design utilizes small finger module composed of a small tungsten tile brazed on a thimble made from tungsten alloy. The divertor finger is cooled by helium jet impingement at 10 MPa and 600 °C. The subject of this paper is technological studies on machining and braze joining the divertor components. Goal of this task, which is considered an important R&D issue, is to find out appropriate manufacturing methods to ensure high functionality and high reliability of the divertor as well as to meet the economic aspect. One of the major requirements for manufacturing is micro-crack-free surface of tungsten parts, since crack propagations in tungsten were observed in the previous high-heat-flux tests at Efremov. Different manufacturing methods and the corresponding results are discussed in the following report.

  15. Rapidly Moving Divertor Plates In A Tokamak

    SciTech Connect

    S. Zweben

    2011-05-16

    It may be possible to replace conventional actively cooled tokamak divertor plates with a set of rapidly moving, passively cooled divertor plates on rails. These plates would absorb the plasma heat flux with their thermal inertia for ~10-30 sec, and would then be removed from the vessel for processing. When outside the tokamak, these plates could be cooled, cleaned, recoated, inspected, and then returned to the vessel in an automated loop. This scheme could provide nearoptimal divertor surfaces at all times, and avoid the need to stop machine operation for repair of damaged or eroded plates. We describe various possible divertor plate designs and access geometries, and discuss an initial design for a movable and removable divertor module for NSTX-U.

  16. Helium-cooled divertor for DEMO: Manufacture and high heat flux tests of tungsten-based mock-ups

    NASA Astrophysics Data System (ADS)

    Norajitra, P.; Gervash, A.; Giniyatulin, R.; Hirai, T.; Janeschitz, G.; Krauss, W.; Kuznetsov, V.; Makhankov, A.; Mazul, I.; Ovchinnikov, I.; Reiser, J.; Widak, V.

    2009-04-01

    A helium-cooled divertor concept for DEMO has been investigated extensively at the Forschungszentrum Karlsruhe under the EU power plant conceptual study, the goal being to demonstrate performance under heat flux of 10 MW/m 2 at least. Work covers different areas ranging from conceptual design to analysis, materials and fabrication issues to experiments. Meanwhile, the He-cooled modular divertor concept with jet cooling (HEMJ) has been proposed as reference design. In cooperation with the Efremov Institute, manufacture and high heat flux testing of divertor elements was performed for design verification and proof-of-principle. This paper focuses on the technological study of the fabrication of mock-ups from W/W alloy and Eurofer steel supporting structure material. The high heat flux test results of 2006 and 2007 are summarised and discussed.

  17. Pre-irradiation testing of actively cooled Be-Cu divertor modules

    SciTech Connect

    Linke, J.; Duwe, R.; Kuehnlein, W.

    1995-09-01

    A set of neutron irradiation tests is prepared on different plasma facing materials (PFM) candidates and miniaturized components for ITER. Beside beryllium the irradiation program which will be performed in the High Flux Reactor (HFR) in Petten, includes different carbon fiber composites (CFQ) and tungsten alloys. The target values for the neutron irradiation will be 0.5 dpa at temperatures of 350{degrees}C and 700{degrees}C, resp.. The post irradiation examination (PIE) will cover a wide range of mechanical tests; in addition the degradation of thermal conductivity will be investigated. To determine the high heat flux (HHF) performance of actively cooled divertor modules, electron beam tests which simulate the expected heat loads during the operation of ITER, are scheduled in the hot cell electron beam facility JUDITH. These tests on a selection of different actively cooled beryllium-copper and CFC-copper divertor modules are performed before and after neutron irradiation; the pre-irradiation testing is an essential part of the program to quantify the zero-fluence high heat flux performance and to detect defects in the modules, in particular in the brazed joints.

  18. Boosted Fast Flux Loop Alternative Cooling Assessment

    SciTech Connect

    Glen R. Longhurst; Donna Post Guillen; James R. Parry; Douglas L. Porter; Bruce W. Wallace

    2007-08-01

    The Gas Test Loop (GTL) Project was instituted to develop the means for conducting fast neutron irradiation tests in a domestic radiation facility. It made use of booster fuel to achieve the high neutron flux, a hafnium thermal neutron absorber to attain the high fast-to-thermal flux ratio, a mixed gas temperature control system for maintaining experiment temperatures, and a compressed gas cooling system to remove heat from the experiment capsules and the hafnium thermal neutron absorber. This GTL system was determined to provide a fast (E > 0.1 MeV) flux greater than 1.0E+15 n/cm2-s with a fast-to-thermal flux ratio in the vicinity of 40. However, the estimated system acquisition cost from earlier studies was deemed to be high. That cost was strongly influenced by the compressed gas cooling system for experiment heat removal. Designers were challenged to find a less expensive way to achieve the required cooling. This report documents the results of the investigation leading to an alternatively cooled configuration, referred to now as the Boosted Fast Flux Loop (BFFL). This configuration relies on a composite material comprised of hafnium aluminide (Al3Hf) in an aluminum matrix to transfer heat from the experiment to pressurized water cooling channels while at the same time providing absorption of thermal neutrons. Investigations into the performance this configuration might achieve showed that it should perform at least as well as its gas-cooled predecessor. Physics calculations indicated that the fast neutron flux averaged over the central 40 cm (16 inches) relative to ATR core mid-plane in irradiation spaces would be about 1.04E+15 n/cm2-s. The fast-to-thermal flux ratio would be in excess of 40. Further, the particular configuration of cooling channels was relatively unimportant compared with the total amount of water in the apparatus in determining performance. Thermal analyses conducted on a candidate configuration showed the design of the water coolant and

  19. Powder Injection Molding for mass production of He-cooled divertor parts

    NASA Astrophysics Data System (ADS)

    Antusch, S.; Norajitra, P.; Piotter, V.; Ritzhaupt-Kleissl, H.-J.

    2011-10-01

    A He-cooled divertor for future fusion power plants has been developed at KIT. Tungsten and tungsten alloys are presently considered the most promising materials for functional and structural divertor components. The advantages of tungsten materials lie, e.g. in the high melting point, and low activation, the disadvantages are high hardness and brittleness. The machinig of tungsten, e.g. milling, is very complex and cost-intensive. Powder Injection Molding (PIM) is a method for cost effective mass production of near-net-shape parts with high precision. The complete W-PIM process route is outlined and, results of product examination discussed. A binary tungsten powder feedstock with a grain size distribution in the range 0.7-1.7 μm FSSS, and a solid load of 50 vol.% was developed. After heat treatment, the successfully finished samples showed promising results, i.e. 97.6% theoretical density, a grain size of approximately 5 μm, and a hardness of 457 HV0.1.

  20. Design and testing of a superfluid liquid helium cooling loop

    SciTech Connect

    Gavin, L.M.; Green, M.A.; Levin, S.M.; Smoot, G.F.; Witebsky, C.

    1989-07-01

    This paper describes the design and preliminary testing of a cryogenic cooling loop that uses a thermomechanical pump to circulate superfluid liquid helium. The cooling loop test apparatus is designed to prove forced liquid helium flow concepts that will be used on the Astromag superconducting magnet facility. 3 refs., 2 figs.

  1. Numerical simulations of transverse oscillations in radiatively cooling coronal loops

    NASA Astrophysics Data System (ADS)

    Magyar, Norbert; Van Doorsselaere, Tom; Marcu, Alexandru

    2016-05-01

    We aim to study the influence of radiative cooling on the standing kink oscillations of coronal loops. To solve the 3D MHD ideal problem, we use the FLASH code. Our model consists of a straight, density enhanced and gravitationally stratified magnetic flux tube. We perturbed the system initially, leading to a transverse oscillation of the structure, and followed its evolution for a number of periods. A realistic radiative cooling is implemented. Results are compared to available analytical theory. We find that in the linear regime (i.e. low amplitude perturbation and slow cooling) the obtained period and damping time are in good agreement with theory. The cooling leads to an amplification of the oscillation amplitude. However, the difference between the cooling and non-cooling cases is small (around 6% after 6 oscillations). In high amplitude runs with realistic cooling, instabilities deform the loop, leading to increased damping. In this case, the difference between cooling and non-cooling is still negligible at around 12%. A set of simulations with higher density loops are also performed, to explore what happens when the cooling takes place in a very short time (t cool ≈ 100 s). In this case, the difference in amplitude after nearly 3 oscillation periods for the low amplitude case is 21% between cooling and non-cooling cases. We strengthen the results of previous analytical studies that state that the amplification due to cooling is ineffective, and its influence on the oscillation characteristics is small, at least for the cases shown here. Furthermore, the presence of a relatively strong damping in the high amplitude runs even in the fast cooling case indicates that it is unlikely that cooling could alone account for the observed, flare-related undamped oscillations of coronal loops. These results may be significant in the field of coronal seismology, allowing its application to coronal loop oscillations with observed fading-out or cooling behaviour.

  2. Numerical simulations of transverse oscillations in radiatively cooling coronal loops

    NASA Astrophysics Data System (ADS)

    Magyar, N.; Van Doorsselaere, T.; Marcu, A.

    2015-10-01

    Aims: We aim to study the influence of radiative cooling on the standing kink oscillations of a coronal loop. Methods: Using the FLASH code, we solved the 3D ideal magnetohydrodynamic equations. Our model consists of a straight, density enhanced and gravitationally stratified magnetic flux tube. We perturbed the system initially, leading to a transverse oscillation of the structure, and followed its evolution for a number of periods. A realistic radiative cooling is implemented. Results are compared to available analytical theory. Results: We find that in the linear regime (i.e. low amplitude perturbation and slow cooling) the obtained period and damping time are in good agreement with theory. The cooling leads to an amplification of the oscillation amplitude. However, the difference between the cooling and non-cooling cases is small (around 6% after 6 oscillations). In high amplitude runs with realistic cooling, instabilities deform the loop, leading to increased damping. In this case, the difference between cooling and non-cooling is still negligible at around 12%. A set of simulations with higher density loops are also performed, to explore what happens when the cooling takes place in a very short time (tcool ≈ 100 s). In this case, the difference in amplitude after nearly 3 oscillation periods for the low amplitude case is 21% between cooling and non-cooling cases. We strengthen the results of previous analytical studies that state that the amplification due to cooling is ineffective, and its influence on the oscillation characteristics is small, at least for the cases shown here. Furthermore, the presence of a relatively strong damping in the high amplitude runs even in the fast cooling case indicates that it is unlikely that cooling could alone account for the observed, flare-related undamped oscillations of coronal loops. These results may be significant in the field of coronal seismology, allowing its application to coronal loop oscillations with observed

  3. Numerical Study of High Heat Flux Performances of Flat-Tile Divertor Mock-ups with Hypervapotron Cooling Concept

    NASA Astrophysics Data System (ADS)

    Chen, Lei; Liu, Xiang; Lian, Youyun; Cai, Laizhong

    2015-09-01

    The hypervapotron (HV), as an enhanced heat transfer technique, will be used for ITER divertor components in the dome region as well as the enhanced heat flux first wall panels. W-Cu brazing technology has been developed at SWIP (Southwestern Institute of Physics), and one W/CuCrZr/316LN component of 450 mm×52 mm×166 mm with HV cooling channels will be fabricated for high heat flux (HHF) tests. Before that a relevant analysis was carried out to optimize the structure of divertor component elements. ANSYS-CFX was used in CFD analysis and ABAQUS was adopted for thermal-mechanical calculations. Commercial code FE-SAFE was adopted to compute the fatigue life of the component. The tile size, thickness of tungsten tiles and the slit width among tungsten tiles were optimized and its HHF performances under International Thermonuclear Experimental Reactor (ITER) loading conditions were simulated. One brand new tokamak HL-2M with advanced divertor configuration is under construction in SWIP, where ITER-like flat-tile divertor components are adopted. This optimized design is expected to supply valuable data for HL-2M tokamak. supported by the National Magnetic Confinement Fusion Science Program of China (Nos. 2011GB110001 and 2011GB110004)

  4. Film cooling for a closed loop cooled airfoil

    DOEpatents

    Burdgick, Steven Sebastian; Yu, Yufeng Phillip; Itzel, Gary Michael

    2003-01-01

    Turbine stator vane segments have radially inner and outer walls with vanes extending therebetween. The inner and outer walls are compartmentalized and have impingement plates. Steam flowing into the outer wall plenum passes through the impingement plate for impingement cooling of the outer wall upper surface. The spent impingement steam flows into cavities of the vane having inserts for impingement cooling the walls of the vane. The steam passes into the inner wall and through the impingement plate for impingement cooling of the inner wall surface and for return through return cavities having inserts for impingement cooling of the vane surfaces. At least one film cooling hole is defined through a wall of at least one of the cavities for flow communication between an interior of the cavity and an exterior of the vane. The film cooling hole(s) are defined adjacent a potential low LCF life region, so that cooling medium that bleeds out through the film cooling hole(s) reduces a thermal gradient in a vicinity thereof, thereby the increase the LCF life of that region.

  5. The Corrected Simulation Method of Critical Heat Flux Prediction for Water-Cooled Divertor Based on Euler Homogeneous Model

    NASA Astrophysics Data System (ADS)

    Zhang, Jingyang; Han, Le; Chang, Haiping; Liu, Nan; Xu, Tiejun

    2016-02-01

    An accurate critical heat flux (CHF) prediction method is the key factor for realizing the steady-state operation of a water-cooled divertor that works under one-sided high heating flux conditions. An improved CHF prediction method based on Euler's homogeneous model for flow boiling combined with realizable k-ɛ model for single-phase flow is adopted in this paper in which time relaxation coefficients are corrected by the Hertz-Knudsen formula in order to improve the calculation accuracy of vapor-liquid conversion efficiency under high heating flux conditions. Moreover, local large differences of liquid physical properties due to the extreme nonuniform heating flux on cooling wall along the circumference direction are revised by formula IAPWS-IF97. Therefore, this method can improve the calculation accuracy of heat and mass transfer between liquid phase and vapor phase in a CHF prediction simulation of water-cooled divertors under the one-sided high heating condition. An experimental example is simulated based on the improved and the uncorrected methods. The simulation results, such as temperature, void fraction and heat transfer coefficient, are analyzed to achieve the CHF prediction. The results show that the maximum error of CHF based on the improved method is 23.7%, while that of CHF based on uncorrected method is up to 188%, as compared with the experiment results of Ref. [12]. Finally, this method is verified by comparison with the experimental data obtained by International Thermonuclear Experimental Reactor (ITER), with a maximum error of 6% only. This method provides an efficient tool for the CHF prediction of water-cooled divertors. supported by the National Magnetic Confinement Fusion Science Program of China (No. 2010GB104005) and National Natural Science Foundation of China (No. 51406085)

  6. Film cooling air pocket in a closed loop cooled airfoil

    DOEpatents

    Yu, Yufeng Phillip; Itzel, Gary Michael; Osgood, Sarah Jane; Bagepalli, Radhakrishna; Webbon, Waylon Willard; Burdgick, Steven Sebastian

    2002-01-01

    Turbine stator vane segments have radially inner and outer walls with vanes extending between them. The inner and outer walls are compartmentalized and have impingement plates. Steam flowing into the outer wall plenum passes through the impingement plate for impingement cooling of the outer wall upper surface. The spent impingement steam flows into cavities of the vane having inserts for impingement cooling the walls of the vane. The steam passes into the inner wall and through the impingement plate for impingement cooling of the inner wall surface and for return through return cavities having inserts for impingement cooling of the vane surfaces. To provide for air film cooing of select portions of the airfoil outer surface, at least one air pocket is defined on a wall of at least one of the cavities. Each air pocket is substantially closed with respect to the cooling medium in the cavity and cooling air pumped to the air pocket flows through outlet apertures in the wall of the airfoil to cool the same.

  7. Hot topic, warm loops, cooling plasma? Multithermal analysis of active region loops

    SciTech Connect

    Schmelz, J. T.; Pathak, S.; Christian, G. M.; Dhaliwal, R. S.; Brooks, D. H.

    2014-11-10

    We have found indications of a relationship between the differential emission measure (DEM) weighted temperature and the cross-field DEM width for coronal loops. The data come from the Hinode X-ray Telescope, the Hinode EUV Imaging Spectrometer, and the Solar Dynamics Observatory Atmospheric Imaging Assembly. These data show that cooler loops tend to have narrower DEM widths. If most loops observed by these instruments are composed of bundles of unresolved magnetic strands and are only observed in their cooling phase, as some studies have suggested, then this relationship implies that the DEM of a coronal loop narrows as it cools. This could imply that fewer strands are seen emitting in the later cooling phase, potentially resolving the long standing controversy of whether the cross-field temperatures of coronal loops are multithermal or isothermal.

  8. The Effect of Radiative Cooling on Coronal Loop Oscillations

    NASA Astrophysics Data System (ADS)

    Aschwanden, Markus J.; Terradas, Jaume

    2008-10-01

    Coronal loops that exhibit kink-mode oscillations have generally been assumed to have a constant density and temperature during the observed time interval. Analyzing their intensities in an EUV wave band, however, clearly shows that their brightness varies in a way that is consistent with a temperature cooling through the EUV passband, which limits their detection time, observed damping time, and number of observable periods. We study kink-mode oscillations of eight loops observed during the so-called harmonica event on 2001 April 15, 21:58-22:27 UT in the 171 Å band. We find loop densities of ne = (1.4 +/- 0.6) × 109 cm-3, loop widths of w = 2.0 +/- 2.6 Mm, and e-folding cooling times of τcool = 17 +/- 7 minutes, when they cool through the peak temperature T = 0.95 MK of the 171 Å band. We conclude that oscillations of a single loop cannot be detected longer than 10-20 minutes in one single filter and appropriate light curve modeling is necessary to disentangle the subsequent oscillation phases of multiple near-cospatial loops.

  9. Closed loop air cooling system for combustion turbines

    DOEpatents

    Huber, D.J.; Briesch, M.S.

    1998-07-21

    Convective cooling of turbine hot parts using a closed loop system is disclosed. Preferably, the present invention is applied to cooling the hot parts of combustion turbine power plants, and the cooling provided permits an increase in the inlet temperature and the concomitant benefits of increased efficiency and output. In preferred embodiments, methods and apparatus are disclosed wherein air is removed from the combustion turbine compressor and delivered to passages internal to one or more of a combustor and turbine hot parts. The air cools the combustor and turbine hot parts via convection and heat is transferred through the surfaces of the combustor and turbine hot parts. 1 fig.

  10. Closed loop air cooling system for combustion turbines

    DOEpatents

    Huber, David John; Briesch, Michael Scot

    1998-01-01

    Convective cooling of turbine hot parts using a closed loop system is disclosed. Preferably, the present invention is applied to cooling the hot parts of combustion turbine power plants, and the cooling provided permits an increase in the inlet temperature and the concomitant benefits of increased efficiency and output. In preferred embodiments, methods and apparatus are disclosed wherein air is removed from the combustion turbine compressor and delivered to passages internal to one or more of a combustor and turbine hot parts. The air cools the combustor and turbine hot parts via convection and heat is transferred through the surfaces of the combustor and turbine hot parts.

  11. Helium Loop Cooling Channel Hydraulic Characterization

    SciTech Connect

    Olivas, Eric Richard; Morgan, Robert Vaughn; Woloshun, Keith Albert

    2015-07-02

    New methods for generating ⁹⁹Mo are being explored in an effort to eliminate proliferation issues and provide a domestic supply of ⁹⁹mTc for medical imaging. Electron accelerating technology is used by sending an electron beam through a series of ¹⁰⁰Mo targets. During this process a large amount of heat is created, which directly affects the operating temperature set for the system. In order to maintain the required temperature range, helium gas is used to serve as a cooling agent that flows through narrow channels between the target disks. Currently we are tailoring the cooling channel entrance and exits to decrease the pressure drop through the targets. Currently all hardware has be procured and manufactured to conduct flow measurements and visualization via solid particle seeder. Pressure drop will be studied as a function of mass flow and diffuser angle. The results from these experiments will help in determining target cooling geometry and validate CFD code results.

  12. Study of Fluid Cooling Loop System in Chinese Manned Spacecraft

    NASA Astrophysics Data System (ADS)

    Jiang, Jun; Xu, Jiwan; Fan, Hanlin; Huang, Jiarong

    2002-01-01

    change. To solve the questions, a fluid cooling loop system must be applied to Chinese manned spacecraft besides other conventional thermal control methods, such as thermal control coatings, multiplayer insulation blankets, heat pipes, electro-heating adjustment temperature devices, and so on. The paper will introduce the thermal design of inner and outer fluid loop including their constitution and fundamental, etc. The capability of heat transportation and the accuracy of control temperature for the fluid loop will be evaluated and analyzed. To insure the air temperature of sealed cabins within 21+/-4, the inlet liquid temperature of condensing heat exchanger needs to be controlled within 9+/-2. To insure this, the inlet liquid temperature of middle heat exchanger needs to be controlled within 8+/-1.8. The inlet temperature point is controlled by a subsidiary loop adjusting: when the computer receives feedbacks of the deviation and the variety rate of deviation from the controlled temperature point. It drives the temperature control valve to adjust the flow flux distribution between the main loop through radiator and the subsidiary loop which isn't through radiator to control the temperature of the mixed fluid within 8+/-1.8. The paper will also introduce thermal designs of key parts in the cooling loop, such as space radiators, heat exchangers and cooling plates. Thermal simulated tests on the ground and flight tests have been performed to verify correctness of thermal designs. rational and the loop system works order. It realizes the circulation of absorbing heat dissipation to the loop and transferring it to radiator then radiating it to space. (2) loop control system controls inlet temperature of middle heat exchanger within 8+/-1.8 under various thermal cases. Thermal design of the middle heat exchanger insures inlet temperature of condensing heat within 9+/-2. Thereby, the air temperature of sealed cabins is controlled within about 21+/-4 accurately. (3) The

  13. The global build-up to intrinsic edge localized mode bursts seen in divertor full flux loops in JET

    NASA Astrophysics Data System (ADS)

    Chapman, S. C.; Dendy, R. O.; Todd, T. N.; Watkins, N. W.; Calderon, F. A.; Morris, J.

    2015-07-01

    A global signature of the build-up to an intrinsic edge localized mode (ELM) is found in the temporal analytic phase of signals measured in full flux azimuthal loops in the divertor region of JET. Toroidally integrating, full flux loop signals provide a global measurement proportional to the voltage induced by changes in poloidal magnetic flux; they are electromagnetically induced by the dynamics of spatially integrated current density. We perform direct time-domain analysis of the high time-resolution full flux loop signals VLD2 and VLD3. We analyze plasmas where a steady H-mode is sustained over several seconds during which all the observed ELMs are intrinsic; there is no deliberate intent to pace the ELMing process by external means. ELM occurrence times are determined from the Be II emission at the divertor. We previously [Chapman et al., Phys. Plasmas 21, 062302 (2014); Chapman et al., in 41st EPS Conference on Plasma Physics, Europhysics Conference Abstracts (European Physical Society, 2014), Vol. 38F, ISBN 2-914771-90-8] found that the occurrence times of intrinsic ELMs correlate with specific temporal analytic phases of the VLD2 and VLD3 signals. Here, we investigate how the VLD2 and VLD3 temporal analytic phases vary with time in advance of the ELM occurrence time. We identify a build-up to the ELM in which the VLD2 and VLD3 signals progressively align to the temporal analytic phase at which ELMs preferentially occur, on a ˜ 2 - 5 ms timescale. At the same time, the VLD2 and VLD3 signals become temporally phase synchronized with each other, consistent with the emergence of coherent global dynamics in the integrated current density. In a plasma that remains close to a global magnetic equilibrium, this can reflect bulk displacement or motion of the plasma. This build-up signature to an intrinsic ELM can be extracted from a time interval of data that does not extend beyond the ELM occurrence time, so that these full flux loop signals could assist in ELM

  14. Closed-loop air cooling system for a turbine engine

    DOEpatents

    North, William Edward

    2000-01-01

    Method and apparatus are disclosed for providing a closed-loop air cooling system for a turbine engine. The method and apparatus provide for bleeding pressurized air from a gas turbine engine compressor for use in cooling the turbine components. The compressed air is cascaded through the various stages of the turbine. At each stage a portion of the compressed air is returned to the compressor where useful work is recovered.

  15. Robust Cooling of High Heat Fluxes Using Hybrid Loop Technology

    NASA Astrophysics Data System (ADS)

    Zuo, Jon; Park, Chanwoo; Sarraf, David; Paris, Anthony

    2005-02-01

    This paper discusses the development of an advanced hybrid loop technology that incorporates elements from both passive and active loop technologies. The result is a simple yet high performance cooling technology that can be used to remove high heat fluxes from large heat input areas. Operating principles and test results of prototype hybrid loops are discussed. Prototype hybrid loops have been demonstrated to remove heat fluxes in excess of 350W/cm2 from heat input areas over 4cm2 with evaporator thermal resistances between 0.008 and 0.065°C/W/cm2. Also importantly, this performance was achieved without the need to actively adjust or control the flows in the loops, even when the heat inputs varied between 0 and 350W/cm2. These performance characteristics represent substantial improvements over state of the art heat pipes, loop heat pipes and spray cooling devices. The hybrid loop technology was demonstrated to operate effectively at all orientations.

  16. Numerical Calculation of the Peaking Factor of a Water-Cooled W/Cu Monoblock for a Divertor

    NASA Astrophysics Data System (ADS)

    Han, Le; Chang, Haiping; Zhang, Jingyang; Xu, Tiejun

    2015-09-01

    In order to accurately predict the incident critical heat flux (ICHF, the heat flux at the heated surface when CHF occurs) of a water-cooled W/Cu monoblock for a divertor, the exact knowledge of its peaking factors (fp) under one-sided heating conditions with different design parameters is a key issue. In this paper, the heat conduction in the solid domain of a water-cooled W/Cu monoblock is calculated numerically by assuming the local heat transfer coefficients (HTC) of the cooling wall to be functions of the local wall temperature, so as to obtain fp. The reliability of the calculation method is validated by an experimental example result, with the maximum error of 2.1% only. The effects of geometric and flow parameters on the fp of a water-cooled W/Cu monoblock are investigated. Within the scope of this study, it is shown that the fp increases with increasing dimensionless W/Cu monoblock width and armour thickness (the shortest distance between the heated surface and Cu layer), and the maximum increases are 43.8% and 22.4% respectively. The dimensionless W/Cu monoblock height and Cu thickness have little effect on fp. The increase of Reynolds number and Jakob number causes the increase of fp, and the maximum increases are 6.8% and 9.6% respectively. Based on the calculated results, an empirical correlation on peaking factor is obtained via regression. These results provide a valuable reference for the thermal-hydraulic design of water-cooled divertors. supported by National Magnetic Confinement Fusion Science Program of China (No. 2010GB104005) and Funding of Jiangsu Innovation Program for Graduate Education, China (CXLX12_0170), the Fundamental Research Funds for the Central Universities of China

  17. Heating and cooling of coronal loops observed by SDO

    NASA Astrophysics Data System (ADS)

    Li, L. P.; Peter, H.; Chen, F.; Zhang, J.

    2015-11-01

    Context. One of the most prominent processes to have been suggested as heating the corona to well above 106 K builds on nanoflares, which are short bursts of energy dissipation. Aims: We compare observations to model predictions to test the validity of the nanoflare process. Methods: Using extreme UV data from AIA/SDO and HMI/SDO line-of-sight magnetograms, we study the spatial and temporal evolution of a set of loops in active region AR 11850. Results: We find a transient brightening of loops in emission from Fe xviii forming at about 7.2 MK, while at the same time these loops dim in emission from lower temperatures. This points to a fast heating of the loop that goes along with evaporation of material that we observe as apparent upward motions in the image sequence. After this initial phase lasting some 10 min, the loops brighten in a sequence of AIA channels that show progressively cooler plasma, indicating that this cooling of the loops lasts about one hour. A comparison to the predictions from a 1D loop model shows that this observation supports the nanoflare process in (almost) all aspects. In addition, our observations show that the loops get broader while getting brighter, which cannot be understood in a 1D model. Movie associated to Fig. 1 is available in electronic form at http://www.aanda.org

  18. Longitudinal magnetohydrodynamics oscillations in dissipative, cooling coronal loops

    SciTech Connect

    Al-Ghafri, K. S.; Ruderman, M. S.; Williamson, A.; Erdélyi, R. E-mail: m.s.ruderman@sheffield.ac.uk E-mail: robertus@sheffield.ac.uk

    2014-05-01

    This paper investigates the effect of cooling on standing slow magnetosonic waves in coronal magnetic loops. The damping mechanism taken into account is thermal conduction that is a viable candidate for dissipation of slow magnetosonic waves in coronal loops. In contrast to earlier studies, here we assume that the characteristic damping time due to thermal conduction is not small, but arbitrary, and can be of the order of the oscillation period, i.e., a temporally varying plasma is considered. The approximation of low-beta plasma enables us to neglect the magnetic field perturbation when studying longitudinal waves and consider, instead, a one-dimensional motion that allows a reliable first insight into the problem. The background plasma temperature is assumed to be decaying exponentially with time, with the characteristic cooling timescale much larger than the oscillation period. This assumption enables us to use the WKB method to study the evolution of the oscillation amplitude analytically. Using this method we obtain the equation governing the oscillation amplitude. The analytical expressions determining the wave properties are evaluated numerically to investigate the evolution of the oscillation frequency and amplitude with time. The results show that the oscillation period increases with time due to the effect of plasma cooling. The plasma cooling also amplifies the amplitude of oscillations in relatively cool coronal loops, whereas, for very hot coronal loop oscillations the damping rate is enhanced by the cooling. We find that the critical point for which the amplification becomes dominant over the damping is in the region of 4 MK. These theoretical results may serve as impetus for developing the tools of solar magneto-seismology in dynamic plasmas.

  19. High capacity 30 K remote helium cooling loop

    NASA Astrophysics Data System (ADS)

    Trollier, T.; Tanchon, J.; Icart, Y.; Ravex, A.

    2014-01-01

    Absolut System has built several 50 K remote helium cooling loops used as high capacity and very low vibration cooling source into large wavelength IR detectors electro-optical characterization test benches. MgB2 based superconducting electro-technical equipment's under development require also distributed high cooling power in the 20-30 K temperature range. Absolut System has designed, manufactured and tested a high capacity 30 K remote helium cooling loop. The equipment consists of a CRYOMECH AL325 type cooler, a CP830 type compressor package used as room temperature circulator and an intermediate LN2 bath cooling used between two recuperator heat exchangers (300 K-77 K and 77 K-20 K). A cooling capacity of 30 W @ 20 K or 80 W @ 30 K has been demonstrated on the application heat exchanger, with a 4-meter remote distance ensured by a specifically designed gas circulation flexible line. The design and the performance will be reported in this paper.

  20. Real-Time Closed Loop Modulated Turbine Cooling

    NASA Technical Reports Server (NTRS)

    Shyam, Vikram; Culley, Dennis E.; Eldridge, Jeffrey; Jones, Scott; Woike, Mark; Cuy, Michael

    2014-01-01

    It has been noted by industry that in addition to dramatic variations of temperature over a given blade surface, blade-to-blade variations also exist despite identical design. These variations result from manufacturing variations, uneven wear and deposition over the life of the part as well as limitations in the uniformity of coolant distribution in the baseline cooling design. It is proposed to combine recent advances in optical sensing, actuation, and film cooling concepts to develop a workable active, closed-loop modulated turbine cooling system to improve by 10 to 20 the turbine thermal state over the flight mission, to improve engine life and to dramatically reduce turbine cooling air usage and aircraft fuel burn. A reduction in oxides of nitrogen (NOx) can also be achieved by using the excess coolant to improve mixing in the combustor especially for rotorcraft engines. Recent patents filed by industry and universities relate to modulating endwall cooling using valves. These schemes are complex, add weight and are limited to the endwalls. The novelty of the proposed approach is twofold 1) Fluidic diverters that have no moving parts are used to modulate cooling and can operate under a wide range of conditions and environments. 2) Real-time optical sensing to map the thermal state of the turbine has never been attempted in realistic engine conditions.

  1. Divertor efficiency in ASDEX

    NASA Astrophysics Data System (ADS)

    Engelhardt, W.; Becker, G.; Behringer, K.; Campbell, D.; Eberhagen, A.; Fussmann, G.; Gehre, O.; Gierke, G. V.; Glock, E.; Haas, G.; Huang, M.; Karger, F.; Keilhacker, M.; KlÜber, O.; Kornherr, M.; Lisitano, G.; Mayer, H.-M.; Meisel, D.; Müller, E. R.; Murmann, H.; Niedermeyer, H.; Poschenrieder, W.; Rapp, H.; Schneider, F.; Siller, G.; Steuer, K.-H.; Venus, G.; Vernickel, H.; Wagner, F.

    1982-12-01

    The divertor efficiency in ASDEX is discussed for ohmically heated plasmas. The parameters of the boundary layer both in the torus midplane and the divertor chamber have been measured. The results are reasonably well understood in terms of parallel and perpendicular transport. A high pressure of neutral hydrogen builds up in the divertor chamber and Franck-Condon particles recycle back through the divertor throat. Due to dissociation processes the boundary plasma is effectively cooled before it reaches the neutralizer plates. The shielding property of the boundary layer against impurity influx is comparable to that of a limiter plasma. The transport of iron is numerically simulated for an iron influx produced by sputtering of charge exchange neutrals at the wall. The results are consistent with the measured iron concentration. First results from a comparison of the poloidal divertor with toroidally closed limiters (stainless steel, carbon) are given. Diverted discharges are considerably cleaner and easier to create.

  2. Electron beam facility for divertor target experiments

    SciTech Connect

    Anisimov, A.; Gagen-Torn, V.; Giniyatulin, R.N.

    1994-12-31

    To test different concepts of divertor targets and bumpers an electron beam facility was assembled in Efremov Institute. It consists of a vacuum chamber (3m{sup 3}), vacuum pump, electron beam gun, manipulator to place and remove the samples, water loop and liquid metal loop. The following diagnostics of mock-ups is stipulated: (1) temperature distribution on the mock-up working surface (scanning pyrometer and infra-red imager); (2) temperature distribution over mocked-up thickness in 3 typical cross-sections (thermo-couples); (3) cracking dynamics during thermal cycling (acoustic-emission method), (4) defects in the mock-up before and after tests (ultra-sonic diagnostics, electron and optical microscopes). Carbon-based and beryllium mock-ups are made for experimental feasibility study of water and liquid-metal-cooled divertor/bumper concepts.

  3. Floating Loop System For Cooling Integrated Motors And Inverters Using Hot Liquid Refrigerant

    DOEpatents

    Hsu, John S [Oak Ridge, TN; Ayers, Curtis W [Kingston, TN; Coomer, Chester [Knoxville, TN; Marlino, Laura D [Oak Ridge, TN

    2006-02-07

    A floating loop vehicle component cooling and air-conditioning system having at least one compressor for compressing cool vapor refrigerant into hot vapor refrigerant; at least one condenser for condensing the hot vapor refrigerant into hot liquid refrigerant by exchanging heat with outdoor air; at least one floating loop component cooling device for evaporating the hot liquid refrigerant into hot vapor refrigerant; at least one expansion device for expanding the hot liquid refrigerant into cool liquid refrigerant; at least one air conditioning evaporator for evaporating the cool liquid refrigerant into cool vapor refrigerant by exchanging heat with indoor air; and piping for interconnecting components of the cooling and air conditioning system.

  4. UV Observations of Prominence Activation and Cool Loop Dynamics

    NASA Technical Reports Server (NTRS)

    Kucera, Therese A.; Landi, Enrico

    2006-01-01

    In this paper we investigate the thermal and dynamic properties of dynamic structures in and around a prominence channel observed on the limb on 17 April 2003. Observations were taken with the Solar and Heliospheric Observatory's Solar Ultraviolet Measurements of Emitted Radiation (SOHO/SUMER) in lines formed at temperatures from 80,000 to 1.6 MK. The instrument was pointed to a single location and took a series of 90 s exposures. Two-dimensional context was provided by the Transition Region and Coronal Explorer (TRACE) in the UV and EUV and the Kanzelhohe Solar Observatory in H-alpha. Two dynamic features were studied in depth: an activated prominence and repeated motions in a loop near the prominence. We calculated three-dimensional geometries and trajectories, differential emission measure, and limits on the mass, pressure, average density, and kinetic and thermal energies. These observations provide important tests for models of dynamics in prominences and cool (approx. 10(exp 5) K)loops, which will ultimately lead to a better understanding the mechanism(s) leading to energy and mass flow in these solar features.

  5. Supervisory control of a pilot-scale cooling loop

    SciTech Connect

    Kris Villez; Venkat Venkatasubramanian; Humberto Garcia

    2011-08-01

    We combine a previously developed strategy for Fault Detection and Identification (FDI) with a supervisory controller in closed loop. The combined method is applied to a model of a pilot-scale cooling loop of a nuclear plant, which includes Kalman filters and a model-based predictive controller as part of normal operation. The system has two valves available for flow control meaning that some redundancy is available. The FDI method is based on likelihood ratios for different fault scenarios which in turn are derived from the application of the Kalman filter. A previously introduced extension of the FDI method is used here to enable detection and identification of non-linear faults like stuck valve problems and proper accounting of the time of fault introduction. The supervisory control system is designed so to take different kinds of actions depending on the status of the fault diagnosis task and on the type of identified fault once diagnosis is complete. Some faults, like sensor bias and drift, are parametric in nature and can be adjusted without need for reconfiguration of the regulatory control system. Other faults, like a stuck valve problem, require reconfiguration of the regulatory control system. The whole strategy is demonstrated for several scenarios.

  6. Design and Testing of a Superfluid Liquid Helium CoolingLoop

    SciTech Connect

    Gavin, L.M.; Green, M.A.; Levin, S.M.; Smoot, George F.; Witebsky, C.

    1989-07-24

    This paper describes the design and preliminary testing of a cryogenic cooling loop that uses a thermomechanical pump to circulate superfluid liquid helium. The cooling loop test apparatus is designed to prove forced liquid helium flow concepts that will be used on the Astromag superconducting magnet facility.

  7. The flow-chart loop: temperature, density, and cooling observables supporting nanoflare coronal heating models

    SciTech Connect

    Schmelz, J. T.; Pathak, S.; Dhaliwal, R. S.; Christian, G. M.; Fair, C. B.

    2014-11-10

    We have tested three controversial properties for a target loop observed with the Atmospheric Imaging Assembly: (1) overdense loops; (2) long-lifetime loops; and (3) multithermal loops. Our loop is overdense by a factor of about 10 compared to results expected from steady uniform heating models. If this were the only inconsistency, our loop could still be modeled as a single strand, but the density mismatch would imply that the heating must be impulsive. Moving on to the second observable, however, we find that the loop lifetime is at least an order of magnitude greater than the predicted cooling time. This implies that the loop cannot be composed of a single flux tube, even if the heating were dynamic, and must be multi-stranded. Finally, differential emission measure analysis shows that the cross-field temperature of the target loop is multithermal in the early and middle phases of its lifetime, but effectively isothermal before it fades from view. If these multithermal cooling results are found to be widespread, our results could resolve the original coronal loop controversy of 'isothermal' versus 'multithermal' cross-field temperatures. That is, the cross-field temperature is not always 'multithermal' nor is it always 'isothermal', but might change as the loop cools. We find that the existence and evolution of this loop is consistent with predictions of nanoflare heating.

  8. Divertor detachment

    NASA Astrophysics Data System (ADS)

    Krasheninnikov, Sergei

    2015-11-01

    The heat exhaust is one of the main conceptual issues of magnetic fusion reactor. In a standard operational regime the large heat flux onto divertor target reaches unacceptable level in any foreseeable reactor design. However, about two decades ago so-called ``detached divertor'' regimes were found. They are characterized by reduced power and plasma flux on divertor targets and look as a promising solution for heat exhaust in future reactors. In particular, it is envisioned that ITER will operate in a partly detached divertor regime. However, even though divertor detachment was studied extensively for two decades, still there are some issues requiring a new look. Among them is the compatibility of detached divertor regime with a good core confinement. For example, ELMy H-mode exhibits a very good core confinement, but large ELMs can ``burn through'' detached divertor and release large amounts of energy on the targets. In addition, detached divertor regimes can be subject to thermal instabilities resulting in the MARFE formation, which, potentially, can cause disruption of the discharge. Finally, often inner and outer divertors detach at different plasma conditions, which can lead to core confinement degradation. Here we discuss basic physics of divertor detachment including different mechanisms of power and momentum loss (ionization, impurity and hydrogen radiation loss, ion-neutral collisions, recombination, and their synergistic effects) and evaluate the roles of different plasma processes in the reduction of the plasma flux; detachment stability; and an impact of ELMs on detachment. We also evaluate an impact of different magnetic and divertor geometries on detachment onset, stability, in- out- asymmetry, and tolerance to the ELMs. Supported by the U.S. Department of Energy Office of Science, Office of Fusion Energy Sciences under Award Number DE-DE-FG02-04ER54739 at UCSD.

  9. Closed loop spray cooling apparatus. [for particle accelerator targets

    NASA Technical Reports Server (NTRS)

    Alger, D. L.; Schwab, W. B.; Furman, E. R. (Inventor)

    1978-01-01

    A closed loop apparatus for spraying coolant against the back of a radiation target is described. The coolant was circulated through a closed loop with a bubble of inert gas being maintained around the spray. Mesh material was disposed between the bubble and the surface of the liquid coolant which was below the bubble at a predetermined level. In a second embodiment, no inert gas was used, the bubble consisting of a vapor produced when the coolant was sprayed against the target.

  10. Passive coolers for pre-cooling of JT loops for deep space infrared imaging applications

    NASA Astrophysics Data System (ADS)

    Zhang, Burt; Larson, Melora; Rodriguez, Jose

    2010-09-01

    Infrared instruments (IR) for deep space imaging missions, such as the James Webb Space Telescope (JWST) and Planck, require cryogenic cooling for proper operation of their focal plane arrays (FPA) in far infrared and sub-millimeter wavelength ranges. The FPA is sometimes located meters away from the spacecraft. To meet such remote cooling requirement, a Joule-Thomson (J-T) loop becomes a convenient choice for either direct cooling for the FPA or for serving as a heat sink for a cascade cooling system. The refrigerant lines of the JT loop inevitably suffer parasitic heat leak primarily due to IR backload as they traverse from the spacecraft to the FPA. An actively cooled JT loop using a mechanical pre-cooler located at the spacecraft will experience the highest parasitic heat leak since the lines are cold through the entire length whereas a passively cooled JT loop can utilize a number of radiators to cool the lines down gradually in stages and hence reduce the heat leak. In addition to savings in power and mass, a passive cooler offers consistent and predictable performance with practically no performance degradation in a thermally stable orbit, such as one around the Sun-Earth L2 point. Passive coolers are less popular in low temperature applications when their cooling capacity diminishes rapidly in proportion to T4 until the temperature reaches a point where either the parasitic heat leak becomes so significant or its size becomes so excessive that the passive cooling scheme becomes impractical. Despite the limited capacity, passive cooling may still prove to be a viable alternative to active cooling depending on the operating temperature and heat dissipation rate of the FPA. The current effort aims at evaluating the merit of using passive coolers as an alternative to using a mechanical cooler for pre-cooling of a JT loop for remote IR instrument cooling. A parametric study is conducted to explore the merits of passive cooling of a JT loop in a temperature range

  11. The Quiet Sun Network at Subarcsecond Resolution: VAULT Observations and Radiative Transfer Modeling of Cool Loops

    NASA Astrophysics Data System (ADS)

    Patsourakos, S.; Gouttebroze, P.; Vourlidas, A.

    2007-08-01

    One of the most enigmatic regions of the solar atmosphere is the transition region (TR), corresponding to plasmas with temperatures intermediate of the cool, few thousand K, chromosphere and the hot, few million K, corona. The traditional view is that the TR emission originates from a thin thermal interface in hot coronal structures, connecting their chromosphere with their corona. This paradigm fails badly for cool plasmas (~T<105 K), since it predicts emission orders of magnitude less than what it is observed. It was therefore proposed that the ``missing'' TR emission could originate from tiny, isolated from the hot corona, cool loops at TR temperatures. A major problem in investigating this proposal is the very small sizes of the hypothesized cool loops. Here, we report the first spatially resolved observations of subarcsecond-scale looplike structures seen in the Lyα line made by the Very High Angular Resolution Ultraviolet Telescope (VAULT). The subarcsecond (~0.3") resolution of VAULT allows us to directly view and resolve looplike structures in the quiet Sun network. We compare the observed intensities of these structures with simplified radiative transfer models of cool loops. The reasonable agreement between the models and the observations indicates that an explanation of the observed fine structure in terms of cool loops is plausible.

  12. Computer cooling using a two phase minichannel thermosyphon loop heated from horizontal and vertical sides and cooled from vertical side

    NASA Astrophysics Data System (ADS)

    Bieliński, Henryk; Mikielewicz, Jarosław

    2010-10-01

    In the present paper it is proposed to consider the computer cooling capacity using the thermosyphon loop. A closed thermosyphon loop consists of combined two heaters and a cooler connected to each other by tubes. The first heater may be a CPU processor located on the motherboard of the personal computer. The second heater may be a chip of a graphic card placed perpendicular to the motherboard of personal computer. The cooler can be placed above the heaters on the computer chassis. The thermosyphon cooling system on the use of computer can be modeled using the rectangular thermosyphon loop with minichannels heated at the bottom horizontal side and the bottom vertical side and cooled at the upper vertical side. The riser and a downcomer connect these parts. A one-dimensional model of two-phase flow and heat transfer in a closed thermosyphon loop is based on mass, momentum, and energy balances in the evaporators, rising tube, condenser and the falling tube. The separate two-phase flow model is used in calculations. A numerical investigation for the analysis of the mass flux rate and heat transfer coefficient in the steady state has been accomplished.

  13. The impact of a filament eruption on nearby high-lying cool loops

    SciTech Connect

    Harra, L. K.; Matthews, S. A.; Long, D. M.; Doschek, G. A.; De Pontieu, B.

    2014-09-10

    The first spectroscopic observations of cool Mg II loops above the solar limb observed by NASA's Interface Region Imaging Spectrograph (IRIS) are presented. During the observation period, IRIS is pointed off-limb, allowing the observation of high-lying loops, which reach over 70 Mm in height. Low-lying cool loops were observed by the IRIS slit-jaw camera for the entire four-hour observing window. There is no evidence of a central reversal in the line profiles, and the Mg II h/k ratio is approximately two. The Mg II spectral lines show evidence of complex dynamics in the loops with Doppler velocities reaching ±40 km s{sup –1}. The complex motions seen indicate the presence of multiple threads in the loops and separate blobs. Toward the end of the observing period, a filament eruption occurs that forms the core of a coronal mass ejection. As the filament erupts, it impacts these high-lying loops, temporarily impeding these complex flows, most likely due to compression. This causes the plasma motions in the loops to become blueshifted and then redshifted. The plasma motions are seen before the loops themselves start to oscillate as they reach equilibrium following the impact. The ratio of the Mg h/k lines also increases following the impact of the filament.

  14. Direct observations of plasma upflows and condensation in a catastrophically cooling solar transition region loop

    SciTech Connect

    Orange, N. B.; Chesny, D. L.; Oluseyi, H. M.; Hesterly, K.; Patel, M.; Champey, P.

    2013-12-01

    Minimal observational evidence exists for fast transition region (TR) upflows in the presence of cool loops. Observations of such occurrences challenge notions of standard solar atmospheric heating models as well as their description of bright TR emission. Using the EUV Imaging Spectrometer on board Hinode, we observe fast upflows (v {sub λ} ≤ –10 km s{sup –1}) over multiple TR temperatures (5.8 ≤log T ≤ 6.0) at the footpoint sites of a cool loop (log T ≤ 6.0). Prior to cool loop energizing, asymmetric flows of +5 km s{sup –1} and –60 km s{sup –1} are observed at footpoint sites. These flows, speeds, and patterns occur simultaneously with both magnetic flux cancellation (at the site of upflows only) derived from the Solar Dynamics Observatory's Helioseismic Magnetic Imager's line-of-sight magnetogram images, and a 30% mass influx at coronal heights. The incurred non-equilibrium structure of the cool loop leads to a catastrophic cooling event, with subsequent plasma evaporation indicating that the TR is the heating site. From the magnetic flux evolution, we conclude that magnetic reconnection between the footpoint and background field is responsible for the observed fast TR plasma upflows.

  15. Moving Divertor Plates in a Tokamak

    SciTech Connect

    S.J. Zweben, H. Zhang

    2009-02-12

    Moving divertor plates could help solve some of the problems of the tokamak divertor through mechanical ingenuity rather than plasma physics. These plates would be passively heated on each pass through the tokamak and cooled and reprocessed outside the tokamak. There are many design options using varying plate shapes, orientations, motions, coatings, and compositions.

  16. Thermal Response of the Hybrid Loop-Pool Design for Sodium Cooled Faster Reactors

    SciTech Connect

    Zhang, Hongbin; Zhao, Haihua; Davis, Cliff

    2008-09-01

    An innovative hybrid loop-pool design for the sodium cooled fast reactor (SFR) has been recently proposed with the primary objective of achieving cost reduction and safety enhancement. With the hybrid loop-pool design, closed primary loops are immersed in a secondary buffer tank. This design takes advantage of features from conventional both pool and loop designs to further improve economics and safety. This paper will briefly introduce the hybrid loop-pool design concept and present the calculated thermal responses for unproctected (without reactor scram) loss of forced circulation (ULOF) transients using RELAP5-3D. The analyses examine both the inherent reactivity shutdown capability and decay heat removal performance by passive safety systems.

  17. 158. ARAIII Reactor building (ARA608) Secondary cooling loop and piping ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    158. ARA-III Reactor building (ARA-608) Secondary cooling loop and piping plan. This drawing was selected as a typical example of piping arrangements within reactor building. Aerojet/general 880-area/GCRE-608-P-16. Date: February 1958. INeel index code no. 063-0608-50-013-102641. - Idaho National Engineering Laboratory, Army Reactors Experimental Area, Scoville, Butte County, ID

  18. Feasibility of cogenerated district heating and cooling for North Loop project

    NASA Astrophysics Data System (ADS)

    Porter, R. W.

    1982-03-01

    A thermal-economic analysis was performed in order to determine feasibility of cogeneration with central heating and cooling for Chicago's North Loop Development Project. Heating, cooling and electrical loads were predicted by using energy data according to use and floor area, representative of downtown Chicago. The central facility proposed would supply cogenerated heating for a part of the development's demand and about one half of the cooling demand by means of combined conventional and cogeneration equipment together on the 4-pipe distribution system. Electricity would also be distributed and used to substantially displace purchases. Additional options are also discussed and, if economical, could make implementation more attractive. Four alternatives involving gas turbines and diesels were selected for study and are reported. Energy savings extend over the assumed 25 years of the project and are indexed to inflation and fuel-cost escalation. It would appear that cogeneration could assist economic development of the North Loop Project.

  19. Test Report on ISR Double-Loop, Spray-Cooled Inverter

    SciTech Connect

    Hsu, John S; Coomer, Chester; Campbell, Steven L; Wiles, Randy H; Lowe, Kirk T; McFee, Marshall T

    2007-02-01

    The Isothermal Systems Research, Inc. (ISR) double-loop, two-phase spray cooling system was designed to use 85 C transmission oil to cool a heat exchanger via a second cooling loop. The heat exchanger condenses the working fluid vapor back to liquid inside a sealed enclosure to allow for continuous spray cooling of electronics. In the ORNL tests, 85 C water/ethylene/glycol (WEG), which has better thermal properties than transmission oil, was substituted for the transmission oil. Because the ISR spray-cooling system requires a second cooling loop, the final inverter might be inherently larger than inverters that do not require a second-loop cooling system. The ISR test setup did not include a dc bus capacitor. Because the insulated gate bipolar transistor (IGBT) conduction test indicated that the ISR test setup could not be properly loaded thermally, no switching tests were conducted. Therefore it was not necessary to attach external capacitors outside the test setup. During load situations not exceeding 400A, the WEG inlet temperature was higher than the WEG outlet temperature. This meant that the 85 C WEG heat exchanger was not cooling the inverter and became a thermal load to the inverter. Only when the load was higher than 400A with a higher coolant temperature and the release valve actuated did the WEG heat exchanger start to cool the 2-phase coolant. The inverter relied strongly on the cooling of the huge aluminum enclosure located inside the ventilation chamber. In a hybrid vehicle, the inverter is situated under the hood, where the dependency on cooling provided by the enclosure may become a problem. The IGBT power dissipation with both sides being spray cooled was around 34 W/cm{sup 2} at 403A, with 995W total IGBT loss at 113.5 C projected junction temperature before the release valve was actuated. The current loading could rise higher than 403 A before reaching the 125 C junction temperature limit if the pressure buildup inside the enclosure could be

  20. Floating Refrigerant Loop Based on R-134a Refrigerant Cooling of High-Heat Flux Electronics

    SciTech Connect

    Lowe, K.T.

    2005-10-07

    The Oak Ridge National Laboratory (ORNL) Power Electronics and Electric Machinery Research Center (PEEMRC) have been developing technologies to address the thermal issues associated with hybrid vehicles. Removal of the heat generated from electrical losses in traction motors and their associated power electronics is essential for the reliable operation of motors and power electronics. As part of a larger thermal control project, which includes shrinking inverter size and direct cooling of electronics, ORNL has developed U.S. Patent No. 6,772,603 B2, ''Methods and Apparatus for Thermal Management of Vehicle Systems and Components'' [1], and patent pending, ''Floating Loop System for Cooling Integrated Motors and Inverters Using Hot Liquid Refrigerant'' [2]. The floating-loop system provides a large coefficient of performance (COP) for hybrid-drive component cooling. This loop (based on R-134a) is integrated with a vehicle's existing air-conditioning (AC) condenser, which dissipates waste heat to the ambient air. Because the temperature requirements for cooling of power electronics and electric machines are not as low as that required for passenger compartment air, this adjoining loop can operate on the high-pressure side of the existing AC system. This arrangement also allows the floating loop to run without the need for the compressor and only needs a small pump to move the liquid refrigerant. For the design to be viable, the loop must not adversely affect the existing system. The loop should also provide a high COP, a flat-temperature profile, and low-pressure drop. To date, the floating-loop test prototype has successfully removed 2 kW of heat load in a 9 kW automobile passenger AC system with and without the automotive AC system running. The COP for the tested floating-loop system ranges from 40-45, as compared to a typical AC system COP of about 2-4. The estimated required waste-heat load for future hybrid applications is 5.5 kW and the existing system could be

  1. Redesign of the Extravehicular Mobility Unit Airlock Cooling Loop Recovery Assembly

    NASA Technical Reports Server (NTRS)

    Steele, John; Elms, Theresa; Peyton, Barbara; Rector, Tony; Jennings, Mallory

    2016-01-01

    During EVA (Extravehicular Activity) 23 aboard the ISS (International Space Station) on 07/16/2013 an episode of water in the EMU (Extravehicular Mobility Unit) helmet occurred, necessitating a termination of the EVA (Extravehicular Activity) shortly after it began. The root cause of the failure was determined to be ground-processing short-comings of the ALCLR (Airlock Cooling Loop Recovery) Ion Beds which led to various levels of contaminants being introduced into the Ion Beds before they left the ground. The Ion Beds were thereafter used to scrub the failed EMU cooling water loop on-orbit during routine scrubbing operations. The root cause investigation identified several areas for improvement of the ALCLR Assembly which have since been initiated. Enhanced washing techniques for the ALCLR Ion Bed have been developed and implemented. On-orbit cooling water conductivity and pH analysis capability to allow the astronauts to monitor proper operation of the ALCLR Ion Bed during scrubbing operation is being investigated. A simplified means to acquire on-orbit EMU cooling water samples has been designed. Finally, an inherently cleaner organic adsorbent to replace the current lignite-based activated carbon, and a non-separable replacement for the separable mixed ion exchange resin are undergoing evaluation. These efforts are undertaken to enhance the performance and reduce the risk associated with operations to ensure the long-term health of the EMU cooling water circuit.

  2. Redesign of the Extravehicular Mobility Unit Airlock Cooling Loop Recovery Assembly

    NASA Technical Reports Server (NTRS)

    Steele, John; Elms, Theresa; Peyton, Barbara; Rector, Tony; Jennings, Mallory A.

    2016-01-01

    During EVA (Extravehicular Activity) 23 aboard the ISS (International Space Station) on 07/16/2013 an episode of water in the EMU (Extravehicular Mobility Unit) helmet occurred, necessitating a termination of the EVA (Extravehicular Activity) shortly after it began. The root cause of the failure was determined to be ground-processing short-comings of the ALCLR (Airlock Cooling Loop Recovery) Ion Beds which led to various levels of contaminants being introduced into the Ion Beds before they left the ground. The Ion Beds were thereafter used to scrub the failed EMU cooling water loop on-orbit during routine scrubbing operations. The root cause investigation identified several areas for improvement of the ALCLR Assembly which have since been initiated. Enhanced washing techniques for the ALCLR Ion Bed have been developed and implemented. On-orbit cooling water conductivity and pH analysis capability to allow the astronauts to monitor proper operation of the ALCLR Ion Bed during scrubbing operation is being investigation. A simplified means to acquire on-orbit EMU cooling water samples have been designed. Finally, an inherently cleaner organic adsorbent to replace the current lignite-based activated carbon, and a non-separable replacement for the separable mixed ion exchange resin are undergoing evaluation. These efforts are undertaken to enhance the performance and reduce the risk associated with operations to ensure the long-term health of the EMU cooling water circuit.

  3. Heating and Cooling of Flare Loops in a C5.7 Two-ribbon Flare

    NASA Astrophysics Data System (ADS)

    Pearce, Sarah; Qiu, Jiong

    2016-05-01

    Heating and cooling of flare plasmas can be studied using models constrained by observations. In this work, we analyze and model thermal evolution of a C5.7 two-ribbon flare that occurred on December 26, 2011. The flare was observed by AIA. Two hundred flare loops are identified, which formed sequentially during one hour. Light curves of these flare loops in multiple EUV bands are analyzed to derive the duration and timing of flare emission in each bandpass. These timescales usually reflect cooling of flare plasmas from 10~MK to successively lower temperatures. We then use a zero-dimensional enthalpy-based thermal evolution of loops (EBTEL) model to study flare heating and cooling. Several variations on the EBTEL model are assessed. The first model uses an impulsive heating function inferred from the rapid rise of the foot-point UV emission. Synthetic emission from this model evolves and decays more quickly than the observations, as many models do. Two other variations on the model are analyzed, in an attempt to counter this. In one variation the heating function is a combination of an impulsive pulse followed by an extended tail (i.e., continuous heating). The other model uses reduced thermal conduction to slow the flares evolution. These models are compared with one another and the observations, to evaluate effects of different mechanisms governing the thermal evolution of flare plasmas.

  4. Observational Signatures of Coronal Loop Heating and Cooling Driven by Footpoint Shuffling

    NASA Astrophysics Data System (ADS)

    Dahlburg, R. B.; Einaudi, G.; Taylor, B. D.; Ugarte-Urra, I.; Warren, H. P.; Rappazzo, A. F.; Velli, M.

    2016-01-01

    The evolution of a coronal loop is studied by means of numerical simulations of the fully compressible three-dimensional magnetohydrodynamic equations using the HYPERION code. The footpoints of the loop magnetic field are advected by random motions. As a consequence, the magnetic field in the loop is energized and develops turbulent nonlinear dynamics characterized by the continuous formation and dissipation of field-aligned current sheets: energy is deposited at small scales where heating occurs. Dissipation is nonuniformly distributed so that only a fraction of the coronal mass and volume gets heated at any time. Temperature and density are highly structured at scales that, in the solar corona, remain observationally unresolved: the plasma of our simulated loop is multithermal, where highly dynamical hotter and cooler plasma strands are scattered throughout the loop at sub-observational scales. Numerical simulations of coronal loops of 50,000 km length and axial magnetic field intensities ranging from 0.01 to 0.04 T are presented. To connect these simulations to observations, we use the computed number densities and temperatures to synthesize the intensities expected in emission lines typically observed with the Extreme Ultraviolet Imaging Spectrometer on Hinode. These intensities are used to compute differential emission measure distributions using the Monte Carlo Markov Chain code, which are very similar to those derived from observations of solar active regions. We conclude that coronal heating is found to be strongly intermittent in space and time, with only small portions of the coronal loop being heated: in fact, at any given time, most of the corona is cooling down.

  5. An Innovative Hybrid Loop-Pool Design for Sodium Cooled Fast Reactor

    SciTech Connect

    Haihua Zhao; Hongbin Zhang

    2007-11-01

    The existing sodium cooled fast reactors (SFR) have two types of designs – loop type and pool type. In the loop type design, such as JOYO (Japan) [1] and MONJU (Japan), the primary coolant is circulated through intermediate heat exchangers (IHX) external to the reactor tank. The major advantages of loop design include compactness and easy maintenance. The disadvantage is higher possibility of sodium leakage. In the pool type design such as EBR-II (USA), BN-600M(Russia), Superphénix (France) and European Fast Reactor [2], the reactor core, primary pumps, IHXs and direct reactor auxiliary cooling system (DRACS) heat exchangers (DHX) all are immersed in a pool of sodium coolant within the reactor vessel, making a loss of primary coolant extremely unlikely. However, the pool type design makes primary system large. In the latest ANL’s Advanced Burner Test Reactor (ABTR) design [3], the primary system is configured in a pool-type arrangement. The hot sodium at core outlet temperature in hot pool is separated from the cold sodium at core inlet temperature in cold pool by a single integrated structure called Redan. Redan provides the exchange of the hot sodium from hot pool to cold pool through IHXs. The IHXs were chosen as the traditional tube-shell design. This type of IHXs is large in size and hence large reactor vessel is needed.

  6. Performance analysis of a Cooling System with Natural-Circulation Loop using CO2

    NASA Astrophysics Data System (ADS)

    Okazaki, Takashi

    The experiments and calculations were carried out to evaluate the cycle performance of natural circulation loop with CO2. The cooling capacity of CO2 was compared with that of R410A and the cooling capacity of reverse circulation observed under the supercritical condition was analyzed from a point of view of refrigerant flow direction. The experimental results showed that the cooling capacity of CO2 was approximately4∼13% larger than that of R410A under the two-phase condition at indoor temperature of 30°C. On the other hand, the cooling capacity of CO2 was approximately11% smaller than that of R410A under the supercritical condition at indoor temperature of 50°C. In addition, the cooling capacity with the counter-cross flow heat exchanger was approximately 40% larger than that with the parallel-cross flow heat exchanger under the supercritical condition at indoor temperature of 50°C. These experimental results agreed well with the calculated results.

  7. Actively convected liquid metal divertor

    NASA Astrophysics Data System (ADS)

    Shimada, Michiya; Hirooka, Yoshi

    2014-12-01

    The use of actively convected liquid metals with j × B force is proposed to facilitate heat handling by the divertor, a challenging issue associated with magnetic fusion experiments such as ITER. This issue will be aggravated even more for DEMO and power reactors because the divertor heat load will be significantly higher and yet the use of copper would not be allowed as the heat sink material. Instead, reduced activation ferritic/martensitic steel alloys with heat conductivities substantially lower than that of copper, will be used as the structural materials. The present proposal is to fill the lower part of the vacuum vessel with liquid metals with relatively low melting points and low chemical activities including Ga and Sn. The divertor modules, equipped with electrodes and cooling tubes, are immersed in the liquid metal. The electrode, placed in the middle of the liquid metal, can be biased positively or negatively with respect to the module. The j × B force due to the current between the electrode and the module provides a rotating motion for the liquid metal around the electrodes. The rise in liquid temperature at the separatrix hit point can be maintained at acceptable levels from the operation point of view. As the rotation speed increases, the current in the liquid metal is expected to decrease due to the v × B electromotive force. This rotating motion in the poloidal plane will reduce the divertor heat load significantly. Another important benefit of the convected liquid metal divertor is the fast recovery from unmitigated disruptions. Also, the liquid metal divertor concept eliminates the erosion problem.

  8. Self-driven cooling loop for a large superconducting magnet in space

    NASA Technical Reports Server (NTRS)

    Mord, A. J.; Snyder, H. A.

    1992-01-01

    Pressurized cooling loops in which superfluid helium circulation is driven by the heat being removed have been previously demonstrated in laboratory tests. A simpler and lighter version which eliminates a heat exchanger by mixing the returning fluid directly with the superfluid helium bath was analyzed. A carefully designed flow restriction must be used to prevent boiling in this low-pressure system. A candidate design for Astromag is shown that can keep the magnet below 2.0 K during magnet charging. This gives a greater margin against accidental quench than approaches that allow the coolant to warm above the lambda point. A detailed analysis of one candidate design is presented.

  9. Cryogenic Loop Heat Pipes for the Cooling of Small Particle Detectors at CERN

    NASA Astrophysics Data System (ADS)

    Pereira, H.; Haug, F.; Silva, P.; Wu, J.; Koettig, T.

    2010-04-01

    The loop heat pipe (LHP) is among the most effective heat transfer elements. Its principle is based on a continuous evaporation/condensation process and its passive nature does not require any mechanical devices such as pumps to circulate the cooling agent. Instead a porous wick structure in the evaporator provides the capillary pumping forces to drive the fluid [1]. Cryogenic LHP are investigated as potential candidates for the cooling of future small-scale particle detectors and upgrades of existing ones. A large spectrum of cryogenic temperatures can be covered by choosing appropriate working fluids. For high luminosity upgrades of existing experiments installed at the Large Hadron Collider (LHC) (TOTEM) and planned ones (FP420) [2-3] being in the design phase, radiation-hard solutions are studied with noble gases as working fluids to limit the radiolysis effect on molecules detrimental to the functioning of the LHP. The installation compactness requirement of experiments such as the CAST frame-store CCD detector cooling system impels also the design of a compact shaped LHP [4]. This paper reports on the design and experimental results of a general purpose LHP for temperatures as low as 110 K, for which the performances were measured using a Gifford-McMahon (GM) cooler as the cold source, combination envisaged for the cooling of future particle detectors.

  10. Divertor parameters and divertor operation in ASDEX

    NASA Astrophysics Data System (ADS)

    Fussmann, G.; Ditte, U.; Eckstein, W.; Grave, T.; Keilhacker, M.; McCormick, K.; Murmann, H.; Röhr, H.; Elshaer, M.; Steuer, K.-H.; Szymanski, Z.; Wagner, F.; Becker, G.; Bernhardi, K.; Eberhagen, A.; Gehre, O.; Gernhardt, J.; Gierke, G. V.; Glock, E.; Gruber, O.; Haas, G.; Hesse, M.; Janeschitz, G.; Karger, F.; Kissel, S.; Klüber, O.; Kornherr, M.; Lisitano, G.; Mayer, H. M.; Meisel, D.; Müller, E. R.; Poschenrieder, W.; Ryter, F.; Rapp, H.; Schneider, F.; Siller, G.; Smeulders, P.; Söldner, F.; Speth, E.; Stäbler, A.; Vollmer, O.

    1984-12-01

    Recent measurements of plasma boundary and divertor scrape-off parameters for ohmically and neutral injection heated plasmas are presented. For these data the power flow onto the divertor plates and the sputtering rates at the plates are calculated and compared with separate measurements. The impurity behaviour in front of the plates is also discussed.

  11. RELAP5 Analysis of the Hybrid Loop-Pool Design for Sodium Cooled Fast Reactors

    SciTech Connect

    Hongbin Zhang; Haihua Zhao; Cliff Davis

    2008-06-01

    An innovative hybrid loop-pool design for sodium cooled fast reactors (SFR-Hybrid) has been recently proposed. This design takes advantage of the inherent safety of a pool design and the compactness of a loop design to improve economics and safety of SFRs. In the hybrid loop-pool design, primary loops are formed by connecting the reactor outlet plenum (hot pool), intermediate heat exchangers (IHX), primary pumps and the reactor inlet plenum with pipes. The primary loops are immersed in the cold pool (buffer pool). Passive safety systems -- modular Pool Reactor Auxiliary Cooling Systems (PRACS) – are added to transfer decay heat from the primary system to the buffer pool during loss of forced circulation (LOFC) transients. The primary systems and the buffer pool are thermally coupled by the PRACS, which is composed of PRACS heat exchangers (PHX), fluidic diodes and connecting pipes. Fluidic diodes are simple, passive devices that provide large flow resistance in one direction and small flow resistance in reverse direction. Direct reactor auxiliary cooling system (DRACS) heat exchangers (DHX) are immersed in the cold pool to transfer decay heat to the environment by natural circulation. To prove the design concepts, especially how the passive safety systems behave during transients such as LOFC with scram, a RELAP5-3D model for the hybrid loop-pool design was developed. The simulations were done for both steady-state and transient conditions. This paper presents the details of RELAP5-3D analysis as well as the calculated thermal response during LOFC with scram. The 250 MW thermal power conventional pool type design of GNEP’s Advanced Burner Test Reactor (ABTR) developed by Argonne National Laboratory was used as the reference reactor core and primary loop design. The reactor inlet temperature is 355 °C and the outlet temperature is 510 °C. The core design is the same as that for ABTR. The steady state buffer pool temperature is the same as the reactor inlet

  12. Spectroscopic study of a dark lane and a cool loop in a solar limb active region by Hinode/EIS

    SciTech Connect

    Lee, Kyoung-Sun; Imada, S.; Moon, Y.-J.; Lee, Jin-Yi

    2014-01-10

    We investigated a cool loop and a dark lane over a limb active region on 2007 March 14 using the Hinode/EUV Imaging Spectrometer. The cool loop is clearly seen in the spectral lines formed at the transition region temperature. The dark lane is characterized by an elongated faint structure in the coronal spectral lines and is rooted on a bright point. We examined their electron densities, Doppler velocities, and nonthermal velocities as a function of distance from the limb. We derived electron densities using the density sensitive line pairs of Mg VII, Si X, Fe XII, Fe XIII, and Fe XIV spectra. We also compared the observed density scale heights with the calculated scale heights from each peak formation temperatures of the spectral lines under the hydrostatic equilibrium. We noted that the observed density scale heights of the cool loop are consistent with the calculated heights, with the exception of one observed cooler temperature; we also found that the observed scale heights of the dark lane are much lower than their calculated scale heights. The nonthermal velocity in the cool loop slightly decreases along the loop, while nonthermal velocity in the dark lane sharply falls off with height. Such a decrease in the nonthermal velocity may be explained by wave damping near the solar surface or by turbulence due to magnetic reconnection near the bright point.

  13. Flight Test Results for the HST Orbital Systems Test (HOST) Capillary Pump Loop Cooling System

    NASA Technical Reports Server (NTRS)

    Buchko, M.; Kaylor, M.; Kroliczek, E.; Ottenstein, L.

    1999-01-01

    The Near Infrared Camera and Multi Object Spectrometer (NICMOS) was installed in the Hubble Space Telescope (MST) in February 1997. Shortly thereafter, the instrument experienced a thermal short in its solid nitrogen dewar system which will significantly shorten the instrument's useful life. A reverse Brayton cycle mechanical refrigerator will be installed during the Third Servicing Mission (SM3) to provide cooling for the instrument, and thereby extend its operations. A Capillary Pump Loop (CPL) and radiator system was designed, built and tested to remove up to 500 watts of heat from the mechanical cryocooler and its associated electronics. The HST Orbital Systems Test (HOST) platform was flown on the Space Shuttle Discovery (STS-95) as a flight demonstration of the cryocooler system, CPL control electronics, and the CPL/Radiator. This paper will present the flight test results and thermal performance of the CPL system in detail.

  14. Effect of a Radiation Cooling and Heating Function on Standing Longitudinal Oscillations in Coronal Loops

    NASA Astrophysics Data System (ADS)

    Kumar, S.; Nakariakov, V. M.; Moon, Y.-J.

    2016-06-01

    Standing long-period (with periods longer than several minutes) oscillations in large, hot (with a temperature higher than 3 MK) coronal loops have been observed as the quasi-periodic modulation of the EUV and microwave intensity emission and the Doppler shift of coronal emission lines, and they have been interpreted as standing slow magnetoacoustic (longitudinal) oscillations. Quasi-periodic pulsations of shorter periods, detected in thermal and non-thermal emissions in solar flares could be produced by a similar mechanism. We present theoretical modeling of the standing slow magnetoacoustic mode, showing that this mode of oscillation is highly sensitive to peculiarities of the radiative cooling and heating function. We generalized the theoretical model of standing slow magnetoacoustic oscillations in a hot plasma, including the effects of the radiative losses and accounting for plasma heating. The heating mechanism is not specified and taken empirically to compensate the cooling by radiation and thermal conduction. It is shown that the evolution of the oscillations is described by a generalized Burgers equation. The numerical solution of an initial value problem for the evolutionary equation demonstrates that different dependences of the radiative cooling and plasma heating on the temperature lead to different regimes of the oscillations, including growing, quasi-stationary, and rapidly decaying. Our findings provide a theoretical foundation for probing the coronal heating function and may explain the observations of decayless long-period, quasi-periodic pulsations in flares. The hydrodynamic approach employed in this study should be considered with caution in the modeling of non-thermal emission associated with flares, because it misses potentially important non-hydrodynamic effects.

  15. Recovery Act: Cedarville School District Retrofit of Heating and Cooling Systems with Geothermal Heat Pumps and Ground Source Water Loops

    SciTech Connect

    Jarrell, Mark

    2013-09-30

    Cedarville School District retrofitted the heating and cooling systems in three campus areas (High School, Middle School, and Upper Elementary School) with geothermal heat pumps and ground source water loops, as a demonstration project for the effective implementation of geothermal heat pump systems and other energy efficiency and air quality improvements.

  16. Models for poloidal divertors

    SciTech Connect

    Post, D.E.; Heifetz, D.; Petravic, M.

    1982-07-01

    Recent progress in models for poloidal divertors has both helped to explain current divertor experiments and contributed significantly to design efforts for future large tokamak (INTOR, etc.) divertor systems. These models range in sophistication from zero-dimensional treatments and dimensional analysis to two-dimensional models for plasma and neutral particle transport which include a wide variety of atomic and molecular processes as well as detailed treatments of the plasma-wall interaction. This paper presents a brief review of some of these models, describing the physics and approximations involved in each model. We discuss the wide variety of physics necessary for a comprehensive description of poloidal divertors. To illustrate the progress in models for poloidal divertors, we discuss some of our recent work as typical examples of the kinds of calculations being done.

  17. Air-Cooled Design of a Temperature-Swing Adsorption Compressor for Closed-Loop Air Revitalization Systems

    NASA Technical Reports Server (NTRS)

    Mulloth, Lila M.; Affleck, Dave L.; Rosen, Micha; LeVan, M. Douglas; Wang, Yuan; Cavalcante, Celio L.

    2004-01-01

    The air revitalization system of the International Space Station (ISS) operates in an open loop mode and relies on the resupply of oxygen and other consumables from earth for the life support of astronauts. A compressor is required for delivering the carbon dioxide from a removal assembly to a reduction unit to recover oxygen and thereby closing the air-loop. We have a developed a temperature-swing adsorption compressor (TSAC) for performing these tasks that is energy efficient, quiet, and has no rapidly moving parts. This paper discusses the mechanical design and the results of thermal model validation tests of a TSAC that uses air as the cooling medium.

  18. EUV spectroscopy of cool stars. III. Interpretation of EUVE spectra in terms of quasi-static loops.

    NASA Astrophysics Data System (ADS)

    van den Oord, G. H. J.; Schrijver, C. J.; Camphens, M.; Mewe, R.; Kaastra, J. S.

    1997-10-01

    We discuss the limitations of coronal spectroscopy to derive physical parameters of stellar magnetic loops. We distinguish between the intrinsic non-uniqueness of emitted spectra for models of quasi-static coronal loops, and the supplemental ambiguity introduced by both instrumental effects and spectral line formation. We demonstrate that the spectrum emitted by loops with constant cross-sections is the same for a large range of values of the conductive flux at the base when the apex temperature is fixed. Because it is impossible to estimate the conductive flux at the base from observations, it is also impossible to determine the volume heating rate and the loop length uniquely. For geometrically expanding (tapered) loops, the emitted spectrum depends on the expansion and on the conductive flux at the base, and there is a trade off between them without significant changes in the spectrum. We show that loop length and heating rate can only be derived if the density is known, but that even then a large intrinsic uncertainty remains for these loop parameters. We conclude that there is no unambiguous relationship between loop parameters and emitted spectra: modeling the spectra as the sum of spectra from discrete loops cannot result in a unique determination of coronal structure. Based on spectra observed with the Extreme Ultra Violet Explorer (EUVE) we find that quasi-static loop models allow adequate modeling of stellar coronal spectra. We show that coronal loops on active cool stars must expand with height. The minimum required areal expansion between base and apex is not very large, lying between 2 and 5. For three stars (α Cen, Capella and ξ UMa) the observations suggest the presence of two distinct, dominant loop populations, while for χ^1^ Ori a single population, characterized by a single apex temperature, suffices. The high electron densities (10^12^-10^13^cm^-3^) for coronal components on Capella and ξ UMa require abnormally large heating rates. It is

  19. Solid tungsten Divertor-III for ASDEX Upgrade and contributions to ITER

    NASA Astrophysics Data System (ADS)

    Herrmann, A.; Greuner, H.; Jaksic, N.; Balden, M.; Kallenbach, A.; Krieger, K.; de Marné, P.; Rohde, V.; Scarabosio, A.; Schall, G.; the ASDEX Upgrade Team

    2015-06-01

    ASDEX Upgrade became a full tungsten experiment in 2007 by coating its graphite plasma facing components with tungsten. In 2013 a redesigned solid tungsten divertor, Div-III, was installed and came into operation in 2014. The redesign of the outer divertor geometry provided the opportunity to increase the pumping efficiency in the lower divertor by increasing the gap between divertor and vessel. In parallel, a by-pass was installed into the cryo-pump in the divertor region allowing adapting of the pumping speed to the required edge density. Safe divertor operation and heat removal becomes more and more significant for future fusion devices. This requires developing ‘tools’ for divertor heat load control and to optimize the divertor design. The new divertor manipulator, DIM-II, allows retracting a relevant part of the outer divertor into a target exchange box without venting ASDEX Upgrade. Different front-ends can be installed and exposed to the plasma. At present, front-ends for probe exposition, gas puffing, electrical probes and actively cooled prototype targets are under construction. The installation of solid tungsten, the control of the pumping speed and the flexibility for testing divertor modifications on a weekly base is a unique feature of ASDEX Upgrade and offers together with the extended set of diagnostics the possibility to investigate dedicated questions for a future divertor design.

  20. Spectroscopy of divertor plasmas

    SciTech Connect

    Isler, R.C.

    1995-12-31

    The requirements for divertor spectroscopy are treated with respect to instrumentation and observations on present machines. Emphasis is placed on quantitative measurements.of impurity concentrations from the interpretation of spectral line intensities. The possible influence of non-Maxwellian electron distributions on spectral line excitation in the divertor is discussed. Finally the use of spectroscopy for determining plasma temperature, density, and flows is examined.

  1. Experimental Study of Counterflow Cooling Using a Test Loop to Simulate the Thermal Characteristics of a HTS Cable System

    SciTech Connect

    Demko, Jonathan A

    2012-01-01

    The counterflow cooling configuration is a compact, efficient, and relatively low cost thermal management approach for long-length HTS cable systems. In the counter-flow cooling configuration the coolant flow, typically liquid nitrogen, is initially supplied through the center of the cable turning around at the far end of the cable and returning through the annular space between the cable and the inner cryostat wall, using a single cryostat. The temperature distributions along the cable and the nitrogen flow streams are extremely difficult to measure in an operating HTS cable because of the issues associated with installing thermometers on high voltage components. A 5-meter long test loop has been built that simulates a counter-flow cooled, HTS cable using a heated metal tube to simulate the cable. The test loop contains calibrated thermometers to measure the temperature distribution along the tube and the return liquid nitrogen stream. Measured temperature distributions in the return flow stream and along the tube wall for varying flow rates and heating conditions to simulate a HTS cable are presented and discussed.

  2. THERMAL HYDRAULIC ANALYSIS OF FIRE DIVERTOR

    SciTech Connect

    C.B. bAXI; M.A. ULRICKSON; D.E. DRIMEYER; P. HEITZENROEDER

    2000-10-01

    The Fusion Ignition Research Experiment (FIRE) is being designed as a next step in the US magnetic fusion program. The FIRE tokamak has a major radius of 2 m, a minor radius of 0.525 m, and liquid nitrogen cooled copper coils. The aim is to produce a pulse length of 20 s with a plasma current of 6.6 MA and with alpha dominated heating. The outer divertor and baffle of FIRE are water cooled. The worst thermal condition for the outer divertor and baffle is the baseline D-T operating mode (10 T, 6.6 MA, 20 s) with a plasma exhaust power of 67 MW and a peak heat flux of 20 MW/m{sup 2}. A swirl tape (ST) heat transfer enhancement method is used in the outer divertor cooling channels to increase the heat transfer coefficient and the critical heat flux (CHF). The plasma-facing surface consists of tungsten brush. The finite element (FE) analysis shows that for an inlet water temperature of 30 C, inlet pressure of 1.5 MPa and a flow velocity of 10 m/s, the incident critical heat flux is greater than 30 MW/m{sup 2}. The peak copper temperature is 490 C, peak tungsten temperature is 1560 C, and the pressure drop is less than 0.5 MPa. All these results fulfill the design requirements.

  3. Divertor target for magnetic containment device

    DOEpatents

    Luzzi, Jr., Theodore E.

    1982-01-01

    In a plasma containment device of a type having superconducting field coils for magnetically shaping the plasma into approximately the form of a torus, an improved divertor target for removing impurities from a "scrape off" region of the plasma comprises an array of water cooled swirl tubes onto which the scrape off flux is impinged. Impurities reflected from the divertor target are removed from the target region by a conventional vacuum getter system. The swirl tubes are oriented and spaced apart within the divertor region relative to the incident angle of the scrape off flux to cause only one side of each tube to be exposed to the flux to increase the burnout rating of the target. The divertor target plane is oriented relative to the plane of the path of the scrape off flux such that the maximum heat flux onto a swirl tube is less than the tube design flux. The containment device is used to contain the plasma of a tokamak fusion reactor and is applicable to other long pulse plasma containment systems.

  4. The tungsten divertor experiment at ASDEX Upgrade

    NASA Astrophysics Data System (ADS)

    Neu, R.; Asmussen, K.; Krieger, K.; Thoma, A.; Bosch, H.-S.; Deschka, S.; Dux, R.; Engelhardt, W.; García-Rosales, C.; Gruber, O.; Herrmann, A.; Kallenbach, A.; Kaufmann, M.; Mertens, V.; Ryter, F.; Rohde, V.; Roth, J.; Sokoll, M.; Stäbler, A.; Suttrop, W.; Weinlich, M.; Zohm, H.; Alexander, M.; Becker, G.; Behler, K.; Behringer, K.; Behrisch, R.; Bergmann, A.; Bessenrodt-Weberpals, M.; Brambilla, M.; Brinkschulte, H.; Büchl, K.; Carlson, A.; Chodura, R.; Coster, D.; Cupido, L.; de Blank, H. J.; de Peña Hempel, S.; Drube, R.; Fahrbach, H.-U.; Feist, J.-H.; Feneberg, W.; Fiedler, S.; Franzen, P.; Fuchs, J. C.; Fußmann, G.; Gafert, J.; Gehre, O.; Gernhardt, J.; Haas, G.; Herppich, G.; Herrmann, W.; Hirsch, S.; Hoek, M.; Hoenen, F.; Hofmeister, F.; Hohenöcker, H.; Jacobi, D.; Junker, W.; Kardaun, O.; Kass, T.; Kollotzek, H.; Köppendörfer, W.; Kurzan, B.; Lackner, K.; Lang, P. T.; Lang, R. S.; Laux, M.; Lengyel, L. L.; Leuterer, F.; Manso, M. E.; Maraschek, M.; Mast, K.-F.; McCarthy, P.; Meisel, D.; Merkel, R.; Müller, H. W.; Münich, M.; Murmann, H.; Napiontek, B.; Neu, G.; Neuhauser, J.; Niethammer, M.; Noterdaeme, J.-M.; Pasch, E.; Pautasso, G.; Peeters, A. G.; Pereverzev, G.; Pitcher, C. S.; Poschenrieder, W.; Raupp, G.; Reinmüller, K.; Riedl, R.; Röhr, H.; Salzmann, H.; Sandmann, W.; Schilling, H.-B.; Schlögl, D.; Schneider, H.; Schneider, R.; Schneider, W.; Schramm, G.; Schweinzer, J.; Scott, B. D.; Seidel, U.; Serra, F.; Speth, E.; Silva, A.; Steuer, K.-H.; Stober, J.; Streibl, B.; Treutterer, W.; Troppmann, M.; Tsois, N.; Ulrich, M.; Varela, P.; Verbeek, H.; Verplancke, Ph; Vollmer, O.; Wedler, H.; Wenzel, U.; Wesner, F.; Wolf, R.; Wunderlich, R.; Zasche, D.; Zehetbauer, T.; Zehrfeld, H.-P.

    1996-12-01

    Tungsten-coated tiles, manufactured by plasma spray on graphite, were mounted in the divertor of the ASDEX Upgrade tokamak and cover almost 90% of the surface facing the plasma in the strike zone. Over 600 plasma discharges have been performed to date, around 300 of which were auxiliary heated with heating powers up to 10 MW. The production of tungsten in the divertor was monitored by a W I line at 400.8 nm. In the plasma centre an array of spectral lines at 5 nm emitted by ionization states around W XXX was measured. From the intensity of these lines the W content was derived. Under normal discharge conditions W-concentrations around 0741-3335/38/12A/013/img12 or even lower were found. The influence on the main plasma parameters was found to be negligible. The maximum concentrations observed decrease with increasing heating power. In several low power discharges accumulation of tungsten occurred and the temperature profile was flattened. The concentrations of the intrinsic impurities carbon and oxygen were comparable to the discharges with the graphite divertor. Furthermore, the density and the 0741-3335/38/12A/013/img13 limits remained unchanged and no negative influence on the energy confinement or on the H-mode threshold was found. Discharges with neon radiative cooling showed the same behaviour as in the graphite divertor case.

  5. Divertor design for the Tokamak Physics Experiment

    SciTech Connect

    Hill, D.N.; Braams, B.; Brooks, J.N.

    1994-05-01

    In this paper we discuss the present divertor design for the planned TPX tokamak, which will explore the physics and technology of steady-state (1000s pulses) heat and particle removal in high confinement (2--4{times} L-mode), high beta ({beta}{sub N} {ge} 3) divertor plasmas sustained by non-inductive current drive. The TPX device will operate in the double-null divertor configuration, with actively cooled graphite targets forming a deep (0.5 m) slot at the outer strike point. The peak heat flux on, the highly tilted (74{degrees} from normal) re-entrant (to recycle ions back toward the separatrix) will be in the range of 4--6 MW/m{sup 2} with 18 MW of neutral beams and RF heating power. The combination of active pumping and gas puffing (deuterium plus impurities), along with higher heating power (45 MW maximum) will allow testing of radiative divertor concepts at ITER-like power densities.

  6. An experimental study on the performance of a stainless steel-water loop heat pipe under natural cooling condition

    NASA Astrophysics Data System (ADS)

    Wang, Yiwei; Cen, Jiwen; Jiang, Fangming; Zhu, Xiong

    2014-02-01

    Aiming to improve the thermal characteristics of modern electronics, we experimentally study the performance of a stainless steel/water loop heat pipe (LHP) under natural cooling condition. The LHP heat transfer performance, including start-up performance, temperature oscillation and total thermal resistance at different heat loads and with different incline angles have been investigated systematically. Experimental results show that at an optimal heat load (i.e. 60 W) and with the LHP being inclined 60° to the horizontal plane, the total thermal resistance is lowered to be ˜0.24 K/W, and the temperature of evaporator could be controlled steadily at around 90°C.

  7. The snowflake divertor

    DOE PAGESBeta

    Ryutov, D. D.; Soukhanovskii, V. A.

    2015-11-17

    The snowflake magnetic configuration is characterized by the presence of two closely spaced poloidal field nulls that create a characteristic hexagonal (reminiscent of a snowflake) separatrix structure. The magnetic field properties and the plasma behaviour in the snowflake are determined by the simultaneous action of both nulls, this generating a lot of interesting physics, as well as providing a chance for improving divertor performance. One of the most interesting effects of the snowflake geometry is the heat flux sharing between multiple divertor channels. The authors summarise experimental results obtained with the snowflake configuration on several tokamaks. Wherever possible, relation tomore » the existing theoretical models is described. Divertor concepts utilizing the properties of a snowflake configuration are briefly discussed.« less

  8. The snowflake divertor

    SciTech Connect

    Ryutov, D. D.; Soukhanovskii, V. A.

    2015-11-17

    The snowflake magnetic configuration is characterized by the presence of two closely spaced poloidal field nulls that create a characteristic hexagonal (reminiscent of a snowflake) separatrix structure. The magnetic field properties and the plasma behaviour in the snowflake are determined by the simultaneous action of both nulls, this generating a lot of interesting physics, as well as providing a chance for improving divertor performance. One of the most interesting effects of the snowflake geometry is the heat flux sharing between multiple divertor channels. The authors summarise experimental results obtained with the snowflake configuration on several tokamaks. Wherever possible, relation to the existing theoretical models is described. Divertor concepts utilizing the properties of a snowflake configuration are briefly discussed.

  9. Intermediate Heat Transfer Loop Study for High Temperature Gas-Cooled Reactor

    SciTech Connect

    C. H. Oh; C. Davis; S. Sherman

    2008-08-01

    A number of possible configurations for a system that transfers heat between the nuclear reactor and the hydrogen and/or electrical generation plants were identified. These configurations included both direct and indirect cycles for the production of electricity. Both helium and liquid salts were considered as the working fluid in the intermediate heat transport loop. Methods were developed to perform thermal-hydraulic and cycleefficiency evaluations of the different configurations and coolants. The thermal-hydraulic evaluations estimated the sizes of various components in the intermediate heat transport loop for the different configurations. This paper also includes a portion of stress analyses performed on pipe configurations.

  10. Advanced Space Suit PLSS 2.0 Cooling Loop Evaluation and PLSS 2.5 Recommendations

    NASA Technical Reports Server (NTRS)

    Steele, John; Quinn, Greg; Campbell, Colin; Makinen, Janice; Watts, Carly; Westheimer, David

    2016-01-01

    From 2012 to 2015 The NASA/JSC AdvSS (Advanced Space Suit) PLSS (Portable Life Support Subsystem) team, with support from UTC Aerospace Systems, performed the build-up, packaging and testing of PLSS 2.0. One aspect of that testing was the evaluation of the long-term health of the water cooling circuit and the interfacing components. Periodic and end-of-test water, residue and hardware analyses provided valuable information on the status of the water cooling circuit, and the approaches that would be necessary to enhance water cooling circuit health in the future. The evaluated data has been consolidated, interpreted and woven into an action plan for the maintenance of water cooling circuit health for the planned FY (fiscal year) 2016 through FY 2018 PLSS 2.5 testing. This paper provides an overview of the PLSS 2.0 water cooling circuit findings and the associated steps to be taken in that regard for the PLSS 2.5.

  11. Advanced Space Suit PLSS 2.0 Cooling Loop Evaluation and PLSS 2.5 Recommendations

    NASA Technical Reports Server (NTRS)

    Steele, John; Quinn, Greg; Campbell, Colin; Makinen, Janice; Watts, Carly; Westheimer, Dave

    2016-01-01

    From 2012 to 2015 The NASA/JSC AdvSS (Advanced Space Suit) PLSS (Primary Life Support Subsystem) team, with support from UTC Aerospace Systems, performed the build-up, packaging and testing of PLSS 2.0. A key aspect of that testing was the evaluation of the long-term health of the water cooling circuit and the interfacing components. Intermittent and end-of-test water, residue and hardware analyses provided valuable information on the status of the water cooling circuit, and the approaches that would be necessary to enhance water cooling circuit health in the future. The evaluated data has been consolidated, interpreted and woven into an action plan for the maintenance of water cooling circuit health for the planned FY (fiscal year) 2016 through FY 2018 PLSS 2.5 testing. This paper provides an overview of the PLSS 2.0 water cooling circuit findings and the associated steps to be taken in that regard for the PLSS 2.5 testing.

  12. Influence of magnetic field structure on the conduction cooling of flare loops

    NASA Technical Reports Server (NTRS)

    Antiochos, S. K.; Sturrock, P. A.

    1976-01-01

    A simple model facilitates calculation of the influence of magnetic-field configuration on the conduction cooling rate of a hot post-flare coronal plasma. The magnetic field is taken to be that produced by a line dipole or point dipole at an arbitrary depth below the chromosphere. For the high temperatures (at least 10 million K) produced by flares, the plasma may remain static and isobaric. The influence of the field is such as to increase the heat flux (per unit area) into the chromosphere, but to decrease the total conduction cooling of the flare plasma. This leads to a significant enhancement of the total energy radiated by the flare plasma.

  13. Thermohydraulics in a high-temperature gas-cooled reactor primary loop during early phases of unrestricted core-heatup accidents

    SciTech Connect

    Kroeger, P.G.; Colman, J.; Hsu, C.J.

    1983-01-01

    In High Temperature Gas Cooled Reactor (HTGR) siting considerations, the Unrestricted Core Heatup Accidents (UCHA) are considered as accidents of highest consequence, corresponding to core meltdown accidents in light water reactors. Initiation of such accidents can be, for instance, due to station blackout, resulting in scram and loss of all main loop forced circulation, with none of the core auxiliary cooling system loops being started. The result is a slow but continuing core heatup, extending over days. During the initial phases of such UCHA scenarios, the primary loop remains pressurized, with the system pressure slowly increasing until the relief valve setpoint is reached. The major objectives of the work described here were to determine times to depressurization as well as approximate loop component temperatures up to depressurization.

  14. Floating loop method for cooling integrated motors and inverters using hot liquid refrigerant

    DOEpatents

    Hsu, John S.; Ayers, Curtis W.; Coomer, Chester; Marlino, Laura D.

    2007-03-20

    A method for cooling vehicle components using the vehicle air conditioning system comprising the steps of: tapping the hot liquid refrigerant of said air conditioning system, flooding a heat exchanger in the vehicle component with said hot liquid refrigerant, evaporating said hot liquid refrigerant into hot vapor refrigerant using the heat from said vehicle component, and returning said hot vapor refrigerant to the hot vapor refrigerant line in said vehicle air conditioning system.

  15. Divertor plasma detachment

    NASA Astrophysics Data System (ADS)

    Krasheninnikov, S. I.; Kukushkin, A. S.; Pshenov, A. A.

    2016-05-01

    Regime with the plasma detached from the divertor targets (detached divertor regime) is a natural continuation of the high recycling conditions to higher density and stronger impurity radiation loss. Both the theoretical considerations and experimental data show clearly that the increase of the impurity radiation loss and volumetric plasma recombination causes the rollover of the plasma flux to the target when the density increases, which is the manifestation of detachment. Plasma-neutral friction (neutral viscosity effects), although important for the sustainment of high density/pressure plasma upstream and providing the conditions for efficient recombination and power loss, is not directly involved in the reduction of the plasma flux to the targets. The stability of detachment is also discussed.

  16. The snowflake divertor

    SciTech Connect

    Ryutov, D. D.; Soukhanovskii, V. A.

    2015-11-15

    The snowflake magnetic configuration is characterized by the presence of two closely spaced poloidal field nulls that create a characteristic hexagonal (reminiscent of a snowflake) separatrix structure. The magnetic field properties and the plasma behaviour in the snowflake are determined by the simultaneous action of both nulls, this generating a lot of interesting physics, as well as providing a chance for improving divertor performance. Among potential beneficial effects of this geometry are: increased volume of a low poloidal field around the null, increased connection length, and the heat flux sharing between multiple divertor channels. The authors summarise experimental results obtained with the snowflake configuration on several tokamaks. Wherever possible, relation to the existing theoretical models is described.

  17. One factor of resonant wavelength shift from onewavelength to two-wavelength resonance in loop-tube-type thermoacoustic cooling system

    NASA Astrophysics Data System (ADS)

    Sakamoto, Shin-ichi; Shibata, Kenji; Kitadani, Yuji; Inui, Yoshitaka; Watanabe, Yoshiaki

    2012-05-01

    Results of this study show that the resonant wavelength of the sound generated in a loop-tube-type thermoacoustic cooling system shifts from one-wavelength to two-wavelength resonance during system operation. The effect of the viscous boundary layer upon the resonant wavelength shift is discussed. The viscous boundary layer thickness is always less than the stack channel radius because the loop tube increases the resonance frequency and shifts the resonant wavelength from one-wavelength to two-wavelength resonance, which reduces the influence of viscosity and allows the loop tube to maintain the thermoacoustic self-sustained sound.

  18. Prominence and Cool Loop Energetics Measured in the UV, EUV, and H-alpha

    NASA Technical Reports Server (NTRS)

    Kucera, Therese A.; Landi, E.

    2006-01-01

    We investigate the thermal and dynamic properties of moving features in a prominence jet, a approx. 10(exp 5)K loop near a prominence channel, and an erupting prominence. In order to make measurements of the quickly moving features seen in prominences in the UV we use the SOHO/SUMER spectrograph to take a time series of exposures from a single pointing position, providing a measurement of spectral line properties as a function of time and position along the slit. The lines observed cover a broad range of temperatures from 80,000 - 1.6 million K. These measurements are combined with TRACE movies in transition region and coronal temperature bands and with ground based H-alpha data to obtain more complete information concerning prominence structure and motions. The resulting observations allow us perform DEM analysis and to calculate limits on densities, pressures, and the thermal and kinetic energies of the moving sources.

  19. Modelling of radiative divertor operation towards detachment in experimental advanced superconducting tokamak

    SciTech Connect

    Chen Yiping; Wang, F. Q.; Hu, L. Q.; Guo, H. Y.; Wu, Z. W.; Zhang, X. D.; Wan, B. N.; Li, J. G.; Zha, X. J.

    2013-02-15

    In order to actively control power load on the divertor target plates and study the effect of radiative divertor on plasma parameters in divertor plasmas and heat fluxes to the targets, dedicated experiments with Ar impurity seeding have been performed on experimental advanced superconducting tokamak in typical L-mode discharge with single null divertor configuration, ohmic heating power of 0.5 MW, and lower hybrid wave heating power of 1.0 MW. Ar is puffed into the divertor plasma at the outer target plate near the separatrix strike point with the puffing rate 1.26 Multiplication-Sign 10{sup 20} s{sup -1}. The radiative divertor is formed during the Ar puffing. The SOL/divertor plasma in the L-mode discharge with radiative divertor has been modelled by using SOLPS5.2 code package [V. Rozhansky et al., Nucl. Fusion 49, 025007 (2009)]. The modelling shows the cooling of the divertor plasma due to Ar seeding and is compared with the experimental measurement. The changes of peak electron temperature and heat fluxes at the targets with the shot time from the modelling results are similar to the experimental measurement before and during the Ar impurity seeding, but there is a major difference in time scales when Ar affects the plasma in between experiment and modelling.

  20. Experimental analysis and FEM simulation of loop heat charged with diamond nanofluid for desktop PC cooling

    NASA Astrophysics Data System (ADS)

    Gunnasegaran, P.; Abdullah, M. Z.; Yusoff, M. Z.

    2015-09-01

    This paper discusses the impact of diamond nanofluid on heat transfer characteristics in a Loop Heat Pipe (LHP). In this study, diamond nanoparticles in water with particle mass concentration ranged from 0% to 3% is considered as the operational fluid within the LHP. The experiments are carried out by manufacturing the LHP, in which the setup consists of a water tank with pump, a flat evaporator, condenser installed with two pieces of fans, two transportation lines (vapor and liquid lines), copper pipe sections for attachment of the thermocouples and power supply. The uniqueness of the current experimental setup is the vapor line of LHP which is made of transparent plastic tube to visualize the fluid flow patterns. The experimental results are verified by Finite Element (FE) simulation using a three-dimensional (3D) model based on the heat transfer by conduction where the LHP as a whole is modeled by assuming it as a conducting medium without taking into account the events occurring inside the LHP. The LHP performance is evaluated in terms of transient temperature distribution and total thermal resistance (Rt). The experimental and simulation results are found in good agreement.

  1. Features and Initial Results of the DIII-D Advanced Tokamak Radiative Divertor

    SciTech Connect

    R.C. O'Neill; A.S. Bozek; M.E. Friend; C.B. Baxi; E.E. Reis; M.A. Mahdavi; D.G. Nilson; S.L. Allen; W.P. West

    1999-11-01

    The Radiative Divertor Program of DIII-D is in its final phase with the installation of the cryopump and baffle structure (Phase 1B Divertor) in the upper inner radius of the DIII-D vacuum vessel at the end of this calendar year. This divertor, in conjunction with the Advanced Divertor and the Phase 1A Divertor, located in the lower and upper outer radius of the DIII-D vacuum vessel respectively, provides pumping for density control of the plasma while minimizing the effects on the core confinement. Each divertor consists of a cryobelium cooling ring and a shielded protective structure. The cryo/helium-cooled pumps of all three diverters exhaust helium from the plasma. The protective shielded structure or baffle structure, in the case of the diverters located at the top of the vacuum vessel, provides baffling of neutral charged particles and minimize the flow of impurities back into the core of the plasma. The baffles, which consist of water-cooled panels that allow for the attachment of tiles of various sizes and shapes, house gas puff systems. The intent of the puffing systems is to inject gas in and around the divertor to minimize the heat flux on specific areas on the divertor and its components. The reduction of the heat flux on the divertor minimizes the impurities that are generated from excess heat on divertor components, specifically tiles. Experiments involving the gas puff systems and the divertor structures have shown the heat flux can be spread over a large area of the divertor, reducing the peak heat flux in specific areas. The three diverters also incorporate a variety of diagnostic tools such as halo current monitors, magnetic probes and thermocouples to monitor certain plasma characteristics as well as determine the effectiveness of the cryopumps and baffle configurations. The diverters were designed to optimize pumping performance and to withstand the electromagnetic loads from both halo currents and toroidal induced currents. Incorporated also

  2. Design, R&D and commissioning of EAST tungsten divertor

    NASA Astrophysics Data System (ADS)

    Yao, D. M.; Luo, G. N.; Zhou, Z. B.; Cao, L.; Li, Q.; Wang, W. J.; Li, L.; Qin, S. G.; Shi, Y. L.; Liu, G. H.; Li, J. G.

    2016-02-01

    After commissioning in 2005, the EAST superconducting tokamak had been operated with its water cooled divertors for eight campaigns up to 2012, employing graphite as plasma facing material. With increase in heating power over 20 MW in recent years, the heat flux going to the divertors rises rapidly over 10 MW m-2 for steady state operation. To accommodate the rapid increasing heat load in EAST, the bolting graphite tile divertor must be upgraded. An ITER-like tungsten (W) divertor has been designed and developed; and firstly used for the upper divertor of EAST. The EAST upper W divertor is modular structure with 80 modules in total. Eighty sets of W/Cu plasma-facing components (PFC) with each set consisting of an outer vertical target (OVT), an inner vertical target (IVT) and a DOME, are attached to 80 stainless steel cassette bodies (CB) by pins. The monoblock W/Cu-PFCs have been developed for the strike points of both OVT and IVT, and the flat type W/Cu-PFCs for the DOME and the baffle parts of both OVT and IVT, employing so-called hot isostatic pressing (HIP) technology for tungsten to CuCrZr heat sink bonding, and electron beam welding for CuCrZr to CuCrZr and CuCrZr to other material bonding. Both monoblock and flat type PFC mockups passed high heat flux (HHF) testing by means of electron beam facilities. The 80 divertor modules were installed in EAST in 2014 and results of the first commissioning are presented in this paper.

  3. Asymmetric divertor biasing in MAST

    NASA Astrophysics Data System (ADS)

    Helander, P.; Cohen, R.; Counsell, G. C.; Ryutov, D. D.

    2002-11-01

    Experiments are being carried out on the Mega-Ampere Spherical Tokamak (MAST) where the divertor tiles are electrically biased in a toroidally alternating way. The aim is to induce convective cells in the divertor plasma, broaden the SOL and reduce the divertor heat load. This paper describes the underlying theory and experimental results. Criteria are presented for achieving strong broadening and exciting shear-flow turbulence in the SOL, and properties of the expected turbulence are derived. It is also shown that magnetic shear near the X-point is likely to confine the potential perturbations to the divertor region, leaving the part of the SOL that is in direct contact with the core plasma intact. Preliminary comparison of the theory with MAST data is encouraging: the distortion of the heat deposition pattern, its broadening, and the incremental heat load are qualitatively in agreement; quantitative comparisons are underway.

  4. Electric field divertor plasma pump

    DOEpatents

    Schaffer, M.J.

    1994-10-04

    An electric field plasma pump includes a toroidal ring bias electrode positioned near the divertor strike point of a poloidal divertor of a tokamak, or similar plasma-confining apparatus. For optimum plasma pumping, the separatrix of the poloidal divertor contacts the ring electrode, which then also acts as a divertor plate. A plenum or other duct near the electrode includes an entrance aperture open to receive electrically-driven plasma. The electrode is insulated laterally with insulators, one of which is positioned opposite the electrode at the entrance aperture. An electric field E is established between the ring electrode and a vacuum vessel wall, with the polarity of the bias applied to the electrode being relative to the vessel wall selected such that the resultant electric field E interacts with the magnetic field B already existing in the tokamak to create an E [times] B/B[sup 2] drift velocity that drives plasma into the entrance aperture. The pumped plasma flow into the entrance aperture is insensitive to variations, intentional or otherwise, of the pump and divertor geometry. Pressure buildups in the plenum or duct connected to the entrance aperture in excess of 10 mtorr are achievable. 11 figs.

  5. Electric field divertor plasma pump

    DOEpatents

    Schaffer, Michael J.

    1994-01-01

    An electric field plasma pump includes a toroidal ring bias electrode (56) positioned near the divertor strike point of a poloidal divertor of a tokamak (20), or similar plasma-confining apparatus. For optimum plasma pumping, the separatrix (40) of the poloidal divertor contacts the ring electrode (56), which then also acts as a divertor plate. A plenum (54) or other duct near the electrode (56) includes an entrance aperture open to receive electrically-driven plasma. The electrode (56) is insulated laterally with insulators (63,64), one of which (64) is positioned opposite the electrode at the entrance aperture. An electric field E is established between the ring electrode (56) and a vacuum vessel wall (22), with the polarity of the bias applied to the electrode being relative to the vessel wall selected such that the resultant electric field E interacts with the magnetic field B already existing in the tokamak to create an E.times.B/B.sup.2 drift velocity that drives plasma into the entrance aperture. The pumped plasma flow into the entrance aperture is insensitive to variations, intentional or otherwise, of the pump and divertor geometry. Pressure buildups in the plenum or duct connected to the entrance aperture in excess of 10 mtorr are achievable.

  6. An air-cooled Litz wire coil for measuring the high frequency hysteresis loops of magnetic samples--a useful setup for magnetic hyperthermia applications.

    PubMed

    Connord, V; Mehdaoui, B; Tan, R P; Carrey, J; Respaud, M

    2014-09-01

    A setup for measuring the high-frequency hysteresis loops of magnetic samples is described. An alternating magnetic field in the range 6-100 kHz with amplitude up to 80 mT is produced by a Litz wire coil. The latter is air-cooled using a forced-air approach so no water flow is required to run the setup. High-frequency hysteresis loops are measured using a system of pick-up coils and numerical integration of signals. Reproducible measurements are obtained in the frequency range of 6-56 kHz. Measurement examples on ferrite cylinders and on iron oxide nanoparticle ferrofluids are shown. Comparison with other measurement methods of the hysteresis loop area (complex susceptibility, quasi-static hysteresis loops, and calorific measurements) is provided and shows the coherency of the results obtained with this setup. This setup is well adapted to the magnetic characterization of colloidal solutions of magnetic nanoparticles for magnetic hyperthermia applications. PMID:25273736

  7. An air-cooled Litz wire coil for measuring the high frequency hysteresis loops of magnetic samples—A useful setup for magnetic hyperthermia applications

    NASA Astrophysics Data System (ADS)

    Connord, V.; Mehdaoui, B.; Tan, R. P.; Carrey, J.; Respaud, M.

    2014-09-01

    A setup for measuring the high-frequency hysteresis loops of magnetic samples is described. An alternating magnetic field in the range 6-100 kHz with amplitude up to 80 mT is produced by a Litz wire coil. The latter is air-cooled using a forced-air approach so no water flow is required to run the setup. High-frequency hysteresis loops are measured using a system of pick-up coils and numerical integration of signals. Reproducible measurements are obtained in the frequency range of 6-56 kHz. Measurement examples on ferrite cylinders and on iron oxide nanoparticle ferrofluids are shown. Comparison with other measurement methods of the hysteresis loop area (complex susceptibility, quasi-static hysteresis loops, and calorific measurements) is provided and shows the coherency of the results obtained with this setup. This setup is well adapted to the magnetic characterization of colloidal solutions of magnetic nanoparticles for magnetic hyperthermia applications.

  8. UEDGE Simulation of Triple-X Divertors

    NASA Astrophysics Data System (ADS)

    Wiley, J.; Kotschenreuther, M.; Valanju, P.; Pekker, M.; Rognlien, T.

    2006-04-01

    Novel magnetic divertors with additional X-points downstream from the main plasma X-point have been proposed to overcome reactor heat flux limitations. These divertor designs may allow a fully detached state at the divertor plate - without the poor confinement and disruptive tendencies by avoiding x-point MARFEs found in conventional divertor magnetic geometries. These new configurations are examined using UEDGE for existing machines that are considering experimental implementation of these divertors: PEGASUS, MAST, and EAST(China's new long-pulse, superconducting tokamak) as well as proposed reactor designs.

  9. Recent Progress in the NSTX/NSTX-U Lithium Program and Prospects for Reactor-Relevant Liquid-Lithium Based Divertor Development

    SciTech Connect

    M. Ono, et al.

    2012-10-27

    Li-coated divertor chamber wall. By operating at a lower temperature than the first wall, the LLD can serve to purify the entire reactor chamber, as impurities generally migrate toward lower temperature Li-condensed surfaces. To maintain the LL purity, a closed LL loop system with a modest capacity (e.g., ~ 1 Liter/sec for ~ 1% level "impurities") is envisioned for a steady-state 1 GW-electric class fusion power plant.

  10. Magnetic geometry and physics of advanced divertors: The X-divertor and the snowflake

    SciTech Connect

    Kotschenreuther, Mike; Valanju, Prashant; Covele, Brent; Mahajan, Swadesh

    2013-10-15

    Advanced divertors are magnetic geometries where a second X-point is added in the divertor region to address the serious challenges of burning plasma power exhaust. Invoking physical arguments, numerical work, and detailed model magnetic field analysis, we investigate the magnetic field structure of advanced divertors in the physically relevant region for power exhaust—the scrape-off layer. A primary result of our analysis is the emergence of a physical “metric,” the Divertor Index DI, which quantifies the flux expansion increase as one goes from the main X-point to the strike point. It clearly separates three geometries with distinct consequences for divertor physics—the Standard Divertor (DI = 1), and two advanced geometries—the X-Divertor (XD, DI > 1) and the Snowflake (DI < 1). The XD, therefore, cannot be classified as one variant of the Snowflake. By this measure, recent National Spherical Torus Experiment and DIIID experiments are X-Divertors, not Snowflakes.

  11. Kinetic Modeling of Divertor Plasma

    NASA Astrophysics Data System (ADS)

    Ishiguro, Seiji; Hasegawa, Hiroki; Pianpanit, Theerasarn

    2015-11-01

    Particle-in-Cell (PIC) simulation with the Monte Carlo collisions and the cumulative scattering angle coulomb collision can present kinetic dynamics of divertor plasmas. We are developing two types of PIC codes. The first one is the three dimensional bounded PIC code where three dimensional kinetic dynamics of blob is studied and current flow structures related to sheath formation are unveiled. The second one is the one spatial three velocity space dimensional (1D3V) PIC code with the Monte Carlo collisions where formation of detach plasma is studied. First target of our research is to construct self-consistent full kinetic simulation modeling of the linear divertor simulation experiments. This work is performed with the support and under the auspices of NIFS Collaboration Research program (NIFS15KNSS059, NIFS14KNXN279, and NIFS13KNSS038) and the Research Cooperation Program on Hierarchy and Holism in Natural Science at NINS.

  12. Fabrication and installation of the DIII-D radiative divertor structures

    SciTech Connect

    Hollerbach, M.A.; Smith, J.P.

    1997-11-01

    Phase 1A of the Radiative Divertor Program (RDP) is now installed in the DIII-D tokamak located at General Atomics. This hardware was added to enhance both the Divertor and Advanced Tokamak research elements of the DIII-D program. This installation consists of a divertor baffle enveloping a cryocondensation pump at the upper outer divertor target of DIII-D. The divertor baffle consists of two toroidally continuous Inconel 625 water-cooled rings and a toroidal array of discontinuous radiatively-cooled plates. The water-cooled rings are each comprised of four quadrants, mechanically formed, chem.-milled, and resistance and TIG welded Inconel 625 panels. The supports attaching the panels to the vessel wall are designed to accommodate the differential thermal expansion between the rings and vessel during bake and to react the electromagnetic loads induced during disruptions. They are made from either Inconel 625 or Inconel 718 depending on the stress levels predicted in Finite Element Analysis. Gas seals are designed to limit the leakage from the baffle chamber back to the core plasma to 2,500 {ell}/s and incorporate plasma sprayed alumina to minimize currents flowing through them. The bulk of the water-cooled ring fabrication was performed by a vendor, however, the final machining of penetrations in the conical ring for diagnostic access was performed in-house using a unique machining configuration. This configuration, and the machining of the diagnostic cutouts is described. Graphite tiles were machined from ATJ graphite to form a smooth plasma-facing surface. The installation of all divertor components required only four weeks.

  13. Survivability of dust in tokamaks: Dust transport in the divertor sheath

    SciTech Connect

    Delzanno, Gian Luca; Tang, Xianzhu

    2014-02-15

    The survivability of dust being transported in the magnetized sheath near the divertor plate of a tokamak and its impact on the desired balance of erosion and redeposition for a steady-state reactor are investigated. Two different divertor scenarios are considered. The first is characterized by an energy flux perpendicular to the plate q{sub 0}≃1 MW/m{sup 2} typical of current short-pulse tokamaks. The second has q{sub 0}≃10 MW/m{sup 2} and is relevant to long-pulse machines like ITER or Demonstration Power Plant. It is shown that micrometer dust particles can survive rather easily near the plates of a divertor plasma with q{sub 0}≃1 MW/m{sup 2} because thermal radiation provides adequate cooling for the dust particle. On the other hand, the survivability of micrometer dust particles near the divertor plates is drastically reduced when q{sub 0}≃10 MW/m{sup 2}. Micrometer dust particles redeposit their material non-locally, leading to a net poloidal mass migration across the divertor. Smaller particles (with radius ∼0.1 μm) cannot survive near the divertor and redeposit their material locally. Bigger particle (with radius ∼10 μm) can instead survive partially and move outside the divertor strike points, thus causing a net loss of divertor material to dust accumulation inside the chamber and some non-local redeposition. The implications of these results for ITER are discussed.

  14. The lithium vapor box divertor

    NASA Astrophysics Data System (ADS)

    Goldston, R. J.; Myers, R.; Schwartz, J.

    2016-02-01

    It has long been recognized that volumetric dissipation of the plasma heat flux from a fusion power system is preferable to its localized impingement on a material surface. Volumetric dissipation mitigates both the anticipated very high heat flux and intense particle-induced damage due to sputtering. Recent projections to a tokamak demonstration power plant suggest an immense upstream parallel heat flux, of order 20 GW m-2, implying that fully detached operation may be a requirement for the success of fusion power. Building on pioneering work on the use of lithium by Nagayama et al and by Ono et al as well as earlier work on the gas box divertor by Watkins and Rebut, we present here a concept for a lithium vapor box divertor, in which lithium vapor extracts momentum and energy from a fusion-power-plant divertor plasma, using fully volumetric processes. At the high powers and pressures that are projected this requires a high density of lithium vapor, which must be isolated from the main plasma in order to avoid lithium build-up on the chamber walls or in the plasma. Isolation is achieved through a powerful multi-box differential pumping scheme available only for condensable vapors. The preliminary box-wise calculations are encouraging, but much more work is required to demonstrate the practical viability of this scheme, taking into account at least 2D plasma and vapor flows within and between the vapor boxes and out of the vapor boxes to the main plasma.

  15. Conceptual design of divertor and first wall for DEMO-FNS

    NASA Astrophysics Data System (ADS)

    Sergeev, V. Yu.; Kuteev, B. V.; Bykov, A. S.; Gervash, A. A.; Glazunov, D. A.; Goncharov, P. R.; Dnestrovskij, A. Yu.; Khayrutdinov, R. R.; Klishchenko, A. V.; Lukash, V. E.; Mazul, I. V.; Molchanov, P. A.; Petrov, V. S.; Rozhansky, V. A.; Shpanskiy, Yu. S.; Sivak, A. B.; Skokov, V. G.; Spitsyn, A. V.

    2015-11-01

    Key issues of design of the divertor and the first wall of DEMO-FNS are presented. A double null closed magnetic configuration was chosen with long external legs and V-shaped corners. The divertor employs a cassette design similar to that of ITER. Water-cooled first wall of the tokamak is made of Be tiles and CuCrZr-stainless steel shells. Lithium injection and circulation technologies are foreseen for protection of plasma facing components. Simulations of thermal loads onto the first wall and divertor plates suggest a possibility to distribute heat loads making them less than 10 MW m-2. Evaluations of sputtering and evaporation of plasma-facing materials suggest that lithium may protect the first wall. To prevent Be erosion at the outer divertor plates either the full detached divertor operation or arrangement of the renewal lithium flow on targets should be implemented. Test bed experiments on the Tsefey-M facility with the first wall mockup coated by Ве tiles and cooled by water are presented. The temperature of the surface of tiles reached 280-300 °С at 5 MW m-2 and 600-650 °С at 10.5 MW m-2. The mockup successfully withstood 1000 cycles with the lower thermal loading and 100 cycles with higher thermal loading.

  16. Recent progress in the NSTX/NSTX-U lithium programme and prospects for reactor-relevant liquid-lithium based divertor development

    NASA Astrophysics Data System (ADS)

    Ono, M.; Jaworski, M. A.; Kaita, R.; Kugel, H. W.; Ahn, J.-W.; Allain, J. P.; Bell, M. G.; Bell, R. E.; Clayton, D. J.; Canik, J. M.; Ding, S.; Gerhardt, S.; Gray, T. K.; Guttenfelder, W.; Hirooka, Y.; Kallman, J.; Kaye, S.; Kumar, D.; LeBlanc, B. P.; Maingi, R.; Mansfield, D. K.; McLean, A.; Menard, J.; Mueller, D.; Nygren, R.; Paul, S.; Podesta, M.; Raman, R.; Ren, Y.; Sabbagh, S.; Scotti, F.; Skinner, C. H.; Soukhanovskii, V.; Surla, V.; Taylor, C. N.; Timberlake, J.; Zakharov, L. E.; the NSTX Research Team

    2013-11-01

    Developing a reactor-compatible divertor has been identified as a particularly challenging technology problem for magnetic confinement fusion. Application of lithium (Li) in NSTX resulted in improved H-mode confinement, H-mode power threshold reduction, and other plasma performance benefits. During the 2010 NSTX campaign, application of a relatively modest amount of Li (300 mg prior to the discharge) resulted in a ˜50% reduction in heat load on the liquid lithium divertor (LLD) attributable to enhanced divertor bolometric radiation. These promising Li results in NSTX and related modelling calculations motivated the radiative LLD concept proposed here. Li is evaporated from the liquid lithium (LL) coated divertor strike-point surface due to the intense heat flux. The evaporated Li is readily ionized by the plasma due to its low ionization energy, and the poor Li particle confinement near the divertor plate enables ionized Li ions to radiate strongly, resulting in a significant reduction in the divertor heat flux. This radiative process has the desired effect of spreading the localized divertor heat load to the rest of the divertor chamber wall surfaces, facilitating the divertor heat removal. The LL coating of divertor surfaces can also provide a ‘sacrificial’ protective layer to protect the substrate solid material from transient high heat flux such as the ones caused by the edge localized modes. By operating at lower temperature than the first wall, the LL covered large divertor chamber wall surfaces can serve as an effective particle pump for the entire reactor chamber, as impurities generally migrate towards lower temperature LL divertor surfaces. To maintain the LL purity, a closed LL loop system with a modest circulating capacity (e.g., ˜1 l s-1 for ˜1% level ‘impurities’) is envisioned for a steady-state 1 GW-electric class fusion power plant.

  17. Finding the Cold Needle in a Warm Haystack: Infrared Imaging Applied to Locating Cryo-cooled Crystals in Loops

    NASA Technical Reports Server (NTRS)

    Snell, Edward; vanderWoerd, Mark

    2003-01-01

    Thermally imaging the cryocooling processes of crystals has been demonstrated showing the progression of a cold wave through a crystal from the face closest to the origin of the coldstream ending at the point furthest away. During these studies large volume crystals were clearly distinguished from the loop holding them. Large volume crystals, used for neutron studies, were chosen deliberately to enhance the imaging. The different infrared transmission and reflectance properties of the crystal in comparison to the cryo-protectant are thought to be the parameter that produces the contrast making the crystal visible. As an application of the technology to locating crystals, more small crystals of lysozyme and a bFGF/dna complex were cryo-protected and imaged in large loops. The crystals were clearly distinguished from the vitrified solution. In the case of the bFGF/dna complex the illumination had to be carefully manipulated to enable the crystal to be seen in the visible spectrum. These preliminary results will be presented along with advantages and disadvantages of the technique and a discussion of how it might be applied.

  18. Performance characteristics of the DIII-D advanced divertor cryopump

    SciTech Connect

    Menon, M.M.; Maingi, R.; Wade, M.R.; Baxi, C.B.; Campbell, G.L.; Holtrop, K.L.; Hyatt, A.W.; Laughon, G.J.; Makariou, C.C.; Mahdavi, M.A.; Reis, E.E.; Schaffer, M.J.; Schaubel, K.M.; Scoville, J.T.; Smith, J.P.; Stambaugh, R.D.

    1993-10-01

    A cryocondensation pump, cooled by forced flow of two-phase helium, has been installed for particle exhaust from the divertor region of the DIII-D tokamak. The Inconel pumping surface is of coaxial geometry, 25.4 mm in outer diameter and 11.65 m in length. Because of the tokamak environment, the pump is designed to perform under relatively high pulsed heat loads (300 Wm{sup {minus}2}). Results of measurements made on the pumping characteristics for D{sub 2}, H{sub 2}, and Ar are discussed.

  19. Effect of Divertor Shaping on Divertor Plasma Behavior on DIII-D

    NASA Astrophysics Data System (ADS)

    Petrie, T. W.; Leonard, A. W.; Luce, T. C.; Mahdavi, M. A.; Holcomb, C. T.; Fenstermacher, M. E.; Hill, D. N.; Lasnier, C. J.; Watkins, J. G.; Moyer, R. A.; Stangeby, P. C.

    2012-10-01

    Recent experiments examined the dependence of divertor density (nTAR), temperature (TTAR), and heat flux at the outer divertor separatrix target on changes in the divertor separatrix geometry. The responses of nTAR and TTAR to changes in the parallel connection length in the scrape-off layer (SOL) (L||) are consistent with the predictions of the Two Point Model (TPM). However, nTAR and TTAR display a more complex response to changes in the radial location of the outer divertor strike point (RTAR) than expected based on the TPM. SOLPS transport analysis indicates that small differences in divertor geometry can change neutral trapping sufficient to explain differences between experiment and TPM predictions. The response of the core and divertor plasmas to changes in L|| and RTAR, under both radiating and non-radiating divertor conditions, will be shown.

  20. Development of a Method for Local Electron Temperature and Density Measurements in the Divertor of the JET Tokamak

    NASA Technical Reports Server (NTRS)

    Jupen, C.; Meigs, A.; Bhatia, A. K.; Brezinsek, S.; OMullane, M.

    2004-01-01

    Plasma volume recombination in the divertor, a process in which charged particles recombine to neutral atoms, contributes to plasma detachment and hence cooling at the divertor target region. Detachment has been observed at JET and other tokamaks and is known to occur at low electron temperatures (T(sub e)<1 eV) and at high electron density (n(sub e)>10(exp 20)/m(exp 3)). The ability to measure such low temperatures is therefore of interest for modelling the divertor. In present work we report development of a new spectroscopic technique for investigation of local electron density (n(sub e)) and temperature (T,) in the outer divertor at JET.

  1. ADX: A high Power Density, Advanced RF-Driven Divertor Test Tokamak for PMI studies

    NASA Astrophysics Data System (ADS)

    Whyte, Dennis; ADX Team

    2015-11-01

    The MIT PSFC and collaborators are proposing an advanced divertor experiment, ADX; a divertor test tokamak dedicated to address critical gaps in plasma-material interactions (PMI) science, and the world fusion research program, on the pathway to FNSF/DEMO. Basic ADX design features are motivated and discussed. In order to assess the widest range of advanced divertor concepts, a large fraction (>50%) of the toroidal field volume is purpose-built with innovative magnetic topology control and flexibility for assessing different surfaces, including liquids. ADX features high B-field (>6 Tesla) and high global power density (P/S ~ 1.5 MW/m2) in order to access the full range of parallel heat flux and divertor plasma pressures foreseen for reactors, while simultaneously assessing the effect of highly dissipative divertors on core plasma/pedestal. Various options for efficiently achieving high field are being assessed including the use of Alcator technology (cryogenic cooled copper) and high-temperature superconductors. The experimental platform would also explore advanced lower hybrid current drive and ion-cyclotron range of frequency actuators located at the high-field side; a location which is predicted to greatly reduce the PMI effects on the launcher while minimally perturbing the core plasma. The synergistic effects of high-field launchers with high total B on current and flow drive can thus be studied in reactor-relevant boundary plasmas.

  2. Dust divertor for a tokamak fusion reactor

    SciTech Connect

    Tang, X Z; Delzanno, G L

    2009-01-01

    Micron-size tungsten particulates find equilibrium position in the magnetized plasma sheath in the normal direction of the divertor surface, but are convected poloidally and toroidally by the sonic-ion-flow drag parallel to the divertor surface. The natural circulation of dust particles in the magnetized plasma sheath can be used to set up a flowing dust shield that absorbs and exhausts most of the tokamak heat flux to the divertor. The size of the particulates and the choice of materials offer substantial room for optimization.

  3. Benchmarking of thermal hydraulic loop models for Lead-Alloy Cooled Advanced Nuclear Energy System (LACANES), phase-I: Isothermal steady state forced convection

    NASA Astrophysics Data System (ADS)

    Cho, Jae Hyun; Batta, A.; Casamassima, V.; Cheng, X.; Choi, Yong Joon; Hwang, Il Soon; Lim, Jun; Meloni, P.; Nitti, F. S.; Dedul, V.; Kuznetsov, V.; Komlev, O.; Jaeger, W.; Sedov, A.; Kim, Ji Hak; Puspitarini, D.

    2011-08-01

    As highly promising coolant for new generation nuclear reactors, liquid Lead-Bismuth Eutectic has been extensively worldwide investigated. With high expectation about this advanced coolant, a multi-national systematic study on LBE was proposed in 2007, which covers benchmarking of thermal hydraulic prediction models for Lead-Alloy Cooled Advanced Nuclear Energy System (LACANES). This international collaboration has been organized by OECD/NEA, and nine organizations - ENEA, ERSE, GIDROPRESS, IAEA, IPPE, KIT/IKET, KIT/INR, NUTRECK, and RRC KI - contribute their efforts to LACANES benchmarking. To produce experimental data for LACANES benchmarking, thermal-hydraulic tests were conducted by using a 12-m tall LBE integral test facility, named as Heavy Eutectic liquid metal loop for integral test of Operability and Safety of PEACER (HELIOS) which has been constructed in 2005 at the Seoul National University in the Republic of Korea. LACANES benchmark campaigns consist of a forced convection (phase-I) and a natural circulation (phase-II). In the forced convection case, the predictions of pressure losses based on handbook correlations and that obtained by Computational Fluid Dynamics code simulation were compared with the measured data for various components of the HELIOS test facility. Based on comparative analyses of the predictions and the measured data, recommendations for the prediction methods of a pressure loss in LACANES were obtained. In this paper, results for the forced convection case (phase-I) of LACANES benchmarking are described.

  4. Stochasticity about a poloidal divertor separatrix

    SciTech Connect

    Skinner, D.A.; Osborne, T.H.; Prager, S.C.; Park, W.

    1986-10-01

    The stochasticization of the magnetic separatrix due to the presence of a helical perturbation in a poloidal divertor tokamak is illustrated by a numerical computation which traces magnetic field lines.

  5. Stochasticity about a poloidal divertor separatrix

    SciTech Connect

    Skinner, D.A.; Osborne, T.H.; Prager, S.C.; Park, W.

    1987-04-01

    The stochasticization of the magnetic separatrix caused by the presence of a helical perturbation in a poloidal divertor tokamak is illustrated by a numerical computation that traces magnetic field lines.

  6. High flux expansion divertor studies in NSTX

    SciTech Connect

    Soukhanovskii, V A; Maingi, R; Bell, R E; Gates, D A; Kaita, R; Kugel, H W; LeBlanc, B P; Maqueda, R; Menard, J E; Mueller, D; Paul, S F; Raman, R; Roquemore, A L

    2009-06-29

    Projections for high-performance H-mode scenarios in spherical torus (ST)-based devices assume low electron collisionality for increased efficiency of the neutral beam current drive. At lower collisionality (lower density), the mitigation techniques based on induced divertor volumetric power and momentum losses may not be capable of reducing heat and material erosion to acceptable levels in a compact ST divertor. Divertor geometry can also be used to reduce high peak heat and particle fluxes by flaring a scrape-off layer (SOL) flux tube at the divertor plate, and by optimizing the angle at which the flux tube intersects the divertor plate, or reduce heat flow to the divertor by increasing the length of the flux tube. The recently proposed advanced divertor concepts [1, 2] take advantage of these geometry effects. In a high triangularity ST plasma configuration, the magnetic flux expansion at the divertor strike point (SP) is inherently high, leading to a reduction of heat and particle fluxes and a facilitated access to the outer SP detachment, as has been demonstrated recently in NSTX [3]. The natural synergy of the highly-shaped high-performance ST plasmas with beneficial divertor properties motivated a further systematic study of the high flux expansion divertor. The National Spherical Torus Experiment (NSTX) is a mid-sized device with the aspect ratio A = 1.3-1.5 [4]. In NSTX, the graphite tile divertor has an open horizontal plate geometry. The divertor magnetic configuration geometry was systematically changed in an experiment by either (1) changing the distance between the lower divertor X-point and the divertor plate (X-point height h{sub X}), or by (2) keeping the X-point height constant and increasing the outer SP radius. An initial analysis of the former experiment is presented below. Since in the divertor the poloidal field B{sub {theta}} strength is proportional to h{sub X}, the X-point height variation changed the divertor plasma wetted area due to

  7. Upgrade of Langmuir probe diagnostic in ITER-like tungsten mono-block divertor on experimental advanced superconducting tokamak.

    PubMed

    Xu, J C; Wang, L; Xu, G S; Luo, G N; Yao, D M; Li, Q; Cao, L; Chen, L; Zhang, W; Liu, S C; Wang, H Q; Jia, M N; Feng, W; Deng, G Z; Hu, L Q; Wan, B N; Li, J; Sun, Y W; Guo, H Y

    2016-08-01

    In order to withstand rapid increase in particle and power impact onto the divertor and demonstrate the feasibility of the ITER design under long pulse operation, the upper divertor of the EAST tokamak has been upgraded to actively water-cooled, ITER-like tungsten mono-block structure since the 2014 campaign, which is the first attempt for ITER on the tokamak devices. Therefore, a new divertor Langmuir probe diagnostic system (DivLP) was designed and successfully upgraded on the tungsten divertor to obtain the plasma parameters in the divertor region such as electron temperature, electron density, particle and heat fluxes. More specifically, two identical triple probe arrays have been installed at two ports of different toroidal positions (112.5-deg separated toroidally), which can provide fundamental data to study the toroidal asymmetry of divertor power deposition and related 3-dimension (3D) physics, as induced by resonant magnetic perturbations, lower hybrid wave, and so on. The shape of graphite tip and fixed structure of the probe are designed according to the structure of the upper tungsten divertor. The ceramic support, small graphite tip, and proper connector installed make it possible to be successfully installed in the very narrow interval between the cassette body and tungsten mono-block, i.e., 13.5 mm. It was demonstrated during the 2014 and 2015 commissioning campaigns that the newly upgraded divertor Langmuir probe diagnostic system is successful. Representative experimental data are given and discussed for the DivLP measurements, then proving its availability and reliability. PMID:27587120

  8. Upgrade of Langmuir probe diagnostic in ITER-like tungsten mono-block divertor on experimental advanced superconducting tokamak

    NASA Astrophysics Data System (ADS)

    Xu, J. C.; Wang, L.; Xu, G. S.; Luo, G. N.; Yao, D. M.; Li, Q.; Cao, L.; Chen, L.; Zhang, W.; Liu, S. C.; Wang, H. Q.; Jia, M. N.; Feng, W.; Deng, G. Z.; Hu, L. Q.; Wan, B. N.; Li, J.; Sun, Y. W.; Guo, H. Y.

    2016-08-01

    In order to withstand rapid increase in particle and power impact onto the divertor and demonstrate the feasibility of the ITER design under long pulse operation, the upper divertor of the EAST tokamak has been upgraded to actively water-cooled, ITER-like tungsten mono-block structure since the 2014 campaign, which is the first attempt for ITER on the tokamak devices. Therefore, a new divertor Langmuir probe diagnostic system (DivLP) was designed and successfully upgraded on the tungsten divertor to obtain the plasma parameters in the divertor region such as electron temperature, electron density, particle and heat fluxes. More specifically, two identical triple probe arrays have been installed at two ports of different toroidal positions (112.5-deg separated toroidally), which can provide fundamental data to study the toroidal asymmetry of divertor power deposition and related 3-dimension (3D) physics, as induced by resonant magnetic perturbations, lower hybrid wave, and so on. The shape of graphite tip and fixed structure of the probe are designed according to the structure of the upper tungsten divertor. The ceramic support, small graphite tip, and proper connector installed make it possible to be successfully installed in the very narrow interval between the cassette body and tungsten mono-block, i.e., 13.5 mm. It was demonstrated during the 2014 and 2015 commissioning campaigns that the newly upgraded divertor Langmuir probe diagnostic system is successful. Representative experimental data are given and discussed for the DivLP measurements, then proving its availability and reliability.

  9. Snowflake divertor configuration studies for NSTX-Upgrade

    SciTech Connect

    Soukhanovskii, V A

    2011-11-12

    Snowflake divertor experiments in NSTX provide basis for PMI development toward NSTX-Upgrade. Snowflake configuration formation was followed by radiative detachment. Significant reduction of steady-state divertor heat flux observed in snowflake divertor. Impulsive heat loads due to Type I ELMs are partially mitigated in snowflake divertor. Magnetic control of snowflake divertor configuration is being developed. Plasma material interface development is critical for NSTX-U success. Four divertor coils should enable flexibility in boundary shaping and control in NSTX-U. Snowflake divertor experiments in NSTX provide good basis for PMI development in NSTX-Upgrade. FY 2009-2010 snowflake divertor experiments in NSTX: (1) Helped understand control of magnetic properties; (2) Core H-mode confinement unchanged; (3) Core and edge carbon concentration reduced; and (4) Divertor heat flux significantly reduced - (a) Steady-state reduction due to geometry and radiative detachment, (b) Encouraging results for transient heat flux handling, (c) Combined with impurity-seeded radiative divertor. Outlook for snowflake divertor in NSTX-Upgrade: (1) 2D fluid modeling of snowflake divertor properties scaling - (a) Edge and divertor transport, radiation, detachment threshold, (b) Compatibility with cryo-pump and lithium conditioning; (2) Magnetic control development; and (3) PFC development - PFC alignment and PFC material choice.

  10. A "Snowflake" Divertor and its Properties

    SciTech Connect

    Ryutov, D

    2007-06-21

    Handling the power and particle exhaust in fusion reactors based on tokamaks is a challenging problem [1,2]. To bring the energy flux to the divertor plates to an acceptable level (< 10 MW/m2), it is desirable to significantly increase poloidal flux expansion in the divertor area. Some recent ideas include that of a so-called X divertor [3] and a 'snowflake' divertor [4]. We use an acronym SF to designate the latter. In this paper we concentrate on the SF divertor. The general idea behind this configuration is that, by a proper selection of divertor (poloidal field) coils, one can make the null point of the second, not of the first order as in the standard divertor. The separatrix in the vicinity of the X point then acquires a characteristic hexapole structure (Fig. 1), reminiscent of a snowflake, whence the name. The fact that the field has a second-order null, leads to a significant increase of the flux expansion. It was noted in Ref. [4] that the SF configuration is topologically unstable: if the current in the divertor coils is somewhat higher than the one that provides the SF configuration, it becomes a single-null X-point configuration. Conversely, if the coil current becomes somewhat lower, there appear two separate X-points. To solve this problem, one can operate the divertor at the current by roughly 5% higher than the value needed to create the second-order null. Then, configuration becomes robust enough and the shape of the separatrix does not change significantly if the coil current varies by 2-3%. At the same time, the flux expansion still remained by a factor of {approx}3 larger compared to a 'canonical' divertor. Following Ref. [4], we call this configuration a 'SF-plus' configuration. Specific examples in Ref. [4] were given for simple magnetic geometries The aim of this paper is to demonstrate that the SF concept will also work for a strongly shaped plasma. The other set of issues considered in the present paper relates to the possible presence of

  11. Impurity-induced divertor plasma oscillations

    DOE PAGESBeta

    Smirnov, R. D.; Kukushkin, A. S.; Krasheninnikov, S. I.; Pigarov, A. Yu.; Rognlien, T. D.

    2016-01-07

    Two different oscillatory plasma regimes induced by seeding the plasma with high- and low-Z impurities are found for ITER-like divertor plasmas, using computer modeling with the DUSTT/UEDGE and SOLPS4.3 plasma-impurity transport codes. The oscillations are characterized by significant variations of the impurity-radiated power and of the peak heat load on the divertor targets. Qualitative analysis of the divertor plasma oscillations reveals different mechanisms driving the oscillations in the cases of high- and low-Z impurity seeding. The oscillations caused by the high-Z impurities are excited near the X-point by an impurity-related instability of the radiation-condensation type, accompanied by parallel impurity ionmore » transport affected by the thermal and plasma friction forces. The driving mechanism of the oscillations induced by the low-Z impurities is related to the cross-field transport of the impurity atoms, causing alteration between the high and low plasma temperature regimes in the plasma recycling region near the divertor targets. As a result, the implications of the impurity-induced plasma oscillations for divertor operation in the next generation tokamaks are also discussed.« less

  12. Impurity-induced divertor plasma oscillations

    NASA Astrophysics Data System (ADS)

    Smirnov, R. D.; Kukushkin, A. S.; Krasheninnikov, S. I.; Pigarov, A. Yu.; Rognlien, T. D.

    2016-01-01

    Two different oscillatory plasma regimes induced by seeding the plasma with high- and low-Z impurities are found for ITER-like divertor plasmas, using computer modeling with the DUSTT/UEDGE and SOLPS4.3 plasma-impurity transport codes. The oscillations are characterized by significant variations of the impurity-radiated power and of the peak heat load on the divertor targets. Qualitative analysis of the divertor plasma oscillations reveals different mechanisms driving the oscillations in the cases of high- and low-Z impurity seeding. The oscillations caused by the high-Z impurities are excited near the X-point by an impurity-related instability of the radiation-condensation type, accompanied by parallel impurity ion transport affected by the thermal and plasma friction forces. The driving mechanism of the oscillations induced by the low-Z impurities is related to the cross-field transport of the impurity atoms, causing alteration between the high and low plasma temperature regimes in the plasma recycling region near the divertor targets. The implications of the impurity-induced plasma oscillations for divertor operation in the next generation tokamaks are also discussed.

  13. Detecting divertor damage during steady state operation of Wendelstein 7-X from thermographic measurements

    NASA Astrophysics Data System (ADS)

    Rodatos, A.; Greuner, H.; Jakubowski, M. W.; Boscary, J.; Wurden, G. A.; Pedersen, T. S.; König, R.

    2016-02-01

    Wendelstein 7-X (W7-X) aims to demonstrate the reactor capability of the stellarator concept, by creating plasmas with pulse lengths of up to 30 min at a heating power of up to 10 MW. The divertor plasma facing components will see convective steady state heat flux densities of up to 10 MW/m2. These high heat flux target elements are actively cooled and are covered with carbon fibre reinforced carbon (CFC) as plasma facing material. The CFC is bonded to the CuCrZr cooling structure. Over the life time of the experiment this interface may weaken and cracks can occur, greatly reducing the heat conduction between the CFC tile and the cooling structure. Therefore, there is not only the need to monitor the divertor to prevent damage by overheating but also the need to detect these fatigue failures of the interface. A method is presented for an early detection of fatigue failures of the interface layer, solely by using the information delivered by the IR-cameras monitoring the divertor. This was developed and validated through experiments made with high heat flux target elements prior to installation in W7-X.

  14. Impact of divertor geometry on radiative divertor performance in JET H-mode plasmas

    NASA Astrophysics Data System (ADS)

    Jaervinen, A. E.; Brezinsek, S.; Giroud, C.; Groth, M.; Guillemaut, C.; Belo, P.; Brix, M.; Corrigan, G.; Drewelow, P.; Harting, D.; Huber, A.; Lawson, K. D.; Lipschultz, B.; Maggi, C. F.; Matthews, G. F.; Meigs, A. G.; Moulton, D.; Stamp, M. F.; Wiesen, S.; Contributors, JET

    2016-04-01

    Radiative divertor operation in JET high confinement mode plasmas with the ITER-like wall has been experimentally investigated and simulated with EDGE2D-EIRENE in horizontal and vertical low field side (LFS) divertor configurations. The simulations show that the LFS divertor heat fluxes are reduced with N2-injection in similar fashion in both configurations, qualitatively consistent with experimental observations. The simulations show no substantial difference between the two configurations in the reduction of the peak LFS heat flux as a function of divertor radiation, nitrogen concentration, or pedestal Zeff. Consistently, experiments show similar divertor radiation and nitrogen injection levels for similar LFS peak heat flux reduction in both configurations. Nevertheless, the LFS strike point is predicted to detach at 20% lower separatrix density in the vertical than in the horizontal configuration. However, since the peak LFS heat flux in partial detachment in the vertical configurations is shifted towards the far scrape-off layer (SOL), the simulations predict no benefit in the reduction of LFS peak heat flux for a given upstream density in the vertical configuration relative to a horizontal one. A factor of 2 reduction of deuterium ionization source inside the separatrix is observed in the simulations when changing to the vertical configuration. The simulations capture the experimentally observed particle and heat flux reduction at the LFS divertor plate in both configurations, when adjusting the impurity injection rate to reproduce the measured divertor radiation. However, the divertor D α -emissions are underestimated by a factor of 2-5, indicating a short-fall in radiation by the fuel species. In the vertical configuration, detachment is experimentally measured and predicted to start next to the strike point, extending towards the far SOL with increasing degree of detachment. In contrast, in the horizontal configuration, the entire divertor particle flux

  15. Designing divertor targets for uniform power load

    NASA Astrophysics Data System (ADS)

    Dekeyser, W.; Reiter, D.; Baelmans, M.

    2015-08-01

    Divertor design for next step fusion reactors heavily relies on 2D edge plasma modeling with codes as e.g. B2-EIRENE. While these codes are typically used in a design-by-analysis approach, in previous work we have shown that divertor design can alternatively be posed as a mathematical optimization problem, and solved very efficiently using adjoint methods adapted from computational aerodynamics. This approach has been applied successfully to divertor target shape design for more uniform power load. In this paper, the concept is further extended to include all contributions to the target power load, with particular focus on radiation. In a simplified test problem, we show the potential benefits of fully including the radiation load in the design cycle as compared to only assessing this load in a post-processing step.

  16. Characteristics of divertor detachment for ITER conditions

    NASA Astrophysics Data System (ADS)

    Kukushkin, A. S.; Pacher, H. D.; Pitts, R. A.

    2015-08-01

    The relative role of particle balance vs. momentum balance in the phenomenon of divertor plasma detachment in tokamaks is re-assessed. Ion removal from the plasma flow by volumetric recombination and/or cross-field transport is identified as the key element in the formation of the rollover of the ion saturation current on the targets, whereas "momentum removal" (friction) is responsible for maintaining high plasma pressure upstream. The deterioration of neutral particle confinement in the divertor as particle throughput increases is the primary cause of the solution collapse typically seen when deep detachment is modelled for present day experiments.

  17. High-heat-flux testing of helium-cooled heat exchangers for fusion applications

    SciTech Connect

    Youchison, D.L.; Izenson, M.G.; Baxi, C.B.; Rosenfeld, J.H.

    1996-07-01

    High-heat-flux experiments on three types of helium-cooled divertor mock-ups were performed on the 30-kW electron beam test system and its associated helium flow loop at Sandia National Laboratories. A dispersion-strengthened copper alloy (DSCu) was used in the manufacture of all the mock-ups. The first heat exchanger provides for enhanced heat transfer at relatively low flow rates and much reduced pumping requirements. The Creare sample was tested to a maximum absorbed heat flux of 5.8 MW/m{sup 2}. The second used low pressure drops and high mass flow rates to achieve good heat removal. The GA specimen was tested to a maximum absorbed heat flux of 9 MW/m{sup 2} while maintaining a surface temperature below 400{degree}C. A second experiment resulted in a maximum absorbed heat flux of 34 MW/m{sup 2} and surface temperatures near 533{degree}C. The third specimen was a DSCu, axial flow, helium-cooled divertor mock-up filled with a porous metal wick which effectively increases the available heat transfer area. Low mass flow and high pressure drop operation at 4.0 MPa were characteristic of this divertor module. It survived a maximum absorbed heat flux of 16 MW/m{sup 2} and reached a surface temperature of 740{degree}C. Thermacore also manufactured a follow-on, dual channel porous metal-type heat exchanger, which survived a maximum absorbed heat flux of 14 MW/m{sup 2} and reached a maximum surface temperature of 690{degree}C. 11refs., 20 figs., 3 tabs.

  18. Predictions for Non-Solenoidal Startup in Pegasus with Lower Divertor Helicity Injectors

    NASA Astrophysics Data System (ADS)

    Perry, J. M.; Barr, J. L.; Bongard, M. W.; Fonck, R. J.; Lewicki, B. T.

    2014-10-01

    Non-solenoidal startup in Pegasus has focused on using arrays of local helicity injectors situated on the outboard midplane to leverage PF induction. In contrast, injector assemblies located in the lower divertor region can provide improved performance. Higher toroidal field at the injector increases the helicity injection rate, providing a higher effective loop voltage. Poloidal flux expansion in the divertor region will increase the Taylor relaxation current limit. Radial position control requirements are lessened, as plasma expansion naturally couples to injectors in the divertor region. Advances in cathode design and plasma-facing guard rings allow operation at bias voltages over 1.5 kV, three times higher than previously available. This results in increased effective loop voltage and reduced impurity generation. Operation of helicity injectors in the high field side elevates the current requirements for relaxation to a tokamak-like state, but these are met through the improved injector design and increased control over the poloidal field structure via the addition of new coil sets. These advances, combined with the relocation of the injectors to the divertor region, will allow access to the operational regime where helicity injection current drive, rather the poloidal induction, dominates the discharge--a prerequisite for scaling to larger devices. Initial estimates indicate that plasma currents of 0.25-0.30 MA are attainable at full toroidal field with 4 injectors of 2 cm2 each and 8 kA total injected current. Work supported by US DOE Grant DE-FG02-96ER54375.

  19. Heat Load on Divertors in NCSX

    NASA Astrophysics Data System (ADS)

    Kaiser, T. B.; Hill, D. N.; Maingi, R.; Monticello, D.; Zarnstorff, M.; Grossman, A.

    2006-10-01

    We have continued our study[1-3] of the effect of divertors in NCSX, using magnetic field data generated by both the PIES and VMEC/MFBE equilibrium codes. Results for comparable equilibria from the two codes agree to within statistical uncertainty. We follow field lines from a surface just outside and conformal with the LCMS until they strike a divertor plate or the first wall, or exceed 1000m in length, with effects of particle scattering mimicked by field-line diffusion. Current candidate divertor designs efficiently collect field lines, allowing fewer than 0.1% to reach the wall. The sensitivity of localized power deposition, assumed to be proportional to the density of field- line strike-points, to adjustments in the divertor configuration is under investigation.1. T.B. Kaiser, et al, Bull. Am. Phys. Soc., 48, paper RP1-20, 2003.2. T.B. Kaiser, et al, Bull. Am. Phys. Soc., 49, paper PP1-73, 2004.3. R. Maingi, et al, EPS Conf. Rome, Italy, paper P5.116, 2006.

  20. An X-point ergodic divertor

    SciTech Connect

    Chu, M.S.; Jensen, T.H.; La Haye, R.J.; Taylor, T.S.; Evans, T.E.

    1991-10-01

    A new ergodic divertor is proposed. It utilizes a system of external (n = 3) coils arranged to generate overlapping magnetic islands in the edge region of a diverted tokamak and connect the randomized field lines to the external (cold) divertor plate. The novel feature in the configuration is the placement of the external coils close to the X-point. A realistic design of the external coil set is studied by using the field line tracing method for a low aspect ratio (A {approx equal} 3) tokamak. Two types of effects are observed. First, by placing the coils close to the X-point, where the poloidal magnetic field is weak and the rational surfaces are closely packed only a moderate amount of current in the external coils is needed to ergodize the edge region. This ergodized edge enhances the edge transport in the X-point region and leads to the potential of edge profile control and the avoidance of edge localized modes (ELMs). Furthermore, the trajectories of the field lines close to the X-point are modified by the external coil set, causing the hit points on the external divertor plates to be randomized and spread out in the major radius direction. A time-dependent modulation of the currents in the external (n = 3) coils can potentially spread the heat flux more uniformly on the divertor plate avoiding high concentration of the heat flux. 10 refs., 9 figs.

  1. Divertor Coil Design and Implementation on Pegasus

    NASA Astrophysics Data System (ADS)

    Shriwise, P. C.; Bongard, M. W.; Cole, J. A.; Fonck, R. J.; Kujak-Ford, B. A.; Lewicki, B. T.; Winz, G. R.

    2012-10-01

    An upgraded divertor coil system is being commissioned on the Pegasus Toroidal Experiment in conjunction with power system upgrades in order to achieve higher β plasmas, reduce impurities, and possibly achieve H-mode operation. Design points for the divertor coil locations and estimates of their necessary current ratings were found using predictive equilibrium modeling based upon a 300 kA target plasma. This modeling represented existing Pegasus coil locations and current drive limits. The resultant design calls for 125 kA-turns from the divertor system to support the creation of a double null magnetic topology in plasmas with Ip<=300 kA. Initial experiments using this system will employ 900 V IGBT power supply modules to provide IDIV<=4 kA. The resulting 20 kA-turn capability of the existing divertor coil will be augmented by a new coil providing additional A-turns in series. Induced vessel wall current modeling indicates the time response of a 28 turn augmentation coil remains fast compared to the poloidal field penetration rate through the vessel. First results operating the augmented system are shown.

  2. Recent results from tokamak divertor plasma measurements

    SciTech Connect

    Allen, S.L.

    1996-05-01

    New diagnostics have been developed to address key divertor physics questions, including: target plate heat flux reduction by radiation, basic edge transport issues, and plasma wall interactions (PWI) such as erosion. A system of diagnostics measures the target plate heat flux (imaging IR thermography) and particle flux (probes, pressure and Penning gauges, and visible emission arrays). Recently, T{sub e},n{sub e}, and P{sub e} (electron pressure) have been measured in 2-D with divertor Thomson Scattering. During radiative divertor operation T{sub e} is less than 2 eV, indicating that new atomic processes are important. Langmuir probes measure higher T{sub e} in some cases. In addition, the measured P{sub e} near the separatrix at the target plate is lower than the midplane pressure, implying radial momentum transport. Bolometer arrays, inverted with reconstruction algorithms, provide the 2-D core and divertor radiation profiles. Spectroscopic measurements identify the radiating species and provide information on impurity transport; both absolute chordal measurements and tomographic reconstructions of images are used. Either intrinsic carbon or an inert species (e.g., injected Ne) are usually observed, and absolute particle inventories are obtained. Computer codes are both benchmarked with the experimental data and provide important consistency checks. Several techniques are used to measure fundamental plasma transport and fluctuations, including probes and reflectometry. PWI issues are studied with in-situ coupons and insertable samples (DiMES). Representative divertor results from DIII-D with references to results on other tokamaks will be presented.

  3. Observation of Non-Maxwellian Electron Distributions in th e NSTX Divertor

    SciTech Connect

    M.A. Jaworski, et. al.

    2013-03-07

    The scrape-off layer plasma at the tokamak region is characterized by open field lines and often contains large variations in plasma properties along these field-lines. Proper characterization of local plasma conditions is critical to assessing plasma-material interaction processes occuring at the target. Langmuir probes are frequently employed in tokamak divertors but are challenging to interpretation. A kinetic interpretation for Langmuir probes in NSTX has yielded non-Maxwellian electron distributions in the divertor characterized by cool bulk populations and energetic tail populations with temperatures of 2-4 times the bulk. Spectroscopic analysis and modeling confirms the bulk plasma temperature and density which can only be obtained with the kinetic interpretation

  4. Regulative Loops, Step Loops and Task Loops

    ERIC Educational Resources Information Center

    VanLehn, Kurt

    2016-01-01

    This commentary suggests a generalization of the conception of the behavior of tutoring systems, which the target article characterized as having an outer loop that was executed once per task and an inner loop that was executed once per step of the task. A more general conception sees these two loops as instances of regulative loops, which…

  5. Refrigerant directly cooled capacitors

    DOEpatents

    Hsu, John S.; Seiber, Larry E.; Marlino, Laura D.; Ayers, Curtis W.

    2007-09-11

    The invention is a direct contact refrigerant cooling system using a refrigerant floating loop having a refrigerant and refrigeration devices. The cooling system has at least one hermetic container disposed in the refrigerant floating loop. The hermetic container has at least one electronic component selected from the group consisting of capacitors, power electronic switches and gating signal module. The refrigerant is in direct contact with the electronic component.

  6. Design and operation of a novel divertor cryopumping system in Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Labombard, B.; Beck, B.; Bosco, J.; Childs, R.; Gwinn, D.; Irby, J.; Leccacorvi, R.; Marazita, S.; Mucic, N.; Pierson, S.; Rokhman, Y.; Titus, P.; Vieira, R.; Zaks, J.; Zhukovsky, A.

    2007-11-01

    C-Mod's recently installed upper-divertor cryopump is unique among the world's tokamaks, employing an array of gas-pumping slots that penetrate the upper divertor target. This geometry enables the use of a single toroidal loop of liquid helium, operating in an efficient heat transfer regime with low or no helium flow. A system pumping speed of 9,600 l/sec for D2 gas has been achieved, matching that of a full-scale prototype system. Neutral pressures in the pumping slots during upper-null plasmas (USN) are found to meet or exceed pressures in the lower divertor's private flux region during lower-null (LSN) -- evidence that the pumping-slot geometry is performing as intended. Very high steady-state pumping throughputs (exceeding ˜140 torr-l/s) have been demonstrated in USN. Reliable and efficient operation of the pump has been established, synchronized with the C-Mod shot cycle and consuming 60 to 90 liters of liquid helium during a full day of operation.

  7. Performance of the INTOR poloidal divertor

    SciTech Connect

    Post, D.E.; Petravic, M.; Schmidt, J.A.; Heifetz, D.

    1981-10-01

    The next generation of large tokamak experiments is expected to have large particle and heat outfluxes (approx. 10/sup 23/ particles/sec and 80 MW). These outfluxes must be controlled to provide adequate pumping of the helium ash and to minimize the sputtering erosion of the vacuum vessel walls, limiters, and neutralizer plates. A poloidal divertor design to solve these problems for INTOR has been done using a two-dimensional code which models the plasma as a fluid and solves equations for the flow of particles, momentum and energy, and calculates the neutral gas transport with Monte-Carlo techniques. These calculations show that there is a regime of operation where the density in the divertor is high and the temperature is low, thus easing the heat load and erosion problems. The neutral pressure at the plate is high, resulting in high gas throughputs, with modest pumping speeds.

  8. NSTX Plasma Response to Lithium Coated Divertor

    SciTech Connect

    H.W. Kugel, M.G. Bell, J.P. Allain, R.E. Bell, S. Ding, S.P. Gerhardt, M.A. Jaworski, R. Kaita, J. Kallman, S.M. Kaye, B.P. LeBlanc, R. Maingi, R. Majeski, R. Maqueda, D.K. Mansfield, D. Mueller, R. Nygren, S.F. Paul, R. Raman, A.L. Roquemore, S.A. Sabbagh, H. Schneider, C.H. Skinner, V.A. Soukhanovskii, C.N. Taylor, J.R. Timberlak, W.R. Wampler, L.E. Zakharov, S.J. Zweben, and the NSTX Research Team

    2011-01-21

    NSTX experiments have explored lithium evaporated on a graphite divertor and other plasma facing components in both L- and H- mode confinement regimes heated by high-power neutral beams. Improvements in plasma performance have followed these lithium depositions, including a reduction and eventual elimination of the HeGDC time between discharges, reduced edge neutral density, reduced plasma density, particularly in the edge and the SOL, increased pedestal electron and ion temperature, improved energy confinement and the suppression of ELMs in the H-mode. However, with improvements in confinement and suppression of ELMs, there was a significant secular increase in the effective ion charge Zeff and the radiated power in H-mode plasmas as a result of increases in the carbon and medium-Z metallic impurities. Lithium itself remained at a very low level in the plasma core, <0.1%. Initial results are reported from operation with a Liquid Lithium Divertor (LLD) recently installed.

  9. Modeling detachment physics in the NSTX snowflake divertor

    NASA Astrophysics Data System (ADS)

    Meier, E. T.; Soukhanovskii, V. A.; Bell, R. E.; Diallo, A.; Kaita, R.; LeBlanc, B. P.; McLean, A. G.; Podestà, M.; Rognlien, T. D.; Scotti, F.

    2015-08-01

    The snowflake divertor is a proposed technique for coping with the tokamak power exhaust problem in next-step experiments and eventually reactors, where extreme power fluxes to material surfaces represent a leading technological and physics challenge. In lithium-conditioned National Spherical Torus Experiment (NSTX) discharges, application of the snowflake divertor typically induced partial outer divertor detachment and severalfold heat flux reduction. UEDGE is used to analyze and compare conventional and snowflake divertor configurations in NSTX. Matching experimental upstream profiles and divertor measurements in the snowflake requires target recycling of 0.97 vs. 0.91 in the conventional case, implying partial saturation of the lithium-based pumping mechanism. Density scans are performed to analyze the mechanisms that facilitate detachment in the snowflake, revealing that increased divertor volume provides most of the parallel heat flux reduction. Also, neutral gas power loss is magnified by the increased wetted area in the snowflake, and plays a key role in generating volumetric recombination.

  10. Flute mode fluctuations in the divertor mirror cell

    SciTech Connect

    Katanuma, I.; Yagi, K.; Nakashima, Y.; Ichimura, M.; Imai, T.

    2010-03-15

    The computer code by reduced magnetohydrodynamic equations were made which can simulate the flute interchange modes (similar to the Rayleigh-Taylor instability) and the instability associated with the presence of nonuniform plasma flows (similar to the Kelvin-Helmholtz instability). This code is applied to a model divertor and the GAMMA10 [M. Inutake et al., Phys. Rev. Lett. 55, 939 (1985)] with divertor in order to investigate the flute modes in these divertor cells. The linear growth rate of the flute instability determined by the nonlocal linear analysis agrees with that in the linear phase of the simulations. There is a stable nonlinear steady state in both divertor cells, but the nonlinear steady state is different between the model divertor and the GAMMA10 with divertor.

  11. Divertor and scoop limiter experiments on PDX

    SciTech Connect

    McGuire, K.; Beiersdorfer, P.; Bell, M.; Bol, K.; Boyd, D.; Buchenauer, D.; Budny, R.; Cavallo, A.; Couture, P.; Crowley, T.

    1985-01-01

    Routine operation in the enhanced energy confinement (or H-mode) regime during neutral beam injection was achieved by modifying the PDX divertor hardware to inhibit the influx of neutral gas from the divertor region to the main plasma chamber. A particle scoop limiter has been studied as a mechanical means of controlling particles at the plasma edge, and neutral beam heated discharges with this limiter show similar confinement times (normalized to tau/sub E//I/sub p/) to average H-mode plasmas. Two new instabilities are observed near the plasma edge in PDX during H-mode operation. The first, a quasicoherent fluctuation, occurred in bursts at well-defined frequencies (..delta omega../..omega.. less than or equal to 0.1) in the range 50 to 180 kHz, and had no obvious effects on confinement. The second instability, the edge relaxation phenomena (ERP), did cause deterioration in the global confinement time. The ERP's are characterized by sharp spikes in the divertor plasma density, H/sub ..cap alpha../ emission, and on the x-ray signals they appear as sawtoothlike relaxations at the plasma edge with an inversion radius near the separatrix. Attempts to obtain high ..beta../sub T/ in the H-mode discharges were hampered by a deterioration in the H-mode confinement and major disruptions which limited the achievable ..beta../sub T/. A study of the stability of both the limiter L-mode and divertor H-mode discharges close to the theoretical ..beta.. boundary, showed that the major disruptions observed there are sometimes caused by a fast growing m/n = 1/1 mode with no observable external precursor oscillations.

  12. JET divertor coils, manufacture, assembly and testing

    NASA Astrophysics Data System (ADS)

    Dolgetta, N.; Bertolini, E.; D'Urzo, C.; Last, J. R.; Laurenti, A.; Presle, P.; Sannazzaro, G.; Tait, J.; Tesini, A.

    1994-07-01

    Four coils have been built and installed in the JET vacuum vessel to produce divertor plasmas. The coils are copper with glass epoxy insulation and are enclosed in vacuum tight Inconel cases. At the coil contractor's factory, the coil parts were manufactured and process techniques qualified. In the JET vacuum vessel the conductor bars were brazed to form the coils, which were inserted in the casings and impregnated and cured with epoxy resin.

  13. Constrained ripple optimization of Tokamak bundle divertors

    SciTech Connect

    Hively, L.M.; Rome, J.A.; Lynch, V.E.; Lyon, J.F.; Fowler, R.H.; Peng, Y-K.M.; Dory, R.A.

    1983-02-01

    Magnetic field ripple from a tokamak bundle divertor is localized to a small toroidal sector and must be treated differently from the usual (distributed) toroidal field (TF) coil ripple. Generally, in a tokamak with an unoptimized divertor design, all of the banana-trapped fast ions are quickly lost due to banana drift diffusion or to trapping between the 1/R variation in absolute value vector B ..xi.. B and local field maxima due to the divertor. A computer code has been written to optimize automatically on-axis ripple subject to these constraints, while varying up to nine design parameters. Optimum configurations have low on-axis ripple (<0.2%) so that, now, most banana-trapped fast ions are confined. Only those ions with banana tips near the outside region (absolute value theta < or equal to 45/sup 0/) are lost. However, because finite-sized TF coils have not been used in this study, the flux bundle is not expanded.

  14. ADX - Advanced Divertor and RF Tokamak Experiment

    NASA Astrophysics Data System (ADS)

    Greenwald, Martin; Labombard, Brian; Bonoli, Paul; Irby, Jim; Terry, Jim; Wallace, Greg; Vieira, Rui; Whyte, Dennis; Wolfe, Steve; Wukitch, Steve; Marmar, Earl

    2015-11-01

    The Advanced Divertor and RF Tokamak Experiment (ADX) is a design concept for a compact high-field tokamak that would address boundary plasma and plasma-material interaction physics challenges whose solution is critical for the viability of magnetic fusion energy. This device would have two crucial missions. First, it would serve as a Divertor Test Tokamak, developing divertor geometries, materials and operational scenarios that could meet the stringent requirements imposed in a fusion power plant. By operating at high field, ADX would address this problem at a level of power loading and other plasma conditions that are essentially identical to those expected in a future reactor. Secondly, ADX would investigate the physics and engineering of high-field-side launch of RF waves for current drive and heating. Efficient current drive is an essential element for achieving steady-state in a practical, power producing fusion device and high-field launch offers the prospect of higher efficiency, better control of the current profile and survivability of the launching structures. ADX would carry out this research in integrated scenarios that simultaneously demonstrate the required boundary regimes consistent with efficient current drive and core performance.

  15. Divertor bypass in the Alcator C-Mod tokamak

    NASA Astrophysics Data System (ADS)

    Pitcher, C. S.; LaBombard, B.; Danforth, R.; Pina, W.; Silveira, M.; Parkin, B.

    2001-01-01

    The Alcator C-Mod divertor bypass has for the first time allowed in situ variations to the mechanical baffle design in a tokamak. The design utilizes small coils which interact with the ambient magnetic field inside the vessel to provide the torque required to control small flaps of a Venetian blind geometry. Plasma physics experiments with the bypass have revealed the importance of the divertor baffling to maintain high divertor gas pressures. These experiments have also indicated that the divertor baffling has only a limited effect on the main chamber pressure in C-Mod.

  16. Divertor Heat Flux Mitigation in the National Spherical Torus Experiment

    SciTech Connect

    Soukhanovskii, V A; Maingi, R; Gates, D A; Menard, J E; Paul, S F; Raman, R; Roquemore, A L; Bell, M G; Bell, R E; Boedo, J A; Bush, C E; Kaita, R; Kugel, H W; LeBlanc, B P; Mueller, D

    2008-08-04

    Steady-state handling of divertor heat flux is a critical issue for both ITER and spherical torus-based devices with compact high power density divertors. Significant reduction of heat flux to the divertor plate has been achieved simultaneously with favorable core and pedestal confinement and stability properties in a highly-shaped lower single null configuration in the National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 2000] using high magnetic flux expansion at the divertor strike point and the radiative divertor technique. A partial detachment of the outer strike point was achieved with divertor deuterium injection leading to peak flux reduction from 4-6 MW m{sup -2} to 0.5-2 MW m{sup -2} in small-ELM 0.8-1.0 MA, 4-6 MW neutral beam injection-heated H-mode discharges. A self-consistent picture of outer strike point partial detachment was evident from divertor heat flux profiles and recombination, particle flux and neutral pressure measurements. Analytic scrape-off layer parallel transport models were used for interpretation of NSTX detachment experiments. The modeling showed that the observed peak heat flux reduction and detachment are possible with high radiated power and momentum loss fractions, achievable with divertor gas injection, and nearly impossible to achieve with main electron density, divertor neutral density or recombination increases alone.

  17. Divertor heat flux mitigation in the National Spherical Torus Experiment

    SciTech Connect

    Soukhanovskii, V. A.; Maingi, R.; Gates, D.A.; Menard, J.E.; Bush, C.E.

    2009-01-01

    Steady-state handling of divertor heat flux is a critical issue for both ITER and spherical torus-based devices with compact high power density divertors. Significant reduction of heat flux to the divertor plate has been achieved simultaneously with favorable core and pedestal confinement and stability properties in a highly shaped lower single null configuration in the National Spherical Torus Experiment (NSTX) [M. Ono , Nucl. Fusion 40, 557 2000] using high magnetic flux expansion at the divertor strike point and the radiative divertor technique. A partial detachment of the outer strike point was achieved with divertor deuterium injection leading to peak flux reduction from 4-6 MW m(-2) to 0.5-2 MW m(-2) in small-ELM 0.8-1.0 MA, 4-6 MW neutral beam injection-heated H-mode discharges. A self-consistent picture of the outer strike point partial detachment was evident from divertor heat flux profiles and recombination, particle flux and neutral pressure measurements. Analytic scrape-off layer parallel transport models were used for interpretation of NSTX detachment experiments. The modeling showed that the observed peak heat flux reduction and detachment are possible with high radiated power and momentum loss fractions, achievable with divertor gas injection, and nearly impossible to achieve with main electron density, divertor neutral density or recombination increases alone.

  18. Temperature initiated passive cooling system

    DOEpatents

    Forsberg, C.W.

    1994-11-01

    A passive cooling system for cooling an enclosure only when the enclosure temperature exceeds a maximum standby temperature comprises a passive heat transfer loop containing heat transfer fluid having a particular thermodynamic critical point temperature just above the maximum standby temperature. An upper portion of the heat transfer loop is insulated to prevent two phase operation below the maximum standby temperature. 1 fig.

  19. Temperature initiated passive cooling system

    DOEpatents

    Forsberg, Charles W.

    1994-01-01

    A passive cooling system for cooling an enclosure only when the enclosure temperature exceeds a maximum standby temperature comprises a passive heat transfer loop containing heat transfer fluid having a particular thermodynamic critical point temperature just above the maximum standby temperature. An upper portion of the heat transfer loop is insulated to prevent two phase operation below the maximum standby temperature.

  20. High heat flux Langmuir probe array for the DIII-D divertor platesa)

    NASA Astrophysics Data System (ADS)

    Watkins, J. G.; Taussig, D.; Boivin, R. L.; Mahdavi, M. A.; Nygren, R. E.

    2008-10-01

    Two modular arrays of Langmuir probes designed to handle a heat flux of up to 25 MW/m2 for 10 s exposures have been installed in the lower divertor target plates of the DIII-D tokamak. The 20 pyrolytic graphite probe tips have more than three times higher thermal conductivity and 16 times larger mass than the original DIII-D isotropic graphite probes. The probe tips have a fixed 12.5° surface angle to distribute the heat flux more uniformly than the previous 6 mm diameter domed collectors and a symmetric "rooftop" design to allow operation with reversed toroidal magnetic field. A large spring-loaded contact area improves heat conduction from each probe tip through a ceramic insulator into a cooled graphite divertor floor tile. The probe tips, brazed to molybdenum foil to ensure good electrical contact, are mounted in a ceramic tray for electrical isolation and reliable cable connections. The new probes are located 1.5 cm radially apart in a staggered arrangement near the entrance to the lower divertor pumping baffle and are linearly spaced 3 cm apart on the shelf above the in-vessel cryopump. Typical target plate profiles of Jsat, Te, and Vf with 4 mm spatial resolution are shown.

  1. The DIII-D Radiative Divertor Project: Status and plans

    SciTech Connect

    Smith, J.P.; Baxi, C.B.; Bozek, A.S.

    1996-10-01

    New divertor hardware is being designed and fabricated for the Radiative Divertor modification of the DIII-D tokamak. The installation of the hardware has been separated into two phases, the first phase starting in October of 1996 and the second and final phase, in 1998. The phased approach enables the continuation of the divertor characterization research in the lower divertor while providing pumping for density control in high triangularity, single- or double-null advanced tokamak discharges. When completed, the Radiative Divertor Project hardware will provide pumping at all four strike points of a double-null, high triangularity discharge and provide baffling of the neutral particles from transport back to the core plasma. By puffing neutral gas into the divertor region, a reduction in the heat flux on the target plates will be be demonstrated without a large rise in core density. This reduction in heat flux is accomplished by dispersing the power with radiation in the divertor region. Experiments and modeling have formed the basis for the new design. The capability of the DIII-D cryogenic system is being upgraded as part of this project. The increased capability of the cryogenic system will allow delivery of liquid helium and nitrogen to three new cryopumps. Physics studies on the effects of slot width and length can be accomplished easily with the design of the Radiative Divertor. The slot width can be varied by installing graphite tiles of different geometry. The change in slot length, the distance from the X-point to the target plate, requires relocating the structure vertically and can be completed in about 6-8 weeks. Radiative Divertor diagnostics are being designed to provide comprehensive measurements for diagnosing the divertor. Required diagnostic modifications will be minimal for Phase 1, but extensive for Phase 2 installation. These Phase 2 diagnostics will be required to fully diagnose the high triangularity discharges in the divertor slots.

  2. Divertor for use in fusion reactors

    DOEpatents

    Christensen, Uffe R.

    1979-01-01

    A poloidal divertor for a toroidal plasma column ring having a set of poloidal coils co-axial with the plasma ring for providing a space for a thick shielding blanket close to the plasma along the entire length of the plasma ring cross section and all the way around the axis of rotation of the plasma ring. The poloidal coils of this invention also provide a stagnation point on the inside of the toroidal plasma column ring, gently curving field lines for vertical stability, an initial plasma current, and the shaping of the field lines of a separatrix up and around the shielding blanket.

  3. Comparison of ELM heat loads in snowflake and standard divertors

    SciTech Connect

    Rognlien, T D; Cohen, R H; Ryutov, D D; Umansky, M V

    2012-05-08

    An analysis is given of the impact of the tokamak divertor magnetic structure on the temporal and spatial divertor heat flux from edge localized modes (ELMs). Two configurations are studied: the standard divertor where the poloidal magnetic field (B{sub p}) varies linearly with distance (r) from the magnetic null and the snowflake where B{sub p} varies quadratrically with r. Both one and two-dimensional models are used to analyze the effect of the longer magnetic field length between the midplane and the divertor plate for the snowflake that causes a temporal dilation of the ELM divertor heat flux. A second effect discussed is the appearance of a broad region near the null point where the poloidal plasma beta can substantially exceed unity, especially for the snowflake configuration during the ELM; such a condition is likely to drive additional radial ELM transport.

  4. Super-X divertors and high power density fusion devices

    SciTech Connect

    Valanju, P. M.; Kotschenreuther, M.; Mahajan, S. M.; Canik, J.

    2009-05-15

    The Super-X Divertor (SXD), a robust axisymmetric redesign of the divertor magnetic geometry that can allow a fivefold increase in the core power density of toroidal fusion devices, is presented. With small changes in poloidal coils and currents for standard divertors, the SXD allows the largest divertor plate radius inside toroidal field coils. This increases the plasma-wetted area by 2-3 times over all flux-expansion-only methods (e.g., plate near main X point, plate tilting, X divertor, and snowflake), decreases parallel heat flux and hence plasma temperature at plate, and increases connection length by 2-5 times. Examples of high-power-density fusion devices enabled by SXD are discussed; the most promising near-term device is a 100 MW modular compact fusion neutron source 'battery' small enough to fit inside a conventional fission blanket.

  5. RELAP5 MODEL OF THE DIVERTOR PRIMARY HEAT TRANSFER SYSTEM

    SciTech Connect

    Popov, Emilian L; Yoder Jr, Graydon L; Kim, Seokho H

    2010-08-01

    This report describes the RELAP5 model that has been developed for the divertor primary heat transfer system (PHTS). The model is intended to be used to examine the transient performance of the divertor PHTS and evaluate control schemes necessary to maintain parameters within acceptable limits during transients. Some preliminary results are presented to show the maturity of the model and examine general divertor PHTS transient behavior. The model can be used as a starting point for developing transient modeling capability, including control system modeling, safety evaluations, etc., and is not intended to represent the final divertor PHTS design. Preliminary calculations using the models indicate that during normal pulsed operation, present pressurizer controls may not be sufficient to keep system pressures within their desired range. Additional divertor PHTS and control system design efforts may be required to ensure system pressure fluctuation during normal operation remains within specified limits.

  6. OEDGE Modeling of Divertor Fueling at DIII-D

    NASA Astrophysics Data System (ADS)

    Bray, B. D.; Leonard, A. W.; Elder, J. D.; Stangeby, P. C.

    2015-11-01

    Onion-skin-modeling (OSM) is used to assess the affect of divertor closure on pedestal fueling sources. The OSM includes information from a wide range of diagnostic measurements at DIII-D to constrain the model background plasma for better simulation of neutrals and impurity ions and spectroscopy to compare to the results of the simulation. DIII-D has open lower divertor and closed upper divertor configurations which can be run with similar discharges. Progress toward modeling the pedestal fueling in low density plasmas for these cases will be presented as well as initial comparisons of recent lower single null discharges with the outer leg on the divertor shelf (fully open) and divertor floor (partially open). Work supported by the US DOE under DE-FC02-04ER54698 and DE-AC52-07NA27344.

  7. Development of a fuel-rod simulator and small-diameter thermocouples for high-temperature, high-heat-flux tests in the Gas-Cooled Fast Reactor Core Flow Test Loop

    SciTech Connect

    McCulloch, R.W.; MacPherson, R.E.

    1983-03-01

    The Core Flow Test Loop was constructed to perform many of the safety, core design, and mechanical interaction tests in support of the Gas-Cooled Fast Reactor (GCFR) using electrically heated fuel rod simulators (FRSs). Operation includes many off-normal or postulated accident sequences including transient, high-power, and high-temperature operation. The FRS was developed to survive: (1) hundreds of hours of operation at 200 W/cm/sup 2/, 1000/sup 0/C cladding temperature, and (2) 40 h at 40 W/cm/sup 2/, 1200/sup 0/C cladding temperature. Six 0.5-mm type K sheathed thermocouples were placed inside the FRS cladding to measure steady-state and transient temperatures through clad melting at 1370/sup 0/C.

  8. To develop a dynamic model of a collector loop for purpose of improved control of solar heating and cooling. Final technical report. [TRNSYS code

    SciTech Connect

    Herczfeld, P R; Fischl, R

    1980-01-01

    The program objectives were to (1) assess the feasibility of using the TRNSYS computer code for solar heating and cooling control studies and modify it wherever possible, and (2) develop a new dynamic model of the solar collector which reflects the performance of the collector under transient conditions. Also, the sensitivity of the performance of this model to the various system parameters such as collector time constants, flow rates, turn-on and turn-off temperature set points, solar insolation, etc., was studied. Results are presented and discussed. (WHK)

  9. A super-cusp divertor configuration for tokamaks

    DOE PAGESBeta

    Ryutov, D. D.

    2015-08-26

    Our study demonstrates a remarkable flexibility of advanced divertor configurations created with the remote poloidal field coils. The emphasis here is on the configurations with three poloidal field nulls in the divertor area. We are seeking the structures where all three nulls lie on the same separatrix, thereby creating two zones of a very strong flux expansion, as envisaged in the concept of Takase’s cusp divertor. It turns out that the set of remote coils can produce a cusp divertor, with additional advantages of: (i) a large stand-off distance between the divertor and the coils and (ii) a thorough controlmore » that these coils exert over the fine features of the configuration. In reference to these additional favourable properties acquired by the cusp divertor, the resulting configuration could be called ‘a super-cusp’. General geometrical features of the three-null configurations produced by remote coils are described. Furthermore, issues on the way to practical applications include the need for a more sophisticated control system and possible constraints related to excessively high currents in the divertor coils.« less

  10. A super-cusp divertor configuration for tokamaks

    SciTech Connect

    Ryutov, D. D.

    2015-08-26

    Our study demonstrates a remarkable flexibility of advanced divertor configurations created with the remote poloidal field coils. The emphasis here is on the configurations with three poloidal field nulls in the divertor area. We are seeking the structures where all three nulls lie on the same separatrix, thereby creating two zones of a very strong flux expansion, as envisaged in the concept of Takase’s cusp divertor. It turns out that the set of remote coils can produce a cusp divertor, with additional advantages of: (i) a large stand-off distance between the divertor and the coils and (ii) a thorough control that these coils exert over the fine features of the configuration. In reference to these additional favourable properties acquired by the cusp divertor, the resulting configuration could be called ‘a super-cusp’. General geometrical features of the three-null configurations produced by remote coils are described. Furthermore, issues on the way to practical applications include the need for a more sophisticated control system and possible constraints related to excessively high currents in the divertor coils.

  11. SOLPS Modeling of Slot Divertor Configuration on DIII-D

    NASA Astrophysics Data System (ADS)

    Sang, C. F.; Stangeby, P. C.; Guo, H. Y.; Lao, L. L.

    2015-11-01

    A major thrust of the DIII-D boundary/PMI initiative is to develop an advanced divertor configuration for next-step devices, such as FNSF and DEMO. We are adopting an integrated approach by optimizing both divertor structure and magnetic shape. Initial SOLPS modeling was carried out to optimize divertor structure shape to enhance divertor power dissipation, focusing on slot configurations. In particular, four different slot divertor structures, i.e., orthogonal-target slot, slanted-target slot, very narrow slot and v-shaped slot have been analyzed and comparisons made with an open divertor structure. It is found that the slot helps to trap recycling neutrals and impurities thus increasing radiative power dissipation in the divertor, reducing the electron temperature Te and the perpendicular heat flux q⊥ at the target plate. As expected, a narrower slot leads to lower Te and q⊥ than a less narrow one. The v-shaped slot appears to be especially effective at redirecting and concentrating recycling neutrals and impurities near the separatrix, thus promoting detachment at a lower upstream density than the other configurations. Work supported by US DOE under DE-FC02-04ER54698.

  12. Current and Potential Distribution in a Divertor with Torioidally-Asymmetric Biasing of the Divertor Plate

    SciTech Connect

    Cohen, R H; Ryutov, D D; Counsell, G F; Helander, P

    2006-06-06

    Toroidally-asymmetric biasing of the divertor plate may increase convective cross-field transport in SOL and thereby reduce the divertor heat load. Experiments performed with the MAST spherical tokamak generally agree with a simple theory of non-axisymmetric biasing. However, some of the experimental results have not yet received a theoretical explanation. In particular, existing theory seems to overestimate the asymmetry between the positive and the negative biasing. Also lacking a theoretical explanation is experimentally observed increase of the average floating potential in the main SOL in the presence of biasing. In this paper we attempt to solve these problems by accounting for the closing of the currents (driven by the biasing) in a strong-shear region near the X-point. We come up with the picture which, at least qualitatively, agrees with these experimental results.

  13. Modeling impurities and tilted plates in the ITER divertor

    SciTech Connect

    Rensink, M.E.; Rognlien, T.D.

    1996-07-29

    The UEDGE 2-D edge transport code is used to model the effect of impurities and tilted divertor plates for the ITER SOL/divertor region. The impurities are modeled as individual charge states using either the FMOMBAL 21-moment description or parallel force balance. Both helium and neon impurities are used together with a majority hydrogenic species. A fluid description of the neutrals is used that includes parallel inertia and neutral-neutral collisions. Effects of geometry are analyzed by using the nonorthogonal mesh capability of UEDGE to obtain solutions with the divertor plate tilted at various angles.

  14. Optics design of the divertor infrared television of KSTAR.

    PubMed

    Oh, S; Lee, K; Lee, H H; Wi, H M; Kim, Y S; Kang, C S

    2014-11-01

    The divertor Infrared television (IR TV) system for monitoring the temperature of a divertor and localized hot spots will be installed on the upper port of the N-port in the Korea Superconducting Tokamak Advanced Research (KSTAR). The cassette of KSTAR makes a periscope inevitable for the divertor IR TV. In this article, 4 design concepts for the periscope were examined, and the design based on Keplerian was shown to have better stabilities in alignment and the vibration. The final optics design based on an f-theta lens, Keplerian, and telecentric lens was derived. PMID:25430316

  15. A review of ELMs in divertor tokamaks

    SciTech Connect

    Hill, D.N.

    1996-05-23

    This paper reviews what is known about edge localized modes (ELMs), with an emphasis on their effect on the scrape-off layer and divertor plasmas. ELM effects have been measured in the ASDEX-U, C-Mod, COMPASS-D, DIII-D, JET, JFT-2M,JT-60U, and TCV tokamaks and are reported here. At least three types of ELMs have been identified and their salient features determined. Type-1 giant ELMs can cause the sudden loss of up to 10-15% of the plasma stored energy but their amplitude ({Delta}W/W) does not increase with increasing power. Type- 3 ELMs are observed near the H-mode power threshold and produce small energy dumps (1-3% of the stored energy). All ELMs increase the scrape- off layer plasma and produce particle fluxes on the divertor targets which are as much as ten times larger that the quiescent phase between ELMs. The divertor heat pulse is largest on the inner target, unlike that of L-Mode or quiescent H-mode; some tokamaks report radial structure in the heat flux profile which is suggestive of islands or helical structures. The power scaling of Type-1 ELM amplitude and frequency have been measured in several tokamaks and has recently been applied to predictions of the ELM Size in ITER. Concern over the expected ELM amplitude has led to a number of experiments aimed at demonstrating active control of ELMs. Impurity gas injection with feedback control on the radiation loss in ASDEX-U suggests that a promising mode of operation (the CDH-mode) with a very small type-3 ELMs can be maintained with heating power sell above the H-mode threshold, where giant type-1 ELMs can be maintained with heating power well above the H-mode threshold, where Giant type-1 ELMs are normally observed. While ELMs have many potential negative effects, the beneficial effect of ELMs in providing density control and limiting the core plasma impurity content in high confinement H- mode discharges should not be overlooked.

  16. Surface modifications of W divertor components for EAST during exposure to high heat loads with He

    NASA Astrophysics Data System (ADS)

    Li, C.; Greuner, H.; Yuan, Y.; Zhao, S. X.; Luo, G. N.; Böswirth, B.; Fu, B. Q.; Jia, Y. Z.; Liu, X.; Liu, W.

    2015-08-01

    Flat-type W/Cu plasma-facing components have been developed for the new generation divertor of the Chinese Experimental Advanced Superconducting Tokamak. Surface modifications of such actively water-cooled W components following short and long pulse high heat loading coupled with He particle loads with fluence of 3 × 1022 m-2 have been investigated. An adiabatically loaded W block was investigated as a comparison and exposed to short pulse loads. Blistering was observed on all sample surfaces, but was less pronounced on the components than on the W block, due to the significant lower surface temperature caused by active cooling. For components, longer pulse loads gave rise to a rougher surface. Furthermore, most blisters on components are found to be less than 1 μm in diameter, with just a very few blisters larger than 1 μm, observed only in some near <1 1 1> grains.

  17. Potential collector surface materials for divertors

    NASA Astrophysics Data System (ADS)

    Prebble, H. E.; Forty, C. B. A.; Butterworth, G. J.

    1992-09-01

    Twelve refractory materials have been investigated to assess their suitability for use as collector target materials for divertors. The steady state limiting heat flux to avoid melting of the collector material has been calculated as a function of thickness using a simple one-dimensional thermal-hydraulics model. Similarly, the limiting heat flux to avoid melting following a plasma disruption has been calculated as a function of collector surface temperature just prior to the disruption event. Finally, the resistance of each collector material to thermal shock was estimated. The calculations indicate diamond, graphite and tungsten as favourable materials, BN, AlN, TiN, V 2C and beryllium as unsuitable and BeO, SiC, TiC and TIB 2 as exhibiting combinations of favourable and unfavourable properties.

  18. Design Construction and Operation of a Supercritical Carbon Dioxide (sCO2) Loop for Investigation of Dry Cooling and Natural Circulation Potential for Use in Advanced Small Modular Reactors Utilizing sCO2 Power Conversion Cycles.

    SciTech Connect

    Middleton, Bobby D.; Rodriguez, Salvador B.; Carlson, Matthew David

    2015-11-01

    This report outlines the work completed for a Laboratory Directed Research and Development project at Sandia National Laboratories from October 2012 through September 2015. An experimental supercritical carbon dioxide (sCO 2 ) loop was designed, built, and o perated. The experimental work demonstrated that sCO 2 can be uti lized as the working fluid in an air - cooled, natural circulation configuration to transfer heat from a source to the ultimate heat sink, which is the surrounding ambient environment in most ca ses. The loop was also operated in an induction - heated, water - cooled configuration that allows for measurements of physical parameters that are difficult to isolate in the air - cooled configuration. Analysis included the development of two computational flu id dynamics models. Future work is anticipated to answer questions that were not covered in this project.

  19. Divertor IR thermography on Alcator C-Moda)

    NASA Astrophysics Data System (ADS)

    Terry, J. L.; LaBombard, B.; Brunner, D.; Payne, J.; Wurden, G. A.

    2010-10-01

    Alcator C-Mod is a particularly challenging environment for thermography. It presents issues that will similarly face ITER, including low-emissivity metal targets, low-Z surface films, and closed divertor geometry. In order to make measurements of the incident divertor heat flux using IR thermography, the C-Mod divertor has been modified and instrumented. A 6° toroidal sector has been given a 2° toroidal ramp in order to eliminate magnetic field-line shadowing by imperfectly aligned divertor tiles. This sector is viewed from above by a toroidally displaced IR camera and is instrumented with thermocouples and calorimeters. The camera provides time histories of surface temperatures that are used to compute incident heat-flux profiles. The camera sensitivity is calibrated in situ using the embedded thermocouples, thus correcting for changes and nonuniformities in surface emissivity due to surface coatings.

  20. Status of National Spherical Torus Experiment Liquid Lithium Divertor

    NASA Astrophysics Data System (ADS)

    Kugel, H. W.; Viola, M.; Ellis, R.; Bell, M.; Gerhardt, S.; Kaita, R.; Kallman, J.; Majeski, R.; Mansfield, D.; Roquemore, A. L.; Schneider, H.; Timberlake, J.; Zakharov, L.; Nygren, R. E.; Allain, J. P.; Maingi, R.; Soukhanovskii, V.

    2009-11-01

    Recent NSTX high power divertor experiments have shown significant and recurring benefits of solid lithium coatings on plasma facing components to the performance of divertor plasmas in both L- and H- mode confinement regimes heated by high-power neutral beams. The next step in this work is the 2009 installation of a Liquid Lithium Divertor (LLD). The 20 cm wide LLD located on the lower outer divertor, consists of four, 80 degree sections; each section is separated by a row of graphite diagnostic tiles. The temperature controlled LLD structure consists of a 0.01cm layer of vacuum flame-sprayed, 50 percent porous molybdenum, on top of 0.02 cm, 316-SS brazed to a 1.9 cm Cu base. The physics design of the LLD encompasses the desired plasma requirements, the experimental capabilities and conditions, power handling, radial location, pumping capability, operating temperature, lithium filling, MHD forces, and diagnostics for control and characterization.

  1. Divertor IR thermography on Alcator C-Mod.

    PubMed

    Terry, J L; LaBombard, B; Brunner, D; Payne, J; Wurden, G A

    2010-10-01

    Alcator C-Mod is a particularly challenging environment for thermography. It presents issues that will similarly face ITER, including low-emissivity metal targets, low-Z surface films, and closed divertor geometry. In order to make measurements of the incident divertor heat flux using IR thermography, the C-Mod divertor has been modified and instrumented. A 6° toroidal sector has been given a 2° toroidal ramp in order to eliminate magnetic field-line shadowing by imperfectly aligned divertor tiles. This sector is viewed from above by a toroidally displaced IR camera and is instrumented with thermocouples and calorimeters. The camera provides time histories of surface temperatures that are used to compute incident heat-flux profiles. The camera sensitivity is calibrated in situ using the embedded thermocouples, thus correcting for changes and nonuniformities in surface emissivity due to surface coatings. PMID:21034041

  2. Divertor IR thermography on Alcator C-Mod

    SciTech Connect

    Terry, J. L.; LaBombard, B.; Brunner, D.; Payne, J.; Wurden, G. A.

    2010-10-15

    Alcator C-Mod is a particularly challenging environment for thermography. It presents issues that will similarly face ITER, including low-emissivity metal targets, low-Z surface films, and closed divertor geometry. In order to make measurements of the incident divertor heat flux using IR thermography, the C-Mod divertor has been modified and instrumented. A 6 deg. toroidal sector has been given a 2 deg. toroidal ramp in order to eliminate magnetic field-line shadowing by imperfectly aligned divertor tiles. This sector is viewed from above by a toroidally displaced IR camera and is instrumented with thermocouples and calorimeters. The camera provides time histories of surface temperatures that are used to compute incident heat-flux profiles. The camera sensitivity is calibrated in situ using the embedded thermocouples, thus correcting for changes and nonuniformities in surface emissivity due to surface coatings.

  3. Local Effects of Biased Electrodes in the Divertor of NSTX

    SciTech Connect

    Zweben, S.; Campanell, M. D.; Lyons, B. C.; Maqueda, R. J.; Raitses, Y.; Roquemore, A. L.; Scotti, F.

    2012-05-07

    The goal of this paper is to characterize the effects of small non-axisymmetric divertor plate electrodes on the local scrape-off layer plasma. Four small rectangular electrodes were installed into the outer divertor plates of NSTX. When the electrodes were located near the outer divertor strike point and biased positively, there was an increase in the nearby probe currents and probe potentials and an increase in the LiI light emission at the large major radius end of these electrodes. When an electrode located farther outward from the outer divertor strike point was biased positively, there was sometimes a significant decrease in the LiI light emission at the small major radius end of this electrode, but there were no clear effects on the nearby probes. No non-local effects were observed with the biasing of these electrodes.

  4. Compatibility of detached divertor operation with robust edge pedestal performance

    NASA Astrophysics Data System (ADS)

    Leonard, A. W.; Makowski, M. A.; McLean, A. G.; Osborne, T. H.; Snyder, P. B.

    2015-08-01

    The compatibility of detached radiative divertor operation with a robust H-mode pedestal is examined in DIII-D. A density scan produced low temperature plasmas at the divertor target, Te ⩽ 2 eV, with high radiation leading to a factor of ⩾4 drop in peak divertor heat flux. The cold radiative plasma was confined to the divertor and did not extend across the separatrix in X-point region. A robust H-mode pedestal was maintained with a small degradation in pedestal pressure at the highest densities. The response of the pedestal pressure to increasing density is reproduced by the EPED pedestal model. However, agreement of the EPED model with experiment at high density requires an assumption of reduced diamagnetic stabilization of edge Peeling-Ballooning modes.

  5. Structural design of the DIII-D radiative divertor

    SciTech Connect

    Reis, E.E.; Smith, J.P.; Baxi, C.B.; Bozek, A.S.; Chin, E.; Hollerbach, M.A.; Laughon, G.J.; Sevier, D.L.

    1996-10-01

    The divertor of the DIII-D tokamak is being modified to operate as a slot type, dissipative divertor. This modification, called the Radiative Divertor Program (RDP) is being carried out in two phases. The design and analysis is complete and hardware is being fabricated for the first phase. This first phase consists of an upper divertor baffle and cryopump to provide some density control for high triangularity, single or double null discharges. Installation of the first phase is scheduled to start in October, 1996. The second phase provides pumping at all four divertor strike points of double null high triangularity discharges and baffling of the neutral particles from transport back to the core plasma. Studies of the effects of varying the slot length and width of the divertor can be easily accomplished with the design of RDP hardware. Static and dynamic analyses of the baffle structures, new cryopumps, and feedlines were performed during the preliminary and final design phases. Disruption loads and differential thermal displacements must be accommodated in the design of these components. With the full RDP hardware installed, the plasma current in DIII-D will be a maximum of 3.0 MA. Plasma disruptions induce toroidal currents in the cryopump, producing complex dynamic loads. Simultaneously, the vacuum vessel vibrations impose a sinusoidal base excitation to the supports for the cryopump. Static and dynamic analyses of the cryopump demonstrate that the stresses due to disruption and thermal loadings satisfy the stress and deflection criteria.

  6. Development of a radiative divertor for DIII-D

    SciTech Connect

    Allen, S.L.; Brooks, N.H.; Campbell, R.B.

    1994-07-01

    We have used experiments and modeling to develop a new radiative divertor configuration for DIII-D. Gas puffing experiments with the existing open divertor have shown the creation of a localized ({approximately}10 cm diameter) radiation zone which results in substantial reduction (3--10) in the divertor heat flux while {delta}{sub E} remains {approximately}2 times ITER-89P scaling. However, ne increases with D{sub 2} puffing, and Z{sub eff} increases with neon puffing. Divertor structures are required to minimize the effects on the core plasma. The UEDGE fluid code, benchmarked with DIII-D data, and the DEGAS neutrals transport code are used to estimate the effectiveness of divertor configurations; slots reduce the core ionization more than baffles. The overall divertor shape is set by confinement studies which indicate that high triangularity ({delta} {approximately}0.8) is important for high {tau}{sub E} VH-modes. Results from engineering feasibility studies, including diagnostic access, will be presented.

  7. Turbulent Simulations of Divertor Detachment Based On BOUT + + Framework

    NASA Astrophysics Data System (ADS)

    Chen, Bin; Xu, Xueqiao; Xia, Tianyang; Ye, Minyou

    2015-11-01

    China Fusion Engineering Testing Reactor is under conceptual design, acting as a bridge between ITER and DEMO. The detached divertor operation offers great promise for a reduction of heat flux onto divertor target plates for acceptable erosion. Therefore, a density scan is performed via an increase of D2 gas puffing rates in the range of 0 . 0 ~ 5 . 0 ×1023s-1 by using the B2-Eirene/SOLPS 5.0 code package to study the heat flux control and impurity screening property. As the density increases, it shows a gradually change of the divertor operation status, from low-recycling regime to high-recycling regime and finally to detachment. Significant radiation loss inside the confined plasma in the divertor region during detachment leads to strong parallel density and temperature gradients. Based on the SOLPS simulations, BOUT + + simulations will be presented to investigate the stability and turbulent transport under divertor plasma detachment, particularly the strong parallel gradient driven instabilities and enhanced plasma turbulence to spread heat flux over larger surface areas. The correlation between outer mid-plane and divertor turbulence and the related transport will be analyzed. Prepared by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-675075.

  8. Design and analysis of the cryopump for the D3-D advanced divertor

    NASA Astrophysics Data System (ADS)

    Reis, E.; Almajan, I.; Baxi, C. B.; Schaffer, M. J.; Sevier, D. L.; Smith, J. P.; Menon, M. M.

    1992-09-01

    A cryocondensation pump for the DIII-D advanced divertor program is to be installed in the vacuum vessel in the fall of 1992. The purpose of the cryopump is to remove gas from the divertor, reduce recycling to the plasma, and to provide reduced density plasmas for experimental study. The pump is designed for a pumping speed of 50,000 l/s at 0.4 mtorr. The major pump components are toroidally continuous to minimize inductive voltages, thereby greatly reducing the risk of any electrical breakdown during disruptions. The cryopump consists of a 25 mm Inconel tube, 10 m long, cooled by liquid helium. It is surrounded by liquid nitrogen-cooled shields and a segmented ambient temperature radiation/particle shield. The outer nitrogen shield has a toroidally discontinuous copper coating to enhance thermal conductivity while maintaining a high toroidal electrical resistance to minimize electromagnetic loads during disruptions. The pump is cooled by 10 g/s of liquid helium at an inlet pressure of 115 kPa and temperature of 4.35 K. The pump is subjected to a steady-state heat load of less than 10 W due to conduction and radiation heat transfer. The helium tube will be subjected to Joule heating of less than 182J due to induced current and a particle load of less than 20 W during plasma operation. Thermal analysis and tests show that the helium tube can absorb a transient heat load of up to 100 W for 10 s and still pump deuterium at 6.3 K.

  9. Spectroscopic Measurement System for ITER Divertor Plasma: Impurity Influx Monitor (divertor)

    SciTech Connect

    Sugie, Tatsuo; Ogawa, Hiroaki; Kusama, Yoshinori; Kasai, Satoshi

    2008-03-12

    The detailed design of the Impurity Influx Monitor (divertor) has been carried out to provide the measurement capability in the harsh environment such as higher irradiation levels of neutron, gamma-ray and particles than in present devices. The in-situ calibration system using a micro retro-reflector array has been developed to monitor the sensitivity change of the optical system due to the environmental effects. The optical alignment system for the Monitor has been developed by using a dedicated optics for alignment in the collection optics for measurement.

  10. Comment on “Magnetic geometry and physics of advanced divertors: The X-divertor and the snowflake” [Phys. Plasmas 20, 102507 (2013)

    SciTech Connect

    Ryutov, D. D. Cohen, R. H.; Rognlien, T. D.; Soukhanovskii, V. A.; Umansky, M. V.

    2014-05-15

    In the recently published paper “Magnetic geometry and physics of advanced divertors: The X-divertor and the snowflake” [Phys. Plasmas 20, 102507 (2013)], the authors raise interesting and important issues concerning divertor physics and design. However, the paper contains significant errors: (a) The conceptual framework used in it for the evaluation of divertor “quality” is reduced to the assessment of the magnetic field structure in the outer Scrape-Off Layer. This framework is incorrect because processes affecting the pedestal, the private flux region and all of the divertor legs (four, in the case of a snowflake) are an inseparable part of divertor operation. (b) The concept of the divertor index focuses on only one feature of the magnetic field structure and can be quite misleading when applied to divertor design. (c) The suggestion to rename the divertor configurations experimentally realized on NSTX (National Spherical Torus Experiment) and DIII-D (Doublet III-D) from snowflakes to X-divertors is not justified: it is not based on comparison of these configurations with the prototypical X-divertor, and it ignores the fact that the NSTX and DIII-D poloidal magnetic field geometries fit very well into the snowflake “two-null” prescription.

  11. Comment on "Magnetic geometry and physics of advanced divertors: The X-divertor and the snowflake" [Phys. Plasmas 20, 102507 (2013)

    NASA Astrophysics Data System (ADS)

    Ryutov, D. D.; Cohen, R. H.; Rognlien, T. D.; Soukhanovskii, V. A.; Umansky, M. V.

    2014-05-01

    In the recently published paper "Magnetic geometry and physics of advanced divertors: The X-divertor and the snowflake" [Phys. Plasmas 20, 102507 (2013)], the authors raise interesting and important issues concerning divertor physics and design. However, the paper contains significant errors: (a) The conceptual framework used in it for the evaluation of divertor "quality" is reduced to the assessment of the magnetic field structure in the outer Scrape-Off Layer. This framework is incorrect because processes affecting the pedestal, the private flux region and all of the divertor legs (four, in the case of a snowflake) are an inseparable part of divertor operation. (b) The concept of the divertor index focuses on only one feature of the magnetic field structure and can be quite misleading when applied to divertor design. (c) The suggestion to rename the divertor configurations experimentally realized on NSTX (National Spherical Torus Experiment) and DIII-D (Doublet III-D) from snowflakes to X-divertors is not justified: it is not based on comparison of these configurations with the prototypical X-divertor, and it ignores the fact that the NSTX and DIII-D poloidal magnetic field geometries fit very well into the snowflake "two-null" prescription.

  12. An implicit Monte Carlo method for simulation of impurity transport in divertor plasma

    SciTech Connect

    Suzuki, Akiko; Hayashi, Nobuhiko; Hatayama, Akiyoshi

    1997-02-01

    A new {open_quotes}implicit{close_quotes} Monte Carlo (IMC) method has been developed to simulate ionization and recombination processes of impurity ions in divertor plasmas. The IMC method takes into account many ionization and recombination processes during a time step {Delta}t. The time step is not limited by a condition, {Delta}t {much_lt} {tau}{sub min} ({tau}{sub min}; the minimum characteristic time of atomic processes), which is forced to be adopted in conventional Monte Carlo methods. We incorporate this method into a one-dimensional impurity transport model. In this transport calculation, impurity ions are followed with the time step about 10 times larger than that used in conventional methods. The average charge state of impurities, (Z), and the radiative cooling rate, L(T{sub e}), are calculated at the electron temperature T{sub e} in divertor plasmas. These results are compared with those obtained from the simple noncoronal model. 10 refs., 7 figs.

  13. Thermomechanical design evaluation and material properties requirements for net divertor elements

    NASA Astrophysics Data System (ADS)

    Zolti, E.

    1988-07-01

    The major thermomechanical problems of the divertor target plates of the Next European Torus (NET), the procedures and the material data needed for design evaluation are described. As a representative example a preliminary analysis of the divertor plates, which consist of an assembly of one-channel TZM elements, cooled with helium and protected with brazed graphite, is presented. The thermal and mechanical results show, on the one hand, the viability of this concept with respect to peak graphite temperatures, distortion limit to maintain adequate angles with the separatrix, and thermal fatigue and ratchetting of the TZM structure, for a peak surface heat flux of 5 MW/m 2. On the other hand, they contribute to the definition of the material testing programme in terms of further data needs, priorities and test parameter range. Emphasis is put on the fracture mechanics behaviour of the refractory materials under static and dynamic conditions, on the thermal and mechanical properties of intermediate joining layers, on irradiation effects on graphite and carbon fibre composites, and on the relevance of the graphite thermal conductivity in the plasma-to-coolant direction and of its strength under cyclic tensile stresses in the perpendicular direction.

  14. Production and fabrication of vanadium alloys for the radiative divertor program of DIII-D

    SciTech Connect

    Johnson, W.R.; Smith, J.P.; Trester, P.W.

    1997-04-01

    V-4Cr-4Ti alloy has been selected for use in the manufacture of a portion of the DIII-D Radiative Divertor upgrade. The production of a 1200-kg ingot of V-4Cr-4Ti alloy, and processing into final sheet and rod product forms suitable for components of the DIII-D Radiative Divertor structure, has been completed at Wah Chang (formerly Teledyne Wah Chang) of Albany, Oregon (WCA). Joining of V-4Cr-4Ti alloy has been identified as the most critical fabrication issue for its use in the RD Program, and research into several joining methods for fabrication of the RD components, including resistance seam, friction, and electron beam welding, is continuing. Preliminary trials have been successful in the joining of V-alloy to itself by electron beam, resistance, and friction welding processes, and to Inconel 625 by friction welding. An effort to investigate the explosive bonding of V-4Cr-4Ti alloy to Inconel 625 has also been initiated, and results have been encouraging. In addition, preliminary tests have been completed to evaluate the susceptibility of V-4Cr-4Ti alloy to stress corrosion cracking in DIII-D cooling water, and the effects of exposure to DIII-D bakeout conditions on the tensile and fracture behavior of V-4Cr-4Ti alloy.

  15. Carbon flows in attached divertor plasmas

    SciTech Connect

    Isler, R.C.; Brooks, N.H.; West, W.P.; Porter, G.D. |; The DIII-D Divertor Team

    1999-05-01

    Parallel flow velocities of carbon ions in the DIII-D divertor [J. Luxon {ital et al.}, {ital Plasma Physics Controlled Nuclear Fusion Research}, 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159; S. L. Allen {ital et al.}, {ital Controlled Fusion and Plasma Physics}, 1987 (Proc. 24th European Conf. Berchtesgaden, 1997), Vol. 21 A, Part III, p. 1129] have been studied under various operating conditions: L-mode (low-confinement mode), H-mode (high-confinement mode) with low-frequency ELMs (edge-localized modes), and H-mode with high-frequency ELMs. Both normal and reversed flows (toward the target plate and away from the target plate, respectively) are observed under all conditions, with the reversed speeds being as much as a factor of four greater than normal speeds. Magnitudes are approximately the same for L-mode and H-mode operation with high-frequency ELMs. In H-mode conditions with low-frequency ELMs, normal velocities are frequently observed to decline while reversed velocities increase in comparison to the other two conditions. {copyright} {ital 1999 American Institute of Physics.}

  16. Optical design study of an infrared visible viewing system for Wendelstein 7-X divertor observation and control

    SciTech Connect

    Cantarini, J.; Hildebrandt, D.; Koenig, R.; Wolf, R.; Klinkhamer, F.; Moddemeijer, K.; Vliegenthart, W.

    2008-10-15

    For the Wendelstein 7-X stellarator, which will allow quasicontinuous operation ({tau}{<=}30 min) with 10 MW of electron cyclotron radiation heating power, a conceptual design study for an IR/visible viewing system (IVVS) has been elaborated. Ten such systems, as part of the machine protection system, will be required for real time monitoring of all ten discrete, water cooled divertor modules with high spatial (<10 mm) resolution, in order to prevent local overheating of the target tiles, which could easily lead to their destruction. On the physics side, the systems will be used for divertor symmetry investigations by studying the power load distribution on all targets modules and by observing the island divertor plasmas in the light of H{alpha}, C II, and C III using the visible imaging section of the systems. The optics of the system can be divided into three parts: a mirror based optical head, creating an intermediate image, a Cassegrain telescope system, and individual lens based imaging optics adapted to the various detectors for IR (3-5 {mu}m and 8-14 {mu}m) and visible observations, with their optical light paths being separated by in-vacuum dichroic beam splitters.

  17. Optical design study of an infrared visible viewing system for Wendelstein 7-X divertor observation and control.

    PubMed

    Cantarini, J; Hildebrandt, D; König, R; Klinkhamer, F; Moddemeijer, K; Vliegenthart, W; Wolf, R

    2008-10-01

    For the Wendelstein 7-X stellarator, which will allow quasicontinuous operation (tau < or = 30 min) with 10 MW of electron cyclotron radiation heating power, a conceptual design study for an IR/visible viewing system (IVVS) has been elaborated. Ten such systems, as part of the machine protection system, will be required for real time monitoring of all ten discrete, water cooled divertor modules with high spatial (< 10 mm) resolution, in order to prevent local overheating of the target tiles, which could easily lead to their destruction. On the physics side, the systems will be used for divertor symmetry investigations by studying the power load distribution on all targets modules and by observing the island divertor plasmas in the light of H alpha, C II, and C III using the visible imaging section of the systems. The optics of the system can be divided into three parts: a mirror based optical head, creating an intermediate image, a Cassegrain telescope system, and individual lens based imaging optics adapted to the various detectors for IR (3-5 microm and 8-14 microm) and visible observations, with their optical light paths being separated by in-vacuum dichroic beam splitters. PMID:19044658

  18. Turbomachine rotor with improved cooling

    DOEpatents

    Hultgren, K.G.; McLaurin, L.D.; Bertsch, O.L.; Lowe, P.E.

    1998-05-26

    A gas turbine rotor has an essentially closed loop cooling air scheme in which cooling air drawn from the compressor discharge air that is supplied to the combustion chamber is further compressed, cooled, and then directed to the aft end of the turbine rotor. Downstream seal rings attached to the downstream face of each rotor disc direct the cooling air over the downstream disc face, thereby cooling it, and then to cooling air passages formed in the rotating blades. Upstream seal rings attached to the upstream face of each disc direct the heated cooling air away from the blade root while keeping the disc thermally isolated from the heated cooling air. From each upstream seal ring, the heated cooling air flows through passages in the upstream discs and is then combined and returned to the combustion chamber from which it was drawn. 5 figs.

  19. Turbomachine rotor with improved cooling

    DOEpatents

    Hultgren, Kent Goran; McLaurin, Leroy Dixon; Bertsch, Oran Leroy; Lowe, Perry Eugene

    1998-01-01

    A gas turbine rotor has an essentially closed loop cooling air scheme in which cooling air drawn from the compressor discharge air that is supplied to the combustion chamber is further compressed, cooled, and then directed to the aft end of the turbine rotor. Downstream seal rings attached to the downstream face of each rotor disc direct the cooling air over the downstream disc face, thereby cooling it, and then to cooling air passages formed in the rotating blades. Upstream seal rings attached to the upstream face of each disc direct the heated cooling air away from the blade root while keeping the disc thermally isolated from the heated cooling air. From each upstream seal ring, the heated cooling air flows through passages in the upstream discs and is then combined and returned to the combustion chamber from which it was drawn.

  20. Initial Development of the NSTX-U Snowflake Divertor Control

    NASA Astrophysics Data System (ADS)

    Vail, Patrick; Kolemen, Egemen; Welander, Anders; Lanctot, Matthew

    2015-11-01

    A feedback control system has been implemented at NSTX-U for real-time detection and manipulation of snowflake divertor (SFD) magnetic configurations. The SFD is an alternative magnetic divertor concept that is characterized by a second-order null formed by two x-points in close proximity. The SFD is an attractive option for heat flux mitigation for NSTX-U in which unmitigated peak heat fluxes in standard divertor operation near 20 MW/m2 may compromise plasma-facing components. The real-time control system at NSTX-U is capable of simultaneous control of multiple SFD parameters, such as the separation between the two x-points in the divertor region and their orientation. Control of SFD configurations in NSTX-U has been simulated in TOKSYS using the upgraded sets of poloidal field coils in both the upper and lower divertor regions. Performance of the real-time control system and its effect on plasma performance will be assessed experimentally as an initial step toward the development of the SFD concept at NSTX-U. Supported by the US DOE under DE-AC02-09CH11466.

  1. Radiative snowflake divertor studies in DIII-D

    NASA Astrophysics Data System (ADS)

    Soukhanovskii, V. A.; Allen, S. L.; Fenstermacher, M. E.; Hill, D. N.; Lasnier, C. J.; Makowski, M. A.; McLean, A. G.; Meyer, W. H.; Kolemen, E.; Groebner, R. J.; Hyatt, A. W.; Leonard, A. W.; Osborne, T. H.; Petrie, T. W.

    2015-08-01

    Recent DIII-D experiments assessed the snowflake divertor (SF) configuration in a radiative regime in H-mode discharges with D2 seeding. The SF configuration was maintained for many energy confinement times (2-3 s) in H-mode discharges (Ip = 1.2 MA, PNBI = 4- 5 MW, and B × ∇B down (favorable direction toward the divertor)), and found to be compatible with high performance operation (H98y2 ⩾ 1). The two studied SF configurations, the SF-plus and the SF-minus, have a small finite distance between the primary X-point and the secondary Bp null located in the private flux region or the common flux region, respectively. In H-mode discharges with the SF configurations (cf. H-mode discharges with the standard divertor with similar conditions) the stored energy lost per the edge localized mode (ELM) was reduced, and significant divertor heat flux reduction between and during ELMs was observed over a range of collisionalities, from lower density conditions toward a higher density H-modes with the radiative SF divertor.

  2. A numerical study of the thermal stability of solar loops

    NASA Technical Reports Server (NTRS)

    Klimchuk, J. A.; Antiochos, S. K.; Mariska, J. T.

    1987-01-01

    An important property of all loops is their thermal stability. If low lying hot loops were thermally unstable, for example, a great majority of the low loops on the Sun might be expected to be cool. How small perturbations evolve in low lying, linearly unstable hot loops was determined and how high lying, linearly stable hot loops respond to large amplitude disturbances such as might be expected on the Sun were examined. Only general descriptions and results are given.

  3. Radiative divertor plasmas with convection in DIII-D

    SciTech Connect

    Leornard, A.W.; Porter, G.D.; Wood, R.D.

    1998-01-01

    The radiation of divertor heat flux on DIII-D is shown to greatly exceed the limits imposed by assumptions of energy transport dominated by electron thermal conduction parallel to the magnetic field. Approximately 90% of the power flowing into the divertor is dissipated through low Z radiation and plasma recombination. The dissipation is made possible by an extended region of low electron temperature in the divertor. A one-dimensional analysis of the parallel heat flux finds that the electron temperature profile is incompatible with conduction dominated parallel transport. Plasma flow at up to the ion acoustic speed, produced by upstream ionization, can account for the parallel heat flux. Modeling with the two-dimensional fluid code UEDGE has reproduced many of the observed experimental features.

  4. A survey of problems in divertor and edge plasma theory

    SciTech Connect

    Boozer, A. ); Braams, B.; Weitzner, H. . Courant Inst. of Mathematical Sciences); Cohen, R. ); Hazeltine, R. . Inst. for Fusion Studies); Hinton, F. ); Houlberg, W. (Oak

    1992-12-22

    Theoretical physics problems related to divertor design are presented, organized by the region in which they occur. Some of the open questions in edge physics are presented from a theoretician's point of view. After a cursory sketch of the fluid models of the edge plasma and their numerical realization, the following topics are taken up: time-dependent problems, non-axisymmetric effects, anomalous transport in the scrape-off layer, edge kinetic theory, sheath effects and boundary conditions in divertors, electric field effects, atomic and molecular data issues, impurity transport in the divertor region, poloidally localized power dissipation (MARFEs and dense gas targets), helium ash removal, and neutral transport. The report ends with a summary of selected problems of particular significance and a brief bibliography of survey articles and related conference proceedings.

  5. A survey of problems in divertor and edge plasma theory

    SciTech Connect

    Boozer, A.; Braams, B.; Weitzner, H.; Cohen, R.; Hazeltine, R.; Hinton, F.; Houlberg, W.; Oktay, E.; Sadowski, W.; Post, D.; Sigmar, D.; Wootton, A.

    1992-12-22

    Theoretical physics problems related to divertor design are presented, organized by the region in which they occur. Some of the open questions in edge physics are presented from a theoretician`s point of view. After a cursory sketch of the fluid models of the edge plasma and their numerical realization, the following topics are taken up: time-dependent problems, non-axisymmetric effects, anomalous transport in the scrape-off layer, edge kinetic theory, sheath effects and boundary conditions in divertors, electric field effects, atomic and molecular data issues, impurity transport in the divertor region, poloidally localized power dissipation (MARFEs and dense gas targets), helium ash removal, and neutral transport. The report ends with a summary of selected problems of particular significance and a brief bibliography of survey articles and related conference proceedings.

  6. A novel approach to magnetic divertor configuration design

    NASA Astrophysics Data System (ADS)

    Blommaert, M.; Baelmans, M.; Dekeyser, W.; Gauger, N. R.; Reiter, D.

    2015-08-01

    Divertor exhaust system design and analysis tools are crucial to evolve from experimental fusion reactors towards commercial power plants. In addition to material research and dedicated vessel geometry design, improved magnetic configurations can contribute to sustaining the diverted heat loads. Yet, computational design of the magnetic divertor is a challenging process involving a magnetic equilibrium solver, a plasma edge grid generator and a computationally demanding plasma edge simulation. In this paper, an integrated approach to efficient sensitivity calculations is discussed and applied to a set of slightly reduced divertor models. Sensitivities of target heat load performance to the shaping coil currents are directly evaluated. Using adjoint methods, the cost for a sensitivity evaluation is reduced to about two times the simulation cost of one specific configuration. Further, the use of these sensitivities in an optimal design framework is illustrated by a case with realistic Joint European Torus (JET) configurational parameters.

  7. Plasma transport in a simulated magnetic-divertor configuration

    SciTech Connect

    Strawitch, C. M.

    1981-03-01

    The transport properties of plasma on magnetic field lines that intersect a conducting plate are studied experimentally in the Wisconsin internal ring D.C. machine. The magnetic geometry is intended to simulate certain aspects of plasma phenomena that may take place in a tokamak divertor. It is found by a variety of measurements that the cross field transport is non-ambipolar; this may have important implications in heat loading considerations in tokamak divertors. The undesirable effects of nonambipolar flow make it preferable to be able to eliminate it. However, we find that though the non-ambipolarity may be reduced, it is difficult to eliminate entirely. The plasma flow velocity parallel to the magnetic field is found to be near the ion acoustic velocity in all cases. The experimental density and electron temperature profiles are compared to the solutions to a one dimensional transport model that is commonly used in divertor theory.

  8. Toroidally symmetric plasma vortex at tokamak divertor null point

    NASA Astrophysics Data System (ADS)

    Umansky, M. V.; Ryutov, D. D.

    2016-03-01

    Reduced MHD equations are used for studying toroidally symmetric plasma dynamics near the divertor null point. Numerical solution of these equations exhibits a plasma vortex localized at the null point with the time-evolution defined by interplay of the curvature drive, magnetic restoring force, and dissipation. Convective motion is easier to achieve for a second-order null (snowflake) divertor than for a regular x-point configuration, and the size of the convection zone in a snowflake configuration grows with plasma pressure at the null point. The trends in simulations are consistent with tokamak experiments which indicate the presence of enhanced transport at the null point.

  9. Turbulence studies in Tokamak boundary plasmas with realistic divertor geometry

    SciTech Connect

    Xu, X.Q.

    1998-10-14

    Results are presented from the 3D nonlocal electromagnetic turbulence code BOUT [1] and the linearized shooting code BAL[2] to study turbulence in tokamak boundary plasmas and its relationship to the L-H transition, in a realistic divertor plasma geometry. The key results include: (1) the identification of the dominant, resistive X-point mode in divertor geometry and (2) turbulence suppression in the L-H transition by shear in the ExB drift speed, ion diamagnetism and finite polarization. Based on the simulation results, a parameterization of the transport is given that includes the dependence on the relevant physical parameters.

  10. Non-ambipolar transport in a magnetic divertor

    SciTech Connect

    Strawitch, C M; Emmert, G A

    1980-02-01

    Plasma transport is studied in a simulated magnetic divertor in the Wisconsin single ring DC machine. The transport perpendicular and parallel to the magnetic field is shown to be non-ambipolar by a variety of measurements, but can be forced to be ambipolar by an appropriately designed divertor target plate. The density profile in the scrape-off zone agrees with the predictions of a one-dimensional diffusion equation that assumes classical cross-field transport and plasma flow parallel to the field at the local ion acoustic velocity.

  11. Divertor for a linear fusion device

    NASA Astrophysics Data System (ADS)

    Ryutov, D. D.; Yushmanov, P. N.; Barnes, D. C.; Putvinski, S. V.

    2016-03-01

    Linear fusion devices can use large magnetic flux flaring in the end tanks to reduce the heat load on the end structures. In order to reduce parallel electron heat loss, one has to create conditions where the neutral gas density in the end tanks is low, as otherwise cold electrons produced by the ionization of the neutrals would cool down the core plasma electrons. The processes determining the neutral gas formation and spatial distribution are analysed for the case where neutrals are formed by the surface recombination of the outflowing plasma. The conditions under which the cooling of the core plasma is negligible are formulated.

  12. Thermal Analysis of the Divertor Primary Heat Transfer System Piping During the Gas Baking Process

    SciTech Connect

    Yoder Jr, Graydon L; Harvey, Karen; Ferrada, Juan J

    2011-02-01

    A preliminary analysis has been performed examining the temperature distribution in the Divertor Primary Heat Transfer System (PHTS) piping and the divertor itself during the gas baking process. During gas baking, it is required that the divertor reach a temperature of 350 C. Thermal losses in the piping and from the divertor itself require that the gas supply temperature be maintained above that temperature in order to ensure that all of the divertor components reach the required temperature. The analysis described in this report was conducted in order to estimate the required supply temperature from the gas heater.

  13. RAMI Analysis for Designing and Optimizing Tokamak Cooling Water System (TCWS) for the ITER's Fusion Reactor

    SciTech Connect

    Ferrada, Juan J; Reiersen, Wayne T

    2011-01-01

    U.S.-ITER is responsible for the design, engineering, and procurement of the Tokamak Cooling Water System (TCWS). TCWS is designed to provide cooling and baking for client systems that include the first wall/blanket, vacuum vessel, divertor, and neutral beam injector. Additional operations that support these primary functions include chemical control of water provided to client systems, draining and drying for maintenance, and leak detection/localization. TCWS interfaces with 27 systems including the secondary cooling system, which rejects this heat to the environment. TCWS transfers heat generated in the Tokamak during nominal pulsed operation - 850 MW at up to 150 C and 4.2 MPa water pressure. Impurities are diffused from in-vessel components and the vacuum vessel by water baking at 200-240 C at up to 4.4 MPa. TCWS is complex because it serves vital functions for four primary clients whose performance is critical to ITER's success and interfaces with more than 20 additional ITER systems. Conceptual design of this one-of-a-kind cooling system has been completed; however, several issues remain that must be resolved before moving to the next stage of the design process. The 2004 baseline design indicated cooling loops that have no fault tolerance for component failures. During plasma operation, each cooling loop relies on a single pump, a single pressurizer, and one heat exchanger. Consequently, failure of any of these would render TCWS inoperable, resulting in plasma shutdown. The application of reliability, availability, maintainability, and inspectability (RAMI) tools during the different stages of TCWS design is crucial for optimization purposes and for maintaining compliance with project requirements. RAMI analysis will indicate appropriate equipment redundancy that provides graceful degradation in the event of an equipment failure. This analysis helps demonstrate that using proven, commercially available equipment is better than using custom-designed equipment

  14. Loop-to-loop coupling.

    SciTech Connect

    Warne, Larry Kevin; Lucero, Larry Martin; Langston, William L.; Salazar, Robert Austin; Coleman, Phillip Dale; Basilio, Lorena I.; Bacon, Larry Donald

    2012-05-01

    This report estimates inductively-coupled energy to a low-impedance load in a loop-to-loop arrangement. Both analytical models and full-wave numerical simulations are used and the resulting fields, coupled powers and energies are compared. The energies are simply estimated from the coupled powers through approximations to the energy theorem. The transmitter loop is taken to be either a circular geometry or a rectangular-loop (stripline-type) geometry that was used in an experimental setup. Simple magnetic field models are constructed and used to estimate the mutual inductance to the receiving loop, which is taken to be circular with one or several turns. Circuit elements are estimated and used to determine the coupled current and power (an equivalent antenna picture is also given). These results are compared to an electromagnetic simulation of the transmitter geometry. Simple approximate relations are also given to estimate coupled energy from the power. The effect of additional loads in the form of attached leads, forming transmission lines, are considered. The results are summarized in a set of susceptibility-type curves. Finally, we also consider drives to the cables themselves and the resulting common-to-differential mode currents in the load.

  15. Taming the plasma-material interface with the snowflake divertor.

    SciTech Connect

    Soukhanovskii, V A

    2015-04-24

    Experiments in several tokamaks have provided increasing support for the snowflake configuration as a viable tokamak heat exhaust concept. This white paper summarizes the snowflake properties predicted theoretically and studied experimentally, and identifies outstanding issues to be resolved in existing and future facilities before the snowflake divertor can qualify for the reactor interface.

  16. Modeling results for a linear simulator of a divertor

    SciTech Connect

    Hooper, E.B.; Brown, M.D.; Byers, J.A.; Casper, T.A.; Cohen, B.I.; Cohen, R.H.; Jackson, M.C.; Kaiser, T.B.; Molvik, A.W.; Nevins, W.M.; Nilson, D.G.; Pearlstein, L.D.; Rognlien, T.D.

    1993-06-23

    A divertor simulator, IDEAL, has been proposed by S. Cohen to study the difficult power-handling requirements of the tokamak program in general and the ITER program in particular. Projections of the power density in the ITER divertor reach {approximately} 1 Gw/m{sup 2} along the magnetic fieldlines and > 10 MW/m{sup 2} on a surface inclined at a shallow angle to the fieldlines. These power densities are substantially greater than can be handled reliably on the surface, so new techniques are required to reduce the power density to a reasonable level. Although the divertor physics must be demonstrated in tokamaks, a linear device could contribute to the development because of its flexibility, the easy access to the plasma and to tested components, and long pulse operation (essentially cw). However, a decision to build a simulator requires not just the recognition of its programmatic value, but also confidence that it can meet the required parameters at an affordable cost. Accordingly, as reported here, it was decided to examine the physics of the proposed device, including kinetic effects resulting from the intense heating required to reach the plasma parameters, and to conduct an independent cost estimate. The detailed role of the simulator in a divertor program is not explored in this report.

  17. Neoclassical and Initial Divertor-Geometry Tests of COGENT

    NASA Astrophysics Data System (ADS)

    Cohen, R. H.; Dorf, M.; Compton, J. C.; Dorr, M.; Rognlien, T. D.; Colella, P.; McCorquodale, P.; Angus, J.; Krasheninnikov, S.

    2012-03-01

    COGENT is a full-f continuum kinetic code being developed for study of edge physics phenomena in tokamaks. The code is distinguished by 4th order conservative discretization and mapped multiblock grid technology to handle the geometric complexity of the tokamak edge. We discuss a number of recent neoclassical results in closed-flux-surface geometry, in particular self-consistent neoclassical simulations with increasingly complete collision operators (Lorentz, full test-particle, and adding model momentum- and energy-conserving terms). We also examine the effects of strong radial electric fields on neoclassical transport and decay of geodesic acoustic modes (GAM's). The code is being upgraded to full single-null divertor geometry, with numerical geometric coefficients imported from an external MHD equilibrium calculation. We discuss several initial tests of the divertor code: advection of phase-space blobs through the x-point region, and neoclassical transport and flows in the presence of divertor losses. We also summarize progress on code-development activities needed to complete the divertor code.

  18. Theoretical design of a compact energy recovering divertor

    NASA Astrophysics Data System (ADS)

    Baver, D. A.

    2015-11-01

    An energy recovering divertor (ERD) is a type of plasma direct converter (PDC) designed to fit in the divertor channel of a tokamak. Such a device reduces the heat load to the divertor plate by converting a portion of it into electrical energy. This recovered energy can then be used for auxiliary heating and current drive, fundamentally altering the relationship between scientific and engineering breakeven and reducing dependence on bootstrap current. Previous work on the ERD concept focused on amplification of Alfven waves in a manner similar to a free-electron laser. While conceptually straightforward, this concept was also bulky, thus limiting its applicability to existing tokamak experiments. A design is presented for an ERD based on sheath-localized waves. This makes possible a device sufficiently compact to fit in the divertor channel of many existing tokamak experiments, and moreover requires no new shaping coils to achieve the desired magnetic geometry or topology. In addition, incidental advantages of this concept will be discussed.

  19. Dynamically limiting energy consumed by cooling apparatus

    DOEpatents

    Chainer, Timothy J.; David, Milnes P.; Iyengar, Madhusudan K.; Parida, Pritish R.; Schmidt, Roger R.; Schultz, Mark D.

    2015-05-26

    Cooling apparatuses and methods are provided which include one or more coolant-cooled structures associated with an electronics rack, a coolant loop coupled in fluid communication with one or more passages of the coolant-cooled structure(s), one or more heat exchange units coupled to facilitate heat transfer from coolant within the coolant loop, and N controllable components associated with the coolant loop or the heat exchange unit(s), wherein N.gtoreq.1. The N controllable components facilitate circulation of coolant through the coolant loop or transfer of heat from the coolant via the heat exchange unit(s). A controller is coupled to the N controllable components, and dynamically adjusts operation of the N controllable components, based on Z input parameters and one or more specified constraints, to provide a specified cooling to the coolant-cooled structure(s), while limiting energy consumed by the N controllable components, wherein Z.gtoreq.1.

  20. Dynamically limiting energy consumed by cooling apparatus

    DOEpatents

    Chainer, Timothy J.; David, Milnes P.; Iyengar, Madhusudan K.; Parida, Pritish R.; Schmidt, Roger R.; Schultz, Mark D.

    2015-06-09

    Cooling methods are provided which include providing: one or more coolant-cooled structures associated with an electronics rack, a coolant loop coupled in fluid communication with one or more passages of the coolant-cooled structure(s), one or more heat exchange units coupled to facilitate heat transfer from coolant within the coolant loop, and N controllable components associated with the coolant loop or the heat exchange unit(s), wherein N.gtoreq.1. The N controllable components facilitate circulation of coolant through the coolant loop or transfer of heat from the coolant via the heat exchange unit(s). A controller is also provided to dynamically adjust operation of the N controllable components, based on Z input parameters and one or more specified constraints, and provide a specified cooling to the coolant-cooled structure(s), while limiting energy consumed by the N controllable components, wherein Z.gtoreq.1.

  1. Passive cooling system for top entry liquid metal cooled nuclear reactors

    DOEpatents

    Boardman, Charles E.; Hunsbedt, Anstein; Hui, Marvin M.

    1992-01-01

    A liquid metal cooled nuclear fission reactor plant having a top entry loop joined satellite assembly with a passive auxiliary safety cooling system for removing residual heat resulting from fuel decay during shutdown, or heat produced during a mishap. This satellite type reactor plant is enhanced by a backup or secondary passive safety cooling system which augments the primary passive auxiliary cooling system when in operation, and replaces the primary cooling system when rendered inoperative.

  2. Diagnostic options for radiative divertor feedback control on NSTX-Ua)

    NASA Astrophysics Data System (ADS)

    Soukhanovskii, V. A.; Gerhardt, S. P.; Kaita, R.; McLean, A. G.; Raman, R.

    2012-10-01

    A radiative divertor technique is used in present tokamak experiments and planned for ITER to mitigate high heat loads on divertor plasma-facing components (PFCs) to prevent excessive material erosion and thermal damage. In NSTX, a large spherical tokamak with lithium-coated graphite PFCs and high divertor heat flux (qpeak ⩽ 15 MW/m2), radiative divertor experiments have demonstrated a significant reduction of divertor peak heat flux simultaneously with good core H-mode confinement using pre-programmed D2 or CD4 gas injections. In this work diagnostic options for a new real-time feedback control system for active radiative divertor detachment control in NSTX-U, where steady-state peak divertor heat fluxes are projected to reach 20-30 MW/m2, are discussed. Based on the NSTX divertor detachment measurements and analysis, the control diagnostic signals available for NSTX-U include divertor radiated power, neutral pressure, spectroscopic deuterium recombination signatures, infrared thermography of PFC surfaces, and thermoelectric scrape-off layer current. In addition, spectroscopic "security" monitoring of possible confinement or pedestal degradation is recommended. These signals would be implemented in a digital plasma control system to manage the divertor detachment process via an actuator (impurity gas seeding rate).

  3. Diagnostic options for radiative divertor feedback control on NSTX-U

    SciTech Connect

    Soukhanovskii, V. A.; McLean, A. G.; Gerhardt, S. P.; Kaita, R.; Raman, R.

    2012-10-15

    A radiative divertor technique is used in present tokamak experiments and planned for ITER to mitigate high heat loads on divertor plasma-facing components (PFCs) to prevent excessive material erosion and thermal damage. In NSTX, a large spherical tokamak with lithium-coated graphite PFCs and high divertor heat flux (q{sub peak} Less-Than-Or-Slanted-Equal-To 15 MW/m{sup 2}), radiative divertor experiments have demonstrated a significant reduction of divertor peak heat flux simultaneously with good core H-mode confinement using pre-programmed D{sub 2} or CD{sub 4} gas injections. In this work diagnostic options for a new real-time feedback control system for active radiative divertor detachment control in NSTX-U, where steady-state peak divertor heat fluxes are projected to reach 20-30 MW/m{sup 2}, are discussed. Based on the NSTX divertor detachment measurements and analysis, the control diagnostic signals available for NSTX-U include divertor radiated power, neutral pressure, spectroscopic deuterium recombination signatures, infrared thermography of PFC surfaces, and thermoelectric scrape-off layer current. In addition, spectroscopic 'security' monitoring of possible confinement or pedestal degradation is recommended. These signals would be implemented in a digital plasma control system to manage the divertor detachment process via an actuator (impurity gas seeding rate).

  4. Manufacturing and testing of a Be/OFHCCu divertor module

    NASA Astrophysics Data System (ADS)

    Araki, M.; Youchison, D. L.; Akiba, M.; Watson, R. D.; Sato, K.; Suzuki, S.

    1996-10-01

    Beryllium, carbon-based materials and tungsten are considered as plasma facing materials for the next generation of fusion machines such as the international thermonuclear experimental reactor (ITER). Beryllium is one of the primary candidate materials because of its low atomic number and lack of tritium codeposition. However, joining of a beryllium armor to a copper heat sink remains a critical problem due to the formation of brittle intermetallics at the interface. To address this concern, the Japan Atomic Energy Research Institute manufactured a beryllium/Cu divertor module with Cr and Ni diffusion barriers. This Be/Cu module was tested in the electron beam test system of Sandia National Laboratories in the framework of the US—Japan Fusion Collaboration. The divertor module consisted of four beryllium tiles, 25 mm × 25 mm, and a square copper heat sink with convolutions like a screw nut inside the coolant channel. To evaluate the integrity of the brazed bonds under various heat fluxes, beryllium tiles of two different thicknesses, 2 and 10 mm, were bonded to the copper heat sink. Cooling conditions of 10 m/s water flow velocity at 1 MPa, and a water inlet temperature of 20°C were selected based on the thermal analysis. During high heat flux testing the 10 mm thick Be tiles detached at an absorbed heat flux around 5 MW/m 2 for several shots due to flaws at the braze joint confirmed by optical observation after manufacturing. One of the 2 mm thick Be tiles failed after 550 cycles at the steady state heat flux of 6.5 MW/m 2. Most likely the failure was caused by brittleness at the interface caused by the presence of BeCu intermetallics.

  5. Stochastic Cooling

    SciTech Connect

    Blaskiewicz, M.

    2011-01-01

    Stochastic Cooling was invented by Simon van der Meer and was demonstrated at the CERN ISR and ICE (Initial Cooling Experiment). Operational systems were developed at Fermilab and CERN. A complete theory of cooling of unbunched beams was developed, and was applied at CERN and Fermilab. Several new and existing rings employ coasting beam cooling. Bunched beam cooling was demonstrated in ICE and has been observed in several rings designed for coasting beam cooling. High energy bunched beams have proven more difficult. Signal suppression was achieved in the Tevatron, though operational cooling was not pursued at Fermilab. Longitudinal cooling was achieved in the RHIC collider. More recently a vertical cooling system in RHIC cooled both transverse dimensions via betatron coupling.

  6. Modeling of divertor geometry effects in China fusion engineering testing reactor by SOLPS/B2-Eirene

    SciTech Connect

    Zhao, M. L.; Chen, Y. P.; Li, G. Q.; Luo, Z. P.; Guo, H. Y.; Institute of Plasma Physics, Chinese Academy of Science, Hefei 230031; General Atomics, P.O. Box 85608, San Diego, California 92186 ; Ye, M. Y.; Institute of Plasma Physics, Chinese Academy of Science, Hefei 230031 ; Tendler, M.

    2014-05-15

    The China Fusion Engineering Testing Reactor (CFETR) is currently under design. The SOLPS/B2-Eirene code package is utilized for the design and optimization of the divertor geometry for CFETR. Detailed modeling is carried out for an ITER-like divertor configuration and one with relatively open inner divertor structure, to assess, in particular, peak power loading on the divertor target, which is a key issue for the operation of a next-step fusion machine, such as ITER and CFETR. As expected, the divertor peak heat flux greatly exceeds the maximum steady-state heat load of 10 MW/m{sup 2}, which is a limit dictated by engineering, for both divertor configurations with a wide range of edge plasma conditions. Ar puffing is effective at reducing divertor peak heat fluxes below 10 MW/m{sup 2} even at relatively low densities for both cases, favoring the divertor configuration with more open inner divertor structure.

  7. Transmutation and activation analysis for divertor materials in a HCLL-type fusion power reactor

    NASA Astrophysics Data System (ADS)

    Fischer, U.; Pereslavtsev, P.; Möslang, A.; Rieth, M.

    2009-04-01

    The activation and transmutation of tungsten and tantalum as plasma facing materials was assessed for a helium cooled divertor irradiated in a typical fusion power reactor based on the use of Helium-cooled Lithium Lead (HCLL) blankets. 3D activation calculations were performed by applying a programme system linking the Monte Carlo transport code MCNP and the fusion inventory code FISPACT through an appropriate interface. Special attention was given to the proper treatment of the resonance shielding of tungsten and tantalum by using reaction rates provided directly by MCNP on the basis of continuous energy activation cross-section data. It was shown that the long-term activation behaviour is dominated by activation products of the assumed tramp material while the short-term behaviour is due to the activation of the stable Ta and W isotopes. The recycling limit for remote handling of 100 mSv/h can be achieved after decay times of 10 and 50 years for Ta and W, respectively. The elemental transmutation rates of Ta and W were shown to be on a moderate level for the HCLL-type fusion power reactor.

  8. Development and qualification of a bulk tungsten divertor row for JET

    NASA Astrophysics Data System (ADS)

    Mertens, Ph.; Altmann, H.; Hirai, T.; Philipps, V.; Pintsuk, G.; Rapp, J.; Riccardo, V.; Schweer, B.; Uytdenhouwen, I.; Samm, U.

    2009-06-01

    A bulk tungsten divertor row has been developed in the frame of the ITER-like Wall project at JET. It consists of 96 tiles grouped in 48 modules around the torus. The outer strike point is located on those tiles for most of the ITER-relevant, high triangularity plasmas. High power loads (locally up to 10-20 MW/m 2) and erosion rates are expected, even a risk of melting, especially with the transients or ELM loads. These are demanding conditions for an inertially cooled design as prescribed. A lamella design has been selected for the tungsten, arranged to control the eddy and halo current flows. The lamellae must also withstand high temperature gradients (2200 to 220 °C over 40 mm height), without overheating the supporting carrier (600-700 °C maximum). As a consequence of the tungsten emissivity, the radiative cooling drops appreciably in comparison with the current CFC tiles, calling for interleaved plasma scenarios in terms of performance. The compromise between shadowing and power handling is discussed, as well as the consequences for operation. Prototypes have been exposed in TEXTOR and in an electron beam facility (JUDITH-2) to the nominal power density of 7 MW/m 2 for 10 s and, in addition, to higher loads leading to surface temperatures above 2000 °C.

  9. Innovative tokamak DEMO first wall and divertor material concepts

    NASA Astrophysics Data System (ADS)

    Wong, C. P. C.

    2009-06-01

    ITER has selected Be as the first wall and C and W as the divertor surface materials. When extrapolated to the DEMO design, C and Be layers will not be suitable due to radiation damage. The remaining material, W, could also suffer radiation damage from helium ion implantation and experience blistering at the first wall and form submicron fine structure at the divertor. In this paper we introduce a new concept called the boron W-mesh (BW-mesh) in which B is infiltrated into a W-mesh. The goal is to use a thin coating of B to protect the W-mesh from helium ion damage and to maintain a sufficient amount of B to protect the W from transient events like edge localized modes (ELMs) and disruptions. Critical issues and corresponding development of this BW-mesh concept have been identified, including the need for real time boronization.

  10. Investigation of tokamak solid divertor target options. Final report

    SciTech Connect

    McMurray, J.M.

    1981-05-26

    Analysis of survival constraints on the design of solid targets for tokamak bundle divertors is presented. Previous target design efforts are reviewed. Considerations of heat removal, surface erosion, and fatigue life are included in a generalized design window methodology which facilitates target selection. Using subcooled water as coolant, eight possible target materials are evaluated for use in tubular and plate targets as substrates, coatings, and claddings. Subject to the severe environment of the tokamak plasma, the most promising conventional designs are identified. A thermally bonded, mechanically unbonded laminated design is proposed and evaluated as a target design well suited to the divertor target environment. Due to fatigue and sputtering erosion this configuration has limited life, but appears to constitute an upper bound for the capabilities of a solid target design. Needs for experimental work are identified.

  11. Detached divertor operation in DIII-D helium plasmas

    SciTech Connect

    Hill, D. N., LLNL

    1998-05-01

    This paper presents results from operating helium plasmas in DIII-D in which helium gas puffing is used to reduce the peak divertor heat flux by factors of four or more. The threshold density for achieving these conditions is nearly the same as for deuterium plasmas, which is surprising given the fact that lack of chemical sputtering reduces the carbon concentration in the plasma by more than a factor of five. Spectroscopic analysis shows that helium becomes the primary radiation in these plasmas, which is possible because, unlike carbon, it is the primary species present. These plasmas differ from the usual partially detached divertor (PDD) plasmas in that there is no concomitant reduction in target plate ion flux with target plate heat flux in the scrape off later outside the separatrix.

  12. An automated approach to magnetic divertor configuration design

    NASA Astrophysics Data System (ADS)

    Blommaert, M.; Dekeyser, W.; Baelmans, M.; Gauger, N. R.; Reiter, D.

    2015-01-01

    Automated methods based on optimization can greatly assist computational engineering design in many areas. In this paper an optimization approach to the magnetic design of a nuclear fusion reactor divertor is proposed and applied to a tokamak edge magnetic configuration in a first feasibility study. The approach is based on reduced models for magnetic field and plasma edge, which are integrated with a grid generator into one sensitivity code. The design objective chosen here for demonstrative purposes is to spread the divertor target heat load as much as possible over the entire target area. Constraints on the separatrix position are introduced to eliminate physically irrelevant magnetic field configurations during the optimization cycle. A gradient projection method is used to ensure stable cost function evaluations during optimization. The concept is applied to a configuration with typical Joint European Torus (JET) parameters and it automatically provides plausible configurations with reduced heat load.

  13. Divertor heat and particle control experiments on the DIII-D tokamak

    SciTech Connect

    Mahdavi, M.A; Baker, D.R.; Allen, S.L.

    1994-05-01

    In this paper we present a summary of recent DIII-D divertor physics activity and plans for future divertor upgrades. During the past year, DIII-D experimental effort was focused on areas of active heat and particle control and divertor target erosion studies. Using the DIII-D Advanced Divertor system we have succeeded for the first time to control the plasma density and demonstrate helium exhaust in H-mode plasmas. Divertor heat flux control by means of D{sub 2} gas puffing and impurity injection were studied separately and in, both cases up to a factor of five reduction of the divertor peak heat flux was observed. Using the DiMES sample transfer system we have obtained erosion data on various material samples in well diagnosed plasmas and compared the results with predictions of numerical models.

  14. An experimental investigation of the post-CHF enhancement factor for a prototypical ITER divertor plate with water coolant

    SciTech Connect

    Marshall, T.D.; Watson, R.D.; McDonald, J.M.

    1995-09-01

    In an off-normal event, water-cooled copper divertor plates in the International Thermonuclear Experimental Reactor (ITER) may either experience heat loads beyond their design basis, or the normal heat loads may be accompanied by low coolant pressure and velocity. The purpose of this experiment was to illustrate that during one-sided heating, as in ITER, a copper divertor plate with the proper side wall thickness, at low system pressure and velocity can absorb without failing an incident heat flux, q{sub i}, that significantly exceed the value, q{sub i}{sup CHF}, which is associated with local CHF at the wall of the coolant channel. The experiment was performed using a 30 kW electron beam test system for heating of a square cross-section divertor heat sink with a smooth circular channel of 7.63 mm diameter. The heated width, length, and wall thickness were 16, 40, and 3 mm, respectively. Stable surface temperatures were observed at incident heat fluxes greater than the local CHF point, presumably due to circumferential conduction around the thick tube walls when q{sub i}{sup CHF} was exceeded. The Post-CHF enhancement factor, {eta}, is defined as the ratio of the incident burnout heat flux, q{sub i}{sup BO}, to q{sub i}{sup CHF}. For this experiment with water at inlet conditions of 70{degrees}C, 1 m/s, and 1 MPa, q{sub i}{sup CHF} and q{sub i}{sup BO} were 600 and 1100 W/cm{sup 2}, respectively, which gave an {eta} of 1.8.

  15. Experimental evaluation of cooling efficiency of the high performance cooling device

    NASA Astrophysics Data System (ADS)

    Nemec, Patrik; Malcho, Milan

    2016-06-01

    This work deal with experimental evaluation of cooling efficiency of cooling device capable transfer high heat fluxes from electric elements to the surrounding. The work contain description of cooling device, working principle of cooling device, construction of cooling device. Experimental part describe the measuring method of device cooling efficiency evaluation. The work results are presented in graphic visualization of temperature dependence of the contact area surface between cooling device evaporator and electronic components on the loaded heat of electronic components in range from 250 to 740 W and temperature dependence of the loop thermosiphon condenser surface on the loaded heat of electronic components in range from 250 to 740 W.

  16. Cooling system with automated seasonal freeze protection

    DOEpatents

    Campbell, Levi A.; Chu, Richard C.; David, Milnes P.; Ellsworth, Jr., Michael J.; Iyengar, Madhusudan K.; Simons, Robert E.; Singh, Prabjit; Zhang, Jing

    2016-05-24

    An automated multi-fluid cooling system and method are provided for cooling an electronic component(s). The cooling system includes a coolant loop, a coolant tank, multiple valves, and a controller. The coolant loop is at least partially exposed to outdoor ambient air temperature(s) during normal operation, and the coolant tank includes first and second reservoirs containing first and second fluids, respectively. The first fluid freezes at a lower temperature than the second, the second fluid has superior cooling properties compared with the first, and the two fluids are soluble. The multiple valves are controllable to selectively couple the first or second fluid into the coolant in the coolant loop, wherein the coolant includes at least the second fluid. The controller automatically controls the valves to vary first fluid concentration level in the coolant loop based on historical, current, or anticipated outdoor air ambient temperature(s) for a time of year.

  17. DiMES divertor erosion experiments on DIII-D

    SciTech Connect

    Whyte, D.G.; Brooks, J.N.; Wong, C.P.C.; West, W.P.; Bastasz, R.; Wampler, W.R.; Rubinstein, J.

    1996-06-01

    The DiMES (Divertor Material Evaluation Studies) mechanism allows insertion of material samples to the lower divertor floor of the DIII-D tokamak. The main purpose of these studies is to measure erosion rates and redeposition mechanisms under tokamak divertor plasma conditions in order to obtain a physical understanding of the erosion/redeposition processes and to determine its implications for fusion power plant plasma facing components. Thin metal films of Be, W, V, and Mo, were deposited on a Si depth-marked graphite sample and exposed to the steady-state outer strike point on DIII-D. A variety of surface analysis techniques are used to determine the erosion/redeposition of the metals and the carbon after 5--15 seconds of exposure. These short exposure times ensure controlled exposure conditions and the extensive array of DIII-D divertor diagnostics provide a well characterized plasma for modeling efforts. Erosion rates and redeposition lengths are found to decrease with the atomic number of the metallic species, as expected. Under these conditions, the peak net erosion rate for carbon is {approximately} 4 nm/s, with the erosion following the ion flux profile. Comparisons of the measured carbon erosion with REDEP code calculations show good agreement for both the absolute net erosion rate and its spatial variation. Measured erosion rates of the metals are smaller than predicted for sputtering from a bare metal surface, apparently due to effects of carbon deposition on the metal surface. Visible spectroscopic measurements of singly ionized Be have determined that the erosion process reaches steady-state during the exposure.

  18. Waves in Solar Coronal Loops

    NASA Astrophysics Data System (ADS)

    Wang, T. J.

    2016-02-01

    The corona is visible in the optical band only during a total solar eclipse or with a coronagraph. Coronal loops are believed to be plasma-filled closed magnetic flux anchored in the photosphere. Based on the temperature regime, they are generally classified into cool, warm, and hot loops. The magnetized coronal structures support propagation of various types of magnetohydrodynamics (MHD) waves. This chapter reviews the recent progress made in studies based on observations of four types of wave phenomena mainly occurring in coronal loops of active regions, including: flare-excited slow-mode waves; impulsively excited kink-mode waves; propagating slow magnetoacoustic waves; and ubiquitous propagating kink (Alfvénic) waves. This review not only comprehensively discusses these waves and coronal seismology but also topics that are newly emerging or hotly debated in order to provide the reader with useful guidance on further studies.

  19. Tokamak power exhaust with the snowflake divertor: Present results and outstanding issues

    DOE PAGESBeta

    Soukhanovskii, V. A.; Xu, X.

    2015-09-15

    Here, a snowflake divertor magnetic configuration (Ryutov in Phys Plasmas 14(6):064502, 2007) with the second-order poloidal field null offers a number of possible advantages for tokamak plasma heat and particle exhaust in comparison with the standard poloidal divertor with the first-order null. Results from snowflake divertor experiments are briefly reviewed and future directions for research in this area are outlined.

  20. Coronal Loop Evolution Observed with AIA and Hi-C

    NASA Technical Reports Server (NTRS)

    Mulu-Moore, Fana; Winebarger, A.; Cirtain, J.; Kobayashi, K.; Korreck, K.; Golub, L.; Kuzin. S.; Walsh, R.; DeForest, C.; DePontieu, B.; Weber, M.

    2012-01-01

    Despite much progress toward understanding the dynamics of the solar corona, the physical properties of coronal loops are not yet fully understood. Recent investigations and observations from different instruments have yielded contradictory results about the true physical properties of coronal loops. In the past, the evolution of loops has been used to infer the loop substructure. With the recent launch of High Resolution Coronal Imager (Hi-C), this inference can be validated. In this poster we discuss the first results of loop analysis comparing AIA and Hi-C data. We find signatures of cooling in a pixel selected along a loop structure in the AIA multi-filter observations. However, unlike previous studies, we find that the cooling time is much longer than the draining time. This is inconsistent with previous cooling models.

  1. Impurity Transport in a Simulated Gas Target Divertor

    NASA Astrophysics Data System (ADS)

    Blush, L. M.; Luckhardt, S.; Seraydarian, R.; Whyte, D.; Conn, R. W.; Schmitz, L.

    1997-11-01

    Previous simulated gas target divertor experiments in the PISCES-A linear plasma device (n <= 3 × 10^19 m-3, kTe <= 20 eV) indicated enhanced impurity retention near the target in comparison to a high recycling divertor regime. A 1 1\\over2-D fluid modeling code suggested that impurities are impeded from transporting away from the target by friction with the neutral and ionized hydrogen. In recent experiments with a PISCES-A ``slot-type'' divertor configuration, we have implemented a spectroscopic detection system to measure the axial density profiles of several impurity charge states. Moreover, we envision adding two extended cylindrical baffles spanning a pumped vacuum section to achieve strong differential pumping. This arrangement will isolate the plasma source from the gas target region and allow us to seed the background hydrogen plasma with higher impurities concentrations and investigate a regime dominated by impurity radiation. In preliminary design experiments, PISCES-A was successfully operated with an electrically isolated, copper baffle (d=5 cm, l=33.5 cm) mounted to reduce the vacuum conductance between the source and target regions. This work supported by US-DoE contract DE-FG03-95ER-54301.

  2. Analytical calculations for impurity seeded partially detached divertor conditions

    NASA Astrophysics Data System (ADS)

    Kallenbach, A.; Bernert, M.; Dux, R.; Reimold, F.; Wischmeier, M.; ASDEX Upgrade Team

    2016-04-01

    A simple analytical formula for the impurity seeded partially detached divertor operational point has been developed using 1D modelling. The inclusion of charge exchange momentum loss terms improves the 1D modelling for ASDEX Upgrade conditions and its extrapolation to larger devices. The investigations are concentrated around a partially detached divertor working point of low heat flux and an electron temperature around 2.5 eV at the target which are required to maintain low sputtering rates at a tungsten target plate. An experimental formula for the onset of detachment by nitrogen seeding in ASDEX Upgrade is well reproduced, and predictions are given for N, Ne and Ar seeding for variable device size. Moderate deviations from a linear {{P}\\text{sep}}/R size dependence of the detachment threshold are seen in the modelling caused by upstream radiation at longer field line lengths. The presented formula allows the prediction of the neutral gas or seed impurity pressure which is required to achieve partial detachment for a given {{P}\\text{sep}} in devices with a closed divertor similar to the geometry in ASDEX Upgrade.

  3. UEDGE modeling of divertor geometry effects in NSTX

    NASA Astrophysics Data System (ADS)

    Izacard, Olivier; Soukhanovskii, Vlad; Scotti, Filippo

    2015-11-01

    We report efforts toward the modeling of divertor geometry effects using the fluid code UEDGE and NSTX experimental equilibria with different X-point heights. A variation of the geometry generates a competition between the poloidal magnetic flux expansion, which reduces the peak of the deposited heat flux and homogenizes its profile at divertor plates, and the proximity of the X-point to the divertor plates, which decreases the connection length and increases the peak heat flux. Our simulations use fixed fraction of carbon impurity, poloidally and radially constant transport coefficients, and high recycling boundary conditions, with a scan of density and pressure boundary conditions, and impurity fraction. Our simulations support the experimental observation that the poloidal flux expansion dominates the deposit heat flux over the parallel connection length effect. In opposite to experimental observation, detachment seems independent to the elevation. Improvement of the model is required. Supported by U.S. Department of Energy Contract No. DE-AC52-07NA27344.

  4. Assessment of issues for the MAST divertor biasing experiment

    NASA Astrophysics Data System (ADS)

    Helander, P.; Cohen, R. H.; Fielding, S.; Ryutov, D.

    2001-10-01

    A biasing experiment is being undertaken in the MAST scrape-off layer; the goal is to induce intense convection by a toroidally alternating biasing of divertor tiles. This would lead to a thickening of the SOL and a reduction of the heat load on the divertor plates. In addition, by studying the reaction of a plasma to a varying bias, one can collect new information regarding pre-existing SOL turbulence. We consider the following issues: 1. The bias amplitude required to produce significant SOL broadening; 2. Excitation of shear-flow turbulence in convective cells; 3. The role of magnetic shear; 4. Effects of electrostatic sheaths at the divertor plates; 5. Redistribution of heat fluxes during biasing. We show that a significant effect of the biasing on the SOL structure can be reached at relatively small bias voltages 30 V. We also show that the potential perturbations will be limited to a zone between the X-point and the biased tiles, and will be essentially decoupled from the main SOL plasma. Preliminary experimental results may be shown.

  5. Fast reciprocating Langmuir probe for the DIII-D divertor

    SciTech Connect

    Watkins, J.G.; Hunter, J.; Tafoya, B.; Ulrickson, M.; Watson, R.D.; Moyer, R.A.; Cuthbertson, J.W.; Gunner, G.; Lehmer, R.; Luong, P.; Hill, D.N.; Mascaro, M.; Robinson, J.I.; Snider, R.; Stambaugh, R.

    1997-01-01

    A new reciprocating Langmuir probe was used to measure density and temperature profiles, ion flow, and potential fluctuation levels from the lower divertor floor up to the X point on the DIII-D Tokamak. This probe is designed to make fast (2 kHz swept, 20 kHz Mach, 500 kHz Vfloat) measurements with 2 mm spatial resolution in the region where the largest gradients on the plasma open flux tubes are found and therefore provide the best benchmarks for scrap-off layer and divertor numerical models. Profiles are constructed using the 300 ms time history of the probe measurements during the 25 cm reciprocating stroke. Both single and double null plasmas can be measured and compared with a 20 Hz divertor Thomson scattering system. The probe head is constructed of four different kinds of graphite to optimize the electrical and thermal characteristics. Electrically insulated pyrolytic graphite rings act as a heat shield to absorb the plasma heat flux on the probe shaft and are mounted on a carbon/carbon composite core for mechanical strength. The Langmuir probe sampling tips are made of a linear carbon fiber composite. The mechanical, electrical, data acquisition, and power supply systems will be described. Initial measurements will also be presented. {copyright} {ital 1997 American Institute of Physics.}

  6. Island Divertor Plate Modeling for the Compact Toroidal Hybrid Experiment

    NASA Astrophysics Data System (ADS)

    Hartwell, G. J.; Massidda, S. D.; Ennis, D. A.; Knowlton, S. F.; Maurer, D. A.; Bader, A.

    2015-11-01

    Edge magnetic island divertors can be used as a method of plasma particle and heat exhaust in long pulse stellarator experiments. Detailed power loading on these structures and its relationship to the long connection length scrape off layer physics is a new Compact Toroidal Hybrid (CTH) research thrust. CTH is a five field period, l = 2 torsatron with R0 = 0 . 75 m, ap ~ 0 . 2 m, and | B | <= 0 . 7 T. For these studies CTH is configured as a pure stellarator using a 28 GHz, 200 kW gyrotron operating at 2nd harmonic for ECRH. We report the results of EMC3-EIRENE modeling of divertor plates near magnetic island structures. The edge rotational transform is varied by adjusting the ratio of currents in the helical and toroidal field coils. A poloidal field coil adjusts the shear of the rotational transform profile, and width of the magnetic island, while the phase of the island is rotated with a set of five error coils producing an n = 1 perturbation. For the studies conducted, a magnetic configuration with a large n = 1 , m = 3 magnetic island at the edge is generated. Results from multiple potential divertor plate locations will be presented and discussed. This work is supported by U.S. Department of Energy Grant No. DE-FG02-00ER54610.

  7. Experimental study on sintered powder wick loop heat pipe

    NASA Astrophysics Data System (ADS)

    Putra, Nandy; Saputra, Bimo, M. Iqbal; Irwansyah, Ridho; Wayan, S. Nata

    2012-06-01

    Increased of heat flux generated by electronic equipment in particular components of a computer (CPU) should always be accompanied with a good cooling in order to achieve optimal operating capability with a high level of reliability. The use of loop heat pipes in thermal management of electronic cooling becomes one of alternative solution. Before LHPs are implemented as an alternative cooling method for electronic device, a quantity of reliability factors should be considered and evaluated such as wick structure and material, type of working fluid, long term life tests, and other tests. The purposes of this experimental study are to examine and analyze the application of sintered copper powder as a wick on a loop heat pipe, type of cooling system on LHP and the orientation of LHP. The performace of nanofluid as working fluid in loop heat pipe were also investigated in this experiment. The performance of the loop heat pipe was also affected by the type of condenser; the water cooled loop heat pipe has the highest temperature reducing value compared to the heat sink fan. The orientation of loop heat pipe also affected the performance of loop heat pipe. This proved that gravity and capillary pressure affecting the performance of loop heat pipes. Temperature differences between the evaporator and condenser sections with nanofluids were less that pure water, i.e. thermal resistance of the LHP when charged with nanofluids was less. It makes nanofluid attractive as working fluid in loop heat pipe technology.

  8. Active control of divertor asymmetry on EAST by localized D2 and Ar puffing

    NASA Astrophysics Data System (ADS)

    Wang, Dongsheng; Guo, Houyang; Wang, Huiqian; Luo, Guangnan; Wu, Zhenwei; Wu, Jinhua; Gao, Wei; Wang, Liang; Li, Qiang; East Team

    2011-03-01

    The divertor asymmetry in particle and power fluxes has been investigated on the EAST superconducting tokamak [S. Wu and EAST Team, Fusion Eng. Des. 82, 463 (2007)] for both single null (SN) and double null (DN) divertor configurations. D2 and Ar puffing at various divertor locations has also been explored as an active means to reduce peak target heat load and control divertor asymmetry. For SN, peak heat load on the outer divertor target is 2-3 times that on the inner divertor target under typical ohmic plasma conditions. DN operation leads to a stronger in-out asymmetry favoring the outer divertor. D2 and Ar puffing promotes partial detachment near the strike points, greatly reducing peak target heat load (over 50%), while the far-SOL divertor plasma remains attached. What is remarkable is that the particle flux is even increased away from the strike points when the B×∇B drift is directed toward the divertor target, thus facilitating particle removal.

  9. Comparison of Ne and Ar seeded radiative divertor plasmas in JT-60U

    NASA Astrophysics Data System (ADS)

    Nakano, T.

    2015-08-01

    In H-mode plasmas with Ne, Ar and a mixture of Ne and Ar injection, the divertor radiation power fractions amongst these impurities in addition to an intrinsic impurity, C, are investigated. In plasmas with the inner divertor plasma attached, carbon is the biggest radiator, whichever impurity, Ne, Ar or a mixture of Ar and Ne is injected. In contrast, in plasmas with the inner divertor plasma detached, Ne is the biggest radiator due to a significantly high recombination radiation from Ne VIII. Ar is always a minor contributor in plasmas with the inner divertor both attached and detached.

  10. Active control of divertor asymmetry on EAST by localized D{sub 2} and Ar puffing

    SciTech Connect

    Wang Dongsheng; Luo Guangnan; Guo Houyang; Wang Huiqian; Wu Zhenwei; Wu Jinhua; Gao Wei; Wang Liang; Li Qiang

    2011-03-15

    The divertor asymmetry in particle and power fluxes has been investigated on the EAST superconducting tokamak [S. Wu and EAST Team, Fusion Eng. Des. 82, 463 (2007)] for both single null (SN) and double null (DN) divertor configurations. D{sub 2} and Ar puffing at various divertor locations has also been explored as an active means to reduce peak target heat load and control divertor asymmetry. For SN, peak heat load on the outer divertor target is 2-3 times that on the inner divertor target under typical ohmic plasma conditions. DN operation leads to a stronger in-out asymmetry favoring the outer divertor. D{sub 2} and Ar puffing promotes partial detachment near the strike points, greatly reducing peak target heat load (over 50%), while the far-SOL divertor plasma remains attached. What is remarkable is that the particle flux is even increased away from the strike points when the Bx{nabla}B drift is directed toward the divertor target, thus facilitating particle removal.