Facility Status 05/20/2015

Transcription

1 Facility Status 05/20/2015

2 Outline Machine Status Alternator Engineering Systems Diagnostic Systems In-vessel work Short Term Schedule SOFE

3 Machine Status Alternator to full speed on 04/08/15 Pump-down on 04/17/15 C-Mod began plasma operations on 04/30/15 after one day of power system testing Discharge on first plasma attempt Full length discharges by the end of the day Currently nearing the end of the plasma conditioning phase of operation Clean plasma facing surfaces Reduce hydrogen levels Boronization next week will mark entry into research ops

4 MIT Alternator Repair and Inspection Rotor passed all electrical tests Stator passed all electrical tests Flywheel passed UT tests Bearings refurbished All 1 st and 2 nd turns of the #1 and #2 coils of all poles were inspected Instrumentation has been reinstalled and calibrated Checks of all protection systems completed including Is-limiters (explosive fuses) Rotor balance checks completed Rotor on turning gear by 03/16/15 Insurance covers all repair costs

5 Engineering Systems ICRF Four new enhanced anode FPA tubes on order (1 st tube to ship 04/30/2015, 2 nd 05/30/2015) Waiting for CPI to update us on delivery dates Manufacturing of anodes has delayed shipment New grid regulators (from PPPL) have been installed and are operational. All transmitters successfully brought back into operation for FY2015 campaign Antennas undergoing conditioning: 2.75 MW from D&E and 1.5 MW from J thus far D and E are limited by weak damping (H/D) FA J antenna had control issue resulting in false positives 22 kv in vacuum Grid Regulators Reactive Bonding

6 Engineering Systems LH Operation Launcher was refurbished during up-to-air and calibrations were checked 800 kw coupled to plasma thus far Reactive Bonding

7 Diagnostic Systems

8 Update on RFQ accelerator refurbishment in support of AIMS David Terry Ed Johnson Zach Hartwig Brandon Sorbom Leigh Ann Kesler Bill Beck Pete Stahle Rick Murray Slides Prepared by Zach Hartwig and Dave Terry

9 Refurbishment of RFQ ion source is nearing completion; first full system tests expected mid-june Review: The RFQ accelerator is the core of the AIMS diagnostic Difficulties achieving full energy, full current beam led to full inspection; revealed need for substantial internal maintenance, alignment (end-2014) Careful, methodical work by C-Mod team for complete refurbishment is now underway; we hope for full system tests by mid-june 2015 Complete disassembly, documentation, drawings completed RF cavity completely cleaned, restored, and modeled in RF software Ion source and optics characterization, alignment, optimization Full 3D laser-based alignment of all components Consulting closely with world-experts in RFQ design AccSys (original manufacturer of this RFQ) Bob Hamm (original designer of this RFQ)

10 Cross section drawings of the RFQ accelerator RFQ RF Cavity (work completed early 2015) Ion source and lens (work to-be complete by mid-june) Components of accelerator need to be very precisely aligned (a few mils)

11 The RFQ RF cavity has been completely cleaned and restored as close to original state as possible After cleaning Before cleaning All RF characterization matches original specification; cavity now bright shiny conducting copper

12 The RFQ beam imager installed in the RFQ source Faraday Cup BNC Out Phosphor Screen/Faraday Cup BNC Out Phosphor screen can be moved along axis Digital camera measures position of beam CMM measures position of flange faces Pearson Current Monitor BNC Out

13 Fitting program developed for rapid 2D Gaussian fit of beam spot; enables precision beam location in space

14 Complete refurbishment of RFQ ion source is nearing completion; first full system tests expected mid-june Near-terms steps: All necessary beam images acquired (mid-may) Full 3D beam reconstruction, analysis complete (end-may) Complete precision alignment of complete system and reassembly in the experimental hall (early-mid June) Full beam tests (mid-to-late June) Provided the above goes as planned, the RFQ would be reinstalled on C-Mod in July and AIMS would commence operation soon afterwards

15 MSE Upgrade Polychromators Polychromators Rack Mounted Greatly improved background subtraction Improved detectors and filters System installed and ready for operation as DNB comes back online Upgrade to MSE analysis software to handle new hardware and much more data is ongoing

16 O-mode Reflectometer Power Supply Upgrade New consolidated power supply designed by PPPL was delivered and successfully powered up for the 50, 60, and 75 GHz O-mode reflectometer system. This upgrade simplifies the reflectometer design, and minimizes noise generation arising from multiple ground points. New regulator boards designed by C. Kung, PPPL, are used to regulate the voltages to active microwave components such as Gunn Oscillators and mixers.

17 A new probe head is under fabrication to mount magnetic probes to measure parallel wavenumber of LH waves Six magnetic probes will be mounted on a radially moveable probe system. Probes were designed at the University of Japan (Takahiro Shinya and Yuichi Takase) Vacuum-compatible probes and the probe head are under fabrication. The probe head will be mounted on the existing Surface Science Station [R. Ochoukov, MIT PhD Thesis 2013]. The electronics that will down-convert from 4.6 GHz to 25 MHz have been built. Fast speed digitizer (100MS/sec) will directly digitize the signals. Digitizer Slit Shield Probe Array

18 Spectral MSE Will it work on ITER? Spectral MSE On ITER, may out-perform contemporary spectral MSE diagnostics due to larger Stark splitting Suggested as an alternative to standard MSE on ITER Alcator C-Mod is uniquely capable of testing spectral MSE at ITER levels of Stark splitting due to large toroidal field Proof-of-principle exp was promising: Spectrum yielded pitch angle that is consistent with kinetic E-FIT Miniproposal (MP763) approved for experiment with improved optics at ITER-like Stark splitting

19 In-Vessel Work Primary goals Refurbish plasma facing components and diagnostics Install new advanced divertor diagnostics Improve power handling capability of the outer divertor Diagnostic calibration

20 In-Vessel Work New outer divertor rail probes designed, manufactured, and installed flush probes should eliminate melting, the most common probe failure modes probes extended toroidally to have well-defined projected area, minimizing effects of sheath expansion on interpretation Initial results promising, detailed analysis underway Divertor heat flux instrumentation refurbished surface thermocouples now have more reliable triaxial cable new Langmuir probes installed, modified surface area to meet current limitations of future divertor mirror Langmuir probe system Inner divertor Langmuir probes refurbished new Langmuir probes installed, replacing melted and shorted probes new in vessel cabling, replacing damaged cabling Inner wall scanning Langmuir probes refurbished Upper divertor Langmuir probes refurbished

21 In-Vessel Work Lower hybrid launcher Langmuir probes inspected Limiter retarding field analyzer refurbished New surface science station ( S 3 ) Langmuir probes designed and manufactured Limiter and divertor tile thermocouples inspected, repaired where possible New servomotor drive upgrade for the horizontal scanning probe system assembly. Testing underway Circuit for real time calculation of divertor heat flux from surface thermocouples for feedback control of impurity seeding designed, built, and tested New mirror Langmuir probe system under construction to drive outer divertor Langmuir probes: Will enable feedback control on divertor plasma conditions as well as unprecedented time-resolution of divertor fluctuation measurements Polarimeter shutter successfully repaired

22 In-Vessel Work Outer divertor modules have been shimmed to provide a small toroidal twist All outer divertor modules were removed, tiles refurbished, shims fitted and modules reinstalled Provides a ski jump to reduce heat flux at the edges of the modules Ski Jump

23 In-Vessel Work New Rail Probe Arrays New rail probe arrays installed for FY2015 campaign Power flux density has proved to be too great for standard button probes Rail probes designed to be much more robust (flush to surface) High spatial resolution: increased coverage to 21 locations (from 10 previously)

24 In-Vessel Work Initial Rail-Probe Profile Data Three plasma parameters from the probe current-voltage characteristic: electron temperature, ion saturation current, and floating potential Plot from one time-slice, each point from an individual probe (scatter due to fluctuations) Twice the spatial resolution as previous array allows for finer spatial resolution without strike point sweeps

25 Short Term Schedule Planning for 12 weeks of research operation in FY2015 Currently completing plasma conditioning phase of operation Mon 5/18/15 ID Task Name Duration Start Finish 1 Pumpdown 0 days Fri 4/17/15 Fri 4/17/15 2 Leakcheck/Bake/ECDC 11 days Sat 4/18/15 Tue 4/28/15 3 Plasma Condition 15 days Wed 4/29/15 Fri 5/22/15 4 Plasma Ops FY days Tue 5/26/15 Fri 6/26/15 5 Maintenance 8 days Mon 6/29/15 Thu 7/9/15 6 Plasma Ops FY days Fri 7/10/15 Thu 8/13/15 7 Maintenance 9 days Fri 8/14/15 Wed 8/26/15 8 Plasma Ops FY days Thu 8/27/15 Wed 9/30/ APS Meeting (2015) 5 days Mon 11/16/15 Fri 11/20/15 March 2015 April 2015 May 2015 June 2015 July 2015 August 2015 September 2015 October 2015 November /17 12 Weeks

26 C-Mod Well Represented at SOFE (May 31 st to June 4 th Austin, Texas) Invited Talk (Plenary) Smaller & Sooner: Exploiting New Technologies for Fusion's Development D. Whyte Invited Talks Alcator C-Mod and ADX: Research on the High-Field Pathway to Fusion Energy B. LaBombard RF Enabling Technologies for Reactor Relevant Devices S. J. Wukitch, P. T. Bonoli, Y. Lin, G. Wallace, S. Shiraiwa, S. G. Baek, R. R. Parker, W. M. Beck, R. Vieira Engineering the Alcator C-Mod MSE Diagnostic: Solutions to Reactor-Relevant Diagnostic Challenges R. T. Mumgaard, S. D. Scott The Engineering and Operation of AIMS, an In-Situ Accelerator-Based Diagnostic for Plasma Facing Components Z. S. Hartwig, H. S. Barnard, B. N. Sorbom, L. A. Kesler, W. M. Burke, J. Doody, R. C. Lanza, P. W. Stahle, D. R. Terry, R. F. Vieira, D. G. Whyte, L. Zhou Vulcan

27 SOFE Papers and Posters Analysis of ICRF Ferrite Tuner P. Koert, L. Zhou, S. Wukitch, A. Binus, E. Fitzgerald, A. Pfeiffer, R. Murray RF, Disruption and Thermal Analyses of East Antennas L. Zhou, W. K. Beck, P. Koert, Q. X. Yang*, C. M. Qin*, X. J. Zhang*, J. Doody, R. F. Vieira, S. J. Wukitch, R. S. Granetz, J. H. Irby, Y. P. Zhao* * Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui, P.R. China The Engineering Design of ARC: A Compact, High Field, Fusion Nuclear Science Facility and Demonstration Power Plant B. N. Sorbom, J. Ball, T. R. Palmer, F. J. Mangiarotti, J. M. Sierchio, P. Bonoli, C. Kasten, D. Sutherland, H. S. Barnard, C. B. Haakonsen, J. Goh, C. Sung, D. G. Whyte Power Systems Analysis and Design for ADX D. R. Terry, J. Irby, W. Cochran, S. Wolfe, B. LaBombard, W. Burke, R. Vieira Structural Analysis of High-Field-Side Rf Antennas During a Disruption on the Advanced Divertor Experiment (ADX) J. Doody, B. LaBombard, R. Leccacorvi, S. Shiraiwa, R. Vieira, G. M. Wallace, S. J. Wukitch, J. H. Irby Novel Vacuum Vessel & Coil System Design for the Advanced Divertor Experiment (ADX) R. F. Vieira, J. Doody, W. K. Beck, L. Zhou, R. Leccacorvi, B. LaBombard, R. S. Granetz, S. M. Wolfe, J. H. Irby, S. J. Wukitch, D. R. Terry, G. M. Wallace, R. R. Parker ADX

28 SOFE Papers and Posters High Field Side Launch of Lower Hybrid Waves: a Scoping Study for ADX G. M. Wallace, S. Shiraiwa, S. G. Baek, P. T. Bonoli, A. D. Kanojia, P. Koert, B. L. LaBombard, R. Leccacorvi, R. R. Parker, D. R. Terry, R. Vieira, S. J. Wukitch Advanced ICRF Antenna for ADX S. J. Wukitch, P. T. Bonoli, Y. Lin, W. M. Beck, R. Vieira Real-Time High-Field Measurement of Joint Resistance in the Alcator C-Mod Toroidal Field Magnet W. M. Burke, A. Kanojia, J. A. Stillerman High Field Launcher Design ~5cm The Shoelace Antenna: a Device for Inductively Coupling to Low Frequency, Short Wavelength Fluctuations in the Plasma Boundary T. Golfinopoulos, W. M. Burke, B. LaBombard, R. R. Parker, W. C. Parkin, P. P. Woskov Shoelace Antenna 28

29 EOT

30 C-Mod FY2015 run planning presented by R. Granetz Alcator C-Mod quarterly review 2015/05/20

31 C-Mod FY2015 operation Budgeted for 12 research run weeks (48 physics run days) Next year s (FY2016) guidance budget provides for a maximum of 5 weeks of operation, and then C-Mod is scheduled to cease operation, so there is intense pressure on run time Plan to devote much run time to topics that C-Mod is uniquely capable of addressing, including: High B-field (8 tesla) High performance I-mode Lower hybrid (2015 JRT is on off-axis current drive) ICRF field-aligned antenna 56 run days worth of highest priority experiments are competing for run time 2/4

32 C-Mod FY2015 highest priority run days requested Topic/Group Run Days Transport 10.5 Pedestal 12.6 Boundary 11.5 LH 4.0 ICRF 6.0 MHD/Disruptions 5.0 ITER specific requests 6.4 (not included in other topics) Total research days for 56.0 (14.0 weeks) highest priority experiments Research target for FY2015 is 12 weeks. NOTE: This does not include 38.0 other high priority run days requested 3/4

33 C-Mod operations: current status Late April pumped down; baked out 04/29 to 05/22 plasma startup, conditioning, discharge cleaning, ICRF conditioning, LH conditioning Week of 05/26 boronization; recovery 06/01 begin physics research operations June - Sept three run blocks of 4 weeks each, with two maintenance periods interspersed (~1.5 weeks each) First run block has B drift downward Plan to switch field & current direction later in campaign (for I-mode studies and relativistic electron studies) 4/4

34 DIII-D: Subcontract status and research plans J. Hughes on behalf of the C-Mod Team C-Mod Quarterly Review 20 May 2015

35 GA subcontract for MIT research on DIII-D: Timeline 2013: Subcontract negotiations began with intent of funding research in FY14 11/2013 1/2014: Work was performed under GA-MIT Letter Agreement, while final subcontract being negotiated 1/2014: Subcontract put on hiatus following passing of FY14 appropriations 10/2014: Discussions re-opened on subcontract 11/2014: MIT and DIII-D research contacts began communicating on potential projects, key personnel 4/2015: Scope of subcontract, deliverables agreed upon by MIT + DIII-D technical staff Currently: GA Statement of Work (SOW) is in management approval stage RFP is expected to go to MIT in 1 2 weeks MIT proposal will be submitted 1 2 weeks after receipt of RFP MIT is prepared to resume subcontract funded collaboration on DIII-D soon after C-Mod/DIII-D Collaboration Status, 22 Jan

36 MIT and DIII-D have agreed on scope of proposal (4/22) Multi-channel turbulent transport in the tokamak core (D. Ernst, N. Howard, A. White) Experimental emphasizing impurity, momentum, electron energy transport Diagnostic development; Simulation and model validation Pedestal physics in high-performance ELM-suppressed regimes (J. Hughes, J. Walk) Characterization + modeling of recent and proposed QH-mode, I-mode experiments Disruption prediction and warning (R. Granetz) Disruption warning algorithm development for implementation in DIII-D PCS Development and delivery of RF hardware to optimize plasma performance (S. Wukitch) Design, engineering and fabrication of hardware for high-power helicon antenna Participate in installation on DIII-D (2016) C-Mod/DIII-D Collaboration Status, 22 Jan

37 Subcontract work prelude to enhanced DIII-D collaboration Near-term work is a beginning to larger collaboration as outlined in MIT 5-year proposal (in review) Sub-contract will allow near-term addition of 3 FTE of PSFC staff to DIII-D research 2 new MIT postdocs (on-site at DIII-D) 2 3 MIT graduate students Themes and topics align between near-term and longterm proposals, with significant expansion after 2016 C-Mod/DIII-D Collaboration Status, 22 Jan

38 Signing subcontract will enable and accelerate DIII-D collaboration Transport: Darin Ernst has been nominated for a 2015 APS-DPP invited talk on DIII-D research into TEM turbulence Disruption warning: SQL database initiated for identification of DIII-D disruptions, similar to those developed for C-Mod and EAST Intent is to develop disruption prediction algorithms Helicon hardware Specifications have been determined for coaxial vacuum feedthroughs, transition components Cost of fabrication being determined: DIII-D funds will be added to the subcontract to cover these additional costs Histogram of current quench time for DIII-D disruptions (1999-present) --R. Granetz C-Mod/DIII-D Collaboration Status, 22 Jan

39 International Collaboration on Control and Extension of ITER and Advanced Scenarios to Long Pulse in EAST and KSTAR P. T. Bonoli On behalf of the MIT Team: S. G. Baek, R. S. Granetz, E. Edlund, A. E. Hubbard, Y. Lin, R. R. Parker, M. Porkolab, J. E. Rice, S. Shiraiwa, J. Stillerman, G. M. Wallace, and J. C. Wright DoE Teleconference May 20, 2015

40 Task 1: Extension of the I-Mode scenario to EAST & KSTAR EAST (A. Hubbard; X. Gao, T. Zhang, Z. X. Liu, G. Q. Li, Y. Yang, D.F. Kong, and X. Han): An experimental proposal for Development and study of I-mode on EAST was revised and submitted in January Anticipate scheduling for next physics campaign; Hubbard is making plans to participate on site. This will include current, density and power scans, and also the novel idea of adding RMP coils to increase particle transport. KSTAR (A. Hubbard & J. Ko): Initial attempts in October, 2014 to produce I-mode were unsuccessful due to problems with position control in USN configuration (drsep and inner gap). Will try again in 2015 when KSTAR starts up. PCS work by GA as part of this collaboration will assist the KSTAR team in resolving these issues so that experiments in 2015 can provide more definitive results.

41 Task 2. Long Pulse Disruption Free Control Primary activity has been the installment of a disruption database on EAST, which is now fully functional and automatically populated with new disruptions. Studies of relativistic runaway electrons (RE's) during disruptions on EAST (R. Granetz): Working with one of the EAST physicists who is studying this on EAST. Planning to visit EAST this summer while they are operating in order to participate in some of the RE experiments. At ASIPP, Granetz is working with several graduate students who are doing disruption-related research. One student is developing disruption prediction/warning algorithms based on neutral networks. Granetz will be hosting this student during a month-long visit to MIT in August/September at the request of his advisor, Jiangang Li.

42 Task 3. Diagnostic and Actuator Development for Scenario Extension Mode conversion flow drive (MCFD) studies on EAST with an ICRF actuator (Y. Lin, Xinjin Zhang, Jiale Chen): Submitted a mini-proposal to perform (MCFD) experiments on EAST. Y. Lin (MIT) worked with Xinjun Zhang and Jiale Chen, on including TORIC ICRF simulation results into an ICRF MCFD calculation by J. Chen [J. Chen and Z. Gao, Phys. Plasmas 21, (2014) and Z. Gao, J. Chen and N.J. Fisch, Phys. Rev. Lett 110, (2013)]. Chen's theoretical work has shown some qualitative agreement with C-Mod MCFD results, and his theory will be used to guide EAST research in MCFD. Y. Lin is planning a trip to EAST in summer 2015 (likely in July), to participate in ICRF work in general and MCFD research on EAST with a possible second trip to EAST in combination with ITPA-IOS meeting in October. ICRF coupling and absorption studies for EAST (E. Edlund, S. Wukitch, M. Porkolab): E. Edlund has been using the TORIC ICRF solver to perform simulations for a new four strap antenna to project the k // needed for optimal coupling (E. M. Edlund, P. Bonoli, M. Porkolab, S. J. Wukitch, paper at the 21 st Topical Conference on Radio-frequency Power in Plasmas, April 2015, Lake ArrowHead, CA).

43 Task 3. Diagnostic and Actuator Development for Scenario Extension Simulation studies of LHCD in EAST (S. Shiraiwa, P. T. Bonoli, J. C. Wright; Boijang Ding, Miaohui Li, Cheng Yang): Using GENRAY / CQL3D can reproduce the peaked hard x-ray and current density profiles in EAST experiments by slightly broadening the incident LH power spectrum (5% of power put in a lobe at n // = 2.75). Same approach has been used to successfully simulate C-Mod LHCD experiments [S. Shiraiwa, Invited Talk at the 21st Topical Conference on Radio-frequency Power in Plasmas, April 2015, Lake ArrowHead, CA)]. EAST simulation studies also being carried out now in collaboration with Y. Peysson from CEA / IRFM using the LUKE / C3PO model. Plan to participate in LHCD Physics experiments on EAST in 2015: Perform experiments to examine source frequency dependence of LHCD (2.45 GHz vs. 4.6 GHz) as a function of density by monitoring PDI and hard x-ray emission (S. Baek, R. Parker). Study poloidal dependence of LHCD by separately powering off mid-plane rows of 4.6 GHz LH launcher (R. Parker, G. Wallace). Continue analysis of LHCD experiments using GENRAY / TORLH / CQL3D.

44 International Collab: Development of long-pulse RF actuators and Operational Techniques for High Z PFC Plasma operations expected from mid June to end of August. Under vacuum since end of April Repaired tungsten divertor. Second 4 MW of NBI has been installed. ECRF is limited to 0.5 MW per gyrotron (~1 MW source) for coming campaign. Campaign planning: Number of proposals submitted by EAST deadline (27 January). Had internal planning meeting 5/ Overall campaign goals are: Develop long-pulse/steady-state, high performance scenario with a low momentum input and Develop long-pulse (>100s) scenario with a high electron temperature (>4.5 kev). Wukitch - DoE Quarterly

45 For EAST ICRF, Improving Coupling is Critical EAST antenna coupling has low coupling efficiency. Antenna coupling efficiency is estimated by. I port antenna: k =14.4 m 1 and n ecut ~9x10 18 m 3 x~8 cm =0.28 B port antenna: k =12.6 m 1 and n ecut ~6.4x10 18 m 3. x~8 cm =0.33 C Mod: k =11 m 1 and 14 m 1 n ecut ~5x10 18 m 3 x~2 cm ~0.75 Electron Density [m -3 x10 19 ] Cutoff Density ~9x10 18 m T, Ip= 373 ka, r/a Operate 4 strap antenna in current drive [0, ] and /3 phase [0, ] to improve coupling efficiency. CD phase k =7.2 m -1,n ecut ~2.2x10 18 m -3,and =0.53. /3 phase k =4.8 m -1,n ecut ~1x10 18 m -3,and =0.65. For new antenna, attempt to minimize k while maintaining good SPA. An experimental proposal to investigated antenna loading versus antenna phase is planned for the upcoming campaign. Wukitch - DoE Quarterly

46 Core Absorption: High Single Pass Absorption for H Minority Estimate minority H heating scenario single pass absorption with analytic formula and include impact of energetic ions. 1 kev and 5 kev curves represent thermal plasma single pass absorption. 10 kev tail shows how quickly the minority energy impacts single pass aborption. Single pass absorption (%) kev is typical minority ion energy. For reference, we show C-Mod values - which have demonstrated high heating efficiency. For k =4.8 m -1, the single pass absorption is similar to C-Mod conditions and expect good absorption. For k =9 m -1, single pass absorption is approaching 40% for 1 kev plasma. Wukitch - DoE Quarterly C-Mod k =10 m -1 EAST k =4.8 m -1 EAST k =9 m kev 5.0 kev kev 10.0 kev 5.0 kev 1.0 kev n H /n e (%)

47 EAST Conceptual FA Antenna: General Specifications ICRF antenna power capability: 4.2 MW into ELMy H-mode Bandwidth: MHz transmitter bandwidth 2.5 T operation H minority is 38 MHz, 2nd harmonic is 76 MHz 3 T operation H minority cyclotron frequency = 45.6 MHz Maximum average electric field is not to exceed 15 kv/cm where E B. Maximum voltage 45 kv. Mechanical stress based upon disruption: 0.2 T Bake out temperature: 300 C Preferred antenna strap configuration is end fed, center grounded RF antenna limiter: m 5 mm behind plasma limiter Antenna to operate 100 s. Current straps, Faraday shield and protection tiles to be actively cooled. Coolant: water Coolant pressure: 3 atm Coolant flow velocity: 2 m/s Wukitch - DoE Quarterly

48 Current Strap Layout for Conceptual EAST FA Antenna Antenna straps are to normal to total magnetic field, field line pitch is 7. Current strap is end fed-center grounded. Strap length 700 mm I and B antenna straps are ~640 mm. Current straps are 350 mm on center. Corresponds to k ~9 m -1. Coupling efficiency ~45% assuming distance to cutoff is unchanged. n ecut ~4x10 18 m -3 bottom of pedestal Antenna is to replace I port antenna. Antenna structure will occupy wall space between H and J port without interfering with H or J port. Limits strap spacing; thus coupling efficiency. Wukitch - DoE Quarterly

49 Vacuum Transmission Line Behind Back Plate For end fed/center grounded, coaxial to strip line feeds are a challenge. If the feedthrus are moved closer to the back plate, new feedthrus will be required. Design will be similar to the feedthrus used on the C-Mod FA antenna. Position coax feeds to maximize clearance between neighbors. Work was presented at 21 st Power in Plasmas Top. Conf. on RF Wukitch - DoE Quarterly

50 Summary of Activity: Divertor/Disruptions We worked with EAST on understanding where divertor cooling channel leaks are located and investigate a cause. Failure of connection pipes occurred during machine bake out. Cluster of failures at the interface block may be related to poor electron beam welds from one of two manufacturers. Four Chinese visitors were here to review tungsten divertor and discuss plans for hot tungsten divertor. Presented fully aligned and hot divertor designs for C-Mod. Major challenge for EAST hot divertor design is thermal expansion. EAST divertor is fixed at 3 locations that prevent expansion. Wukitch - DoE Quarterly

51 Summary of Activity: Disruptions Integrated filament reconstruction is available. Correct geometry and input/output data stored in MDS trees. Critical to engineering studies on divertor electromagnetic studies. Request for 7000 existing discharges prompted ICRF group to properly evaluate and store RF power signals in central repository. Work on disruptions (Bob Granetz) has been published in Chinese Physics B. Characterization of plasma current quench during disruption in EAST tokamak Work is based on the disruption database (first sql database at EAST) implemented by Granetz. Utilizes MFIL for flux surface reconstruction during disruption (Granetz contribution). Bob Granetz visited EAST in March. Proposed experiments on disruptions and runaway electron physics for upcoming campaign. Wukitch - DoE Quarterly

52 Summary of Activity: Low P regimes (I-mode) Dr. Zixi Lui (ASIPP Postdoc) has started BOUT++ analysis of C-Mod I- modes, in collaboration with X. Xu (LLNL) and C-Mod. MIT supplied equilibrium and pedestal profiles for a well diagnosed, high confinement discharge. Simulated turbulence using progressively more complete physics in BOUT++ 3-field, linear simulations confirmed the expected peeling ballooning stability, consistent with lack of ELMs. Linear simulations indicated that I-mode turbulence likely has contributions from both drift Alfven waves and ballooning modes. Full nonlinear simulations have recently been done which show fluctuation spectra quite similar in location, frequency and wavenumber to measurements of the weakly coherent mode. Simulations show that particle diffusivity from these fluctuations is larger than thermal diffusivity, which is close to the experimental value Work was presented at EU-US Transport Task Force meeting in May An experimental proposal for Development and study of I-mode on EAST is planned for the upcoming campaign. Wukitch - DoE Quarterly