Alcator C-Mod Second Quarter FY07 DoE Review

Transcription

1 Alcator C-Mod Second Quarter FY07 DoE Review May 7, 2007 Facility status: Jim Irby ICRF status: Earl Marmar (for Steve Wukitch) Cryopump status: Brian LaBombard LHRF status: Ron Parker Research campaign summary and plans: Steve Wolfe

2 Facility Status and Plans DoE Quarterly Review 05/07/07 1

3 Status Alcator C-Mod is currently in operation (details from Steve Wolfe) Before operation began, major activities completed included Upper divertor cryopump in-vessel installation W-tile toroidal ring in outer divertor Rotation of Long Pulse DNB (7 o toroidal) Many diagnostic upgrades and several new installations 2

4 Updates: Operations W-Tile Belt Installed Complete toroidal ring 8 tungsten plates per module ITER relevant activity Tile Module Installed tiles 3

5 Updates: Operations Lower Hybrid Control and Protection System Continuing to work with vendor of high speed CPCI data acquisition card to provide programming area for interlock signals Programmable trip levels will save hours of in-cell activity Ron Parker will detail operation Lower Hybrid Stainless Steel Couplers Procurement of new couplers complete Alumina windows in-house Preparations being made for brazing Fast-Ferrite Tuner development and installation complete with promising first operation 4

6 Updates: Diagnostics Retro/shutter probes Two new inner wall scanning probes have been installed Six retro-reflectors for the polarimeter installed with new pneumatic shutter Dual FIR laser system on order Beam position feedback system being developed 5

7 Updates: Diagnostics Upgrades to CXRS, fast scanning probes, x-ray spectrometers, Thomson scattering, bolometry, Penning gauges, polarimeter prototype, plasma video system K-Port Horizontal Science Surface Station installed (S 3 ) Microbalances measure deposition (radial, perp, 0.1 to 1 nm resolution) Langmuir probes measure density NeSOX SiLi S 3 Polarimeter Beamline 6

8 New X-ray Spectrometer Spatially Resolving HIgh REsolution X-ray spectrometer (SR HiReX) Improved time response, and spatial resolution and coverage Spherically bent crystal spectrometer looking at H & He-like Argon emissions lines Is now providing impurity temperature and rotation profiles for r/a ~<0.8 He-like Crystal Gate Valve B-port H-like Crystal He-like Detectors H-like Detector Spectrometer Layout Pilatus X-ray Detector Module 7

9 Updates: Diagnostics Rotation of Long Pulse DNB Trapping of beam neutrals in TF ripple field resulted in anomalous signals in MSE diagnostic DNB removed so that stand could be modified DNB horizontal flange removed for modification of beamline entry angle Some diagnostic views were optimized for new beam angle 8

10 Historically, C-Mod MSE beam-into-gas calibrations have been strongly anomalous 30 Channel: 2 MSE measured pitch angle (degrees) perpendicular beam (2005) y=x Actual pitch angle (degrees) 2006: H. Yuh (Nova Photonics) proposes mechanism: spurious emission by 'secondary' beam neutrals with long residence time in MSE field-of-view due to perpendicular beam injection.

11 Rotating the diagnostic beam ~7 o significantly reduces the anomaly 30 MSE measured pitch angle (degrees) Channel: 2 perpendicular beam (2005) 7 o rotated beam (2007) y=x Actual pitch angle (degrees) These results have motivated ITER to re-consider the orientation of its diagnostic neutral beam. J. Ko (PSFC) S. Scott (PPPL) H. Yuh (Nova Photonics)

12 Plans Plasma research operation for 15 weeks Plasma cleanup phase complete Ready for boronization Addition of vertical field to localize deposition S 3 diagnostic measures deposition and plasma density Cryopump operation FFT operation Continue design of new E-plane launcher and fabrication of new klystron cart (4 klystrons) Two lower hybrid launchers From 3 to 4 MW of source power 2 nd ICRF 4-strap antenna design/fab will continue 9

13 List of Completed Up-to-Air Tasks General Ops: Service Liquid Nitrogen System Service LN 2 vent duct Service Power Systems Sparker Development Service/Repair PFCs Replace HEAT TC Scanner Replace HV reed relays in TF Scanner Data system upgrades Network upgrades Diagnostics/Invessel: NESOX move to k-hor 10" flange microbalance installation (S 3 ) bolometer upgrade mods to b-hor for hirex/new detector MSE cals/checks/mods flapper removal/cover plate installation W-Tile belt installation Upper Chamber Cryopump installation outer divertor test tiles (B, CBN, W) shutter for polarimeter retros Mo/Ceramic polarimeter retros TCI feedback control install 7 limiter magnetic coils fix magnetics as possible (f11) mods to tiles at f-port (DNB location) mods to CXRS systems new upper divertor probe array new cryopump Penning gauges repair Penning gauge cables install two new inner-wall scanning probes install new F-top MKS gauge refurbish outer divertor probe array install 10 halo Rogowskis upper divertor change fiber bundle inner wall telescope Mo source diag coverage mods clean or replace fast camera telescope replace fiber bundle inner wall telescope new GPI telescope on A-B shelf Thomson Scattering Upgrades Upgrade to HiReX Improve LH camera reliability 10

14 Status of ICRF System and Initial Antenna Operation with FFT Matching Network DoE Quarterly Review May 7, 2007 MIT, Cambridge MA Outline: 1. Operational status of ICRF system 2. Overview of Antenna operation with FFT matching network 3. Initial results from plasma operation.

15 ICRF System Status Removed all antennas during the last machine opening. D and E antennas were inspected and had arc damage between the back plate and vacuum transmission line where E B. Modified the backplate to reduce the E along B in-situ. During the inspection of the J antenna and associated transmission network, we found that: Vacuum transmission line had significant dust, likely Ti left over from previous LH grill disintegration; and Arc damage on two feedthrus and stub tuner. J antenna was reinstalled with clean vacuum transmission line and feedthrus; and the stub tuner section was cleaned and the damaged teflon removed. All antennas have operated near full power (~1 MW per transmitter) without significant problems. Gate board problems with FMIT#1 (D antenna) have been stabilized.» Have decided to develop a new board based on CPLD rather the current one-shot analog devices. Leaks in the transmission line have limited the use of SF6 which is critical for high power operation.» Repairs should be complete within couple of weeks.

16 C-Mod Discharges Present Wide Variety of Antenna Loads Source of load variation separates into two groups: External demand - experimental plan calls for a parameter scan. Plasma state change L H, H L and ITB evolution are examples. Previously, external demand mismatches are managed by either: Making small changes during scan or Making large parameter change and take successive discharges to obtain match. Plasma state induced variations required multiple discharges to allow for an optimal match to be obtained. Real time matching eliminates mismatches arising from external demand and plasma state changes.

17 Mechanical Stub Tuner and Phase Shifter Matching System Stub Phase shifter (line stretcher) Transmitter 50 Ω coaxial line Γ dc1 Γ dc2 Antenna Directional coupler #1 Directional coupler #2 Matched side (low VSWR) Un-matched side (high VSWR) Adjust stub and phase shifter lengths to obtain zero reflection (Γ dc1 0) between discharges.

18 Typical Results from ST/PS System Poor match Poor match Good match Good match

19 Options for Real Time ICRF Matching Frequency modulation: Vary RF source frequency to follow changes in antenna loading. Long (relative to wavelength) unmatched transmission line acts as phase shifter. Transmitter frequency bandwidth must be sufficient (bandwidth determined by transmission line length) Although demonstrated on JET and LHD, C-Mod unmatched line lengths are too short given the transmitter bandwidth. Conjugate T passive matching network. Requires antenna elements to be decoupled and independent. Successfully demonstrated on JET. We demonstrated that coupling degrades conjugate T matching. Dielectric liquid: Vary electrical length of stub tuner and phase shifter by varying level of dielectric liquid. Slow time response and has power handling limitations. Ferrite material: Varying magnetic field on ferrite material to change effective electrical length Fast (milliseconds) Limited range of electrical length variation Tested on ASDEX-Upgrade but had matching performance worse than mechanical stub tuner and phase shifter matching.

20 Fast Ferrite Tuner System Tuner #1 Tuner #2 Transmitter Short Stub #1 Short Stub #2 l st1 l st1,st2 =3/8 λ l st2 Γ 1 Γ 1 Γ 2 Γ 2 Load/Antenna

21 Fast Ferrite Tuning System

22 Digital Controller and Power Supply Digital Controller Power Supplies

23 Characteristics of AFT Ferrite Tuner A combination of permanent magnets and magnetic field coils is used for the magnetization of the ferrites. Permeability is varied around a set point by changing the magnetic field created by the coils. The electrical characteristic of the tuner is controlled by varying the current in the coils. Effective electrical length can vary ~35 cm at 80 MHz for current range of ± 150 A. 4 msec time response swing from -15 cm to +20 cm.

24 Demonstrate Good Time Response Feedback loop minimizes matched side reflection coefficient to 1% reflected power. Calculate the stub electrical lengths by comparing reflection coefficients on matched and unmatched sides of tuners. Calculate the new stub lengths using unmatched reflection coefficient. Calculate the error signals of the stub lengths. Convert the errors lengths to the FFT current errors. Calculate the demand signals using a tuned PID feedback loop to ensure stability and speed. Match is obtained in in less than 3 ms.

25 Good Match is Maintained Through Plasma State Change Reflected power maintained < 5% during the excursion caused by L H transition.

26 Matching Performance Comparison Previous ST/PS System FFT system L H LH Poor match Always matched Good match FFT system did not miss discharges due to plasma changes due to experimental demands.

27 Concluding Remarks Antennas have been re-installed and are operating at ~1 MW/transmitter. FFT matching network has been very successful in following external and plasma state variations in antenna loading. Considering options for adding capability to all 3 systems (~$200k per transmitter)

28 Alcator C-Mod Upper Divertor Cryopump Quarterly Progress Report Presented by B. LaBombard for the Cryopump Team May 7, 2007

29 Recent Accomplishments Alcator C-Mod Pumping Slots Gas Baffle Gas Cuffs (for laser access) Cryopump System Installed in C-Mod 10 instrumented shim plates In-vessel orbital welding and leak-testing of cryogenic tubing Custom-fit cryogenic-feed baffles, hangers 30 sectors: shelf, plates, posts, baffles 720 Moly tiles, fasteners, keepers,... Probes, rogowskis & gauge instrumentation Cryogenic Systems are Leak-Tight LN2 and LHe systems cooled down to LN2 temperatures -- no leaks Periscope Pumping Slot & Baffles Work as Planned Upper plenum pressures in USN exceed lower divertor pressures in LSN (~ x1.5) Penning gauges

30 Current Activities Alcator C-Mod External cryogenic components are being fabricated/assembled: LN2 transfer lines (complete) LHe transfer line (complete) Dewar tray & support brackets (complete) Heat exchanger (complete) LHe stepper control valve (tested) Installation of valves, sensors, pump,... Cryogenic System at Igoo Top heat stepper LHe line exchanger control valve LN2 line LHe Dewar PLC Rack Cryogenic Control System is being assembled/programmed: Wiring from PLC Rack to valves & sensors PLC programming for manual operation with interlocks & C-Mod permissives LHe transfer line fabrication

31 Remaining Tasks & Schedule Alcator C-Mod Cryopump Control System - Complete wiring/testing - Demonstrate manual control - Interface to C-Mod - Debug - Perform cool-down to LHe => LHe in dewar next week Helium Bottle A2 0, 2, 4 PSI Regulated Pressurizer/ Heater B2- high He Bottle Pressure Manual Dewar Vent Valve Regulator (manual) A1 LHe Level Meter B2- low Helium purge Pressure Dewar Vent Valve A4 Dewar Pressure 500 liter Helium Dewar A5 normally open 0.5 PSI Relief Valve +/- 15PSI/"Hg A3 LHe Valve - stepping motor drive - open and closed limit switches - % open-closed based on stepping motor Cryopump Control System B1 pneumatically actuated Helium Purge Valve Helium Pump&Purge Upper Divertor Cryopump Control System Relief Valve 10 PSI LHe Transfer Line State Diagram Standby Remote Control Readout D1 LHe Level Meter "dipstick" D2 He Exhaust Pressure D8 +/-30PSI/"Hg TC, Type K C6 Purge Vent to Cell Relief Valve Temperature sensor Temperature sensor TC, Type K 8 PSI C3 LN2 Sensor Manual Valve Heat Exchanger Relief Valve 30 PSI LN2 Manual Flow Control Valve D8 D3 Relief Valve Rouging Pump D PSI D7 Bypass Valve Temperature sensor Manual Valve TC, Type K C4 N2 Purge Valve LN2 Pressure Roughing Pump Valve C-Mod LN2 Sump to Helium gas recovery system 0-60 PSI C2 Flow Meter pneumatically actuated C5 N2 Purge Pressure LN2 Flow Valve D4 C1 Alcator C-Mod Vacuum Chamber D6 Helium Exhaust Valve LN2 Sump Status: Full or Not Full 0-60 PSI N2 inlet LN2 inlet Nitrogen Purge Cooldown to LN2 Change-Dewar He Purge LN2 Ready Start MP#475 Cryopump Startup ~ 1-2 wks I - System Assembly & Checkout II - Cool-down/Regeneration and pumping speed benchmarks III - Operation during C-Mod Discharge IV - Effect of SSEP on pumping V- Density control in H-mode discharges Shutdown C-Mod "INIT" C-Mod "PULSE" C-Mod "RECOOL" Cooldown to LHe LHe Ready Regeneration B. LaBombard April 27, 2007

32 Lower Hybrid Experiments Ron Parker Quarterly Progress Report 7 May 2007

33 LH Objectives for First Weeks of 2007 Campaign Reestablish LH operation similar to 2006 campaign Optimize coupling: Density, shape and power H-Modes, ICRF Investigate density limit Study distribution of LH-produced fast electrons in energy and space (via Bremsstrahlung)

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38 Parametric Decay Density Limit?

39 Summary: Coupling Studies Limited success with ICRF ~ 1MW J-port Appears to require gas feed to LH antenna to keep density from falling during ICRF next campaign Parametric decay to ICW s may indicate density limit Experiments and modeling continue Greg Wallace thesis

40 C-Mod Cross section with pinhole camera a c =5mm a d =5mm Spatial resolution =1.7cm

41 Coupled Power (kw) Time Traces for Low Density, 60 o Phasing Shots nl (10 20 m 2 ) 8 x HXR Count Rate (s 1 ) 4 x

42 60 Phasing (n = 1.6) Profiles Are Relatively Broad Count rate for kev (s 1 ) HXR Profiles for Low Density, 60 o Phasing Shots Viewing Cord Channel ms ms ms ms ms ms ms ms ms ms kev emissivity (counts/(mm 2 str s)) Flux surface emissivity for Low Density, 60 o Phasing Shots r/a ms ms ms ms ms ms ms ms ms ms

43 90 Phasing (n = 2.3) Have More structure, Peaking) Count rate for kev (s 1 ) HXR Profiles for Medium Density, 90 o Phasing Shots Viewing Cord Channel ms ms ms ms ms ms ms ms ms ms kev emissivity (counts/(mm 2 str s)) Flux surface emissivity for Medium Density, 90 o Phasing Shots r/a ms ms ms ms ms ms ms ms ms ms

44 Summary: Bremsstrahlung Measurements More structure, more peaking in the medium density, 90º shots. In both cases, peak seems to deplete faster than wings enhanced diffusion inside sawtooth mixing radius? Photon profiles reflect complex interplay between fast electron slow down, diffusion, energy, and deposition profile. More detailed modeling required--will be basis for Andrea Schmidt s PhD thesis.

45 Alcator C Mod C-Mod 2007 Campaign Status Presented by: Stephen M. Wolfe Alcator C-Mod Quarterly Review MIT Plasma Science & Fusion Center Cambridge, MA May 7, 2007

46 C-Mod JOULE target 15 Weeks of Research Operation in FY2007. Alcator C Mod Budgeted for 60 Research Days plus 14 Startup & Conditioning Tokamak Operations began March 13 (Power Tests) First Plasma March 21 First Research run March 29 (Lower Hybrid Physics) Ohmic and Lower Hybrid research runs carried out while machine cleanup, H/D reduction proceeds First boronization will take place this week Alcator C-Mod Quarterly Review May 7, 2007 smw 1

47 Run Utilization (Days). Alcator C Mod Topic/Thrust Through 2rd Quarter thru May 04 Lower Hybrid Operations/Diagnostics Integrated Scenarios (AT) Integrated Scenarios (H) Transport Physics Edge/Divertor ICRF Physics & Tech MHD Total Research Days Startup & Conditioning Total Operating Days Alcator C-Mod Quarterly Review May 7, 2007 smw 2