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

Alcator C-Mod Second Quarter FY07 DoE Review

1

DoE Quarterly Review05/07/07

Facility Status and Plans

2

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 (7o toroidal)– Many diagnostic upgrades and several new

installations

3

Updates: Operations

Tile Module

Installed tiles

• W-Tile Belt Installed– Complete toroidal

ring– 8 tungsten plates

per module– ITER relevant

activity

4

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

5

Updates: Diagnostics

• 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

probes

Retro/shutter

6

Updates: Diagnostics

• Upgrades to CXRS, fast scanning probes, x-ray spectrometers, Thomson scattering, bolometry, Penning gauges, polarimeter prototype, plasma video system

• Science Surface Station installed (S3)

• Microbalances measure deposition (radial, perp, 0.1 to 1 nm resolution)

• Langmuir probes measure density

S3

SiLi

NeSOX

PolarimeterBeamline

K-Port Horizontal

7

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

Spectrometer LayoutPilatus X-ray Detector Module

H-like Crystal

He-like Crystal

He-like Detectors

B-port

H-like Detector

Gate Valve

8

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

Actual pitch angle (degrees)

MS

E m

easu

red

pitc

h an

gle

(deg

rees

)

perpendicularbeam (2005)

y=x

-5 0 5 10 15-30

-20

-10

0

10

20

30

Channel: 2

Historically, C-Mod MSE beam-into-gas calibrationshave been strongly anomalous

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.

Rotating the diagnostic beam ~7o significantlyreduces the anomaly

Actual pitch angle (degrees)

MS

E m

easu

red

pitc

h an

gle

(deg

rees

)

perpendicularbeam (2005)

7o rotatedbeam (2007)

y=x

-5 0 5 10 15-30

-20

-10

0

10

20

30

Channel: 2

J. Ko (PSFC)S. Scott (PPPL)

H. Yuh (Nova Photonics)

These results have motivated ITER to re-consider theorientation of its diagnostic neutral beam.

9

Plans

• Plasma research operation for 15 weeks– Plasma cleanup phase complete– Ready for boronization

• Addition of vertical field to localize deposition• S3 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

• 2nd ICRF 4-strap antenna design/fab will continue

10

List of Completed Up-to-Air Tasks

Diagnostics/Invessel:

NESOX move to k-hor 10" flange

microbalance installation (S3)

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

General Ops:

Service Liquid Nitrogen System

Service LN2 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

Status of ICRF System and Initial Antenna Operation with FFT Matching Network

DoE Quarterly ReviewMay 7, 2007

MIT, Cambridge MA

Outline:1. Operational status of ICRF system2. Overview of Antenna operation with FFT matching network3. Initial results from plasma operation.

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.

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 ⇒Land 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.

Mechanical Stub Tuner and Phase Shifter Matching System

Adjust stub and phase shifter lengths to obtain zero reflection (Γdc1 0) between discharges.

StubPhase shifter

(line stretcher)

AntennaTransmitterΓdc1 Γdc2

Directional coupler #2Directional coupler #1

Un-matched side (high VSWR)

Matched side(low VSWR)

50 Ωcoaxial line

Typical Results from ST/PS System

Good match

Poor match

Good match

Poor match

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.

Fast Ferrite Tuner System

Tuner #2

Tuner #1

Load/Antennalst1,st2=3/8 λ

Short Stub #1 Short Stub #2

Transmitter

lst1 lst2

Γ1 Γ′1 Γ′2 Γ2

Fast Ferrite Tuning System

Digital Controller and Power Supply

DigitalController

PowerSupplies

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.

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.

Good Match is Maintained Through Plasma State Change

Reflected power maintained < 5% during the excursion caused by L⇒H transition.

Matching Performance Comparison

Good match

Poor match

Previous ST/PS System FFT system

L H LH

Always matched

FFT system did not miss discharges due to plasma changes due to experimental demands.

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)

AlcatorC-Mod

Upper Divertor Cryopump

Quarterly Progress ReportPresented by B. LaBombardfor the Cryopump TeamMay 7, 2007

AlcatorC-ModRecent Accomplishments

Cryopump System Installed in C-Mod10 instrumented ‘shim plates’In-vessel orbital welding and leak-testing of cryogenic tubingCustom-fit cryogenic-feed baffles, hangers30 sectors: shelf, plates, posts, baffles720 Moly tiles, fasteners, keepers, ...Probes, rogowskis & gauge instrumentation

Cryogenic Systems are Leak-TightLN2 and LHe systems cooled down to LN2 temperatures -- no leaks

Pumping Slot & Baffles Work as PlannedUpper plenum pressures in USNexceed lower divertor pressures in LSN(~ x1.5)

Penninggauges

Gas Baffle

Gas Cuffs(for laser access)

Pumping Slots

Periscope

AlcatorC-ModCurrent Activities

External cryogenic components arebeing fabricated/assembled:

LHe transfer line fabrication

Cryogenic System at Igoo Top

LHe Dewar

PLCRack

stepper control valve

heatexchanger LHe line

LN2 line

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 Control System is being assembled/programmed:

Wiring from PLC Rack to valves & sensorsPLC programming for manual operation with interlocks & C-Mod permissives

AlcatorC-ModRemaining Tasks & Schedule

Cryopump Control System- Complete wiring/testing- Demonstrate manual control- Interface to C-Mod- Debug- Perform cool-down to LHe => LHe in dewar next week

Start MP#475 “Cryopump Startup” ~ 1-2 wks I - System Assembly & Checkout II - Cool-down/Regeneration and pumping speed benchmarksIII - Operation during C-Mod DischargeIV - Effect of SSEP on pumping V- Density control in H-mode discharges

Cryopump Control System

PurgeVent toCell

C5C6

A5

DewarPressure

LHeLevelMeter

500 literHeliumDewar

0, 2, 4 PSIRegulatedPressurizer/Heater

LHe Valve- stepping motor drive

HeliumPurgeValve

LHe Transfer Line

Alcator C-Mod Vacuum Chamber

LHeLevelMeter"dip-stick"

HeliumBottle

He ExhaustPressure

ReliefValve Temperature

sensor

Upper Divertor Cryopump Control System

B. LaBombardApril 27, 2007

RougingPump

Heat Exchanger

FlowMeter

BypassValve

10 PSI

B2- low

A2

A1A3

B1

C3

C2 C1LN2 ManualFlow ControlValve

LN2Sensor

ReliefValve

ReliefValve

LN2FlowValve

LN2 inlet

LN2Pressure

N2PurgeValve

N2 inlet

N2 PurgePressure

D1D2 D5

D3

D4

to Helium gasrecoverysystem

HeliumExhaustValve

ReliefValve

8 PSI

30 PSI

60-70 PSI

0-60 PSI

0-60 PSI

TC, Type K

+/-30PSI/"Hg

Standby

Cooldown to LHe

Cooldown to LN2

Helium Pump&Purge

Shutdown

State Diagram

LN2 Ready

LHe ReadyC-Mod "INIT"

C-Mod "PULSE"

C-Mod "RECOOL" Regeneration

Nitrogen Purge

Change-Dewar He Purge

+/- 15PSI/"Hg

He BottlePressure

Regulator(manual) Roughing

PumpValve

- open and closed limitswitches

Remote Control

Readout

HeliumpurgePressure

B2- high

C4

A4

D6D7

D8DewarVentValve

normallyopen

ReliefValve

ManualDewarVentValve

0.5 PSI

pneumaticallyactuated

pneumaticallyactuated

C-ModLN2Sump

ManualValve

ManualValve

LN2 Sump Status:FullorNot Full

Temperaturesensor

D8TC, Type K

Temperaturesensor

TC, Type K

- % open-closed basedon stepping motor

Lower Hybrid Experiments

Ron Parker

Quarterly Progress Report

7 May 2007

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)

Parametric Decay – Density Limit?

Summary: Coupling Studies

Limited success with ICRF

~ 1MW J-port

Appears to require gas feed to LH antenna to keep densityfrom falling during ICRF – next campaign

Parametric decay to ICW’s may indicate density limit

Experiments and modeling continue – Greg Wallace thesis

C-Mod Cross section with pinhole camera

ac=5mmad=5mm

Spatial resolution =1.7cm

0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.30

100

200

300

400

500

Cou

pled

Pow

er (

kW)

Time Traces for Low−Density, 60o Phasing Shots

0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.34

5

6

7

8x 10

19

nl (

1020

m−

2 )

0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.30

1

2

3

4x 10

6

HX

R C

ount

Rat

e (s

−1 )

1070503031107050303410705030351070503036

5 10 15 20 25 300

500

1000

1500

2000

2500

3000

Viewing Cord Channel

Cou

nt r

ate

for

40−

60 k

eV (

s−1 )

HXR Profiles for Low−Density, 60o Phasing Shots

0−2.5 ms2.5−5 ms5−7.5 ms7.5−10 ms10−12.5 ms12.5−15 ms15−17.5 ms17.5−20 ms20−22.5 ms22.5−25 ms

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

500

1000

1500

2000

2500

3000

r/a40

−60

keV

em

issi

vity

(co

unts

/(m

m2 s

tr s

))

Flux surface emissivity for Low−Density, 60o Phasing Shots

0−2.5 ms2.5−5 ms5−7.5 ms7.5−10 ms10−12.5 ms12.5−15 ms15−17.5 ms17.5−20 ms20−22.5 ms22.5−25 ms

60° Phasing (n|| = 1.6) Profiles Are Relatively Broad

5 10 15 20 25 300

100

200

300

400

500

600

Viewing Cord Channel

Cou

nt r

ate

for

40−

60 k

eV (

s−1 )

HXR Profiles for Medium−Density, 90o Phasing Shots

0−2.5 ms2.5−5 ms5−7.5 ms7.5−10 ms10−12.5 ms12.5−15 ms15−17.5 ms17.5−20 ms20−22.5 ms22.5−25 ms

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

100

200

300

400

500

600

r/a40

−60

keV

em

issi

vity

(co

unts

/(m

m2 s

tr s

))

Flux surface emissivity for Medium−Density, 90o Phasing Shots

0−2.5 ms2.5−5 ms5−7.5 ms7.5−10 ms10−12.5 ms12.5−15 ms15−17.5 ms17.5−20 ms20−22.5 ms22.5−25 ms

90° Phasing (n|| = 2.3) Have More structure, Peaking)

More structure, more peaking in the medium density, 90ºshots.

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.

Summary: Bremsstrahlung Measurements

C ModAlcator

−

C-Mod 2007 Campaign StatusPresented by:

Stephen M. Wolfe

Alcator C-Mod Quarterly ReviewMIT Plasma Science & FusionCenterCambridge, MAMay 7, 2007

.

C ModAlcator

−C-Mod JOULE target 15 Weeks of ResearchOperation in FY2007

• 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 machinecleanup, H/D reduction proceeds

• First boronization will take place this week

Alcator C-Mod Quarterly Review May 7, 2007 smw 1

.

C ModAlcator

−Run Utilization (Days)

Topic/Thrust Through 2rd Quarter thru May 04

Lower Hybrid 1.06 4.63Operations/Diagnostics 0.00 5.40Integrated Scenarios (AT) 0.00 1.00Integrated Scenarios (H) 0.00 0.00Transport Physics 0.00 0.00Edge/Divertor 0.00 0.50ICRF Physics & Tech 0.00 0.19MHD 0.00 0.00

Total Research Days 1.06 11.81

Startup & Conditioning 6.63 8.13

Total Operating Days 7.69 19.94

Alcator C-Mod Quarterly Review May 7, 2007 smw 2