Recent experiments in the STOR-M Tokamak* Akira Hirose In collaboration with: C. Boucher (INRS-EMT), G. St. Germaine D. Liu, S. Livingstone, A. Singh,

Recent experiments in the STOR-M Recent experiments in the STOR-M Tokamak*Tokamak*

Akira Hirose

In collaboration with:C. Boucher (INRS-EMT), G. St. GermaineD. Liu, S. Livingstone, A. Singh, C. Xiao

Plasma Physics LaboratoryPlasma Physics LaboratoryUniversity of SaskatchewanUniversity of SaskatchewanSaskatoon, Saskatchewan, Canada

*Supported by NSERC, CRC

PPL, Univ. of Sask.PPL, Univ. of Sask.Department of Physics & Engineering PhysicsDepartment of Physics & Engineering Physics

OutlineOutline

• Edge plasma flow measurements with Mach probes• Low frequency edge density and potential fluctuation

measurements with Langmuir probes (GAM)• Skin size ballooning mode (theory)• Density fluctuation measurements with 2 mm

microwave scattering (search for ETG and skin size mode)

• Vertical CT (compact torus) injection• Future plan


STOR-M top viewSTOR-M top view


STOR-M side viewSTOR-M side view


4-Pair Mach (Gundestrup) Probes4-Pair Mach (Gundestrup) Probes


Ohmic discharge (Ohmic discharge (IIp p counter to Bt)

Flow is predominantly along the magnetic field.


Parallel flow in the direction of current. Parallel flow in the direction of current.

t=17 ms r=10.5 cm

Bt

Ip


When the current is reversed, so is the When the current is reversed, so is the

flow.flow.

Bt

Ip

t=17 ms r=12 cm


Neoclassical theoryNeoclassical theory

• In an axisymmetric plasma,

Toroidal flow

Poloidal flow

may depend on collisionality

1 i ir dp dTEV V n

B enB dr dr

idTV VeB dr


Electrode BiasingElectrode Biasing


GAM (Geodesic Acoustic Mode)GAM (Geodesic Acoustic Mode)

• GAM frequency

• In GAM, the potential is symmetric but density perturbation is not,

• Excitation mechanism? Its roles?

sin , :GAMn poloidal angle

, (sound speed) = .ss

c Pc

R


Probes and locationsProbes and locations

= 0

- 45- 90

90

Probe locations


ObservationObservation

• Potential fluctuations have a peak at f ~ 12-15 kHz at all positions

• Density fluctuation has this peak except at the outer mid plane where it is small.

• Unclear what role is played by GAM in transport.


Power spectra of potential and density Power spectra of potential and density fluctuationsfluctuations

Density at -90 degrees (bottom)

Potential at 0 degree

Density at 0 degree


Skin size ballooning mode Skin size ballooning mode

• Skin size plasma turbulence has long been speculated. Such turbulence would explain Ohkawa diffusivity

and thus Alcator scaling • Earlier this year, a novel short wavelength

ballooning mode was predicted in the regime

2

pe

Tee

v c

qR

E en

.real De

222*

* 1 /e

De De e e De Tee i pe

ckk v

T T


Electron thermal diffusivity in units of Electron thermal diffusivity in units of gyro-Bohm gyro-Bohm 2Te

eGB en

v

L


Klystron

Directional Coupler

20dB

Two Attenuator

s

Phase

Shifter

Detector 2

Over-moded (WR-28) waveguide sections GOL

A Horn

Standard Gain Horn

Mixer

Isolator

Detector 1

Transmitted signal

Received signal

Power supply and cooling

system

Scattering Volume

Lower mirror

Upper mirror

Plasma

Reference Arm

E-H Tuner

Quartz windows

Vertical ports on STOR-M chamber

2 mm microwave scattering: experimental 2 mm microwave scattering: experimental setupsetup

Isolator

Directional Coupler


Dispersion relationDispersion relation

The solid line indicates the ion drift mode. The observed normalized frequency tends to be constant at high k.


Fueling Large TokamakFueling Large Tokamak

A.J.H. Donne et al. Fusion Sci. &Tech., January 2006 issue: “In the field of density control it has been concluded that there is not much flexibility in the fueling of ITER.” As part of their recommendations, they further state: “New fueling techniques should be tested on present devices. Given the prospects of CT (compact torus) injection, a test on a relatively large device is highly desirable.”

[Summary of 2005 IEA Workshop on Burning Plasma Physics and Simulations, Tarragona, Spain]


Compact Torus (CT) injectionCompact Torus (CT) injectionHorizontal vs. verticalHorizontal vs. vertical


USCTI with deflectorUSCTI with deflector


Effects of vertical CT injection (preliminary)Effects of vertical CT injection (preliminary)

0 5 10 15 20 25 30 350

1

2

3

4

5

6

7

8

9

n e (

1012

cm-3

)

Time (ms)

Shot: #170539

CT on


Vertical CT injection (cont.)Vertical CT injection (cont.)


Future planFuture plan

• Plasma flow: more complete plasma data are needed for comparison with the neoclassical theory

• Repetitive CT injection• Heterodyne 2 mm microwave scattering• Numerical simulations of the skin size

ballooning mode

Documents

Recent experiments in the STOR-M Tokamak* Akira Hirose In collaboration with: C. Boucher (INRS-EMT), G. St. Germaine D. Liu, S. Livingstone, A. Singh,