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
PPL, Univ. of Sask.PPL, Univ. of Sask.Department of Physics & Engineering PhysicsDepartment of Physics & Engineering Physics
STOR-M top viewSTOR-M top view
PPL, Univ. of Sask.PPL, Univ. of Sask.Department of Physics & Engineering PhysicsDepartment of Physics & Engineering Physics
STOR-M side viewSTOR-M side view
PPL, Univ. of Sask.PPL, Univ. of Sask.Department of Physics & Engineering PhysicsDepartment of Physics & Engineering Physics
4-Pair Mach (Gundestrup) Probes4-Pair Mach (Gundestrup) Probes
PPL, Univ. of Sask.PPL, Univ. of Sask.Department of Physics & Engineering PhysicsDepartment of Physics & Engineering Physics
Ohmic discharge (Ohmic discharge (IIp p counter to Bt)
Flow is predominantly along the magnetic field.
PPL, Univ. of Sask.PPL, Univ. of Sask.Department of Physics & Engineering PhysicsDepartment of Physics & Engineering Physics
Parallel flow in the direction of current. Parallel flow in the direction of current.
t=17 ms r=10.5 cm
Bt
Ip
PPL, Univ. of Sask.PPL, Univ. of Sask.Department of Physics & Engineering PhysicsDepartment of Physics & Engineering Physics
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
PPL, Univ. of Sask.PPL, Univ. of Sask.Department of Physics & Engineering PhysicsDepartment of Physics & Engineering Physics
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
PPL, Univ. of Sask.PPL, Univ. of Sask.Department of Physics & Engineering PhysicsDepartment of Physics & Engineering Physics
Electrode BiasingElectrode Biasing
PPL, Univ. of Sask.PPL, Univ. of Sask.Department of Physics & Engineering PhysicsDepartment of Physics & Engineering Physics
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
PPL, Univ. of Sask.PPL, Univ. of Sask.Department of Physics & Engineering PhysicsDepartment of Physics & Engineering Physics
Probes and locationsProbes and locations
= 0
- 45- 90
90
Probe locations
PPL, Univ. of Sask.PPL, Univ. of Sask.Department of Physics & Engineering PhysicsDepartment of Physics & Engineering Physics
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.
PPL, Univ. of Sask.PPL, Univ. of Sask.Department of Physics & Engineering PhysicsDepartment of Physics & Engineering Physics
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
PPL, Univ. of Sask.PPL, Univ. of Sask.Department of Physics & Engineering PhysicsDepartment of Physics & Engineering Physics
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
PPL, Univ. of Sask.PPL, Univ. of Sask.Department of Physics & Engineering PhysicsDepartment of Physics & Engineering Physics
Electron thermal diffusivity in units of Electron thermal diffusivity in units of gyro-Bohm gyro-Bohm 2Te
eGB en
v
L
PPL, Univ. of Sask.PPL, Univ. of Sask.Department of Physics & Engineering PhysicsDepartment of Physics & Engineering Physics
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
PPL, Univ. of Sask.PPL, Univ. of Sask.Department of Physics & Engineering PhysicsDepartment of Physics & Engineering Physics
Dispersion relationDispersion relation
The solid line indicates the ion drift mode. The observed normalized frequency tends to be constant at high k.
PPL, Univ. of Sask.PPL, Univ. of Sask.Department of Physics & Engineering PhysicsDepartment of Physics & Engineering Physics
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]
PPL, Univ. of Sask.PPL, Univ. of Sask.Department of Physics & Engineering PhysicsDepartment of Physics & Engineering Physics
Compact Torus (CT) injectionCompact Torus (CT) injectionHorizontal vs. verticalHorizontal vs. vertical
PPL, Univ. of Sask.PPL, Univ. of Sask.Department of Physics & Engineering PhysicsDepartment of Physics & Engineering Physics
USCTI with deflectorUSCTI with deflector
PPL, Univ. of Sask.PPL, Univ. of Sask.Department of Physics & Engineering PhysicsDepartment of Physics & Engineering Physics
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
PPL, Univ. of Sask.PPL, Univ. of Sask.Department of Physics & Engineering PhysicsDepartment of Physics & Engineering Physics
Vertical CT injection (cont.)Vertical CT injection (cont.)
PPL, Univ. of Sask.PPL, Univ. of Sask.Department of Physics & Engineering PhysicsDepartment of Physics & Engineering Physics
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