Physics Basis of FIRE Next Step Burning Plasma Experiment

Charles Kessel

Princeton Plasma Physics Laboratory

U.S.-Japan Workshop on Fusion Power Plant Design, University of Tokyo

March 29-31, 2001 http://fire.pppl.gov

Goals of the FIRE StudyUsing the high field compact tokamak, produce burning plasmas with Q > 5-10 over pulse lengths > 2 current diffusion times, to study and resolve both standard and advanced tokamak burning plasma physics issues, for $1B

FIRE Has Many Features Similar to ARIES Tokamaks

FIRE Looks Like a Scale Model of ARIES-AT

FIRE

~ 3X

ARIES-AT The “Goal”

B = 6 TR = 5.2 m

Pfusion = 1755 MW

Volume = 330 m3

R = 2 m B = 10 T

Pfusion = ~ 200 MW

Volume = 18 m3

Nw = 3 MW/m2

Pfus = 12 MW/m3 Nw = 3.3 MW/m2

Pfus = 5.3 MW/m3

FIRE Can Access Various Pulse Lengths by Varying BT

FIRE’s Divertor Must Handle Attached(25 MW/m2) and Detached(5

MW/m2) Operation

FIRE’s Divertor is Designed to Withstand Large Eddy Current and

Halo Current Forces

FIRE Must Handle DisruptionsVDE Simulation with 3 MA/ms Current Quench

FIRE Has Several Operating Modes Based on Present Day Physics

• Reference: ELMing H-mode– B=10 T, Ip=6.5 MA,

Q=5, t(pulse)=18.5 s

• High Field: ELMing H-mode– B=12 T, Ip=7.7 MA,

Q=10, t(pulse)=12 s

• AT Mode: Reverse Shear with fbs>50%– B=8.5 T, Ip=5.0 MA,

Q=5, t(pulse)=35 s

• Long Pulse DD: AT Mode and H-mode– B=4 T, Ip=2.0 MA,

Q=0, t(pulse)>200 s

FIRE can study both burning AND long pulse plasma physics in the same device

Progress Toward ARIES-like Plasmas Requires A Series of Steps

1) stabilize NTM’s

2) stabilize n=1 RWM

3) stabilize n>1 RWMs

*each step with higher fbs

**each step with more profile control

FIRE is Examining Ways to Feedback Control RWM/Kink Modes

FIRE Must Satisfy Present Day Physics Constraints

FIRE Can Access Most of the Existing H-mode Database

FIRE’s Performance With Projected Confinement

FIRE Is Being Designed to Access Higher AT Plasmas

40

30

20

10

0

0 4 8 12 16 20 24 28 32

50

-5

Time (s)

Power (MW)

Bt

Ip

Ip

Bt

R = 2.14m, A = 3.6, 10 T, 7.7 MA, ~ 20 s flat top

Alpha Power

Auxiliary Power

Ohmic Power

1 1/2-D Simulation of Burn Control in FIRE* (TSC)

• ITER98(y,2) scaling with H(y,2) = 1.1, n(0)/<n> = 1.2, and n/n GW = 0.67

• Burn Time ≈ 18 s ≈ 21 τE ≈ 4 τHe ≈ 2 τskin

≈ 13Q

Plasma Response to Paux Modulation

Plasma Response to Fueling Modulation

Divertor Pumping Strongly Affects Plasma Burn

TSC Simulation of FIRE Burning AT Discharge

Ip=5 MA, Bt=8.5 T, N=3.0, li(3)=0.4, n/nGr=0.7, H(y,2)=1.15, PLH=20 MW, PICRF=18 MW, n(0)/<n>=1.45

TSC Simulation of FIRE Burning AT Discharge

A Burning Device Like FIRE Must Validate Assumptions Made in Power

Plant Studies Like ARIES

• Power and particle handling in the divertor/SOL/first wall

• Stabilization of NTM’s

• Stabilization of RWM/Kink modes

• Large bootstrap fraction plasmas with external CD

• Control of current, n, and T profiles

• Develop methods to mitigate/avoid disruptions

• Demonstrate energetic particle effects are benign

• All in a plasma with significant alpha particle heating

The FIRE Design is Evolving

• What can the machine do?– Q

– Pulse length

– T and n variations

– Heating/fueling/pumping/current drive

• What is the impact of physics uncertainties?– Scaling of τE

– Scaling of Pth(L to H)

– NTM -limit

– Density limit– Particle confinement τp*/τE

• What is machine flexibility to examine physics issues?– Burn control

– AE, energetic particles

– Sawteeth, other MHD

– AT profile interactions (p(r), j(r), (r))