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,

Goals of the FIRE Study Using 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 N w = 3 MW/m2 P fus = 12 MW/m3 N w = 3.3 MW/m2 P fus = 5.3 MW/m3

FIRE Can Access Various Pulse Lengths by Varying B T

FIREs Divertor Must Handle Attached(25 MW/m2) and Detached(5 MW/m2) Operation

FIREs Divertor is Designed to Withstand Large Eddy Current and Halo Current Forces

FIRE Must Handle Disruptions VDE 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 f bs >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 NTMs 2) stabilize n=1 RWM 3) stabilize n>1 RWMs *each step with higher f bs **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

FIREs Performance With Projected Confinement

FIRE Is Being Designed to Access Higher AT Plasmas

Plasma Response to P aux 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)/ =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 NTMs 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/pump ing/current drive What is the impact of physics uncertainties? –Scaling of E –Scaling of P th (L to H) –NTM -limit –Density limit –Particle confinement p */ E What is machine flexibility to examine physics issues? –Burn control –AE, energetic particles –Sawteeth, other MHD –AT profile interactions (p(r), j(r), (r))