Extrapolation of GDT Results to a DT Fusion Neutron Source for Fusion

Materials Testing

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Tom Simonen, U. Calif., Berkeley8th International Conference on Open

Magnetic SystemsJuly 5-9, 2010 Novosibirsk, Russia

US Fusion Program (2010)

• Establish the Scientific Basis– Burning Plasma (ITER)– Plasma Control (DIIID, EAST,KSTAR, JT60)– Materials Science

• Plasma Material Interactions• Neutron Material Interactions• ………..

US Mirror Assessment• Stimulated by new Gamma-10 and GDT Results• Formed a Mirror Study Group (Virtual Meetings)

– 10 Institutions, 25 individuals• Held Two Workshops

– Physics and Technology• Held a Magnetic-Mirror Mini-Conference

– At 2009 American Phys. Society DPP Meeting– Participated in Numerous DOE Planning Meetings

• Proposed International Collaborations– Russia, Japan, China

• Tutorial Talk at 2010 APS Meeting– Dmitri Ryutov

ITER is under Construction China, EU, India, Korea, Japan, Russia, US

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FUSION CHALLENGES (Sci.Am., March 2010)“Before fusion can be a viable energy source, scientists must overcome a number of problems.

Heat: Materials that face the reactions must withstand extremely high temperatures for years on end.

Structure: The high-energy neutrons coming from fusion reactions turn ordinary materials brittle.

Fuel: A fusion reactor will have to “breed” its own tritium in a complex series of reactions.

Reliability: Laser reactors produce only intermittent blasts; magnet based systems must maintain aplasma for weeks, not seconds.”

Fusion Neutrons Damage Materials

Fusion Materials Must Withstand Neutron Bombardment

• Three Options toQualify Materials:– Accelerator Based (coupons)– Mirror Based (Blanket Sub-modules}– Tokamak Based (Blanket Modules)

RTNS Accelerator Facility(US Rotating Target Neutron Source)

RTNS Accelerator

IFMIF Design by EU & Japan

Tokamak Component Test Facility (US Design)

Tokamak Fusion Nuclear Science Facility (US Design)

fnsf

TDF

1980’s Mirror Based Neutron Source Designs

Axisymmetric Magnetic Mirror

Gas Dynamic Trap (GDT) ConceptA.A. Ivanov, Fus. Sci. & Tech. 57, (2010), 320

GDT Schematic

GDT DD-Neutron Axial Profile(Agrees with Computer Simulation)

Electron Temperature vs Time(End Expansion = 100)

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- H-plasma n ≈ 1.5 x 1013 cm-3 with H-NBI

- H-plasma n ≈ 2.5 x 1013 cm-3 with H-NBI

- D-plasma n ≈ 2.5÷3 x 1013 cm-3 with H-NBI

- H-plasma n ≈ 1.2 x 1013 cm-3 with H-NBI min gas puff

- H-plasma n ≈ 3 x 1013 cm-3 with D-NBI

- H-plasma n ≈ 3.5÷3 x 1013 cm-3 with H-NBI

Neutron Flux Increases with Te(Now GDT Te = 0.25 keV so Flux = 0.4 MW/m2)

(ITER Goal = 0.5 MW/m2, Fluence = 0.3 MW-yrs/m2)

A Russian Neutron Source DesignA MW of Fusion Power for Weeks

Neutron Flux ~ 2 MW/m2 Test Area ~ 1 m2I

A DTNS Showing Magnets, Shielding ,Neutral Beams, and Material Samples

(Bobouch, Fusion Science & Tech. 41 (2002) p44)

With Today’s GDT ElectronTemperature (0.25 keV)

• DTNS Neutron Flux 80% of ITER

• DTNS Neutron Fluence in One Year Exceeds that in ITERs Lifetime

Note: DTNS does Not Address ITER’s Burning Plasma Physics or Full-scale Blanket Module Testing

Design DTNS from GDT Results

• Same Physical Size– L, r

• Higher Mag. Field, NBI Energy and Power– 1.2 T, 80 keV, 40 MW

• Same Dimensionless Parameters– Beta, B(z), L/ai, r/ai, Te/Ei

Same-Size & Dimensionless Scaling

GDT DTNS

B, Tesla 0.3 1.0

Eb, keV 20 80

Pb, MW 5 30

Beta (%) 60 60

Mirror Ratio, R 17 17

Length, & Radius, cm 7 00 , 6 700 , 6

Radius / Gyro-radius 2 2

Debye Length, 10-3 cm 2 2

Te/Eb , % 1 1

Collisionality 5 1 Marginal

f(pe)/f(ci) 6 0.6 More Microstable

v(b)/v(Alfven) 1.6 0.5 More Alfven Stab

A Possible Next Step

A Phased Approach (Physics >> PMI >> D-T Neutrons)

B = 0.6 Tesla – 1 s NBI 40 keV – 1 MW – 1 s

Key DTNS Scientific Issues

• Increase Electron Temperature– Now Te ~ 0.25 keV (0.4 MW/m2 neutrons)– Demonstrate Te > 0.5 keV (80 keV NBI)

• Confirm MHD Stabilization Physics– Diagnostics and Simulation

• Evaluate DTNS Design– Simultaneous Neutron and PMI Testing?

Key DTNS Technical Issues

• High Neutral Beam Power • Large Tritium Recycling

• Consider Simple Tandem-Mirror Concept (GDT-SHIP concept)

• Small Axisymmetric End-Cells Reduce Plasma End Losses– Reduces overall neutral beam power – Reduces Tritium Recycling

A Tandem-Mirror Neutron Source (TNS) (Based on TMX Data and the GDT-SHIP Concept)

TNS Features

• Plug to Center-cell density ratio 4– To reduce end loss 4-fold

• Plug Mirror ratio 3– To reduce AIC and loss cone size

• Plug NB injected at mirror ratio 1.3– For AIC Stability

• Neutral Beam Power (MW) 20– Half of DTNS

TNS Parameters

• Maximum Miagnetic Field, 20 Tesla• Plug Mirror Ratio, 3• Central-Cell Magnetic Field, 1.2 Tesla• Central-Cell NBI Power, 10 MW• End-Cell NBI Power, 5 MW each• Electron Temperature, 2 keV

TNS Challenges(GDT-SHIP can address many issues)

• Electron Temperature• MHD Stability at Higher Te• Energetic Ion iMicro-stability• Tritium Retention• Detailed Modeling Needed

• GDT – SHIP can address many issues

Summary

• A DT Neutron Source (DTNS) can have the same Physical-Size and the same Dimensionless -Size as GDT

• A Simple Tandem Mirror Neutron Source (TNS) Reduces Tritium Reprocessing 4-fold and Reduces the Neutral Beam Power 2-fold.

We Can Produce 1 MW of Fusion Power Sustained for Weeks within 10 Years

Purpose:– Test materials & Subcomponents– Demonstrate sustained fusion power

Features:– Based on recent GDT Results– Low Tritium Consumption,– No tritium Breeding Required– Simple Construction Geometry.