6.5 T.Matsumoto Ct2016

Compact Toroid Injection   into C-2U FRC

NIHON UNIVERSITY

Tadafumi Matsumoto Nihon University

US-Japan CT2016, August 24

Integral partnership

Nihon University

*  *  Development of a compact toroid injector for particle refueling

Collaborations

*  This project has been conducted in part under the MOU on the research cooperation between UCI and NU.

University of California at Irvine

Tri Alpha Energy

Presenter: Tadafumi Matsumoto

CT-WorkShop2016

Acknowledgements

*Nihon University

H. Gota T. Roche T. Asai* E. Garate E. Granstedt I. Allfrey T. Valentine J. Kinley,   C. Hooper M. Cordero P. Feng W. Waggoner M. Conroy M. Morehouse D. Sheftman T. Tajima*

Presenter: Tadafumi Matsumoto

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*UCI

*  CT Injector Overview

*  CT injection into C-2U FRC

*  Motivation

*  Summary

*  Upgrade

Outline

Presenter: Tadafumi Matsumoto

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*  CT Injector Overview

*  CT injection into C-2U FRC

*  Motivation

*  Summary

*  Upgrade

Outline

Presenter: Tadafumi Matsumoto

CT-WorkShop2016

*  The CT Injector is a viable refueling candidate

*  To penetrate the FRC, the kinetic energy density of the CT must be

Requirement for CT Injection * 

In C-2U particle loss rate was 2.0 - 4.0× 1018 / ms

higher than 4 kJ/m3, which is magnetic field energy inside the confinement vessel, e.g., density of CT 1×1015 cm-3, velocity 70 km/s

r e b m u n

e c i t r a P

)

1 x (

1.5

1.0

2.0

0.5

2.5

Motivation

Time evolution of particle loss rate of the C-2U FRC

Particles

Loss rate: 2.5x1018 #/ms

3 time (ms)

Presenter: Tadafumi Matsumoto

CT-WorkShop2016

*  CT Injector Overview

Ø Developed CT injector

Ø Test Stand

*  Motivation

*  Summary

*  Upgrade

Outline

Presenter: Tadafumi Matsumoto

CT-WorkShop2016

*  CT injection into C-2U FRC

Ø CT Parameters

Outer Electrode (I.D 83.1 mm)

Magnetized Coaxial Plasma Gun

Extension

Gas Puﬀ Valve

Bias Coil

Bias field

Gas port

Breakdown

Working gas

(1) Biasing magne7c field applied and working gas is injected between electrode.

(2) Forma7on bank is triggered to begin breakdown. The plasma is accelerated by Lorentz force.

(3) The accelerated plasma is captured by bias field. Then the reconnec7on occurs.

(4) The magne7zed plasma is ejected.

Accelerate by Jr×Bθ

Presenter: Tadafumi Matsumoto

Toroidal current

Reconnec7on

capture

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Inner Electrode (O.D. 54 mm)

Tungsten coating *  The surface of the inner electrode is coated with tungsten by Vacuum Plasma Spraying

Extension electrode *  The roles of the extension electrode are;

protect ceramic break from the plasma, and suppress diﬀusion of the magnetic field.

Transverse Field Coil

Test Bed with Transverse magnetic field coil

CT Injector

DriM tube *  Magne7c probe *  Dispersion Inter. *  PMT *  Triple Langmuir probe

Presenter: Tadafumi Matsumoto

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Drift tube *  The drift tube diagnostics measure typical CT parameters; velocity, density, and temperature. Glass chamber *  The transverse magnetic field coil simulates C-2U’s magnetic field.

Expansion glass chamber *  Magne7c probe *  PMT *  Triple Langmuir probe

CT was compressed by magnetic field

Field-free region èCT Expands

w/o Transverse field

Transverse field region èCT Compressed

w/ Transverse field

Presenter: Tadafumi Matsumoto

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Summary of CT Optimization

n  Required parameters n  Gun current up to n  Total energy of CT up to n  Velocity n  Density n  Electron temperature n  Energy Density

CT Performance

>70 km/s, 1.0×1015 cm-3 190 kA 0.7 kJ >100 km/s 1.5 - 3.5×1015 cm-3 20 - 40 eV 50 kJ/m3

Presenter: Tadafumi Matsumoto

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n  Developed CT injector achieved the requirement n  CT will penetrate C-2U Field n  Diameter of CT in the transverse field is 5-10 cm according to probe

CT Injec_on across transverse field

measurements

*  CT Injector Overview

*  CT injection into C-2U FRC

*  Motivation

*  Summary

*  Upgrade

Outline

1 CT Up to 3 CTs

Presenter: Tadafumi Matsumoto

CT-WorkShop2016

Ø Installation of CTI

Ø Single CT injection

Ø Multi-Pulse CT injection

CT injectors installed on C-2U

FRC

NW Injector

SE Injector

*  Angles

*  NW CTI

From mid-plane 26.1 deg

From Vertical 42 deg

*  The CT injectors were installed on the confinement vessel.

From mid-plane 29 deg

From Vertical 39.3 deg *  These injectors can be

controlled independently.

Presenter: Tadafumi Matsumoto

*  SE CTI

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Single CT pulse increased density/particles *  Interferometry verifies mid-plane density increase *  Pressure balance confirms particle number increases *  Shine-through reduced when CT injected

(

)

m c

1 ×

CTI triggered

s e c i t r a P

)

1 ×

d e n

(

Line integrated density

CO2 chords

Shine-Through Detection via Secondary Electron Emission (NB1-5, gray lines)

Particle number

Presenter: Tadafumi Matsumoto

Time (ms)

y t i s n e t n

~15%

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) . u . a

(

Time (ms)

Particle number increased by CT injection

(

1.5

1.0

2.0

2.5

0.5

)

1 ×

s e c i t r a P

s e c i t r a P Δ

)

1 ×

(

1.0 ms

2.0 ms 4.0 ms

with higher oﬀset

*  Original loss rate resumes

Initial rise particle inventory as high as 40%

*  CTs Injected at various times * 

*  Total particles added seems to depend on injection time *  Probably due to larger target *  For these conditions ~ 2ms

was optimal time for injection

Suﬃcient Refueling

Presenter: Tadafumi Matsumoto

CT-WorkShop2016

Injection Time (ms)

*  CT Injector Overview

*  CT injection into C-2U FRC

*  Motivation

*  Conclusion

*  Upgrade

Outline

1 CT Up to 3 CTs

Presenter: Tadafumi Matsumoto

CT-WorkShop2016

Ø  Installation of CTI

Ø  Single CT injection

*  Development of Multi-pulse injection system

Ø  Multi-Pulse CT injection

*  Main Bank of 125 µF with

*  Multi-pulse at ≤ 1 kHz

*  Diodes as crowbar and

Multi-pulse system and Fast Camera

10 kV

blocking element

Mul_-Pulse:

*  10-bit, 58 μm pixels

*  Nikon lens mount

-10 kV

125 µF

Main bank

CT innjector

Charging circuit

Camera control unit

Presenter: Tadafumi Matsumoto

Camera head

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Snubber circuit

*  100 ns minimum exposure time

*  360×410 pixel color sensor

Fast-framing Camera (NAC Image Technology):

*  Up to 1.25 MILLION frames/sec for 120 frames

High speed imaging of 2 CTs at the Test-Stand

Presenter: Tadafumi Matsumoto

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1st Awesome Video on the C-2U

Presenter: Tadafumi Matsumoto

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(2) 1 CT

(1) SE CT, (2) NW CT, (3) SE CT

CTs add a lot of particles

(

)

m c

d e n

1 ×

(1) 1 CT

15-20%

s e c i t r a P

)

1 ×

(

Time (ms)

(3) 1 CT

(2) 1 CT

(1) 2 CTs

(1) SE + NW CT, (2) SE CT

*  The increased density was 10-20% *  3rd CT alters/kills FRC *  Particle loss rate reduced by first CT *  FRC begins to decline after 2nd CT

*  First 2 CTs increase particle

Presenter: Tadafumi Matsumoto

inventory

Time (ms)

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Ø  Exposure 50 µs Ø  Filter

Blank

Dα emission was increased after CT injection

1st CT injection

Fast Camera Images

After 1st CT

Before 2nd CT

l  First CT leaves a trail of

neutral particles l  This can be seen

PI system is important to reduce trailing neutral gas

l  When 2nd CT enters it collides with cloud

interacting with edge plasma

2nd CT injection

Neutral gas emission

Presenter: Tadafumi Matsumoto

CT-WorkShop2016

*  CT Injector Overview

*  CT injection into C-2U FRC

*  Motivation

*  Summary

*  Upgrade

Outline

Presenter: Tadafumi Matsumoto

CT-WorkShop2016

Ø  Development of a Pre-ionization source

w/ PI, 25 psia

w/o PI, 40 psia

Easily breaks down

Pre-Ionization system has been developed

(

)

-5

V k

e g a t l o v n u G

8 Time (µs)

t n e r r u c n o i t a r u t a S

Time (µs)

(

)

1.5 µF

<10 kV

Gas puﬀ

Teﬂon (Insulator)

Semi-rigid cable

Copper (electrode)

Schematic diagram of Pre-Ionization system

Outer electrode

Inner electrode

Presenter: Tadafumi Matsumoto

CT-WorkShop2016

Triple Langmuir Probe measurement

w/o PI, 40 psia

w/ PI, 25 psia

PI reduces trailing neutral gas

No PI

With PI

*  PI eliminates gas trail *  Edge undisturbed

Presenter: Tadafumi Matsumoto

CT-WorkShop2016

*  Neutral gas follows CT *  Interacts with plasma

Dα emission w/ and w/o Pre-Ionization

Neutral gas load removed with PI

(

) .

. a

0.4

0.5

0.3

0.2

y t i s n e t n

0.1

w/ PI

w/o PI

C plane

Presenter: Tadafumi Matsumoto

CT-WorkShop2016

*  Dα emission at C plane minimized *  No burst of light when 2nd CT is injected -> Bulk of trailing neutral gas avoided

2 Time (ms)

*  The CTI program has advanced quickly *  Incremental addition of pulses *  Refueling from each pulse *  Dα emission after pulse

development

Summary

Presenter: Tadafumi Matsumoto

CT-WorkShop2016

*  Multi-pulsed system *  Reduction of neutral gas by Pre-ionization system

*  Full refueling capabilities for C-2W currently in

*  Several developmental cycles have led to