Plasma Research Center, University of Tsukuba Y. Nakashima, GAMMA 10 Group

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14th US-Japan Workshop on Inertial Electrostatic Confinement Fusion University of Maryland, College Park College Park, MD October 14th - 17th, 2012 The GAMMA 10 Tandem Mirror Plasma Confinement

1 14th US-Japan Workshop on Inertial Electrostatic Confinement Fusion University of Maryland, College Park College Park, MD October 14th - 17th, 2012 The GAMMA 10 Tandem Mirror Plasma Confinement Device as a Test Bed for DEC Technologies Plasma Research Center, University of Tsukuba Y. Nakashima, GAMMA 10 Group CONTENTS 1. GAMMA 10 Tandem Mirror Device 2. Present Status of GAMMA 10 Experiments 2-1. New Research Plan for Divertor Simulation Studies 2-2. High-heat Flux Generation Experiments 2-3. First Results of E-divertor Experiments Using D-module 3. Collaboration with Kobe University for DEC Research 4. Summary

2 Schematic View of GAMMA 10 Axially escaping plasma is confined by the potential formation produced with ECH on both ends. GAMMA 10 is the world largest tandem mirror type plasma confinement device. The initial plasma is injected by plasma gun and the main plasma is produced by ICRF waves and gas puffing. 14 th US-J IEC W/S DEC-Panel 2012, Y. Nakashima

3 GAMMA 10 Tandem Mirror Device GAMMA 10 Device Total length 27 m B max : 3 Tesla ICRF: 500 kw 4 ECH: 400 kw kw 2 NBI: 1.5 MW MW 2 N e : ~ m -3 T i : ~ 10 kev T e : ~ 100 ev, Φ C : ~ 2 kv

Anchor region Outline of the New Research

Toward the new research project by making the

Mirror Confinement Magnetic Field line Field

Microwave source for ECH High power heating

order to upgrade the above research, the

confinement by potential formation (2) New

) are introduced to existing tandem mirror

4 Anchor region Outline of the New Research Plan The Largest Tandem Mirror GAMMA 10 Toward the new research project by making the best use of the existing device End region Mirror Confinement Magnetic Field line Field strength Plasma Magnetic coil Improvement of confinement by potential formation Open Magnetic Field Potential & Electric field Microwave source for ECH High power heating systems (RF, NBI) Tools for Plasma Control In order to upgrade the above research, the following two projects are initiated. Target plate (1) Extension from core to boundary region for improvement of plasma confinement by potential formation (2) New divertor systems (A-Div. and E-Div.) are introduced to existing tandem mirror device (GAMMA 10) for boundary plasma study based on divertor simulation. Contribution to the Tokamak Research to be reborn as GAMMA 10/PDX tandem mirror device Open Systems & PMIF 2012, Y. Nakashima

divertor simulation experimental module (D-module) was installed. Open Systems & PMIF 2012, Y.

Assembly (Probe, Calorimeter, V-shaped target) Movable calorimeter / Directional probe 0 100 200 300 z EXIT (cm) Noble Gas Injection Diagnostics of

A set of calorimeter and directional probe was installed for the simultaneous measurement of heat and particle fluxes.

5 Experimental setup for E-Div. research Start-up preparative experiments at the end-mirror (three years ago) GAMMA 10 plug/barrier-cell In this spring, a ECH large-scale divertor simulation experimental module (D-module) was installed. Open Systems & PMIF 2012, Y. Nakashima Observation Area by High-speed Camera GAMMA 10 end-mirror vacuum vessel NBI GAMMA 10 End Tank End-loss Ion Energy Analyzer Rotatable Target Assembly (Probe, Calorimeter, V-shaped target) Movable calorimeter / Directional probe z EXIT (cm) Noble Gas Injection Diagnostics of the end-loss plasmas were installed at the west end-mirror cell and the high heat-flux generation experiments were started. A set of calorimeter and directional probe was installed for the simultaneous measurement of heat and particle fluxes. Movable targets consist of a disk and V-shaped plates made of tungsten, a calorimeter array and directional probe were also installed. Visible spectroscopic data were obtained from the plasmamaterial-gas interactions by using a high-speed camera together with noble gas injection. Energy analysis of end-loss ions was started by using an array of the multi-gridded type energy analyzer (ELIEA).

tank has a large space capacity (3 m in diameter, 3 m in height) and flexibility for

Nakashima Exit of end-mirror throat φ 375 Rotatable Target (newly made) Opening the

Calorimeter / directional probe (newly made) A set of movable calorimeter and

6 Experimental setup for E-Div. research Reform of the west end vacuum vessel Interior of the GAMMA 10 end-mirror tank has a large space capacity (3 m in diameter, 3 m in height) and flexibility for installation of diagnostics. PMIF 2011, Y. Nakashima Exit of end-mirror throat φ 375 Rotatable Target (newly made) Opening the partition wall in the vessel Interior of the west end vacuum vessel Support rod Calorimeter / directional probe (newly made) A set of movable calorimeter and directional probe was installed near the exit of the end-mirror throat (z EXIT = 30 cm) and the rotatable target consist of Carbon, Tungsten and Stainless steel was installed at 70 cm from the exit.

7 1. High heat-flux generation experiments

ICRF power dependence on heat and particle fluxes P Heat ( MW / m 2 ) 1.2 1 0.8 0.6 0.4 0.

2 Γ i ( 10 23 particles/s m 2 ) ICRF power dependence on parallel ion temperature 0 0 50 100 150 200 RF2 power (kw) In ICRF heating phase, the heat-flux increases with the RF power and the

8 Recent results of E-Div. experiments In typical hot-ion-mode plasmas (n e (0) ~ m -3, T i (0) ~ 5 kev), measurement of heat and particle flux from the end-mirror exit has been carried out. ICRF power dependence on heat and particle fluxes P Heat ( MW / m 2 ) P Heat (x = 0 cm) P Heat (x = -5 cm) Γ i (x = 2 cm) Γ i (x = -3 cm) RF only 190 ms Z Exit = 30 cm RF2 Power (kw) Γ i ( particles/s m 2 ) ICRF power dependence on parallel ion temperature RF2 power (kw) In ICRF heating phase, the heat-flux increases with the RF power and the heat-flux density of 0.8 MW/m 2 and the particle-flux density of H/s m 2 were achieved near the machine axis at the highest power of RF2 in this experiment. The parallel ion temperature determined from probe and calorimeter increases with the ICRF power and gives a good agreement with the result of ion energy analyzer (ELIEA) measured at the end-plate (z exit = 300 cm) T i// (ev) from Probe & CM from ELIEA Z Exit = 300 cm Open Systems & PMIF 2012, Y. Nakashima

8 IELIEAW-ch1 1000 Ti //eff 800 0.6 600 0.4 400 0.2 200 0 50 10 1200 100 150 200 T ////efff IELIEA (ma/cm 2) 200 1.2 0.8 0 50 150 Time (ms) 1.

9 Recent results of E-Div. experiments In order to increase the particle flux, additional ICRF wave (RF3) was applied in the both anchor-cells. NLCC NLEA 3 2 RF NLCC NLWA RF3 100 Time (ms) IELIEAA (ma/cm 2) IELIEAW-ch Time (ms) RF3 R F3 Γ > 1023 is expected. i IELIEAW-ch Ti //eff T ////efff IELIEA (ma/cm 2) Time (ms) # RF3 (West) 8 7 Γi (x10 22 particles/m icles/m s) # Line Density (1013 cm-2) Line Density (1013 cm-2) RF3 (East) Time (ms) Remarkable increase of plasma density due to the RF3 pulse was observed at C.C. and A.C. and the resultant ion flux at the west end-cell significantly increased. w with wit itith h ad a add additional dd diitititon o al RF3 RF1, 2 + GP3 GP3,4 3,4 4u up p increased RF1 power rprb = 0 cm zexit = 30 cm NLCC (x cm ) Open Systems & PMIF 2012, Y. Nakashima

10 (MW/m 2 ) P Heat net Recent results of E-Div. experiments Effect of superimposing ECH pulse into RF plasmas was investigated. ECH power dependence on peak heat flux P Heat ~2010 P Heat 2012 Z EXIT = 30 cm ITER relevant pech Power (kw) r CM = 0 cm Targeted heatflux level The heat flux almost linearly increases with the ECH power. A short pulse of plug ECH (5 ~ 25 ms) was injected into ICRFheated plasmas (2 ~ m -3 ) and the heat flux measurement has been performed at the endmirror exit. Superimposing ECH pulse of 380 kw attained the highest heat-flux almost comparable to the heat load of ITER divertor plate ( 10 MW/m 2 ). From the above result, a good prospect of achieving higher heat flux is expected by building up the plasma heating power. Open Systems & PMIF 2012, Y. Nakashima

11 2. First results of E-Div. experiments using D-module

Installation of divertor simulation experimental module

Research Objectives Compression of neutrals and enhancement

Study of radiative cooling by injecting radiator gases into

Angular-dependence to the magnetic field on the above

12 Installation of divertor simulation experimental module (D-module) Schematic View of GAMMA 10 West End-mirror Cell Research Objectives Compression of neutrals and enhancement of recycling by making a fullyclosed configuration. Study of radiative cooling by injecting radiator gases into D-module. Divertor pumping experiment using back-side door. Angular-dependence to the magnetic field on the above characteristics. Open Systems & PMIF 2012, Y. Nakashima Divertor Simulation Exp. Module (D-module) Plasma Inlet φ 200 Elevating System V-shaped Tungsten Target Open Angle: 15 ~ 80 Radiator Gas Inlet (He, Ne, Ar)

measurement of visible emission from plasma-target

ECH: Without V-shaped target opening angle α V : 45

size: 640 480 pixels Shutter: Open Frame rate: 10,000

13 First result of E-Div. experiment using D-module Firstly, 2-D image measurement of visible emission from plasma-target interactions in D-module was performed using high-speed camera. Shot No.: # ICRF: RF1 <220 kw> RF2 <110 kw> RF3 Without ECH: Without V-shaped target opening angle α V : 45 Gas Injection: Without Camera: Phantom v710 Image size: pixels Shutter: Open Frame rate: 10,000 fps Filter: Without Images are colorized from blue to red corresponding to the brightness of the image. Open Systems & PMIF 2012, Y. Nakashima

14 3. Collaboration with Kobe University for DEC Research

Chamber In 2004, a collaborative research

plasma Kobe_Cusp DEC has been installed on

15 GAMMA10 West End-cell and Location of Kobe_Cusp DEC GAMMA 10 End-mirror Vacuum Chamber In 2004, a collaborative research program for DEC has been started between Kobe Univ. and Tsukuba Univ. Cross-section of the GAMMA 10 end-loss plasma Kobe_Cusp DEC has been installed on the inclined stand according to the magnetic field. Three pieces of coils are placed on the extension duct in order to guide the end-loss particles smoothly to DEC. A movable end-loss ion analyzer is installed in front of the DEC and charged-particle flow was measured. Inlet of Kobe_Cusp Dec 14 th US-J IEC W/S DEC-Panel 2012, Y. Nakashima

16 Kobe_Cusp DEC Connected to the GAMMA 10 West End under the Collaboration Program Kobe_Cusp DEC End Loss Ion Analyzer Guide Coils GAMMA 10 West-end Vacuum Chamber 14 th US-J IEC W/S DEC-Panel 2012, Y. Nakashima

Plasmas Using DEC Electrons The load circuit

The first light from the endloss plasma by

Collector Ion Collector DC POWER Load Neon

point cusp side in the Kobe_Cusp DEC and

17 Slanted Cusp Magnetic Coils Direct Electricity Generation from the Endloss Plasmas Using DEC Electrons The load circuit was replaced to neon lamps. The first light from the endloss plasma by using DEC Plasma A B Ions I V Electron Collector Ion Collector DC POWER Load Neon lamps were connected to the electrode of point cusp side in the Kobe_Cusp DEC and lighting of the lamps was successfully performed. 14 th US-J IEC W/S DEC-Panel 2012, Y. Nakashima

18 Summary GAMMA 10 is the world largest tandem mirror type plasma confinement device operated in Plasma Research Center, Univ. Tsukuba, which provides high heat-flux plasma flow from the endmirror throat. By making best use of large tandem mirror device, divertor simulation studies have been started in GAMMA 10. In this research plan, a high heat-flux divertor simulator (E-Div.) has been performed successfully by using an end-mirror exit of the GAMMA 10 tandem mirror. In standard hot-ion mode plasmas (n e0 ~ m -3, T i0 ~ 5 kev), the heat flux density of 0.8 MW/m 2 and the particle flux density of /s m 2 were observed at 30 cm downstream of the end-mirror exit. Parallel ion temperature T i// estimated from the probe and calorimetric measurements gives a good agreement with the result of direct measurement by using ion energy analyzer (ELIEA). Obtained T i// are determined to be in the range from 100 ev to 400 ev and increases with the ICRF power. 14 th US-J IEC W/S DEC-Panel 2012, Y. Nakashima

19 Summary (continued) Additional ICRF heating at anchor-cells significantly increased the ion flux (expected to be m 2 /s) at the west end-cell, which proved an effectiveness of additional plasma heating by ICRF wave. Superimposing the ECH pulse induces a remarkable enhancement of heat flux and the peak heat-flux density more than 10 MW/m 2 was attained during the short pulse ECH injection, which almost comes up to the heat load level of the divertor plate of ITER. In this spring, new divertor simulation experimental module (D-module) was installed at the west end-mirror exit and various divertor simulation experiments have just started and a number of interesting results have been observed. In FY2004, a collaborative research program for DEC has been started with Kobe university and a cusp-type DEC was installed in GAMMA 10. First electricity generation experiment using the DEC device has been successfully performed. 14 th US-J IEC W/S DEC-Panel 2012, Y. Nakashima

20 End Thank you very much for attention.

Production of High Power and Large-Area Negative Ion Beams for ITER

1 Production of High Power and Large-Area Negative Ion Beams for ITER M. Hanada, T. Inoue, M. Kashiwagi, M. Taniguchi, H. Tobari, K. Watanabe, N. Umeda, M. Dairaku, Y. Ikeda, K. Sakamoto Japan Atomic Energy