1 US PFC Meeting, UCLA, August 3-6, 2010 DIONISOS: Upgrading to the high temperature regime G.M....

1US PFC Meeting, UCLA, August 3-6, 2010

DIONISOS: Upgrading to the high temperature regime

G.M. Wright, K. Woller, R. Sullivan, H. Barnard, P. Stahle, D.G. Whyte

Plasma Science & Fusion Center, MIT, Cambridge USA


Outline

• DIONISOS Advantages and capabilities

• The high temperature regime Importance Details on upgrades

• He concentrations and depth profiles in W fuzz layers Heavy ion ERD analysis


DIONISOS has similar capabilities to other linear plasma devices in the US

PISCES-B (UCSD) TPE (INL) DIONISOS (MIT)

Deuterium ion flux (m-2s-1) 1021–1023 1020 - 2x1022 1020-1022

Ion energy (eV) 20–300 (bias) 50–200 (bias) 20-350 (bias)

Te (eV) 4 – 40 5 – 20 5-10

Ti (eV) 2 – 5 2 - 5 2 - 5

ne (m–3) 1018–1019 1016 - 2x1018 1017-1019

Pmax (MW/m2) 5 0.5 0.6

Plasma diameter (mm) 75 50 50

Pulse length (s) Steady state Steady state Steady-state

Activated targets No Yes No

Tritium No Yes No


What makes DIONISOS unique?

• Simultaneous plasma and ion beam exposure of targets

• Active target heating and cooling (Ttarget = 300-750 K)

• In-situ, time-resolved ion beam analysis

•In-situ target irradiation by high-energy (~MeV) ions for irradiated materials studies.


Why are we interested in the high temperature regime for DIONISOS?

• Commercial fusion reactors will run with “hot walls” (e.g. 900-1000 K)

• New physics and surface effects at high temperature.

W nanostructureBubbles

• Also allows for in-situ target thermal desorption spectroscopy and annealing.

Ueda, DIV-SOL ITPA, Amsterdam, May 2009Baldwin et al, JNM 390-391


A new target holder is required to reach these temperatures in DIONISOS

• Heatwave Labs UHV substrate heater with DC power supply• Max operating temperature of 1473 K• Electrically isolated from target• Mo heat shielding on the sides and back• Active PID temperature control (K-type thermocouple)

Substrate heater

Isolated sample clips for target biassing

Heat shielding

Power leads


Some key differences between the current target holder and the high-T target holder

• Operating range RT-750 K

• Active cooling and heating

• Large targets (> plasma column)

• Operating range 200-750 K• Active heating feedback• Small targets (< plasma

column)

Current target holder High-T target holder


Other components must also be protected from the additional radiative heating from

the target

• Hot target leads to radiative heating of sensitive components.

• Solid-state detectors used for IBA are cooled through thermal contact with a water-cooled plate.

Cooling line

Heat sink

Detector

Detector housing

Support rod


Ion beam analysis on W nano-filament formation has yielded useful new data

• Fuzz grown in Pilot-PSI with peaked flux and temperature profile.

• ERD performed with 7 MeV O4+ ions for He detection.

• Beam spot is 2.0 x 3.5 mm (oval)

• Fuzz layer is only 5-10 % density of bulk tungsten. Penetration depth of 7 MeV O4+

ions is ~950 nm

Center2mm4mm6mm8mm

10mm


W Fuzz has been grown under a variety of conditions

W13 1200C 500s

W12 1500C 1000s

W11 1500C 500s

W10 1500C 200s

PISCES 850C 300s

PISCES 850C 1000s

PISCES targets have uniform conditions across the surface.

Grown in Pilot-PSI with peaked flux and temperature profile.G. De Temmerman, FOM Rijnhuizen, The Netherlands

NOT exposure conditions for fuzz growth, just an example of possible gradients in Pilot-PSI exposures.


Radial scan on W13 demonstrates transition from fuzz to non-fuzz conditions

• He is distributed uniformly throughout the fuzz layer.

• Before fuzz formation, He is peaked at the surface.

• All other targets had flat He profiles similar to the center of W13

He

conc

entr

atio

n (a

t. %

)


Comparison of He concentrations from all other targets

• He concentration in the W fuzz falls within 0.5-1.0 at.% for all conditions investigated here.

• No clear dependence of He concentration on He fluence or surface temperature.

• More data needed. Controlled parameter scans could reveal hidden dependences.


Future goals

• Further investigations into the dynamics of PSI and PSI for irradiated materials

• In-situ fuzz growth in Pilot-PSI• Time-resolved ERD measurements of W fuzz growth• Retention in high-temperature walls under irradiation

conditions• Characterization of carbon deposition on high-

temperature tungsten substrate

1 US PFC Meeting, UCLA, August 3-6, 2010 DIONISOS: Upgrading to the high temperature regime G.M....

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