# Presentation: 636066

- Measurements of temperature-enhanced sputtering in liquid Sn

- Matt Coventry
- & David Ruzic
*Plasma-Material Interaction Group*
- Nuclear, Plasma, and Radiological Engineering
- University of Illinois at Urbana-Champaign

## Outline

- Motivation
- Approach
- Experimental progress
- Simulation progress
- Conclusions

## Liquid Sn modeling shows high temperature capabilities

- Liquid Sn divertor (Brooks)
- Evaporation limited temp: ~1200oC (vs Li at ~450oC)
- Liquid Sn walls (Rognlien &  Rensink)
- Evap limited temp including ARIES heat flux: ~830oC (vs Li at ~450oC)

- J.N. Brooks, Fusion Engineering and Design 60** **(2002) 515.
- T.D. Rognlien and M.E. Rensink, Contrib. Plasma Phys. 42** **(2002) 193.

- High operating temperatures correspond to greater energy conversion efficiency (Brayton cycle ~ 50%) and improved design flexibility.

## Advantage of using liquid Sn:  Vapor pressure!

-  Sn has an evaporative flux many (~6) *orders of magnitude* lower than Li
-  Sn is an excellent candidate for a liquid-wall system as well due to its vapor pressure [1]
-  Evaporation curves based on theory by [2] and fits from [3] and [4].

- [1] Brooks, J.N., *Modeling of sputtering erosion/redeposition – status and implications for fusion design.* Fusion Eng. Des., **60** (2002) p515-526.
- [2] Y. Waseda, S. Ueno, K.T. Jacob, J. Mat. Sci. Let, 8, (1989) 857-861.
- [3] M.A. Abdou, A. Ying, N.B. Morley et al., APEX Interim Report Report No. UCLA-ENG-99-206, (1999).
- [4] I.A. Sheka, I.S. Chaus, T.T. Mityureva, *The Chemistry of Gallium*, (1966), Elsevier, Amsterdam.

## Ion-surface InterAction eXperiment (IIAX)

- Ion-surface InterAction eXperiment (IIAX)

## Heater & liquid sample holder redesign

- Thermal considerations
- Minimized thermal contact between heater/target components and mounting hardware
- Radiation shield around circumference (SS) and behind (Mo) heater to minimize radiative losses
- Studies in progress regarding the contamination of the retention ring and shield material within the liquid Sn (considering Mo & W; Ta already ruled out)

- Mounting assembly &
- circumferential radiation shield

- Mo radiation shield

- Macor (or BN) isolator

- Mo retention ring

- Sample

- Mo retention shield

- Standard Heatwave
- UHV Heater

- Note: Mo/Re sample
- clips not shown

## Evaporation-limited

- Previous efforts to increase temperature range of measurements by hardware modifications successful, but IIAX measurements are now limited to ~650oC by Sn evaporation

- The target can reach 1200oC
- Assumptions: 160 nA – small – beam & YSPUT ~ 1
- Refractory solids should be measurable to 1000oC

- Peak ion current: ~ 1500 nA

## Sample area geometry:Sample & primary QCM

- Sample area geometry:Sample & primary QCM

- Ion beam at
- 45o incidence

- Sample Heater

- Sample

- Mo components

- Quartz Crystal

- QCM Head

- Ceramic components

- Heater stem for support

- (To scale)

## Quartz-crystal microbalance (QCM or QMB)

## Sample raw data

## Sample raw data 2

*1000 eV Ne**+** **** Sn*

## Estimated distribution from VFTRIM

-  105 sputtered particles’ angular distribution binned into 225 bins (15 polar x 15 azimuthal)
-  Radius of point on surface corresponds to ∂f/∂Ω ~ probability density
-  Red line shows beam incidence

**Notes:**
Previously I used an artificially-decoupled azimuthal and polar distribution.  This is unphysical & produces errant results.  
These results are used to estimate the collected fraction.

## Previously reported...

- Dashed lines indicate VFTRIM results

- [1] Coventry, M.D., J.P. Allain, and D.N. Ruzic, *Temperature dependence of liquid Sn sputtering by low-energy He+ and D+ bombardment.* J. Nucl. Mater., 2004. **335**(1): p. 115-120.
- [2] Coventry, M.D. and D.N. Ruzic, *Incident-mass dependence of temperature-enhanced ion-induced sputtering in liquid metals.* J. Nucl. Mater., 2005. **337-339**: p. 1015-1018.

**Notes:**
Work I’ve done shows this so far.
Seems to be mass dep.

## No temperature-dependence for 1000 eV Ar+ on Sn?

## No temperature-dependence for Ne bombardment up to ~800oC

## Enhancement seen in 1000 eV He+ sputtering

## MD Simulations

- Using Li-Li potential for liquid lithium calculated by M. Canales, L.E. González and J.A. Padró, [Phys Rev E 50** **(1994) p3656]
- For various incident energies and lattice temperatures (200 – 500oC) tracking kinematic relations during PKA-creation events

**Notes:**
Motivation

## Preliminary MD results

- 473K -- 200 flights
- 673K -- 300 flights

*100 eV Li **** Li at 45o*

## Future Work

- Wrap up liquid Sn work in March – Mostly low energy He measurements
- Ben Schultz to take over IIAX (currently on FLiRE)

- Mixed materials studies for all-metal JET/ITER
- How does small amount of W on Be samples affect erosion?

## Conclusions

- Temperature-dependent sputtering of liquid Sn still only seen for light ion sputtering (He) at sufficiently low energies (1000 or less probably)
- Simulations underway to help if mechanism has a kinetic component
- Future work towards ITER relevance

## Acknowledgements

- PFC Community, esp. Bob Bastasz, Jeff Brooks, Jean-Paul Allain
- DOE/OFES support
- Undergrad assistant: David Yi
- Graduate Students: Travis Gray, Ben Schultz, & Marty Neumann

## Data extracted from MolDyn simulations

- INC

- SKA Creation event

- TKA Creation event

- PKA Creation event

- Parent-daughter knock-on
- relations:
-    - Fraction of incident
-      energy transferred
-    - Recoil angle

- Primary, secondary, and
- tertiary knock-on creation events
- are tracked during MD simulations

**Notes:**
Extracted 3 pieces of info to import into the BCA code: 2 kinetic... & 1 surface-specific