pisces laser transient systems - university of california...
TRANSCRIPT
UCSD Center for Energy Research K.Umstadter – PELS
PISCES
PISCES Laser Transient Systems
Karl R. Umstadter for PISCES Team
Center for Energy ResearchUniversity of California – San Diego, USA
February 11, 2009
UCSD Center for Energy Research K.Umstadter – PELS
PISCES
Overview
• Introduction
• Use of Laser Heat Pulses
• PA Short Pulse Update
• PA Long Pulse Initial Results
• PB Long Pulse Install
UCSD Center for Energy Research K.Umstadter – PELS
PISCESIntroduction
When an ELM occurs in tokamaks, up to 30% of the pedestal energy can be deposited on the plasma facing boundary
Result is heating & material loss due to sublimation, evaporation and melt splashing of plasma facing components
and
Expansion of the ejected material into the plasma
UCSD Center for Energy Research K.Umstadter – PELS
PISCES
IFE/MFE Transients & Experiments
J. Linke, F. Escourbiac, I.V. Mazul, R. Nygren, M. Rodig, J. SchlosseR, S. Suzuki, J Nucl. Mat. 367–370 (2007) 1422–1431
PISCES
5.E-9
Q
LP
UCSD Center for Energy Research K.Umstadter – PELS
PISCES
PISCES A & Beam Delivery
Laser PathPISCES A
Γ~1017 – 1019 D+/cm2 s-1
n ~ 1012 D+/cm3
Te ~ 5-10eVVbias ~ up to 250V Rp ~ 4cm
UCSD Center for Energy Research K.Umstadter – PELS
PISCESIntroduction
Calculations indicate that a pulsed laser system can be used to simulate the surface effects of the heat pulse of ELMs
Surface temperature during an ELM is a function of the energy density of deposition and thermal conduction to the bulk during and following the deposition
Lasers of varied pulsewidth can be utilized to mock transients such as ELMs and IFE wall impacts.
UCSD Center for Energy Research K.Umstadter – PELS
PISCES
0
500
1000
1500
2000
2500
3000
3500
1.0E
-08
1.0E
-07
1.0E
-06
1.0E
-05
1.0E
-04
1.0E
-03
Depth in Target (m)
Tem
pera
ture
(C)
ELM (300usec)ELM+60usecYAG (5nsec)YAG+1nsec
Q-Switch Nd:YAG as ELM Mimic
YAG Pulse Simulates Surface Heating Well
Longer duration results in deeper
heat transport
May effect retention
Surface temperature during an ELM is a
function of the energy density of deposition and thermal conduction to the bulk during and following
the deposition
Best expressed as
an Energy Impact Value
with units
MJ/m2-s1/2
UCSD Center for Energy Research K.Umstadter – PELS
PISCES
Mimic of ELM Transient on W
Laser Exposure of W at 200C for 60min
• Laser Parameters5nsec4mm spot166mJ per Shot~108 W/cm2
1200 Pulses
• Plasma ParametersTotal Fluence ~ 1026 D+/m2
Ion Energy ~100eV
Absorbed Energy Impact~58 MJ/m2 s1/2
RW (λ=1064nm) ~ 70%
ELM Equivalent1MJ/m2 @ 0.3msec
UCSD Center for Energy Research K.Umstadter – PELS
PISCES
SEM Surface Analysis
UCSD Center for Energy Research K.Umstadter – PELS
PISCES
Plasma + Heat Pulse Enhancement
F~ 1026 D+/m2
Tsurf ~ 50ºC
Absorbed Energy Impact~45 MJ/m2 s1/2
+
LASER ONLY LASER + PLASMA
LASERSPOT
UCSD Center for Energy Research K.Umstadter – PELS
PISCES
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 30 60 90 120 150Ion Energy [eV] (Vbias-Vplasma)
Mas
s Lo
ss (m
g)
Laser + PlasmaLaser OnlyPlasma Only
Erosion of W PFC under Simulated ELM Transients at High Repetition Rate
F~ 1026 D+/m2
Tsurf ~ 50ºC
3000 Transients withAbsorbed Energy Impact
~45 MJ/m2 s1/2
(low fluence between ELMs)
UCSD Center for Energy Research K.Umstadter – PELS
PISCES
Effects of D Loading on Damage
F = 5x1022/m2
F = 5x1023/m2
F = 2x1024/m2
Vbias=125VΓ=2x1022/m2-sec
Te=11eVne=2x1024/m3
SAM
PLE
Fluence to surfacebetween heating
transients
UCSD Center for Energy Research K.Umstadter – PELS
PISCES
Summary of Observations
• Fluence to PISCES-A targets between transients greater than operating tokamaks - approaching ITER
• Neutral and Ionized W found in range of mm to several cm in front of surface – allows study of transport & redeposition
• Synergistic effect between thermal transients & plasma exposure leads to enhanced material removal
• Synergistic effect depends upon D fluence between transients
UCSD Center for Energy Research K.Umstadter – PELS
PISCES
Long Pulse Laser
• New Laser System• 0.3 - 20msec pulse• Epulse = 1.5 - 50 J
• Installation on PISCES A• Compare results to short-pulse
results• Test diagnostic systems
• Installation on PISCES B for Mixed Materials Studies –
Alloying of MaterialsEffect on Surface “Nanostructures”
UCSD Center for Energy Research K.Umstadter – PELS
PISCESLong Pulse Nd:YAG as ELM Mimic
0
1000
2000
3000
4000
5000
1.E-06 1.E-05 1.E-04 1.E-03 1.E-02depth (m)
Tem
p (C
)
0.3msec1msec5msec10msec
Maximum system parameters at each pulse duration
UCSD Center for Energy Research K.Umstadter – PELS
PISCES
PA Long Pulse
• Output beam collimated (divergence reduced)• Laser safety windows installed• Beam entirely enclosed outside vacuum
“No goggle operation”
• Heat exchanger repaired• Aux air cooling added (AC)• Triggering system for remote/camera operation
UCSD Center for Energy Research K.Umstadter – PELS
PISCES
Initial Experiments
• 25J – 5msec - 1200 Laser Pulses @1/3 Hz5 kW – 50MJ/m2s1/2
• 75V Bias – Total Fluence ~1026 D+/m2
Room Temperature >500ºC
UCSD Center for Energy Research K.Umstadter – PELS
PISCES
Surface Profiles
-70E+3
-35E+3
000E+0
35E+3
70E+3
-500 0 500 1000 1500 2000 2500 3000 3500 4000
Position (um)
Hei
ght (
nm)
RT
550C
UCSD Center for Energy Research K.Umstadter – PELS
PISCES
PB Implementation Update
LaserOptics
EnclosurePyrometer
Spectroscopy Window with Laser Glass Shutter (Interlocked)
Laser-Safe Plastic Operators Window
UCSD Center for Energy Research K.Umstadter – PELS
PISCES
Questions
Karl R. [email protected]
PISCES TeamM.Baldwin, R.Doerner, J. Hanna, E. Hollmann,
D. Nishijima, G.R.Tynan, and J. Yu