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NRL J. Sethian M. Myers J. Giuliani M. Wolford R. Lehmberg S. Obenschain M. Levy Commonwealth Tech F. Hegeler M. Friedman RSI P. Burns SAIC R. Jaynes. Electra (KrF) Laser Development. 14 th HAPL Meeting San Diego, CA August 8th , 2006 Naval Research Laboratory - PowerPoint PPT Presentation
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14th HAPL MeetingSan Diego, CA
August 8th , 2006
Naval Research LaboratoryPlasma Physics Division
Washington, DC
Presented by M. Wolford
Work supported by DOE/NNSA/DP
Electra (KrF) Laser Development
NRLJ. SethianM. MyersJ. GiulianiM. Wolford
R. LehmbergS. Obenschain
M. Levy
Commonwealth Tech
F. HegelerM. Friedman
RSIP. Burns
SAIC R. Jaynes
• Cathode Rep-rate & Durability:– Installed Carbon Emitter
• 2.5 Hz 24,978 shots (continuous)
• Beginning Rep-Rate Focal Profile Experiments– Single shot Recovery of Recirculator less than 200 ms
(Necessary Time for 5 Hz Operation)
• First Light Electra Pre-Amplifier – 23 J laser output
Summary Since Last HAPL Meeting
Ceramic honeycomb
cathode
ceramic honeycomb
primaryemitter:velvet
Review IA: CERAMIC HONEYCOMB CATHODE:Placing a ceramic honeycomb slab above the emitter significantly
improves the cathode performance and lifetime
• The continuous shot number is limited by gas buildup in the vacuum diode (forces us to briefly break up long runs)
• Laser run duration is ultimately limited by foil failure.
(due to cathode debris and/or excess plasma in the A-K gap)
Present Limit of Laser Durability
Cathode lifetime was limited to 10,000 continuous shots
HAPL Meeting March 2006
• Conditioning of the cathode• Replace velvet primary emitter with graphite emitter• Cool the cathode• Modify the cathode construction to eliminate weak spots• Replace cordierite ceramic with more robust SiC or YZA
(yttria stabilized zirconia-alumina)• Eliminate cathode shroud
high voltage feedthroughfor water cooling
copper cooling plate
primary emitter:graphite cathode
cathodecoolingconcept
Review IB: CERAMIC HONEYCOMB CATHODE:Cathode Action Plan as of March 2006
Velvet Carbon
10 k shots...lots of burn marks31 k shots...no change
ESLI (Energy Sciences Laboratories Inc.)
SEM SEM
New all Carbon Emitter has increased Cathode Lifetime …… 31 k shots total,
24,978 continuous @ 2.5 Hz
Motivation for Beginning Focal Profile Experiments
• Nike Laser System (Single Shot) – ISI smooth focal profiles
• Rep-Rate Considerations– Possible Additional Phase
Aberrations• Recirculator baseline gas flow• Leftover energy (pressure gradients)
from last shot• Foil Temperature (Boundary Layer)• Gas Temperature after one roundtrip
of recirculator
Focal Profile after E-Beam Single Shot with NO RECIRCULATOR FLOW
0
200
400
600
800
1000
1200
1400
1600
600 650 700 750 800Pixel #
Inte
nsit
y (
no
rmali
zed
)
5 secs
10 secs
30 secs
E-Beam Fires at Time Zero
0Time (s)
5 10 30
main amp 30 cm x 30 cm seed osc 1cm x 3 cm
Focal Profile Floor Layout
ApertureMay 2006
Beam size:15 cm x15 cm
Schematic of “Pseudo ISI” Essential Optical Elements for focal profile studies
Recorded Image
0
500
1000
1500
2000
2500
600 650 700 750 800
Pixel #
Inte
ns
ity
(a
rb.)
NanoStarCamera
LPX 305 iNot ISI Source
PinholeAmplifier
6 meter focal length lens 248 nmLineout Image
500 microns
Probe Beam No E-Beam Probe Beam with E-Beam 1 Hz390 ms after
30 shots 1 Hz Focal Profile Measurement (“Pseudo ISI”)
Time (s)0 1 2 3
Time(s)
E-Beam Probe
0 .39 1 1.39 2 2.39
Probe
0
500
1000
1500
2000
2500
3000
3500
940 950 960 970 980 990 1000Pixel #
Inte
nsi
ty (
no
rmal
ized
)
Shot 1
Shot 5
Shot 10
Shot 15
Shot 20
Shot 25
Shot 30
0
500
1000
1500
2000
2500
3000
3500
940 950 960 970 980 990 1000Pixel #
Inte
nsi
ty (
no
rmal
ized
)
Shot 1
Shot 5
Shot 10
Shot 15
Shot 20
Shot 25
Shot 30
500 microns
E-Beam 1 HzProbe Beam 390 ms after
E-Beam 2.5 HzProbe Beam 390 ms after
1 Hz and 2.5 Hz Rep-Rate Focal Profile Lineouts (“Pseudo ISI”)
30 shot measurement bursts (gas cycle time of recirculator ~5 secs)
Time(s)
E-Beam Probe
0 .39 1 1.39 2 2.39Time(s)
E-Beam Probe
0 .39 .8 2 2.39
0
500
1000
1500
2000
2500
940 950 960 970 980 990 1000
Distance (pixels)
Inte
ns
ity
(a
rb.)
10 s
1 s
400 ms
200 ms
50 ms
25 ms
Focal Profile Single Shot Lineouts (“Pseudo ISI”)
E-Beam Fires at Time Zero
Time
1 s400 ms200 ms50 ms25 ms 10 s0
Electra Pre-Amplifier Laser Experiments
LPX 305 i Input 0.5 J10 cm x 10 cm
Cylindrical lens Pair
Telescope
1 cm x 3 cm
3 cm x 3 cm
Calorimeter
0.0
5.0
10.0
15.0
20.0
25.0
30.0
8 12 16 20Pressure (psi)
Las
er O
utp
ut
(J)
Orestes 0.5 J Input
Measured Input ~0.5 J
Orestes Prediction (0.5 J input)Measured Output (~0.5 J input)
First light on Electra Pre-Amp
80% Ar, 0.3% Fluorine
• Cathode Rep-rate & Durability:– Installed Carbon Emitter
• 2.5 Hz 24,978 shots (continuous)
• Beginning Rep-Rate Focal Profile Experiments– Single shot Recovery of Recirculator less than 200 ms
(Necessary Time for 5 Hz Operation)
• First Light Electra Pre-Amplifier – 23 J laser output
Summary Since Last HAPL Meeting
Next Steps Based on Results
• Cathode Rep-rate & Durability:• Cool the cathode• Modify the cathode construction to eliminate weak spots• Replace cordierite ceramic with more robust SiC or YZA
(yttria stabilized zirconia-alumina)• Eliminate cathode shroud
• Rep-Rate Focal Profile Experiments• Interferometer• Examine all of Aperture
• Pre-Amplifier Laser • Integrate into the full laser system
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