development of a high-energy seed for contrast improvement of the vulcan laser facility. ian...
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![Page 1: Development of a High-Energy Seed for Contrast Improvement of the Vulcan Laser Facility. Ian Musgrave, W. Shaikh, M. Galimberti, A. Boyle, K Lancaster,](https://reader036.vdocuments.us/reader036/viewer/2022070307/551b779f550346d31b8b63d6/html5/thumbnails/1.jpg)
Development of a High-Energy Seed for Contrast Improvement of the Vulcan Laser
Facility.
Ian Musgrave, W. Shaikh, M. Galimberti, A. Boyle, K
Lancaster, C. Hernandez-Gomez, R. Heathcote.
Central Laser Facility, STFC, Rutherford Appleton Laboratory, UK
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The Vulcan laser Facility
• Nd Glass Laser• 8 Beam CPA Laser• 3 Target Areas• 3 kJ Energy• 1 PW Power
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Vulcan Petawatt
PCF
Ti:S
BBO BBO BBO
Pump
Stretcher
F
F
Compressor
x3 208mm Nova disc amplifiers
16mm Phosphate rod
25mm phosphate rod 45mm Phosphate rod
Adaptive optic
Double pass 108mm phosphate disc
150mm disc
Beam diagnosticsBeam diagnostics+wavefront sensor
Interaction chamber
9mm silicate rod Double pass 16mm silicate rod
F
• Single stretch to 4.5ns• Combination of OPCPA and mixed glass amplifiers for
amplification
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Existing PW facility ASE contrast
• Previously used photo-diodes to investigate the ASE contrast of the Vulcan PW facility gave a baseline of ~108 for the ns ASE.
• These have shown that the ASE is seeded by the pump pulse of the OPCPA, used NF apertures to limit fluorescence.
-1.0E-06
0.0E+00
1.0E-06
2.0E-06
3.0E-06
4.0E-06
5.0E-06
6.0E-06
7.0E-06
95 96 97 98 99 100 101 102
Time (ns)
Le
ve
l re
lativ
e to
ma
in p
uls
e
silicate no aperture
1.1mm aperture after stage 1
1.0mm aperture after stage 1
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Introduce High Energy Seed
•Introduce a single stage of amplification before main stretch. •Reduce the amount of nanosecond gain.•Use PS OPCPA
•Limited ASE window•Double reflections won’t be amplified
•Requires optically synchronised pump beam•No recompression or cleaning
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Single stage PS OPCPATi:Sapphire
SeedRegenerativeAmplifier
2w
BBO
Pulse Length Control
Timing Control
• Common seed for signal and pump pulses-optically synchronised
• Gain Narrowing in Nd:YLF amplifier increases pulses to ~10ps
• Stretcher in signal beam enables pulse length matching
500J
1mm
15mm
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PS OPCPA Performance
1010 1020 1030 1040 1050 1060 1070 1080
1000
1500
2000
Inte
nsi
ty -
arb
un
its
Wavelength nm
• Demonstrated full amplification of seed laser at > 20nm
• SSG~106 at peak of pump• 120μJ for <1nJ input ~ 40% conversion of pump
to signal and idler• Operates in a saturated regime• Measured RMS pulse to pulse stability ~1%
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High and Low Energy Seed operation of the ns OPCPA
Output SSG SSG SSG Input
10mJ 102 103 103 <1nJ
15mJ 102 103 0 ~20μJ
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ASE contrast Measurements
•Relayed a beam out of the interaction chamber•Used single-shot AC to confirm compression•Optics limit the energy to just the rod amplifier chain
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Ns Contrast Measurements
• Used a combination of a water cell and diodes to obtain a dynamic range of ~1010
• Scattering from collimating optic used as timing marker.
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• Pick Off beam at injection to rod chain• Relay and expand beam before injecting into the
TAP compressor
Contrast Measurement of the CPA and OPCPA systems
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Sequoia Measurements
•Using same beam line as the diode traces•Running both OPCPAs but no rods or disks
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Fluorescence from the Pump
• FT of Clipped spectrum in stretcher gives steep gradient for contrast
• Pump pulse varies in time.• SSG and therefore the PF will vary with the
pump pulse intensity
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CPA beam
Long pulse
RCF stack
Reflected energy monitor
Optical probe
2x HOPG2-D Ka imaging
X-ray multi-pinhole camera
Same energy on target in all cases
0
5
10
15
20
25
30
35
40
0 50 100 150
Long pulse energy (J)
Max
imum
pro
ton
ener
gy (
MeV
)
2010: With plasma mirror
2010: Without plasma mirror
2008: With plasma mirror
First Experimental Data
Courtesy of P.McKenna
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Conclusions
Original ASE Contrast
New ASE Contrast
• Demonstrated a ps OPCPA that has improved the ns ASE contrast by at least 2 orders of magnitude.
• Characterised the close in contrast.• Successfully delivered for user experiments