Isao MATSUSHIMA, Hidehiko YASHIRO, Toshihisa TOMIE

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10 kHz 54 W Tisapphire regenerative amplifier
as a pumping laser of a laser-plasma X-ray source
Isao MATSUSHIMA, Hidehiko YASHIRO, Toshihisa
TOMIE National Institute of Advanced Industrial
Science and Technology (AIST) C2 1-1-1, Umezono,
Tsukuba, 3058568, Japan
Laser system for laser-plasma X-ray source
This study was partly financially supported by
the Budget for Nuclear Research of the Ministry
of Education, Culture, Sports, Science and
Technology, based on screening and counseling by
the Atomic Energy Commission.
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Laser-Plasma X-ray Source
X-ray, ?nm, ltns blight point source
Laser
Target
Plasma High Temperature lt100µm?, Ionization gtps,
gtgtmJ, 10µm? pslttltns
gt1011 W/cm2
EUPS extreme ultraviolet (EUV) excited
photoelectron spectroscopy EUV source for defect
inspection of multi-layered mask blanks EUV
lithography X-ray microscopy of living cells
multi kHz repetition-rate is required for high
throughput
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Our Application of Laser-Plasma
EUPS extreme ultraviolet (EUV) excited
photoelectron spectroscopy
Laser-Plasma EVU Source
Novel surface analysis Energy resolution better
than 0.3 eV Spatial resolution better than 1 µm
EUPS4
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High-average power TiSapphire regenerative
amplifier
Key Technologies

• Thermal lensing effect
• Symmetric ring resonator
• Low loss and high gain
• High-quality pump beam

Cryogenic cooling Good beam quality High
efficiency Mode-volume matching
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High-average power TiSapphire regenerative
amplifier
Fig. 1. Schematic drawing of a ring regenerative
amplifier. A cryogenic-cooled Tisapphire rod is
kept in a vacuum cell and placed at the beam
waist for f 1 m intra-cavity lens. M1 M6 are
cavity mirrors ?/2 is a half-wave plate PC is a
Pockels cell TFP is a thin film polarizer FI is
a Faraday isolators and AO2/G is a pump laser.
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Pump Laser
for high gain
AO2/G (PowerLase) 2

• High repetition rate 10 kHz

• High pulse energy 8mJ x 2

• Good beam quality M223.5

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reduce thermal lens
Cryogenic Cooling
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10 kHz TiSapphire regenerative amplifier
Fig. 3. Output power of the regenerative
amplifier at 10 kHz as a function of pump power.
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Discussion
Scale up to kW?

• High power pumping green laser
• Cryogenic cooling for kW

decrease in conversion efficiency
un-known non-linear losses at high pumping power
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Summary
High average power and pulse energy
54W outout
10kHz 180W Pump
before cpmpression
5.4 mJ/pulse
2XDL ? gt80Energy Compressability 82fs
conversion efficiency 30

• The highest output power in the world
• from a single stage single rod kHz TiSap regen
• Scalability to higher output power was discussed.

Acknowledgments The liquid nitrogen cryogenic
cooling system was designed with advices from
AIST Cryogenic Technical Center.
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Requirements of lasers for x-ray generation

• Pulse Energy Multi-mJ
• Repetition rate Multi-kHz
• Focusability a few µm
• Minimum pulse duration 100fs
• High-efficiency
• Small and simple