Laser pulse: 270mJ Argon, 20sccm, 2kV

visible EUV Scattered 10.6 µm difference

+0mm

+5mm

+10mm

+15mm

+20mm

Argon (16 sccm)

Oxygen (20 sccm) Xenon (4 sccm)

Gas discharge source

Charging voltage: 2 kV

Stored energy: 2.2 J

Gases: Xe, Ar, O2, N2

Pressure: 0.5-2 Pa

Pulsed CO2 TEA-Laser

Wavelength: 10.6 µm

Pulse length: 100 ns

Pulse energy: <1 J

Pressure: 700-950 mbar

EUV Metrology

Image or spectrum, diode

Far-IR Metrology

Transmission, image

Electric Metrology

dI/dt, timing

Absorption length (𝛼𝑒𝑖−1) for 10.6 µm

IntroductionThe approach of laser heated discharge plasma (LHDP) is based on the idea

to combine the most common plasma-based methods for EUV generation. It

utilizes an electrically generated compressed plasma pinch (DPP) as target

for additional heating by intense laser radiation (LPP). Possible advantages

are increased brilliance, stabilization of the pinch process, extension of

spectral range and higher power at shorter wavelengths.

We report on the current state and results of the experimental setup. It

consists of a modified gas discharge source that produces a compressed

plasma pinch [1], with which the pulse of a CO2 TEA laser with 10.6 µm

wavelength and up to 1 Joule pulse energy is synchronized. The laser beam

is focused onto the pinch plasma. The implementation of a far infrared

heating laser allows for more efficient laser-plasma interaction compared to

prior experiments [2]. Reflected and scattered laser light is utilized to probe

the plasma properties. Impact of laser radiation on pinch dynamics and EUV

spectra (5-20 nm) of different gasses is discussed.

Advances in laser heated discharge plasmaFlorian Melsheimer1,2,3,4, Detlev Grützmacher2,4,5, Larissa Juschkin1,2,4

Theory• Hollow cathode triggered gas discharge EUV source produces

compressed plasma pinch (ne≈3∙1018 cm-3, Te≈15-30 eV)

• Intense laser pulse (λ=10.6 µm) is focused at pinch

• Absorption via electron-ion invers Bremsstrahlung (→ 𝛼𝑒𝑖)

• Stronger in high density regions (stabilization)

• Compensation of radiative cooling [3]

Experimental setup

ResultsTransmission of the laser pulse is quenched by the emerging plasma.

Drag detector at front additionally picks up scattered light.

Pinch images in different spectral ranges. Argon (flow 16 sccm) recorded in

visible range (DSLR), EUV pinhole camera (30 µm aperture, range 17-80 nm)

and scattered 10.6 µm radiation (200 mm fl. lens). 100 shots averaged.

The impact on EUV emission is presented as absolute difference of EUV

images in counts.

Summary and Outlook

𝛼𝑒𝑖 =𝑛𝑒2𝑒6

6 3𝑛ℇ03𝑐ℏ𝜔𝐿

3𝑚𝑒2

𝑚𝑒

2𝜋𝑘𝐵𝑇𝑒1 − exp

−ℏ𝜔𝐿

𝑘𝐵𝑇𝑒ҧ𝑔

[1] Bergmann, Klaus et. Al. (2008). Soft x-ray emission from a pulsed gas discharge in a pseudosparklike electrode geometry. Journal of Applied Physics. 103. 123304 - 123304. 10.1063/1.2940786.[2] 2015 International Workshop on EUV and Soft X-Ray Sources, S33[3] S. Brückner, S. Wieneke and W. Viöl, „Generation of Double Pulses in the Extreme Ultraviolet Spectral Range Using a Laser Combined Pinch Plasma Source“, The Open Plasma Physics Journal, 2009, 2, 17-23

ωL, laser frequency

n, real part of the refractive index

g, averaged Gaunt-factor

EUV-CCD

Pyrocam

Drag detector

Brewster window

500 mm FL

200 mm FLadj. iris

30 µm pinhole250 nm Al-filter

Beam dump

Drag detector

2x ExpanderAttenuatorPeriscope

TEA-LaserCO2, N2, H

adj. iris

1. RWTH Aachen University, Experimental Physics of EUV, Steinbachstr. 15, 52074 Aachen, Germany2. Forschungszentrum Jülich GmbH, Institute for Semiconductor Nanoelectronics, Peter Grünberg Institut-9, 52425 Jülich

Germany

3. Fraunhofer Institute for Laser Technology, Steinbachstraße 15, 52074 Aachen, Germany4. JARA-FIT, Forschungszentrum Jülich GmbH and RWTH Aachen University, Germany5. Forschungszentrum Jülich GmbH, JARA-Institute for Green-IT, Peter Grünberg Institute -10, 52425 Jülich, Germany

Acknowledgment Larissa Juschkin acknowledges financial support by the Helmholtz Association for a Helmholtz professorship as a part of the Initiative and

Networking Fund. We acknowledge the support of ASML and Wim van der Zande for our current laser heated discharge plasma project.

A focus sweep in 5 mm

steps depicts the influence

on scattering.

The emission of the broad

pinch of oxygen is increased

over the entire volume, not

limited to the focal point.

difference

Oxygen (20 sccm)

Argon (16 sccm)

Coupling of a 300 mJ laser pulse

into different gas pinches enhances

the EUV emission at certain

frequencies by up to ~30 %.

• Investigate scaling of effect

• Add amplifier module for >1 J/pulse

• Modify chamber for simultaneous

diode measurements

• Spatially resolved spectra

• Laser coupling enhances EUV

emission

• Effect on plasma is non localized

• Quenching of laser transmission

is observed

Electron-ion invers Bremsstrahlung absorption

coefficient: