Soft X-ray spectroscopy and microscopy using

a table-top laser-induced plasma sourceM. Müller, J. Holburg, K. MannLaser-Laboratorium Göttingen e. V., Hans-Adolf-Krebs-Weg 1, D-37077 Göttingen

matthias.mueller@llg-ev.de

Introduction

The progress in development of

laboratory-scale soft X-ray sources in

recent years has enabled experimental

techniques that could be performed

before almost exclusively at

synchrotrons. Here, we present two

applications of a compact, long-term

stable and nearly debris-free laser-

induced plasma source based on a

pulsed gas jet target: Broadband

radiation is used for polychromatic

absorption spectroscopy in the ‘waterwindow´ spectral region, investigating

the fine-structure of absorption edges

that reveals information e.g. about type

of bonds, oxidation states and

coordination. The performance of this

NEXAFS spectrometer is demonstrated

for different organic and inorganic

samples probing the K- and L-edges of

carbon, calcium, oxygen, manganese,

and iron. On the other hand,

monochromatic radiation at a

wavelength of λ = 2.88 nm produced

from a nitrogen plasma is employed for

soft X-ray transmission microscopy,

accomplishing a spatial resolution of

about 50 nm.

Research Results

References / Funding

NEXAFS spectroscopy

Polychromatic radiation (λ = 1 – 5 nm) [6,7]

Elemental and compositional analysis (C, Ca, N, O, Mn, Fe, Pr, …)

Pump-probe experiments (proof of principle) [8]

Compact soft X-ray microscope [4,5]

Monochromatic radiation at λ = 2.88 nm

Spatial resolution ≈ 50 nm

Bacterium Deinococcus

radiodurans

1 m

≈ 108 photons/pulse

(FOV 100 µm)

Alga Trachelomonas

oblonga

30 mm

[1] M. Müller, F. C. Kühl, P. Großmann, P. Vrba, and K. Mann. Emission properties of ns and ps laser-induced soft x-ray

sources using pulsed gas jets. Optics Expr. 21(10), 2013.

[2] T. Mey, M. Rein, P. Großmann, and K. Mann. Brilliance improvement of laser-produced soft x-ray plasma by a

barrel shock. New J. Phys. 14(7), 2012.

[3] J. Holburg, M. Müller, S. Wieneke, and K. Mann. Brilliance improvement of laser-produced EUV/SXR plasmas

based on pulsed gas jets. JVST A, submitted, 2018.

[4] M. Müller, T. Mey, J. Niemeyer, and K. Mann. Table-top soft x-ray microscope using laser-induced plasma from a

pulsed gas jet. Optics Expr. 22(19), 2014.

[5] M. Müller, T. Mey, J. Niemeyer, M. Lorenz, and K. Mann. Table-top soft x-ray microscopy with a laser-induced

plasma source based on a pulsed gas-jet. AIP Conf. Proc. 1764, 2016.

[6] C. Peth, F. Barkusky, and K. Mann. Near-edge X-ray absorption fine structure Measurements using a laboratory-

scale XUV source. J. Phys. D 41, 2008.

[7] J. Sedlmair. Soft X-ray Spectromicroscopy of Environmental and Biological Samples. PhD thesis, Universität

Göttingen, 2011.

[8] P. Großmann, I. Rajkovic, R. More, J. Norpoth, S. Techert, C. Jooss, and K. Mann. Time-resolved near-edge x-ray

absorption fine structure spectroscopy on photo-induced phase transitions using a table-top soft-x-ray

spectrometer. Rev. Sci. Instrum. 83(5), 2012.

[9] F. Kühl, M. Müller, M. Schellhorn, S. Wieneke, K. Eusterhues, and K. Mann. Near-edge x-ray absorption fine

structure spectroscopy at atmospheric pressure with a table-top laser-induced soft x-ray source. JVST A, 34(4),

2016.

Laser-driven soft X-ray source

Low debris generation

Long-term stability

Continuous supply of target material

Improvement of plasma brilliance

Enhancement of local gas density by

• generation of a “barrel-shock” [2]

• high pressure gas jet (20 bar 200 bar)

• angular emission characteristics [3]

Employment of high power lasers with

• picosecond pulse duration [1]

• high repetition rate (< 10 ps, > 1 kHz, > 100 W)

Peak brilliance at 2.88 nm

≈ 1018 ph/(s*mrad2*mm2) [1]

Soft X-ray coherent diffractive imaging (CDI) at λ = 2.88 nm

Convolution of far-field diffraction pattern with Gaussian function

Van Cittert-Zernike theorem: lc ≈ 13.3 µm

Diffraction data: lc,exp ≈ 13.2 µm

Methods

average electron

temperature

average electron

density

ns laser 50.3 eV 66.3 eV

ps laser 7.0·1019 e/cm³ 22.4·1019 e/cm³

Inte

nsity

[a.u

.]

0

1

Pinhole camera image

of nitrogen plasma

nitrogen emission spectrum

sample: 10 µm pinhole

Samples under atmospheric conditions [9]

Photon energy [eV] Photon energy [eV]Photon energy [eV]

Photon energy [eV] higher overall intensity

shift to higher photon energies

Photon energy [eV]

Photon energy [eV]Photon energy [eV]

Op

tica

l d

en

sity

[a.u

.]O

ptica

l d

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[a.u

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Op

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[a.u

.]O

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[a.u

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Optical density

[a.u

.]

Optical density

[a.u

.]

Inte

nsity

[10

6C

ounts

]

Inte

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[Cou

nts

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Photon energy [eV]