Ultrashort pulsed laser sources generating pulse trains (bursts) with intra-burst repetition rates in the MHz and the GHz regime enable an efficient production of microstructures with a high surface quality. However, x-ray radiation can be generated during the laser micromachining using large intensities of the laser radiation and its interaction with the ablation cloud or high-density plasma. Therefore, the authors report on the interaction of bursts with a wavelength of 1030 nm and pulse durations of 0.24 and 10 ps with intra-burst repetition rates of 65 MHz (MHz-burst mode) and 2.5 GHz (GHz-burst mode) as well as a combination of both burst modes, called BiBurst mode, with stainless steel, and the x-rays are generated. The x-ray dose rates determined in the respective burst modes are compared and discussed with those of conventional ultrafast laser radiation (single-pulse mode). Furthermore, a theoretical model is used to calculate the expected x-ray dose rates. In the investigated parameter range, the highest dose rates of more than Sv/h are determined at a specific burst setting. Compared to the single-pulse mode, significantly higher dose rates are determined using the burst mode with the same total intensity. Based on the results of this study, it can be stated that the interaction of ultrafast laser radiation in the burst mode with a generated ablation cloud or high-density plasma plays a major role in x-ray generation and the resulting x-ray dose rates.
REFERENCES
1.
R.
Weber
, C.
Freitag
, T. V.
Kononenko
, M.
Hafner
, V.
Onuseit
, P.
Berger
, and T.
Graf
, “Short-pulse laser processing of CFRP
,” Phys. Procedia
39
, 137
–146
(2012
). 2.
G.
Raciukaitis
, M.
Brikas
, P.
Gecys
, and M.
Gedvilas
, “Accumulation effects in laser ablation of metals with high-repetition-rate lasers,” in High-Power Laser Ablation VII (International Society for Optics and Photonics, Taos, NM, 2008), Vol. 7005, p. 70052L.3.
G.
Raciukaitis
, “Use of high repetition rate and high power lasers in microfabrication: How to keep the efficiency high?
,” J. Laser Micro Nanoeng.
4
, 186
–191
(2009
). 4.
M. M.
Murnane
, H. C.
Kapteyn
, M. D.
Rosen
, and R. W.
Falcone
, “Ultrafast G-ray pulses from laser-produced plasmas
,” Science
251
, 531
–536
(1991
). 5.
Y.
Jiang
, T.
Lee
, W.
Li
, G.
Ketwaroo
, and C. G.
Rose-Petruck
, “High-average-power 2-kHz laser for generation of ultrashort X-ray pulses
,” Opt. Lett.
27
, 963
–965
(2002
). 6.
N.
Zhavoronkov
, Y.
Gritsai
, M.
Bargheer
, M.
Woerner
, T.
Elsaesser
, F.
Zamponi
, I.
Uschmann
, and E.
Förster
, “Microfocus Cu K? Source for femtosecond X-ray science
,” Opt. Lett.
30
, 1737
–1739
(2005
). 7.
F.
Zamponi
et al., “Femtosecond hard X-ray plasma sources with a kilohertz repetition rate
,” Appl. Phys. A
96
, 51
–58
(2009
). 8.
W.
Lu
et al., “Optimized K X-ray flashes from femtosecond-laser-irradiated foils
,” Phys. Rev. E
80
, 026404
(2009
). 9.
J.
Weisshaupt
et al., “High-brightness table-top hard X-ray source driven by sub-100-femtosecond mid-infrared pulses
,” Nat. Photonics
8
, 927
–930
(2014
). 10.
A.
Rousse
, C.
Rischel
, and J.-C.
Gauthier
, “Femtosecond X-ray crystallography
,” Rev. Mod. Phys.
73
, 17
–31
(2001
). 11.
C.
Bressler
and M.
Chergui
, “Ultrafast X-ray absorption spectroscopy
,” Chem. Rev.
104
, 1781
–1812
(2004
). 12.
M.
Bargheer
, N.
Zhavoronkov
, M.
Woerner
, and T.
Elsaesser
, “Recent progress in ultrafast X-ray diffraction.
,” Chemphyschem
7
, 783
–792
(2006
). 13.
C.
Bostedt
et al., “Ultra-fast and ultra-intense X-ray sciences: First results from the Linac Coherent Light Source free-electron laser
,” J. Phys. B
46
, 164003
(2013
). 14.
T.
Lee
, Y.
Jiang
, C. G.
Rose-Petruck
, and F.
Benesch
, “Ultrafast tabletop laser-pump-X-ray probe measurement of solvated Fe
,” J. Chem. Phys.
122
, 084506
(2005
). 15.
K.
Holldack
et al., “Femtospex: A versatile optical pump-soft X-ray probe facility with 100 fs X-ray pulses of variable polarization
,” J. Synchrotron Radiat.
21
, 1090
–1104
(2014
). 16.
J.
Götzfried
et al., “Research towards high-repetition rate laser-driven X-ray sources for imaging applications
,” Nucl. Instrum. Methods Phys. Res. Sect. A
909
, 286
–289
(2018
). 17.
G.
Bonamis
, K.
Mishchick
, E.
Audouard
, C.
Hönninger
, E.
Mottay
, J.
Lopez
, and I.
Manek-Hönninger
, “High efficiency femtosecond laser ablation with gigahertz level bursts
,” J. Laser Appl.
31
, 022205
(2019
). 18.
P.
Elahi
, H.
Kalaycioğlu
, Ö.
Akçaalan
, Ç.
Şenel
, and F.
Ömer Ilday
, “Burst-mode thulium all-fiber laser delivering femtosecond pulses at GHz intra-burst repetition rate
,” Opt. Lett.
42
, 3808
–3811
(2017
). 19.
P.
Lickschat
, A.
Demba
, and S.
Weissmantel
, “Ablation of steel using picosecond laser pulses in burst mode
,” Appl. Phys. A
123
, 137
(2017
). 20.
A.
Žemaitis
, P.
Gečys
, M.
Barkauskas
, G.
Račiukaitis
, and M.
Gedvilas
, “Highly-efficient laser ablation of copper by bursts of ultrashort tuneable (fs-ps) pulses
,” Sci. Rep.
9
, 1
–8
(2019
). 21.
D.
Metzner
, P.
Lickschat
, and S.
Weißmantel
, “Investigations of qualitative aspects with burst mode ablation of silicon and cemented tungsten carbide
,” Appl. Phys. A
125
, 1
–6
(2019
).22.
B.
Neuenschwander
, T.
Kramer
, B.
Lauer
, and B.
Jaeggi
, “Burst mode with ps-and fs-pulses: Influence on the removal rate, surface quality, and heat accumulation,” in Laser Applications in Microelectronic and Optoelectronic Manufacturing (LAMOM) XX (International Society for Optics and Photonics, San Francisco, CA, 2015), Vol. 9350, p. 93500U.23.
D. J.
Förster
, S.
Faas
, S.
Gröninger
, F.
Bauer
, A.
Michalowski
, R.
Weber
, and T.
Graf
, “Shielding effects and re-deposition of material during processing of metals with bursts of ultra-short laser pulses
,” Appl. Surf. Sci.
440
, 926
–931
(2018
). 24.
A. A.
Foumani
, D. J.
Förster
, H.
Ghorbanfekr
, R.
Weber
, T.
Graf
, and A. R.
Niknam
, “Atomistic simulation of ultra-short pulsed laser ablation of metals with single and double pulses: An investigation of the re-deposition phenomenon
,” Appl. Surf. Sci.
537
, 147775
(2021
). 25.
K.
Obata
, F.
Caballero-Lucas
, and K.
Sugioka
, “Material processing at GHz burst mode by femtosecond laser ablation
,” J. Laser Micro Nanoeng.
16
, 19
–23
(2021
). 26.
D.
Metzner
, P.
Lickschat
, and S.
Weißmantel
, “High-quality surface treatment using GHz burst mode with tunable ultrashort pulses
,” Appl. Surf. Sci.
531
, 147270
(2020
). 27.
T.
Hirsiger
, M.
Gafner
, S.
Remund
, M. V.
Chaja
, A.
Urniezius
, S.
Butkus
, and B.
Neuenschwander
, “Machining metals and silicon with GHz bursts: Surprising tremendous reduction of the specific removal rate for surface texturing applications,” in Laser Applications in Microelectronic and Optoelectronic Manufacturing (LAMOM) XXV (International Society for Optics and Photonics, San Fransisco, CA, 2020), Vol. 11267, p. 112670T.28.
H.
Legall
, C.
Schwanke
, S.
Pentzien
, G.
Dittmar
, J.
Bonse
, and J.
Krüger
, “X-ray emission as a potential hazard during ultrashort pulse laser material processing
,” Appl. Phys. A
124
, 1
–8
(2018
). 29.
S.
Mattsson
and M.
Söderberg
, “Dose quantities and units for radiation protection,” in Radiation Protection in Nuclear Medicine (Springer, New York, 2013), pp. 7–18.30.
M. J.
Wesolowski
et al., “X-ray dosimetry during low-intensity femtosecond laser ablation of molybdenum in ambient conditions
,” IEEE Trans. Nucl. Sci.
64
, 2519
–2522
(2017
). 31.
R.
Weber
, R.
Giedl-Wagner
, D. J.
Förster
, A.
Pauli
, T.
Graf
, and J. E.
Balmer
, “Expected X-ray dose rates resulting from industrial ultrafast laser applications
,” Appl. Phys. A
125
, 1
–12
(2019
). 32.
R.
Behrens
, B.
Pullner
, and M.
Reginatto
, “X-ray emission from materials processing lasers
,” Radiat. Prot. Dosimetry
183
, 361
–374
(2019
). 33.
H.
Legall
, C.
Schwanke
, J.
Bonse
, and J.
Krüger
, “The influence of processing parameters on X-ray emission during ultra-short pulse laser machining
,” Appl. Phys. A
125
, 1
–8
(2019
). 34.
C.
Freitag
and R.
Giedl-Wagner
, “X-ray protection in an industrial production environment: Industrial implementation of the requirements of the German radiation protection act
,” PhotonicsViews
17
, 37
–41
(2020
). 35.
J.
Prieto-Pena
, F.
Gomez
, D.
Gonzalez-Castano
, M.
Flores-Arias
, J.
Arines
, C.
Bao-Varela
, F.
Cambronero-López
, and A. M.
Maqueira
, “Radiation characterisation and dosimetric measurements of a femtosecond pulsed laser ablation system
,” J. Radiol. Prot.
38
, 716
–730
(2018
). 36.
I.
Artyukov
, D.
Zayarniy
, A. A.
Ionin
, S. I.
Kudryashov
, S. V.
Makarov
, and P. N.
Saltuganov
, “Relaxation phenomena in electronic and lattice subsystems on iron surface during its ablation by ultrashort laser pulses
,” JETP Lett.
99
, 51
–55
(2014
). 37.
N. A.
Smirnov
et al., “Microprocessing of a steel surface by single pulses of variable width
,” Laser Phys. Lett.
16
, 056002
(2019
). 38.
D.
Metzner
, M.
Olbrich
, P.
Lickschat
, A.
Horn
, and S.
Weißmantel
, “Experimental and theoretical determination of the effective penetration depth of ultrafast laser radiation in stainless steel
,” Lasers Manuf. Mater. Process.
7
, 478
–495
(2020
). 39.
P.
Lickschat
, D.
Metzner
, and S.
Weißmantel
, “Fundamental investigations of ultrashort pulsed laser ablation on stainless steel and cemented tungsten carbide
,” Int. J. Adv. Manuf. Technol.
109
, 1167
–1175
(2020
). 40.
R.
Mayerhofer
, “Ultrashort-pulsed laser material processing with high repetition rate burst pulses
,” in Laser Applications in Microelectronic and Optoelectronic Manufacturing (LAMOM) XXII
edited by B. Neuenschwander, C. P. Grigoropoulos, T. Makimura, and G. Račiukaitis (SPIE, 2017), Vol. 10091, pp. 192-201
. 41.
D.
Metzner
, P.
Lickschat
, and S.
Weißmantel
, “Optimization of the ablation process using ultrashort pulsed laser radiation in different burst modes
,” J. Laser Appl.
33
, 012057
(2021
). 42.
P.
Lickschat
, D.
Metzner
, and S.
Weißmantel
, “Burst mode ablation of stainless steel with tunable ultrashort laser pulses
,” J. Laser Appl.
33
, 022005
(2021
). 43.
Technical description, User manual by the manufacturer, Ortsdosimeter OD-02 OD-02 Hx (2016).
44.
“Procedures of dosimetry with probe-type detectors for photon and electron radiation—Part 2: Ionization chamber dosimetry of high energy photon and electron radiation” (Beuth, 2020).
45.
“AAPM’s TG-51 protocol for clinical reference dosimetry of high-energy photon and electron beams,” Report No. 067 (1999).
46.
J.-H.
Grunert
, “Rechtsvorschriften, richtlinien, leitlinien und empfehlungen,” in Strahlenschutz für Röntgendiagnostik und Computertomografie (Springer, New York, 2019), pp. 79–84.47.
R.
Le Harzic
et al., “Pulse width and energy influence on laser micromachining of metals in a range of 100 fs to 5 ps
,” Appl. Surf. Sci.
249
, 322
–331
(2005
). 48.
See the supplementary material at https://www.scitation.org/doi/suppl/10.2351/7.0000403 for the theoretical model for calculating the expected x-ray dose rates. The results obtained are compared and discussed with the experimentally measured x-ray dose rates in Secs. III A and III C.
49.
P.
Ding
, Q.
Liu
, X.
Lu
, X.
Liu
, S.
Sun
, Z.
Liu
, B.
Hu
, and Y.
Li
, “Hydrodynamic simulation of silicon ablation by ultrashort laser irradiation
,” Nucl. Instrum. Methods Phys. Res. Sect. B
286
, 40
–44
(2012
). 50.
J.
Penczak
, R.
Kupfer
, I.
Bar
, and R. J.
Gordon
, “The role of plasma shielding in collinear double-pulse femtosecond laser-induced breakdown spectroscopy
,” Spectrochim. Acta Part B
97
, 34
–41
(2014
). 51.
S.
Tan
, J.
Wu
, Y.
Zhang
, M.
Wang
, and Y.
Ou
, “A model of ultra-short pulsed laser ablation of metal with considering plasma shielding and non-Fourier effect
,” Energies
11
, 3163
(2018
). © 2021 Author(s). Published under an exclusive license by Laser Institute of America.
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