TY - CONF A1 - Krüger, Jörg T1 - Undesired X-ray emission during ultrashort pulse laser material processing N2 - The use of ultrashort laser pulses for material processing in air has many advantages. Due to the progressive development in the laser sector, average powers in the kW range with pulse repetition rates exceeding the MHz-level are available. The machining with high-intensity laser pulses can be accompanied by the generation of a near-surface electron plasma due to absorption and ionization of the material, a subsequent plasma heating by the laser pulse, and finally an interaction of “hot” plasma electrons with the workpiece leading to continuous and characteristic X-ray radiation. The amount of this unwanted X-ray radiation is determined by the laser parameters (pulse duration, intensity, wavelength, polarization), the workpiece (atomic number, surface preparation), and the laser process management (scanning or stationary regime, laser turning). The use of laser intensities above 10^13 W/cm^2 in combination with laser pulse repetition rates in the few 100 kHz-range can lead to X-ray dose rates exceeding the permitted X-ray limits for members of the public. Especially the materials tungsten and steel show significant X-ray emission. Recently, the current state of the art in the field of undesired generation of X-ray radiation during ultrashort pulse laser processing in air was reviewed. In this presentation, important aspects of the measured X-ray doses, X-ray spectra, and practical issues of radiation protection are discussed. T2 - 28th International Conference on Advanced Laser Technologies (ALT'21) CY - Online meeting DA - 06.09.2021 KW - Ultrashort laser pulses KW - Material processing KW - X-ray emission KW - Radiation protection PY - 2021 AN - OPUS4-53241 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Krüger, Jörg T1 - Unerwünschte Röntgenemission bei der UKP-Lasermaterialbearbeitung N2 - Der Vortrag fasst aktuelle Aspekte zum unerwünschten Auftreten von Röntgenstrahlung bei der Ultrakurzpuls-Lasermaterialbearbeitung zusammen. Es werden Einflussparameter, Grenzwerte, Schutzmaßnahmen, Fragen der Abschirmung und rechtliche Gesichtspunkte diskutiert. T2 - Bayerische Laserschutztage 2022 CY - Online meeting DA - 18.01.2022 KW - Ultrakurze Laserpulse KW - Materialbearbeitung KW - Röntgenstrahlung KW - Strahlenschutz PY - 2022 AN - OPUS4-54259 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Krüger, Jörg T1 - X-ray hazards and radiation protection aspects in ultrashort laser processing N2 - Ultrashort pulse laser micromachining at repetition rates of several hundreds of kHz allows a cost-effective high precision manufacturing, which makes this method attractive for many industrial applications. Upon exceeding a critical laser intensity, hard X-ray radiation is generated as a side effect. Even if the emitted X-ray dose per laser pulse is low, for currently available high-repetition-rate laser systems the accumulated X-ray dose becomes significant and radiation safety must be considered. Influences of the processing parameters are discussed and radiation protection aspects will be outlined T2 - AKL’22 – International Laser Technology Congress CY - Aachen, Germany DA - 04.05.2022 KW - Ultrashort pulse laser processing KW - X-ray emission KW - Radiation protection PY - 2022 AN - OPUS4-54805 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Krüger, Jörg T1 - Unwanted X-ray emission in ultrashort pulse laser processing: From metallic to biological materials N2 - Ultrashort laser pulses have become established in many industrial processes. Additionally, they are also an integral part of medical applications especially in ophthalmology and to some extent in dentistry. The availability of highly repetitive powerful laser sources and advanced laser beam control systems have favored these developments. However, the laser processing may be accompanied by the generation of unwanted X-rays. Small doses per laser pulse can accumulate to significant dose levels at high laser pulse repetition rates. Moreover, burst mode processing increases the X-ray dose rates compared to single pulse use and results in X-ray photon energies up to 40 keV for tungsten targets. For laser treatment of human teeth, clearly noticeable X-ray skin dose rates can be found. The paper summarizes the current state of the art in the field of undesired generation of X-ray radiation during ultrashort pulse laser processing in air. T2 - Lasers in Manufacturing 2023 (LiM 2023) CY - Munich, Germany DA - 26.06.2023 KW - Ultrashort laser pulses KW - Laser-induced X-ray emission KW - Secondary hazard PY - 2023 AN - OPUS4-57816 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Krüger, Jörg T1 - Strahlenexpositionen bei der Anwendung von Ultrakurzpulslasern in der Medizin N2 - Die Erzeugung unerwünschter Röntgenstrahlung bei der Ultrakurzpulslaser-Bearbeitung von Cornea und Zahnmaterial wurde untersucht. Laser-induzierte Dosisleistungen über dem natürlichen Hintergrund wurden gemessen. Mögliche Strahlenexpositionen in realen Anwendungen am Menschen wurden im Online-Vortrag diskutiert. Im Rahmen des vom BfS geförderten Projektes haben die Hochschule Mittweida und die BAM gemeinsam Untersuchungen durchgeführt. T2 - Kolloquium des Bundesamtes für Strahlenschutz (BfS) CY - Online meeting DA - 18.04.2023 KW - Ultrakurzpulslaser KW - Laser-induzierte Röntgenstrahlung KW - Medizinische Anwendung KW - Auge KW - Zahn PY - 2023 AN - OPUS4-57362 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Krüger, Jörg T1 - Gefährdung durch Röntgenemission bei der UKP-Laser-Materialbearbeitung N2 - Der Vortrag gibt einen Überblick zu ultrakurzen Laserpulsen, der Ultrakurzpulslaser-Materialbearbeitung und der dabei ggf. auftretenden unerwünschten Röntgenstrahlung. Es wird die Laserbearbeitung von technischen und biologischen Materialien diskutiert. Schutzmöglichkeiten gegenüber der Röntgenstrahlung werden erörtert. T2 - Sonthofer Strahlenschutztage 2024 CY - Sonthofen, Germany DA - 11.03.2024 KW - Ultrakurzpulslaser KW - Laser-induzierte Röntgenstrahlung KW - Materialbearbeitung KW - Technische Materialien KW - Biologische Anwendungen PY - 2024 AN - OPUS4-59667 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Krüger, Jörg T1 - Röntgenstrahlungsexposition bei der Anwendung von Ultrakurzpulslasern in der Medizin N2 - Die Laserbearbeitung von Materialien mit ultrakurzen Laserpulsen kann zu einer sekundären Emission gefährlicher Röntgenstrahlen führen. Dieser Effekt wurde bisher bei der Bearbeitung von technischen Materialien wie Metallen beobachtet. Die Röntgenemission bei der abtragenden Bearbeitung von biologischen Geweben ist noch weitgehend unerforscht. Der Vortrag präsentiert erste Untersuchungen und Ergebnisse des radiologischen Gefährdungspotentials bei der medizinischen Anwendung von Ultrakurzpulslasern am Menschen. T2 - Bayerische Laserschutztage 2024 CY - Nuremberg, Germany DA - 17.01.2024 KW - Ultrakurzpulslaser KW - Laser-induzierte Röntgenstrahlung KW - Medizinische Anwendung KW - Auge KW - Zahn PY - 2024 AN - OPUS4-59399 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krüger, Jörg A1 - Bonse, Jörn T1 - Editorial: Special Issue “Advanced Pulse Laser Machining Technology" N2 - “Advanced Pulse Laser Machining Technology” is a rapidly growing field that can be tailored to special industrial and scientific applications. This is significantly driven by the availability of high-repetition-rate laser sources and novel beam delivery concepts. KW - Editorial KW - Pulse Laser KW - Laser Machining KW - Ultrashort laser pulses PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-568410 DO - https://doi.org/10.3390/ma16020819 SN - 1996-1944 VL - 16 IS - 2 SP - 1 EP - 4 PB - MDPI CY - Basel AN - OPUS4-56841 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kraft, Sebastian A1 - Schille, J. A1 - Bonse, Jörn A1 - Löschner, U. A1 - Krüger, Jörg T1 - X‑ray emission during the ablative processing of biological materials by ultrashort laser pulses N2 - The ablative laser processing with ultrashort pulsed laser beams may cause secondary emission of hazardous X-rays. While the effect has recently been proven to be considered in working safety regulations when processing technical materials, such as metals, the X-ray emission rates during the ablative processing of biological tissue materials are widely unexplored yet. Therefore, biological materials like water, isotonic saline solution, pig eyes, and human teeth were ablated with ultrashort laser pulses of 1030 nm wavelength, 600 fs pulse duration and 5 kHz pulse repetition rate, aiming to mimic typical surgery situations. Simultaneously, in-situ X-ray dose rate measurements were performed at a short distance from the plasma to display potential X-ray emission. For all four studied biological materials, our measurements prove the secondary emission of laser-induced X-rays. KW - Ultrashort pulsed laser KW - Laser-induced X-ray emission KW - Ophthalmology KW - Dentistry KW - Secondary hazard PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-569960 DO - https://doi.org/10.1007/s00339-023-06440-4 SN - 0947-8396 VL - 129 IS - 3 SP - 1 EP - 8 PB - Springer AN - OPUS4-56996 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Böttcher, Katrin A1 - Schmitt Rahner, M. A1 - Stolzenberg, U. A1 - Kraft, Sebastian A1 - Bonse, Jörn A1 - Feist, C. A1 - Albrecht, D. A1 - Pullner, B. A1 - Krüger, Jörg T1 - Worst-case X-ray photon energies in ultrashort pulse laser processing N2 - Ultrashort pulse laser processing can result in the secondary generation of unwanted X-rays if a critical laser irradiance of about 10^13 W/cm^2 is exceeded. Spectral X-ray emissions were investigated during the processing of tungsten and steel using three complementary spectrometers (based on CdTe and silicon drift detectors) simultaneously for the identification of a worst-case spectral scenario. Therefore, maximum X-ray photon energies were determined, and corresponding dose equivalent rates were calculated. An ultrashort pulse laser workstation with a pulse duration of 274 fs, a center wavelength of 1030 nm, pulse repetition rates between 50 kHz and 200 kHz, and a Gaussian laser beam focused to a spot diameter of 33 µm was employed in a single pulse and burst laser operation mode. Different combinations of laser pulse energy and repetition rate were utilized, keeping the average laser power constant close to the maximum power of 20 W. Peak irradiances ranging from 7.3 × 10^13 W/cm^2 up to 3.0 × 10^14 W/cm^2 were used. The X-ray dose equivalent rate increases for lower repetition rates and higher pulse energy if a constant average power is used. Laser processing with burst mode significantly increases the dose rates and the X-ray photon energies. A maximum X-ray photon energy of about 40 keV was observed for burst mode processing of tungsten with a repetition rate of 50 kHz and a peak irradiance of 3 × 10^14 W/cm^2. KW - Ultrashort pulsed laser KW - X-ray emission KW - X-ray spectrum KW - X-ray energies KW - Radiation protection PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-566176 DO - https://doi.org/10.3390/ma15248996 VL - 15 IS - 24 SP - 1 EP - 17 PB - MDPI AN - OPUS4-56617 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -