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Holland J, Hagenlocher C, Weber R, Graf T. Self-Shielding of X-ray Emission from Ultrafast Laser Processing Due to Geometrical Changes of the Interaction Zone. MATERIALS (BASEL, SWITZERLAND) 2024; 17:1109. [PMID: 38473580 DOI: 10.3390/ma17051109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2024] [Revised: 02/23/2024] [Accepted: 02/26/2024] [Indexed: 03/14/2024]
Abstract
Materials processing with ultrashort laser pulses is one of the most important approaches when it comes to machining with very high accuracy. High pulse repetition rates and high average laser power can be used to attain high productivity. By tightly focusing the laser beam, the irradiances on the workpiece can exceed 1013 W/cm2, and thus cause usually unwanted X-ray emission. Pulsed laser processing of micro holes exhibits two typical features: a gradual increase in the irradiated surface within the hole and, with this, a decrease in the local irradiance. This and the shielding by the surrounding material diminishes the amount of ionizing radiation emitted from the process; therefore, both effects lead to a reduction in the potential X-ray exposure of an operator or any nearby person. The present study was performed to quantify this self-shielding of the X-ray emission from laser-drilled micro holes. Percussion drilling in standard air atmosphere was investigated using a laser with a wavelength of 800 nm a pulse duration of 1 ps, a repetition rate of 1 kHz, and with irradiances of up to 1.1·1014 W/cm. The X-ray emission was measured by means of a spectrometer. In addition to the experimental results, we present a model to predict the expected X-ray emission at different angles to the surface. These calculations are based on raytracing simulations to obtain the local irradiance, from which the local X-ray emission inside the holes can be calculated. It was found that the X-ray exposure measured in the surroundings strongly depends on the geometry of the hole and the measuring direction, as predicted by the theoretical model.
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Affiliation(s)
- Julian Holland
- Institut für Strahlwerkzeuge (IFSW), University of Stuttgart, Pfaffenwaldring 43, 70569 Stuttgart, Germany
| | - Christian Hagenlocher
- Institut für Strahlwerkzeuge (IFSW), University of Stuttgart, Pfaffenwaldring 43, 70569 Stuttgart, Germany
| | - Rudolf Weber
- Institut für Strahlwerkzeuge (IFSW), University of Stuttgart, Pfaffenwaldring 43, 70569 Stuttgart, Germany
| | - Thomas Graf
- Institut für Strahlwerkzeuge (IFSW), University of Stuttgart, Pfaffenwaldring 43, 70569 Stuttgart, Germany
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Mosel P, Düsing J, Johannesmeier S, Patzlaff-Günther M, Fröhlich S, Mapa J, Kalies S, Bahlmann J, Püster T, Vahlbruch J, Dittmar G, Merdji H, Fajardo M, Trabattoni A, Heisterkamp A, Morgner U, Kovacev M. X-ray generation by fs-laser processing of biological material. BIOMEDICAL OPTICS EXPRESS 2023; 14:5656-5669. [PMID: 38021146 PMCID: PMC10659813 DOI: 10.1364/boe.499170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 09/29/2023] [Accepted: 09/29/2023] [Indexed: 12/01/2023]
Abstract
The use of ultrashort pulse lasers in medical treatments is increasing and is already an essential tool, particularly in the treatment of eyes, bones and skin. One of the main advantages of laser treatment is that it is fast and minimally invasive. Due to the interaction of ultrashort laser pulses with matter, X-rays can be generated during the laser ablation process. This is important not only for the safety of the patient, but also for the practitioner to ensure that the legally permissible dose is not exceeded. Although our results do not raise safety concerns for existing clinical applications, they might impact future developments at higher peak powers. In order to provide guidance to laser users in the medical field, this paper examines the X-ray emission spectra and dose of several biological materials and describes their dependence on the laser pulse energy.
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Affiliation(s)
- P. Mosel
- Leibniz University Hannover, Welfengarten 1, Hannover 30167, Germany
| | - J. Düsing
- Laser Zentrum Hannover e.V., Hannover 30419, Germany
| | | | | | - S. Fröhlich
- Leibniz University Hannover, Welfengarten 1, Hannover 30167, Germany
| | - J. Mapa
- Leibniz University Hannover, Welfengarten 1, Hannover 30167, Germany
| | - S. Kalies
- Leibniz University Hannover, Welfengarten 1, Hannover 30167, Germany
- Lower Saxony Centre for Biomedical Engineering, Implant Research and Development (NIFE), 30625 Hannover, Germany
| | - J. Bahlmann
- Leibniz University Hannover, Welfengarten 1, Hannover 30167, Germany
- Lower Saxony Centre for Biomedical Engineering, Implant Research and Development (NIFE), 30625 Hannover, Germany
| | - T. Püster
- Laser Zentrum Hannover e.V., Hannover 30419, Germany
| | - J. Vahlbruch
- Institute of Radioecology and Radiation Protection, Leibniz University Hannover, Hannover 30419, Germany
| | - G. Dittmar
- Ingenieur-Büro Prof. Dr.-Ing. G. Dittmar, Aalen 73433, Germany
| | - H. Merdji
- LOA, ENSTA ParisTech, CNRS, Ecole Polytechnique, Université Paris-Saclay 828 Boulevard des Maréchaux, 91120, Palaiseau, France
| | - M. Fajardo
- GoLP, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal
| | - A. Trabattoni
- Leibniz University Hannover, Welfengarten 1, Hannover 30167, Germany
- Center for Free-Electron Laser Science CFEL, Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - A. Heisterkamp
- Leibniz University Hannover, Welfengarten 1, Hannover 30167, Germany
- Lower Saxony Centre for Biomedical Engineering, Implant Research and Development (NIFE), 30625 Hannover, Germany
| | - U. Morgner
- Leibniz University Hannover, Welfengarten 1, Hannover 30167, Germany
| | - M. Kovacev
- Leibniz University Hannover, Welfengarten 1, Hannover 30167, Germany
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Krüger J, Bonse J. Special Issue "Advanced Pulse Laser Machining Technology". MATERIALS (BASEL, SWITZERLAND) 2023; 16:819. [PMID: 36676556 PMCID: PMC9861651 DOI: 10.3390/ma16020819] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Accepted: 01/13/2023] [Indexed: 06/17/2023]
Abstract
"Advanced Pulse Laser Machining Technology" is a rapidly growing field that can be tailored to special industrial and scientific applications [...].
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Böttcher K, Schmitt Rahner M, Stolzenberg U, Kraft S, Bonse J, Feist C, Albrecht D, Pullner B, Krüger J. Worst-Case X-ray Photon Energies in Ultrashort Pulse Laser Processing. MATERIALS (BASEL, SWITZERLAND) 2022; 15:8996. [PMID: 36556801 PMCID: PMC9783067 DOI: 10.3390/ma15248996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Revised: 12/12/2022] [Accepted: 12/14/2022] [Indexed: 06/17/2023]
Abstract
Ultrashort pulse laser processing can result in the secondary generation of unwanted X-rays if a critical laser irradiance of about 1013 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 I0 ranging from 7.3 × 1013 W cm-2 up to 3.0 × 1014 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 × 1014 W cm-2.
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Affiliation(s)
- Katrin Böttcher
- Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany
| | - Mayka Schmitt Rahner
- Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany
| | - Ulf Stolzenberg
- Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany
| | - Sebastian Kraft
- Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany
| | - Jörn Bonse
- Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany
| | - Carsten Feist
- Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany
| | - Daniel Albrecht
- Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany
| | - Björn Pullner
- Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany
| | - Jörg Krüger
- Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany
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