Temporal and spectral characteristics of soft x radiation from laser-irradiated cylindrical cavities

Weber, Rudolf; Cunningham, P. F.; Balmer, J. E.

doi:10.1063/1.100190

Cited by 15 publications

(4 citation statements)

References 10 publications

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“…As seen in [11,[13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] the plasma properties k B T h , Z i , and n h are complicated functions of space and time. However, for this work it is assumed that the predominant part of the Bremsstrahlung emission in the part of the spectrum of interest is produced by the hot electrons, during the laser pulse, and at a constant hot-electron temperature in…”

Section: Thermal Bremsstrahlung Emission From Laser-produced Plasmamentioning

confidence: 99%

“…(2)-(6) and (2) yield a decreasing dose rate from Eq. (14), if the irradiance is increased by decreasing the pulse duration and keeping all other parameters constant.…”

Section: Influence Of the Pulse Duration At Constant Average Powermentioning

confidence: 99%

“…Such high laser irradiances lead to hot-electron temperatures in the plasma of up to several keV [11] that result in Bremsstrahlung, recombination and line emission in the keV X-ray region. X-ray emission from laser-produced plasma is well known and has been investigated since the early 1980ies [12][13][14][15][16][17][18][19][20][21][22][23]. X-rays emitted from laser-induced plasma were used, in particular, in indirect driven fusion and X-ray laser research, later also for X-ray lithography and X-ray spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

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Expected X-ray dose rates resulting from industrial ultrafast laser applications

et al. 2019

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An analytical model is presented, which allows estimating the expected dose rates resulting from X-ray emission from ultrashort-pulse laser-produced plasma under industrial conditions. The model is based on the calculation of the Bremsstrahlung spectrum in the X-ray region between about 5 keV and 50 keV, which is created by the hot electrons in the plasma. The model was calibrated with both spectral and dose rate measurements. The scaling of the hot-electron temperature and the fraction of hot electrons in the plasma served as calibration values. The agreement between experiments and model for the investigated irradiances in range from 10 12 to 10 15 W/cm 2 is excellent. The expected Ḣ (0.07) and Ḣ (10) dose rates at a distance of 20 cm from the process in air were calculated for upcoming lasers with 1 kW of average power. Although the dose rates close to the plasma significantly exceed the allowed dose of 50 mSv per year for an irradiance exceeding about 2·10 15 W/cm 2 , the calculations show that shielding with a 2-mm sheet of iron already at a distance of 20 cm attenuates the radiation to a safe value below 0.4 µSv/h.

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Section: Thermal Bremsstrahlung Emission From Laser-produced Plasmamentioning

confidence: 99%

“…(2)-(6) and (2) yield a decreasing dose rate from Eq. (14), if the irradiance is increased by decreasing the pulse duration and keeping all other parameters constant.…”

Section: Influence Of the Pulse Duration At Constant Average Powermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Expected X-ray dose rates resulting from industrial ultrafast laser applications

et al. 2019

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“…The interaction of incident ultrashort laser pulses with the ablated material was well described in previous reports [ 3 , 5 , 6 ]. Most of the experimental studies on the emission of ionizing radiation from laser-produced plasmas were already carried out in the 1980s under high vacuum conditions [ 9 , 10 , 11 , 12 , 13 , 14 ], resulting in only a few publications considering industrial conditions [ 7 , 15 , 16 , 17 , 18 ]. With the increase in available power of recent ultrafast lasers, the topic is gaining interest in the area of industrial laser material processing, which has lead to the latest investigations about the influence of high pulse repetition rates [ 19 ], different materials [ 20 ] and the pulse duration [ 21 ] on the X-ray emission.…”

Section: Introductionmentioning

confidence: 99%

Self-Shielding of X-ray Emission from Ultrafast Laser Processing Due to Geometrical Changes of the Interaction Zone

Holland,

Hagenlocher,

Weber

et al. 2024

Materials

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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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X‐Ray Protection in an Industrial Production Environment

Freitag¹,

Giedl‐Wagner²

2020

PhotonicsViews

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With the classification of ultrashort‐pulse laser processing systems as “systems for the generation of ionizing radiation” in the German Strahlenschutzgesetz (Radiation Protection Act), their operation is usually no longer possible without a license and without notification of the authorities. This article deals with the implementation of the legal requirements resulting from this classification in an industrial production environment.

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Temporal and spectral characteristics of soft x radiation from laser-irradiated cylindrical cavities

Cited by 15 publications

References 10 publications

Expected X-ray dose rates resulting from industrial ultrafast laser applications

Expected X-ray dose rates resulting from industrial ultrafast laser applications

Self-Shielding of X-ray Emission from Ultrafast Laser Processing Due to Geometrical Changes of the Interaction Zone

X‐Ray Protection in an Industrial Production Environment

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