Mr. Franz S. Englbrecht Profile

Franz S. Englbrecht

at Ludwig-Maximilians-Univ München

SPIE Involvement:

Author

Publications (2)

Proceedings Article | 18 April 2021 Presentation

On the feasibility of quantitative laser-driven proton radiography

Matthias Würl, Chiara Gianoli, Franz Englbrecht, Katia Parodi

Proceedings Volume 11790, 1179007 (2021) https://doi.org/10.1117/12.2596501

Read Abstract +

Laser-accelerated proton bunches with kinetic energies of several tens of MeV can be produced with 100-TW to PW laser pulses. The increasing availability of high-power laser systems operating at repetition rates in the order of Hz, along with the unique features of laser-accelerated proton bunches and the meanwhile repeatably achievable kinetic energies are arousing interest in the field of radiological and biomedical applications. Accurate positioning and characterization of the biological specimen is crucial for such applications, raising the need for on-site imaging. Proton radiography could be promising, as it can make use of the intrinsic energy spread of laser-accelerated proton bunches [1]. The proton energy distribution obtained in the target-normal-sheath acceleration (TNSA) regime results in a monotonically decreasing depth-dose distribution in matter, resembling the attenuation of X-rays. With knowledge of the energy distribution of individual bunches and a pixelated semiconductor detector downstream of the imaged object, quantitative information on the object in terms of water-equivalent thickness (WET) can be obtained online. We present a detailed Monte Carlo (MC) study assessing the feasibility of laser-driven proton radiography [2] for object sizes relevant for small-animal experiments. The simulation setup (fig. 1, left) consists of a thin and coarsely pixelated transmission time-of-flight spectrometer prior to the object and a model of a CMOS sensor for imaging. Two scenarios with TNSA-like proton bunches of energies up to 20 MeV and up to 100 MeV were studied. Phantoms of different geometry and material with a thickness of 0.3 mm to 23 mm were placed at distances from 1 mm to 20 mm from the detector. The bunch energy distribution was determined from the time-dependent energy deposition in the spectrometer. Together with a MC generated look-up table, it was used to create a bunch-specific conversion from energy deposition per pixel of the imaging detector to WET. Requirements on the spectrometer performance were examined by variation of its temporal and spatial resolution. Exemplary, the reconstructed WET distribution of a 2 cm thick phantom is shown in fig. 1 (right). With an imaging dose of a few cGy, corresponding to a proton fluence in the detector plane of around 106 cm-2, reconstructed WET values are in good agreement with ground truth (differences < 1.5%). Due to Coulomb scattering in the object, spatial resolution strongly depends on the distance between object and detector. For a gap of 5 mm, which is realistic for an experimental setup, a spatial resolution of 2.5 lp/mm and 1.9 lp/mm was found for the low and the high-energy scenario, respectively. A temporal resolution of the spectrometer of 0.2 ns or better is required for a drift space of 1 m and 3 m for the two scenarios, respectively. We have shown the feasibility and the potential of a setup for online and quantitative laser-driven proton radiography. The relatively high imaging dose may be reduced by tailoring the initial proton energy distribution. Experimental radiographies are foreseen at the Centre for Advanced Laser Applications (CALA), in Garching near Munich, Germany. [1] J. Schreiber, et al., “Hands-on” laser-driven ion acceleration: A primer for laser-driven source development and potential applications, Rev Sci Instrum, 87, (2016), 071101. [2] M. Würl, et al., A Monte Carlo feasibility study on quantitative laser-driven proton radiography, Z Med Phys, In Press, (2020).

Proceedings Article | 18 April 2021 Presentation

Multimodal emission from laser-plasma accelerators and possible applications in imaging

Tobias Ostermayr, Christian Kreuzer, Franz Englbrecht, Johannes Gebhard, Jens Hartmann, Axel Huebl, Daniel Haffa, Peter Hilz, Katia Parodi, Björn Hegelich, Hai-En Tsai, Anthony Gonsalves, Kei Nakamura, Mario Balcazar, John Nees, Yong Ma, Elizabeth Grace, Raspberry Simpson, Paul King, Isabella Pagano, Félicie Albert, Alexander G. Thomas, Carolyn Kuranz, Csaba Toth, Carl Schroeder, Cameron G. Geddes, Joerg Schreiber, Eric Esarey

Proceedings Volume 11779, 117790P (2021) https://doi.org/10.1117/12.2592671

KEYWORDS: X-rays, X-ray imaging, Laser applications, Electrons, Laser development, Ions, X-ray sources, X-ray lasers, Tungsten, Solids

Read Abstract +

Radiographic imaging is an omnipresent tool in basic research and applications in industry, material science and medical diagnostics. Often, the information contained in more than one modality can be valuable, but difficult to access simultaneously. This talk reviews developments in laser-plasma-accelerators for protons, electrons and x-rays from solid and gas targets for multimodal imaging. Laser-driven ion acceleration and x-ray generation have been investigated using tungsten micro-needle-targets at the Texas Petawatt laser [1]. The experiments and supporting numerical simulations reveal peaked proton spectra around 10 MeV with significant particle count and a strong keV level x-ray source. The source size for both has been measured to be in the few-µm range. Both sources were eventually applied to simultaneous radiographic imaging of biological and technological samples. In recent experiments at BELLA Center’s high repetition rate 100 TW dual-arm laser, steps were taken towards bi-modal x-ray and electron imaging of dynamic events such as hydrodynamic shocks, in which often both density and electro-magnetic fields are important quantities to measure. Here, a shock was driven by a 1 Joule, 200 ps laser focused in a 30 µm wide water jet. A laser wakefield accelerator was driven by a second 2 Joule, 40 fs laser in a gas-jet target, providing both 150 MeV electrons and broadband betatron x-rays up to ˜10 keV for projection imaging. This research aims to leverage unique properties readily available in laser plasma accelerators for applications. Specifically, the emission of pulsed, bright, multimodal bursts of radiation can open new ways in biological imaging (e.g., with ns-synchronized ions and x-rays) and in high-resolution diagnostics for high-energy density science (e.g., with fs-synchronized electrons and x-rays). [1] T. M. Ostermayr et al., “Laser-driven x-ray and proton micro-source and application to simultaneous single-shot bi-modal radiographic imaging,” Nat. Commun., vol. 11, no. 1, pp. 1–9, Dec. 2020. This work was supported by the DFG via the Cluster of Excellence Munich-Centre for Advanced Photonics (MAP) and Transregio SFB TR18. This work has been carried out within the framework of the EUROfusion Consortium and has received funding, through the ToIFE, from the European Union’s Horizon 2020 research and innovation program under grant agreement number 633053. The authors acknowledge funding by the Air Force Office of Scientific Research (AFOSR)(FA9550-14-1-0045, FA9550-17-1-0264). Work supported by DOE FES under grant DE-SC0020237. Work supported by US DOE NNSA DNN R&D, by Sc. HEP, by the Exascale Computing Project and by FES LaserNetUS under DOE Contract DE-AC02-05CH11231.

View contact details

UPDATE YOUR PROFILE

Is this your profile? Update it now.

Sign into your SPIE.org account

Don’t have a profile and want one?

Create an account on SPIE.org

Keywords/Phrases

Search In:

Publication Years