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Prof. Cowan – HZDR

Institute of Radiation Physics

Helmholtz-Zentrum Dresden-Rossendorf

The Helmholtz-Zentrum Dresden-Rossendorf is a member of the Helmholtz Association of German Research Centres pursuing new insights that will allow us to maintain and improve all of our lives. That’s why the HZDR conducts research in the sectors health, energy, and matter in Dresden and at three other locations. Three of our five large-scale facilities are also available to external guests from around the world to help answer the decisive questions of our society.

Institute of Radiation Physics

Basic and Applied Research

The Institute of Radiation Physics is headed by Prof. Thomas E. Cowan and Prof. Ulrich Schramm. The institute is engaged in the basic research in accelerator-, nucleons, hadron and laser physics as well as the development of new types of radiation and particle beams, and new detections and measurement techniques for application to cancer research, nuclear safety and advanced materials.

Scientific Profile

For its research the Institute makes use of the coupling of electromagnetic radiation to animate and inanimate matter. In this work the Rossendorf Radiation Source ELBE plays a central role. Photons used in the various fields of activity cover a wide wavelength range from infrared light (many micrometer) down to subnuclear dimensions (less than femtometer). Electromagnetic radiation is used for the extraction of structural information on complex biological systems and their dynamics, and by exciting atomic nuclei and their hadronic constituents the subatomic structure of matter is investigated and new insight is gained into the cosmic “element cooking”. In health research radiation is also used to study cell damage and to develop new radio-oncologic therapies.

With respect to the investigations in such diverse fields, considerable synergy effects occur: e. g. the numerical simulation of the interaction of radiation with subatomic matter resembles very much the one with bio-molecules and cells, and the transport of radiation within these rather different media has surprising similarities.

Scientific Projects using GPUs

Currently, two projects at the Institute of Radiation Physics are looking into GPU-acceleration to speed up their scientific work.

Simulating laser-plasma interaction on the atomic level

Laser-driven electron acceleration

Visualization of electric fields in laser-driven electron acceleration: When an ultra-short, highly intense laser pulse travels through a gas, it can rip apart the gas atoms, leaving behind a plasma of electrons and positively charged ions. The laser can push electrons away from the ions. This in turn creates local charge imbalances that cause strong electric fields to emerge. These fields are strong enough to accelerate electrons from the plasma. In the picture, the strongest fields, depicted in blue, come from the laser pulse (left) itself and from accelerated electrons trailing the pulse (center).

The first project using GPUs, PIConGPU, is headed by Dr. Michael Bussmann. It aims at simulating the interaction of high-power pulsed lasers with matter. Extreme electric and magnetic fields are created when a high-intensity laser pulse rips matter apart into its constituents, electrons and atomic nuclei. These fields can in turn be used to accelerate these particles, creating beams of electrons and ions with characteristics unmatched by any beam produced by conventional accelerator techniques. Laser-driven particle accelerators are usually more compact than the accelerators commonly used.

Within the Laser Particle Acceleration group headed by Prof. Ulrich Schramm experiments are conducted on laser-driven ion acceleration and laser-driven electron acceleration and the use of these beams for applications such as radiotherapy of cancer tumors and the creation of brilliant X-ray light sources. These experiments are accompanied by highly parallel simulations. To speed up these simulations, the particle-in-cell code PIConGPU has been developed within the Computational Radiation Physics group. With this code running on large clusters of GPUs, it has become possible to receive simulation results within hours rather than weeks.

Online-dosimetry for tumor-conform radiotherapy

When a patient is irradiated, gamma ray photons emitted from the irradiated tissue can be used to determine the dose deposited into the tissue. As a first test of this reconstruction method, the image of a point source sending out gamma rays was assembled from 2000 single-photon events. This technique requires a lot of computational power and could be accelerated using GPUs.

 

 

 

The second project is headed by Dr. Fine Fiedler. The division of Radiation physics is interested in determining the effect of ionizing radiation on living cells (headed by Dr. Jörg Pawelke) and works on precision radiotherapy for ion beams. The precise knowledge of radiation induced cell damage is essential for understanding the radiobiological effectiveness of radiotherapy of cancerous tumors. With this knowledge at hand, it is possible to quantify how much dose has been deposited into the tumor and how this dose has damaged the cancerous cells.

Using ion beams for tumor irradiation requires a very high precision in dose delivery. This information should at best be already available during the irradiation of the patient, allowing for optimum treatment. During irradiation, the location of the tumor and the surrounding healthy tissue can change due to the patient moving, breathing, etc. Thus, online dose control for tumor-conform radiotherapy is mandatory to damage cancerous cells effectively while keeping the dose delivered to the surrounding healthy tissue to a minimum. Online dose control requires fast reconstruction of a 3D image of the dose deposition from the tracks of many single photons emitted from the irradiated region. Acceleration of these computations using GPUs can possibly allow for online reconstruction during the treatment. All projects are in close collaboration with the Medical Physics group at the National Center for Radiation Research in Oncology – OncoRay – headed by Prof. Dr. Wolfgang Enghardt.

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