\item radio therapy is an important tool in cancer therapy
\item continuous development towards improved tolerability and increase of the therapeutic window
\item two promising developments in recent years:
\begin{itemize}
\item encouraging results with very short, high dose beams (FLASH RT)
\item recent further development of spatially fractionated RT towards Microbeam Radiation Therapy (MRT)
\end{itemize}
\item both show improved sparing of healthy tissue and reduction of secondary cancer also increasingly important due to increase in overall life expectancy
\item both are dependent on the use of particle accelerator facilities
\item very high requirements on stability and metrology of the used beams
\end{itemize}
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lead to operation parameters of the used accelerators that can not anymore be described by simple linear optics and beam dynamics. Instead, due to the development towards higher intensity combined with shorter pulse lengths and transverse modulations, the consideration of nonlinear and complex optics as well as beam dynamics influenced by collective effects becomes necessary.\\
Bridging this gap between accelerator science and medical physics from the accelerator side is an important step and will help in paving the way towards accurate predictability, diagnostic and metrology of advanced RT with particle accelerators.
\item improve predictability of RT beam properties on target by improving understanding of dynamic in short and/or spatially structured RT beams
\item study from accelerator point of view the beam dynamics effects relevant in the generation of such beams as well as the diagnostic to reliably deliver the requested conditions
\item provide simulations of the dynamic of RT beams start to end, from inside the accelerator through the air into the target by combining beam dynamics, beam-matter interaction and collective effects simulations
\item predicting the temporal and spacial shape of the individual RT pulse %not only at the exit of the accelerator but also at any diagnostic
at any point on the way up to the target inside the patient
The hope is that, by extending the calculation of these effects beyond the accelerator as a first step, it becomes possible to predict the resulting spatial distribution on target.
And as a second step, it might allow to consider effects of the beam transport already during the generation.
Ideally, this would allow the generation of a spacial distribution which preemptively compensates for the expected changes.
\item experience in longitudinal as well as transverse collective effects and instabilities influencing the electron bunch shape in all dimensions
\item in general, investigating phenomena occurring under extreme operation modes, e.g. high charge, small transverse bunch-size, short bunch-length, sub-structures, ...
\item on rings but focused on single bunch effects transferrable to linacs
\item simulations of non-linear optics and beam dynamics, collective effects
\item extensive experimental studies and measurements
\item used diagnostics: electron-beam based as well as synchrotron-radiation based\\ as well as improved and further-developed diagnostic methods
\item data analysis of complex and big datasets with, amongst others, Python and HPC (high performance computing)
\item based on existing simulation tools and models, e.g. transport/covariance matrices combined with average scattering angles based on existing beam-matter interaction descriptions
\item add collective effects, e.g. space charge, via impedances and/or particle tracking
\end{itemize}
Experimental in parallel:
\begin{itemize}
\item survey of required vs available diagnostics to measure 3D charge distribution at different positions in the linac, e.g. virtual diagnostic available
\item measurements of 3D charge distribution at accelerator exit based on starting distribution
\item experimental studies of the propagation of 3D charge distribution through air and/or water, including acquiring and set up of necessary diagnostic/detectors/targets
\item extend studies to X-ray(/THz?) at synchrotron light source (KARA)