Magnetic field and ion-optical simulations for the optimization of the Super-FRS

The growing demand in the field of discovering and investigating exotic nuclei by means of fragment separators yields challenging restrictions on future facilities. The main task of a fragment separator is the in-flight separation of many different species of nuclides, produced with an ion beam on a target. To achieve the best resolution and capture of rare nuclei, maximal beam illumination of the apertures of the ion-optical elements is required. Many fragment separators have a wide operation range of the magnetic rigidity Brho. Moreover, frequent changes of Brho are required during experiments. Often magnets are operated in the saturation region of the iron yokes, leading to local changes of the magnetic field (B-field) distributions and the corresponding particle trajectories. In such cases it is important to have a fast ion-optical model with good predictability, which considers the real field distributions and the saturation. This thesis describes the development of a general approach to provide a fast and accurate ion-optical model (Taylor transfer map) of large aperture magnets starting from simulated or measured 3D B-field distributions. To produce highly accurate transfer map, a B-field has to be represented by 3D polynomials. It is crucial that the whole transversal aperture is described by a single polynomial, whereas many polynomials might be used in the longitudinal direction. High non-uniformity of the B-field makes this problem more complicated, especially for the regions near the pole shoe ends. The problem was solved by means of a combination of the Surface Integration Helmholtz Method (SIHM) and the Least Squares (LS) method. The approach was extended further for obtaining the B-field polynomial representation dependent on both: the coordinates and the excitation current. This representation allows to produce Brho dependent transfer maps, which can be useful for the optimization of the separator settings for different experiments. The method was tested using the analytical field model, based on a configuration of thin wires and a Biot-Savart law, resulting in a high stability against the errors in the input B-field. The rigidity dependent transfer maps were generated for the normal conducting dipole of the Super-FRS preseparator. The ion-optical study of the preseparator in the separator as well as in the spectrometer modes were conducted

Depth dose measurements in water for 11C and 10C beams with therapy relevant energies

Owing to the favorable depth-dose distribution and the radiobiological properties of heavy ion radiation, ion beam therapy shows an improved success/toxicity ratio compared to conventional radiotherapy. The sharp dose gradients and very high doses in the Bragg peak region, which represent the larger physical advantage of ion beam therapy, make it also extremely sensitive to range uncertainties. The use of beta(+) - radioactive ion beams would be ideal for simultaneous treatment and accurate online range monitoring through PET imaging. Since all the unfragmented primary ions are potentially contributing to the PET signal, these beams offer an improved image quality while preserving the physical and radiobiological advantages of the stable counterparts. The challenging production of radioactive ion beams and the difficulties in reaching high intensities, have discouraged their clinical application. In this context, the project Biomedical Applications of Radioactive ion Beams (BARB) started at GSI (Helmholtzzentrum fur Schwerionenforschung GmbH) with the main goal to assess the technical feasibility and investigate possible advantages of radioactive ion beams on the pre-clinical level. During the first experimental campaign C-11 and C-10 beams were produced and isotopically separated with the FRagment Separator (FRS) at GSI. The beta(+)-radioactive ion beams were produced with a beam purity of 99% for all the beam investigated (except one case where it was 94%) and intensities potentially sufficient to treat a small animal tumors within few minutes of irradiation time, similar to 10(6) particle per spill for the C-10 and similar to 10(7) particle per spill for the C-11 beam, respectively. The impact of different ion optical parameters on the depth dose distribution was studied with a precision water column system. In this work, the measured depth dose distributions are presented together with results from Monte Carlo simulations using the FLUKA software

Radioactive Beams for Image-Guided Particle Therapy : The BARB Experiment at GSI

Several techniques are under development for image-guidance in particle therapy. Positron (β+) emission tomography (PET) is in use since many years, because accelerated ions generate positron-emitting isotopes by nuclear fragmentation in the human body. In heavy ion therapy, a major part of the PET signals is produced by β+-emitters generated via projectile fragmentation. A much higher intensity for the PET signal can be obtained using β+-radioactive beams directly for treatment. This idea has always been hampered by the low intensity of the secondary beams, produced by fragmentation of the primary, stable beams. With the intensity upgrade of the SIS-18 synchrotron and the isotopic separation with the fragment separator FRS in the FAIR-phase-0 in Darmstadt, it is now possible to reach radioactive ion beams with sufficient intensity to treat a tumor in small animals. This was the motivation of the BARB (Biomedical Applications of Radioactive ion Beams) experiment that is ongoing at GSI in Darmstadt. This paper will present the plans and instruments developed by the BARB collaboration for testing the use of radioactive beams in cancer therapy.peerReviewe

A new Time-of-flight detector for the R 3 B setup

© 2022, The Author(s).We present the design, prototype developments and test results of the new time-of-flight detector (ToFD) which is part of the R3B experimental setup at GSI and FAIR, Darmstadt, Germany. The ToFD detector is able to detect heavy-ion residues of all charges at relativistic energies with a relative energy precision σΔE/ ΔE of up to 1% and a time precision of up to 14 ps (sigma). Together with an elaborate particle-tracking system, the full identification of relativistic ions from hydrogen up to uranium in mass and nuclear charge is possible.11Nsciescopu