An online, energy-resolving beam profile detector for laser-driven proton beams.

In this paper, a scintillator-based online beam profile detector for the characterization of laser-driven proton beams is presented. Using a pixelated matrix with varying absorber thicknesses, the proton beam is spatially resolved in two dimensions and simultaneously energy-resolved. A thin plastic scintillator placed behind the absorber and read out by a CCD camera is used as the active detector material. The spatial detector resolution reaches down to ∼4 mm and the detector can resolve proton beam profiles for up to 9 proton threshold energies. With these detector design parameters, the spatial characteristics of the proton distribution and its cut-off energy can be analyzed online and on-shot under vacuum conditions. The paper discusses the detector design, its characterization and calibration at a conventional proton source, as well as the first detector application at a laser-driven proton source.

A scintillator-based online detector for the angularly resolved measurement of laser-accelerated proton spectra.

In recent years, a new generation of high repetition rate (~10 Hz), high power (~100 TW) laser systems has stimulated intense research on laser-driven sources for fast protons. Considering experimental instrumentation, this development requires online diagnostics for protons to be added to the established offline detection tools such as solid state track detectors or radiochromic films. In this article, we present the design and characterization of a scintillator-based online detector that gives access to the angularly resolved proton distribution along one spatial dimension and resolves 10 different proton energy ranges. Conceived as an online detector for key parameters in laser-proton acceleration, such as the maximum proton energy and the angular distribution, the detector features a spatial resolution of ~1.3 mm and a spectral resolution better than 1.5 MeV for a maximum proton energy above 12 MeV in the current design. Regarding its areas of application, we consider the detector a useful complement to radiochromic films and Thomson parabola spectrometers, capable to give immediate feedback on the experimental performance. The detector was characterized at an electrostatic Van de Graaff tandetron accelerator and tested in a laser-proton acceleration experiment, proving its suitability as a diagnostic device for laser-accelerated protons.

A dosimetric system for quantitative cell irradiation experiments with laser-accelerated protons.

An integrated dosimetry and cell irradiation system (IDOCIS) with laser-accelerated proton beams was developed, characterized, calibrated and successfully used for systematic in vitro experiments. Due to the broad exponentially shaped energy spectrum, the low-energy range of the protons (<20 MeV) and the high pulse dose, the absolute dosimetry for this beam quality is challenging. Therefore, a dedicated Faraday cup is used as an energy and dose rate independent absolute dosimeter that has been calibrated consistently with three independent methods. A transmission ionization chamber providing online relative dose information is cross-calibrated against the Faraday cup. Providing both online and absolute dose information, the IDOCIS allows for quantitative dosimetric and radiobiological studies at current low-energy laser-accelerated proton beams. Finally, first dosimetric characterizations of a laser-accelerated proton beam with the IDOCIS are presented.

The investigation of different cameras for in-beam PET imaging.

In situ and in vivo treatment plan verification and beam monitoring as well as dose control during heavy-ion tumour therapy can be performed in principle by measurements of range distributions of beta(+)-emitting nuclei by means of PET techniques. For this purpose the performance of different types of positron camera as well as the results of in-beam PET experiments using beams of beta(+)-active heavy ions (15O, 17F and 19Ne with energies of 300-500 A MeV) are presented. Following the deduced performance requirements a PET scanner that is designed for clinical use in experimental heavy-ion therapy at GSI Darmstadt has been built. This limited angle tomograph consists of two large-area detector heads based on position sensitive BGO detectors and is predicted to perform the measurement of the end point of a beta(+)-emitting ion beam for the verification of a treatment plan with a precision better than 1 mm. The maximum dose applied in the patient thereby is of the magnitude of 10 mGy.