Dosimetry and Radiobiology for Laser Induced Proton Beams

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Laser-generated ion beams have the potential to be used for future cancer therapies as they may provide compact, less expensive alternative sources to those currently used for proton and carbon-ion therapies. Ion-beam therapies have considerable advantages for treating tumours relative to high energy X-rays due to the defined deposition of energy via a Bragg Peak. This PhD project forms part of a large, EPSRC-funded collaborative effort aimed to develop laser-generated ion beams with properties suitable for future use in therapy, and test the consequences of exposure to these beams in normal and tumour cells. Laser produced ion beams deliver radiation dose at extremely high dose-rates in comparison to conventional sources and, in addition to exploring the radiobiology of this regime, a key goal of the PhD research will be to define effective approaches for proton and carbon dosimetry under these extreme conditions. Motivated by the potential for future clinical applications, current experimental activities employing laser-driven sources are devoted to developing a methodology for carrying out meaningful biological assays in a laser-plasma environment , where doses of the order of several Gys can be delivered in a single irradiation. The development of appropriate approaches to dosimetry is a key challenge to be faced in the course of this research. Since the stability and reproducibility of laser-driven ion sources is still not ideal, for a correct estimate of the irradiation conditions, the dose must be measured reliably in the course of every irradiation event, ideally in a non-invasive manner. We will therefore devote effort to the appropriate calibration of film dosimeters in the specific energy and dose range of relevance to the laser-driven ion sources. This will include the validation of customised radio chromic films, as well as the use of alanine pellets and CR39 particle track detectors. In addition to these approaches to relative dosimetry, the project will aim to test the effectiveness in a laser-plasma environment of tools for absolute dosimetry such as Faraday cups and ion calorimeters.