"Laser-hybrid Accelerator for Radiobiological Applications (LhARA)"

​DOI: doi.org/10.3389/fphy.2020.567738 ; Preprint, ​arXiv:2006.00493
News items: ​STFC, ​Imperial

Abstract

The “Laser-hybrid Accelerator for Radiobiological Applications,” LhARA, is conceived as a novel, flexible facility dedicated to the study of radiobiology. The technologies demonstrated in LhARA, which have wide application, will be developed to allow particle-beam therapy to be delivered in a new regimen, combining a variety of ion species in a single treatment fraction and exploiting ultra-high dose rates. LhARA will be a hybrid accelerator system in which laser interactions drive the creation of a large flux of protons or light ions that are captured using a plasma (Gabor) lens and formed into a beam. The laser-driven source allows protons and ions to be captured at energies significantly above those that pertain in conventional facilities, thus evading the current space-charge limit on the instantaneous dose rate that can be delivered. The laser-hybrid approach, therefore, will allow the radiobiology that determines the response of tissue to ionizing radiation to be studied with protons and light ions using a wide variety of time structures, spectral distributions, and spatial configurations at instantaneous dose rates up to and significantly beyond the ultra-high dose-rate “FLASH” regime. It is proposed that LhARA be developed in two stages. In the first stage, a programme of in vitro radiobiology will be served with proton beams with energies between 10 and 15 MeV. In stage two, the beam will be accelerated using a fixed-field alternating-gradient accelerator (FFA). This will allow experiments to be carried out in vitro and in vivo with proton beam energies of up to 127 MeV. In addition, ion beams with energies up to 33.4 MeV per nucleon will be available for in vitro and in vivo experiments. This paper presents the conceptual design for LhARA and the R&D programme by which the LhARA consortium seeks to establish the facility.

Lay Summary

It is well-established that radiation therapy (RT) is an effective treatment for many types of cancer. Most treatments are delivered by machines that accelerate electrons which are then used to produce a beam of high-energy photons (X-rays) which are directed at a tumor to kill cancer cells. However, healthy tissue anywhere in the path of the photon beam is also irradiated and so can be damaged. Modern X-ray therapy is able to reduce this damage by using several beams at different angles. Recent years have seen the use of a new type of machine in which protons are accelerated to produce proton beams (rather than photon beams) which are directed at a tumor. These proton beams can be arranged to deposit almost all of their energy in a small volume within a tumor so they cause little damage to healthy tissue; a major advantage over photon beams. But proton machines are large and expensive, so there is a need for the development of proton machines that are smaller, cheaper and more flexible in how they can be used. The LhARA project is aimed at the development of such proton machines using a new approach based on high power lasers. Such new machines could also make it easier to deliver the dose in very short high-intensity pulses and as a group of micro-beams—exciting recent research has shown that this brings improved effectiveness in killing cancer cells while sparing healthy tissue. The technology to be proved in LhARA should enable a course of RT to be delivered in days rather than weeks. Scientifically, there is a need to understand better the basic processes by which radiation interacts with biological matter to kill cancer cells—the investigation of these processes involves physics as well as biology. Thus the most important aim of LhARA is to pursue this radiobiological research in new regimens and from this to develop better treatments. LhARA will also pursue technological research into laser-hybrid accelerators."

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