Apr 3, 2006
At the Japan Atomic Energy Agency (President Yuichi Tonozuka, here after referred as to JAEA), research on the laser driven proton acceleration method is underway with the aim of providing a compact and cheap device for proton therapy regarded as a revolutionary treatment being less burdensome for cancer patients. This time an important condition for optimum acceleration has been discovered. This is achieved by optimizing the thickness of the target to be irradiated in accordance with the laser intensity. It has been found that the laser intensity required for proton acceleration could be reduced as compared to that envisioned so far. Development for small proton cancer therapy devices has significantly advanced due to the present result. This research was done by Timur Esirkepov, Toshiki Tajima, and Mitsuru Yamagiwa of the JAEA Quantum Beam Science Directorate, being partially supported by the Core Research for Evolutional Science and Technology (CREST) of the Japan Science and Technology Agency (JST).
The method of laser acceleration by using intense laser light is very attractive, since the acceleration performance is markedly higher than standard large accelerators and the device size could be much more compact (1/10∼1/100) than the present facilities in existence. Currently proton acceleration experiments using high power laser close up to petawatt levels are going on vigorously all over the world. However, since laser acceleration is accomplished by a combination of cutting-edge laser technologies, highly-advanced technical know-how to adjust the various conditions is needed. In order to find the delicate conditions for the laser and the optimal target design of micron order thickness, experimental research should be complimented by simulation. Therefore, in this work a simulation program has been developed to scrupulously survey the optimum laser and target conditions by using super computers at JAEA.
The maximum energy of protons generated from a target irradiated by laser light has been predicted and the dependence on the laser and target parameters has been studied. It has been found that the proton energy in the range of 200 MeV required for deep cancer therapy may possibly be achievable with the laser intensity lower than that anticipated so far if the conditions of the laser pulse and the thin film target from which protons originate are appropriately selected.
The present result, indicating that the laser intensity triggering the proton energy generation can be reduced, leads us closer to realization of a laser driven cancer therapy device. Research and development seeking more rational experimental parameters and laser systems for the realization of a small laser driven cancer therapy device will be undertaken at JAEA in coordination with the medical community.
This result was published in the Physical Review Letters: PHYSICAL REVIEW LETTERS 96, 105001 (2006).
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