–Particle Interactions in Nuclear Emulsion for Hadron Therapy and shielding Elaboration

Abstract

A and 3.7A GeV -Particles from Dubna Synchrophasetron are used to understand and address some effects in hadron therapy and shielding programming. The NIKFI-BR2 nuclear emulsion is the present target nuclei, like-some human and shield materials. The interaction mean free path with HCNO nuclei is determined. The inelastic interaction cross section is approximated by a power law, which is independent on the energy and expressed in terms of the target mass number. The different characteristics of the present projectile and target fragmentations are investigated experimentally in comparison with the SRIM simulations At low energy the physics can be accounted for fairly well by one single source. The de-excitation can be understood in terms of particle emission from a liquid drop of nuclear matter. At high energy, multiple sources are needed. The de-excitation is here understood in terms of particle emission from an expanding gas of nuclear matter in thermodynamical equilibrium. At excitation energies comparable with the total binding energy, ~ 5A to 8A MeV, the very existence of a long-lived compound nucleus becomes unlikely. In this situation an explosion-like process leads to the total disintegration of the nucleus and the multiple emission of nuclear fragments of different masses (1 and references therein). One can come to the concept from a quite different starting point, by considering a liquid-gas phase transition in excited nuclear matter. The name multifragmentation is introduced firstly in Ref. (2). At high energy collisions, the produced particles are not confined up to nuclear fragments but they include essentially created particles the so called hadrons. It is known that, the radiation therapy is the medical use of ionizing radiation to treat cancer. In conventional radiation therapy, beams of X-rays (high energy photons) are produced by accelerated electrons and then delivered to the patient to destroy tumor cells. Using crossing beams from many angles, radiation oncologists irradiate the tumor target while trying to spare the surrounding normal tissues. Inevitably some radiation dose is always deposited in the healthy tissues. Initially, the clinical applications are limited to few parts of the body since the accelerators are not powerful enough to allow protons to penetrate deep in the tissues. The improvements in accelerator technology coupled with advances in medical imaging and computing, make proton therapy a viable option for routine medical applications. Therefore, proton becomes the most common type of particle therapy. However, the photon as a particle is used in X-ray and -ray, the so called photon therapy. Muon and electron, the so called lepton therapy, are occasionally attempted. All the particles that are constructed of quarks (hadrons) are not elementary. Therefore, in their usage, it is more correctly to say hadron therapy. When the irradiating beams are made of charged particles (protons, -particle, and heavier ions), radiation therapy is also called hadron therapy or heavy-ion therapy. The strength of hadron therapy lies in the unique physical and radiobiological properties of these particles. They can penetrate the tissues with little diffusion and deposit the maximum energy just before stopping. This allows a precise definition of the specific region to be irradiated. With the use of the hadron the tumor can be irradiated while the damage to healthy tissues is less than with X-rays. Although protons are used in several hospitals, the next step in radiation therapy is the use of carbon ions. These have some clear advantages even over protons in providing both a local control of very aggressive tumors and a lower acute or late toxicity. At HIMAC (NIRS, Chiba, Japan) Kanai et al Ref. (3 and references therein) study the fragmentation of (0.09A and 0.5A GeV iron) and 0.4A GeV krypton beams in tissue equivalent material.For radiotherapy at GSI (Darmstadt, Germany) information on carbon fragmentation in tissue-like materials is of great interest (4, 5) . For shielding applications, relatively light ions such as helium, carbon, neon, and silicon are worth studying both in their own right and because they are produced as secondary fragments by interactions of heavier primary ions in shielding and in the human body. In support of the HIMAC radiotherapy program, Kanai et al Ref. (3 and references therein) use the fragmentation of (0.15A GeV, 0.29A, and 0.4A GeV) 12