The Radiation Effects Of Soft X-rays From Synchrotron Radiation

As is valuable radiation damage in risk evaluation and radiation protection, the radiobiological studies of X-ray are attracted for attentions in these years, and even more, soft X-rays, which have higher linear energy attenuation coefficients, have attracted more interesting. For the reasons, firstly, as low energy rays, the main is photon-electron absorption when soft X-rays interacting with matter and large numbers of photoelectrons, also combining with large numbers of Auger electrons, and there second electrons have track path with nanoscale and can deposit energies in small space, which can cause the structure damage of macromeolecule in cells, thus can cause radiation damage in cells. At the same time, the effect of radiation damage is increasing with the X-ray energy decreasing and is more higher than that of hard X-rays and 60Co-γrays.Using soft X-rays from synchrotron radiation are valuable for radiobiological studies. The synchrotron radiation has many valuable characteristics, such as have high radiation flux and the radiation energy can be adjusted continuously. When using synchrotron radiation as the radiation source, the higher radiation fluxes can be obtained and more samples can be treated each time, and thus the experimental results can be more suitable for statistical principle. At the same time, with the help of synchrotron radiation, the radiation damage studied with selected energies can come true and thus the radiation damage with different energies can be studied. Also the radiation effects of soft X-rays with different energies, which have similar transmission abilities in cells, can be compared, thus the radiobiological effects of soft X-rays at different layer can be studied.As with other radiation source, the X-rays at"water window"region have their unique characteristics and also an advantage for synchrotron radiation. The X-rays at"water window"region are low energy rays and large numbers second electrons are produced in cells when transmitting through cells. At the same time, the K-shell absorption edges of C, N, O elements, which are also the main composing elements of biological cells, are all in this region. When cells irradiated with soft X-rays at the K-shell edges of those elements, more dose will be deposited in cells because of resonance absorption and the radiation damage may be more serious.Considering the specialties of soft X-rays from synchrotron radiation, using the bending magnet radiation of Hefei synchrotron radiation as the radiation source and the zone plate as dispersively optical element, the synchrotron radiation was monochromated and the radiation damage characteristic of soft X-rays at"water window"was studied, including different energies irradiating, the radiation damage discrepancy of soft X-rays near the absorption edges and the radiation damage enhancement of X-rays at the K-shell edges, etc. The studies included soft X-rays causing nucleolus radiation damage, cell killing, mutating and the difference of different compartments of cells. At the same time, the infrared spectrum of synchrotron radiation and gel electrophoresis technique were used as valuable tools for radiation results detecting and analyzing, and also for some influence factors discussing. The peculiar radiation damage of soft X-rays with different energies at"water region"was studied.The experimental results showed that soft X-rays at"water window"region have high radiation damage abilities, and the radiobiological effects are higher than that of 60Co-γrays and the radiation increases with the X-ray energies increasing. At the same time, the radiation effects of X-rays at the K-shell absorption edges are also different. All these indicate that soft X-rays at"water window"region have peculiar radiation damage effects.