Investigation Of The Technology For The Measurement Of Low Energy X Ray's Photon Flux

Recently with the development of the scientific technology, the low energy X rays is used broadly, so it's necessary to measure the low energy X ray's absolute intensity. Take ialrology, industry, nuclear weapon storage, nuclear experiments for example, if we can measure the low energy X ray's photon fluence, one side we can determine the X ray's energy and intensity precisely; on the other hand, according to the measured data we can collocate a suit of proper radioprotection, do our best to insure the personnel dose under the safe value.The AXUV photodiodes have several advantages over the orthodox tube-type XUV detectors. The AXUV photodiodes exhibit very low noise, do not need external voltages for their operation, are insensitive to magnetic firlds,cost less to fabricate, have low mass and have large collection area to size ratio making them extremely attractive for use in many research laboratories around the world. They are also used as transfer standards in the XUV spectral range because of their ease of use, excellent stability and spatial homogeneity of quantum efficiency, large dynamic range (over eight orders of magnitude) small size, ruggedness and ultrahigh vacuum compatibility. It is proved that the semiconductor detectors are proper to be used as a kind of tool in the research of the low energy X-ray photon fluuence's measurement. This kind of use has become a trend in this research field.The following major factors influencing the TL(thermo luminescent) detector response were taken into account:(i) Mass energy absorption coefficients for LiF(Mg,Ti) and air;(ii) Attenuation of low energy X rays in a thick TL detector;(iii) Self-absorption of thermoluminescence light in a thick TL detector;(iv) The relative TL efficiency (intrinsic luminous efficiency), which depends strongly on the photon energy via radiation density.According to the investigation into the development status at home and abroad, found that using the AXUV-100 photodiodes as the standard detector and the LiF(Mg,Ti) thermoluminescent detector as the out-spot metrical detector is a perfect combine in the low energy X ray's photon flux research.When the energy is low, especially for the X rays whose energy lower than 50keV, it's very difficult to measure the X ray's photon flux. There are four reasons accounting for this question.Photoeffect is the main attraction when the low energy photons pass through some medium, its mass energy absorption coefficient varies following the photon energy and the matter's atomic number. Because of its energy dependence, we have to know the low energy X ray's spectra clearly, but it is very difficult;The low energy photon's mass energy absorption coefficient is large at some extent, so the low energy X rays will be absorpted strongly;When the exposure rate is high (not only for the low energy X rays), it's necessary close with the X rays diode's target bulk. In this kind of measurement, the detectors should not have rate (exposure rate or dose rate) dependence, so we have to test the detector's dose-dose rate reciprocity theorem but this experiment is very difficult;For the low energy X rays, its secondary electron's energy are very low, so it's necessary to investigate the detector's LET(Linear Energy Transfer)dependence on the low energy X ray's energy response.In order to meet the laboratory's requirement, we want to use AXUV-100 and LiF (Mg, Ti)-TLD these two kind of detectors to solve the following questions.(i) The measurement of photon fluence for the low energy X rays;(ii)Determine energy responses for AXUV-100 photodiode and LiF(Mg,Ti)-TLD to the low energy X rays;(iii)Determined the corrections of the AXUV-100 photodiode and LiF(Mg,Ti)-TLD,used in the measurement of low energy X ray's photon fluence;(iv)Attest the new calibrate method used in the AXUV-100 photodiode's calibrating progress and the LiF(Mg,Ti)-TLD's calibrate method.From the passed two year's experiments, achieving the following conclusions:(i)We used a new calibrating method in the experiment, its essential is calibrate the AXUV-100's silicon thickness precisely in the ¹³⁷Csγfield, putting the photodiodes in the CPE(charged particle equilibrium) condition, if we know the radiation source's exposure, measuring the signals at different spots on the same line, computing the detector's silicon thickness. If we don't know the field's exposure, using the TLD as an assistant to measure the source's photon fluence;(ii)Compared the calibration results in theγfield with the results came from the synchrotron device, achieving a coincident result, which proving the validity of the new calibrating method;(iii)Investigated the LiF(Mg,Ti)-TLD's repetition rate, achieving an ideal result, and with the help of the result from the synchrotron device, computing the detector's self-absorption coefficient ,TL efficiency(intrinsic luminous efficiency) and the correct factors of TLD used in the measurement of the low energy X rays;(iv)Calibrated the filter's multiple in the symmetricalγfield and computed the uncertainty; (v)With the help of AXUV-100 silicon photodiode and LiF(Mg,Ti)-TLD, measured the low energy X ray's photon fluence , gave the experimental step and the computational formulae.This is an applicable researchful subject, which established a plat for the following investigation, has an actual significance.