脉冲硬X射线能注量测量技术

Energy fluence measurement for pulse hard X-ray

阐述了全吸收法测量脉冲硬X射线能注量的基本原理,选择了光电管配合硅酸镥(LSO)闪烁体作为探测系统的核心部件,研制了脉冲硬X射线能注量测量系统.利用该系统测量了"闪光二号"加速器产生的脉冲硬X射线强度,结合灵敏度的实验标定结果,计算得到了脉冲硬X射线的能注量.在连续5发次的实验中,能注量平均测量结果为35.9 mJ/cm^2,根据实测剂量和能谱计算得到的能注量为39.8 mJ/cm^2,两者的结果比较一致.

Pulsed high-energy fluence X-ray source is based on the“Flash II”accelerator.It can be used to carry out effect vulnerability and sensitivity test of unit level system generated electromagnetic pulse(SGEMP).The energy fluence of pulsed hard X-ray is a main parameter of the equipment beam.At present,theoretical calculation method is widely used.Energy fluence can be calculated according to the dose,energy spectrum and energy absorption coefficient of each energy segment.The principle measuring energy fluence of pulsed hard X-ray by total absorption method is introduced.The photoelectric cell with lutetium silicate(LSO)scintillator is selected as a core component of the detection system,and the measurement system is developed.It is composed of scintillation detector,LSO scintillator,dimmer film,photon collimator,visible light shielding material,power supply and signal collecting system.The conversion coefficient between the incident photon energy and the waveform parameter is calibrated by a standard X-ray source.The energy fluence measurement experiment is carried out with the high-energy beam source of the“Flash II”accelerator as an experimental platform.In order to meet the requirements of the effect test experiments,the series diode structure is used in the accelerator for forming a high strength and large area uniform X-ray source.In the experiment,the LiF TLD is located in the front of the phototube and used to monitor the dose.According to the measured waveform,the actual energy of the incident photons is calculated.Combined with the receiving area of incident photons,the energy fluence of pulsed hard X-ray is calculated.The average measured value is 35.9 mJ/cm^2 in 5 consecutive experiments.Energy fluence calculated from the measured dose and energy spectrum is 39.8 mJ/cm^2.The results of the two methods are compared.It can be found that the experimental result is about 9.8%smaller than the theoretical value.The reasons are as follows.According to the law of exponential decay of rays in matter,in fact,the scintillator cannot absorb all the rays,and some of the rays can penetrate through,the energy of these rays cannot be detected,and thus giving rise to small experimental value.Due to the limited energy point of quasi-monoenergetic source,the sensitivity under the mean photon energy is taken as the sensitivity of the detector,and therefore there is a certain degree of uncertainty.The successful application of the measurement technology provides a good experimental method for the following similar research,and can also provide a reference for X-ray intensity analysis.