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由公式(1)可知辐射流
$\int {I\left( E \right)} $ 的不确定度来源于电压U、中性衰减片透过率${R_N}(E)$ 、FXRD系统响应函数、限孔大小S、安装距离r、示波器阻抗Z、衰减器衰减倍率A、辐射源面积${A_s}$ 和相对辐射源法向角度θ。FXRD系统响应函数由滤片透过率${R_f}(E)$ 和阴极响应函数${R_{{\rm{XRD}}}}(E)$ 决定,计算中分别考虑两者不确定度。其中每个参数的不确定度由多个影响因素决定,比如实验测量带来的不确定度、标定带来的不确定度、算法带来的不确定度、机构精度带来的不确定度等。具体的类目如表1[12]所示。Category Components Source of uncertainty Uncertainty of component Comprehensive uncertainty Measurement Oscilloscope Voltage measurement noise 2% 3.17% (changes with Tr) Verification accuracy 1% Cable Transmission loss 1%+1% Attenuator Attenuation bias 0.3% Verification accuracy 1% Calibration Neutral filter Calibration accuracy 2% 8.9% (changes with Tr) Face uniformity 2% flat-response filter Calibration accuracy 2% Face uniformity 1% XRD Calibration accuracy 1.5% Face uniformity 8% Algorithm Reduction algorithm Response flatness 1% (peak) 1% (changes with Tr) without reduction algorithm Response flatness of F/M-XRD <15% <15% (eliminated) Mechanical Solid angle Aperture punching accuracy 0.5% 1.1% (stable) Distance from aperture to target Angle Effect of installation angle on field of view 1% Table 1. Summary table of sources of radiation flux intensity uncertainty
实际使用加权算法还原谱与响应函数的相互作用,消去未使用还原的不确定度,但是标定数据会因为加权还原算法带来额外的不确定度,这一部分引入的不确定度必须有真实辐射源的能谱与加权用能谱的差来进行计算,涉及非线性迭代还原方法,所以主要依靠蒙特卡罗方法进行计算,表1中已经考虑此因素。同时整形脉冲中低温辐射温度下也会带来算法不确定度,其随温度变化函数已于前文中进行计算。而示波器、电缆、衰减器、衰减片、滤片、XRD阴极等不确定度都会随辐射温度的变化而变化,由于机构带来的不确定是不随辐射温度变化的。各个影响因素的相对不确定度随辐射温度变化的曲线如图9所示,注意
$\displaystyle \int {I(E){\rm{d}}E} \sim {T^4}$ ,所以表格数据和图像数据是经过转化得到的。从图9可以看出,在辐射温度较低区间,整体的不确定度会发生陡升,主要影响因素就是低温辐射温度下FXRD的响应存在的不确定性带来的算法不确定度。
Signal processing method for shaped pulse and radiation flux deviation in low temperature
doi: 10.3788/IRLA20200181
- Received Date: 2020-05-15
- Rev Recd Date: 2020-08-29
- Available Online: 2020-07-20
- Publish Date: 2020-11-25
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Key words:
- inertial confinement fusion /
- shaped pulse /
- flat-response X-ray diode /
- signal splicing /
- radiation flux in low temperature
Abstract: Flat response X-ray diodes have been widely used in large-scale laser devices at home and abroad for the measurement of angularly distributed X-ray radiation flux. In practical experiments, flat-response X-ray diodes measure radiation flux images that have a step change in a shaped pulse-driven radiation source. In order to ensure a good signal-to-noise ratio, a single signal will be connected to multiple channels of the oscilloscope, and then the signals of different channels will be processed, and the final image with good signal-to-noise ratio will be stitched. The research in this paper mainly introduced this data processing method and gave theoretical calculations. At the same time, a theoretical approximation and numerical simulation of a deviation in the calculation of the low temperature radiation flow reduction were made, and the relative uncertainty of the deviation was obtained. Coupled with the uncertainty of all factors, the curve of the overall uncertainty of the flat-response X-ray diode as a function of the radiation temperature was obtained, which realized precise diagnosis and completed the experimental needs for diagnosis.