Prototype 1 MeV X -band linac for aviation cargo inspection
Prototype 1 MeV X -band linac for aviation cargo inspection
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DOI：
10.1103/physrevaccelbeams.22.020101
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发表时间：
2019-02
影响因子：
1.7
通讯作者：
M. Jenkins;G. Burt;A.V.P. Kumar;Y. Saveliev;P. Corlett;T. Hartnett;Robert B. Smith;A. Wheelhouse;P. Mcintosh;K. Middleman
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文献类型：
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作者：
M. Jenkins;G. Burt;A.V.P. Kumar;Y. Saveliev;P. Corlett;T. Hartnett;Robert B. Smith;A. Wheelhouse;P. Mcintosh;K. Middleman
航空货物单元装载装置（ULD）集装箱通常比标准海运集装箱小得多，体积约为1 m3。标准的3-6 MeV X射线屏蔽直线加速器具有太多的能量，在检查ULD时无法获得足够的对比度，因此需要较低的1 MeV直线加速器。为了获得可适应移动的平台应用的小的物理占地面积，需要紧凑的设计，因此X波段射频技术是理想的解决方案。一个原型的1.45 MeV直线加速器腔优化此应用程序已被设计的兰开斯特大学和科学技术设施理事会（STFC），由Comeb（意大利）制造和测试在达雷斯伯里实验室使用的e2 v磁控管，调制器和电子枪。腔体为双周期π/2结构，通过束管孔径耦合，以牺牲分流阻抗为代价简化了制造，同时保持了尽可能小的横向尺寸。介绍了这种直线加速器结构的设计、制造和测试。为了优化图像，有必要能够修改直线加速器的能量。它可以通过改变磁控管的射频功率来改变，但这也会改变磁控管的频率。通过改变束流从0-70 mA的束能量从1.45变化到1.2 MeV。这允许通过改变电子枪上的聚焦电极偏置电压来快速改变能量，同时通过改变重复频率来保持剂量率恒定。通过改变射频功率和通过改变束流来改变束能量都进行了实验研究。电子束上的动量扩散在1%和5%之间，取决于0-70 mA的束流
Aviation cargo unit load device (ULD) containers are typically much smaller than standard shipping containers, with a volume of around 1 m3. Standard 3-6 MeV x-ray screening linacs have too much energy to obtain sufficient contrast when inspecting ULDs, hence a lower 1 MeV linac is required. In order to obtain a small physical footprint, which can be adapted to mobile platform applications, a compact design is required, hence X-band radio-frequency technology is the ideal solution. A prototype 1.45 MeV linac cavity optimized for this application has been designed by Lancaster University and Science and Technology Facilities Council (STFC), manufactured by Comeb (Italy) and tested at Daresbury Laboratory using an e2v magnetron, modulator, and electron gun. The cavity is a bi-periodic π/2 structure, with beam-pipe aperture coupling to simplify the manufacture at the expense of shunt impedance, while keeping the transverse size as small as possible. The design, manufacture, and testing of this linac structure is presented. In order to optimize the image it is necessary to be able to modify the energy of the linac. It can be changed by altering the rf power from the magnetron but this also varies the magnetron frequency. By varying the beam current from 0-70 mA the beam energy varied from 1.45 to 1.2 MeV. This allows fast energy variation by altering the focus electrode bias voltage on the electron gun while keeping the dose rate constant by varying the repetition frequency. Varying the beam energy by varying the rf power and by varying the beam current are both studied experimentally. The momentum spread on the electron beam was between 1% and 5% depending on the beam current of 0-70 mA