Recent progress of study on gas electron multiplier (GEM) has been described. Due to its fast time re-sponse and excellent position sensitivity, the GEM will find wide applications in particle physics, medicine and as...Recent progress of study on gas electron multiplier (GEM) has been described. Due to its fast time re-sponse and excellent position sensitivity, the GEM will find wide applications in particle physics, medicine and as-trophysics. These potential applications have been briefly introduced.展开更多
Among the various micro-pattern gas detectors (MPGD) that are available, the gas electron multiplier (GEM) detector is an attractive gas detector that has been used in particle physics experiments. However, the GEM de...Among the various micro-pattern gas detectors (MPGD) that are available, the gas electron multiplier (GEM) detector is an attractive gas detector that has been used in particle physics experiments. However, the GEM detector usually needs thousands of preamplifier units for its large number of micro-pattern readout strips or pads, which leads to considerable difficulties and complexities for front end electronics (FEE). Nowadays, by making use of complementary metal-oxide semiconductor (CMOS)-based application specific integrated circuit (ASIC), it is fea- sible to integrate hundreds of preamplifier units and other signal process circuits in a small-sized chip, which can be bound to the readout strips or pads of a micro-pattern particle detector (MPPD). Therefore, CMOS ASIC may provide an ideal solution to the readout problem of MPPD. In this article, a triple GEM detector is constructed and one of its readout strips is connected to a CMOS charge-sensitive preamplifier chip. The chip was exposed to an 55Fe source of 5.9 keV X-ray, and the amplitude spectrum of the chip was tested, and it was found that the energy resolution was approximately 27%, which indicates that the chip can be used in triple GEM detectors.展开更多
为揭示蒙古冰草对氮添加的响应机制,设置5个氮添加水平(0,0.8,1.6,2.4,4.0 g N·m^(-2)·a^(-1))对蒙古冰草进行为期2个月处理后,测定根系、叶片中可溶性糖、淀粉、碳(C)、氮(N)、磷(P)的含量,分析氮添加对蒙古冰草叶片、根系...为揭示蒙古冰草对氮添加的响应机制,设置5个氮添加水平(0,0.8,1.6,2.4,4.0 g N·m^(-2)·a^(-1))对蒙古冰草进行为期2个月处理后,测定根系、叶片中可溶性糖、淀粉、碳(C)、氮(N)、磷(P)的含量,分析氮添加对蒙古冰草叶片、根系非结构性碳水化合物(NSCs)与C、N、P含量及其化学计量特征关系的影响。结果表明:2.4 g N·m^(-2)·a^(-1)的氮素添加显著提高了蒙古冰草叶片、根系NSCs含量与C、N、P含量,且不同器官的响应有显著差异性(P<0.05)。叶片NSCs含量与叶片N、可溶性糖、淀粉含量、C/P及N/P呈显著正相关关系,与叶片P含量、C/N呈显著负相关关系(P<0.05);根系NSCs含量与根系C、N、C/P、N/P、可溶性糖和淀粉含量呈显著正相关(P<0.05)。叶片与根系N/P是影响蒙古冰草体内可溶性糖积累的主要因子;根系N含量与叶片P含量共同影响淀粉含量;叶片P含量、根系N含量及根系N/P综合影响NSCs含量。综上,适量的氮添加会缓解研究区蒙古冰草的N限制,促进NSCs合成,而大量氮添加会导致N、P比例失衡,加剧P限制。因此,未来气候变化背景下蒙古冰草人工草地种植或退化草地恢复管理过程中需要考虑优化氮肥施用量与适当的磷添加。展开更多
A new method to monitor the energy variation of a multi-energy electron linac by combining a Cerenkov detector and a CsI（Tl） detector is reported. The signals in the Cerenkov detector show an appreciable but differe...A new method to monitor the energy variation of a multi-energy electron linac by combining a Cerenkov detector and a CsI（Tl） detector is reported. The signals in the Cerenkov detector show an appreciable but different dependence on the energy of the electron linac from the traditional CsI（Tl） detector due to the particular response of the former to charged electrons with high velocity above threshold. The method is more convenient than the HVL （half-value layer） method which is commonly employed to calibrate the energy of an electron linac for real time monitoring. The preliminary validity of the method is verified in a dual-energy electron linac with 6 MeV and 3 MeV gears. Moreover, the method combining the Cerenkov detector and the CsI（Tl） detector is applicable to probe the X-ray spectrum hardened by the inspected material and may serve as a novel tool for material discrimination with effective atomic number in radiation imaging.展开更多
文摘Recent progress of study on gas electron multiplier (GEM) has been described. Due to its fast time re-sponse and excellent position sensitivity, the GEM will find wide applications in particle physics, medicine and as-trophysics. These potential applications have been briefly introduced.
文摘Among the various micro-pattern gas detectors (MPGD) that are available, the gas electron multiplier (GEM) detector is an attractive gas detector that has been used in particle physics experiments. However, the GEM detector usually needs thousands of preamplifier units for its large number of micro-pattern readout strips or pads, which leads to considerable difficulties and complexities for front end electronics (FEE). Nowadays, by making use of complementary metal-oxide semiconductor (CMOS)-based application specific integrated circuit (ASIC), it is fea- sible to integrate hundreds of preamplifier units and other signal process circuits in a small-sized chip, which can be bound to the readout strips or pads of a micro-pattern particle detector (MPPD). Therefore, CMOS ASIC may provide an ideal solution to the readout problem of MPPD. In this article, a triple GEM detector is constructed and one of its readout strips is connected to a CMOS charge-sensitive preamplifier chip. The chip was exposed to an 55Fe source of 5.9 keV X-ray, and the amplitude spectrum of the chip was tested, and it was found that the energy resolution was approximately 27%, which indicates that the chip can be used in triple GEM detectors.
文摘为揭示蒙古冰草对氮添加的响应机制,设置5个氮添加水平(0,0.8,1.6,2.4,4.0 g N·m^(-2)·a^(-1))对蒙古冰草进行为期2个月处理后,测定根系、叶片中可溶性糖、淀粉、碳(C)、氮(N)、磷(P)的含量,分析氮添加对蒙古冰草叶片、根系非结构性碳水化合物(NSCs)与C、N、P含量及其化学计量特征关系的影响。结果表明:2.4 g N·m^(-2)·a^(-1)的氮素添加显著提高了蒙古冰草叶片、根系NSCs含量与C、N、P含量,且不同器官的响应有显著差异性(P<0.05)。叶片NSCs含量与叶片N、可溶性糖、淀粉含量、C/P及N/P呈显著正相关关系,与叶片P含量、C/N呈显著负相关关系(P<0.05);根系NSCs含量与根系C、N、C/P、N/P、可溶性糖和淀粉含量呈显著正相关(P<0.05)。叶片与根系N/P是影响蒙古冰草体内可溶性糖积累的主要因子;根系N含量与叶片P含量共同影响淀粉含量;叶片P含量、根系N含量及根系N/P综合影响NSCs含量。综上,适量的氮添加会缓解研究区蒙古冰草的N限制,促进NSCs合成,而大量氮添加会导致N、P比例失衡,加剧P限制。因此,未来气候变化背景下蒙古冰草人工草地种植或退化草地恢复管理过程中需要考虑优化氮肥施用量与适当的磷添加。
文摘A new method to monitor the energy variation of a multi-energy electron linac by combining a Cerenkov detector and a CsI（Tl） detector is reported. The signals in the Cerenkov detector show an appreciable but different dependence on the energy of the electron linac from the traditional CsI（Tl） detector due to the particular response of the former to charged electrons with high velocity above threshold. The method is more convenient than the HVL （half-value layer） method which is commonly employed to calibrate the energy of an electron linac for real time monitoring. The preliminary validity of the method is verified in a dual-energy electron linac with 6 MeV and 3 MeV gears. Moreover, the method combining the Cerenkov detector and the CsI（Tl） detector is applicable to probe the X-ray spectrum hardened by the inspected material and may serve as a novel tool for material discrimination with effective atomic number in radiation imaging.
