Fundamental study on uranium enrichment by nuclear excitation in laser plasma

从实验和理论上研究了~(235)U和~(235)U在激光产生的铀等离子体中的核激发。该方案可能适用于铀浓缩。金属天然铀靶被聚焦的&lt；CO2&gt；激光照射。~lt；~(235)U&gt；的26分钟异构体是由NEET(电子跃迁核激发)产生的，从~lt；~(235)U&gt；的同素水平上探测到了内转换电子，并根据激发核数估算了~lt；~(235)U&gt；在激光产生的等离子体中被核激发的几率。通过改变激光对铀靶的聚焦条件，测量了激发速率与等离子体中同质异能态能级的温度关系，并与理论预测的关系进行了比较。当电子温度低于50 eV时，没有观察到异构体的产生。400-500 eV的电子温度有利于~lt；(235)U&gt；在等离子体中的核激发，核激发效率随等离子体电子密度的增加而线性增加，这从1&lt；m(Nd：YAG激光)和10&lt；m(&lt；CO_2&gt；激光)激发效率的比较中得到了证实。这表明颗粒内爆可以提高~(235)U&gt；异构体的产率。

Nuclear excitation of <^(235)U> in a laser produced uranium plasma has been investigated experimentally and theoretically. This scheme may be applicable to uranium enrichment.A metallic natural uranium target was irradiated by a focused <CO_2> laser beam. The 26 min isomers of <^(235)U> were produced by NEET (Nuclear Excitation by Electron Transition), which were confirmed by detecting the internal conversion electrons from the isomeric level of <^(235)U> nucleus.The probability of the nuclear excitation of <^(235)U> in the laser produced plasma was estimated from the number of the excited nuclei. The value experimentally obtained was fairly in good agreement with the theoretically expected value.The temperature dependence of the excitation rate to the isomeric level in the plasma was measured by varying the focusing condition of the laser beam to the uranium target, and was compared with the theoretically predicted dependence. When the electron temperature is lower than 50eV, the production of the isomer was not observed. The electron temperature of 400-500eV is favorable for the nuclear excitation of <^(235)U> in the plasma.The efficiency of nuclear excitation increased linearly with the electron density of the plasma, which was confirmed from the comparison of the excitation rates by 1 <micro> m (Nd:YAG laser) and 10 <micro> m ( <CO_2> laser) irradiations. This shows the availability of the pellet implosion to improve the production rate of <^(235)U> isomers.