Lifetime measurements in heavy elements using the charge plunger technique

这项研究的目的是使用最近在于韦斯屈莱大学加速器实验室委托的电荷柱塞装置测量重核的寿命。由于依赖于检测在不同速度区域（降能器箔之前和之后）的核衰变中产生的多普勒频移伽马射线，使用标准柱塞技术难以测量具有大内部转换系数的重元素的寿命。一个补充的方法，具有高的内部转换系数的核是电荷柱塞技术;一个标准的反冲距离多普勒频移（RDDS）方法的修改，该技术利用电荷复位箔，从而离子的电荷被重置到一个值取决于它们的速度。一旦在靶处的聚变-蒸发反应中产生，通过内转换衰变的反冲核随后可能由于俄歇效应而使其离子电荷增加。改变靶到箔的距离允许通过计数在重置箔之前和之后发生的转换事件的数量来探测核寿命的灵敏度。由此产生的反冲离子的电荷形状分布反映了在它们的飞行时间期间发生的过程，并且允许使用微分衰变曲线方法（DDCM）或通过将贝特曼方程拟合到数据来提取核寿命。本研究旨在通过采用上述电荷柱塞技术，首次测量No-254（以及可能的其他transfermium核）中非同质异能态的寿命。

This research aims to measure lifetimes of heavy nuclei using the recently commissioned charge plunger device at the University of Jyväskylä Accelerator Laboratory. Lifetime measurements in heavy elements with large internal conversion coefficients prove difficult using standard plunger techniques, due to the reliance on the detection of Doppler shifted gamma-rays produced in nuclear decays at different velocity regions (before and after a degrader foil). A complementary approach for nuclei with high internal conversion coefficients is the charge plunger technique; a modification of the standard recoil distance Doppler-shift (RDDS) method, the technique utilises a charge reset foil, whereby the charge of ions is reset to a value dependent on their velocity. Once produced in fusion-evaporation reactions at a target, recoiling nuclei that decay via internal conversion may subsequently have their ionic charge increased due to the Auger effect. Varying the target-to-foil distance allows for the sensitivity of nuclear lifetimes to be probed, by counting the number of conversion events that occurred before and after the reset foil. The resulting charge shape distribution of recoil ions reflect the processes that occurred during their time of flight and allows for nuclear lifetimes to be extracted using the differential decay curve method (DDCM), or by fitting Bateman equations to the data. This research aims to make the first measurements of the lifetime of a non-isomeric state in No-254 (and possibly other transfermium nuclei) by employing the charge plunger technique described above.