SISAK Liquid-Liquid Extraction Experiments with Preseparated 257Rf
SISAK Liquid-Liquid Extraction Experiments with Preseparated 257Rf
复制标题
使用预分离的 257Rf 进行 SISAK 液-液萃取实验
DOI：
10.14494/jnrs2000.3.121
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
G. Skarnemark
中科院分区：
文献类型：
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作者：
G. Skarnemark
采用西萨克液-液萃取系统提取4.0-s257 Rf。257 Rf在208 Pb（50 Ti，1 n）257 Rf反应中产生，靶上具有237 MeV的束流能量，在伯克利充气分离器（BGS）中分离，并使用反冲转移室（RTC）转移到气体射流中。将由气体喷射递送的活性溶解在6-M HNO 3中，并将Rf萃取到甲苯中的0.25-M二丁基磷酸中。这是第一次有一个transactinide，即，一种Z ≥ 104的元素被提取出来，并通过西萨克系统明确地鉴定。因此，该中试实验表明，快速液-液萃取系统西萨克与液体闪烁探测器组合，可用于研究反式锕系元素的化学性质。提取结果与Rf族IV同系物Zr和Hf所示的行为一致。和输出。2-4近年来，在研究超锕系元素（Z ≥ 104）的化学性质方面，已开展了使用西萨克的工作。2，5，6发现的唯一合适的检测方法是液体闪烁（LS）检测。7这主要是因为西萨克系统中遇到的流速相当高（0.5-2.0 mL/s）。其他检测方法通常需要薄的干燥样品或非常薄的液体膜。没有发现合适的方法来制备这样的样品，而分离和检测之间没有不可接受的时间延迟。LS计数效率高，但能量分辨率较低（在7 MeV α能量下，半高宽约为300 keV），对β粒子和γ射线敏感。这对分离系统提出了非常严格的要求，因为大多数β-和γ-发射污染物的产率比所研究的反锕系元素高出几个数量级。人们付出了巨大的努力来开发在这些条件下LS检测极低水平α活性的方法。·使用脉冲形状鉴别来将α谱中的β背景降低>1000倍。如果没有这种技术，来自周围环境和靶中产生的核素的β和γ诱导本底将干扰α谱，以至于α谱变得无用。8.通过连续测量662 keV ~（137）Cs γ射线的康普顿边来实时监测中子产额。康普顿边缘的位置用于自动调整能量校准。基于该调整，用于在母模式和子模式之间切换检测单元（分别为打开或关闭阀）的事件门将始终被设置在正确的能量范围上。9
The SISAK liquid-liquid extraction system was used to extract 4.0-s 257 Rf. The 257 Rf was produced in the reaction 208 Pb( 50 Ti, 1n) 257 Rf with 237-MeV beam energy on target, separated in the Berkeley Gas-filled Separator (BGS) and transferred to a gas jet using the Recoil Transfer Chamber (RTC). The activity delivered by the gas jet was dissolved in 6-M HNO3 and Rf was extracted into 0.25-M dibutyl-phosphoric acid in toluene. This was the first time a transactinide, i.e., an element with Z ≥ 104, was extracted and unequivocally identified by the SISAK system. Thus, this pilot experiment demonstrates that the fast liquid-liquid extraction system SISAK, in combination with liquid- scintillation detectors, can be used for investigating the chemical properties of the transactinides. The extraction result is in accordance with the behaviour shown by the Rf group IV homologues Zr and Hf. and output. 2-4 During recent years, work has been undertaken to deploy SISAK in studies of the chemical properties of the transactinide elements (Z ≥ 104). 2, 5, 6 The only suitable detection method found was liquid-scintillation (LS) detection. 7 This was mainly because of the rather high flow rates (0.5-2.0 mL/s) encountered in the SISAK system. Other detection methods usually require either thin, dry samples or very thin liquid films. No suitable method was found to prepare such samples without an unac- ceptable time delay between separation and detection. LS counting has high efficiency, but suffers from relatively poor energy resolution (about 300-keV FWHM at 7-MeV α en- ergy) and is sensitive to β particles and γ rays. This puts very stringent demands on the separation system, because most of the β- and γ-emitting contaminants are produced with orders of magnitude higher yield than the transactinide under study. A huge effort was made to develop methods for LS detection of very low levels of α activity under these conditions. The most important techniques implemented are: • Pulse-shape discrimination is used to reduce the β back- ground in the α spectra by a factor >1000. Without this tech- nique the β- and γ-induced background from the surroundings and from nuclides produced in the target will interfere with the α spectrum to such an extend that it becomes useless. 8 • Real-time scintillation-yield monitoring by continuous mea- surement of the Compton edge of 662-keV 137 Cs γ rays. The position of the Compton edge is used to automatically adjust the energy calibration. Based on this adjustment the event gates used for switching the detection cells between mother and daughter mode (open or closed valve, respectively) will always be set on the correct energy range. 9