Cross sections for forming radionuclides from the interaction of protons with energies up to 70 meV with zirconium
Cross sections for forming radionuclides from the interaction of protons with energies up to 70 meV with zirconium
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能量高达 70 meV 的质子与锆相互作用形成放射性核素的横截面
DOI：
10.1007/bf01123536
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发表时间：
1991
期刊：
影响因子：
--
通讯作者：
V. V. Tokarevskii
中科院分区：
文献类型：
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作者：
S. N. Kondtrat'ev;V. Kuzmenko;Y. Lobach;V. Prokopenko;V. D. Sklyarenko;V. V. Tokarevskii
在先前研究的延续中，我们研究了能量高达70 MeV的质子与天然同位素锆相互作用形成长寿命放射性核素的激发函数。需要实验数据来验证现有的理论模型：1)高激发能核的特性；2)核反应机理；3)核常数的系统论，这些在活化分析、设计屏蔽等方面都需要用到。到目前为止，用质子照射锆形成放射性核素的截面只测量了9~[2,3]。为了研究理论上预测核素形成激发函数的可能性，我们对Weisskopf—Ewing蒸发模型[4]和预平衡粒子发射的几何依赖混合模型[5]进行了计算。然后比较了计算截面和实验截面。实验。用诱导活化法测量了放射性核素形成的截面与入射粒子能量的关系。用入射能量高达70兆电子伏的质子束照射这组样品，散射为0。5兆电子伏特的U-240回旋加速器在IYaI苏联。测量质子能量的误差为3兆电子伏。样品为17 mg/ cm2厚的天然锆箔（51.46% 90Zr, 11.23% 91Zr, 17.11% 92Zr, 17.41% 94Zr, 2.80% 98Zr）。通过与已知反应X7Al (p, 3pn) e4Na、Fe (ppm) 56Co和Fe (p, 3pxn) 51Cr的截面比较，确定了绝对截面[1,6,7]。因此，除锆外，该组样品还包括天然同位素组成为铝和铁的箔；铝箔厚度分别为15和55 mg/ cm2。通过在样品集中加入控制箔，确定了次级中子和7量子对样品活性的贡献可以忽略不计。用体积为100 cm 3的Ge （Li）探测器测量了样品的诱导活度，能量分辨率为2.8 keV, E} = 1332 keV(6~)，实验方法详见[1]。表1给出了放射性核素的半衰期，用于确定这些核素的活性的-射线的能量和量子产率，表1显示了所有同位素的阈值能量< 50 MeV的反应，除了96Zr的反应，它会发射核子和a粒子，这可以导致所研究的放射性核素的形成。该表还显示了这些反应的阈值能量。形成放射性核素的横截面（1 mb= 10-27 cm 2）与7-1线的光峰事件数N有关，由公式表示
In a continuation of previous investigations [1], we studied excitation functions for forming long-lived radionuclides by interacting protons with energies up to 70 MeV with a natural isotopic composition of zirconium. The experimental data are required to verify current theoretical models for 1) characteristics of nuclei at high excitation energies, 2) nuclear reaction mechanisms, and 3) the systematics of nuclear constants, which are required in activation analysis, designing shields, etc. Up to now, cross sections for forming radionuclides by irradiating zirconium with protons have been measured only for 9~[2, 3]. In order to study the possibilities of theoretically predicting excitation functions for nuclide formation, we performed computations on the Weisskopf--Ewing evaporation model [4] and on the geometrically dependent hybrid model for pre-equilibrium particle emission [5]. We then compared the calculated and experimental cross sections. Experiment. The cross sections for forming radionuclides were measured by the induced activation method as a function of the incident particle energy. The set of samples was irradiated with a proton beam with incident energies up to 70 MeV and a scatter of ___0. 5 MeV on the U-240 cyclotron at the IYaI AN USSR. The error in measuring the proton energy was 3 MeV. The irradiation time was 5 h at a beam current of 0.1/, A. The samples were 17 mg/cm 2 thick foils of natural zirconium (51.46% 90Zr, 11.23 91Zr, 17.11% 92Zr, 17.41% 94Zr, and 2.80% 98Zr). The absolute cross sections were determined by comparison with known cross sections of the reactions X7Al (p, 3pn) e4Na, Fe (ppm) 56Co, and Fe (p, 3pxn) 51Cr [1, 6, 7]. Therefore, besides zirconium, the set of samples included foils with natural isotopic compositions of aluminum and iron; the foil thicknesses were 15 and 55 mg/cm 2, respectively. The contribution of secondary neutrons and 7-quanta in the sample activity was determined to be negligibly small by including control foils in the sample sets. The induced activity of the samples was measured by Ge (Li) detectors with a volume of 100 cm 3 with an energy resolution of 2.8 keV for E},= 1332 keV (6~ A detailed description of the experimental method is given in [1]. The half lives of the radionuclides, the energy and quantum yield of the),-rays, which were used to determine the activity of these nuclides, are given in Table 1, which shows the reactions with threshold energies< 50 MeV for all isotopes, except those for 96Zr, which emit nucleons and a particles, which can lead to the formation of the investigated radionuclides. The table also shows the threshold energies for these reactions. The cross section or, rob,(1 mb= 10-27 cm 2) for forming a radionuclide is related to the number of events N in the photopeak of the 7-1ine by the formula