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首页> 外文学位 >Study of (178m2)hafnium(gamma, gamma')(178)hafnium reaction by nuclear spectroscopy methods.
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Study of (178m2)hafnium(gamma, gamma')(178)hafnium reaction by nuclear spectroscopy methods.

机译：（178m2）ha（γ，γ'）（178）reaction反应的核光谱法研究。

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Controlled release of the energy stored in nuclear isomers is very attractive for producing powerful sources of induced gamma-ray radiation. High-energy nuclear isomers can have very long lifetimes of the order of years and thus they can serve as good energy storage media. For instance, 1 mg of the 178m2Hf isomer stores about 1 MJ as excitation energy of the isomeric state. One of the most promising ways to release the energy stored in the isomeric state involves photonuclear reactions in the energy range of soft X-rays. Photons with energies lower than 20 keV can excite the 178m2Hf isomeric state to an intermediate level from which gamma transitions cascade to lower levels with a decay rate much faster than the rate of spontaneous decay of the isomeric state. In this work, the photoexcitation of 178m2Hf by (γ, γ ′) reactions at low energies was studied by nuclear spectroscopy methods. The experimental arrangement was based on the coincident detection of gamma photons with four large HPGe detectors. A bremsstrahlung X-ray generator was used as excitation source, which covered a continuous energy-range from 0 to 60 keV. The interpretation of the experimental results shows that the decay of the 178m2Hf isomer can be triggered by X-rays at a power on the order of only mW/cm 2. The analysis of the gamma-gamma coincidence data has revealed that during X-ray irradiations, a line of 129.5 keV was found in coincidence with the 213.4 keV ground state band (GSB) transition. The 129.5 keV line has not been previously observed and is not a known transition of the spontaneous decay of 178m2Hf. The 129.5 keV gamma transition must be a member of a sequence of gamma transitions that bypasses most of the normal decay cascade populated by spontaneous decay. This result leads to a deeper understanding of the (γ, γ ′) reactions at low energies. These photonuclear reactions are of special interest because of the importance of possible practical applications. The studies of the decay of nuclear isomers induced by X-rays should be seen in a larger perspective of the development of new controlled sources of incoherent gamma-radiation and they could also mean a significant progress for the development of a gamma-ray laser.
机译：受控释放储存在核异构体中的能量对于产生强大的诱发伽马射线辐射源非常有吸引力。高能核异构体的寿命可能长达数年之久，因此它们可以用作良好的储能介质。例如，1 mg 的 178m2 Hf异构体存储约1 MJ 作为异构体的激发能。释放以异构状态存储的能量的最有前途的方法之一是在软X射线能量范围内进行光核反应。能量低于 keV 的光子可以将 178m2 Hf异构体激发到一个中间能级，从该中间能级，伽马跃迁到更低能级，其衰变速率远快于异构状态的自发衰减。本文利用核能谱方法研究了低能（γ，γ'）反应对 178m2 Hf的光激发。实验安排基于与四个大型HPGe检测器同时检测伽马光子。使用致辐射X射线发生器作为激发源，其覆盖从0到60 keV 的连续能量范围。实验结果的解释表明， 178m2 Hf异构体的衰变可以由X射线以仅 mW / cm 的功率触发。 2 。对伽玛-伽玛符合数据的分析表明，在X射线照射期间，发现与123.4 keV 基态能带（GSB）吻合的谱线为129.5 keV ） 过渡。 129.5 keV 线以前未曾观察到，也不是 178m2 Hf自发衰减的已知转变。 129.5 keV 伽马跃迁必须是一系列伽马跃迁的成员，该序列绕过大多数由自然衰变构成的正常衰变级联。这一结果使人们对低能量下的（γ，γ'）反应有了更深入的了解。由于可能的实际应用的重要性，这些光核反应特别受关注。 X射线诱导的核异构体衰变的研究应该在开发新的非相干伽马射线辐射受控源的更大视野中进行，它们也可能意味着伽马射线激光器的发展取得重大进展。

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