Nuclear Physics Rolling Grant

核物理滚动资助

• 批准号: ST/F012055/1
• 负责人: Robert Wadsworth
• 金额: $ 177.42万
• 依托单位: University of York
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2008
• 资助国家: 英国
• 起止时间: 2008 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FF012055%2F1
• 关键词: Nuclear; Physics; Rolling; Grant

All of the matter around us originates utimately from the Big Bang, yet the Big Bang produces only the lightest chemical elements, hydrogen, helium and lithium. This begs the question where and how the other chemical elements are produced. In fact, Nuclear Physics underpins the processes that are responsible for transforming the lightest elements into the distribution of elements up to element 92 (uranium) which we see around us. Much of this processing is carried out in stars but to produce the very heaviest elements, and reproduce the known abundances of the elements, it is clear that much more extreme conditions of temperature, density and pressure are required. The most dramatic of these is the supernova where a dying star blows itself apart, but also important are phenomena such as novae where a star which has exhausted all its nuclear fuel (a white dwarf) suddenly flares up violently after stealing material from a neighbouring star in a binary system. Our research looks into the details of the Nuclear Physics at work in these explosive objects to understand which elements are produced as well as the energy generated. It turns out that even though such processes are highly complex and involve a huge number of possible nuclear reactions, it is only a small subset of these which impact on the final results. A focused research programme is therefore possible but many of the isotopes we need to study do not exist on earth and have to be produced as a radioactive beam in the laboratory. The question of what elements and isotopes can be generated by astrophysical processes is intimately related to the limits of nuclear existence - how many protons and neutrons can be added to a nuclear system before it falls apart? Our research focuses on nuclei on the so-called proton dripline - the limit where adding a further proton is not possible and the nucleus breaks up. This dripline lies very close to the line of nuclei with equal numbers of protons and neutrons (N=Z); such nuclei have special properties by virtue of this symmetry. Moreover, the nuclear force does not discriminate between protons and neutrons - the basic building blocks, and there are important consequences stemming from this. For example, so-called mirror nuclei which are the same under interchange of the number of protons and neutrons have near identical properties; it is the subtle differences, however, that tell us profound details of the balance of nuclear forces. Our research investigates these effects in detail and feeds back this knowledge into our understanding of stellar explosions. As well as the action of individual protons and neutrons, the overall behaviour of the atomic nucleus often reflects the result of the the protons and neutrons in the nucleus acting collectively. This collective behaviour can manifest itself as vibrations or rotations the nucleus. Rotational behaviour is ordinarily associated with a deformed nuclear shape, the commonest being prolate-deformed (rugby-ball shaped) and oblate-deformed (Smartie shaped). One of the striking properties of some atomic nuclei is their ambiguity with respect to which shape or configuration they chose to adopt. Adding a very small amount of extra energy to the nuclear system relative to the energy stored in the nucleus (which can be released, for example, through fission - E=mc^2) can prompt the nucleus to change from a spherical to a prolate or oblate shape, or vice versa. This phenomenon known as shape coexistence is highly sensitive to the properties of the individual nucleus concerned and is notoriously difficult for theoretical models to anticipate. Studying shape coexistence in nuclei therefore provides a strong challenge to our theoretical understanding of the nucleus. Naturally, a good understanding of nuclear properties underpins all aspects of Nuclear Physics discussed above. Shape coexistence therefore forms the third strand of our research programme.

我们周围的所有物质都起源于大爆炸，然而大爆炸只产生最轻的化学元素，氢、氦和锂。这就回避了其他化学元素是在哪里以及如何产生的问题。事实上，核物理支持了将最轻的元素转化为元素分布的过程，直到我们周围看到的92号元素(铀)。这种处理大部分是在恒星中进行的，但要产生非常重的元素，并重现已知的元素丰度，显然需要更极端的温度、密度和压力条件。其中最具戏剧性的是一颗垂死的恒星将自己炸成碎片的超新星，但也有一些重要的现象，比如新星：一颗耗尽了所有核燃料的恒星(白矮星)在从双星系统中的相邻恒星那里窃取物质后突然猛烈地爆发。我们的研究着眼于这些爆炸性物体中起作用的核物理的细节，以了解产生了哪些元素以及产生的能量。事实证明，尽管这样的过程非常复杂，涉及大量可能的核反应，但影响最终结果的只是这些反应中的一小部分。因此，一个有重点的研究方案是可能的，但我们需要研究的许多同位素在地球上并不存在，必须在实验室中作为放射性束流生产。天体物理过程可以产生哪些元素和同位素的问题与核存在的限度密切相关--在一个核系统解体之前，可以向它添加多少质子和中子？我们的研究集中在所谓的质子滴线上的原子核--在这个极限上，不可能再添加一个质子，原子核就会分裂。这条滴线非常接近具有相同数目的质子和中子(N=Z)的原子核的直线；由于这种对称性，这种原子核具有特殊的性质。此外，核力量不区分质子和中子--它们是基本的组成部分，由此产生了重要的后果。例如，在质子和中子数目互换下相同的所谓镜像核具有几乎相同的性质；然而，正是这些细微的差异告诉我们核力平衡的深刻细节。我们的研究详细地研究了这些影响，并将这些知识反馈到我们对恒星爆炸的理解中。除了单个质子和中子的作用外，原子核的整体行为往往反映了原子核中质子和中子共同作用的结果。这种集体行为可以表现为原子核的振动或旋转.旋转行为通常与变形的核形状有关，最常见的是扁平变形(橄榄球形状)和扁平变形(Smartie形状)。一些原子核的显著性质之一是它们对于选择采用哪种形状或构型的模棱两可。相对于储存在核中的能量，向核系统添加非常少量的额外能量(例如，可以通过裂变-E=mc^2释放)可以促使核从球形变成长圆形或扁圆形，反之亦然。这种被称为形状共存的现象对单个原子核的性质高度敏感，而且众所周知，理论模型很难预测到这种现象。因此，研究原子核中的形状共存对我们对原子核的理论理解提出了强有力的挑战。当然，对核性质的良好理解是上面讨论的核物理的所有方面的基础。因此，形状共存构成了我们研究计划的第三条线索。

项目成果

Direct measurement of the F 18 ( p , a ) O 15 reaction at nova temperatures

直接测量新星温度下的 F 18 ( p , a ) O 15 反应

• DOI: 10.1103/physrevc.83.042801
• 发表时间: 2011
• 期刊: Physical Review C
• 影响因子: 3.1
• 作者: Beer C

Isobaric Analogue States Studied in Mirrored Fragmentation and Knockout Reactions

• DOI: 10.1142/s0217732310000575
• 发表时间: 2010-07
• 期刊: Modern Physics Letters A
• 影响因子: 1.4
• 作者: M. Bentley;I. Paterson;J. Brown;M. Taylor;C. Diget;P. Adrich;D. Bazin;J. Cook;A. Gade;T. Glasmacher;S. Mcdaniel;A. Ratkiewicz;K. Siwek;D. Weisshaar;B. Pritychencko;S. Lenzi

Isomeric mirror states as probes for effective charges in the lower pf shell

• DOI: 10.1088/0954-3899/38/3/035104
• 发表时间: 2011-03
• 期刊: Journal of Physics G
• 作者: R. Hoischen;D. Rudolph;H. L. Ma;P. Montuenga;M. Hellström;S. Pietri;Z. Podolyák;P. Regan;A. Garnsworthy;S. Steer;F. Becker;P. Bednarczyk;L. Caceres;P. Doornenbal;J. Gerl;M. Gorska;J. Gr;ebosz;I. Kojouharov;N. Kurz;W. Prokopowicz;H. Schaffner;H. Wollersheim;L. Andersson;L. Atanasova;D. Balabanski;M. Bentley;A. Blazhev;C. Brandau;J. Brown;C. Fahlander;E. Johansson;A. Jungclaus

Evaluation of charge breeding options for EURISOL

EURISOL 电荷育种方案评估

• DOI: 10.1140/epja/i2010-11042-9
• 发表时间: 2010
• 期刊: The European Physical Journal A
• 作者: Delahaye P

Low energy measurement of the 18F(p,a)15O cross section at TRIUMF

TRIUMF 18F(p,a)15O 截面的低能测量

• 发表时间: 2008
• 期刊: Proceedings of Science
• 作者: Beer C.E.