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61.
Malcolm H. Mac Gregor 《Foundations of Physics Letters》2004,17(4):381-391
Quantum Hall plateaus are entered via quantized cyclotron (QC) cloud-chamber orbits that have Landau-level (LL) energies and uniquely-defined angular momenta. The conservation of angular momentum in the quantum Hall system requires both canonical and magnetic angular momentum components, which add together to form the invariant kinematic angular momentum. The only LL radial eigenfunctions that satisfy the conservation-law requirements of the QC to LL transition are the u
n,l eigenstates u
n,2n+1, where n = 0, 1, 2, .... These same eigenstates uniquely have the correct scaled sizes to tile the observed families of = 1/(2n + 1) Hall plateaus. Quantum Hall plateau formation is a direct consequence of this tiling. 相似文献
62.
Paul Francis Bracken 《International Journal of Theoretical Physics》2007,46(1):116-129
The problem of studying the quantum Hall effect on manifolds with non constant metric is addressed. The Hamiltonian on a space
with hyperbolic metric is determined, and the spectrum and eigenfunctions are calculated in closed form. The hyperbolic disk
is also considered and some other applications of this approach are discussed as well.
PACS numbers: 73.43.-f, 02.30.Jr. 相似文献
63.
The paper discusses the basic design of the critical facility, whose main purpose is the physics validation of AHWR. Apart
from moderator level control, the facility will have shutdown systems based on shutoff rods and multiple ranges of neutron
detection systems. In addition, it will have a flux mapping system based on 25 fission chambers, distributed in the core.
We are planning to use this reactor for experiments with a suitable source to simulate an ADS system. Any desired sub-criticality
can be achieved by adjusting the moderator level. Apart from perfecting our experimental techniques, in simple configurations,
we intend to study the one-way coupled core in this facility. Preliminary calculations, employing a Monte Carlo code TRIPOLI,
are presented.
相似文献
64.
182Hf的半衰期为(8.90±0.09)Ma, 是一个接近灭绝的放射性核素. 超新星爆炸是自然界中已知的惟一能产生182Hf的途径. 因此182Hf是研究近1亿年来在地球附近可能发生的超新星事件的理想核素. 另外, 182Hf是核工程中特别感兴趣的一个长寿命放射性核素. 精确测量超痕量的182Hf对反应堆的设计和核天体物理学以及其他研究领域都是非常重要的. 用加速器质谱有可能实现对超低含量182Hf的测量. 在中国原子能科学研究院的HI-13加速器质谱装置上对182Hf的测量方法以及样品的化学去钨方法进行了研究, 分别得到了空白样品以及系列标准样品的182Hf和183W的能量-飞行时间双维谱. 182W对182Hf计数的贡献是通过测量183W的计数归一扣除的. 目前本工作对182Hf的测量灵敏度为4.15±10-11 (182Hf/180Hf比值). 相似文献
65.
采用多晶LaB6材料制成平板二极管阴极,阳极采用钼材料,阴极采用热传导与热辐射加热,加热体为石墨。实验研究了不同阴极温度、不同真空度下的脉冲发射特性,并对热发射稳定性进行了分析。结果表明: 在动态真空系统中, 阴极发射面积为0.012 1 cm2, 工作真空度为2×10-4 Pa, 阴极温度分别为1 600, 1 650和1 700 ℃,在脉冲宽度为40 ms、重复频率为107 Hz的条件下,最大脉冲发射电流密度分别为34.0,44.0和53.8 A/cm2; 2×10-4,5×10-4和2×10-3 Pa压强下的发射能力没有明显的差异;脉冲宽度的变化不影响发射电流密度的变化。 相似文献
66.
J. Adam K. Katovsky A. Balabekyan V. G. Kalinnikov M. I. Krivopustov H. Kumawat A. A. Solnyshkin V. I. Stegailov S. G. Stetsenko V. M. Tsoupko-Sitnikov W. Westmeier 《Pramana》2007,68(2):201-212
Target-blanket facility ‘Energy + Transmutation’ was irradiated by proton beam extracted from the Nuclotron Accelerator in
Laboratory of High Energies of Joint Institute for Nuclear Research in Dubna, Russia. Neutrons generated by the spallation
reactions of 0.7, 1.0, 1.5 and 2 GeV protons and lead target interact with subcritical uranium blanket. In the neutron field
outside the blanket, radioactive iodine, neptunium, plutonium and americium samples were irradiated and transmutation reaction
yields (residual nuclei production yields) have been determined using γ-spectroscopy. Neutron field's energy distribution
has also been studied using a set of threshold detectors. Results of transmutation studies of 129I, 237Np, 238Pu, 239Pu and 241Am are presented.
相似文献
67.
V. Wagner A. Krása M. Majerle F. Křížek O. Svoboda A. Kugler J. Adam V. M. Tsoupko-Sitnikov M. I. Krivopustov I. V. Zhuk W. Westmeier 《Pramana》2007,68(2):297-306
The set-up ‘energy plus transmutation’, consisting of a thick lead target and a natural uranium blanket, was irradiated by
relativistic proton beams with the energy from 0.7 GeV up to 2 GeV. Neutron field was measured in different places of this
set-up using different activation detectors. The possibilities of using the obtained data for benchmark studies are analyzed
in this paper. Uncertainties of experimental data are shown and discussed. The experimental data are compared with results
of simulation with MCNPX code.
相似文献
68.
J. Blomgren 《Pramana》2007,68(2):269-278
One of the outstanding new developments in the field of partitioning and transmutation (P&T) concerns accelerator-driven systems
(ADS) which consist of a combination of a high-power, high-energy accelerator, a spallation target for neutron production
and a sub-critical reactor core. The development of the commercial critical reactors of today motivated a large effort on
nuclear data up to about 20 MeV, and presently several million data points can be found in various data libraries. At higher
energies, data are scarce or even non-existent. With the development of nuclear techniques based on neutrons at higher energies,
nowadays there is a need also for higher-energy nuclear data. To provide alternative to this lack of data, a wide program
on neutron-induced data related to ADS for P&T is running at the 20–180 MeV neutron beam facility at ‘The Svedberg Laboratory’
(TSL), Uppsala. The programme encompasses studies of elastic scattering, inelastic neutron production, i.e., (n, xn′) reactions, light-ion production, fission and production of heavy residues. Recent results are presented and future program
of development is outlined.
相似文献
69.
Gun Sang Jeon Chia-Chen Chang Jainendra K. Jain 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(3):271-282
We review and extend the composite fermion theory for semiconductor quantum dots in high magnetic fields. The mean-field model
of composite fermions is unsatisfactory for the qualitative physics at high angular momenta.
Extensive numerical calculations demonstrate that the microscopic CF theory,
which incorporates interactions between composite fermions, provides an excellent qualitative and quantitative account
of the quantum dot ground state down to the largest angular momenta studied,
and allows systematic improvements by inclusion of mixing between composite
fermion Landau levels (called Λ levels). 相似文献
70.
Roland Wittje 《Physics in Perspective (PIP)》2007,9(4):406-433
In the late 1940s and the 1950s, Norwegian nuclear scientists, engineers, and administrators were deeply split over their
nation’s goals, organization, politics, and tools for research in nuclear physics. One faction was determined to build a nuclear
reactor in Norway, while another fiercely opposed the reactor plans and focused on particle accelerators. The first faction
comprised scientific entrepreneurs and research technologists, the second academic scientists, most of whom began their research
careers in nuclear physics in the 1930s. To understand this conflict, I trace the development of nuclear research in Norway
from the early 1930s to the mid-1950s, placing it within an international context.
Roland Wittje is working on his habilitation thesis in the History of Science Unit at the University of Regensburg, Germany. 相似文献