Nuclear fusion driven by coulomb explosions of large deuterium clusters

Recent experiments on the interaction of intense, ultrafast laser pulses with large van der Waals bonded clusters have shown that these clusters can explode with substantial kinetic energy. By driving explosions in deuterium clusters with a 35 fs laser pulse, we have accelerated ions to sufficient kinetic energy to produce DD nuclear fusion. By diagnosing the fusion yield through measurements of 2.45 MeV fusion neutrons, we have found that the fusion yield from these exploding clusters varies strongly with the cluster size, consistent with acceleration of deuterons via Coulomb explosion forces.     

SILEX-I装置上激光-团簇聚变实验中子产额测量

 超短超强脉冲激光与CD4团簇相互作用可以产生高能量的氘离子,从而产生DD聚变中子,这种团簇聚变中子源有着非常广阔的应用前景。在SILEX-I 100 TW飞秒激光装置上,超短超强脉冲激光与CD₄团簇相互作用实现了DD核聚变。团簇聚变的中子产额是实验中最为重要的物理量,在实验中采用高灵敏的中子探测器对团簇聚变产生的中子进行了测量,在现有实验条件下测得中子产额为10³。     

超短脉冲强激光与团簇的相互作用

超短脉冲强激光与团簇的相互作用已被证明能够产生能量高达ＭｅＶ量级的高能离子和中子以及非常强的Ｘ射线辐射。广阔好原子团簇在超短脉冲强激光场的作用下的加热、电离和膨胀等机制,对这种相互作用的深入研究可能会对激光核聚变和Ｘ射线激光等应用领域产生重大影响。     

Nuclear fusion from Coulomb explosions of deuterated methane clusters subjected to ultraintense femtosecond laser pulses

This paper reports that Coulomb explosions taken place in the experiment of heteronuclear deuterated methane clusters ((CD₄)₂) in a gas jet subjected to intense femtosecond laser pulses (170mJ, 70fs) have led to table-top laser driven DD nuclear fusion. The clusters produced in supersonic expansion had an average size of about 5nm in radius and the laser intensity used was 3×10¹⁷W/cm².The measured maximum and average energies of deuterons produced in the laser--cluster interaction were 60 and 13.5keV, respectively. From DD collisions of energetic deuterons, a yield of 2.5(±0.4)×10⁴ fusion neutrons of 2.45MeV per shot was realized, giving rise to a neutron production efficiency of about 1.5×10⁵ per joule of incident laser pulse energy. Theoretical calculations were performed and a fairly good agreement of the calculated neutron yield with that obtained from the present experiment was found.     

利用超高能中子诊断惯性约束聚变的燃烧

惯性约束聚变靶丸中,高能中子相互之间发生碰撞将导致超高能中子的产生.本文讨论超高能中子产生与聚变燃烧速率的关系.数值模拟理想模型,分析超高能中子产生量与平均烧氚体积的关系,讨论利用出壳超高能中子流与烧氚量诊断二维效应和混合效应.进一步分析出壳超高能中子流与平均烧氚率的关系,探讨利用超高能中子诊断平均烧氚温度并判断是否发生非平衡效应问题.     

D-D neutron yield in the 125 J dense plasma focus Nanofocus

We present here a very small transportable dense plasma focus with 125 J of energy able to be used mainly as an intense fast neutron source. The aim of this work was to design, construct and experimentally study a very compact nuclear fusion apparatus, at the lower energy limit, useful for multiple applications, such as soil humidity measurements, inspection of several materials metallic inclusions, medical neutron-therapies, etc. Besides, the possibility of using the same device as X-rays emitter has been explored. In a narrow range of deuterium filling pressure around 1 mbar, peaked Rogowski dips are observed. Correspondingly, strong neutron and hard X-ray pulses are measured. The neutron pulses last, in average, 50 ns, being about 10⁶ the amount of neutrons per pulse. The performance of this device has shown to be higher than any other plasma focus apparatus, compar ed on the empirical scaling law of neutron yield vs. pinch current.Received: 29 April 2003, Published online: 5 August 2003PACS: 52.58.Lq Z-pinches, plasma focus and other pinch devices - 52.70.Ds Electric and magnetic measurements - 52.70.Nc Particle measurements     

High-intensity laser induced ion acceleration from heavy-water droplets

Fusion neutrons from a heavy water droplet target irradiated with laser pulses of 3 x 10(19) W/cm(2) and from a deuterated secondary target are observed by a time-of-flight (TOF) neutron spectrometer. The observed TOF spectrum can be explained by fusion of deuterium ions simultaneously originating from two different sources: ion acceleration in the laser focus by ponderomotively induced charge separation and target-normal sheath acceleration off the target rear surface. The experimental findings agree well with 3D particle-in-cell simulations.     

Search for neutrons from ‘cold nuclear fusion’

We have searched for neutrons from a Pd-electrode loaded with deuterium in electrolysis setups similar to those of Fleischmann and Pons [1] and Jones et al. [2]. Within the sensitivity of our neutron detection system corresponding to a neutron source strength of 5 x 10^{? 2} neutrons/s we did not find any neutrons due to ‘cold nuclear fusion’. We emphasize the necessity of using several independent neutron detectors.     

台面激光核聚变中子源研究进展

通过超短脉冲激光与合适的介质相互作用,在普通光学实验室中可以产生聚变中子,经过特殊设计的固体靶结构和特殊安排的级联过程,亚ＴＷ激光即可引发光核反应产生中子,通过台面超强激光与固体靶相互作用利用对离子的自导通道径向加速机制,可获得较多的高能离子和较多的中子产率,由于超强激光辐照下大的团簇爆炸时可获得大量高能离子,团簇靶实验中实现的中子产率比相似激光能量的固体靶实验高两个量级,文章讨论了上述三种产生中     

A femtosecond neutron source

The possibility of using the ultrashort ion bunches produced by circularly polarized laser pulses to drive a source of fusion neutrons with sub-optical cycle duration is discussed. A two-sided irradiation of a deuterated thin foil target produces two counter-moving ion bunches, whose collision produces an ultrashort neutron burst. Using particle-in-cell simulations and analytical modeling, it is calculated that, for intensities of a few 10¹⁹ W cm^-2, more than 10³ neutrons per Joule may be producedwithin a time shorter than one femtosecond. Another scheme based on a layered deuterium-tritium target is outlined. PACS 24.90.+d; 29.25.Dz; 52.38.ph; 52.50.Jm     

Neutron emission under particular nonequilibrium conditions from Pd and Ti electrolytically charged with deuterium

Summary We report on neutron emission in palladium and titanium electrolitically charged with deuterium. The detection of neutrons is observed after thermal treatment of the electrode. In the hypothesis that neutrons came from cold fusion processes, we estimate a fusion rate as high as 1.3·10⁻²¹ fusions/deuteron pair/second.     

Radiation effect of neutrons produced by D–D side reactions on a D–3He fusion reactor

One of the most important characteristics in D–³He fusion reactors is neutron production via D–D side reactions. The neutrons can activate structural material, degrading them and ultimately converting them into high-level radioactive waste, while it is really costly and difficult to remove them. The neutrons from a fusion reactor could also be used to make weapons-grade nuclear material, rendering such types of fusion reactors a serious proliferation hazard. A related problem is the presence of radioactive elements such as tritium in D–³He plasma, either as fuel for or as products of the nuclear reactions; substantial quantities of radioactive elements would not only pose a general health risk, but tritium in particular would also be another proliferation hazard. The problems of neutron radiation and radioactive element production are especially interconnected because both would result from the D–D side reaction. Therefore, the presentation approach for reducing neutrons via D–D nuclear side reactions in a D–³He fusion reactor is very important. For doing this research, energy losses and neutron power fraction in D–³He fusion reactors are investigated. Calculations show neutrons produced by the D–D nuclear side reaction could be reduced by changing to a more ³He-rich fuel mixture, but then the bremsstrahlung power loss fraction would increase in the D–³He fusion reactor.     

Deuterium-deuterium fusion dynamics in low-density molecular-cluster jets irradiated by intense ultrafast laser pulses

Following the interaction of superintense, short pulse lasers and plasmas, ions can be accelerated to velocities sufficient to drive nuclear fusion reactions, in particular, by the process of Coulomb explosion of clusters [T. Ditmire, Nature (London) 398, 491 (1999)]]. We show here how short bursts of neutrons can be produced using a jet of low-density deuterated methane clusters. Ion velocity distributions were simultaneously measured by a Thomson parabola mass spectrometer, demonstrating deuteron energies up to 120 keV. We show that, in such conditions, nuclear fusion will occur not only in the hot plasma core, but also in the cold outer region by collision processes.     

Correlation of x-ray and neutron emissions from an ion implosion system

The paper presents the results of space- and time-resolved studies of X-rays and neutrons emitted by the SOWA-150A ion-impulsion facility equipped with a coaxial set multi-rod electrodes. Proportionality and correlation of neutron and hard X-ray pulses favour the hypothesis of a beam-target mechanism of the neutron production.     

HL－1M中的聚变中子产额

本文概算了在欧姆加热、波加热和中性束注入条件下，ＨＬ－１Ｍ托卡马克等离子体的聚变中子产额、中子通量，以及相关的电离率、电荷交换率及快离子的空间分布。计算结果为发展下一代聚变中子探测系统和进行中子辐射的环境评估提供了依据。     

Effect of positive Q-value neutron transfers on sub-barrier fusion reactions

The role of positive Q-value neutron transfers in sub-barrier fusion reactions has been studied with a modified quantum coupled channels model with all order couplings(CCFULL model). Neutron rearrangement related only to the dynamical matching condition with no free parameters is implemented in the model, which provides a way to understand especially the Q-value dependence of sub-barrier fusion reactions. The fusion cross sections of the collision systems ~(40)Ca+~(94,96)Zr have been calculated and analyzed. The general trend of experimental data can be reproduced well with additional channels for neutron rearrangement. We find that enhancement of sub-barrier fusion cross sections is closely related to the Q-value of the transferred neutrons, in particular for channels with sequential even number transferred neutrons.     

高灵敏度的快中子照相系统

快中子照相系统由闪烁光纤阵列和科学级可见光CCD等元件组成. 14 MeVD-T聚变中子在穿透样品后进入50 mm×50 mm闪烁光纤阵列，中子辐射转换为中心波长496 nm的绿光. 光纤阵列长100 mm，光纤截面500 μm×500 μm，100×100根闪烁体光纤组成阵列. 阵列对14 MeV中子探测效率经估算可达21.4%. CCD与光纤阵列之间采用反射镜和透镜耦合方式，使CCD避开中子源直接辐照. 综合考虑光纤尺寸、CCD记录噪声及中子源与受照样品几何关系等因素，理论上系统可获得整体分辨率1.5 mm的中子图像. 在K400直流加速器中子源上进行了初步实验，获得了中子图像.     

Neutron star matter at sub-nuclear densities

An extremely simple form for the energy density of a nuclear many-body system derived from the two-body nucleon-nucleon interaction is used to determine the ground state configuration of matter at sub-nuclear density. As the baryon density is increased, nuclei become progressively more neutron rich until neutrons eventually escape, yielding a Coulomb lattice of bound neutron and proton clusters surrounded by a dilute neutron gas. The clusters enlarge and the lattice constant decreases with increasing density, approaching a completely uniform state near nuclear density.     

Absence of neutron emission during interaction of deuterium with metal at low energies

Technique and instrumentation to detect reliably, multiplicity of neutrons emitted in sharp bursts (≤100 μs) has been developed where a burst of as low as 15 neutrons and continuous emission of ⋍10⁻¹ neutron/s may be detected. Using this technique, attempts were made to detect neutron emission from various experiments in which anomalous nuclear effects (or what is commonly referred to as cold fusion) may be expected to occur. No neutrons, above our detection threshold, were detected in the recent series of experiments.