Tritium implantation and depth profiling in fusion related materials

Tritium behaviour in solids and particularly its permeation and inventory in the first wall, limiters, breeding blanket materials and in other structural elements of fusion reactors is a subject of great concern in all projects aiming at D + T fusion. In the present work elastic recoil detection (ERD) under ⁴He bombardment and the T(d, α)n nuclear reaction analysis (NRA) in the forward detection geometry were applied to the depth profiling of tritium at submicron distances below the surface of selected fusion related materials. Experimental results obtained for tritium implanted in titanium, graphite and lithium aluminate LiAlO₂ are presented as the examples.     

Studies on p+6Li Fusion Reaction using 3-Parameter Model

The 3-parameter model introduces 3 parameters (radius of a square nuclear potential well, the real part and the imaginary part of the nuclear potential depth) to describe the low energy behavior of the fusion cross-section for light nuclei. It has been justified by the experimental data from the National Nuclear Data Center (NNDC) for 3 major fusion reactions (d?+?T, d?+?D, and d?+?³He). In the present paper this 3-parameter model has been extended to p+⁶Li fusion reaction. It agrees with the fusion cross-section data from NNDC again. Moreover it is able to calculate the astrophysical S-factor with an electron screening potential for p+⁶Li fusion reaction as well. As a development of the 3-parameter model, the necessary condition for a low energy resonant tunneling through Coulomb barrier is derived. It reveals further the possibility of resonant tunneling at very low energy for p+⁶Li system.     

High energy primary knock-on process in metal-deuterium systems initiated by bombardment with noble gas ions

An experimental study confirms the possibility of nuclear fusion reactions initiating in metal-deuterium targets by bombarding them with ions that are not the reagents of the fusion reaction, in particular, with noble gas ions. The yields of (d,d) and (d,t) reactions were measured as functions of energy (0.4-3.2 MeV) and mass of incident ions (He⁺, Ne⁺, Ar⁺, Kr⁺ and Xe⁺). Irradiation by heavy ions produced a number of energetic deuterium atoms in the deuteride and deuterium + tritium metal targets. At ion energies of ∼0.1-1 MeV the d-d reaction yields are relatively high. A model of nuclear fusion reaction cross-sections in atomic collision cascades initiated by noble gas ion beam in metal-deuterium target is developed. The method for calculation tritium or deuterium recoil fluxes and the yield of d-d fusion reaction in subsequent collisions was proposed. It was shown that D(d,p)t and D(t,n)⁴He reactions mainly occur in energy region of the recoiled D-atom from 10 keV to 250 keV. The calculated probabilities of d-d and d-t fusion reactions were found to be in a good agreement with the experimental data.     

天体物理重要反应13N(p,γ)14O的实验研究

¹³N(p,γ)¹⁴O是高温CNO循环中的关键反应,对恒星能量产生机制及其演化的研究具有重要意义。利用北京HI-13串列加速器次级束流线产生的13N放射性束测量了质心系能量为8.9MeV的¹³N(d,n)¹⁴O反应的角分布,导出了¹⁴O基态渐进归一化系数（ANC）为(29.4±5.3)fm^-1。此外,使用镜像核的电荷对称性,通过分析¹³C(d,p)¹⁴C反应的角分布,导出了与实验一致的¹⁴O基态质子ANC。使用最新开发出的R矩阵程序,导出¹³N(p,γ)¹⁴O反应在高温CNO循环中的天体物理S因子和反应率。将此数据代入核天体物理反应的网络程序进行计算,结果表明,新星中CNO循环产生的能量比原有的结果多5%,这可能会对新星的演化有一定的影响。     

A Monte-Carlo simulation program of nuclear reaction analysis spectrum

A Monte-Carlo simulation program NRIBA of charged particle spectrum from nuclear reaction in solid is presented. The slowdown process of projectile and nuclear reaction procedure are separated in order to improve the simulation speed. The simulated energy spectra of transmitted ⁴He ions are comparable to that calculated from SRIM-2010. This program could fit previous experimental result very well. By this program, the asymmetry proton spectra of low energy D(d,p)T reaction with a high energy tail induced by multi-scattering effect is discussed.     

氘-氘聚变反应高能γ射线产额的实验研究

本文对低能D(d,γ)⁴He聚变反应进行了实验研究。由于D(d,γ)⁴He聚变反应γ射线的产额低、能量高、本底大,实验采用大NaI-塑料闪烁体反康谱仪,以提高探测效率并降低宇宙线的影响;采用脉冲束飞行时间方法区分中子和γ射线,以减小中子和宇宙线本底的影响。实验测量了300 keV d束轰击厚D靶和薄D靶两种情况下的γ数据。在计算反应产生23.8 MeV的高能γ峰面积时,采用了拟合法扣除本底。实验测得,对厚靶,D(d,γ)⁴He反应截面为2.47×10^-37m²;对薄靶,D(d,γ)⁴He反应截面为4.36×10^-37m²。     

Preliminary study of high neutron flux fusion heating

A heating scheme for nuclear fusion is proposed based on the availability of a high flux, low energy neutron source. The heat is derived in the reaction ⁶Li (n, T) ⁴He resulting from the incidence of a low energy neutron beam on a sample of ⁶Li D. The energy release per reaction, Q = 4.6 MeV, is converted through electron Coulomb collisions thereby quickly dissociating the solid sample to the plasma state. For 10⁻³ eV neutrons it is estimated that this dissociation occurs in 7 ms for an incident flux of 10¹⁷ cm⁻² · s⁻¹. The possibility of further driving the heated fuel to fusion is also discussed.     

^197Au束轰击TiD靶引起的D—D熔合研究

测量了能量范围从１．０ＭｅＶ到５．２ＭｅＶ的＾１９７Ａｕ束轰击ＴｉＤ靶引发的Ｄ（ｄ，ｐ）Ｔ反应的质子产额曲线，为了对其进行解释，根据两步级联磁撞模型的框架编写的ＴＳＣＣＦＣ程序进行了相应的计算，发现计算结果与结果在误差范围内能较好地符合。     

Nova target physics program and the Nova upgrade laser

Summary Recent advances in ICF target design and performance have made possible the achievement of ignition and gain with 1–2 MJ laser drive energy, as against the 5–10 MJ necessary to achieve high gain in the earlier designs. Ignition and propagating burn can be achieved at the lower energy by increasing the hohlraum temperature and, thereby increasing the pressure driving the imploding fusion capsule. Nova experiments continue to address the target physics of radiatively driven targets, such as laser-plasma interaction physics, the efficiency of laser light conversion to X-rays, hohlraum characterization and design, hydrodynamic stability, and implosion physics. Recent experiments on Nova have also demonstrated 1.3 times higher hohlraum temperature than previously predicted. This latter demonstration is the key achievement leading to the Nova Upgrade proposal. These combined results, together with those from experiments to study the interaction of high-power laser light with target plasmas, indicate that the capsule drive and symmetry conditions required for ignition and net gain can be achieved with a properly designed upgrade of the existing Nova facility.Success in the Nova Upgrade objective would firmly establish target and driver requirements for achieving high yield and high gain and would support a decision to construct a Laboratory Microfusion Facility (LMF) for defense applications and an Engineering Test Facility (ETF) for energy applications by the end of the first decade of the next century. Nova Upgrade experiments would focus on the target physics necessary to determine the minimum driver energy required to achieve ignition and high-gain laser fusion. The thermonuclear yield produced (up to 20 MJ) would be used to study the effects of fusion microexplosions on potential LMF and ETF reactor chamber materials. This information would permit development of the most efficient and least costly designs for the LMF and the ETF.In collaboration with W. H. Lowdermilk, N. Frank, C. D. Henning, John R. Murray, M. T. Tobin, J. R. Smith, E. K. Storm, J. D. Lindl, J. D. Kilkenny, J. T. Hunt, and J.B. Trenholme.     

Determination of the concentrations of tritium and helium in titanium tritide targets

Atom ratios of T to Ti in T-Ti targets have been determined by the ⁴He⁺ Rutherford backscattering (RBS) and the proton elastic scattering (PES) techniques, and that of ³He to T in aged T-Ti targets by the ³He(d, p)⁴He and T(d, n)⁴He reactions. The results from RBS show that the depth distribution of T is uniform in a region of 8000 Å under the target surface. For the results from the nuclear reaction analysis (NRA), a discrepancy between the experimentally measured and the calculated concentration of ³He in a heavily bombarded T-Ti target obviously exists.     

Retention and surface blistering of helium irradiated tungsten as a first wall material

The first wall of an inertial fusion energy reactor may suffer from surface blistering and exfoliation due to helium ion irradiation and extreme temperatures. Tungsten is a candidate for the first wall material. A study of helium retention and surface blistering with regard to helium dose, temperature, pulsed implantation, and tungsten microstructure was conducted to better understand what may occur at the first wall of the reactor. Single crystal and polycrystalline tungsten samples were implanted with 1.3 MeV ³He in doses ranging from 10¹⁹ m⁻² to 10²² m⁻². Implanted samples were analyzed by ³He(d,p)⁴He nuclear reaction analysis and ³He(n,p)T neutron depth profiling techniques. Surface blistering was observed for doses greater than 10²¹ He/m². For He fluences of 5 × 10²⁰ He/m², similar retention levels in both microstructures resulted without blistering. Implantation and flash heating in cycles indicated that helium retention was mitigated with decreasing He dose per cycle.     

New cold nuclear fusion theory and experimental tests

A theory of neutron-induced tritium-deuterium fusion at room temperature is developed, based entirely on previously measured cross-sections of known nuclear reactions. The fusion process involves self-sustaining chain reactions: (1)n+⁶Li ⁴He+T and/orn+⁷Li⁴He+T+n, and (2) T+D ⁴He+n, in Li-D plasma or pellet surrounded by Li and other blankets and by neutron reflectors. The recent results of cold deuterium fusion reported by Fleischmann, Pons, and Hawkins are described in terms of this fusion process. Experimental evidence and tests of the chain reaction hypothesis are described.     

Fusion Energy Without Strong Nuclear Radiation

Conventional quantum mechanics calculation shows that fusion energy without strong nuclear radiation is feasible, because this is the nature of sub-barrier nuclear fusion. When the Coulomb barrier is relatively thin and low, the resonant tunneling would select the fusion reaction with strong neutron and Gamma radiation. On the other hand, if the Coulomb barrier is thick and high, the resonant tunneling would select the fusion reaction without strong neutron and Gamma radiation. Thus, fusion energy with lowest radiation is predictable in terms of d + t fusion data. This is the harmony between various approaches towards fusion energy. What we lose is the assumption of compound nucleus model for light nuclei fusion, and what we gain is the fusion energy without strong neutron and Gamma radiation.     

Ti-T靶中~3He测量

一、引言轻元素在材料中的含量及分布情况,是应用物理、应用技术等领域感兴趣的问题。目前,国外正在用各种核技术对此进行测量和研究。通常使用的Ti-T靶,因T的β衰变(T_(1/2)为12.33a),靶内~3He的含量将随制成靶的时间不同而变化。本文试图通过对不同时间制备的Ti-T靶中~3He的测量,探索测量和分析~3He的某种途径。     

铁屏蔽T（d,n）^4He源的模拟结果分析

用Ｍｏｎｔｅ Ｃａｒｌｏ法模拟了用铁屏蔽Ｔ（ｄ，ｎ）＾４Ｈｅ快中子源时不同条件下的透射率随铁厚度的变化规律。研究了（ｎ，２ｎ）反应对快中子慢化的作用，使较低能量的中子产生了累积效应，并分析了反射中子二次进入屏蔽体时透射率的变化规律。推荐了多层屏蔽体的铁的适当厚度，与国外数据符合较好。     

3 MeV中子诱发裂变测定铀同位素丰度

铀同位素丰度分析是核燃料循环中重要的分析项目。本工作研究了以D(d,n)³He反应产生的能量约为3 MeV的中子为源诱发裂变测定铀同位素丰度,并与以T(d,n)⁴He反应产生的14 MeV快中子为源的方法进行了比较,结果表明两种方法分析结果基本一致。     

Deuteron tunneling at electron-volt energies

We speculate on a new mechanism for deuteron-deuteron fusion reactions at electron-volt energies. Appealing to conservation principles, it is shown that deuteron tunneling leading to fusion is very unlikely to take place between two isolated deuterons. It is argued that in solids, however, tunneling may lead to fusion via a new reaction mechanism which populates energy levels of⁴He, with simultaneous energy transfer to an electron. Predictions of this theory are that d+d+e^– fusion at electron-volt energies in solids should lead to copious production of tritium, protium, energetic electrons, and small quantities of⁴He.     

Depth distribution profiling of deuterium and 3He

A technique using nuclear microanalysis has been developed to determine ²D an ³He concentrations versus depth profiles in the near surface regions (～2 μm) of solids. Ultimate near-surface depth resolutions of (≈100 Å) should be attainable by these techniques. A probing beam of ³He ions is used to analyze for the deuterium. By energy analyzing the emitted ⁴He ions from the reaction d(³He,p)⁴He and by simple computer analysis, deuterium concentration versus depth profiles are obtained. The same methods are applicable for ³He profiling except in that case a ²D probing beam is used. The techniques is currently being developed using Er hydride and Sc hydride films. It is particularly suited for the study of the transition metals with high hydrogen solubility such as Nb and V which are of interest for CTR reactor applications.     

Comparison of Level Density Models for the <Superscript>60,61,62,64</Superscript>Ni(p,n) Reactions of Structural Fusion Material Nickel from Threshold to 30 MeV

The knowledge of level density for reaction cross-section calculations are needed for various applications such as fission and fusion reactor design, accelerator driven sub-critical systems, nuclear medicine, neutron capture and astrophysics. In this study, the excitation functions for (p, n) reactions from reaction threshold to 30 MeV proton incident energy on ⁶⁰Ni, ⁶¹Ni, ⁶²Ni and ⁶⁴Ni isotopes were calculated using TALYS 1.6 nuclear code involving the level density models. This is of importance to the validation of nuclear model approaches with increased predictive power. There are several models of level density that can be used to predict cross-section. In this work, the (p, n) cross-sections would be calculated using three different model of level density, such as constant temperature model, back-shifted fermi gas model and generalized superfluid model on ^60,61,62,64Ni reactions. The (p, n) reaction cross-section calculations for ^60,61,62,64Ni target nuclei were compared with each other and the experimental nuclear reaction data obtained from EXFOR database.     

离子源及厚靶参数对氘氚反应中子源中子产额的影响

用厚靶氘氚(D-T)反应中子产额的计算方法模拟计算了入射氘离子能量为120 keV时D-T中子源的中子产额。研究了氘离子源产生的束流中单原子氘离子(D+)及双原子氘离子(D2+)比例对中子产额的影响。结果表明,提高D+比例,同时降低D2+比例将有效提高中子产额。另外还研究了不同靶膜材料及组分引起的中子产额变化。表明中子产额与靶膜中氚的含量成正比,与靶膜元素的原子质量成反比。同时分析讨论了离子源品质及靶参数对中子源整体性能的影响,得出离子源束流品质的提高对中子源整体的设计至关重要。最后,模拟计算了靶膜表面有氧化层情况下中子产额的变化,并与实验结果作了对比。在此基础上提出了一种新的靶设计方案,并对其物理可行性进行了研究。