Radiative losses of alpha particles on heavy ions in fusion plasma

A new channel of radiative losses in fusion plasma with impurities of multielectron ions associated with their excitation by fast alpha particles has been studied. It has been shown that this loss channel for tungsten impurity is comparable with standard radiative losses of plasma electrons.     

First measurements in search for keV sterile neutrino in tritium beta-decay in the Troitsk nu-mass experiment

We present the first results of precision measurements of tritium -decay spectrum in the electron energy range 16–18.6 keV by the Troitsk nu-mass experiment. The goal is to find distortions that may be caused by the existence of heavy sterile neutrinos. A signature would correspond to a kink in the spectrum with characteristic shape and end point shifted by the value of a heavy neutrino mass. We set new upper limits to the neutrino mixing matrix element U _e4 ² , which improve existing limits by a factor of 2 to 5 in the mass range of 0.1–2 keV.     

JET: Preparing the future in fusion

JET (Joint European Torus) is the largest tokamak in the world and the only fusion facility able to operate with Tritium, the fusion fuel, and Beryllium, the ITER first wall material. JET also features the most complete remote handling equipment for invessel maintenance. As a multinational research center, JET provides logistic experience in preparing for operation of the global facility, tokamak ITER.Experiments on JET are focused on ITER-relevant studies, in particular on detailing the operational scenarios (EL My H-modes and advanced regimes), on enhancing the heating systems, on developing diagnostics for burning plasmas etc. Pioneering real-time control techniques have been implemented that maximize performance and minimize internal disturbances of JET plasmas. In helium plasmas, ion cyclotron heating (ICRH) created fast α-particles, mimicking their populations in future burning plasmas. The recent successful Trace Tritium campaign provided important new data on fuel transport. Current enhancements on JET include a new ITER-like ELM-resilient high power ICRH antenna (7 MW) and over twenty new diagnostics that will further extend the JET scientific capabilities and push the facility even closer to the ITER parameters.A special mention is given to the involvement of the fusion experts from Association EURATOM-IPP.CR, who have been actively participating in the collective use of JET facility for more than three years.     

正硅酸锂陶瓷小球离线释氚实验研究

中国氦冷球床包层(CH HCSB TBM)初步采用Li₄SiO₄陶瓷小球作为氚增殖材料,实验研究了Li₄SiO₄陶瓷小球的中子辐照产氚性能。将冷冻成型法制备的Li₄SiO₄ 陶瓷小球置于反应堆中辐照100min,然后在离线释氚实验平台上进行退火行为研究。实验结果表明,在用He +1% H₂为载气,流速为100mL•min^-1,升温速率为5K•min^-1的实验条件下,氚气(HT+T₂)是Li₄SiO₄陶瓷小球的主要释氚形态,占总氚的70%左右(不包括自由氚中的氚气),在400℃~700℃范围内出现两次释氚峰;氚化水(HTO+T₂O)所占比例小于20%,主要在300℃~500℃的低温段进行释放;氚在800℃前基本释放完,小球退火后的残氚量小于1%。冷冻成型干燥法制备的Li₄SiO₄陶瓷小球在300℃~700℃范围内有较好的释氚性能,氚残留量低,在聚变堆固态氚增殖包层设计中具有一定应用价值。     

First PAC experiments in MAX-phases

MAX-phases are hexagonal ternary carbides and nitrides with the general formula: M _n?+?1 AX _n and n = 1 to 3. ¹¹¹In was implanted into the two MAX compounds Ti₂InC and Zr₂InC. Based on the general knowledge of previous ¹¹¹In implantations one expects to find the probes on the indium lattice-site in these compounds. First experiments on the annealing behaviour and the thermal stability of the indium-containing MAX-phases are reported. The observed EFGs are interpreted and first PAC-measurements under compressive stress are shown.     

Measurement of X-rays from muon to alpha sticking and fusion neutrons in solid/liquid D-T mixtures of high tritium concentration

We measured the yields of K-series X-rays from (αμ)⁺ ion formed by muon to alpha sticking as well as the yields and the disappearance rates of fusion neutrons in ³He-free solid and liquid D-T mixtures. The effective sticking probability ω_s obtained by neutron measurement is much smaller than any theoretical values so far published, while the discrepancy in αμ X-ray yield seems less significant. This revised version was published online in August 2006 with corrections to the Cover Date.     

Studies of UV-cured CR-39 recording properties in view of its applicability in radiobiological experiments with alpha particles

In radiobiology, low doses of high-LET radiation correspond to a few particle traversals through the cell population. Therefore, for studies on cell monolayers irradiated with a low dose of -particles, it is extremely useful if the number and position of particle traversals can be determined. In this study we describe a new method, based on UV-curing, to obtain a thick CR-39 grafted onto a thick PolyEthylene Terephtalate (PET). This thin double polymeric layer, used as a dish base, has a regular and reproducible detector thickness which can be traversed by 3.5 MeV -particles, with a sufficient residual energy to traverse mammalian cells attached to the base. The recording properties of a PET-CR-39 dish, together with a demonstration of its use for radiobiological experiments, are presented. This new tool allows the precise determination of single-track impact parameters at a sub-cellular level.     

Coincidence measurements of light particles and evaporation residues in the 16O+27Al fusion reaction

Energy and angular distributions of protons and α-particles in coincidence with fusion residues produced in the reaction of 150 MeV ¹⁶O with ²⁷Al were measured. Experimental results are reproduced by a statistical model calculation except a forward component of α-particle yield. About 20% of the total α-particle yield is considered to originate from incomplete fusion process.     

聚变堆液态包层提氚鼓泡器的概念设计

在气-液接触法提取液态锂合金中的氢的实验基础上,提出了以气-液交换柱为核心的提氚鼓泡器(LBTB)的概念设计。LBTB 主要由气体进样纯化器、气-液交换柱系统、饱和器－解吸器和辅助系统构成。LBTB以氩氢混合气为吹洗气,其主要功能是在线监测液态包层主回路中的氚行为,并检验多柱级联后的氚回收率是否可以达到90%的期望值。     

�۱��Һ̬������밹������ĸ������

在气-液接触法提取液态锂合金中的氢的实验基础上,提出了以气-液交换柱为核心的提氚鼓泡器(LBTB)的概念设计。LBTB 主要由气体进样纯化器、气-液交换柱系统、饱和器－解吸器和辅助系统构成。LBTB以氩氢混合气为吹洗气,其主要功能是在线监测液态包层主回路中的氚行为,并检验多柱级联后的氚回收率是否可以达到90%的期望值。     

In situ measurements of gamma-ray intensity from radon progeny in rainwater

The radon progeny concentration in raindrops as well as in cloud droplets has been determined based on a simplified rainout model from the in situ measurement of gamma-ray intensity using an HPGe detector. The radon concentration in cloud air was deduced from the radon progeny concentration in cloud droplets by applying the Junge's equation. From the measured radon progeny concentration in raindrops the additional exposure rate due to rainfall has been evaluated and compared with the HPIC monitoring data.     

Environmental studies in Antarctica on the basis of tritium and radiocarbon measurements

In 1975 and 1977, samples from snow, firn, atmospheric CO(2), plants, and penguin guano were collected near the Soviet Antarctic research station Molodezhnaya. The results of tritium, deuterium, oxygen-18, (13)C, and (14)C measurements are discussed. From the tritium, deuterium, and (18)O measurement results of a firn profile at the Hays glacier, a value of the accumulation rate of 30 g water per cm 2 and year could be evaluated. By means of (14)C dating, the age of penguin breeding places was determined to be 1500 ± 500 years. (14)C data from atmospheric CO(2) and plants are discussed in terms of the age of the plants.     

Identification of bunches and particles in LHC experiments

Problems associated with the identification of bunches and particles used at the largest installations designed for LHC experiments are considered. In addition, parameters of such detectors as time-projection chambers, ring-imaging chambers, transition-radiation detectors, time-of-flight systems based on resistive-plate chambers, and calorimeters used for particle identification are considered. Installations designed by JINR and other Russian physicists for particle identification are described.     

Discovery of temperature-dependent phenomena of muon-catalyzed fusion in solid deuterium and tritium mixtures

A systematic experimental study on muon-catalyzed fusion was conducted using a series of solid deuterium and tritium mixtures. A variety of conditions were investigated, i.e., tritium concentrations from 20% to 70%, and temperatures from 5 to 16 K. With decreasing temperature, we observed an unexpected decrease in the muon cycling rate (lambda(c)) and an increase in the muon loss probability (W). The origins of these observed changes were interpreted by the temperature-dependence in the dt mu formation process for lambda(c) and that in the muon reactivation process after muon-to-alpha sticking for W.     

A fitting formula for electron–ion energy partition fraction of 3.54-MeV fusion alpha particles in hot dense deuterium–tritium plasmas

Based on our previous work(Phys.Plasmas 25 012704(2018)),a fitting formula is given for electron-ion energy partition fraction of 3.54-MeV fusion alpha particles in deuterium-tritium(DT) plasmas as a function of plasma mass density ρ,electron temperature T_e,and ion temperature T_i.The formula can be used in a huge range of the plasma state,where ρ varies between 1.0 g/cc~10.0³ g/cc and both T_e and T_i change from 0.1 keV to 100.0 keV.Relativistic effect for electrons is investigated including the effect of the projectile recoil in the plasmas at T_e≥ 50.0 keV.The partition fraction for T_e>T_i is found to be close to that for T_e=T_i. The comparisons with other fitting results are made at some plasma densities when T_e=T_i,and the difference is explained.The fitting result is very close to the calculated one in most cases,which is convenient for the simulation of alpha heating in hot dense DT plasmas for inertial confined fusion.     

氘氚聚变中子发生器旋转氚靶传热特性研究

强流氘氚中子发生器可用于模拟聚变堆中子环境, 对于开展聚变堆包层材料相关实验研究具有重要意义. 本文提出了一种用于10¹² n·^-1量级氘氚中子发生器HINEG (high intensity neutron generator)的旋转氚靶系统设计方案, 并对其技术难点和强化传热方法进行了介绍. 为考查该氚靶系统的传热特性, 利用Computational Fluid Dynamics方法对冷却水层厚度、冷却水流速和氚靶系统旋转速度对靶面冷却的影响进行了分析, 并对不同热功率密度下靶面的传热过程进行了研究. 结果显示, 大的水层厚度、大的冷却水流速和高的靶系统旋转速度有利于靶面的冷却, 但水层厚度和水流速的变化对靶面传热影响较小. 一定条件下靶面所承受的热功率密度不能超过某个限值.     

Experimental detection and investigation of muon catalyzed fusion of deuterium and tritium

Measurement of the neutron yield of the reaction $\text{dt}\text{μ →}{}^4\text{He}\text{+ μ}{}^{\mathrm{?}}\text{+ 17.6}\text{MeV}$, induced by negative muons in a mixture of gaseous D₂ and T₂, has shown that the rate of muon transfer from deuterium to tritium is λ_dt = (2.7 ± 0.9) × 10⁸s^?1 and that the lower limit of the formation rate of dt_μ molecules is λ_dtμ > 10⁸s^?1.