The applications of nuclear track detectors in transuranic contamination problems

Nuclear Track Methodology (NTM) is very well known for its possibilities in applications in a wide variety of fields. The appearance of the polycarbonate as alpha radiation detector material, established a very confident monitoring surface alpha contamination, soil and water alpha activity. The purpose of the study is to investigate the utility of the CR-39 (Allyl Diglycol Carbonate) in fast semi-quantitative transuranic contaminant evaluation, including the distribution in underground contaminated soils, hot spots and transuranic material accumulations.     

Status and applications of cryogenic detectors

An overview of the actual technical status and achievements of different types of cryogenic detectors is given. Typical applications in several fields are discussed with emphasis put on appropriate nuclear experiments for the planned Princeton facility. The possibility of implementation in low temperature nuclear orientation experiments will be explored.     

Particularization of alpha contamination using CR-39 track detectors

Solid-state nuclear track detectors have found wide use in various domains of science and technology, e.g. in environmental experiments. The measurement of alpha activity on sources in an environment, such as air is not easy because of short penetration range of alpha particles. Furthermore, measurement of alpha activity by most gas ionization detectors suffers from high background induced by the accompanying gamma radiation. Solid state nuclear track detectors (SSNTDs) have been used successfully as detecting devices and as a passive system to detect alpha contamination on different surfaces. This work presents the response of CR-39 (for two types) to alpha particles from two sources, ²³⁸Pu with energy 5 MeV and ²⁴¹Am with energy 5.4 MeV. The methods of etching and counting are investigated, along with the achievable linearity, efficiency and reproducibility. The sensitivity to low activity and energy resolution are studied.      

Study of semiconductors using solid state nuclear track detectors

Uranium trace characterization of crystalline GeS, sputtered thin films of GeS and amorphous SiH on quartz substrates, and crystalline p-type Si using the technique of solid state nuclear track detectors is reported. Concentration and distribution of uranium in these materials studied are presented. Using uranium as microprobe, it is observed that uranium prefers to be in the cleavage planes of GeS crystals. There seems to be a link between uranium concentration and the thermally induced defects in Si.     

Hybrid fusion reactor for production of nuclear fuel with minimum radioactive contamination of the fuel cycle

The paper presents the results of the system research on the coordinated development of nuclear and fusion power engineering in the current century. Considering the increasing problems of resource procurement, including limited natural uranium resources, it seems reasonable to use fusion reactors as high-power neutron sources for production of nuclear fuel in a blanket. It is shown that the share of fusion sources in this structural configuration of the energy system can be relatively small. A fundamentally important aspect of this solution to the problem of closure of the fuel cycle is that recycling of highly active spent fuel can be abandoned. Radioactivity released during the recycling of the spent fuel from the hybrid reactor blanket is at least two orders of magnitude lower than during the production of the same number of fissile isotopes after the recycling of the spent fuel from a fast reactor.     

Single-sheet identification method of heavy charged particles using solid state nuclear track detectors

The theoretical and experimental investigations of the penetration of charged particles in matter played a very important role in the development of modern physics. Solid state nuclear track detectors have become one of the most important tools for many branches of science and technology. An attempt has been made to examine the suitability of the single-sheet particle identification technique in CR-39 and CN-85 polycarbonate by plotting track cone length vs. residual range for different heavy ions in these detectors. So, the maximum etchable ranges of heavy ions such as ⁹³Nb, ⁸⁶Kr and ⁴He in CR-39 and ⁴He and ¹³²Xe in CN-85 polycarbonate have been determined. The ranges of these ions in these detectors have also been computed theoretically using the Henke-Benton program. A reasonably good agreement has been observed between the experimentally and theoretically computed values.      

Effect of environmental conditions on radon concentration-track density calibration factor of solid-state nuclear track detectors

In this work, the effect of environmental conditions viz., temperature (T) and relative humidity (RH) on the track density-radon concentrations calibration factor (K) has been studied for CR-39 and LR-115 track detectors. The factorK was determined using a reference radon chamber in the National Institute for Standards (NIS) in Egypt. Track detectors were etched at the recommended optimum etching conditions. It is found that, the calibration factorK varies with bothT and RH, so they should be considered for the sake of uncertainty reduction. Good agreement is found between the calculated and measured values ofK and the compatibility between them is in the range of experimental uncertainty.     

Final results of the EDELWEISS-II WIMP search using a 4-kg array of cryogenic germanium detectors with interleaved electrodes

The EDELWEISS-II Collaboration has completed a direct search for WIMP dark matter with an array of ten 400-g cryogenic germanium detectors in operation at the Laboratoire Souterrain de Modane. The combined use of thermal phonon sensors and charge collection electrodes with an interleaved geometry enables the efficient rejection of γ-induced radioactivity as well as near-surface interactions. A total effective exposure of 384 kg d has been achieved, mostly coming from fourteen months of continuous operation. Five nuclear recoil candidates are observed above 20 keV, while the estimated background is 3.0 events. The result is interpreted in terms of limits on the cross-section of spin-independent interactions of WIMPs and nucleons. A cross-section of 4.4×¹⁰−8 pb is excluded at 90%CL for a WIMP mass of 85 GeV. New constraints are also set on models where the WIMP-nucleon scattering is inelastic.     

Secondary nuclear fragment beams for investigations of relativistic fragmentation of light radioactive nuclei using nuclear photoemulsion at Nuclotron

Slowly extracted relativistic beams of light nuclei and a beam transportation line net system constitute a good base for secondary nuclear beams forming at the LHE accelerator facility. A recent years activity in the field at the Laboratory is connected with a project on study light nuclei structure by means the emulsion technique [1,2]. The paper shortly summarizes results of the work.     

Measurement of the energy spectra of fission fragments using nuclear track detectors and digital image processing

Energy spectra of fission fragments were determined using a Nuclear Track Methodology (NTM) supported by digital image analysis and numerical data processing using a standard personal computer. The analysis of a californium (²⁵²Cf) spectrum with this approach shows improvement compared with the values reported previously using the standard procedure, in terms of resolution and accuracy. This new method adds full automation to the technical advantages and cost effectiveness of an NTM.     

Investigation of uranium dioxide distribution dissolved in silicate compositions using solid state nuclear track detectors

The method of solid state nuclear track detectors (SSNTD) has been used for the determination of uranium dioxide distribution in silicate compositions. The method of -radiography based on registration of - particles at the contact of SSNTD CR-39 with the specimen has been used here. An initial uranium dioxide applied for studying the dissolving process used as the standard. The results of the measurements of distribution of uranium dioxide concentration obtained with the help of this technique have been used for the estimation of diffusion and solubility of UO₂ in silicate melts.     

Measurement of indoor radon levels in Erbil capital by using solid state nuclear track detectors

Radon alpha activity concentration has been measured in 28 homes in the Erbil Capital-Iraqi Kurdistan region during the autumn season by using time-integrated passive radon dosimeters containing CR-39 solid state nuclear track detectors “SSNTDs”. The radon activity concentrations in these homes range from (10.33–90.34) with an average of . The average absorption effective dose equivalent for a person living in homes for which the investigation were done was found to be , obtained by using an equilibrium factor of 0.5 and an occupancy factor of 0.8. The average lung cancer cases per year per 10⁶ person was found to be 23±12.     

Temperature quenching of luminescence for linear and derivative nuclear operators

An earlier study of the thermal quenching of luminescence using the single-configurational-coordinate model is extended from Condon-approximation overlap integrals 〈u_n|v_m〉² to the linear and derivative integrals 〈u_n|z_v|v_m〉² and 〈u_n|?/?z_v|v_m〉². For non-radiative transitions, the thermally weighted nuclear factor in the transition rate is, for the linear and derivative integrals, the corresponding factor for 〈u_n|v_m〉² integrals multiplied by 2E_Xv/?ω_v and $\text{2[E}{}_{\mathrm{Xv}}\text{- E}{}_{\mathrm{p}}{}_{\mathrm{U}}\text{(T)]/}\text{h}\text{?}\text{ω}{}_{\mathrm{v}}$, respectively. E_Xv is the energy of the crossover above the initial- v-parabola minimum, and E_pU(T) is the single activation energy fitted to the nuclear factor's temperature dependence for 〈u_n|v_m〉² integrals. These multiplying factors are exact for equal parabola force constants and good approximations for unequal force constants. These multiplying factors will be difficult to distinguish experimentally. The more important considerations for fitting the model to thermal-quenching data are the parabola placement and the Condon-approximation integrals described previously.     

Kaon and pion ratio probes of jet quenching in nuclear collisions

Non-Abelian energy loss in quark gluon plasmas is shown to lead to novel hadron ratio suppression patterns in ultrarelativistic nuclear collisions. Here we investigate pion and kaon production in pp and AA collisions in a perturbative QCD frame, suppression pattern and hadron ratios. The K^?/K⁺ and K⁺/π⁺ ratios are found to be most sensitive to the opacity (density) of the plasma. Experimental data indicate that the fragmentation dominated pQCD region will be reached only at higher p _T; in an intermediate p _Tregion other particle production mechanisms dominate the K/π ratios.     

低温低噪声放大器产品详细规范制定研究

介绍了低温低噪声放大器产品结构、功能和用途。分析了现行低温低噪声放大器相关标准的适用情况,针对噪声温度、可靠性等质量特性,提出了包含产品全部要求和内容的详细规范制定方案,研究了详细规范中性能参数、测试方法和环境试验等关键技术要素的制定。结果表明:该标准规范了低温低噪声放大器详细要求的制定方法,适用于该产品的设计、制造及质量评价。     

Obtaining colder ensembles of free clusters by using evaporation and recoil

We describe a theoretical model which treats the effects of evaporation-induced recoil on the mass and temperature distributions of a collimated beam of small neutral clusters emitted by a hot-nozzle source. The model incorporates two important consequences of in-flight cluster fragmentation processes. One is the well-known statistical evaporation of atoms and dimers accompanied by cluster size redistribution and cooling, and the other is the accompanying mechanical recoil of the fragments. We predict that the filtering effect introduced by cluster recoil can be used to an advantage by separating out the off-axis cluster population. This fraction will have a significantly narrower and colder distribution of internal temperatures than the on-axis ensemble.     

The slowing-down of low-energy recoil atoms in solids and liquids investigated by nuclear resonance fluorescence

Using the nuclear resonance-fluorescence technique, the slowing down mechanisms of recoiling¹⁴⁰Ce nuclei in La, LaMg₃ and La₂O₃, are studied via the Dopler shift of the 1.596 MeV transition, following the decay of¹⁴⁰La. In LaMg₃ the slowing down time shows a pronounced temperature dependence with a sharp drop close to the melting point. In the oxide, as well as in the metal with only a small oxygen content, the slowing down time is considerably smaller than in the pure metal. These results are in support of a model, describing the slowing down process in solids in terms of a damped oscillation, with a time dependence related to the phonon frequency spectrum.Supported by Deutsche Forschungsgemeinschaft through contract Schu 222