Magnetic Moment Measurement of ^28p

The last proton separation energy of β-emitting nuclide ^28p is 0.6 MeV and its last proton occupies the orbit 2s1/2. At present, all of the results showed that there exists proton halo structure in ^28p, whether from the measurements of cross section or from the theoretical study. No magnetic moment or quadrupole moment of ^28p have been reported until now. But the value of nuclear moments is a very important experimental data for the decision of halo structure.     

Re-estimation of absolute gamma ray intensities of ^56Mn using k0-standardization

The thermal neutron capture gamma ray facility at Pakistan Research Reactor （PARR-1） is being used for the re-estimation of various properties like capture cross-sections, resonance integral, absolute gamma intensities, etc. of different isotopes. The data for gamma ray transitions from the capture of thermal neutrons by ^55Mn are not in good agreement specifically below 2 MeV. So there is a need to re-estimate its intensities with better accuracy. Analytical grade MnCl2 powder and high purity Mn metal pieces were used in this study. Standard ^152Eu and ^60Co radioactive sources as well as thermal neutron capture γ-rays in chlorine were chosen for efficiency calibration. The k0 standardization technique was applied for these measurements to eliminate systematic errors in efficiencies. Chlorine also acted as a comparator in k0-factor calculations. The results have been tabulated for the main gamma rays from ^56Mn in the low as well as in the medium energy regions. The absolute intensities are in good agreement with most of the reported values.     

Measurement of fast－neutron capture cross sections for ^75As

The cross sections of the ^75As(n,γ)^76As reaction were measured in the neutron energy range from 0.50 to 1.50 MeV by using the activation technique.Neutrons were produced via the T(p,n)^3He reaction and the cross sections of the ^197Au(n,γ)^198Au reaction were used to determine the absolute neutron flux.Present results are compared with existing measurements and evaluations.     

Comparable investigation in dopamine transporters with ^99mTc-TRODAT-1 and ^131I-FP-CIT SPECT in Parkinson＇s disease patients

Dopamine transporter （DAT） mediates the regulation of dopaminergic function. Two agents of TRODAT-1 and FP-CIT were observed in evaluating DAT change of Parkinson＇s disease （PD）. The relationship between them was also evaluated. The results suggested that ^99mTc-TRODAT-1 SPECT and ^131I-FP-CIT SPECT may serve as sensitive and objective in vivo markers to reflect the severity of PD. The ^99mTc-TRODAT-1 image is more accurate and clearer compared with ^131I-FP-CIT.     

Measurements of ^134Cs and ^137Cs in urine and estimation of the internal dose of an adult exposed to the Chernobyl Accident

To estimate the internal dose of a Chinese visiting scholar internally contaminated because of the Chernobyl Accident, the contents of 134Cs and 137Cs in urine were measured using a Ge（Li） γ-spectrometer. The internal doses were calculated based on data from the ICRP Publications. The effective doses from ^134Cs and ^137Cs were estimated to be 61 μSv and 98 μ Sv, respectively. The sum of 159 μSv was lower than the total effective dose （310 μSv）, from the inhalation and ingestion of natural radionuclides. The dose of ^131I was also reviewed referring to the UNSCEAR 2000 Report. The equivalent effective dose of ^131I was estimated to be 2.9 mSv, 18 times more than the amount of ^134Cs and ^137Cs. Therefore, it is considered that the earlier estimation of internal doses of ^131I is important in evaluating radiation injuries from a nuclear reactor accident.     

Systematics Study of the Independent Yields for Neutron-Induced Fission of ^235,238U and ^239pu

The fission yields play important rolls in the nuclear engineering, such as the calculations for the decay energy and the poisonous material in reactor engineering. The independent yield is the main part of the fission yields. The systematics of the independent yields was studied for fission of ^235＇238U and ^239pu induced by thermal, fission spectrum and fast（about 14 MeV） neutron with Zp model, and the data were evaluated. The results were compared with the data from other libraries such as ENDF/B6, JEF-3.0 and JENDL3.3.     

Dynamic Study of Fusion Reactions of ^40,48Ca＋^90,96Zr

Based on the Improved Quantum Molecular Dynamics Model the fusion reactions of ^40,48Ca＋^90,96Zr are studied by making a more rigorous treatment of the initial condition. The study shows us that： （1） the calculated fusion cross sections for all four reactions of ^40,48Ca＋^90,96Zr are in good agreement with experiment data;     

Synthesis and application of PLGA labeled with ^125I

The weight loss in vivo degradation of poly （lactide-co-glycolide） （PLGA） radiolabeled with ^125I was investigated. PLGA with molecular weight （Mw） of 84000（LA/GA= 85/15） were labeled with ^125I in the chloroform media by circularly heating and round films of about 15 mm in diameter were formed. The composition and Mw of the ^125I-PLGA were characterized by ^1H-NMR and viscosimeter. The weight loss of this copolymer in vitro and in vivo degradation was quantified by determining radioactivity of materials. The results indicated that PLGA exhibited significantly faster degradation in vivo than that of in vitro conditions.     

Pre-formation Probability of ^5He Cluster in Pre-equilibrium Mechanism

A new reaction model for light nuclei of lp shell is expanded to ^19F with 2s-ld shell nucleus. The double-differential cross sections of total outgoing neutron for n＋^19F reactions at En = 14.2 MeV are calculated and analyzed, and the calculated results agree fairly well with the experimental measurements.     

Preparation of ^151Sm Standards for AMS Measurement

^151Sm （T1/2=90 a） is a kind of long-lived fission products. It was applied to the industry, agriculture, national defence and many other fields. The measurement of ^151Sm is very significant in environment science, and life science, etc. The content of Sm in samples is very low especially in biological samples （10^-6-10 ^-9）, so AMS is the best choice for the measurement of Sm with high sensitivity. But AMS is a kind of relative measurement method which needs standards to calibrate. The preparation of ^151Sm standards is described in this paper.     

Application of the Monte Carlo method to the analysis of measurement geometries for the calibration of a HP Ge detector in an environmental radioactivity laboratory

A gamma spectrometer including an HP Ge detector is commonly used for environmental radioactivity measurements. The efficiency of the detector should be calibrated for each geometry considered. Simulation of the calibration procedure with a validated computer program is an important auxiliary tool for environmental radioactivity laboratories. The MCNP code based on the Monte Carlo method has been applied to simulate the detection process in order to obtain spectrum peaks and determine the efficiency curve for each modelled geometry. The source used for measurements was a calibration mixed radionuclide gamma reference solution, covering a wide energy range (50-2000 keV). Two measurement geometries - Marinelli beaker and Petri boxes - as well as different materials - water, charcoal, sand - containing the source have been considered. Results obtained from the Monte Carlo model have been compared with experimental measurements in the laboratory in order to validate the model.     

Interstitial Defects in p-Type Silicon

Two defects introduced in boron- and aluminum-doped silicon by 1.5-MeV electron irradiation have been studied by means of infrared photoconductivity. The defects have been identified as being dopant atoms in interstital positions. Stress-induced dichroism measurements have allowed the determination of the defects' symmetry which is C3v.     

Application of Particle Filtering for Estimating the Dynamics of Nuclear Systems

System dynamics estimation is a crucial issue for the safe operation and control of nuclear power plants. Typically, the estimation is based on a model of the plant dynamics and related measurements. In practice, the non-linearity of the dynamics and non-Gaussianity of the noise associated to the process and measurements lead to inaccurate results even with advanced approaches, such as the Kalman, Gaussian-sum and grid-based filters. On the contrary, accurate results may be obtained with Monte Carlo-based estimation methods, also called particle filters. The present paper illustrates the developments of a previous work by the same authors with regards to the comparison of the so called sampling importance resampling filter method with the standard and extended Kalman filtering techniques. Two case studies are analyzed to separately highlight the effect of non-linearity and non-Gaussianity in the process noise.     

Correlation of in-plane bending test and FEA results for thin-walled elbows

The objective of this study is to validate a finite element analysis (FEA) simulation methodology to predict the global behavior of thin-walled elbows subjected to in-plane bending. Two in-plane closing mode bending tests and one in-plane opening mode bending test were conducted on 2″ schedule 10 elbows, and a nonlinear FEA procedure was used to simulate the tests. A detailed FEA study was carried out to determine the relative importance of weld size and location, measured wall thicknesses, and original cross-section dimensions on the reconciliation results. When the weld bead was included in the analysis, the reconciliation results for load–displacement behavior and some of the strain measurements were excellent. For those cases in which the strain measurements reconciliations were not so good, a possible explanation is provided.     

Results of the temperature noise measurements in subchannels of sodium cooled electrically heated 28 rod bundle behind a blockage

For LMFBR safety studies a 28 rod bundle has been built at Petten (cooperation of GfK and ECN), representing a 60-degrees section of an SNR-300 fuel element having a 70% flat type central blockage. The aims of the temperature noise measurements were to determine the subchannel coolant velocities behind the blockage to study the mixing of coolant in subchannels of different temperature from behind the blockage to the outlet and to study the temperature noise due to boiling in a subchannel. The temperature noise measurements were carried out in parallel to the other measurements (temperature distribution, etc.), using signals of fourteen subchannel thermocouples placed in five measuring planes behind the blockage. The single phase measurements were made with several heat fluxes (5 W/cm² to 120 W/cm²), inlet flows (0.25 to 3 m/s) and inlet temperatures (250°C to 600°C). Two phase flow is initiated and sustained either by a slow and continuous pressure reduction or by stepwise reduction of the main flow. The temperature noise signals were amplified and recorded in analog form. Later the signals were digitized and analysed by digital computers. Part of the signals was also processed by a hardware correlator. The experimental results of the temperature noise measurements will be shown for the different conditions of the loop. Measurements clearly show the following effects:

• - the recirculation flow pattern due to the vortex in the wake behind the blockage;

• - the dependence of r.m.s. value of the noise on the heat flux and the coolant flow;

• - the increase in noise and change in power spectra when going from single phase to the boiling condition.

     

Monte Carlo simulation of synchrotron radiation transport and calculation of dose to the components of a high-energy accelerator

An electron-positron collider (LEP) has recently been put into operation at CERN. Two 46 GeV beams circulate around the 27 km accelerator ring and these produce intense synchrotron radiation with photon energies up to more than 1 MeV. A lead shiedl 8 mm thick has been provided in most places around the vacuum chamber to minimize radiation damage to sensitive machine components. Monte-Carlo techniques using a modified version of MORSE have been used to estimate dose-rate levels in the tunnel due to radiation escaping from the vacuum pipe and scattered by magnets and the tunnel walls. The results have been confirmed by dosimetry measurements.     

电子直线加速器加速系统的相位测量

文章叙述了两种微波相位测量方法及其在BEPC电子直线加速器微波加速系统研制和运行中的应用。测量微波加速系统的相让噪声、相位调制、相位抖动和相位漂移;测量速调管和行波管放大器各极电压的相位灵敏度;监测加速管工作温度和正确选择工作温度以及实现加速系统最佳相位控制。     

Concentration profiles in paint layers studied by differential PIXE

Differential PIXE measurements varying the proton energy were used to probe the concentration profiles of metal-based pigments in paint layers. The algorithms developed earlier for metal targets were improved and enhanced to include light elements; the necessary information on chemical compounds has to be provided by complimentary methods. The de-convolution method employs slicing the target into layers characterized by mean production depths; the matrix inversion is replaced by a min χ² problem. Two different methods of normalization are used: setting the sum of weight fractions of particular compounds to unity, and direct measurements of the projectile number, in our case through the argon line excited in the air. The efficiency of the two methods was compared for paint layers in frescoes, showing that smother concentration profiles are obtained using the measured proton numbers. Conversion of the layer areal densities into geometrical thicknesses is discussed.     

Characterisation of titanium beryllides with different microstructure

Preliminary investigations revealed that beryllides like Be₁₂Ti may be much more suitable for use as a neutron multiplier in future fusion power plants compared to pure beryllium. Two sorts of Be–Ti samples having different grain sizes but consisting, mainly, of Be₁₂Ti have been fabricated. Investigation of microstructure and measurements of tritium release rate allow make a comparison between both types of fabricated titanium beryllides. Obtained results are disclosed in this paper.     

PILIS: post-ISOCELE laser isobar separation; a high efficiency apparatus for laser spectroscopy

A new experimental setup PILIS II has been installed on-line with the ISOCELE isotope separator (IPN, Orsay). The mass-separated ions are slowed from 30 kV to 500 V and implanted on a graphite collecting disk. The atoms are then thermally desorbed at the implantation region by Nd: YAG laser pulses and selectively ionized by three laser beams. The ions created are mass identified by a time-of-flight (TOF) system. Two versions of the TOF system with accelerating voltages of 1.5 and 30 kV were used to carry out hyperfine structure measurements. With the 30 kV system we obtained an overall detection efficiency of 1.4 × 10⁻⁵. First measurements were performed on very light gold and platinum isotopes. It has been shown that PILIS II is well adapted to study very short half-life isotopes ( ).