Light Particle and Complex Fragments Emission from 12C Induced Reactions on 58Ni,64Ni at E/A=46.2MeV

Energy spectra of light charged particles and complex fragments emitted in the interaction of 46.2MeV/u ¹²C with different target ⁵⁸Ni,⁶⁴Ni,¹²C,¹⁹⁷Au and ²⁰⁹Bi have been measured by telescopes,consisting of CsI(Tl) and surface barrier detector stacks.These telescopes for light charged particles and complex fragments have good energy resolution and mass identification.The inclusive data have been analysed within a moving source parametrization.The complex fragment yields from different targets have been compared at several angles.The systematic variation of deduced isotope yields ratios with different reaction systems is used to detemine the N/Z degree of freedom equilibration of the system achieved.     

Measurements of charge transfer efficiency in a proton-irradiated swept charge device

Charged Coupled Devices (CCDs) have been successfully used in several low energy X-ray astronomical satellites over the past two decades. Their high energy resolution and high spatial resolution make them a perfect tool for low energy astronomy, such as observing the formation of galaxy clusters and the environment around black holes. The Low Energy X-ray Telescope (LE) group is developing a Swept Charge Device (SCD) for the Hard X-ray Modulation Telescope (HXMT) satellite. A SCD is a special low energy X-ray CCD, which can be read out a thousand times faster than traditional CCDs, simultaneously keeping excellent energy resolution. A test method for measuring the charge transfer efficiency (CTE) of a prototype SCD has been set up. Studies of the charge transfer inefficiency (CTI) with a proton-irradiated SCD have been performed at a range of operating temperatures. The SCD is irradiated by 3×10⁸cm^-2 10 MeV protons.     

Physical Explanation on Designing Three Axes as Different Resolution Indexes from GRACE Satellite-Borne Accelerometer

The GRACE Earth＇s gravitational field complete up to degree and order 120 is recovered based on the same and different three-axis resolution indexes from satellite-borne accelerometer using the improved energy conservation principle. The results show that designing XA1（2） as low-sensitivity axis （3 × 10^-9 m/s^2） of accelerometer and designing YA1（2） and ZA1（2） as high-sensitivity axes （3 × 10^-10 m/s^2） are reasonable. The physical reason why the resolution of XA1（2） is one order of magnitude lower than YA1（2） and ZA1（2） is that non-conservative forces acting on GRACE satellites are mainly decomposed into YA1（2） and ZA1（2） in the orbital plane. Since XA1（2） is not orthogonal accurately to orbital plane during the development of accelerometer, the measurement of XA1（2） can not be thrown off entirely, but be reduced properly.     

A Prototype of X-Ray Imaging Based on the GEM Detector

A prototype of X-ray imaging device based on triple Gas Electron Multiply detector is studied,which has an effective gain up to 10⁵ and can be used in high rate X-rays imaging.The precise method of micro–strip readout is designed for X-rays localization, and the crate controller of high–speed SCSI interface is applied for the data acquisition.The test results show that the position resolution of measurement system is less than 90μm and the stability of its effective gain is better than 1% under the X-ray flux of 10⁵Hz/mm².     

INVESTIGATION OF THE 238U ION TRACKS REGISTERD IN POLYCARBONATE CHAOYANG NO.1

We have studied the registration characteristics of polycarbonate ChaoYang No.1 for ²³⁸U. The experimental range of ²³⁸U in it was determined. The relation between the energy of ²³⁸U and range and the relation between the energy and REL of ²³⁸U in it are calculated. The V_T versus REL response, the charge resolution and the mass resolution for heavy charged particles are analysed and discussed.     

RADIOCHEMICAL INVESTIGATION OF MASS DISTRIBUTIONS IN 12C-INDUCED FISSION OF 209Bi AND 238U

The yields of 15 and 17 fission, products have been obtained by radiochemical determinations in ¹²C-induced fission of ²⁰⁹Bi and ²³⁸U respectively. From these data, the mass distributions of fission fragments are calculated based on three different hypotheses for the charge distribution. The results seem to indicate that the hypothesis of equal charge displacement gives the best fit to the Gaussian distribution for the masses of the fission fragments. By comparison with the mass distributions for ²⁰⁹Bi (¹²C, f), ²³⁸U(¹²C, f) and ¹⁹⁷Au(¹²C, f) in our early measurement, we find that for fission parameter Z²/A>37, the width of the mass distributions increases with Z²/A rapidly.     

Extended Glauber Theory and Its Application in Halo Nucleus Scattering

We introduced an extended Glauber theory for a halo nucleus scattering, where the halo nucleons and the nuclear core were treated separately. Expressions of reaction and interaction cross sections of the halo nucleus scattering were derived. We took the halo structure of the projectile nucleus into account and adopted an improved optical limit approximation. In the framework of the extended Glauber theory, we studied the reaction cross section for the halo nucleus ¹⁴Be scattering on a target ¹²C. For comparison, the reaction cross sections of ¹²Be+¹²C were calculated as well. The density distribution of target ¹²C is taken from experiments, and those of the projectiles ¹²Be and ¹⁴Be were obtained by two methods. One is that the harmonic oscillator wave functions for ¹²Be and ¹⁴Be are used. The length of harmonic oscillator is adjusted to reproduce the reaction cross section of ¹²Be+¹²C at the high energy E=790MeV/u . The density distribution of ¹⁴Be was also calculated self-consistently in the relativistic mean field (RMF) theory, with a long tail wave functions for the two neutrons in ¹⁴Be. It was found that the calculated reaction cross sections for ¹²Be+¹²C at E=790MeV/u and E=56.5MeV/u were in good agreement with the experimental data no matter harmonic oscillator or RMF wave functions were used. In contrast, the experiments of the reaction cross sections for ¹⁴Be+ ¹²C could only be reproduced when the wave functions of two 2s_1/2 neutrons spreaded over with a long tail. It comes to a conclusion that two outside neutrons in ¹⁴Be form a halo structure.     

Investigation of the [лh9/2vi13/2－1] 10－ Isomer in 206At

The high-spin states of ²⁰⁶At have been studied in the ¹⁹⁷An (¹²C, 3n)²⁰⁶At reaction at ¹²C energies from 60 to 80 MeV using technique of in-beam γ-ray spectroscopy. Measurements of Tray excitation functions, γ-γ-t coincidences, and y-ray angular distributions were performed. A level scheme for ²⁰⁶At, including a 10^－ isomer with a measured half-life of 908±400 ns, was established for the first the. The characteristics of the 10^－ isomers in doubly edd ²⁰⁶At nuclei were stressed.     

STUDY OF THE MECHANISM OF 12C（d,d）12C AND 12C（d,p）13C* REACTIONS

A formalism for studying the interference between the direct reaction and the compound resonance processes is presented by the S-matrix theory; The mechanism of ¹²C（d, d） ¹²C, ¹²C（d, p₁） ¹³C* and ¹²C（d, p₂） ¹³C* reactions in the energy range E_d=1.63 MeV to 2.05 MeV is analysed.Te results show that: the interference between these two processes exists; and the quantitative relation between them is given. While the parameters of direct reactions and compound resonance processes, particularly for four resonance states with E_d=1.726, 1.767, 1.792 and 1.86 MeV are determined.     

铝粉快速反应光谱的研究

 使用光学多道分析仪（OMA）详细收集了氢氧气体爆炸产物激励下，两种不同粒度的铝粉在不同氧含量条件下快速反应的低分辨和高分辨光谱。实验结果表明在240~850 nm的光谱范围内的辐射以连续辐射为主，并有较弱的铝原子线和AlO的B²Σ⁺→X²Σ⁺带光谱。     

Level sructure in 206At

The high-spin states of ²⁰⁶At have been studied in the reaction ¹⁹⁷Au (¹²C,3n) ²⁰⁶At at ¹²C energies from 60 to 80 MeV. In-beam measurements of %-ray excitation functions, %-%-t coincidences, and %-ray angular distributions were carried out with seven BGO(AC)HPGe detectors and one intrinsic Ge planar detector. A level scheme for ²⁰⁶At with 25 % rays was established for the first time, including a 10^m isomer with a measured half-life of 410 - 80 ns. The level scheme of ²⁰⁶At consists of two disconnected cascades, probably corresponding to the proton excitations and the neutron-hole excitations, respectively.     

MEASUREMENT AND ANALYSIS OF EMITTED α PARTICLES IN REACTIONS OF 12C BOMBARDING 12C,27Al AND natCa

The energy spectra and angular distributions of the emitted α particles in the reactions of the 69.5MeV ¹²C bombarding ¹²C,²⁷Al and ^natCa have been measured and analysed using the fast particle exciton model. The contribution from the equilibrium and preequilibrium α-emissions is calculated to be 89%, 81% and 83% of the total α yields for the three reactions respectively, where the preequilibrium α emissions are 11%, 14% and 16% respectively. A small contribution comes from the other reaction mechanism.     

Study of Kso Reconstruction and Lifetime Measurement at BESⅡ

The beam collision center of the BEPC has slightly shifted from geometrical origin of the BES detector and the beam bunch of the BEPC also has certain size. For these reasons, to measure K_s^o lifetime, primary vertex reconstruction must be carried out. After the investigation of di-muon, bhabha and hadron events, the beam collision center for each run is determined by bhabha and di-muon events. For the large branching ratio of and the existence of the resonance of KⅡ0 , this channel is chosen to provide much pure K_s^o signal. With the aid of M. C. tools at BES Ⅱ , existing software for secondary vertex reconstruction is adjusted and improved. A new method of secondary vertex determination is used and a better position resolution of secondary vertex is obtained. The lifetime of Ks0 is measured with channel and the inclusive K_s^o mass is investigated with BES Ⅱ 's 50M J/ψ data sample, which give consistent Ks0 lifetime and mass with PDG' s value within error. 1C fit on K⁰_s mass is also studied with M. C. events. The resolution of momentum and energy of 7π+ , π- and K, is improved too.     

ANALYSIS FOR ENERGY SPECTRA OF LIGHT PARTICLES EMITTED FROM 12C+64Ni REACTION

Some experimental results measured for light emission particles with Z≤2 from ¹²C+⁶⁴Ni reaction at E(¹²C)=69, 56MeV are reported. A comparison between moving source model calculation and proton's spectra have been performed. Extracted parameters of the source with faster velocity are agreement with the systematic values found before. The composite particle energy spectra of α, ³He and D were analyzed by coalescence model.     

S-WAVE πN INTERACTION IN (π+d) REACTION

Based on the two nucleon pion absorption mechanism, the reaction (π⁺d) is studied. The formula of the differential cross section for (π⁺d) reaction is obtained for S-wave πN interaction. A calculation is also performed for ¹²C(π⁺d)¹⁰C(0⁺,2⁺) at the incident energy of 49.3MeV by using the plane wave approximation. The results indicate that the effect of the D-wave component in the deutron wave function is quite important. The antisymmetric space structure of the neutron pair participated in the process is as the important as symmetric one.     

Conditioning the γ spectrometer for activity measurement at very high background

The application of a high purity Germanium (HPGe) γ spectrometer in determining the fuel element burnup in a future reactor is studied. The HPGe detector is exposed by a ⁶⁰Co source with varying irradiation rate from 10× 10³m s^-1 to 150× 10³m s^-1 to simulate the input counting rate in real reactor environment. A ¹³⁷Cs and a ¹⁵²Eu source are positioned at given distances to generate a certain event rate in the detector with the former being proposed as a labeling nuclide to measure the burnup of a fuel element. It is shown that both the energy resolution slightly increasing with the irradiation rate and the passthrough rate at high irradiation level match the requirement of the real application. The influence of the background is studied in the different parameter sets used in the specially developed procedure of background subtraction. It is demonstrated that with the typical input irradiation rate and ¹³⁷Cs intensity relevant to a deep burnup situation, the precision of the ¹³⁷Cs counting rate in the current experiment is consistently below 2.8%, indicating a promising feasibility of utilizing an HPGe detector in the burnup measurement in future bed-like reactors.     

INFLUENCE OF THE NEUTRON NUMBER OF TARGET NUCLEUS ON CROSS SECTIONS OF PARTICLES EMISSION IN 12C+112,124Sn

The energy spectra and angular distributions of Li, Be, B particles emitted from the ¹²C+¹¹²Sn and ¹²C+¹²⁴Sn reactions at E_L=70.0MeV are measured. The angular distributions of the Li, Be, and B particles are found to be peaked around the grazing angle, without any forward peaked component.
The experimental results also showed that the cross section for emission is larger in ¹²C+¹¹²Sn reaction than that in ¹²C+¹²⁴Sn reaction, in contrast with the cross sections for Li, Be and B emissions. The indicates the effect of the neutron number of the target nucleus on the emission probability.     

AlGaN-Based Solar-Blind Schottky Photodetectors Fabricated on AlN/Sapphire Template

We report AlGaN-based back-illuminated solar-blind Schottky-type ultraviolet photodetectors with the cutoff- wavelength from 280nm to 292nm without bias. The devices show low dark current of 2.1× 10^-6A/cm^2 at the reverse bias of 5 V. The specific detectivity D＊ is estimated to be 3.3 × 10^12cmHz^1/2 W^-1 . To guarantee the performance of the photodetectors, the optimization of AlGaN growth and annealing condition for Schottky contacts were performed. The results show that high-temperature annealing method for Ni/Pt Schottky contacts is effective for the reduction of leakage current.     

STUDY ON BINDING PROBLEM OF Δ(1232) IN NUCLEI WITH HARTREE-FOCK METHOD

The binding problem of isobar Δ(1232) in ⁴He ¹²C and ¹⁶O systems is studied in detail by Hartree-Fock method. The OBEP is used for the nucleon-nucleon potential and the nucleon-Δ(1232) interaction. The calculated results show that Δ(1232) can be bound only in ⁴He and not in ¹²C and ¹⁶O systems.     

ANGULAR DISTRIBUTIONS OF FISSION FRAGMENTS IN INTERACTIONS OF 12C IONS WITH VARIOUS TARGETS

Angular distributions of fission fragments were measured for a series of compound nuclei formed in the bombardment of ¹⁶⁹Tm,¹⁷⁵Lu,¹⁸¹Ta,W,Re,Pt,¹⁹⁷Au,Pb and ²⁰⁹Bi by ¹²C ions with mica track detectors and gold surface barrier silicon detectors.All the measured angular distributions can be fitted satisfactorily by the theoretical formula based on saddle point model.The variation trend for K² with the excitation energy increasing was given at various ranges of the fission parameter Z²/A.