2004 Vol. 28, No. 2
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This paper gives the result of proof-of-principle study of a novel compact electron linac. In this linac, the spent beam of a high power klystron, after energy and phase selection by a magnetic field, is used for injection into an accelerator section and the klystron works in self-excited mode-of-operation. According to this proposal, many components of conventional linacs can be omitted to simplify the construction, maintenance and reduce the cost. The realization of this scheme with better affordability should promote the applications of linac.;There are several key problems that should be resolved to realize such a novel linac. The electron bunch properties, such as energy, current, emittance, etc., and the frequency stability of the klystron oscillator have to be appropriate for accelerator application. In this report, computer simulation and experimental measurements are carried out which results confirm the feasibility of the realization of this novel linac.
Many experiments have reported observations on possible correlations between the muon flux and temperature variation in the atmosphere, and especially recent MACRO and AMANDA observed apparent seasonal variation in the absolute muon rate. We report the calculation of effective temperature from Payerne meteorological data, and the simulation of temperature effect on muon flux from its representative atmosphere samples, which gives temperature coefficient α T prediction in muon threshold energy range 30 GeV up to 2000 GeV and the order of possible influence on absolute muon flux.
We use pertubative QCD to calculate the cross sections of pion virtual Compton scattering. QCD running coupling constant and different pion distribution amplitudes are explored in detail. The “work point” is defined to determine when pQCD is applicable to exclusive processes. We show that pQCD begins to work at 10 GeV2. If we relax our constraint to a weak sense, the work point may be as low as 4 GeV2.
We give an introduction to the design and coding of parallel computing for Monte Carlo simulations of lattice systems, by taking the Ising model as an example. The performance results on our PC cluster are also provided. We believe that such information is useful for large scale simulation of lattice QCD.
We analyze D+→K0K+decay at the leading order, α s corrections with the QCD factorization approach and the soft-gluon effects with the light cone QCD sum rules. We find the prediction of naive factorization is far from the experimental data, and the QCD factorization result approaches to the experimental data. However, in QCD factorization method, if we consider the soft-gluon effects, then the result is in accordance with the experimental data well. Our calculation shows that the soft-gluon contributions which are firstly calculated in D meson nonleptonic decay are noticeable. So, it can't be neglected in the decay channel.
Based on theory of constrained Hamiltonian system, the Faddeev-Senjanovic Path-integral quantization for studying the quantization of Conwall-Norton and Jackiw-Johnson models were reexamined, the canonical Ward identities were derived. The mass spectra of both fermion and bound states were also obtained, which is in agreement with that results obtained by using another method.
Properties of nuclear matter and neutron star are described in relativistic mean field theory with density-dependent effective interactions. The difference of saturated properties for nuclear matter between different effective interactions is subtle except for NL2 and TM2 which are mainly used for light nucleus. For neutron star matter, the meson field potentials calculated from different effective interactions have short odds at low-density, while the difference becomes large at high-density and increases with density. The equations of state (EOS) of neutron star given by density-dependent effective interactions DD-ME1 and TW-99 are softer than those of the other effective interactions such as NL1,NL3 and NLSH. The maximum masses calculated from different EOS are 2.0—3.0M ⊙, and the corresponding radius are 10—14km.
High-spin states in 179Au have been studied experimentally using the 149Sm(35Cl,5n) heavy-ion fusion-evaporation reaction at beam energies of 164—180MeV. Measurements of γ-ray excitation functions, X-γ coincidences and γ-γ-t coincidences were performed with 13 BGO(AC)HPGe and 3 LOAX detectors. Based on these measurements, a rotational band built on the 1/2(πi13/2) Nilsson state has been established for the first time, and this band has been assigned to 179Au according to the systematic of level structure in odd-A Au nuclei. Properties of the 1/2(πi13/2) band in odd-A Au nuclei are discussed with an emphasis on the band-head energy while changing the neutron number.
An array of 13 detector telescopes has been used for detecting small-angle particle-particle correlations in the reactions 40Ar+112,124Sn at 30MeV/u. The α-α correlation functions were extracted from two-particle coincident events. A three-body trajectory code MENEKA was used to calculate the background correlation function. The detection efficiency was calculated by using the Monte-Carlo method. After subtracting the background correlation and making the detection efficiency correction, the temperatures of 4.18±0.25 0.21 MeV and 4.10±0.22 0.20MeV are obtained from relative populations of 8Be states for the reaction systems with different isospin,40Ar+112Sn and 40Ar+124Sn, respectively. From the relationship between the state population temperature and outgoing particle energies, it is found that the emission temperature decreases with increase of the particle energies for both studied reaction systems. For the neutron deficient system 40Ar+112Sn the emission temperature is 5.13±0.30 0.26MeV for the lower emitting particle energies and 3.87±0.37 0.29MeV for the higher emitting particle energies. And for the neutron rich system 40Ar+124Sn the emission temperature is 5.39±0.30 0.26MeV for the lower emitting particle energies and 3.32± 0.28 0.23MeV for the higher emitting particle energies. This kind of isospin dependence is discussed.
The very neutron-deficient nuclide 129Pm was produced via the 92Mo(40Ca, p2n) reaction and identified for the first time by using the X-γ coincidence in combination with a He-jet tape transport system. From the decay of a 99keV γ ray which corresponds to the 5/2－→1/2－ transition in the daughter nucleus 129Nd following the (EC+β+) decay of 129Pm, the half-life of 129Pm was determined to be 2.4(6)s.
Based on the triaxial particle-rotor model (PRM), the chiral doublet bands with symmetric particle-hole configurations πg9/2νg-1 9/2, πh11/2νh-1 11/2 and asymmetric configurations πg-1 9/2νh11/2, πh -1 11/2νi13/2 have been investigated, including their rotation spectra, the relations between spin and rotational frequency, and the reduced B(E2),B(M1) transition probabilities. These configurations correspond to regions A～100, A～130 and A～170 in nuclear chart respectively. It is observed that the larger angular momentum provided by the valence nucleons, the higher the spin corresponding to the appearance of the chiral doublet bands, and the broader their spin interval. The chiral bands based on asymmetric configurations exhibit quite similar properties as those on symmetric ones, and can be discovered in future in-beam γ experiments.
Polarized deep inelastic scattering is a powerful tool for studying the internal refined information about the parton structure of the proton and deuteron. By means of the spin-dependent quark distributions in 6-quark clusters extended from a pQCD model, the polarized structure function of deuterons is investigated. Nuclear effects due to the presence of spin-1 isosinglet 6-quark clusters in the deuteron is obtained. It can be found that the calculated results with nuclear effects can better fit the SLAC E155 experimental data than that without nuclear effects.
The systematics of the even platinum isotopes are described within the framework of the Fermion Dynamical Symmetry Model. By using a pairing—plus—quadrupole type interactions, we show that the transitional behavior of these isotopes can be effectively accounted for. Good agreement is obtained between theory and data for energy levels, B(E2) values, electric quadrupole moments, gyromagnetic factors, and the isomer shifts and isotope shifts for 190—196Pt. The Calculations are also compared with various results obtained from the Interacting Boson Model. Consequently, our numerical calculation show that a very accurate effective SO(6) dynamical sysmmetry exists around 196Pt, even though the proton-neutron coupled system (SOπ(8)×SPν(6)) does not formally contain such a dynamical symmetry in the fermion dynamical symmetry model. Implications of this effective dynamical symmetry are discussed.
Based on the new measurements of total, nonelastic, elastic cross section and elastic scattering angular distributions for n+U reactions, a set of neutron optical model potential parameters is obtained in the region of incident neutron energy from 0.1 to 20 MeV. The cross sections, angular distributions, energy spectra and double differential cross sections are calculated and analyzed by optical model, nuclear fission theory, distorted wave Born approximation theory, coupled channel theory, the unified Hauser-Feshbach theory, as well as exciton model. The results indicate that our theoretical model can reasonably analysis n+ 238U reaction data with neutron energy lower than 20 MeV.
Based on the Smoluchowski equations, we study the influence of angular momentum on the shell effects of pre-scission particle emission for a light closed shell nucleus 132Sn. It has been found that the shell effects of pre-scission particle multiplicity depends on the angular momentum in a complicated way. Possible reasons are discussed.
Two methods of energy reconstruction for long column CsI(Tl) crystal detector in the TEXONO experiment, using concepts of “arithmetic mean” and “geometric mean”, have been developed. Both the principle of two methods and data analysis are discussed.
The Monte Carlo simulation software is developed based on the operating principle of CdZnTe detector, the randomicity of γ ray reaction in the detector and the statistic rule of the amount of electron-hole pairs produced. First, the reaction depth of photons is calculated based on the disintegration rule. Secondly, the reaction section of every reaction is estimated and the reaction probability of the three atoms in CZT and the probability of every reaction of every atom are calculated. Based on these probabilities, the category of atoms and the type of reactions of a photon reacting with the detector are determined and the amount of electron-hole pairs produced by the photon is obtained. From the reaction depth and the amount of electron-hole pairs produced, the amount of charge collected can be calculated.;The response energy spectra of γ ray in the CdZnTe detector are simulated by using the Monte Carlo software developed. The simulation results are well comparable with the data of the real CdZnTe devices. In addition, the ideal thickness of the device, which is of maximum detecting efficiency, is also obtained based on the analysis over the relationship between the thickness and the efficiency, assuming the device to be under the radiation of 57Co source.
The average field idea and the single particle model have been introduced, and the motion behaviours in large scale of beam particles have been disscussed for 2 Dimension crystallization beams in storage rings. It is shown that a particle orbit is the spiral line moved along z axis, and new configuration has been disclosed in the plane vertical to z axis.
The ever-increasing demand for better performance from circular accelerators requires improved methods to calibrate. beam position monitors(BPM). A beam based calibration system has been established to locate the centers of the BPM with respect to the magnetic center of quadrupole magnets.;Additional windings are applied to the quadrupole magnets to make the quadrupole magnetic strength individually adjustable and the number of the power supply of all 32 additional windings is only one. Software system has been finished to automatically measure the offsets of BPMs.;The effect of the beam-based calibration system shows that the calibration of BPM has been more quickly and accuretely.
In this paper the calibrations of different soft X-ray detector elements used in experiment diagnostics of Inertial Confinement Fusion (ICF) with Synchrotron Radiation is reported. Beijing Synchrotron Radiation Facility used special operation type with beam current 35—110mA, the storage ring electron energy 2GeV, photon energy region 50—1500eV. The performance of the light source is studied by transmission grating and face array CCD system. We divide 50—1500eV energy region in seven energy section through different material prefilter with monochromaticity than 95%. The energy response of different soft X-ray detector elements are calibrated. The calibration results are used in ICF data analysis, which secures the accuracy of data treatment.
This paper described the development of a split photon beam position monitor of HLS (Hefei Light Source). The main performances (e.g. sensitivity, position offset and linearity range) were analyzed. The performances of this device were tested, the results are well matched with the calculated results.
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