2005 Vol. 29, No. 3
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3.5MeV injector is the electron beam source of Dragon-I induction linac. Electron beam is extracted by the magnetic field from diode powered by an induction voltage adder, which is composed of pulsed power system, induction cavities, cathode/anode stem and radial insulator. Innovation is adopted in the development such as Pierce-like cathode, 800mm OD ferrite torroid and solenoids placed inside cathode/anode.Measurement shows that this injector is of high performance with output beam of 2.8kA,3.7MeV, and normalized emittance of 1040 p×mm·mrad, energy spread of 2.1%.
We have modified the field theory of soft Pomeron proposed by Landshoff and Nachtmann. Starting from the viewpoint that the constituent quark has its own structure and according to the hypothesis of the maximum non-perturbative strong interaction reactions, which should be obeyed in high energy strong soft processes, we proposed a new structure model for the soft Pomeron. A pair of constituent quarks of colliding hadrons in such processes will be resolved into a bare quark (or antiquark) and a lot of non-perturbative gluons (and quark pairs). Corresponding to such mechanism, the relevant structure of soft Pomeron is represented by the sum of a series of cutting ladder diagrams. In the multi-Regge region, where the energy s of the system is very large and its momentum transfer |t| is very small, and in the approximation where only the leading logarithm order of s are preserving, we have calculated the q-q (q) scattering amplitude and its total cross section from the sum of such ladder diagrams. The factor of Regge behavior in the exponential power law of s does arise in it. We also get a compact formula for the trajectory of soft Pomeron in our model. Some short discussions about the application for our approach to other strong-soft processes are mentioned.
We study thd radiative annihilation decay B0s,d→J/ψ γ in the framework of QCD factorization. we show that the nonfactorizable radiative correction at the order αs changes the magnitude sighificantly in comparison with the leading-order result with the naive factorization in the Standard Model.Future measurements of these decays would be useful testing the factorization framework.Rare radiative decays of B mesons received considerable theoretical attention due to their special sensitivity to physics beyond the Standard Model.As an example,we consider the effects of the admixture of right-hand charge currents to the standard left-hand current.This admixture will give a significant contribrution to the decays.
It was reported in our previous paper in 2004 that the unknown isotope 129Pm near the proton drip line was produced via the fusion-evaporation reaction 40Ca+92Mo, and a 99-keV γ line was assigned to the (EC+b+) decay of 129Pm for the first time.In order to confirm the assignment,following three new evidences were provided in this paper. (1) The excitation function of the 99-keV γ line was made from 164MeV to 190Mev of the incident energy. (2) A cross bombardment 36Ar+96Ru was carried out, from which the same 99-keV γ transition was observed.(3) The nuclear potential-energy-surface (PES) of 129Pm was calculated by using the Woods-Saxon Strutinsky method. The ground spin and parity of 129Pm was then predicted to be 5/2－. This prediction leads to a 5/2－ low-lying state in the daughter nucleus 129Nd via the (EC+b+) decay of 129Pm favorably.
The 95 MeV 19F beam projects on an enriched
Both theoretical calculations and experimental observations show that there exists proton halo in the first excited state (1/2)+ of 17F. The elastic electron scattering process off the the first excited state of 17F is studied with the RMF model and Eikonal approximation. The charge form factor is calculated and compared with those of 16O and 16F. The results show that the existence of the proton halo can lead to an obvious change to the form factors in the range of low and moderate-momentum transfer. This indicates that elastic electron-nucleus scattering can be an effective tool for a refined study of the proton-halo structure of the proton-rich nuclei.
If Jaffe and Wilczek's diquark picture for Θ5+ pentaquark is correct, there should also exist a SUF(3) pentaquark octet and singlet with no orbital excitation between the diquark pair, hence JP=12-.These states are lighter than the Θ5+ anti-decuplet and lie close to the orbitally excited (L=1) three-quark states in the conventional quark model.We calculate their masses and magnetic moments and discuss their possible strong decays using the chiral Lagrangian formalism. Among them two pentaquarks with nucleon quantum numbers may be narrow. Selection rules of strong decays are derived. We propose the experimental search of these nine additional JP=12- baryon states. Especially there are two additional JP=12- Λ baryons around Λ(1405).We also discuss the interesting possibility of interpreting Λ(1405) as a pentaquark.The presence of these additional states will provide strong support of the diquark picture for the pentaquarks. If future experimental searches fail, one has to re-evaluate the relevance of this picture for the pentaquarks.
The three dimensional Total Routhian Surface calculations are carried out to analyze the four rotational bands in 168Lu observed recently. One of these four bands is identified as tri-axial super-deformed band, which is consistent with the experimental assignment. The values of its deformation parameters are derived respectively from the analysis. The quasi-particle energy variation with the rotational frequency is explained reasonably.The reason, why the signature partner of the fourth band has not been found experimentally, is also given.
Based on the spherical optical model,the Coupled-Channels theory,the empirical formula based intranuclear cascade mechanism for nucleon emission,the exciton model,the evaporation model and the Hauser-Feshbach statistical theory with width fluctuation correction, the reaction data are calculated for p+238U in the energy region from threshold up to 200MeV,the fission widths are calculated with Bohr-Wheeler formula.The calculated results are generally in good agreement with the experimental data.
The shell effects on the particle evaporation for those nuclei near magic number,namely,204Pb,208Pb and 212Pb as well as 128Sn,132Sn and 136Sn,are investigated via a diffusion model.Calculations show that shell has an effect on the isospin dependence of particle emission, and that the magnitude of this shell effect is related to the spin and excitation energy of compound systems.It is found that angular momentum plays a significant role in the shell effects on the isospin-dependent particle emission while high excitation energy weakens such shell effects.
A chiral hadronic model is applied to the investigation of the influences of temperature on the properties of dense matter with neutrino trapping.Our results show that the proton fraction of the npeνe system is less sensitive to the variation of temperature than the npe one.The energy densities of both systems increase with temperature.Moreover,the maximum masses and Kepler frequency of protoneutron stars decrease when temperature increases.
The two-dimension positional sensitive CsI(Tl) detector is reported. The detector’s spatial resolution is 0.81mm (FWHM) and energy resolution is 0.9%(FWHM).This detector is the part of the ΔE－E telescope which is used on RIBLL.The light output of different kinds of particle is different.And the light output is not linear with the energy loss.So we should make the energy calibration of the CsI(Tl) detector by magnetic rigidity of ions and energy loss on Si detector which we know.
An experimental study of accelerated aging of BESIII drift chamber prototype with radioactive source 55Fe 5.9 keV X-ray(1.85X109 Bq)) was done. The dependence of anode current and full energy photo-electron peak of 55Fe 5.9 keV X-ray on the accumulated Q was measured. When total charge Q=0.07C/cm is accumulated (equivalent to 5 operation years of BESIII DC) the anode current is 87% of primary value and aging ratio R=-0.19%/(mC/cm) for small cell was measured.
A high-Z nuclei detector based reactor neutrino spectra measurement is being operated by TEXONO Collaboration, focusing on low energy low background experiments in Neutrino and astroparticle physics. This article reviews the data processing procedures adopted on CsI(Tl) scintillator detector array, one of the two major detectors in TEXONO project. Owing to the complications in reconstructing energy spectra from the two-end output system, two approaches are introduced to improve the resolution of the final result.
Dipole field in an RFQ accelerator exerts beam a bending force and thus results in beam losses on the machine. Measures must be taken to diminish the influence of the dipole field. Dipole stabilizer rod was proposed to shift the dipole modes far from the working quadrupole mode. In our recent measurements on a cold model RFQ, we observed some new phenomena associated with the function of dipole stabilizer rods. In this paper we report our results and give an analysis on these results. A new idea of imbalance insertion of the dipole stabilizer rods is proposed for both shifting dipole mode and reducing the dipole components in an asymmetrical RFQ.
Electron beam can be focused into a small spot with the diameter of only about nanometers theoretically,and easily controlled.It cannot be replaced by any other micro fabrication techniques in mask-making of VLSI (Very Large-Scale Integration).Based on the electron gun of SDS-3 electron beam lithography machine,the concave hyperboloid Wehnelt(oxide-coated cover)of accelerator is discussed.The electron trajectories and potential distribution are given.Electrons from the gun accelerated by a high voltage reached a target of silicon piece(In front of the aperture)via the Wehnelt.Finally,spots of E-beam in the silicon piece and the geometry schematics for Wehnelt of accelerator are given.
In this paper, the theoretical background of OTR (abbreviation for Optical Transition Radiation) is stated, the principle of applying OTR to beam diagnostics is described, the schemes of experiments on an electron beam of 18MeV, 2.7kA are presented. In intense electron beam diagnostics, there are many difficulties,such as target destruction,X-ray noise,electron-magnetic disturbance,and so an. After overcoming these difficulties,the characteristic pattern of OTR with and without polarizing glass are both obtained. The conclusion that polarizing glass should be used in beam diagnostics is deduced after analyzing the difference between the two patterns.With OTR method,the beam profile,energy,divergence are measured.OTR and Cerenkov Radiation are used simultaneously to measure the normalized beam emittance.In this experiment,OTR is used to measure the energy and divergence,and Cerenkov Radiation is used to measure the profile.
I/Q demodulation is a common and useful technique used in accelerators. This paper presents a series of methods to correct phase errors based on the theories of the analog I/Q demodulator, which can correct various errors effectively. And based on this, we have done the relative experiments.
In order to compensate the RF phase drift due to various factors,we will establish a RF phasing system for BEPCII linac. Energy maximizing method will be used to determine the RF phase of each RF power source. A coaxial line will be used to distribute RF phase reference along the klystron gallery.The key components,such as PAD unit, IφA units, have been developed.A minimum phasing system is established and runs successfully.
In this paper, a set of imaging plate powder diffraction equipment for Synchrotron radiation were reported. The error sources of the equipment was discussed in detail. The results demonstrated that the set of equipment satisfied the experimental requirements and completely applied to the powder diffration experiments.
The Schrödinger equation for a type of artificial atom is solved,the expressions for the energy levels and the electron wave functions of this type of artificial atom are presented,and the Rydberg states of the artificial atom are also discussed in detail.
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