## 2005 Vol. 29, No. 11

column

Display Method:          |

2005, 29(11): 1027-1032.
Abstract:
In the context of topcolor-assisted techicolor (TC2)model, we study the contributions of the neutral top-pion π0t to the lepton flavor violation (LFV) processes li→ljγ,li→ljlkll and t→clilj respectively. We find that the present experimental upper bound for μ→eγ gives severe constraints on the free parameters of the TC2 model. Under these constraints,we consider the processes li→ljlkll and t→c lilj generated by π0t exchange at the tree-level and the one loop level. Our numerical results show that the neutral top-pion π0t can enhance the branching ratios of these processes by several orders of magnitude. Some of those processes might be used to detect the possible signals of π0t in the futrue high energy experiment.
2005, 29(11): 1033-1040.
Abstract:
The role of the auxiliary scalar field φ of BD theory in baryon number asymmetry is discussed in this paper. We consider a derivative coupling of this gravitational scalar field to the baryon current JμB or the current of the baryon number minus lepton number JJμB-L based on a series of works of R.Morganstern about the Brans-Dicke cosmology. We find that the spontaneous baryogenesis by this coupling is able to yield sufficient baryon asymmetry nB/s～10-10 provided the time of the grand unification is a little bit earlier. In addition,Davoudiasl et al have recently introduced a new type of interaction between the Ricci scalar R and the bayon current Jμ, \partial_{\upmu}R Jμ and also proposed a mechanism for baryogenesis, the gravitational baryogenesis. However, the Einstein equation tells us that R=0 in the radiation-dominated epoch of the standard FRW cosmology. In this paper we reconsider the feasibility of having gravitational baryongenesis with such a form of interaction in radiation-filled BD cosmology. We show that R does not vanish in this case and the required baryon number asymmetry can also be achieved.
2005, 29(11): 1041-1046.
Abstract:
It is expected that a radioactive 9C-ion beam as a type of double irradiation source can increase the curative effect when applying it to heavy-ion cancer therapy,and it has been proved in our previous radiobiological experiment that the relative biological effectiveness (RBE) at the depths around the Bragg peak of a 9C beam was greater than that of a therapeutic 12C beam at least by a factor of 2. To characterize the physical basis of a 9C ion beam applying to radiotherapy, a spherical tissue-equivalent proportional counter (TEPC) was used to measure the lineal energy (y) spectra at different depths along a radioactive 9C-ion beam in this work. Based on the measured spectra, the distribution of dose-averaged lineal energy in depth was derived.Moreover, the measured lineal energy spectra were converted into the distributions of LET in absorbed dose at the different depths. The distribution of dose-averaged LET in depth, therefore, has been obtained for the 9C beam. The dose-averaged LETs measured with the TEPC and our preceding parellel-plate proportional counter (PPPC) were compared. It has been found that both the measurements agreed well with each other at the entrance channel of the 9C beam while the dose-averaged LETs by the TEPC were larger than those by the PPPC around the Bragg peak, i.e. the stopping region of the incident 9C ions. This coincides with the expectation that all of the delayed alpha particles and protons,which are emitted isotropically during the decays of the 9C ions, can be included by means of the TEPC measurement. The data sets obtained in this work provide a substantial physical basis for revealing the advantages of 9C beams in cancer therapy.
2005, 29(11): 1047-1051.
Abstract:
Using heavy-ion nuclear reaction and in-beam γ-ray spectroscopy technique,high spin states of 136La have been studied. The nuclear reaction used is 130Te(11B,5n) with a beam energy 60MeV. The level scheme with three collective band structures has been updated with spin up to 20h. The collective backbending has been observed in $\uppi h_{11/2}\otimes \upnu h_{11/2}$ band. According to the TRS calculations，this backbending is due to the alignment of a pair of h11/2 neutrons. The signature splitting and inversion for the $\uppi h_{11/2}\otimes \upnu h_{11/2}$ band were also discussed. Other two bands based on $12^-$ and $16^+$ levels were proposed as oblate deformation with $\gamma\approx -60^\circ$. They most probably originate from four- and six- quasiparticle configurations, that is,$\uppi h_{11/2}\otimes\upnu g_{7/2} h_{11/2}^2$ and $\uppi g_{7/2}\otimes\upnu g_{7/2}^2 d_{5/2}h_{11/2}^2$ respectively.
2005, 29(11): 1052-1056.
Abstract:
The reaction cross section, together with the one-, two- and three neutron removal cross sections, of 17C with the energy of 79A MeV on carbon target were measured using the radioactive beam line RIPS of RIKEN. The reaction cross section and the one-neutron removal cross section were analyzed within the frame of Glauber model. Both the analyses favor the dominant configuration of a 16C core (2+) plus a d5/2 valence neutron for 17C. The work for the neutron-rich carbon isotope on the reaction cross section σR and the interaction cross section σI on 12C target are summarized.
2005, 29(11): 1057-1060.
Abstract:
Cross-sections for 84Sr(n, 2n)83Sr, 86Sr(n, 2n)85mSr,86Sr(n, 2n)85Sr,88Sr(n, 2n)87mSr,84Sr(n, p)84Rb,86Sr(n, p)86Rb, 88Sr(n, p)88Rb and 88Sr(n,α)85mKr reactions were measured at neutron energies from 13.5 to 14.6MeV using activation technique and γ-ray spectrometry. The neutron flux was determined using the monitor reaction 93Nb(n, 2n)92mNb and the neutron energies were measured by the method of cross section ratios for $^{90}$Zr(n, 2n)$^{89m+g}$Zr to $^{93}$Nb(n, 2n)$^{92m}$Nb reactions. The results of present work were compared with data published previously.
2005, 29(11): 1061-1066.
Abstract:
The finite temperature Brueckner-Hartree-Fock (FTBHF) approach is extended by introducing a microscopic three-body force. Within the extended approach, the three-body force effects on the equation of state of hot nuclear matter and its temperature dependence have been investigated. The critical properties of the liquid-gas phase transition of hot nuclear matter have been calculated. It is shown that the three-body force provides a repulsive contribution to the equation of state of hot nuclear matter. The repulsive effect of the three-body force becomes more pronounced as the density and temperature increase and consequently inclusion of the three-body force contribution in the calculation reduces the predicted critical temperature from about 16MeV to about 13MeV. By separating the contribution originated from the 2σ-exchange process coupled to the virtual excitation of a nucleon-antinucleon pair from the full three-body force, the connection between the three-body force effect and the relativistic correction from the Dirac-Brueckner-Hartree-Fock has been explored. It turns out that the contribution of the 2σ-NN part is more repulsive than that of the full three-body force and the calculated critical temperature is about 11MeV if only the 2σ-NN component of the three-body force is included which is lower than the value obtained in the case of including the full three-body force and is close to the value predicted by the Dirac-Brueckner-Hartree-Fock (DBHF) approach. Our result provides a reasonable explanation for the discrepancy between the values of critical temperature predicted from the FTBHF approach including the three-body force and the DBHF approach.
2005, 29(11): 1067-1070.
Abstract:
The density dependent relativistic hadron field theory is extended to inclusions of pentaquark Θ+. We have investigated the mass modifications of nucleons and pentaquark Θ+ in the framework of relativistic mean field theory. We find that the effective mass, of either the nucleon or the pentaquark Θ+ decreases as baryon density increases. We have studied the effects of the fractions of Θ+ and neutron on the baryon masses. We also discussed the relations between scale density ρS and vector density ρB at different baryon fractions.
2005, 29(11): 1071-1076.
Abstract:
Analyzing methods on the angular resolution of lead-scintillating fiber electromagnetic calorimeter are studied. The space resolution function, which is used to calculate weights,is extracted from Monte-Carlo simulation. Better angular resolution was obtained from the beam test data of AMS ECAL in 2002 at CERN, when the space resolution function was used in the fit. Different ways to calculate the centers of gravity,to choose the layers to fit the incidence direction are also discussed.
2005, 29(11): 1077-1080.
Abstract:
For achieving high average current electron beams, we need to eliminate charge-induced fields in superconducting cavity. In order to manufacture effective high order modes (HOM) coupler, we study the HOM that are excited possibly in the Peking University 1+1/2 Cell superconducting cavity. With Code HFSS, we have calculated 31 HOMs' parameters, which fit the experimental data very well. We also compared the parameters to the results calculated from Superfish code, and we got a good match, proving HFSS is a reasonable simulation code for superconducting cavity.
2005, 29(11): 1081-1085.
Abstract:
An impedance measurement system has been established to measure the longitudinal coupling impedance of vacuum components for the BEPC upgrade project(BEPCⅡ). The measurement system is based on the traditional coaxial wire methods. The measurements are done in frequency domain taking advantage of the HP/Agilent microwave vector network analyzer 8720ES. Two kinds of techniques, the TRL calibration and using a reference line, were investigated and applied to the practical measurements. This paper introduces this impedance measurement system and the results of the measurements. As a comparison, we also give the numerical simulations of the RF-shielded bellows for BEPCⅡ.
2005, 29(11): 1086-1090.
Abstract:
The medium-energy beam-transport line (MEBT) plays an important role in reducing the beam loss in the Japan Proton Accelerator Research Complex (J-PARC). A MEBT was designed and constructed,with good beam matching and lower beam loss. A brief introduction to the MEBT and its beam test results are given. To further reduce the beam loss during the transient time of the chopper,a medium-energy beamtransport line with an anti-chopper has been designed. It accomplishes three tasks: matching the beam from the RFQ to the acceptance of the DTL, chopping the beam to produce gaps for injection into the rapid cycling ring which follows the linac, and returning the partially deflected beam back to the acceptance of the DTL. An RF chopper and an anti-chopper have been adopted in the beam line, and the optimization of the design of the chopper cavity is discussed. Details of the beam dynamics analysis are given.
2005, 29(11): 1091-1094.
Abstract:
To design the coupler of one kind of thermionic cathode microwave electronic gun, we apply the energy method'',which calculates the coupler factor between the waveguide and cavities of the electronic gun. So we can design the geometry size of the coupling iris. MAFIA code is used. Comparing with the experiment results,the simulating results is in agreement with measurement about 10%—30% deviation. Energy method'' is an efficient and simply method to calculate the coupler factor between cavities and waveguide.
2005, 29(11): 1095-1099.
Abstract:
The technology using optical transition radiation (OTR) which is a main method for measuring the electron beam of high energy and high current has been developed for the past ten years．OTR characterized by the ultra-fast response，high resolution and capability of measuring both spatial and angular profiles of an electron beam．It also can measure the beam energy and divergence．A time-resolved measurement results of an electron beam produced by linear induction accelerator (LIA) can provide much more detail information so that many problems about the beam transmission can be known well．Such a time-resolved measurement system has been developed recently in our lab and put into operation．It provides an on-line beam diagnostic method for a 18.5MeV, 2kA, 90ns electron pulse．The beam emittance and its variation during the 90ns pulse are obtained in 10ns time interval．This system can capture 8 frame images at one time in the minimum interval period of 10ns while the exposure time is 3ns．The frame interval time is 8 level which changes from 10ns to 1280ns in power of 2 and the exposure time can change in three level of 3ns, 5ns, 10ns．The size of image is 1376×1035 and the object plane size can reach φ80mm.
2005, 29(11): 1100-1103.
Abstract:
The construction of CSR (cooling storage ring) which includes a main ring (CSRm) and an experimental ring (CSRe) will be finished at the end of 2005. Heavy ions of carbon to uranium will be accelerated up to 900MeV/u and 400MeV/u at intensity of 108 pps. The HIRFL (heavy ion research facility in Lanzhou) will be used as the injector. For the shielding design of CSR, the secondary neutrons due to the ion beam loss, their spectra and angular distributions were estimated based on the experimental results. The dose equivalent outside the shielding surface and in the surrounding environment and the neutron skyshine dose equivalent were also estimated in this study. The experimental result, neutron yield, spectrum and angular distribution for 400MeV/u 12C+Cu reaction were used for estimating the source term of shielding design. It is found that the most important environmental radiation impact component of CSR is the skyshine neutrons.
2005, 29(11): 1104-1106.
Abstract:
The grazing exit X-ray fluorescence provides a possibility to analyze the characteristics of thin film and multilayer, especially the thickness, interface structure and composition.The Cr film samples with different thickness deposited on silicon (Si) bases are tested with grazing method using Beijing synchrotron radiation source (SR) as excitation light.The results agree with the theoretical prediction, and the interference of emitted X-ray has been observed.
2005, 29(11): 1107-1111.
Abstract:
The effects of additional vacancy-like defects on thermal diffusion of B atoms in silicon were investigated by using secondary ion mass spectroscopy. B atoms were introduced into silicon by 30keV B ion implantation at a dose of 2×1014cm－2, while the additional vacancy-like defects were produced by two different ways. One was via 40 or 160keV He ion implantation at a dose of 5×1016cm－2 and followed by an annealing at 800°C for 1h, which produced a well-defined cavity band near the projected range of He ions. The other was via 0.5MeV F or O ion implantation at a dose of 5×1015cm－2,which creates excess vacancy-like defects around the 1/2 projected range of F or O ions. Our results clearly show that the additional vacancy-like defects could suppress the boron diffusion during subsequent thermal annealing at 800°C for 30 min. The suppressing effects were found to depend on both the ion type and ion energy. The results were qualitatively discussed in combination with the results obtained by using transmission electron microscopy and Rutherford backscattering spectroscopy.
2005, 29(11): 1112-1114.
Abstract:
In the present work the photoluminescence (PL)character of sapphire implanted with He ions and subsequently irradiated with 208Pb27+ of 1.1MeV/u was studied. Sapphire single crystals were implanted with 110keV He ions at 600K temperature to fluences ranging from (0.5 to 2)×1017 ions/cm2, some of them were subsequently irradiated with 208 Pb27+.From experimental results we found PL spectra peaks at 375nm, 413nm, and 450nm, and it's intensity gets maximum at fluence of 5×1016 He ions/cm2. Also we found a new peak at 390nm after subsequent 208 Pb27+ irradiation, which is possibly due to the crystallized sediment containing nano crystal Al2O3 appeared on the sample surface.
2005, 29(11): 1115-1120.
Abstract:
In recent years, the velocity dependence of the damage cross section, the damage efficiency and the damage morphology of solid materials induced by swift heavy ions, named ion velocity effect,is observed. But the mechanism or origin of the ion velocity effect is not clear up to now.In this paper, the discovery, current researching situation and some typical experimental results of ion velocity effect in the process of the damage creation in solids induced by swift heavy ion irradiations were briefly described, and the main theoretical explanation of ion velocity effect was also reviewed and discussed in short words.
IF: 5.861

Monthly founded in 1977

ISSN 1674-1137 CN 11-5641/O4

Original research articles, Ietters and reviews Covering theory and experiments in the fieids of

• Particle physics
• Nuclear physics
• Particle and nuclear astrophysics
• Cosmology
Author benefits
News
Meet Editor