2008 Vol. 32, No. S2
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We briefly introduce the current status and progress in the field of radioactive ion beam physics and the study of super-heavy nuclei. Some important problems and research directions are outlined, such as the sub-barrier fusion reaction, the direct reaction at Fermi energy and high energies, the property of nuclei at drip-lines, new magic numbers and new collective motion modes for unstable nuclei
and the synthesis and study of the super-heavy nuclei.
The status of heavy-ion cancer therapy has been reviewed. The existing and constructing heavy-ion beam facilities for cancer therapy in the world are introduced. The first clinical trials of superficially placed tumor therapy at heavy ion research facility in Lanzhou (HIRFL) are presented.
We calculated the relative abundances of charge hadron, KS0, Λ and Λ in the near-side and away-side cones correlated with triggered high pT particles in minimum bias in p+p collisions at √sNN=200 GeV in the PYTHIA model. From the quark and gluon jet events in the PYTHIA model, we have found that the particle yields' different splitting. So the di-hadron correlation in the quark jet events and gluon jet events are also presented. And the particle charge dependance of the di-hadron correlation is extracted from the PYTHIA model. The di-hadron plus and di-hadron minus correlations are similar in the near-side (Δφ~0), but in the away-side, the di-hadron minus correlation seems to be lower. The Hadron-KS0 and －Λ+Λ correlations seem to be differet. We have used a double-Gaussian function to fit those correlation functions and compared the fit parameters.
Uranium on uranium target (U+U) collision experiment has been proposed to be performed on Cooling Storage Ring (CSR), External Target Facility (ETF), which is to be built at Lanzhou, China, delivering the uranium beam up to 520 MeV/nucleon. It is predicted that the tip-tip U+U collision patterns can produce significant high baryon density and long duration nuclear matter to study the nuclear Equation of State (EoS). As the random orientation in U+U collisions, it is necessary to select the interested tip-tip events from the large trivia background. A Relativistic Transport (ART1.0) Model is applied to compute the random mini-biased U+U collisions to select our most favorable tip-tip events. It is found that applying various combination cut on the forward neutron multiplicity and forward charged particle multiplicity of the random U+U mini-biased sample, we can select the tip-tip configuration with certain purity and efficiency.
The non-central Au+Au collision at center-of-mass energy √sNN=200 GeV is simulated using AMPT model. It is found that both the integral and differential elliptic flow behaves differently for partons freezing out at different stages. It is shown that the integral elliptic flow of freeze-out partons decreases with time at the early stage, but increases with time at the late stage. The curve of transverse momentum distribution of elliptic flow of partons is more flatter at the early stage than at the late stage. The effect of surface emitting on elliptic flow is argued to be not neglectable.
Using a multisource ideal gas (MSIG) model, we reconstruct the transverse emission source in the momentum space for light fragments produced in reactions 86Kr-124Sn at 25 MeV/nucleon and b=7—10 fm based on the theoretical predictions of the Isospin-Dependent Quantum Molecular Dynamics (IDQMD) model. We show that the MSIG model can reasonably describe the IDQMD-predicted results for the azimuthal distribution and the transverse momentum dependence of elliptic flow v2 and fourth-order anisotropic flow v4 but can only qualitatively describe the transverse momentum spectra. The azimuthal distributions of nuclear fragments produced in heavy-ion collisions at intermediate energies are studied by the MSIG model. The calculated results are compared and found to be in agreement with the experimental data of Ca-Ca, Nb-Nb, and Au-Au collisions at 150—800 MeV/nucleon beam energies. Meanwhile, the angular distributions of pions and kaons produced in heavy-ion collisions at the low-energy end (1—2 GeV/nucleon) of high energies are investigated by the MSIG model, too. The calculated results are compared and found to be in agreement with the experimental data of the KaoS Collaboration.
The predictions of the directed collective flow by using the relativistic quantum molecular dynamics model are presented for the heavy-ion reactions at HIRFL-CSR energies. The directive flow value as a function of the emitting nucloen rapidity in the center-of-mass system is calculated with the azimuthal
event plane method and two-particle angle correlation method, respectively.
Comparing the rapidity dependence of directed flow in different freeze-out
time windows, the evolution and development of the directed flow is investigated. We find that one can reliably obtain the earlier information of the emitting source at this energy by time analysis of the directed collective flow.
Such an analysis is useful to the designing of the hadron detector at CSR.
We introduce and summary our research progress on the effective masses of K meson in dense nuclear matter.
The longitudinal momentum distribution (P//) of fragments after one-proton removal from 23Al and reaction cross sections (σR) for 23,24Al on carbon target at 74A MeV have been measured simultaneously. An enhancement in σR is observed for 23Al compared with 24Al. The full width at half maximum of the P// distribution for 22Mg fragments has been determined to be 232±28 MeV/c. Analysis of P// using the Few-Body Glauber Model indicates a dominant d-wave configuration for the valence proton in the ground state of 23Al. The exotic structure in 23Al is discussed.
Some experimental techniques and theoretical analysis on unbound nuclei structure study are briefly introduced in this article. The unbound nuclei structure investigation can inspect the reliability of theoretical calculation, and is also important to extend the modern nuclear structure model to exotic nuclear regions. With the recent development of radioactive Ion Beam (RIB) facility and some new experimental methods, the structure of unbound nuclei near drip line can be studied in experiment.
The β-delayed neutron and γ spectra of neutron-rich nucleus 21N using β-γ and β-n coincidence measurements were presented in this paper. Thirteen new neutron groups ranging from 0.28 MeV to 4.98 MeV and with a total branching ratio 88.7±4.2% were observed. One γ transition among the excited states of 21O, and four γ transitions among the excited states of 20O were identified in the β decay chain of 21N. The ungated half-life of 83.8±2.1 ms was also determined for 21N.
The structures of N=7 and N=8 isotones in Be-F mass range are investigated in the framework of the single-particle shell model. Different from the traditional potential terms, the l2 coupling is included in the average nuclear potential. Calculations give a unified description for the structures of all studied nuclei. The neutron s-p level inversion in 11Be and proton s-d level inversion in 16F are simultaneously reproduced. In addition, the neutron halo structures in 11Be(2s1/2) and 11Be(1p1/2) are obtained. The proton halo in the first-excited state of 17F is also discussed.
Experimental data of nuclear β+-decay half-lives are systematically analyzed and investigated. We present an exponential law between the half-life of β+-decay with the same forbiddenness and the nucleon number (Z,N) of parent nucleus far from the β-stable line. A formula with four parameters is proposed to describe the β+-decay half-lives of nuclei far from stability. Experimental β+-decay half-lives of the first and second forbidden transitions are well reproduced by this simple formula. The physics of the exponential law is related to the statistical properties of β+-decay far from β-stable line.
The basic process of an exotic decay mode namely β-delayed fission is simply introduced. The progress status of the study in the world is essentialized. The observation of β-delayed fission of 228Ac is reported. The radium was radiochemically separated from natural thorium. Thin Ra sources in which 228Ac was got through 228Ra →β－228Ac were prepared for observing fission fragments from β-delayed fission of 228Ac. They exposed to the mica fission track detectors, and measured by an HPGe γ-ray detector. The β-delayed fission events of 228Ac were observed and its β-delayed fission probability was found to be (5±2)×10－12.
A thick natural uranium target was bombarded with a 60 MeV/u 18O beam. The neutron-rich isotope 230Ra as the target residue was produced through the multinucleon transfer reaction(238U-4p-4n). The barium and radium fraction as BaCl2 precipitate were radiochemically separated first from the mixture of uranium and reaction products. Then, the radium fraction was separated from BaCl2 precipitate by using cation exchange technique. The γ-ray spectra of the Ra fraction were measured using an HPGe detector. The production cross sections of 230Ra were obtained by a combination of the radiochemical separation technique and off-line γ-ray spectroscopy. The cross section of 230Ra has been determined to be 66±20 μb.
This paper described the nuclear astrophysical studies using the unstable ion beam facility GIRAFFE in CIAE, by indirect measurements. We measured the angular distributions for some single proton or neutron transfer reactions, such as 7Be(d,n)8B, 11C(d,n)12N, 8Li(d,p)9Li and 13N(d,n)14O in inverse kinematics, and derived the astrophysical S-factors or reaction rates of 7Be(p,γ)8B, 11C(p,γ)12N, 8Li(n,γ)9Li, 13N(p,γ)14O by asymptotic normalization coefficient, spectroscopic factor, and R-matrix approach at astrophysically relevant energies. Some most recent progress of nuclear astrophyiscal work in CIAE are also summarized.
We have developed the formula and the numerical code for calculating the rearrangement contribution to the single particle (s.p.) properties in asymmetric nuclear matter induced by three-body forces within the framework of the Brueckner theory extended to include a microscopic three-body force (TBF). We have investigated systematically the TBF-induced rearrangement effect on the s.p. properties and their isospin-behavior in neutron-rich nuclear medium. It is shown that the TBF induces a repulsive rearrangement contribution to the s.p. potential in nuclear medium. The repulsion of the TBF rearrangement contribution increases rapidly as a function of density and nucleon momentum. It reduces largely the attraction of the BHF s.p. potential and enhances strongly the momentum dependence of the s.p. potential at large densities and high-momenta. The TBF rearrangement effect on symmetry potential is to enhances its repulsion (attraction) on neutrons (protons) in dense asymmetric nuclear matter.
We calculate the in-medium nucleon-nucleon scattering cross sections from the G-matrix using the Dirac-Brueckner-Hartree-Fock (DBHF) approach. And we investigate the influence of the different representations of the $G$-matrix to the cross sections, the difference of which is mainly from the different effective masses.
The neutron 3PF2 pairing gap in pure neutron matter, neutron 3PF2 gap and neutron-proton 3SD1 gap in symmetric nuclear matter have been studied by using the Brueckner-Hartree-Fock(BHF) approach and the BCS theory. We have concentrated on investigating and discussing the three-body force effect on the nucleon superfluidity. The calculated results indicate that the three-body force enhances remarkably the 3PF2 superfluidity in neutron matter. It also enhances the 3PF2 superfluidity in symmetric nuclear matter and its effect increases monotonically as the Fermi-momentum kF increases, whereas the three-body force is shown to influence only weakly the neutron-proton 3SD1 gap in symmetric nuclear matter.
We study the hadron-quark phase transition in the interior of neutron stars. The relativistic mean field (RMF) theory is adopted to describe the hadronic matter phase, while the Nambu-Jona-Lasinio (NJL) model is used for the quark matter phase. We investigate the influence of the hadronic equation of state on the phase transition and neutron star properties. It is found that a neutron star possesses a large population of hyperons, but it is not dense enough to possess a pure quark core. Whether or not the mixed phase of hadronic and quark matter appears in the center of neutron stars depends on the RMF parameters used in the calculation.
We study the medium modifications of nucleon properties in nuclear matter and finite nuclei. The nucleons are described as nontopological solitons, which interact through the self-consistent exchange of scalar and vector mesons. The model adopted incorporates explicit quark degrees of freedom into nuclear many-body systems, and it can provide satisfactory results on the properties of nuclear matter and finite nuclei.
We study the influence of strong magnetic fields on antikaon condensation in neutron star matter using the quark-meson coupling (QMC) model. The QMC model describes a nuclear many-body system as nonoverlapping MIT bags interacting through the self-consistent exchange of scalar and vector meson mean fields. It is found that the presence of strong magnetic fields alters the threshold density of antikaon condensation significantly. The results of the QMC model are compared with those obtained in a relativistic mean-field (RMF) model.
We calculate the charge form factors of the even-even isotopes on the Z=20 and 28 isotopic chains, including both the stable nuclei and unstable ones, and investigate the influences of the change of neutron number on the charge form factors of the Ca and Ni isotopes systematically with the relativistic eikonal
approximation associated with the self-consistent relativistic mean field model. We find that the charge form factor changes significantly and regularly with the variation of neutron number. The charge form factors shift outward and downward as the nucleus moves from the very neutron-rich region to the very proton-rich region along an isotopic chain. The significant shift shows that the charge form factor is very sensitive to a change of neutron number. The regularity of the variation of the charge form factors along an isotope chain may suggest certain laws which rules the influence of the neutrons on the distribution of the protons. The calculations will provide a useful reference for the future experiments as well as a test of the reliability of the relativistic mean field model for unstable nuclei far from the stability line.
With the CDCC approach, the reactions induced by weakly bound nucleus deuteron are studied. By comparing the results from CDCC approach and spherical optical model with our global deuteron optical potential, we find that it is reasonable and valuable for CDCC approach in a large energy range and nuclei range.
Based on the urgent requirement of the (n,γ) reaction cross-section in the energy range of keV~MeV, 4π gamma total absorption facility (GTAF) is being constructed at China Institute of Atomic Energy (CIAE). In this paper, firstly the review of historic experimental facilities over the world is presented, and then measurement method of GTAF is described. Finally, the structure requirement for GTAF is presented. Neutron capture reactions are the key process of nucleosynthesis in astrophysics beyond iron element. The application of such facility will improve the experimental condition for the research of (n,γ) reaction.
In this paper we study collective motion under random two-body interactions in the fermion dynamical symmetry Model (FDSM). It is found that a Hamiltonian with the SO(8) symmetry of the FDSM does not give generic vibration and rotation under random interactions while that with the SP(6) symmetry does.
Projected SD-pair shell model is used to study the collectivity of low-lying state for even-even Xe isotopes. It is found that the collectivity can be reproduced in term of a three-parameter Hamiltonian.
The yrast bands of 51,52,53Fe have been studied with a microscopical effective Hamiltonian derived from the charge-dependent Bonn NN potential. Calculations obtain satisfactory agreements with experimental data, reproducing the observed isomeric states. The possible origins of the isomers are discussed.
By using a new five-parameter formula derived from the WKB approximation, we systematically calculate the spontaneous fission half-lives of even-even nuclei with Z=90—108. The isospin effect is taken into account in the new formula. The calculated half-lives agree well with the experimental data. In addition, we predict the spontaneous fission half-lives of superheavy nuclei with Z=108—114. Our predictions may provide references for future experiments.
The high spin states of 106Ag were populated via the fusion-evaporation reaction 100Mo(11B,5n)106Ag at a beam energy of 60 MeV. A new level scheme of 106Ag is presented. The positive parity band based on the configuration of πg9/2⊙ν[h211/2(g7/2/d5/2)] is assigned to magnetic rotation band of shears mechanism. Theoretical calculation of the effective interaction on the basis of TAC mode were also performed, the calculated results agrees well with the value extracted from the experiment.
The high spin states of 112In have been populated via the 110Pd(7Li,5n)112In reaction with a beam energy of 50 MeV. By analyzing the γ-γ coincidence relations and DCO ratios of γ transitions，A new level scheme of 112In including seventy-four new gamma transitions and six new bands up to the excitation energy of 6.8 MeV has been presented.
Recent progress in research on octupole deformation around Z=56, N=88 neutron-rich nuclei by our cooperative groups of Tsinghua University, Vanderbilt University and Lawrence Berkeley National Laboratory has been introduced. The experiment was carried out by measuring the prompt γ-rays in spontaneous fission of 252Cf with the Gammasphere detector array. The new results of
high spin states in 143La and 148Ce have been obtained and the octupole deformation bands are identified in both nuclei. The important structural characteristics have been discussed.
High-spin isomeric states in proton-rich A~190 nuclei have been investigated using configuration-constrained calculations of potential-energy surfaces. The calculations reproduce reasonably the experimental data, and predict shape coexistence of high-spin isomeric states in light Po isotopes.
High-spin states of 160Tm have been studied through the 146Nd(19F, 5n) reaction at a beam energy of 102 MeV. The previously known πh11/2⊙νi13/2 yrast band and πh11/2⊙νh9/2 side band are confirmed, and several low-lying levels are observed. A 4-quasiparticle band feeding into the yrast band based on the πg7/2⊙νh9/2⊙νi13/22 is suggested. Other two bands are observed and assigned to be based on the πd3/2⊙νi13/2 and πg7/2⊙νi13/2 configurations, respectively.
The criteria for chiral doublet bands based on one particle and one hole coupled to a triaxial rotor have been summarized. Candidate chiral doublet bands in A~100 and 130 odd-odd nuclei were checked against these chiral criteria. Two representative cases, nearly degenerate ΔI =1 doublet bands in 126Cs and 106Rh were investigated in the two quasiparticles coupled with a triaxial rotor model. After including the pairing correlation, good agreement has been obtained between the calculated results and the data available, which supports the interpretation of observed doublet bands as chiral bands.
The high spin states of 129Ce have been populated via heavy-ion fusion evaporation reaction 96Mo (37Cl, 1p3n) 129Ce. The comparison between the signature- and B(M1)-staggering defined by Hagemann and Hamamoto have been showed in the negative-parity band of 129Ce. The lifetimes and quadrupole moments Qt of the high spin states of 129Ce have been extracted from the line shape analyses using Doppler shift attenuation method (DSAM). The deformation parameters extracted through the solution of equations for quadrupole transition moments Qt and collective moments of inertia JRR.
The high-spin states of 110Ag were populated via fusion evaporation reaction 110Pd(7Li, 2p2n)110Ag and a new level scheme has been presented. The systematics of signature splitting and signature inversion of the πg9/2⊙νh11/2 configuration band in Ag isotopes are studied. The spin of inversion point decreases with increasing neutron number and this feature is explained as due to the competition between the p-n residual interaction and the Coriolis force.
The excitation spectra of nuclei in the regions 150156Gd. Also we have shown the result of the nucleus 102Ru which is given as an example of the reverse transition, i.e., vibration to rotation. The TRS plots reveal that, as the spin increases up the band, the former nucleus becomes slightly soft in γ and β direction, whereas the latter becomes rigid in γ direction.
We have employed the shell model and Skyrme-Hartree-Fock methods to investigate the structure of the neutron-rich nucleus 19N. The level scheme of 19N from the shell-model calculation with the WBT interaction is displayed. The potential-energy-surface calculation with the SGII interaction implies that 19N should be a deformed nucleus. The theoretical β-decay half life of 19N reproduces well the available experimental data.
Shape coexistence appears in the region of superheavy nuclei. Calculations for the nobelium isotopes have been carried out with the cranking TRS model. It shows that normal deformed and superdeformed prolate shapes coexist. Particularly for the nuclei 248,250No, the ground states are superdeformed. The kinematic moments of inertia are calculated and they agree well with available experimental results. As rotational frequency increases, the
Routhians of the superdeformations decrease and the superdeformed shapes will become yrast states at high spins.
The effects of the spin-orbit interaction in exotic nuclei are investigated by studying the binding energies and deformations of Si, S and Ar isotopes. The calculations were obtained by Skyrme-Hartree-Fock model with various spin-orbit potentials. The results reveal that spin-orbit potential is important in neutron rich nuclei.
The reflection asymmetric shell model (RASM) has been applied to describe the
alternating-parity rotational bands in neutron-rich 142,144,146,148Ba octupole nuclei. The calculated rotational bands are in good agreement with the available experimental data. The parity splitting and the parity inversion are also reproduced by the present calculation.
If is there enhanced sensitivity to variations of fine structure constant, nucleon mass and meson masses in the transition between the low energy and long-lived nuclear isomer and ground states? To answer this open problem, we investigate the transition between the long-lived 7.6±0.5 eV isomer and ground states in 229Th based on the formulae derived from both the Nilsson model and Feynman-Hellmann theorem. Consistent conclusions are drawn by these two method. The sensitivity to relative variation of fine structure constant could be enhanced by 3—4 orders of magnitude, and to variations of nucleon mass and meson masses are enhanced by about 5—6 orders of magnitude in the 229Th transition.
The measurement of the electromagnetic polarizabilities have been given extensive attention, which is also a fresh field of the experimental nuclear physics. Now we will use the method - the light nucleus scattered by the heavy nucleus at energies below the Coulomb barrier to precisely and systematically measure the polarizabilities of the light nucleus. We hope we can solve the inconsistency among the results of the 3He polarizabilities and extract the 4He polarizabilities by our experiment. It is useful to mention that our experiment now is a supplement to the future experiment on SLEGS.
The magnetic-rotational band in 85Zr was populated by the fusion-evaporation reaction 60Ni(28Si, 2pn)85Zr with a 98 MeV Si beam from the HI-13 tandem accelerator at China Institute of Atomic Energy. The g-factors of the high spin states of this magnetic rotation band in 85Zr were measured by the TMF-IMPAD method for the first time. The measured g-factors decrease with the increasing of spin. It implies that the valence neutron alignment is more rapid than that of the valence proton, which leads to a decrease of g-factors along the band.
The spin polarized β-emitting mirror nuclei 12B(Iπ=1+,T1/2=20.18 ms) and 12N(Iπ=1+,T1/2=11 ms) are produced by the low nuclear reactions 11B(d, p) 12B and 10B(3He,n) 12N and by selecting the projectile energy and the recoil angle. Their magnetic moments are measured by the β-NMR technique. The magnetic moments obtained after Knight shift correction are μ(12B)=1.001(17) μN and μ(12N)=0.4571(1) μN. The calculation using the existing shell model could not reproduce the measured magnetic moments for 12B and 12N simultaneously.
A prototype of accurate/advanced radiotherapy treatment planning and quality assurance system (ARTS) is developed and key technical issues related to the improvement of the treatment accuracy is studied. After a brief introduction to the prototype of ARTS, the advanced development in key technical issues is presented, including image data processing and human body modeling, fast and accurate hybrid dose calculation, multi-objective optimization of inverse planning, intelligent patient positioning, and dose verification.
A facility has been constructed for research of charged particle emission
induced by fast neutron reactions ((n, x) reaction) based on the white
neutron source and the quasi-monoenergetic neutron source which will be
provided by the upgrade of the HI-13 Tandem Accelerator at China Institute
of Atomic Energy (CIAE).
The facility mainly consists of a cylindrical vacuum chamber with the diameter of 100 cm and the height of 50 cm, a target changer with 5 targetframes and eight ΔE-ΔE-E telescopes. Each telescope consists of two silicon detectors and a CsI crystal. Eight telescopes were mounted with 20°angle intervals; they can cover the detection angle from 20 to 160 degrees. ΔE-ΔE-E Techniques were used to obtain good particle identification (PID) for protons, deuterons, tritons, 3He and α particles over an energy range from a few MeV up to 100 MeV. All operations inside the vacuum chamber, i.e., changing the target sample, calibration with an alpha source, or rotation of the telescope table, can be made without breaking the vacuum.
Detailed description of the reaction chamber and the telescopes will be given in this report. The test results and the application of the facility in the future are also presented.
The research of the in-beam efficiency calibration of Neutron Detector Array of Peking University using 17N and 16C beams was introduced in this paper. The efficiency of neutron wall and ball are comparable to the foreign similar devices and neutrons can be detected from low to high energies in high efficiency.
Shanghai Laser Electron Gamma Source, a high intensity beam line of γ-ray, is expected to generate γ-rays up to the maximum energy of 22 MeV by Compton backscattering between a CO2 laser and electrons in the 3.5 GeV storage ring of the Shanghai Synchrotron Radiation Facility. The luminosity of SLEGS γ-ray beam is estimated to be 7×107 A－1W－1s－1 in a optimized setup. Indirect measurement of cross section of the key nuclear-astrophysics reaction 12C(α,γ)16O and γ-ray-triggered transmutation of long-lived radioactive wastes are discussed based on the estimated SLEGS γ-ray beam properties.
A new forward vertex detector is under construction for the PHENIX experiment and will be installed in 2011. The device consists of two sets of four disks of silicon mini-strips and matches the acceptance of the existing muon detectors, and will provide precise vertex measurement for charged tracks. The forward vertex detector is designed to greatly enhance the heavy-flavor physics capabilities on PHENIX. The structure of the proposed device and its performance from Monte Carlo studies are presented.
A Penning trap, which can measure the atomic masses with the highest precision, is one of the most important facilities in nuclear physics research nowadays. The precision mass data play an important role in the studies of nuclear models, mass formulas, nuclear synthesis processes in the nuclear astrophysics, symmetries of the weak interaction and the conserved vector current (CVC) hypothesis. The status of high precision mass measurement around the world, the basic principle of Penning trap and the basic information about the LPT (Lanzhou Penning Trap) are introduced.
The present detection limit for 182Hf at CIAE HI-13 AMS systems could not satisfy various applications (e. g. detection of a nearby supernovae signal). Therefore, techniques were developed in this work to improve the AMS measurement of 182Hf mainly on building a new injector and using a method that based on solid-phase reaction for the preparation of HfF4 samples from HfO2. The experimental results show that mass resolution of the injector can reached 630, and the F－/O－ and beam current of 180HfF5－ for HfF4 samples produced by dry method is about 2—3 times and 1.5 times of that by previously method, respectively.
A new method for measuring selenium-79 with AMS, which is based on extracting molecular negative ions, is described in this paper. According to the experimental results, the extraction ion form SeO2－ could depress the interference of Bromine-79 as much as 5 order levels, that is to say, the background of 79Br can be deducted to 79Br/Se≈10－10. By the way, the chemical form of sample and preparation flow was also developed. Finally, three 79Se AMS calibration standard samples with theoretical 79Se/Se ratios of 5.06×10－7, 6.87×10－8, 5.40×10－10 were obtained and the method of 79Se measurement was set up, which actualized transmission and detection of 79Se. By using our Bragg curve detector, the two isobars 79Br and 79Se could be partly identified to a certain extent and 79Se can be identified from 79Br about 1 order level. AMS measurements of the three calibration standard samples above were performed and good linearity was obtained. The sensitivity of the measurement is (5.16±1.80)×10－11.
The schematic layout and principle of a Bragg curve detector were showed in this paper. A Bragg curve detector was systemically modified and its performance was improved. The total energy resolution of the detector is 0.9% for alpha particle at energy of 5.48 MeV from 241Am source, and the Bragg Peak resolution is 1.6%. Measurement of medium-weight nuclides by using the Bragg curve detector were carried at CIAE-AMS system. series of 36Cl and 41Ca standard samples were measured. The results showed that this Bragg curve detector could clearly identify isobars 36Cl-36S and 41Ca-41K. The results also showed that the ΔZ/Z of 1/47, corresponding to Bragg Peak resolution is 2.1% at ion atomic number of about 16. The Bragg curve detector can be successfully used for AMS measurement.
Tumor radiotherapy was a promising modality and over 100 years. Beams of heavy-charged particles show high RBE advantages and become the optimum tool for tumors therapy. Newly, along with the development of accelerators, scintillators, micro-electronics and computers, the heavy ion tumor therapy has been recognized more and developed.
This article has introduced the origin and speciality of fast-transient signal, and told the meaning of researching on fast-transient signal. The main troubles of sampling on fast-transient signal is its `fast' and `transient', and the experiment's bad condition also troubles the transmission of information. To solve those troubles we put forward a technology called `digital Forward-sampling', and designs a sampling system for the fast-transient signal with this technology. The sampling rate of this system is 1.2 GSPS; it could get the whole pulse of fast-transient signal through the digital Forward-sampling technology; this system also could transmit the result to the analyzing equipment kilometers away immediately, before the data was destroyed by the electromagnetic and
mechanical wave. In the end, this article tells the result of testing on this system, and gives the improved project.
The RFQ cooler and buncher RFQ1L is a key device of the SHANS (Spectrometer for Heavy Atoms and Nuclear Structure). The status of the machining and assembly of the central part is introduced, and the structure of the whole RFQ1L system and the preliminary plan for the testing are discussed also.
A new type of particle identification (PID) detector based on measurements of 1-D Time-Of-Propagation (TOP) and 1-D space information is described. Geant4 toolkit is used to simulate the propagation of Cherenkov photon in thin quartz bar radiator. Contributions to the timing uncertainty are discussed. The π/K separability (S0) is defined and its dependence on the particle momentum, incident angle and propagation length are studied, respectively.
This paper mainly summarizes investigation of TU GAS (Ar:CH4:CF4=90:7:3) with the GEM-TPC detection system that had been developed , especially, the gas's bigger attachment coefficient was obtained and the result does not agree with the results of theoretical calculation seriously. Through repeated verification experimental, the attachment coefficient of measurement acquired. It's 0.1/cm and it's much bigger than the simulated value of 0.003/cm by Garfild. Finally, some analysis results and discussion were given.
Based on the principles of transmission line and the output signal of GEM detector, a full simulation model of delay-line circuit has been described in this paper. The consistency of simulation results and experimental data shows that the method is very effective for the design of delay-line readout.
Neutron penumbral imaging technique is an important diagnosis method in Inertial Confined Fusion, and the design of the aperture shape will affect the resolution of the imaging system. In this paper, several designs of the aperture shape are discussed. Moreover, the pointing precision is also discussed, and a rational pointing precision is given.
PIN detectors have been extensively used to detect charged particles and X-ray. The new type PIN detectors were irradiated by different energy protons, and their irradiation tolerance was investigated. Relative charge collection efficiency, energy spectrometer and relative energy resolution were also measured. With the increasing of irradiation dose, charge collection efficiency decreased and relative energy resolution grown. The results suggested that the irradiation tolerance in the PIN detector depended on the range of the protons in the detector. The maximum tolerance irradiation doses of the detector for the impacts of 3.5 and 7.2 MeV protons were 3×1010p/cm2 and 7.2×109p/cm2, respectively.
Displacement damage dose is applied to analyze the irradiation effects of 2 MeV carbon ions and 0.28~20 MeV protons on homemade GaAs/Ge solar cells. The NIEL for each ion is modified by taking into account the distribution of Bragg damage peak in the active region of the solar cells, and then the corresponding displacement damage dose is obtained. It is found that with the aid of displacement damage dose, the degradation of Pmax of GaAs/Ge solar cells induced by carbon ions and protons with various energies and fluences could be characterized with a simple curve. Obviously, the displacement damage dose approach simplifies the description of ion irradiation effects on homemade GaAs/Ge solar cells.
The total electron emission yields following the interaction of slow highly charged ions (SHCI) O4+ with different material surfaces (W, Au, Si and SiO2) have been measured. It is found that the electron emission yield γ increases proportionally with the projectile velocity v ranging from 5.36×105m/s to 10.7× 105m/s. The total emission yield is dependent on the target materials, and it turns out to follow the relationship γ(Au)>γ(Si)>γ(W). The result shows that the electron emission yields are mainly determined by the electron stopping power of the target when the projectile potential energy is taken as a constant, which is in good agreement with the former studies.
Amorphous SiO2 thin films with about 400—500 nm in thickness were thermally grown on single crystalline silicon. These SiO2/Si samples were firstly implanted at room temperature (RT) with 100 keV carbon ions to 2.0×1017, 5.0×1017 or 1.2×1018 ions/cm2, then irradiated at RT by 853 MeV Pb ions to 5.0×1011, 1.0×1012, 2.0×1012 or 5.0×1012 ions/cm2, respectively. The variation of photoluminescence (PL) properties of these samples was analyzed at RT using a fluorescent spectroscopy. The obtained results showed that Pb-ion irradiations led to significant changes of the PL properties of the carbon ion implanted SiO2 films. For examples, 5.0×1012 Pb-ions/cm2 irradiation produced huge blue and green light-emitters in 2.0×1017 C-ions/cm2 implanted samples, which resulted in the appearance of two intense PL peaks at about 2.64 and 2.19 eV. For 5.0×1017 carbon-ions/cm2 implanted samples, 2.0×1012 Pb-ions/cm2 irradiation could induce the formation of a strong and wide violet band at about 2.90 eV, whereas 5.0×1012 Pb-ions/cm2 irradiation could create double peaks of light emissions at about 2.23 and 2.83 eV. There is no observable PL peak in the 1.2×1018 carbon-ions/cm2 implanted samples whether it was irradiated with Pb ions or not. All these results implied that special light emitters could be achieved by using proper ion implantation and irradiation conditions, and it will be very useful for the synthesis of new type of SiO2-based light-emission materials.
Single-crystalline Si (100) samples were implanted with 30 keV He2+ ions to doses ranging from 2.0×1016 to 2.0×1017ions /cm2 and subsequently thermally annealed at 800℃ for 30min. The morphological change of the samples with the increase of implantation dose was investigated using atomic force microscopy (AFM). It was found that oblate-shaped blisters with an average height around 4.0nm were found on the 2.0×1016 ions /cm2 implanted sample surface; spherical-shaped blisters with an average height around 10.0nm were found on the 5.0×1016 ions /cm2 implanted sample surface; strip-shaped and conical cracks were observed on the sample He-implanted to a dose of 1.0×1017 ions /cm2. Exfoliations occurred on the sample surface to a dose of 2.0×1017 ions /cm2. Mechanisms underlying the surface change were discussed.
The quadrupole interaction in nano-soft magnetic material Fe73.5Cu1Nb3Si13.5B9 has been studied by perturbed angular correlation using 62Zn probe nuclei from the ISOL radioactive nuclear beam facility at CIAE HI-13 tandem accelerator. Two quadrupole interaction frequencies ω01=440 Mrad/s with a distribution width σ=0 and ω02=90 Mrad/s with a width σ=0.48 are obtained. The fractions of ω01 and ω02 are 38% and 62%, respectively. The measured quadruple interaction parameters indicate that 62% of the implanted 62Zn are located in the grain boundary and 32% in the grain.
Two kinds of Fe/Cu multilayers with different modulation wavelength were deposited on cleaved Si(100) substrates and then irradiated at room temperature using 400 keV Xe20+ in a wide range of irradiation fluences. As a comparison, thermal annealing at 300—900℃ was also carried out in vacuum. Then the samples were analyzed by XRD and the evolution of crystallite structures induced by irradiation was investigated. The obtained XRD patterns showed that, with increase of the irradiation fluence, the peaks of Fe became weaker, the peaks related to Cu-based fcc solid solution and Fe-based bcc solid solution phase became visible and the former became strong gradually. This implied that the intermixing at the Fe/Cu interface induced by ion irradiation resulted in the formation of the new phases which could not be achieved by thermal annealing. The possible intermixing mechanism of Fe/Cu multilayers induced by energetic ion irradiation was briefly discussed.
Crystalline n-type Si (100) wafers were implanted at room temperature with
160 keV He ions to a fluence of 5×1016cm－2 or 40 keV H ions to a fluence of 1×1016cm－2, singly or in combination, followed by thermal annealing. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and cross-sectional transmission electron microscopy (XTEM) have been used to investigate ion implantation induced surface phenomena and thermal evolution of micro-defects. SEM results show that successive implantation of He and H ions could induce surface blistering and exfoliation of Si at high thermal annealing temperature. AFM observations reveal that the surface exfoliation is mainly achieved at the sample depth corresponding to the projected range of H ions. XTEM observations demonstrate that the occurrence of surface blister or exfoliation on silicon can be attributed to the important role of He implantation in the thermal growth of H induced defects.
One of main difficulties in the experiments of inner-shell ionization of atoms by positron impact near threshold energy region is the relatively high low-energy background, which is caused by the deposited part of energy in semi-conductor X-ray detectors of 0.511 MeV γ rays that are produced by positron annihilations in targets and target chamber. In this paper, by using the Monte Carlo method, we simulated the backgrounds for the X-ray detectors with the sensitive layer thickness of 0.3 mm and 3 mm in the case of 0.511 MeV γ rays impacting vertically on a Ti plate of 0.2 mm in thickness, and compared the simulation results with the experimental observations of the other research group and our own. Moreover, we also simulated the backgrounds for a simplified experimental setup in the case of 20 keV positrons impacting vertically on a thick Ti target and observed that the backgrounds for the X-ray detectors with the sensitive layer thickness of 0.3 mm and 3 mm, are very similar.
The paper selects 15 samples of the pottery warriors in Qinshihuang Mausoleum Pit K0006, 21 samples of pottery warriors in Qinshihuang Mausoleum Pit K0007 and 75 samples of clay nearby Qinshihuang mausoleum. The contents of 23 elements were measured by neutron activation analysis (NAA), from which these data were got and analyzed by fuzzy cluster analysis so that the cluster analysis diagram is obtained. The results show that the soil ingredients of the pottery warriors of Pit K0006 and Pit K0007 were very similar to that of the area of Wuling site, Shanliu village, Shanren village and burial accompany Pit K9801, indicating that the pottery warriors in Pit K0006 and Pit K0007 are made of the local materials.
Loess is the most important and the most typical continental classic sediments of Quaternary. So the measurement of In-situ produced cosmogenic 10Be is expected to be used for the Loess stratigraphic age. But the production rate of In-situ produced cosmogenic 10Be in Loess quartz is very low. It requires very high sensitivity and accuracy of measurement. This work has measured the concentrations of 10Be of two layers in Loess section of Luochuan including L8, L9 and the concentrations of 10Be in (of) blank sample with the HI-13 AMS system at China Insitute of Atomic Energy(CIAE), then calculated the content of 10Be in loess quartz for each layer. The ratio of 10Be/9Be was found in the range of 10－13. The background of 10Be/9Be was about 3×10－14.
Nuclear analytical technique is an efficient method in study of rarity cultural relic for its advantage of nondestructive analysis. Longquan celadon is one kind of the most important ancient porcelain in China. In order to determine the inner provenance property and age's characteristic of ancient Longquan porcelain, ten components in porcelain body and glaze were measured by the Wave Dispersive X-ray Fluorescence (WDXRF). Multivariates Statistical Analysis was used to analyze the experiment data. The results showed that the chemical compositions in porcelain body of three typical kilns were similar. The difference of components in porcelain glaze can be used to identify the provenance and age.
The excess 3H (tritium) have been observed in the volcanic lakes Nemrut (Turkey), Laacher (Germany) and Pavin (France). The 4He and 3He concentrations in Lakes Nemrut, Laacher, and Pavin were determined to be 25 and 190, 10 and 50, and 70 and 500 times larger than the atmospheric saturation value respectively. The isotopic ratio of the helium excess, 3Heex/4Heex, in Lakes Nemrut, Laacher and Pavin was (1.032±0.006)×10－5, (7.42±0.03)×10－6 and (9.09±0.01)×10－6 respectively. The 3He/4He ratio of helium isotopes in the lake can help us to identify the origin of gas fluxes from the interior of the Earth. The 3He/4He ratios in the Lakes Nemrut, Laacher and Pavin clearly indicate that a large amount of helium isotopes were released to the lakes from mantle source. The excess 3H at the bottom of Lakes Nemrut, Laacher and Pavin have a good correlation with mantle 3He. We consider that the excess 3H might be also released from mantle source and both 3H and 3He might be produced by nuclear fusion (d-d reaction) in an environment rich in H atoms and (U+Th) at high temperature and high pressure condition in deep Earth.
Treatment planning of heavy-ion radiotherapy involves predictive calculation of not only the physical dose but also the biological dose in a patient body. The goal in designing beam-modulating devices for heavy ion therapy is to achieve uniform biological effects across the spread-out Bragg peak (SOBP). To achieve this, a mathematical model of Bragg peak movement is presented. The parameters of this model have been resolved with Monte Carlo method. And a rotating wheel filter is designed basing on the velocity of the Bragg peak movement.
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