119112485
Multidimensionally constrained relativistic mean field model and applications in actinide and transfermium nuclei
We present some results of potential energy surfaces of actinide and transfermium nuclei from multidimensionally constrained relativistic mean field (MDC-RMF) models. Recently we developed multidimensionally constrained covariant density functional theories (MDC-CDFT), in which all shape degrees of freedom beta with even mu are allowed, and the functional can be one of the following four forms: the meson exchange or point-coupling nucleon interactions combined with the nonlinear or density-dependent couplings. In MDC-RMF models, the pairing correlations are treated with the BCS method. With MDC-RMF models, the potential energy surfaces of even-even actinide nuclei were investigated and the effect of triaxiality on the fission barriers in these nuclei was discussed. The nonaxial reflection-asymmetric beta(32) shape in some transfermium nuclei with N = 150, namely Cm-246, Cf-248, Fm-250 and No-252, were also studied.
122169147
Microscopic self-consistent study of neon halos with resonant contributions
Recent reaction measurements have been interpreted as evidence of a halo structure in the exotic neutron-rich isotopes Ne-29,Ne-31. While theoretical studies of Ne-31 generally agree on its halo nature, they differ significantly in their predictions of its properties and underlying cause (e.g., that Ne-31 has an inverted ordering of p-f orbitals). We have made a systematic theoretical analysis of possible Neon halo signatures - the first using a fully microscopic, relativistic mean field approach that properly treats positive energy orbitals (such as the valence neutron in Ne-31) self-consistently with bound levels, as well as the pairing effect that keeps the nucleus loosely bound with negative Fermi energy. Our model is the analytical continuation of the coupling constant (ACCC) method based on a relativistic mean field (RMF) theory with Bardeen-Cooper-Schrieffer (BCS) pairing approximation. We calculate neutron- and matter-radii, one-neutron separation energies, p- and f-orbital energies and occupation probabilities, and neutron densities for single-particle resonant orbitals in Ne27-31. We analyze these results for evidence of neutron halo formation in Ne-29,Ne-31. Our model predicts a p-orbit in halo structure for Ne-31, based on a radius increase from Ne-30 that is 7-8 times larger than the increase from Ne-29 to Ne-30, as well as a decrease in the neutron separation energy by a factor of similar to 10 compared to that of Ne27-30. In contrast to some other studies, our inclusion of resonances yields an inverted ordering of p and f orbitals for spherical and slightly deformed nuclei. Furthermore, we find no evidence of an s-orbit in halo in Ne-29 as recently claimed in the literature. (C) 2014 The Authors. Published by Elsevier B.V.
55241388
Potential energy surfaces of actinide and transfermium nuclei from multi-dimensional constraint covariant density functional theories
Multi-dimensional constrained covariant density functional theories were developed recently. In these theories, all shape degrees of freedom β λμ deformations with even μ are allowed, e.g., β 20 , β 22 , β 30 , β 32 , β 40 , β 42 , β 44 , and so on and the CDFT functional can be one of the following four forms: the meson exchange or point-coupling nucleon interactions combined with the non-linear or density-dependent couplings. In this contribution, some applications of these theories are presented. The potential energy surfaces of actinide nuclei in the ( β 20 , β 22 , β 30 ) deformation space are investigated. It is found that besides the octupole deformation, the triaxiality also plays an important role upon the second fission barriers. The non-axial reflection-asymmetric β 32 shape in some transfermium nuclei with N = 150, namely 246 Cm, 248 Cf, 250 Fm, and 252 No are studied.
32125097
PRELIMINARY RESULTS OF H2+ BEAM GENERATED BY A 2.45 GHZ PERMANENT MAGNET ECR ION SOURCE AT PKU
To obtain high-yield H2 ion beam, experimental and theoretical study was carried out on the 2.45 GHz Peking University permanent magnet electron cyclotron resonance ion source (PKU PMECRIS). With PMECR II [1], studies on the size of discharge chamber and the operation pressure were carried out to increase H2 ion fraction. Beam analysis results prove that the H2 can reach 47.7% with suitable operation parameters. More details will be presented in this paper. INTRODUCTION The creation of molecular ion H2 is an essential process in hydrogen gas plasma. For proton ion source, H2 ions are undesirable in the final extract beam. But recently, the demand to build an ion source to generate high current hydrogen molecular ion H2 beam has been growing rapidly. For example, H2 ion can be used as a pilot beam of the intense deuteron beam during the commissioning of linear accelerators to minimize the activation of components.[2][3] Also it is an effective way to improve the output current of cyclotrons by accelerating H2 and stripping it into H at the exit of accelerator, instead of accelerating H beam directly.[4][5] R. F. King et al. proposed a one-dimensional plasma model for a volume arc source, which is expected to produce 140 mA of ion beam with H2 species ratio around 73% in theory, but it wasn’t realized.[6] N. Joshi et al. developed a volume type ion source at Frankfurt University, and about 91% H2 was extracted with current intensity of 2.84 mA.[7] Obviously, the fraction of H2 is definitely high, but the current is not enough for some applications. With a 2.45 GHz permanent magnet ECR ion source PMECR II [1][8][9] (Fig. 1), the fraction and current intensity of molecular ion H2 were improved at PKU. Theoretical study indicates that, to optimize the production of H2, it is helpful to increase the electron temperature in the source and avoid attachment with neutral H2 which lead to fast destruction of H2.[6] In our PMECRIS, these were achieved by changing the size of discharge chamber and operation pressure in the source. The experimental results will be presented.
119227150
Nonaxial-octupole Y-32 correlations in N=150 isotones from multidimensional constrained covariant density functional theories
The nonaxial reflection-asymmetric beta(32) shape in some transfermium nuclei with N = 150, namely, Cm-246, Cf-248, Fm-250, and No-252, are investigated with multidimensional constrained covariant density functional theories. By using the density-dependent point-coupling covariant density functional theory with the parameter set DD-PC1 in the particle-hole channel, it is found that, for the ground states of Cf-248 and Fm-250, the nonaxial octupole deformation parameter beta(32) > 0.03 and the energy gain due to the beta(32) distortion is larger than 300 keV. In Cm-246 and No-252, shallow beta(32) minima are found. The occurrence of the nonaxial octupole beta(32) correlations is mainly from a pair of neutron orbitals, [734]9/2 (nu j(15/2)) and [622]5/2 (nu g(9/2)), which are close to the neutron Fermi surface, and a pair of proton orbitals, [521]3/2 (pi f(7/2)) and [633]7/2 (pi i(13/2)), which are close to the proton Fermi surface. The dependence of the nonaxial octupole effects on the form of the energy density functional and on the parameter set is also studied.
55354069
NUMERICAL METHODS TO THE SPACE CHARGE COMPENSATION (SCC) EFFECT OF THE LEBT BEAM
Numerical simulation as well as experimental researches on space charge compensation for high intensity, low energy ion beam has been done at Peking University (PKU). In this paper we will describe the simulation model proposed at PKU and use it on the PKU ECR single-charged ion source. It consists of a new concept of equivalent density and more consideration of physical process. A series of arithmetical equations is gained through theoretical derivation. Although no numerical solutions have been carried out from our computation, it is foreseeable that the final result will be achieved soon.
120465076
Beam optimization of helium injector for coupled RFQ-SFRFQ linac
Abstract The coupled RFQ–SFRFQ (CRS) cavity designed in Peking University is a new type linac that coupled radio frequency quadrupole (RFQ) and separated function radio frequency quadrupole (SFRFQ) structure into a single cavity. An upgraded helium injector for the CRS cavity consisting of a 2.45 GHz permanent magnet electron cyclotron resonance (ECR) ion source and a 1.16 m low energy beam transport (LEBT) has been constructed and tested. The beam conditions of the injector were carefully optimized to satisfy the requirements of the CRS linac, the corresponding control system and a two-dimension scanner code CRSv1.0 were developed for optimizing the beam transmission from LEBT section to the entrance of the CRS cavity. The beam transmission efficiency has reached to approximately 87.5% as well as the optimized operating parameters were obtained by means of the scanner code.
117183376
Test of non point‐like behavior of Fermions
We search in measurements from LEP, TRISTAN, CDF, D0 and UA1 for those phenomena beyond the Standard Model where the fundamental particles can exhibit non point‐like behavior. The total and differential cross sections for the reaction e+e− → γγ(γ) measured at center‐of‐mass energies from 55 GeV to 207 GeV are used for a global fit to test the hypothesis of an excited electron and contact interaction induced terms. The best value for the fit exhibits an approximately 5 σ effect for the scale factor of an excited electron of (1/Λ±4)best = −(1.11 ± 0.20) × 10−10 GeV−4 and the scale of contact interaction of (1/Λ4)best = −(4.05 ± 0.73) × 10−13 GeV−4 but with the opposite to the expected in the modified cross section sign. An empirical scheme is discussed to encompass all fermions and bosons in one framework, if these particles would be geometrically extended objects.
118558419
Matrix Model and Refined Wall-Crossing Formula
In this paper, we show how to get matrix models corresponding to the refined BPS states partition functions of $\mathbb{C}^3$, resolved conifold and $\mathbb{C}^3/\mathbb{Z}_2$ by inserting the identity operator at a proper position in the fermionic expression of the refined BPS states partition functions.
92987620
Vertices, vortices & interacting surface operators
A bstractWe show that the vortex moduli space in non-abelian supersymmetric $ \mathcal{N} = \left( {{2},{2}} \right) $ gauge theories on the two dimensional plane with adjoint and anti-fundamental matter can be described as an holomorphic submanifold of the instanton moduli space in four dimensions. The vortex partition functions for these theories are computed via equivariant localization. We show that these coincide with the field theory limit of the topological vertex on the strip with boundary conditions corresponding to column diagrams. Moreover, we resum the field theory limit of the vertex partition functions in terms of generalized hypergeometric functions formulating their AGT dual description as interacting surface operators of simple type. Analogously we resum the topological open string amplitudes in terms of q-deformed generalized hypergeometric functions proving that they satisfy appropriate finite difference equations.
119135529
Orbifold Vortex and Super Liouville Theory
We study the nonabelian vortex counting problem on $\mathbb{C}/\mathbb{Z}_p$. At first we calculate vortex partition functions on the orbifold space using localization techniques, then we find how to extract orbifold vortex partitions function from orbifold linear quiver instanton partition functions. Finally, we study the AGT like relation between orbifold SU(2) vortices and $\mathcal{N} = 1$ super Liouville theory in the mixed R/NS sector by fixing the dictionary among parameters in the common hypergeometric functions system.