124768645
Development of high intensity beam emittance measurement unit
Three sets of High Intensity Beam Emittance Measurement Units (HIBEMUs) are being developed at Peking University. They are HIBEMU-2 (slit-wire type, one direction), HIBEMU-3 (Allison scanner type, one direction) and HIBEMU-4 (slit-wire type, two directions). For HIBEMU-2 and HIBEMU-3, more recent work has been done on software redesign in order to measure beam emittance and to draw phase diagram more efficiently and precisely. Software for control and data processing of them were developed in Labveiw environment, trying to improve calculation rationality and to offer user-friendly interface. Mechanical modification was also done for HIBEMU-3, mainly concentrating on the protection of Faraday cups from being overheated by the high intensity beam and also from interference of secondary electrons. This paper will also cover the mechanical structure as well as the software development of HIBEMU-4, which is a two-direction emittance scanner newly designed and manufactured for the high energy beam transport (HEBT) of Peking University Neutron Imaging FaciliTY (PKUNIFTY). At the end of this paper, comparison and analysis of the three HIBEMUs are given to draw forth better design of the future emittance measurement facility.
43842936
Study of the Energy Modulated Electron Cyclotron Resonance Ion Source for the Coupled RFQ-SFRFQ Cavity
The coupled RFQ and SFRFQ cavity has been manufactured and tested recently. According to the beam dynamic design, the input He beam within 120° phase width is designed for the cavity to achieve over 98% transmission efficiency. An energy modulated electron cyclotron resonance (ECR) ion source was proposed and simulated. To achieve the 1% energy modulation on the 30keV direct current (DC) beam, two simplified RF power feeding structures for beam bunching were studied. The simulations show positive results as well as the bunched beam is achieved by the energy modulated ECR ion source.
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.
55611929
A PEPPER-POT BASED DEVICE FOR DIAGNOSTICS OF THE SINGLE-SHOT BEAM
In order to measure the peak current and the beam transversal distribution of an ampere-scale microsecond single-pulse ion beam, a novel single shot beam diagnostic device based on pepper-pot technique, which is a combination of Faraday cup and pepper-pot measurement facility, was developed at Peking University (PKU) [1]. It consists of a main Faraday cup with a pepper-pot mask at its bottom, and a Faraday cup array locating 3 mm away from the pepper-pot mask. This device has been tested at the PKU LEBT test bench and the measurement results are consistent with the results acquired by the Allison scanner. By replacing the Faraday cup array with a fluorescent screen and a CCD camera, this device becomes a facility that not only has the ability to measure the total beam current and the beam profile, but also has the capability to measure the beam emittance for CW or pulsed ion beams. Details will be presented in this paper.
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.
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.
326670
Limits on sizes of fundamental particles and on gravitational mass of a scalar
We review the experimental limits on mass of excited fundamental particles and contact interaction energy scale parameters Λ for QCD, QED and electroweak reactions. In particular we have focused on the QED reaction measuring the differential cross-sections for the process e+e−→γγ(γ) at the energies from 91 GeV to 202 GeV using the data collected with the L3 detector from 1991 to 1999. With a global fit we set lower limits at 95% CL on Λ>1687 GeV, which restricts the characteristic QED size of the interaction region to Re<1.17×10−17 cm. All the interaction regions are found to be smaller than the Compton wavelength of the fundamental particles. This constraint is used to estimate a lower limit on the size of a fundamental particle related to gravitational interaction, applying the model of self-gravitating particle-like structure with the de Sitter vacuum core. It gives rτ⩾2.3×10−17 cm and re⩾1.5×10−18 cm, if leptons get masses at the electroweak scale, and rτ⩾3.3×10−27 cm,re⩾4.9×10−26 cm, as the most stri...
119319863
The Liouville side of the vortex
We analyze conformal blocks with multiple (semi-)degenerate field insertions in Liouville/Toda conformal field theories an show that their vector space is fully reproduced by the four-dimensional limit of open topological string amplitudes on the strip with generic boundary conditions associated to a suitable quiver gauge theory. As a by product we identify the non-abelian vortex partition function with a specific fusion channel of degenerate conformal blocks.
118033922
A quantum oscillator model for entropic gravity
In Verlinde's theory of entropic gravity, the internal degrees of freedom are marked by "bits", but the microscopic origin of "bits" is unknown hitherto. To this direction, we adopt the quantum harmonic oscillators to naively model the internal degrees of freedom. In this model, the equipartition relation is modified at the low temperature. The Newton's law and Poisson's equation of gravity are reproduced at small distances, but they receive appreciable corrections at large distances. Geometrization of gravity for this model is explored, resulting in modifications to Einstein equations.
109283317
Design and implementation of the NaI(Tl)/CsI(Na) detectors output signal generator
We designed and implemented a signal generator that can simulate the output of the NaI(Tl)/CsI(Na) detectors' pre-amplifier onboard the Hard X-ray Modulation Telescope (HXMT). Using the development of the FPGA (Field Programmable Gate Array) with VHDL language and adding a random constituent, we have finally produced the double exponential random pulse signal generator. The statistical distribution of the signal amplitude is programmable. The occurrence time intervals of the adjacent signals contain negative exponential distribution statistically.
18467789
Putting non Point-like Behavior of Fundamental Particles to Test
We review the experimental limits on those hypothetical interactions where the fundamental particles could exhibit non point-like behavior. In particular we have focused on the QED reaction measuring the differential cross sections for the process $ \EEGG $ at energies around 91 GeV and 209 GeV with data collected from the L3 detector from 1991 to 2001. With a global fit L3 set lower limits at $ 95 % $ CL on a contact interaction energy scale parameter $\Lambda > 1.6 $ TeV, which restricts the characteristic QED size of the interaction region to $ R_{e} < 1.2 \times 10^{-17} $ cm. All the interaction regions are found to be smaller than the Compton wavelength of the fundamental particles. This constraint we use to estimate a lower limit on the internal density of particle-like structure with the de Sitter vacuum core. Some applications of obtained limits to the string and quantum gravity scales are also discussed.