119213503
Radiation field simulation of C-ADS Injector II
The injector of C-ADS (Chinese Accelerator Driven Sub-critical System) project is a high current, fully super-conducting proton accelerator. Meanwhile, a BLM system is indispensable to this facility, especially in low energy segments. This paper presents some basic simulations for 10MeV proton by Monte Carlo program FLUKA, as well as the distributions on different secondary particles in three aspects: angular, energy spectrum and current. These results are beneficial to selecting the detector type and its location and determining its dynamic range matching different requirements for both fast and slow beam loss. Further, the major impact of the background is analyzed, such as superconducting cavity X radiation and radiation caused by material activation, in this paper as well. This work is meaningful in BLM system research.
118572221
Analytic modeling of instabilities driven by higher-order modes in HLS II RF system with a higher-harmonic cavity
The utility of a passive fourth-harmonic cavity plays key role in suppressing longitudinal beam instabilities in the electron storage ring and lengthens the bunch by a factor of 2.6 for the phase II project of Hefei Light Source(HLS II). Meanwhile, instabilities driven by higher-order modes(HOM) may limit the performance of the higher-harmonic cavity. In this paper, the parasitic coupled-bunch instability which is driven by narrow band parasitic modes and the microwave instability which is driven by broadband HOM are both modeled analytically. The analytic modeling results are in good agreement with that of our previous simulation study and indicate that the passive fourth-harmonic cavity suppresses parasitic coupled-bunch instabilities and the microwave instability. The modeling suggests that a fourth-harmonic cavity may be successfully used at HLS II.
125890271
Closed orbit correction of hefei light source(hls) upgrading storage ring
In order to meet the increasing requirements of synchrotron radiation users, an upgrading plan of hefei light source is undergoing by National Synchrotron Radiation Laboratory (NSRL). The emittance of storage ring is reduced from 166nm.rad to 36nm.rad. In this paper, we study the beam close orbit distortions’ (COD) sensitivity to the field and alignment errors in magnets. Estimation of the COD from various error sources is investigated. The distribution of beam position monitors and the location of correctors are reported in the paper. Simulation proves that COD can be corrected down to 50 microns level. In the same time the corrector strengths are weaker enough in the correction scheme. INTRODUCTION Hefei Light Source (HLS) of National Synchrotron Radiation Laboratory is a dedicated second generation light source. HLS can’t meet the requirements of some advanced SR experiments due to lower brilliance. In order to obtained synchrotron radiation with high brightness and better coherence in the VUV and soft Xray range for users, an upgrading plan of hefei light source is undergoing[1]. Considering theoretical minimum beam emittance and number of straight section, separate function DBA was adopted as the standard cell of ring. Two optional focusing parameters were designed, which is named as mode A and mode B. The mode A is an achromatic mode, whose dispersion in the long straight section is zero. In contrast, the mode B is a distributed dispersion mode, whose emittance is smaller than that of mode A. The figure 1 and figure 2 displayed the twiss and dispersion function of two modes. Main parameters about HLS II storage ring can be founded in table1. The magnet alignment errors will lead to larger closed orbit distortion (COD), which can induce unwanted effects. The non-linear effect can make the dynamic aperture and beam lifetime decreasing. Furthermore, it will change the synchrotron light’s position at the beamline front ends, which can influence the brightness at experiment station. In order to correct the COD, Beam Position Monitors (BPMs) and correctors must be installed. In the paper, COD is estimated considering alignment errors in magnets and girders. Magnets field errors are also included. Using SVD method, the closed orbit distortions are corrected. Table 1: Main Parameters of HLS II Storage Ring Mode A Mode B Operation energy 800MeV Circumference 66.13m RF frequency 204MHz Transverse tunes 4.41/3.21 4.44/3.20 Momentum compaction 0.0205 0.0183 Emittance 36nm.rad 20nm.rad Radiation loss 16.74kev/turn Beam intensity > 300mA Parameters of straight section (4m + 2.3m) 4 = 25.2m Orbit shift < 5 m 0 2 4 6 8 10 12 14 16 0 2 4 6 8 10 12 14 16 18 20 an d fu nc tio ns /m Longitudinal positions /m x
114005690
LATTICE DESIGN AND BEAM LIFETIME STUDY FOR HLS STORAGE RING UPGRADE PROJECT
HLS (Hefei Light Source) is a dedicated synchrotron radiation research facility, whose emittance is relatively large. In order to improve performance of the machine, especially getting higher brilliance synchrotron radiation and increasing the number of straight sections for insertion devices, an upgrade project is on going. A new low emittance lattice, which keeps the circumference of the ring no changing, has been studied and presented in this paper. For the upgrade project, a new ring will be installed on current ground settlement of HLS and all of the magnets will be reconstructed. After optimization, two operation modes have been chosen for different users. Nonlinear dynamics shows that dynamic aperture for onmomentum and off-momentum particle is large enough. Beam lifetime has also been studied. Calculation results proves that expected beam lifetime about 8.5 hours can be obtained with a fourth harmonic cavity operation. INTRODUCTION HLS is a typical 2nd generation synchrotron radiation light source. A 200MeV electron linear accelerator, an 800MeV electron storage ring and a beam transport line are the main component parts about the machine. Phase I project of HLS was finished in 1989 [1], which marks that the first dedicated synchrotron radiation light source has been fulfilled in china. From 1999 to end of 2004, Phase II Upgrade Project [2] of HLS was carried out in order to improve the machine reliability and install more beamlines for users. For the operating machine, beam emittance of the lattice is 160nm⋅rad. The magnet lattice is a TBA structure with 4 super periods and transverse tunes are 3.54 and 2.60 respectively, which means only 4 straight sections can be used to install insertion devices or injection system. With the current situation of HLS, an upgrade project was brought forward one year ago, which main purpose is to improve the machine’s performance. Comparing with 2nd generation synchrotron light sources in the world, there are three considering aspects for this project. First, a new lattice should be found to reduce beam emittance to get higher brilliance synchrotron radiation for users. Second, more straight sections are needed for installing wiggler or undulators. Third, beam orbit stability should be improved to guarantee the radiation’s quality. Some systems such as magnet system will be rebuilt to meet the project requirement. Considering time limitation of the project, the new ring will be installed on current ground settlement of HLS, which means circumference of the ring will keep 66.13m as current situation. LINEAR OPTICS Several lattices have been studied over the past years. As work progressed, it became clear that DBA lattice could meet the emittance purpose while providing an increased number of insertion device straight sections. In this way, a DBA with 4 periods was chosen as the lattice structure. There are 8 straight sections along the ring. Four short straight sections about 2.3m in chromatic arcs can be used besides four 4.0m long achromatic straight sections. There are eight quadrupoles in each cell. 4 quadrupoles are located in chromatic arcs and others in long straight section which can be used to adjust tunes and β function. In order to lengthen straight sections, combined function sextupoles are chosen to save space along the ring. Sextupoles can not only compensate chromaticity and harmonics, but correct closed orbit distortion and transverse coupling by providing dipole and skew quadrupole field components. The magnet layout of the ring is shown in Figure 1. Figure 1: Magnet layout of HLS II storage ring. Two operation modes (mode A and mode B) have been optimized. Mode A is an achromatic mode, whose dispersion in the long straight section is zero. Mode B is a distributed dispersion mode, whose emittance is smaller than that of mode A. Table1 shows list of the linear lattice about the two modes in half cell. β and dispersion functions of the two modes are shown in Figure2 and 3. Table2 gives main parameters of the storage ring. From above results, one can see that there are same tunes in the two modes although their beam emittances are quite ___________________________________________ *Work supported by NSFC (10905054 and 10979045) fenggy@ustc.edu.cn Proceedings of IPAC’10, Kyoto, Japan WEPEA042 02 Synchrotron Light Sources and FELs A05 Synchrotron Radiation Facilities 2585 different. This means one can easy get Mode B from Mode A by lattice tuning. Table 1: List of The Linear Lattice (Half cell)
54892783
APPLICATION OF PCS IN NSRL CONTROL SYSTEM
The upgrade of the National Synchrotron Radiation Laboratory (NSRL) control system is currently being implemented using EPICS (Experimental Physics and Industrial Control System). For cost saving purposes, we use a large number of PCs. PCs play a dominant role as I/O controllers (IOCs) and device controllers in the new control system. In this paper, the application of PCs in the NSRL control system is described.
119610396
Simultaneous optimization of beam emittance and dynamic aperture for electron storage ring using genetic algorithm
Finding a high quality of lattice that simultaneously meets low beam emittance performance and acceptable dynamic aperture is a challenging task for the storage ring-based light source, especially for the next generation storage ring which is characterized with ultralow beam emittance. This paper presents an alternative method, based on the concept of genetic algorithm, to simultaneously optimize the beam emittance and dynamic aperture for low emittance lattice. Instead of analyzing the nonlinear indicators extracted from the high order nonlinear map, the algorithm can globally optimize the nonlinear performance by the direct dynamic aperture tracking result. So this method is more straightforward and efficient than analyzing the nonlinear driving terms. In order to illustrate this method, the quadrupole and sextupole strengths of a five-bend-achromatic lattice are simultaneously optimized by nondominated sorting genetic algorithm II (NSGA-II). Finally, the optimal linear optics for ultralow emittance lattices with better dynamic aperture are obtained. The result shows that the algorithm is particularly useful for the low emittance lattice design, where the beam emittance and the dynamic aperture always conflict with each other.
117275575
The double charm decays of B Mesons in the mSUGRA model
Based on the low energy effective Hamiltonian with naive factorization, we calculate the branching ratios(BRs) and CP asymmetries (CPAs) for the twenty three double charm decays $B/B_s \to D^{(*)}_{(s)} D^{(*)}_{(s)}$ in both the standard model (SM) and the minimal supergravity (mSUGRA) model. Within the considered parameter space, we find that (a) the theoretical predictions for the BRs, CPAs and the polarization fractions in the SM and the mSUGRA model are all consistent with the currently available data within $\pm 2\sigma$ errors; (b) For all the considered decays, the supersymmetric contributions in the mSUGRA model are very small, less than $7\%$ numerically. It may be difficult to observe so small SUSY contributions even at LHC.
54005042
Modular properties of 3D higher spin theory
A bstractIn the three-dimensional $ \mathfrak{s}\mathfrak{l} $(N) Chern-Simons higher-spin theory, we prove that the conical surplus and the black hole solution are related by the S-transformation of the modulus of the boundary torus. Then applying the modular group on a given conical surplus solution, we generate a ‘SL(2, $ \mathbb{Z} $)’ family of smooth constant solutions. We then show how these solutions are mapped into one another by coordinate transformations that act non-trivially on the homology of the boundary torus.After deriving a thermodynamics that applies to all the solutions in the ‘SL(2, $ \mathbb{Z} $)’ family, we compute their entropies and free energies, and determine how the latter transform under the modular transformations. Summing over all the modular images of the conical surplus, we write down a (tree-level) modular invariant partition function.
109503889
EM Calorimeter in BESIII Experiment
BESIII EM Calorimeter (EMC) is based on CsI crystals, working at upgraded Beijing Electron Positron Collider (BEPC), called BEPCII. The overall BEPCII and BESIII design and current status are briefly described. The design and construction of EMC and its performance are presented. EMC works very well and its performances reach the design expectations, it plays an important roll in detector operation and in the BESIII trigger. There are some special features in the EMC construction and reconstruction: the crystals are assembled without support wall to reduce dead area; the time information of the EM clusters can help to suppress the machine background; the detector noise is smaller than similar detectors; the energy reconstruction with TOF signals helps to improve the energy resolution, especially for low energy showers. Several physics papers mainly based on EMC information have been published.
1852671
The Light Echo around Supernova 2003gd in Messier 74
ABSTRACT We confirm the discovery of a light echo around the Type II‐plateau supernova 2003gd in Messier 74 (NGC 628), seen in images obtained with the High Resolution Channel of the Advanced Camera for Surveys on board the Hubble Space Telescope (HST) as part of a larger Snapshot program on the late‐time emission from supernovae. The analysis of the echo we present suggests that it is due to the SN light pulse scattered by a sheet of dust grains located ∼113 pc in front of the SN, and that these grains are not unlike those assumed to be in the diffuse Galactic interstellar medium, both in composition and in size distribution. The echo is less consistent with scattering off carbon‐rich grains, and if anything, the grains may be somewhat more silicate rich than the Galactic dust composition. The echo also appears to be more consistent with a SN distance closer to 7 Mpc than to 9 Mpc. This further supports the conclusion we reached elsewhere that the initial mass for the SN progenitor was relatively low (∼8...
110884800
The High-Level Dataset-based Data Transfer System in BESDIRAC
Data transfer is an essential part in grid. In the BESIII experiment, the result of Monte Carlo Simulation should be transfered back from other sites to IHEP and the DST files for physics analysis should be transfered from IHEP to other sites. A robust transfer system should make sure all data are transfered correctly. DIRAC consists of cooperation distributed services and light-weight agents delivering the workload to the Grid Resources. We reuse the most functionalities supplied by DIRAC. BESDIRAC is an extension to DIRAC for BES specified. In BESDIRAC, a Dataset-based Data Transfer System is developed. In this paper, we present the design of this system and its implementation details.