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.
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.
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)
55102285
CONCEPTUAL DESIGN OF INJECTION SYSTEM FOR HEFEI LIGHT SOURCE (HLS) UPGRADE PROJECT
In order to obtain more straight sections for insertion devices and higher brilliance synchrotron radiation, an upgrade project of Hefei Light source (HLS) is undergoing. A new injection system has been designed to improve injection efficiency and keep the machine running stably. Four kickers will be used to generate a local injection bump. Effects of injection system to injecting beam and stored beam have been simulated considering errors. Finally, ELEGANT code was used to simulate the injection process with new designed bump system. The simulation results show that the injection efficiency would be higher than 99% and perturbation on stored beam would be small enough, which are benefit to full energy injection and top-up operation of HLS in the future. INTRODUCTION Hefei Light Source (HLS) of National Synchrotron Radiation Laboratory is a dedicated second generation light source [1,2]. In order to obtained synchrotron radiation with high brightness in the VUV and soft X-ray range for synchrotron radiation users, A plane of building a new machine named HLSII storage ring has been brought forward. Considering the required low emittance and the straight sections’ number and length, A DBA lattice structure with 4 super-periods has been chosen for HLSII. 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. 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. β and dispersion functions of the two modes are shown in Fig. 1 and 2. Table1 gives main parameters of the storage ring. Table 1: Storage Ring Parameters
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
64725884
THE UPGRADE PROJECT OF HEFEI LIGHT SOURCE (HLS)
To enhance the performance of Hefei Light Source, which was designed and constructed two decades ago, an upgrade project is undergoing. The detail upgrade scheme was described in this paper. Firstly, the magnet lattice of storage ring should be reconstructed with 4 DBA cells, whose advantages are lower beam emittance and more straight section available for insertion devices. Secondly, the beam diagnostics, main power supply, transverse and longitudinal multi-bunch feedback, beam control and manipulation system would be upgrade to improve the beam orbit stability. Finally, the injection system of storage ring and injector, which is composed of electron linac and beam transfer line, would be updated in order to assure smooth beam accumulation process under new low emittance lattice. With above measures, it is hopeful to increase the brilliance of Hefei Light Source by two orders approximately. INTRODUCTION HLS is a dedicated second generation VUV light source, whose main body is composed of 800MeV electron storage ring, 200MeV linac and beam transfer line. HLS was designed and constructed in the late 1980s; ten years ago, Phase II Upgrade Project was carried out and more beamlines were built successfully. The main parameters of HLS were listed in table 1. There are two factors affecting light source performance: large beam emittance and less number of straight sections. Table 1: Main Parameters of HLS Injection/Operation Energy 200/800 MeV Circumference 66.13m Magnet Lattice 4×TBA RF Frequency 204MHz Transverse Tunes 3.54/2.60 Momentum Compaction 0.048 Energy Loss 16.3keV/turn Beam Intensity 250~300mA Beam Emittance ~160nm⋅rad Parameters of straight section 3.36m×4 = 13.4m Number of undulator 2 MOTIVATION OF UPGRADE VUV synchrotron radiation plays the essential roles in the quantum control, catalysis, combustion and blame, high temperature super-conductivity, etc. Unfortunately, HLS can’t meet the requirements of some advanced SR experiments due to lower brilliance. There are three keys to improve HLS performance: increasing the number of insertion devices, lowering beam emittance and improving the beam orbit stability. UPGRADE OF MAGNET LATTICE Considering theoretical minimum beam emittance and number of straight section, separate function DBA was adopted as the standard cell of ring. Similar to many light sources, the length of straight section in the arc was increased to install undulators. The layout of new magnet lattice is showed in the Figure 1. 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 2 and Figure 3 displayed the Twiss and dispersion function of two modes. Figure 1: Magnet layout of HLS II storage ring. Work supported by NSFC (10875127 and 10979045) wanglin@ustc.edu.cn ____________________________________________ ork supported by (10875127 and 10979045) anglin ustc.edu.cn WEPEA043 Proceedings of IPAC’10, Kyoto, Japan 2588 02 Synchrotron Light Sources and FELs A05 Synchrotron Radiation Facilities 0 2 4 6 8 10 12 14 16 0 2 4 6 8 10 12 14 16 18 20 β an d η fu nc tio ns /m Long itud inal positions /m β x β y 10 *η ξ Figure 2: β and dispersion function of mode A. 0 2 4 6 8 10 12 14 16 0 2 4 6 8 10 12 14 16 18 20 β an d η fu nc tio ns /m Longitudinal positions /m βx βy 10*η Figure 3: β and dispersion function of mode B. Table 2: Main parameters of HLS II 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
119284944
Thermal fluctuations in viscous cosmology
In this Letter we investigate the power spectrum of thermal fluctuations in very early stage of viscous cosmology. When the state parameter as well as the viscous coefficient of a barotropic fluid is properly chosen, a scale invariant spectrum with large non-Gaussianity can be obtained. In contrast to the results previously obtained in string gas cosmology and holographic cosmology, we find the non-Gaussianity in this context can be k-independent such that it is not suppressed at large scale, which is expected to be testified in future observation.
209999832
Measurements of charge transfer efficiency in a proton-irradiated swept charge device
Charged Coupled Devices (CCDs) have been successfully used in several low energy X-ray astronomical satellites over the past two decades. Their high energy resolution and high spatial resolution make them a perfect tool for low energy astronomy, such as observing the formation of galaxy clusters and the environment around black holes. The Low Energy X-ray Telescope (LE) group is developing a Swept Charge Device (SCD) for the Hard Xray Modulation Telescope (HXMT) satellite. A SCD is a special low energy X-ray CCD, which can be read out a thousand times faster than traditional CCDs, simultaneously keeping excellent energy resolution. A test method for measuring the charge transfer efficiency (CTE) of a prototype SCD has been set up. Studies of the charge transfer inefficiency (CTI) with a proton-irradiated SCD have been performed at a range of operating temperatures. The SCD is irradiated by 3x10(8)cm(-2) 10 MeV protons.
119177216
Lepton Flavor Violating $\tau$ Decays in Two Higgs Doublet Model III
We study the lepton flavor violating processes of $\tau^-\to\mu^-PP$ decays with $PP=K^+K^-,K^0\bar{K}^0,\pi^+\pi^-,\pi^0\pi^0$ in the framework of two Higgs doublet model III by virtue of the Chiral Perturbation Theory. In this model, only three neutral Higgs bosons contribute to these decays. With the current experimental constraints, we show that (a) the contributions of $|\lambda_{uu(dd)}|$ term are very small for these four decays; (b) we get the correlation between $|\lambda_{ss}|$ and $|\lambda_{\tau\mu}|$. For $|\lambda_{\tau\mu}| \sim 10-400$, one has $|\lambda_{ss}|\sim 40-1$; (c) in the existing model parameter space, $Br(\tau^- \to \mu^- K^+K^-)$ could reach the order of ${\cal O}(10^{-8})$, but $Br(\tau \to \mu^- \pi^+\pi^-/\pi^0\pi^0)$ are too small to be observed.
110580855
File and metadata management for BESIII distributed computing
The BESIII experiment at the Institute of High Energy Physics (IHEP), Beijing, uses the high-luminosity BEPCII e+e− collider to study physics in the π-charm energy region around 3.7 GeV; BEPCII has produced the worlds largest samples of J/ and ' events to date. An order of magnitude increase in the data sample size over the 2011-2012 data-taking period demanded a move from a very centralized to a distributed computing environment, as well as the development of an efficient file and metadata management system. While BESIII is on a smaller scale than some other HEP experiments, this poses particular challenges for its distributed computing and data management system. These constraints include limited resources and manpower, and low quality of network connections to IHEP. Drawing on the rich experience of the HEP community, a system has been developed which meets these constraints. The design and development of the BESIII distributed data management system, including its integration with other BESIII distributed computing components, such as job management, are presented here.
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.