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.
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
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
14623575
The Calibration of the Swift UVOT Optical Observations: A Recipe for Photometry
ABSTRACT The Ultraviolet/Optical Telescope (UVOT) on board Swift has the capability to provide critical insight into the physics of the early afterglows of gamma‐ray bursts (GRBs). But without precise calibration of the UVOT to standard photometric systems, it is impossible to leverage late‐time, ground‐based follow‐up data to the early‐time UVOT observations. In this paper, we present a calibration of the Swift UVOT photometry to the standard Johnson UBV system for the UVOT U, B, and V filters, and a step‐by‐step photometry recipe for analyzing these data. We base our analysis on aperture photometry performed on the ground‐based and UVOT observations of the local standard stars in the fields of supernovae (SNe) 2005am and 2005cf and a number of Landolt standard stars. We find that the optimal photometry aperture radius for UVOT data is small (2 \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmary...
124889910
Recent Beijing Spectroscopy (BES) results
AbstractRecent experimental results from Beijing Spectroscopy (BES) are reviewed, including the hadron spectroscopy from J/ψ decays, and a number of new states are found or confirmed, including σ, κ, X(1835), ωφ threshold enhancement in J/ψ→γωφ, a broad resonance in J/ψ→K+K−π0, decay studies of ψ(2S) and χCJ, as well as the results of ψ(3770) non-D$$
\bar D
$$ decays. The current status of BEPCII/BESIII, the major upgrade of BEPC/BESII, is also reported.
118857728
Dynamical chiral symmetry breaking in QED{sub 3} at finite density and impurity potential
We study the effects of finite chemical potential and impurity scattering on dynamical fermion mass generation in (2+1)-dimensional quantum electrodynamics. In any realistic systems, these effects usually cannot be neglected. The longitudinal component of the gauge field develops a finite static length produced by chemical potential and impurity scattering, while the transverse component remains long-ranged because of the gauge invariance. Another important consequence of impurity scattering is that the fermions have a finite damping rate, which reduces their lifetime. By solving the Dyson-Schwinger equation for the fermion mass function, it is found that these effects lead to strong suppression of the critical fermion flavor N{sub c} and the dynamical fermion mass in the symmetry broken phase.
8834215
The lick agn monitoring project 2011: Fe II reverberation from the outer broad-line region
The prominent broad Fe II emission blends in the spectra of active galactic nuclei have been shown to vary in response to continuum variations, but past attempts to measure the reverberation lag time of the optical Fe II lines have met with only limited success. Here we report the detection of Fe II reverberation in two Seyfert 1 galaxies, NGC 4593 and Mrk 1511, based on data from a program carried out at Lick Observatory in Spring 2011. Light curves for emission lines including Hβ and Fe II were measured by applying a fitting routine to decompose the spectra into several continuum and emission-line components, and we use cross-correlation techniques to determine the reverberation lags of the emission lines relative to V-band light curves. In both cases, the measured lag (τ{sub cen}) of Fe II is longer than that of Hβ, although the inferred lags are somewhat sensitive to the choice of Fe II template used in the fit. For spectral decompositions done using the Fe II template of Veron-Cetty et al., we find τ{sub cen}(Fe II)/τ{sub cen}(Hβ) = 1.9 ± 0.6 in NGC 4593 and 1.5 ± 0.3 in Mrk 1511. The detection of highly correlated variations between Femore » II and continuum emission demonstrates that the Fe II emission in these galaxies originates in photoionized gas, located predominantly in the outer portion of the broad-line region.« less
41827043
The Massive Progenitor of the Possible Type II-Linear Supernova 2009hd in Messier 66
We present early- and late-time photometric and spectroscopic observations of supernova (SN) 2009hd in the nearby spiral galaxy NGC 3627 (M66). This SN is one of the closest to us in recent years and provides an uncommon opportunity to observe and study the nature of SNe. However, the object was heavily obscured by dust, rendering it unusually faint in the optical given its proximity. We find that the observed properties of SN 2009hd support its classification as a possible Type II-Linear SN (SN II-L), a relatively rare subclass of core-collapse SNe. High-precision relative astrometry has been employed to attempt to identify an SN progenitor candidate, based on a pixel-by-pixel comparison between Hubble Space Telescope (HST) F555W and F814W images of the SN site prior to explosion and at late times. A progenitor candidate is identified in the F814W images only; this object is undetected in F555W. Significant uncertainty exists in the astrometry, such that we cannot definitively identify this object as the SN progenitor. Via insertion of artificial stars into the pre-SN HST images, we are able to constrain the progenitor's properties to those of a possible supergiant, with intrinsic absolute magnitude M^0_(F555W) ≳ –7.6 mag and intrinsic color (V – I)^0 ≳ 0.99 mag. The magnitude and color limits are consistent with a luminous red supergiant (RSG); however, they also allow for the possibility that the star could have been more yellow than red. From a comparison with theoretical massive-star evolutionary tracks which include rotation and pulsationally enhanced mass loss, we can place a conservative upper limit on the initial mass for the progenitor of M_(ini) ≾ 20 M_☉. If the actual mass of the progenitor is near the upper range allowed by our derived mass limit, then it would be consistent with that for the identified progenitors of the SN II-L 2009kr and the high-luminosity SN II-Plateau (II-P) 2008cn. The progenitors of these three SNe may possibly bridge the gap between lower-mass RSGs that explode as SNe II-P and luminous blue variables, or more extreme RSGs, from which the more exotic SNe II-narrow may arise. Very late time imaging of the SN 2009hd site may provide us with more clues regarding the true nature of its progenitor.