106943567
THE CONTROL SYSTEM OF THE MAIN MAGNET POWER SUPPLY IN NSRL
The control system of main magnet power supplies (PS) in NSRL electron storage ring is built upon the Experimental Physics and Industrial Control System (EPICS). Because PCs have become more and more popular in accelerator control, We use Industrial PC (IPC) as the low-level controller, i.e. front-end device controller (FDC). A total of 12 FDCs control a group of 12 PSs respectively. PSs are star connected to an Input / Output controller (IOC) via RS422. The IOC is an IPC on which vxWorks runs to meet the demand of EPICS. A SUN workstation is used as an OPI (Operator Interface) as well as an EPICS server.
2014815
An upgrade proposal of injection bump system for HLS
The current injection bump system in HLS storage ring, which is designed 8 years ago, has been operated 5 years up to the present with acceptable performance. Due to inherent limitation of HLS (Hefei Light Source) storage ring, there are some deficiencies of the design. For the potential of full energy injection, reasonable design objective was summed up. Then, physical design of new bump system was brought forward. Using simple formula, the acceptance to injected beam and perturbation on stored beam were estimated approximately. Finally, the ELEGANT software was used to simulate the injection process with new designed bump system. The simulation results showed that, the injection efficiency would be higher than 90% and perturbation on stored beam would be small enough, which are very essential to full energy injection and top-up operation of HLS.
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.
126336869
Low emittance lattice optimization using multiobjective genetic algorithm
Low emittance is a desirable performance for high brightness synchrotron light source and damping ring. The work presented in this paper demonstrates that the lattice of a given electron storage ring, which has fixed circumference and magnet layout, can be optimized to obtain low emittance by using MOGA (Multi-objective Genetic Algorithm). Both dispersion-free and nondispersion-free lattices of HLS (Hefei Light Source) upgrade project are computed as an illustration. Simulation result shows that this method is fast and straightforward. INTRODUCTION Presently, there are many codes for storage ring lattice design, such as MAD, OPA, ELEGANT, etc. The critical problem of designing lattice by these codes is that they will consume the designers lots of time to adjust it repeatedly. Though the designers could get a satisfactory structure, but they couldn’t judge whether the ultimate performance is reached. MOGA is a highly effective randomly searching algorithm, which can globally search a set of solutions over a domain. These solutions are superior to the rest of solutions when considering all of the objectives, which are called Pareto-optimal solutions. This algorithm was introduced into damping ring [1] and storage ring lattice [2] optimization in recent years. It overcomes the above difficulties of the existing codes and converges to a set of Pareto optimal solutions. Also this algorithm settles the high computational complexity. In this paper we will use a nondominated sorting-based multi-objective evolutionary algorithm (NSGA-II) [3] to optimize linear optics of low emittance lattice. NSGA-II AND CONSTRAINT HANDLING APPROACH The Non-dominated Sorting Genetic Algorithm (NSGA) was proposed by Srinivas and Deb in 1994. Later the upgraded algorithm NSGA-II was developed. It overcomes the following difficulties of NSGA: high computational complexity, non-elitist and the need for specifying sharing parameters. The optimization steps of this algorithm are listed as below: First of all, rank and crowding distance of the initial population will be computed. And then sort these individuals based on their non domination. Generate a child population from the initial population, and keep the Pareto optimal solutions .
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.
119277915
CEPHEID CALIBRATIONS OF MODERN TYPE Ia SUPERNOVAE: IMPLICATIONS FOR THE HUBBLE CONSTANT
This is the first of two papers reporting measurements from a program to determine the Hubble constant to {approx}5% precision from a refurbished distance ladder. We present new observations of 110 Cepheid variables in the host galaxies of two recent Type Ia supernovae (SNe Ia), NGC 1309 and NGC 3021, using the Advanced Camera for Surveys on the Hubble Space Telescope (HST). We also present new observations of the hosts previously observed with HST whose SNe Ia provide the most precise luminosity calibrations: SN 1994ae in NGC 3370, SN 1998aq in NGC 3982, SN 1990N in NGC 4639, and SN 1981B in NGC 4536, as well as the maser host, NGC 4258. Increasing the interval between observations enabled the discovery of new, longer-period Cepheids, including 57 with P>60 days, which extend these period-luminosity (P-L) relations. We present 93 measurements of the metallicity parameter, 12 + log[O/H], measured from H II regions in the vicinity of the Cepheids and show these are consistent with solar metallicity. We find the slope of the seven dereddened P-L relations to be consistent with that of the Large Magellanic Cloud Cepheids and with parallax measurements of Galactic Cepheids, and we address the implications for themore » Hubble constant. We also present multi-band light curves of SN 2002fk (in NGC 1309) and SN 1995al (in NGC 3021) which may be used to calibrate their luminosities. In the second paper, we present observations of the Cepheids in the H band obtained with the Near-Infrared Camera and Multi-Object Spectrometer on HST, further mitigating systematic errors along the distance ladder resulting from dust and chemical variations. The quality and homogeneity of these SN and Cepheid data provide the basis for a more precise determination of the Hubble constant.« less
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.
46679854
Classifications of the Host Galaxies of Supernovae
Classifications on the DDO system are given for the host galaxies of 177 supernovae (SNe) that have been discovered since 1997 during the course of the Lick Observatory Supernova Search with the Katzman Automatic Imaging Telescope. Whereas SNe Ia occur in all galaxy types, it is found, at a high level of statistical confidence, that SNe Ib, Ic, and II are strongly concentrated in late‐type galaxies. However, attention is drawn to a possible exception provided by SN 2001I. This SN IIn occurred in the E2 galaxy UGC 2836, which was not expected to harbor a massive young supernova progenitor.
15212085
Observations of type ia supernovae, and challenges for cosmology
Observations of Type Ia supernovae (SNe Ia) reveal correlations between their luminosities and light-curve shapes, and between their spectral sequence and photometric sequence. Assuming SNe Ia do not evolve at different redshifts, the Hubble diagram of SNe Ia may indicate an accelerating Universe, the signature of a cosmological constant or other forms of dark energy. Several studies raise concerns about the evolution of SNe Ia (e.g., the peculiarity rate, the rise time, and the color of SNe Ia at different redshifts), but all these studies suffer from the difficulties of obtaining high-quality spectroscopy and photometry for SNe Ia at high redshifts. There are also some troubling cases of SNe Ia that provide counterexamples to the observed correlations, suggesting that a secondary parameter is necessary to describe the whole SN Ia family. Understanding SNe Ia both observationally and theoretically will be the key to boosting confidence in the SN Ia cosmological results.
123608448
Experience of BESIII data production with local cluster and distributed computing model
The BES III detector is a new spectrometer which works on the upgraded high-luminosity collider, BEPCII. The BES III experiment studies physics in the tau-charm energy region from 2 GeV to 4.6 GeV . From 2009 to 2011, BEPCII has produced 106M ψ(2S) events, 225M J/ψ events, 2.8 fb−1 ψ(3770) data, and 500 pb−1 data at 4.01 GeV. All the data samples were processed successfully and many important physics results have been achieved based on these samples. Doing data production correctly and efficiently with limited CPU and storage resources is a big challenge. This paper will describe the implementation of the experiment-specific data production for BESIII in detail, including data calibration with event-level parallel computing model, data reconstruction, inclusive Monte Carlo generation, random trigger background mixing and multi-stream data skimming. Now, with the data sample increasing rapidly, there is a growing demand to move from solely using a local cluster to a more distributed computing model. A distributed computing environment is being set up and expected to go into production use in 2012. The experience of BESIII data production, both with a local cluster and with a distributed computing model, is presented here.