125850686
Transverse Feedback System and Instability Analysis at HLS
In this paper, the BxB transverse feedback systems at Hefei Light Source (HLS) are introduced, which employ an analog system and a digital system. The experiment result of two systems. as well as the primary analysis of beam instability in HLS operation is also presented in this paper. INTRODUCTION HLS is a synchrotron light source,injecting in the energy of 200MeV and operating in the 800MeV. The multi-cycle multi-turn injection system is used for current accumulation. The range of horizontal tune of HLS is from 3.54 to 3.56, and the range of vertical tune is from 2.58 to 2.60 for user operation. The injecting beam current usually cannot exceed 120mA without octupole magnet, and the injecting accumulating beam current is about 250mA with octupole magnet because the beam often occur sudden lose due to CB instabilities in storage ring to limit injection further increase. Therefore the constructing beam feedback system began from 2006 year. The analog feedback system has been built and commissioned at 2007[1-3], At the same time, the development of digital transverse BxB feedback system began at 2007 and has commissioned since 2008[4]. THE ANALOG TFB SYSTEM AND EXPERIMENT RESULTS The diagram of analog TFB system is shown as Figure 1. The analog feedback system is made up of: 3tap filter at centre frequency 612MHz (3*fRF) , hybrid for obtaining beam position oscillation signal, vector algorithm for two BPMs to obtain feedback signal of independent adjustable gain, multiple frequency circuit for centre frequency 612MHz (3*fRF) and 1.2GHz (6*fRF), PXI digitizer for data acquisition modular, the fiber correlator filter for eliminate DC and revolution frequencies, the power amplifier and kicker for exciting beam current. Commissioning Results of Analog TFB at HLS During the commissioning, the damping time and betatron sidebands have been measured by Turn-by-Turn (TBT) [5].and bunch-by-bunch (BXB) [6]. measurement system at beam injecting is shown as Figure 1. Figure 1: Overview of HLS analog TFB after update
43173006
The TAOS Project: Statistical Analysis of Multi-Telescope Time Series Data
The Taiwanese-American Occultation Survey (TAOS) monitors fields of up to ~1000 stars at 5 Hz simultaneously with four small telescopes to detect occultation events from small (~1 km) Kuiper Belt Objects (KBOs). The survey presents a number of challenges, in particular the fact that the occultation events we are searching for are extremely rare and are typically manifested as slight flux drops for only one or two consecutive time series measurements. We have developed a statistical analysis technique to search the multi-telescope data set for simultaneous flux drops which provides a robust false-positive rejection and calculation of event significance. In this article, we describe in detail this statistical technique and its application to the TAOS data set.
12981394
A Close Binary Star Resolved from Occultation by 87 Sylvia
The star BD +29 1748 was resolved to be a close binary from its occultation by the asteroid 87 Sylvia on 2006 December 18 UT. Four telescopes were used to observe this event at two sites separated by some 80 km. Two flux drops were observed at one site, whereas only one flux drop was detected at the other. From the long-term variation of Sylvia, we inferred the probable shape of the shadow during the occultation, and this in turn constrains the binary parameters: the two components of BD +29 1748 have a projected separation of 0:097-0:140 on the sky with a position angle 104°-110°. The asteroid was clearly resolved, with a size scale ranging from 130 to 290 km as projected onto the occultation direction, consistent with the size dimensions 385 × 265 × 230 km, mea- sured by direct adaptive optics imaging. No occultation was detected for either of the two known moonlets of 87 Sylvia.
9262984
Bunch Tracing by Bunch by Bunch Measurement System in HLS
In this paper, we introduce a bunch tracing system which is based on a bunch-by-bunch (BxB) measurement system in Hefei Light Source (HLS), and present the analysis of the experiment results. Using an in-phase gate signal and a double balance mixer to control an external trigger of ADC, we test the reliability of the BxB system. By this system, we can trace all marked bunches in a set time slot or in manual burst mode. We can record all bunches’ data during the injection, ramping, wiggler excitation and normal operation, and provide a powerful facility for machine study.
37988677
Development of Measurement and Transverse Feedback System at HLS
In order to cure and damp coupled bunch (CB) instabilities caused by the high order modes (HOMs) of the RF cavity and the resistive wall impedance of the Ring vacuum chamber. HOMs are ineluctable during the operation of the accelerator. An observer system characterized by bunch by bunch measurement of transverse β oscillation and longitudinal synchrotron phase oscillation has been constructed and commissioned at Hefei Light Source (HLS) [1, 2]. A transverse bunch-by-bunch feedback system is under construction. The design and development of the observe systems, as well as diagnostics results of machine instabilities are presented in this paper.
119230126
The TAOS Project Stellar Variability II. Detection of 15 Variable Stars
The Taiwanese-American Occultation Survey (TAOS) project has collected more than a billion photometric measurements since 2005 January. These sky survey data-covering timescales from a fraction of a second to a few hundred days-are a useful source to study stellar variability. A total of 167 star fields, mostly along the ecliptic plane, have been selected for photometric monitoring with the TAOS telescopes. This paper presents our initial analysis of a search for periodic variable stars from the time-series TAOS data on one particular TAOS field, No. 151 (RA = 17$^{\rm h}30^{\rm m}6\fs$67, Dec = 27\degr17\arcmin 30\arcsec, J2000), which had been observed over 47 epochs in 2005. A total of 81 candidate variables are identified in the 3 square degree field, with magnitudes in the range 8 < R < 16. On the basis of the periodicity and shape of the lightcurves, 29 variables, 15 of which were previously unknown, are classified as RR Lyrae, Cepheid, delta Scuti, SX Phonencis, semi-regular and eclipsing binaries.
120805024
Search for First Generation Scalar Leptoquarks in pp Collisions at $\sqrt{s}=7$ TeV with the ATLAS Detector
We report a search for first generation scalar leptoquarks using 1.03 fb−1 of proton–proton collisions data produced by the Large Hadron Collider at and recorded by the ATLAS experiment. Leptoquarks are sought via their decay into an electron or neutrino and a quark, producing events with two oppositely charged electrons and at least two jets, or events with an electron, missing transverse momentum and at least two jets. Control data samples are used to validate background predictions from Monte Carlo simulation. In the signal region, the observed event yields are consistent with the background expectations. We exclude at 95% confidence level the production of first generation scalar leptoquark with masses when assuming the branching fraction of a leptoquark to a charged lepton is equal to 1.0 (0.5).
30236486
Observation of the Omega(0)(c) Charmed Baryon at CLEO.
The CLEO experiment at the CESR collider has used 13.7 fb(-1) of data to search for the production of the Omega(0)(c) (css ground state) in e(+)e(-) collisions at square root of (s) approximately 10.6 GeV. The modes used to study the Omega(0)(c) are Omega(-)pi(+), Omega(-)pi(+)pi(0), Xi-K-pi(+)pi(+), Xi0K-pi(+), and Omega(-)pi(+)pi(+)pi(-). We observe a signal of 40.4+/-9.0(stat) events at a mass of 2694.6+/-2.6(stat)+/-1.9(syst) MeV/c(2), for all modes combined.
207917728
AN FPGA-BASED TUNE MEASUREMENT SYSTEM FOR THE APS BOOSTER SYNCHROTRON
The Advanced Photon Source (APS) injection booster is a 7-GeV electron synchrotron with a ramping time of 226 ms and a repetition rate of 2 Hz. A real-time tune measurement system is needed in order to monitor and correct tune drift during the 226-ms energy ramp. Such a drift occurs during user beam operations, especially during continuous top-up operations, and results in shotto-shot efficiency fluctuations. We designed and developed an FPGA-based system that pings the beam at variable intervals and measures tunes. An operational system has been built and commissioned. It has achieved a time resolution of better than 2 ms and a tune resolution of better than 0.001. This report describes the system design and main parameters, and results from our preliminary commissioning. We also briefly discuss the application of such a system in ramping correction and ring diagnostics.
117804786
INTEGRAL & RXTE View of Gamma-ray Binaries
Gamma-ray binaries are X-ray binaries with gamma-ray emissions. Their multi-wavelength emissions range from radio, optical, X-ray and to very high energy (TeV). X-ray emissions are crucial to understand the nature of gamma-ray binaries. INTEGRAL and RXTE have covered and monitored most of the gamma-ray binaries in hard and soft X-rays. Here we report the results of several gamma-ray binaries and possible gamma-ray binaries from INTEGRAL and RXTE.
113240014
HLS bunch current measurement system
Bunch current is an important parameter for studying the injection fill-pattern in the storage ring and the instability threshold of the bunch, and the bunch current monitor also is an indispensable tool for the top-up injection. A bunch current measurement (BCM) system has been developed to meet the needs of the upgrade project of Hefei Light Source (HLS). This paper presents the layout of the BCM system. The system based on a high-speed digital oscilloscope can be used to measure the bunch current and synchronous phase shift. To obtain the absolute value of bunch-by-bunch current, the calibration coefficient is measured and analyzed. Error analysis shows that the RMS of bunch current is less than 0.01 mA when bunch current is about 5 mA, which can meet project requirement.