56077124
A closed orbit measurement with the NSRL BPM system
The beam position monitor system (BPM) of NSRL electron storage ring have a resolution of 10 microns with an accuracy of 50 microns, which is adequate fix beam position measurement and the closed orbit correction. The paper describes both of the BPM system and the closed orbit measurement.
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.
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.
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.
39289464
HLS Turn-by-Turn System and its Application
Measurement principles and analysis of Turn-by-Turn beam position monitor system at Hefei Light Source (HLS) are presented in this paper. In emphases, several typical applications are presented here, which include the commissioning of upgraded injection system on HLS storage, monitoring of transientν transientν transientν transientν transientν transientν transientν transientν transientν transientν and damping time of storage ring, beam instability in injection, as well as experiments of low frequency feedback system. Precise analyses of experimental results offer some conclusions, which are consistent with theoretical expectations. The system plays an important role in study of beam instability and improvement of machine performance.
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.
126239408
Observation of B+ ---> K(1)(1270)+ gamma
7484606
Forward energy flow, central charged-particle multiplicities, and pseudorapidity gaps in W and Z boson events from pp collisions at $\sqrt{s}= 7$ TeV
A study of forward energy flow and central charged-particle multiplicity in events with W and Z bosons decaying into leptons is presented. The analysis uses a sample of 7 TeV pp collisions, corresponding to an integrated luminosity of 36 pb−1, recorded by the CMS experiment at the LHC. The observed forward energy depositions, their correlations, and the central charged-particle multiplicities are not well described by the available non-diffractive soft-hadron production models. A study of about 300 events with no significant energy deposited in one of the forward calorimeters, corresponding to a pseudorapidity gap of at least 1.9 units, is also presented. An indication for a diffractive component in these events comes from the observation that the majority of the charged leptons from the W(Z) decays are found in the hemisphere opposite to the gap. When fitting the signed lepton pseudorapidity distribution of these events with predicted distributions from an admixture of diffractive (pompyt) and non-diffractive (pythia) Monte Carlo simulations, the diffractive component is determined to be (50.0 ± 9.3 (stat.) ± 5.2 (syst.))%.
110247079
Charge division read-out in a 1.8-m-long wire chamber
This paper reports on the design and the test results of a charge division electronic read-out system for a charged particle proportional wire detector. Electronic calibration and probable error analysis of the system are also discussed. Position resolution for the system has been measured to be 4.8-mm FWHM on a wire of 1.8-m length (0.26%, relative). >
122103110
Experimental studies on the photoelectron instability in the Beijing Electron Positron Collider
A vertical coupled-bunch instability was observed for a positron beam at the Beijing Electron Positron Collider (BEPC). The experimental results show that the instability has similar characteristics as that observed in the Photon Factory of KEK several years ago. The instability at BEPC can be explained by the effect of an electron cloud which is produced in the beam chamber by synchrotron light hitting the wall.
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.