54740568
A PRELIMINARY EXPERIMENT FOR THE BEAM BASED CALIBRATION OF BEAM POSITION MONITORS AT BEPC
By varying an individual quadrupole magnet and observing the effect on the orbit, the offset of the adjacent beam position monitor (BPM) with respect to the magnetic center of that quadrupole magnet can be determined. At BEPC, 4 BPM offsets in the vertical plane were measured by using this beam-based method. The measurement results will be shown in this paper. 1 GENERAL DESCRIPTION The properties of an electron positron collider are mainly determined by the quadrupole magnets. The highest luminosity and best performances are obtained when the beam is well centered in the quadrupole magnets. The quadrupole magnets of the Beijing Electron-Positron Collider (BEPC) are aligned with an accuracy of better than 0.2 mm rms to form the absolute closed orbit reference. Thirty-two button-type beam position monitors (BPMs) are installed in the BEPC storage ring close to the quadrupole magnets. In order to measure and correct the beam orbit to the reference orbit, it is necessary to know the relative offset between the beam position monitor’s electric center and the adjacent quadrupole’s magnetic center. Despite careful alignment and electric calibration of the beam position monitors, there can still be residual offsets. These residual offsets can be measured by a beam-based alignment technique. Figure 1 shows the principle of the beam-based calibration. When the integrated strength of a quadrupole magnet at the location s 0 of the storage ring is changed by ∆ kl, the beam obtains a local angular kick ∆ y’(s0) = ∆ kly(s 0 ), where y(s 0 ) is the transverse beam position displacement or offset in the quadrupole magnet. This angu) ( ’ ] ) ( ) ( ) ) ( ) ( ) (
201926003
THE BEPCII DCCT SYSTEM
A DC Current Transformer (DCCT) as a standard diagnostic system for beam current plays an important role in BEPCII, the upgrade project of the Beijing Electron Positron Collider. Two DCCTs are operating now, separately in the electron and positron rings, to monitor the beam current, the beam injection rate, the beam loss rate and the beam lifetime. In this paper, the mechanical structure design, readout system and data processing are presented. The progress of DCCTs on each step of BEPCII commissioning, such as improving the beam lifetime and reducing the background noise, are also included.
173169030
WIRE SCANNER FOR TRANSVERSE BEAM PARAMETER MEASURE- MENT IN BEPCII
BEPCII, the upgrade project of Beijing Electron Positron Collider (BEPC), is an accelerator with large beam current and high luminosity, so an efficient and stable injector is required. Several beam diagnostic and monitoring instruments are used. A new diagnostic instrument wire scanner, has been designed and will be used to measure the profile of the linac beam of BEPCII. This paper describes the prototype of this system and the cause of heat generating of the wire. Some simulation results of the heat and force by using finite element method softwareANSYS, are presented and discussed.
110785343
BEPC STORAGE RING BEAM LOSS MONITOR SYSTEM DESIGN
The Beijing Electron Positron Collider (BEPC) is a large experimental equipment for high energy physics as well as synchrotron radiation research in parasitic or dedicated mode. The beam loss phenomenon is frequently observed in the BEPC storage ring, especially when BEPC operates in the dedicated synchrotron radiation mode. Although the accelerator physics group has carried out some studies on this phenomenon, but so far this phenomenon has not well explained. The beam loss monitors (BLMs) have been developed for detecting and locating any possible excessive beam loss with the injection process, beam instabilities, bad vacuum, ion trapping, etc. This paper will discuss the system design considerations such as the detector-type selection, the BLM location in the ring and related experiment results, and so on.
40534119
Synchrotron radiation monitoring system at BEPC
The synchrotron radiation by the relativistic particles is a useful and important diagnostic tool to obtain various beam parameters. The visible light of the synchrotron radiation emitted in a bending magnet of the BEPC storage ring is reflected through the window by a water-cooled mirror in the vacuum chamber and then directed by a remote controlled mirror onto the optical bench supporting the diagnostic instruments in the dark room. These instruments include a CCD camera providing the image of the beam transverse profile on a TV monitor, a lens system focusing the synchrotron light onto a solid state scanned photodiode arrays to obtain the beam height or width, a streak camera to measure the bunch length for a single pass, and a two-dimensional position sensing photo-detector to monitoring the drift of the beam position. This paper gives the detailed description of the synchrotron radiation monitoring system at BEPC.
54677120
BEPC BEAM INSTRUMENTATION SYSTEM AND ITS UPGRADE FOR BEPC-II
The Beijing Electron Positron Collider (BEPC) has been successfully operated for many years since 1989. Now BEPC is proposed to upgrade to BEPC-II. The beam instrumentation system of the BEPC storage ring includes many subsystems such as BPMs, tune measurement, current monitor, synchrotron radiation monitor, etc. This paper will describe the present operation performance of the beam instrumentation system of the BEPC storage ring and its upgrade plan for BEPC-II.
55221705
Measurement of decay time of liquid scintillator
In this paper we describe a single photon method to measure the decay time of two kinds of homemade liquid scintillator. We find that the fast and slow decay time constants of these two samples, with 5cm diameter and 4cm height, are about similar to 4ns and similar to 17ns, respectively. These results are checked through a reference measurement by recording the scintillation pulse shapes at the output of a fast response PMT directly by a digital oscilloscope. The time responses of these two samples are as good as those of commercial liquid scintillator. (C) 2008 Elsevier B.V. All rights reserved.
55451255
Determining Reactor Neutrino Flux
Abstract Flux is an important source of uncertainties for a reactor neutrino experiment. It is determined from thermal power measurements, reactor core simulation, and knowledge of neutrino spectra of fuel isotopes. Past reactor neutrino experiments have determined the flux to (2–3)% precision. Precision measurements of mixing angle θ 13 by reactor neutrino experiments in the coming years will use near-far detector configurations. Most uncertainties from reactor will be canceled out. Understanding of the correlation of uncertainties is required for θ 13 experiments. Precise determination of reactor neutrino flux will also improve the sensitivity of the non-proliferation monitoring and future reactor experiments. We will discuss the flux calculation and recent progresses.
17587825
Narrow width of a glueball decay into two mesons
The widths of a glueball decay to two pions or kaons are analyzed in the perturbative QCD (PQCD) framework. Our results show that the glueball ground state has a small branching ratio for the two-meson decay mode, which is around 10(-2). The predicted values are consistent with the data of xi-->pi pi, KK if the xi particle is a 2(++) glueball. The applicability of PQCD to the glueball decay and a comparison with X-cj decay are also discussed. [S0556-2821(98)04705-5].
13628240
Light-cone QCD predictions for elastic ed scattering in the intermediate energy region
The contributions of helicity-flip matrix elements to the deuteron form factors are discussed in the light-cone frame. Normalized A(Q(2)), B(Q(2)), G(Q)(Q(2)), and T-20 are obtained in a simple QCD-inspired model. As a result of the kinematical enhancement, the helicity-flip matrix elements contribute significantly to G(M) and G(Q) while eta is small. Our numerical results are consistent with data in the intermediate energy region.
242130
Daya Bay Neutrino Experiment
The Daya Bay Neutrino Experiment is proposed to measure sin(2) 2 theta(13) to better than 0.01 at 90% C.L. in a three-year run. The experimental site, detector design, and background estimation are presented.