123393729
Tune Measurements in the BEPC Storage Ring
The betatron and synchrotron tunes are measured frequently during the period of the machine operation and machine studies. The tune measurement system of the BEPC storage ring includes a spectrum analyzer, two sets of the stripline, two voltage amplifiers and a beam oscillation detector. This paper gives the detailed description of the upgraded tune measurement system in the BEPC storage ring.
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) ( ’ ] ) ( ) ( ) ) ( ) ( ) (
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.
22957262
DAQ System of BPM and BCT for the BEPCII Linac
Following the BEPCII upgrade, total about 19 BPMs and 12 BCTs have been newly installed in the BEPCII Linac. Also, a set of distributed control system based on EPICS architecture has been built, and the BPM and BCT system are merged into the new control system for the data acquisition. In order to reduce the effects of RF noise, a special gated integrator was used for the BCT system. In this paper we will describe the DAQ system of BPM and BCT including calibrations in detail.
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.
198186499
THE PROGRESS OF BEPCII STORAGE RING DIAGNOSTICS SYSTEM
In this paper, we will present the progress of BEPCII storage rings beam diagnostics system along with the BEPCII commissioning. Tools such as Libera BPM had been used for the BPR first turn measurement and the injection residual orbit research of BER. COD_BPM can satisfy the resolution requirement for the beam-beam scan in the interaction region, and for the COD measurement, BCM (bunch current monitor) can help us on the different injection pattern. The TFB system is important to suppress the strong multi-bunch instabilities during the higher beam current running. The tune meters, the beamloss monitors, DCCT and SLM (synchrotron light monitor) are also described in this paper.
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.
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.
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.
123938232
A QCD-INSPIRED MODEL FOR THE DEUTERON FORM FACTORS IN THE INTERMEDIATE-Q2 REGION
Based on a perturbative QCD analysis of the deuteron form factors a QCD-inspired model is suggested. The contributions of helicity-flip matrix elements to the deuteron form factors are discussed. Our numerical results are consistent with the data in the intermediate-Q(2) region.
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].