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.
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.
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.
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.
121084890
Detection methods at reactor neutrino experiments
Abstract In 2011 and 2012, the smallest neutrino mixing angle θ 13 was determined to be unexpected large by reactor neutrino experiments Daya Bay, Double Chooz, and RENO, and accelerator experiments T2K and MINOS. The most precise measurement is sin 2 2 θ 13 = 0.089 ± 0.010 ( stat . ) ± 0.005 ( syst . ) , provided by Daya Bay. The measurement of θ 13 opened the gateway to the mass hierarchy and CP phase measurements. It also marked the beginning of precision measurements in neutrino studies. With near-far relative measurement and improvements in detector design, the relative precision of neutrino detectors reached 0.2%. Detection methods for reactor neutrinos are reviewed. The highlighted techniques include gadolinium-doped liquid scintillator, three-layer detectors, functionally identical detectors, reflective panel, background shielding, etc. The next generation reactor neutrino experiment Daya Bay II and its technical challenges are briefly described.
125502899
Daya Bay reactor neutrino experiment
119235151
Higgs decay to dark matter in low energy SUSY: is it detectable at the LHC?
A bstractDue to the limited statistics so far accumulated in the Higgs boson search at the LHC, the Higgs boson property has not yet been tightly constrained and it is still allowed for the Higgs boson to decay invisibly to dark matter with a sizable branching ratio. In this work, we perform a comparative study for the Higgs decay to neutralino dark matter by considering three different low energy SUSY models: the minimal supersymmetric standard model (MSSM), the next-to-minimal supersymmetric standard models (NMSSM) and the nearly minimal supersymmetric standard model (nMSSM). Under current experimental constraints at 2σ level (including the muon g − 2 and the dark matter relic density), we scan over the parameter space of each model. Then in the allowed parameter space we calculate the branching ratio of the SM-like Higgs decay to neutralino dark matter and examine its observability at the LHC by considering three production channels: the weak boson fusion VV → h, the associated production with a Z-boson pp → hZ + X or a pair of top quarks $pp \to ht\overline t + X$. We find that in the MSSM such a decay is far below the detectable level; while in both the NMSSM and nMSSM the decay branching ratio can be large enough to be observable at the LHC. We conclude that at the LHC the interplay of detecting such an invisible decay and the visible di-photon decay may allow for a discrimination of different SUSY models.