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.
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.
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.
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.
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.
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.
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.
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.
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.