Upgrade of beam energy measurement system at BEPC-II

Abstract

The beam energy measurement system is of great importance and profit for both BEPC-II accelerator and BES-III detector. The system is based on measuring the energies of Compton back-scattered photons. Many advanced techniques and precise instruments are employed to realize the highly accurate measurement of positron/electron beam energy. During five year's running period, in order to meet the requirement of data taking and improve the capacity of measurement itself, the upgradation of system is continued, which involve the component reformation of laser and optics subsystem, replacement of view-port of the laser to vacuum insertion subsystem, the purchase of electric cooling system for high purity germanium detector, and the improvement of data acquisition and processing subsystem. The upgrading of system guarantees the smooth and efficient measuring of beam energy at BEPC-II and accommodates the accurate offline energy values for further physics analysis at BES-III.

C.M.S. energy calibration in BES-III and VEPP-2000 experiments

“…In 2010 the first experiment was held with the new beam energy determination system on the BEPC-II collider. This system is more complex, cause it was designed for alternating separate measurements of the beams energies in the electron and positron rings [12][13][14]. The HPGe detector is installed in the north interaction point of the collider, and the laser beam could be delivered for interaction with either electrons or positrons.…”

Laser backscattering for beam energy calibration in collider experiments

“…In 2010 the first experiment was held with the new beam energy determination system on the BEPC-II collider. This system is more complex, cause it was designed for alternating separate measurements of the beams energies in the electron and positron rings [17][18][19]. The HPGe detector is installed in the north interaction point of the collider, and the laser beam could be delivered for interaction with either electrons or positrons.…”

“…Detailed descriptions of the systems listed above and examples of their application in physical experiments may be found in the references [11,17,19,23]. In this report we describe the common features of these installations, focusing on the details of the data acquisition and analysis.…”

Geometric alignment of the CMD-3 endcap electromagnetic calorimeter using events of two-quantum annihilation

“…to 10 32 cm −2 s −1 at the maximum center-of-mass energy √ s = 2 GeV. One of the features is the Compton backscattering method [6][7][8] to precisely measure the beam energy. The current integrated luminosity accumulated by the CMD-3 is about 60 pb −1 .…”