[en] The feasibility of building the BTCF(Beijing τ-charm Factory) on the BEPC site is being studied, but many technical difficulties remain. For the injector, full energy injection and very high beam current are still challenging problems for the BEPC linac. A lot of R and D work remains: on the X-band pulse compressor, on the high current multibunch electron gun and on the subharmonic buncher etc. (author)

[en] The compensation for transient beam loading effect requires that a modulated RF pulsed is fed to the accelerator. A new SLED system to be able to generate the modulated RF pulse in long pulse multi-bunch linac is studied. The required waveforms of SLED input pulses are computed to generate RAMP and flat-top RF pulses. The optimization method of SLED parameters is formulated. The results of cold test coincide with the theoretical prediction. RAMP and flat-top RF pulses are generated using SLED for the first time

[en] To meet the requirements of the Beijing electron positron linear accelerator upgrading, the studies on beam optics and orbit correction calculation are carried out. A program for beam optics and orbit correction calculation is developed. By means of least square method, the satisfying results are obtained. The program can actually reflect the energy variation along the LINAC. With the program, beam optics parameters can be calculated and beam orbit can be corrected on-line. And the program will be used on BEPC II LINAC

No abstract available

[en] To control the BEPC II-linac beam performance within the upgrading goals, the error effects such as the initial beam offset and the accelerator misalignment effects on the beam performance have been systematically studied with beam modeling. The most important operating jitter effects including the phasing drift jitter and the modulator's jitter effects have also been studied. The tolerances of the errors and jitters have been decided and the effective beam orbit correction scheme is further confirmed. By controlling the initial beam offset from the electron gun within ±0.3 mm, the tolerance of the accelerating structures and quadruple misalignment within ±0.2 mm, the phase drift error within ±2 degree , and the modulator's voltage jitter within ±0.1%, and by employing the phase control system and the effective orbit correction scheme, the energy spread is within ±0.5% for the injection electron and positron beams, the beam emittances of injection electron and positron beams are separately less than 0.25 mm·mrad and 1.60 mm·mrad. (authors)

[en] The BEPC II future pre-injector consists of a thermionic gun followed by two subharmonic bunchers (SHB), a travelling wave prebuncher and a travelling wave buncher. All components downstream of the gun are immersed in a solenoid field for transverse focusing. Beam dynamics simulation and optimization have been carried out with programs PARMELA and EGUN. SHBs' bunching voltage and bunching drift distance, prebuncher and buncher's phase and acceleration gradient, and solenoid field profile have been studied. The bunch charge limitation for 10 ps bunch length at the buncher exit is also investigated

[en] The structure optimization of 142.8 MHz sub-harmonic buncher has been carried out with two-dimensional Finite Difference Method software Superfish and three-dimensional Finite Integration Method software MAFIA. The method of optimizing the cavity structure is presented in this paper, and the optimized structure of the cavity is also decided. The simulation results of Superfish and MAFIA are analyzed and compared, and they are consistent with the design data. In addition, the application of methods of Superfish and MAFIA in the cavity design are also investigated

[en] The high current and short bunch of the electron beam in the BEPCII injector linac cause the wakefield effects on the beam performance dilution. These wakefield effects on longitudinal and transverse beam dynamics are systematically studied with analysis and numerical beam modeling, including the single bunch short-range wake effects and the multi-bunch long-range wake effects on beam energy, energy spread, emittance, orbit offset and primary electron beam spot size on the positron production target. The measures to effectively cure these wake effects are also studied

[en] In order to compensate the RF phase drift due to various factors, authors will establish a RF phasing system for BEPC II linac. Energy maximizing method will be used to determine the RF phase of each RF power source. A coaxial line will be used to distribute RF phase reference along the klystron gallery. The key components, such as PAD unit, I φ A units, have been developed. A minimum phasing system is established and runs successfully. (authors)

[en] To meet the upgrading goals of the BEPC II-linac, the beam modeling and studies on optimizing the optics for high current electron and positron beams are carried out. An optics-tuning scheme is defined. The effects of initial beam axis deviation and machine alignment errors on normalized beam emittance growth and on beam orbit offset are systematically studied, and the orbit correction with '1-to1' correction scheme is modeled