Preliminary study on detection and cleaning of parasitic bunches

Abstract

To establish a nuclear resonant scattering beamline at the High Energy Photon Source (HEPS), it is essential to develop tools for detection and cleaning of parasitic bunches, for meeting the stringent demands on bunch purity. To this end, a novel time-correlated singlephoton counting system was implemented at the electron storage ring of the Beijing Electron-Positron Collider II (BEPCII). The purity deterioration process over a weeklong operation was recorded by the system. In this study, the mechanism of impurity growth was analyzed by numerical methods and validated on measurements. The agreement between the experimental results and the calculation was fairly good. Two main sources of parasitic bunches, pre-accelerators and the Touschek scattering were confirmed. A bunch-cleaning technique, based on a sinusoidal signal mixed with a pseudo-square wave, was also developed and implemented, and its capability to improve the bunch purity to the level of 10 -7 was experimentally demonstrated. We present the experimental setup, principle, and measurement results of a system for detection and cleaning of parasitic bunches.

Beam position monitor design for the High Energy Photon Source

“…The single-bunch charge is as high as 15 nC in the highbunch charge mode [28]. Table 5 summarizes the BPM requirements of the HEPS.…”

“…where a is the radius of the interface between the two dielectrics and ε 1 and ε 2 are the relative permittivities of the inner and outer dielectric materials, respectively. The impedance can be calculated by substituting equation (29) into equation (28). The TDR and x-ray tomography results for the two button prototypes are shown in figures 14(b)-(e), respectively.…”

Using a pre-kicker to ensure safe extractions from the HEPS storage ring

“…These two aspects introduce trade-offs in the selection of pre-kicker parameters. In principle, a bunch-by-bunch feedback system or a system similar to that used for parasitic bunch cleaning [15] can also excite and dilute a bunch. However, these techniques have a much smaller deflection amplitude compared to a pre-kicker system and generally require the application of multiple kicks in a resonant manner to dilute the bunch.…”