Utilization of transverse deflecting RF cavities in the designed QBA lattice of 3 GeV Taiwan Photon Source

Abstract

A pair of superconducting transverse deflecting RF cavities has been studied in the QBA low emittance lattices of the 3 GeV TPS for generating ultra short X-ray pulses. Three configurations with different locations for the two cavities in a super-period of the TPS ring are investigated. During numerous turns of the electron tracking, the nonlinear effects between the cavities, the energy spread, the momentum compaction factor, and the synchrotron radiation effects are taken into account. The configuration with positioning the RF deflectors between the QBA cells in each super-period as an optimum arrangement gives rise to better quality electron bunches and radiated photon pulses. The FWHM of the radiated photon pulses of about 540 fs with an acceptable intensity is attained by optimizing the compression optical elements of the TPS photon beam line. Furthermore, the effects of the electron bunch length are studied by alternatively employing an accelerating RF cavity operating with 1.1 MV and 3.0 MV, respectively. The operation of the accelerating RF cavity at 3.0 MV improved the intensity of the photon pulses up to 30% and reduced the equilibrium vertical emittance down to 70 pm-rad. The error tolerance for the deflecting cavities, QBA lattice and injection process are also evaluated.

Computer simulation of bunch lengthening effects caused by a third harmonic cavity in conjunction with deflecting cavities in 3 GeV Taiwan Photon Source

“…Although the first kick is almost reversed by the second deflector but the emittance growth is inevitable. Apart from errors which are characteristics of a real machine, even for an ideal storage ring, perfect elimination of the first kick by the second deflector does not happen [1]. Degradation of the transverse emittance is mainly related to the nonlinearities and coupling of the interior sextupoles (the sextupoles that are between the deflectors), non-zero momentum compaction factor that generates a variation of the time-of-flight of electrons, energy spread, and synchrotron radiation effects.…”

“…Degradation of the transverse emittance is mainly related to the nonlinearities and coupling of the interior sextupoles (the sextupoles that are between the deflectors), non-zero momentum compaction factor that generates a variation of the time-of-flight of electrons, energy spread, and synchrotron radiation effects. For an optimum arrangement, the deflectors are situated in the middle of the two QBA cells in the super-period of TPS as shown in figure 3 [1]. Two dispersive short straight sections are devoted to the deflectors and the ID is placed at a free dispersive straight section between the deflectors.…”

“…This range of pulse duration is sufficient for numerous experiments but shorter pulses of subpicoseconds radiations are required for extending the scientific frontier. For the intense subpicosecond X-ray pulses as an important feature of the machine we decided to investigate the feasibility of producing the ultra-short X-ray pulses with the 3 GeV Taiwan Photon Source (TPS) in the Quadruple Bend Achromat (QBA) design [1]. The designed QBA lattice in TPS [2] by providing a small beam emittance with several zero dispersive straight sections motivated us to study the short bunch operation by employing a pair of superconducting deflecting RF cavities (crab cavities) [3]- [6].…”