LLRF controls in SuperKEKB Phase-1 commissioning
First beam commissioning of SuperKEKB (Phase-1), which is an asymmetry double ring collider of 7-GeV electron and 4-GeV positron beams, which had started from February, has been successfully accomplished at the end of June 2016, and the desired beam current for Phase-1 was achieved in both rings. This paper summarize the operation results related to low level RF (LLRF) control issues during the Phase-1 commissioning, including the system tuning, the coupled bunch instability and the bunch gap transient effect. RF system of SuperKEKB consists of about thirty klystron stations in both rings. Newly developed LLRF control systems were applied to the nine stations among the thirty for Phase-1. The RF reference signal distribution system has been also upgraded for SuperKEKB. These new systems worked well without serious problem and they contributed to smooth progress of the commissioning. The old existing systems, which had been used in the KEKB operation, were still reused for the most stations, and they also worked as soundly as performed in the KEKB operation.
Beam Loading in High-Energy Storage Rings
The analysis of beam loading in the RF systems olhighenergy storage rings (for example, the PEP e-e+ ring ) is complicated by the fact that the time, Tb, between the passage of successive bunches is comparable to the cavity filling time, Tf. In this paper, beam loading expressions are first summarized for the usual case in which Th << Tt. The theory of phase oscillations in the heavily-bea&loa&d case is considered, and the dependence of the synchroixon frequency and damping constant for the oscillations on beam current and cavity.tuningis calculated. Expressions for beam loading are then derived which are valid for any value of the ratio Tb/Tf. It is shown that, for the proposed PEP e-e+ ring parameters, the klystron power required is increased by about 3% over that calculated using the standard beam loading expressions. Finally, the analysis is extended to take into account the additional losses associated with the excitation of higher-order cavity modes. A rough numerical estimate is made of the loss enhancement to be expected for the PEP RF system. It is concluded that this loss enhancement might be substantial unless appropriate measures are taken in the design and tuning of the accelerating structure.
Chemical constituents and chemotaxonomic study of Glycyrrhiza pallidiflora maxim
Abstract Phytochemical study of Glycyrrhiza pallidiflora Maxim. gave seventeen compounds, including two sterols (3 and 4), four triterpenes (1, 2, 5, 6), ten flavones (7, 9–17), and one pterocarpan (8). The chemotaxonomic significance of G. pallidiflora was discussed, which indicated the close relationship between G. pallidiflora with other species of Glycyrrhiza. Moreover, pallidiflorin can be served as a fingerprint for G. pallidiflora, macedonic acid and echinatin can be recognized as biomarkers for Glycyrrhiza, while formononetin, afrormosin and calycosin may be typical second metabolites for Papilionoideae.