Transverse mode-coupling instability with longitudinal impedance

Transverse mode-coupling instability(TMCI)is a dangerous transverse single-bunch instability that can lead to severe par-ticle loss.The mechanism of TMCI can be explained by the coupling of transverse coherent oscillation modes owing to the transverse short-range wakefield(i.e.,the transverse broadband impedance).Recent studies on future circular colliders,e.g.,FCC-ee,showed that the threshold of TMCI decreased significantly when both longitudinal and transverse impedances were included.We performed computations for the circular electron-positron collider(CEPC)and observed a similar phenom-enon.Systematic studies on the influence of longitudinal impedance on the TMCI threshold were conducted.We concluded that the imaginary part of the longitudinal impedance,which caused a reduction in the incoherent synchrotron tune,was the primary reason for the reduction in the TMCI threshold.Additionally,the real part of the longitudinal impedance assists in increasing the TMCI threshold.

Influences of harmonic cavities on single-bunch instabilities in electron storage rings

Harmonic cavities(HCs)are widely used in electron storage rings,mainly to increase the Touschek lifetime by lengthening bunches.HCs have become critical components of almost all fourth-generation synchrotron light sources.In addition to the benefits of increasing the Touschek lifetime,they also affect the collective beam instabilities in electron storage rings.However,the influ-ence of HC settings on collective beam instabilities is still not well understood.HCs are typically designed to operate under so-called ideal lengthening conditions,which do not necessarily optimize the suppression of collective beam instabilities.We therefore extended earlier studies of col-lective beam instabilities to consider more general HC settings.We present preliminary studies and analyses of the influences of different HC settings on microwave and transverse mode-coupling instabilities.

Effect of lipopolysaccharide on the hemocyte apoptosis of Eriocheir sinensis

In the present study, we investigated the possible toxicity mechanism of lipopolysaccharide （LPS） extracted from Gram-negative bacteria in Eriocheir sinensis hemocytes. Apoptotic hemocytes and reactive oxygen species （ROS） production induced by the LPS were monitored by the combination of flow cytometry and microscope observation. It was shown that LPS induced serious damage on the DNA and morphological changes in hemocytes, including cell shrinkage, fracture of nucleus membrane, margination, condensation and fragmentation of chromatin, and formation of apoptotic bodies indicating obvious hemocyte apoptosis. As compared with the control group, the apoptotic cell ratio increased to 30.61% and 39.01% after 1-h exposure and 57.72% and 75.01% after 2-h exposure to 1 and 10 μg/ml LPS, respectively （P〈0.05）. Significant outburst of ROS production was observed in LPS-treated hemocytes with approximately 176.6% of relative dichlorofluorescein mean fluorescence at 1-h exposure, followed by a drastic decline （P〈0.05）. These results indicated that LPS would induce oxidative stress on hemocytes from E. sinensis and cause ROS burst, DNA damage, and subsequently apoptosis. The process of ROS-mediated apoptosis might be one of the potential toxicity mechanisms of LPS on crustacean hemocytes.