Filling Pattern of Volcanostratigraphy of Cenozoic Volcanic Rocks in the Changbaishan Area and Possible Future Eruptions

The Cenozoic volcanostratigraphy in the Changbaishan area had complex building processes.Twenty-two eruption periods have been determined from the Wangtian＇e, Touxi, and Changbaishan volcanoes. The complex volcanostratigraphy of the Changbaishan area can be divided into four types of filling patterns from bottom to top. They are lava flows filling in valleys（LFFV）, lava flows filling in platform（LFFP）, lava flows formed the cone（LFFC）, and pyroclastic Flow filling in crater or valleys（PFFC/V）. LFFV has been divided into four layers and terminates as a lateral overlap. The topography of LFFV, which is controlled by the landform, is lens shaped with a wide flat top and narrow bottom.LFFP has been divided into three layers and terminates as a lateral downlap. The topography of LFFP is sheet and tabular shaped with a narrow top and wide bottom. It has large width to thickness ratio. It was built by multiple eruptive centers distributed along the fissure. The topography of LFFC, which is located above the LFFP, has a hummocky shape with a narrow sloping top and a wide flat bottom. It terminates as a later downlap or backstepping. It has large width to thickness ratio. It was built by a single eruptive center. The topography of PFFC/V, which located above the LFFC, LFFP, or valley, has the shape of fan and terminates as a lateral downlap or overlap. It has a small width to thickness ratio and was built by a single eruptive center. The filling pattern is controlled by temperature, SiO_2 content,volatile content, magma volume, and the paleolandform. In the short term, the eruptive production of the Changbaishan area is comenditic ash or pumice of a Plinian type eruption. The eruptive volume in future should be smaller than that of the Baguamiao period, and the filling pattern should be PFFC/V,which may cause huge damage to adjacent areas.

Fluorescence lifetime measurement from a designated single-bunch in the BEPCⅡ colliding mode

Fluorescence lifetime measurement in the time domain requires excitation from a well separated single bunch using synchrotron light sources. In the colliding mode of the Beijing Electron Positron Collider Ⅱ （BEPCⅡ）, a hybrid filling pattern was realized such that a single bunch was placed in the middle of a large gap between two multi-bunch groups. Detection of fluorescence lifetime, based on the excitation of the light pulse from this designated single-bunch, was established at Beamline 4B8 of the Beijing Synchrotron Radiation Facility （BSRF）. The timing signal of the BEPCII was utilized as a trigger to gate this fluorescence event. L-Tryptophan amino acid, a known lifetime standard, was selected to assess the lifetime measurement performance. The measured lifetime was consistent in both colliding and single-bunch mode with the time resolution down to 450 ps. Moreover, both the bunch purity and the fine structure of the hybrid filling pattern were characterized.

Beam-induced HOM power in CEPC collider ring cavity

Background The power loss of cavity high-order modes(HOMs)is a key issue in Circular Electron and Positron Collider(CEPC)RF system design.A large HOM power may cause a quench of SC cavity.Purpose The purpose of this article is to study the beam-induced HOM power for CEPC collider ring.The factors influencing the cavity HOM power are also investigated.Methods Starting with the beam filling patterns,the beam spectrums of different beam time structures are deduced.Then,the longitudinal impedance is simulated for CEPC 2-cell 650 MHz cavity.Finally,the cavity HOM power is calculated for CEPC CDR design.Results The cavity HOM power is 459 W for Higgs,506 W for W and 1026 W for Z-pole.These values are smaller than the average values.There is no overlap between beam spectral lines and cavity HOM frequency.Conclusion The filling patterns of CEPC CDR Higgs,W and Z are safe.The dangerous filling patterns can be identified for CEPC Z-pole by scanning different parameters.