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Microwave undulators have great potential to be used in short-wavelength free-electron lasers. In this paper, the properties of a corrugated waveguide and its performance as an undulator cavity for a UK X-ray free-electron laser were systematically studied. The equations presented in this paper allow a fast estimation of the dimensions of the corrugated waveguide. An undulator cavity operating at 36 GHz designed for the HE11and HE12modes was investigated and the performance of both modes compared.

High-power microwave sources play an important role in the applications of the radar system, controlled fusion plasma experiments, as well as particle accelerators. Currently, the conventional klystrons operating at S-, and X-band are the main driver in high-gradient accelerators. Klystrons with MW output power have been developed at CPI, SLAC, Thales, and so on. The most powerful klystron product is able to deliver higher than 50 MW at 11.424 GHz with us pulse length. The future accelerators require higher acceleration gradient. One of the solutions is to operate the accelerating structures at a higher frequency. However, for conventional klystrons, operating at a higher frequency will significantly reduce the output power, with a factor of 1/f2. Gyro-klystrons not only have the bunching in the axial direction, which is the same as the klystrons. But also bunching at azimuthal direction due to the cyclotron resonance maser instability. It has the advantages of higher power capability as well as operating at higher frequency. MW gyro-klystrons operating at Ka-and V-band for acceleration applications are currently being developed. It is a joint project between the University of Strathclyde, UK and University of Electronic Science and Technology of China (UESTC), China. Two gyro-klystrons will be developed at the first stage. One is operating at 36 GHz for beam acceleration. From the simulation, a max output power of 1.9 MW, efficiency of 44%, gain of 39 dB and 3 dB bandwidth of 700 MHz were obtained. The other one is designed for the Compact Linear Accelerator for Research and Applications (CLARA), a Free-Electron Laser Test Facility at Daresbury Laboratory, UK. It will be used to drive the linearizer to correct the longitudinal phase space non-linearity from the RF acceleration. The operating frequency will be 48 GHz, which is 4th harmonic of the X-band linearizer. The output power of the gyro-klystron is predicted to be 1 MW if it is driven by a 100 kV, 50 A electron beam. The long-term goal is to develop gyro-klystron at similar operating frequencies but with higher output power to 20 MW.

The frequency agility of a W-band gyrotron travelling wave amplifier (gyro-TWA) was demonstrated by the amplification of a frequency-swept input signal (chirp signal). The gyro-TWA was developed to provide high output power and wide bandwidth by using a helically corrugated interaction region. In the experiment a ~0.5 W signal of linearly swept frequency bandwidth of 1 GHz was amplified and a gain of over 30 dB was measured when driven by a 40 keV, 1.5 A, axis-encircling electron beam.

This paper presents the design of a TE10-to-TE61 mode coupler for a 372 GHz gyrotron travelling wave amplifier. The optimized coupler was able to achieve an -1 dB transmission over the frequency band of 360-384 GHz. The transmission decreases by 1.2 dB when the copper conductivity of 0.5E7 S/m was used in the simulation. The designed coupler was scaled to W-band for manufacture and measurement. The measured transmission and phase response confirmed the mode coupling between the input TE10 mode and the desired TE61 mode.

Biomolecular characteristics of fossil Liquidambar from the Miocene Shengxian Formation, Tiantai, Zhejiang province in eastern China and Miocene Clarkia sediment, Idaho, U.S.A., are obtained by means of Pyrolysis-Gas chromatography-Mass spectrometry analysis (Py-GC-MS). Their modern equivalent (Liquidambar formosana) collected from Nanjing, eastern China, is also analyzed for comparison. The total ion chromatograms (TIC) of modern L. formosana leaves shows abundant pyrolysates of lignin, polysaccharide, aliphatic acid, and amino acid. However, only one polysaccharide molecule, i.e., levoglucosan, is retained in fossil Liquidambar leaves from the two Miocene sites with the Tiantai specimen possessing higher intensity. As expected, some lignin pyrolysates including benzene, phenol, guaiacol, vinylphenol and their derivatives, are detected in Miocene Tiantai L. miosinica. However, the lignin components with large molecular weight other than benzene and phenol compounds, are absent in Miocene Clarkia L. pachyphyllum. Abundant pristene and homologous series of n-alk-1-ene/n-alkane pairs with a long retention time are shown in pyrograms of both Tiantai and Clarkia fossils. Based upon our Py-GC-MS data, the molecular preservation in these Liquidambar leaf samples can be ranked as the following (from high to low quality respectively): modern sample >Tiantai sample >Clarkia sample. Vinyl phenol, an important compound, is present in modern and Tiantai Liquidambar leaves, while absent in Clarkia sample, implying that vinyl phenol may be sourced from lignin for Liquidambar leaves. Our data support the hypothesis of in situ polymerization for the origin of long-chain homologous series of n-alk-1-ene/n-alkane pairs as leaf alteration products. Our data have implications of the impact of leaf degradation toward biases for palaeoenvironmental reconstruction using stable carbon isotope of fossil plants, and suggest the importance of evaluating molecular preservation of fossil leaf tissues prior to the application of carbon isotope compositions of fossil leaves.

This study investigated the transformation of triclosan (TCS) following co-exposure to UV irradiation and ClO2. Special attention was given to understand the influencing of water quality parameters and toxicity changes during the co-exposure process. The results show that the co-exposure process prompted TCS elimination quickly and effectively, with more than 99% of TCS degraded under the experimental conditions. The molar yield ratios of 2,4-dichlorophenol/TCS (2,4-DCP/TCS) were calculated to be 35.81–74.49%; however, the by-product of 2,8-dichlorodibenzop-dioxin (2,8-Cl2DD) was not detected. The TCS degradation was sensitive to ClO2 dosage, pH, H2O2, and natural organic matter (NOM), but not to the carbonate (CO32−) concentration. Neutral and slightly alkaline condition were favorable to TCS elimination. The TCS removal rate increased from 85.33 to 99.75% when the ClO2 concentration increased from 0.25 to 1.5 mg L−1. TCS degradation can be promoted at low NOM level (1, 3, and 5 mg L−1), whereas was inhibited at high NOM concentrations of 7 and 9 mg L−1. While adding H2O2, the degradation rate of TCS increased with increasing H2O2 concentration from 1 to 3 mg L−1; however, too low or overdosed H2O2 (0.5 and 5 mg L−1) hindered TCS degradation. Based on the results of a microtox bioassay, the toxicity did not change following the co-exposure process.

The extant genus Paliurus Miller is divided into P. ramosissimus and P. spina-christi groups and is diagnostically characterized by distinctive orbicular-winged fruits with a trilocular (or often bilocular) ovary and basally triveined leaves with a subentire to serrate margin. Here, structurally preserved winged fruits and associated compressed leaves of Paliurus (Paliureae, Rhamnaceae) are reported from the Middle-Upper Miocene Shengxian Formation of Tiantai, Zhejiang, eastern China. The fruits can be identified as Paliurus microcarpa Xiang-Chuan Li sp. nov., the diagnostic characters of external morphology and anatomy of which differ from those of both extant and fossil generic members; the leaves can be designated as Paliurus sp. The species based on winged fruits, P. microcarpa, might represent an ancient intermediate link exclusively known across the P. ramosissimus and P. spina-christi groups, showing a closer affinity to the P. ramosissimus group based on the resemblant smaller fruits with a narrower wing, and to the P. spina-christi group based on the similar wing structure and texture, respectively. Morphological analyses of the present and previous fossil fruit records around the world indicate that diversification of Paliurus had begun in northern transpacific regions by the Late Eocene. The macrofossil records, i.e., fruits and leaves of Paliurus globally when projected on paleoenvironmental maps in view of changing continental positions through time (from Eocene to Miocene) display that the past distribution of the genus was much wider than the present and belongs to a tropical and warm temperate realm of the Northern Hemisphere. Therefore, the modern restricted disjunction in tropical and warm temperate regions of East Asia and South Europe (even eastwards West Asia) might represent glacial refugia for some of the generic ancient lineages to survive severe cold at least since the terminal Pliocene.