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The Shanghai soft X-ray Free-Electron Laser facility (SXFEL), which is the first X-ray FEL facility in China, is being constructed in two phases: the test facility (SXFEL-TF) and the user facility (SXFEL-UF). The test facility was initiated in 2006 and funded in 2014. The commissioning of the test facility was finished in 2020. The user facility was funded in 2016 to upgrade the accelerator energy and build two undulator lines with five experimental end-stations. The output photon energy of the user facility will cover the whole water window range. This paper presents an overview of the SXFEL facility, including considerations of the upgrade, layout and design, construction status, commissioning progress and future plans.

The investigation of the chemical effect of slurry pH on the CMP process of a C-GST film through electrochemical means reveals a conversion of polishing behavior from the cycling to mechanical mechanism as the pH level varies.

Coupling effect of chemical composition and physical structure is a key factor to construct superaerophobic electrodes. Almost all reports about superaerophobic electrodes were aimed at precisely controlling morphology of loaded materials (constructing specific structure) and ignored the due role of substrate. Nevertheless, in this work, by using high precision and controllable femtosecond laser, hierarchical micro-nano structures with superaerophobic properties were constructed on the surface of silicon substrate (fs-Si), and such special super-wettability could be successfully inherited to subsequent self-supporting electrodes through chemical synthesis. Femtosecond laser processing endowed electrodes with high electrochemical surface area, strong physical structure, and remarkable superaerophobic efficacy. As an unconventional processing method, the reconstructed morphology of substrate surface bears the responsibility of superaerophobicity, thus liberating the structural constraints on loaded materials. Since this key of coupling effect is transferred from the loaded materials to substrate, we provided a new general scheme for synthesizing superaerophobic electrodes. The successful introduction of femtosecond laser will open a new idea to synthesize self-supporting electrodes for gas-involving reactions.

Recently, TaON has become a promising photoelectrode material in the photocatalytic field owing to its suitable band gap and superior charge carrier transfer ability. In this work, we prepared a TaON/CdS photocatalytic film using a CdS nanoparticle-modified TaON film by the successive ionic layer adsorption and reaction (SILAR) method. For the first time, the ZnS nanoparticles were deposited on the TaON/CdS film using the same method. We found that pure TaON had a nanoporous morphology, thus resulting in high specific surface area and better gas adsorption capacity. Furthermore, the TaON/CdS/ZnS film displayed a highly efficient NO2 photodegradation rate under visible light irradiation owing to its stronger visible light response, photocorrosion preventive capacity, and the high separation efficiency of photo-induced electrons and holes. Interestingly, the promising TaON/CdS/ZnS film also possessed remarkable recyclability for NO2 degradation. Therefore, we suggest that the TaON/CdS/ZnS photocatalytic film might be used for the photocatalytic degradation of other pollutants or in other applications. We also put forward the feasible NO2 photocatalytic degradation mechanism for the TaON/CdS/ZnS film. From the schematic diagram, we could further obtain the photo-generated carrier transport process and NO2 photodegradation principle in detail over the ternary photocatalytic film. Moreover, the trapping experiment demonstrates that ·O2− and h+ all play significant roles in NO2 degradation under visible light irradiation.

Organic metal halide perovskite (OMHP) material shows promising applications in the photoelectrocatalytic field, but its efficiencies are unsatisfactory due to the bulk and surface carrier recombination. In this work, we used dual polyoxometalates (C4H9N)3PW12O40 and [Ag10[{Co(H2O)3}2{CoBi2W19O66(OH)4}] to modify the OMHP photoanode; the former acted to improve the quality of the perovskite film and the latter could facilitate hole transfer. Such dual modifications effectively reduce carrier recombination and thus obviously boost photoelectrocatalytic efficiency. Hence, we explored the photoelectrocatalytic oxidation of benzene into phenol in aqueous solution by using the modified OMHP photoanode. The yield of phenol in the reaction using the modified OMHP photoanode reached about 31.8%, which was obviously superior to that using the pure OMHP photoanode. Furthermore, we carried out radical scavenger studies to investigate the active species involved in the photoelectrocatalytic benzene oxidation reaction, and thus proposed the plausible mechanism of the photoelectrocatalytic oxidation of benzene into phenol over the OMHP photoanode. These results provide new insights into the development of high performance OMHP photoanodes for photoelectrocatalytic organic transformation.

Well-organized TiO2 nanorod arrays (TNRs) have increasingly attracted our attention in recent years due to their excellent photocatalytic properties. However, it is of great importance to prepare more efficient photocatalysts using a facile method towards their more widespread use. In this work, K6SiW11O39Co(ii)(H2O) (SiW11Co) and Ag nanoparticles were introduced into TNRs using spin-coating and chemical bath deposition methods. It was found that TNRs/SiW11Co/Ag composite films with an active area of only 1 cm2 exhibit highly efficient and sustainable properties for the photodegradation of NO2 and display a significant enhancement compared with P25 and pure TNRs. Photocatalytic measurements demonstrated that both SiW11Co and Ag synergistically improve the light absorption and charge separation efficiency, thus obtaining the most efficient photocatalytic performance. In addition, the probable photocatalytic mechanism and the dominating active species for NO2 photodegradation were also proposed, in order to testify the effectively enhanced photocatalytic ability of the TNRs/SiW11Co/Ag composite. Hence, the design of these polyoxometalate and metal particle co-modified TNRs may provide a new tactic for developing promising materials for photocatalytic degradation.

To further improve the performance of accelerators, the first cryogenic normal-conducting RF gun in China was designed and manufactured. As a new and attractive trend, this optimized cryogenic RF gun can generate a low-emittance beam with a short-driven laser pulse because of its promising high gradient on the cathode. In this paper, optimization of the RF design and beam dynamics, including suppression of the peak RF field and elimination of the multipole mode, is presented. In addition, the emittance growth caused by the alignment deviation and RF jitter is discussed. After the gun was manufactured, a cold test was conducted at both room temperature and cryogenic conditions. At room temperature, the field distribution was obtained by the bead pull method. Under cryogenic conditions, the RF properties, such as the coupling coefficient and quality factor, varied with temperature. The test results agreed with the design. In the cryogenic test, vibration measurements were performed. Without vibration isolation, a maximum vibration of 50 $$\mu \text{m}$$ was observed. These cold test results are the basis of the following high-power test.

The development of a high-gradient accelerating structure is underway to construct a compact proton linear accelerator for cancer treatment. Extensive experiments and numerous studies are being conducted to develop compact linear accelerators for proton therapy. Optimization of the electromagnetic and mechanical design has been performed to simplify the manufacturing process and reduce costs. A novel high-gradient structure with a low relativistic proton velocity (β), v/c = 0.38, was designed, fabricated, and tested at high power. The first full-scale prototype was also successfully tested with high radio frequency (RF) power, a repetition rate of 50 Hz, and pulse length of 3 µs to reach a high-gradient of 46 MV/m using a 50 MW S-band klystron power supply obtained from the Shanghai Soft X-ray Free Electron Laser Facility. This is the first high-power test in China, which is in line with the expected experimental goal. This study presents preliminary high-power testing of S-band standing wave accelerating structures with 11 cells. This work aims to verify the feasibility of using a high-gradient RF accelerating structure in compact proton therapy facilities. The cold test of the prototype cavity was completed in advance. Details of the high-power RF test setup, the process of RF conditioning, and the high-power results are described.

For improving the three-dimensional structure of phase-change memory devices, Ovonic threshold switch devices have received renewed attention as selectors owing to a simple production process, good scalability, and excellent performance. It can replace transistors and diodes in the available technology. In this article, we studied the GeSe-based chemical mechanical polishing process. The different concentrations of hydrogen peroxide and lysine interacting with GeSe in chemical mechanical polishing were investigated. Material characterization was performed by scanning electron microscopy and atomic force microscopy. In addition, the reaction mechanism in the chemical mechanical polishing process was analyzed by electrochemical experiments and X-ray photoelectron spectroscopy.

An S-band high-gradient accelerating structure is designed for a proton therapy linear accelerator (linac) to accommodate the new development of compact, single-room facilities and ultra-high dose rate (FLASH) radiotherapy. To optimize the design, an efficient optimization scheme is applied to improve the simulation efficiency. An S-band accelerating structure with 2856 MHz is designed with a low beta of 0.38, which is a difficult structure to achieve for a linac accelerating proton particles from 70 to 250 MeV, as a high gradient up to 50 MV/m is required. A special design involving a dual-feed coupler eliminates the dipole field effect. This paper presents all the details pertaining to the design, fabrication, and cold test results of the S-band high-gradient accelerating structure.

As an advanced treatment method in the past five years, ultra-high dose rate (FLASH) radiotherapy as a breakthrough and milestone in radiotherapy development has been verified to be much less harmful to healthy tissues in different experiments. FLASH treatments require an instantaneous dose rate as high as hundreds of grays per second to complete the treatment in less than 100 ms. Current proton therapy facilities with the spread-out of the Bragg peak formed by different energy layers, to our knowledge, cannot easily achieve an adequate dose rate for FLASH treatments because the energy layer switch or gantry rotation of current facilities requires a few seconds, which is relatively long. A new design for a therapy facility based on a proton linear accelerator (linac) for FLASH treatment is proposed herein. It is designed under two criteria: no mechanical motion and no magnetic field variation. The new therapy facility can achieve an ultra-high dose rate of up to 300 Gy/s; however, it delivers an instantaneous dose of 30 Gy within 100 ms to complete a typical FLASH treatment. The design includes a compact proton linac with permanent magnets, a fast beam kicker in both azimuth and elevation angles, a fixed gantry with a static superconducting coil to steer proton bunches with all energy, a fast beam scanner using radio-frequency (RF) deflectors, and a fast low-level RF system. All relevant principles and conceptual proposals are presented herein.

Bismuth vanadate (BiVO4) as an outstanding semiconductor material has been extensively used in visible-light-driven photocatalytic oxidation. However, the fast electron-hole recombination on the surface of BiVO4 photoanode impairs its photoelectrochemical oxidation performance. In this work, we demonstrate, for the first time, that a cobalt-polyoxometalate (Ag10[Co4(H2O)2(PW9O34)2], PW9Co) is exploited as a hole extraction layer on the surface of BiVO4 photoanode for boosting photoelectrochemical activity by promoting hole extraction and transfer. Compared to the pure BiVO4 photoanode, the PW9Co-modified BiVO4 photoanode in photoelectrochemical water oxidation reaction exhibited a higher photocurrent density of 3.06 mA cm−2 at 1.23 V vs. RHE under AM 1.5G illumination, achieving a 3.3-fold improvement in photocurrent density. Furthermore, we performed a photoelectrochemical reaction of oxidizing benzyl alcohol into benzaldehyde, in which the reaction yield of using the modified BiVO4 photoanode is significantly superior to the pure BiVO4 photoanode. These results prove that a rational selection of cobalt-polyoxometalate as a hole extraction layer can efficiently enhance the photoelectrochemical oxidation activity of BiVO4 photoanode.

An X-band transverse-deflecting structure is a crucial RF unit for bunch-length measurement conducted at the Shanghai Soft-X-ray Free Electron Laser Facility (SXFEL) at the Shanghai Institute of Applied Physics (SINAP), Chinese Academy of Sciences. The target of this prototype deflector is to operate at 30 MW to have a deflection of 10 MV/structure to realize 20-fs resolution in a full-size structure (0.6 meters long, used on user facility of SXFEL), which satisfies the requirement of the linac beam size measurement at 840 MeV. The program was started in 2010 focusing on X-band deflectors, including design, fabrication, and RF measurement. The electrical tuning of the deflector was successfully done using a unique “cage”-type bead. Recently, a high-power test was conducted at KEK on the first prototype deflector. The high-gradient features at the nominal gradient was proven, but the further increase of power and pulse width was limited at 45 MW with a 173-ns pulse width due to approaching the feasible limit of the modified pointing vector value 5 MW/mm2. In this final stage, frequent breakdowns near the badly brazed point occurred and further conditioning had to be suspended owing to limited available time.

Organic metal halide perovskite material has attracted intense interest in the photovoltaic field due to its excellent optoelectronic properties, but the extreme susceptibility of organolead halide...

A water-soluble titanium(iv)-oxo-cluster (K6[K3Ti3O4(O2)3 (C7H3O4N)3(OH2)2]Cl·4H2O) 1 has been successfully synthesized and it shows a 2D layered structure through the connection of potassium ions. Its application in photoelectrooxidation activity for DA was also investigated primarily.

Three-dimensional hierarchical nanoflowers self-assembled with the orthorhombic molybdenum oxide (α-MoO3) nanoflowers were synthesized by the modified hydrothermal method. The structure characterizations of the three-dimensional α-MoO3 nanoflowers were carried out by scanning electron microscope (SEM), Energy Disperse Spectroscopy (EDS), X-ray diffraction (XRD) and nitrogen adsorption-desorption measurement. Moreover, the three-dimensional α-MoO3 nanoflowers as photocatalyst exhibited enhanced photocatalytic activity towards photodegradation of Rhodamine B (RhB) under xenon (Xe) lamp irradiation. The results of SEM, EDS, XRD and nitrogen adsorption-desorption measurement showed the three-dimensional α-MoO3 nanoflowers have a better morphology, pore size (7.99 nm) and surface areas (50.788 m2 g−1) than hexagonal MoO3 (h-MoO3) nanosheets, photocatalytic activity studies confirmed that the three-dimensional α-MoO3 nanoflowers photocatalyst exhibits a high visible-light-driven activity for photodegradation of RhB solution of 91.57% within 160 min under Xe lamp irradiation. A mechanism was also proposed for the degradation of RhB by three-dimensional α-MoO3 nanoflowers.

The increasing demands for electron beams with high quality and low timing jitter for accelerator-based applications such as ultrafast electron microscopy (UEM) and ultrafast electron diffraction (UED) have stimulated active efforts to develop suitable injectors for these accelerators. One promising direction in this regard is using of a bimodal rf gun operating in fundamental mode and a phase-locked harmonically-related higher mode. Work reported in this paper is on analysis and design of a bimodal rf gun operating in S-band as the fundamental and C-band as the second-harmonic modes. The rf design for such an rf gun includes the new design like directional coupler and rectangular mode launcher, which presented good transmission, low reflective cross-talk, and allowed multiple iterations of the modification. Compared to the fundamental mode, the new design achieved reduction in rf emittance and energy spread for MeV UEM initial distribution, and reduction in slope of flight time as function of injection phase for MeV UED applications.

Objective This study aimed to investigate the effect of SIK2 on cisplatin resistance induced by aerobic glycolysis in breast cancer cells and its potential mechanism. Methods qRT-PCR and Western blot were used to detect SIK2 mRNA and protein levels. Cisplatin (DDP) resistant cell lines of breast cancer cells were established, CCK-8 was used to measure and evaluate the viability, and Transwell was used to evaluate the cell invasion capability. Flow cytometry was adopted to evaluate the apoptosis rate. The glycolysis level was evaluated by measuring glucose consumption and lactic acid production. The protein levels of p-PI3K, p- protein kinase B (Akt) and p-mTOR were determined by western blot. Results SIK2 is highly expressed in breast cancer tissues and cells compared with adjacent tissues and normal human breast epithelial cells, and has higher diagnostic value for breast cancer. Silencing SIK2 expression can inhibit proliferation and invasion of breast cancer cells and induce their apoptosis. In addition, SIK2 knockdown inhibits glycolysis, reverses the resistance of drug-resistant cells to cisplatin, and inhibits PI3K/AKT/mTOR signaling pathway. When LY294002 is used to inhibit PI3K/AKT/mTOR signaling pathway, the effect of Sh-SIK2 on aerobic glycolysis of breast cancer cells can be reversed. Conclusion SIK2 can promote cisplatin resistance caused by aerobic glycolysis of breast cancer cells through PI3K/AKT/mTOR signaling pathway, which may be a new target to improve cisplatin resistance of breast cancer cells.

Recently, TaON has become a promising photoelectrode material in the photocatalytic field owing to its suitable band gap and superior charge carrier transfer ability. In this work, we prepared a TaON/CdS photocatalytic film using a CdS nanoparticle-modified TaON film by the successive ionic layer adsorption and reaction (SILAR) method. For the first time, the ZnS nanoparticles were deposited on the TaON/CdS film using the same method. We found that pure TaON had a nanoporous morphology, thus resulting in high specific surface area and better gas adsorption capacity. Furthermore, the TaON/CdS/ZnS film displayed a highly efficient NO

An ultrafast electron diffraction (UED) facility is located at Shanghai Jiao Tong University. The layout of the UED is divided into two modules. The accelerating module has one S-band photocathode RF gun, one C-band harmonic buncher, and one C-band deflector. The power-generating module has one S-band klystron and one C-band klystron. To meet the high-precision requirements, a MicroTCA.4-based low level radio frequency (LLRF) system is used to provide a stable RF field in the cavities. In this paper, we introduce the RF distributions, LLRF system, firmware and software of the feedback controller, and field stability of the RF gun; and present an analysis of the measurement results for UED.

An X-band high gradient accelerating structure is a challenging technology for implementation in advanced electron linear accelerator facilities. The present work discusses the design of an X-band accelerating structure for dedicated application to a compact hard X-ray free electron laser facility at the Shanghai Institute of Applied Physics, and numerous design optimizations are conducted with consideration for radio frequency (RF) breakdown, RF efficiency, short-range wakefields, and dipole/quadrupole field modes, to ensure good beam quality and a high accelerating gradient. The designed X-band accelerating structure is a constant gradient structure with a 4π/5 operating mode and input and output dual-feed couplers in a racetrack shape. The design process employs a newly developed effective optimization procedure for optimization of the X-band accelerating structure. In addition, the specific design of couplers providing high beam quality by eliminating dipole field components and reducing quadrupole field components is discussed in detail.

A novel composite room temperature gas sensor based on an In2O3 nanorod-decorated reduced graphene oxide composite (In2O3 NR/rGO composite) was successfully synthesized via a facile reflux method. In this synthesis, In3+ and urea were adsorbed on GO through electrostatic interactions in a water solution. The subsequent reflux treatment led to the transformation of the In(OH)3 nanorods coated on GO and also to the reduction of graphene oxide. We demonstrate that the composite can detect NOx gas with a response of 1.45, a fast response time of 25.0 s for 97.0 ppm NOx and a low detection limit of 970 ppb at room temperature. Compared with the pure In2O3 NRs, the composite has a faster response within 30.0 s over the whole range of NOx concentration. The enhanced sensing properties are attributed to the synergy of the superior conductivity of rGO and the nanostructure of the In2O3 NR/rGO composite. The present strategy for combining various hydroxide and nanoscale building blocks into integrated 3D structures will open new opportunities for designing and synthesizing multifunctional composites.

A tuning method augmented by the bead-pull technique based on nonresonant perturbation field distribution measurements has been widely applied for traveling-wave (TW) accelerating structures. The method is also suitable for deflecting structures, but some key considerations of the field components of the HEM 11 mode and the selection of bead merit discussion. A “cage”-type perturbing object has been designed, fabricated and applied in nonresonant perturbation measurements. Measurements on an S-band TW deflecting structure are carried out, and the measurement and tuning method will be used on the newly developed X-band deflecting structure at Shanghai Institute of Applied Physics.

A novel variable C-band radio-frequency (RF) power splitter was designed at Shanghai Institute of Applied Physics, Chinese Academy of Sciences. Using three RF impedance combiners, an H-bend, and an RF polarizer, this new power splitter is much more compact than a traditionally designed splitter, which comprises three 3-dB hybrids. The parameters were optimized to achieve good matching and minimize reflection. Here, the RF design of the new C-band variable power splitter is presented.

A C-band photocathode injector composed of a 3.6-cell C-band photocathode RF gun and two 1.8-m C-band accelerating structures is proposed. The injector is a low emittance electron source for free electron lasers (FEL) and other compact light sources. The RF structure of the cavities is designed with 2D SUPERFISH simulation. The beam dynamic study in ASTRA helps rectify the 2D RF simulation. To feed the cavities, a design of extracoaxial coupler with RF gun structure is presented. With compact focusing solenoids, for 0.25 nC bunch charge, the final energy can reach 6.9 MeV energy and the 95% emittance can be as low as 0.23 mm mrad (95%). All the details of RF design and beam dynamics studies are presented in this paper, and the design satisfied the requirements of FEL and other applications.

A compact 15.0-MeV, 1.5-kW electron linear accelerator (LINAC) was successfully constructed to provide an electron beam for the first photoneutron source at the Shanghai Institute of Applied Physics, Shanghai, China. This LINAC consists of five main parts: a thermal cathode grid-controlled electron gun, a pre-buncher, a variable-phase-velocity buncher, a light-speed accelerating structure, and a high-power transportation beamline. A digital feedforward radio frequency compensator is adopted to reduce the energy spread caused by the transient beam loading effect. Furthermore, a real-time electron gun emission feedback algorithm is used to keep the beam stable. After months of efforts, all the beam parameters successfully met the requirements of the facility. In this paper, the beam commissioning process and performance of the LINAC are presented.

This work presents an optimized damping waveguide structure designed to satisfy the radio frequency parameters and long-range transverse wakefield suppression of the 380 GeV Compact Linear Collider facility currently under study. Here, the elliptical shape of the iris and the wall shape of the damping waveguides are both optimized to reduce the magnitudes of surface electromagnetic fields. The widths of the waveguide openings of the entire sequence of damping waveguides are also decreased linearly with respect to the direction of beam propagation to strongly suppress long-range transverse wakefields and to maintain the stability of the beam. The position of the high-order-mode damping loads in the waveguide structure is also studied to make the damping waveguide structure more compact while satisfying all design targets.

A serial of CdS/POM (POM denotes polyoxometalate: P2MoxW18-x, x = 3, 9, 15) nanospheres were fabricated through electrostatic self-assembly method. For the first time, the semiconductor properties of the three polyoxometalates were investigated to direct the rational design of the type-II heterojunction photocatalysts. The morphology and semiconducting properties of the as-prepared materials were characterized by using X-ray powder diffraction, scanning electron microscopy, UV–vis diffuse reflectance spectra, Mott-Schottky plots, surface photovoltage spectroscopy and time-resolved photocurrent curves. The band gap of P2Mo3W15, P2Mo9W9 and P2Mo15W3 is taken respectively to be 2.34 eV, 2.26 eV and 2.15 eV. The average diameters of CdS and CdS/P2MoxW18-x (X = 3, 9, 15) nanospheres are all around 80–100 nm, and CdS/P2MoxW18-x (X = 3, 9, 15) nanospheres have better photoelectric performance than pure CdS. The formation of type II heterostructure between CdS and P2MoxW18-x could promote the separation and transfer of photoinduced electron-hole pairs, so the photocatalytic activities of CdS/POM nanospheres for Cr(VI) reduction were improved significantly. Among them, the CdS/P2Mo15W3 photocatalyst exhibited the highest photocatalytic yield of 64% for the Cr(VI) removal. Our study provides new insight into developing novel CdS/P2MoxW18-x nanocomposite photocatalysts for environmental applications.

Compared to the conventional phase change materials, the new phase change material Ta-Sb2Te3 has the advantages of excellent data retention and good material stability. In this letter, the etching characteristics of Ta-Sb2Te3 were studied by using CF4/Ar. The results showed that when CF4/Ar = 25/25, the etching power was 600 W and the etching pressure was 2.5 Pa, the etching speed was up to 61 nm/min. The etching pattern of Ta-Sb2Te3 film had a smooth side wall and good perpendicularity (close to 90°), smooth surface of the etching (RMS was 0.51nm), and the etching uniformity was fine. Furthermore, the mechanism of this etching process was analyzed by X-ray photoelectron spectroscopy (XPS). The main damage mechanism of ICP etching in CF4/Ar was studied by X-ray diffraction (XRD).

C-band RF acceleration is a crucial technology for the compact Free Electron Laser (FEL) facility at the Shanghai Institute of Applied Physics (SINAP), Chinese Academy of Sciences. A project focusing on C-band RF acceleration technology was launched in 2008, based on high-gradient accelerating structures powered by klystron and pulse compressor units. The target accelerating gradient is 40 MV/m or higher. Recently one prototype of C-band RF unit, consisting of a 1.8 m accelerating structure and a klystron with a TE0115 mode pulse compressor, has been tested with high-power and electron beam. Stable operation at 40 MV/m was demonstrated and, 50 MV/m approached by the end of the test. This paper introduces the C-band R&D program at SINAP and presents the experiment results of high-power and beam tests.

In this work, we report a one-step synthesis of spherical flower-shaped tungsten oxide (WO3) nanostructures by using polyethylene glycol (PEG) as a surfactant. The PEG played a crucial role in controlling the final morphology of the WO3 product. The structure and morphology of the product were characterized by carrying out XRD and SEM experiments. These characterizations indicated these three-dimensional flower-shaped nanostructures to be well crystallized, to have a uniform morphology with an average diameter of 3 μm, and to consist of many two-dimensional nanosheets. The flower-shaped WO3 particles exhibited excellent room-temperature NOx gas-sensing performance, including a sensitivity as high as 80%, a short response time of 4.5 s to 97 ppm NOx, and a low detection limit of 970 ppb. The excellent performance was due to the structure and morphology of the WO3 product.

Modification of semiconductor materials by polyoxometalates (POMs) is a promising strategy for increasing their photoelectrocatalytic (PEC) activity. In this work, we synthesized POM-modified CdS composite nanocrystals based on three kinds of Keggin-type mixed-addendum Mo/W POMs (Ag3PMo3W9O40, Ag3PMo6W6O40, and Ag3PMo9W3O40). This is the first report on the semiconductor properties of the three Keggin-type mixed-addendum Mo/W POMs. Their PEC performances were studied by transient photocurrent responses, electrochemical impedance spectroscopy, and PEC oxidation of As(III) to As(V). The PEC performances of POM-modified CdS composite nanocrystals (CdS/Ag3PMo3W9O40, CdS/Ag3PMo6W6O40, and CdS/Ag3PMo9W3O40) were superior to the performance of pure CdS nanocrystals. CdS/Ag3PMo3W9O40 composite nanocrystals exhibited the highest efficiency for the PEC oxidation of As(III) to As(V), which was about 85% higher than that of the pure CdS nanocrystals. The present study provides insight into developing novel composite nanocrystals with Keggin-type mixed Mo/W POMs for efficient PEC oxidation.

Full utilization of the incident light is an effective strategy to enhance photovoltaic performance of perovskite solar cells (PSCs). Here, we used lanthanide-containing polyoxometalate Na9[EuW10O36] (EuW10) as a luminescent down-conversion material incorporated in mesoporous TiO2 layer for boosting the power conversion efficiency (PCE) of the printable hole transport material-free PSCs. The EuW10 can convert the high energy photons into the low energy visible photons matched well with the absorption of perovskite, so that photogenerated current carriers increase substantially. This research represents the first example of using lanthanide-containing polyoxometalate as down-conversion materials to effectively improve PCE in solar cells. Compared with pristine TiO2 based PSCs, the EuW10-TiO2 based PSCs showed an enhanced power conversion efficiency (PCE) from 11.42% to 14.36% and obtained a remarkable photocurrent density of 23.46 mA/cm2. Besides, the EuW10-TiO2 based device exhibited a better long-term stability, which could maintain 98% initial efficiency after storage for 14 days. Since the efficiency of the printable perovskite solar cells has been a key factor to achieve commercial implementations, we consider that the results from this work demonstrate a new kind of down-conversion materials to boost PCE and stability.

A novel Bimodal Electron Gun is designed to apply microwaves at two harmonically-related frequencies in a half-cell RF gun to increase the RF breakdown threshold. This stratagem is intended to allow the RF gun structure to support a high acceleration gradient as well as to manipulate the emittance evolution in the half cell. The superposition of the harmonic field components can provide an engineered spatiotemporal distribution of the cathode field strength and phase by selecting a proper amplitude ratio and phase relationship between the first and second harmonic RF field components. This approach provides multiple control knobs over the cathode field, bunch length, and bunch charge density, and thus the suppression of the space charge effect and RF nonlinearity. The recent status of the Bimodal Electron Gun R&D is presented, including the designs of the novel two frequency directional coupler and rectangular-to-coaxial mode launchers.

Assisted by the bead pull technique, nonresonant perturbation theory is applied for measuring and tuning the field of the linac accelerating structure. The method is capable of making non-touching amplitude and phase measurements, real time mismatch feedback and field tuning. Some key considerations of the measurement system and of a C-band traveling-wave structure are discussed, and the bead pull measurement and the tuning of the C-band traveling-wave linac accelerating structure are presented at last.

The research and development of a C-band (5712 MHz) high gradient traveling-wave accelerating structure has been in progress for some years at the Shanghai Institute of Applied Physics, Chinese Academy of Sciences. Conceptual design of the accelerating structure has been accomplished, and verified by cold testing an experimental model. The first prototype structure is now ready for high RF power tests. To develop a robust high gradient C-band accelerating structure, an optimized constant gradient structure with a 4π/5 operating mode for future X-ray Free Electron Laser facilities is proposed in this paper. This scheme can improve the breakdown stability and beam quality. The high power RF system, four operating modes and disk iris shape are analyzed and optimized.