Gallium Arsenide preparation and QE Lifetime Studies using the ALICE Photocathode Preparation Facility

In recent years, Gallium Arsenide (GaAs) type photocathodes have become widely used as electron sources in modern Energy Recovery Linac based light sources such as the Accelerators and Lasers in Combined Experiments (ALICE) at Daresbury Laboratory and as polarised electron source for the proposed International Linear Collider (ILC). Once activated to a Low Electron Affinity (LEA) state and illuminated by a laser, these materials can be used as a high-brightness source of both polarised and un-polarised electrons. This paper presents an effective multi-stage preparation procedure including heat cleaning, atomic hydrogen cleaning and the activation process for a GaAs photocathode. The stability of quantum efficiency (QE) and lifetime of activated to LEA state GaAs photocathode have been studied in the ALICE load-lock photocathode preparation facility which has a base pressure in the order of 10^-11 mbar. These studies are supported by further experimental evidence from surface science techniques such as X-ray Photoelectron Spectroscopy (XPS) to demonstrate the processes at the atomic level.Comment: Presented at First International Particle Accelerator Conference, IPAC'10, Kyoto, Japan, from 23 to 28 May 201

The corrosion behaviour of CoCrFeNi-x (x = Cu, Al, Sn) high entropy alloy systems in chloride solution

The corrosion properties in NaCl solution of four equiatomic HEAs of the CoCrFeNi system adding Al, Cu and Sn are investigated. These alloys are processed by vacuum arc melting and assessed via the Potentiostat method. The properties were compared with two standard stainless steels. The results indicate that CoCrFeNiSn possesses the best passivation in this solution, explained by the alloy phases and presence at the surface of elements in oxidation states corresponding to stable oxide films. The other systems show a range of behaviours attributable to their different microstructures and varying potential for stable oxide formation

Development of the SLRI beam test facility for characterization of monolithic active pixel sensors

Synchrotron Light Research Institute (SLRI) has successfully constructed a new experimental station, a Beam Test Facility (BTF), to the current SLRI accelerator complex. SLRI-BTF is capable of producing electron test beams with the number of electrons ranging from a few to millions of electrons per spill and with tunable energy from 40 MeV up to 1.2 GeV. The required intensity and energy of the test beam are obtained using a combination of a metal target to reduce high-intensity primary beam and a synchrotron booster to accelerate secondary beam to desired energy. The repetition rate of the test beam is up to 0.5 Hz depending on the selected energy and the pulse width is 90 ns. SLRI-BTF targets to service electron test beams with defined intensity and energy for testing and calibration of high-energy particle detectors as well as other beam diagnostic instrumentations. In commissioning, a pixel sensor telescope was employed as a detector to measure the number of electrons and as a preparation to investigate efficiency of mono active pixel sensors. The results confirm production of the low multiplicity of high-energy electrons at SLRI-BTF and the efficiency of a test pixel sensor is successfully calculated

The unforeseen relationship of Fe2O3 and ZnO on fibrous silica KCC-1 catalyst for fabricated Z-scheme extractive-photooxidative desulphurization

Fibrous silica KAUST Catalysis Centre (KCC-1) was prepared via a hydrothermal-microwave method, followed by incorporation of Fe2O3 and ZnO by an electrochemical technique to give ZnO-Fe2O3/KCC-1 (ZFK) catalysts. XRD, FESEM, N2 physisorption, FTIR, XPS, ESR and UV–Vis DRS were employed to characterize the catalysts. A varied amount of Fe2O3 and ZnO seems have insightful impact on the physicochemical behaviours of the KCC-1 while prominently enhanced the extractive-photooxidative desulphurization of dibenzothiophene (DBT). 5Z10FK demonstrated the best performance mainly due to a well distribution of both metal oxides on KCC-1, the highest Si-O-Fe and Si-O-Zn bonds, an appropriate amount of surface defect and suitable band gap energy. Besides, the suitable band positions of 10FK and 5ZK in 5Z10FK composite has allowed the formation of Z-scheme heterojunction for conserved strong redox potential. Kinetic studies revealed that the adsorption of DBT was the rate determining step, thus this reaction obeyed the Langmuir-Hinshelwood pseudo-first order

Superior sulfate radicals-induced visible-light-driven photodegradation of pharmaceuticals by appropriate ce loading on fibrous silica ceria

atterly, sulfate radical (SO4-)-based advanced oxidation processes (SR-AOPs) have earned great attention for wastewaters treatment containing antibiotics with provides SO4- as an active species. In this study, fibrous silica-ceria (FSC) with various Ce loadings (Ce wt%) were successfully synthesized via microemulsion-crystallization. The catalysts' behaviour was evaluated by XRD, FESEM, N2 adsorption/desorption, UV-vis DRS, FTIR, PL and ESR. Results proved that tuning the Ce wt% influenced the crystallinity, particle size, surface defect, oxygen vacancies as well as band gap of FSCs, which altered their properties toward sulfate radical generation in enhancing the photodegradation performances. Photodegradation of ciprofloxacin (CIP) using catalysts in the presence of peroxydisulfate (PDS) are in the following order: FSC-0.1 (92 %) > FSC-0.15 (85 %) > FSC-0.05 (76 %) > commercial CeO2 (37 %) under visible light for 240 min. Radical scavenging and ESR spin-trapping experiment revealed that the induced sulfate radicals (SO4-) and hydroxyl radicals (OH) during reaction had accelerated the performance of CIP degradation. Besides, a detailed energy diagram of CeO2 and FSC-0.1 was proposed based on VB XPS and Tauc plots. This work indicated that the FSC-0.1 coupled with PDS retained its efficiency for five-cycles of reaction without any significant-loss and displayed promising applications for the various pharmaceutical compounds (PCs)