All-fiber optical parametric oscillator pumped by an all-fiber Yb-based MOPA

We report on an all-fiber PCF-based optical parametric oscillator, synchronously pumped by an all-fiber Yb-doped MOPA. A pump-to-anti-Stokes conversion efficiency of 8.6% is reached at a frequency-shift of 142 THz

The X-HPD: Conceptual Study of a Large Spherical Hybrid Photodetector

We present the results of a conceptual study demonstrating the feasibility of a large spherical hybrid photodetector with central anode. A prototype tube with 208 mm diameter and an anode in form of a metallic cube has been fabricated. In the final version of the so-called X-HPD concept the anode will be a scintillator cube with plated faces and a small photodetector to read out the bottom. The bialkali photocathode covers three quarters of the sphere surface. Combined use of this cathode in transmissive and reflective mode leads to effective quantum efficiency values exceeding those obtained in conventional hemispherical PMT designs. Further features of the concept are a photoelectron collection efficiency approaching 100% and a photon amplification in the scintillator crystal leading to a distinct single photoelectron signal. Using a custom built electron accelerator based on a CsI transmissive photocathode, LSO and YAP block crystals in geometries adapted to the anode of an X-HPD have been tested with single photoelectrons in the 10-30 keV energy range. The scintillation light was read out with a conventional PMT or a Si-PM. More than 30 photoelectrons per incident electron could be detected with the PMT

The X-HPD: Development of a large spherical hybrid photodetector

The X-HPD concept is a modern implementation of the Dumand and Lake Baikal approach to large area photon detectors, primarily aimed at water based Cherenkov detectors. Our prototype detector consists of an almost spherical vacuum tube of 8-inch diameter with a semi-transparent bialkali photocathode and a LYSO scintillation crystal mounted in the centre of the tube. The scintillation light produced after the impact of a photoelectron which was accelerated to about 20-30 keV energy is detected by a small standard PMT. In addition to the attractive characteristics already established with its historic predecessors, namely high gain, large collection efficiency and immunity to the earth magnetic field, the X-HPD concept leads to very high effective Q.E. values, an extended viewing angle and marginal transit time spread.We present recent results obtained with a prototype tube built at CERN and a second full tube under preparation in collaboration with the company Photonis

Filtration of a bacterial fermentation broth: harvest conditions effects on cake hydraulic resistance

Abstract The hydraulic resistance of cakes formed during the ultrafiltration of Streptomyces pristinaespiralis broths has been investigated for different harvesting conditions. S. pristinaespiralis broth was harvested after the point of microorganism activity declines (0-h aged broth) and afterwards held for different durations of up to 16 h (16 aged broths). Aging behavior occurring between the end of microorganism activity and harvest was compared for different acidification procedures (pH) and the mechanisms for which the hydraulic resistance of the cake is affected by aging have been investigated. For broths harvested under conditions where the acidification is fixed at pH 2 or 3, hydraulic resistance associated with cake build-up is directly determined by the interactions between the cells. Holding broths beyond 5 h contributes to a release of a soluble component from the cell surface. Enhanced cell surface interactions then turn the cake structure into a more open one and reduce the specific hydraulic resistance. For broths harvested under conditions where the acidification is fixed at pH 4, hydraulic resistance associated with cake build-up is both determined by cell interactions and cell morphology. The cause of the increase in specific hydraulic resistance with aging is due to the binding of a soluble component released by the microorganisms, which decreases the cell surface interactions. Keywords Ultrafiltration, Cake hydraulic resistance, Biotechnology, Harvest tim

Three-dimensional writing inside silicon using a 2-µm picosecond fiber laser

International audienc

The X-HPD -Conceptual Study of a Large Spherical Hybrid Photodetector

Abstract We present the results of a conceptual study demonstrating the feasibility of a large spherical hybrid photodetector with central anode. A prototype tube with 208 mm diameter and an anode in form of a metallic cube has been fabricated. In the final version of the so-called X-HPD concept the anode will be a scintillator cube with plated faces and a small photodetector to read out the bottom. The bialkali photocathode covers three quarters of the sphere surface. Combined use of this cathode in transmissive and reflective mode leads to effective quantum efficiency values exceeding those obtained in conventional hemispherical PMT designs. Further features of the concept are a photoelectron collection efficiency approaching 100% and a photon amplification in the scintillator crystal leading to a distinct single photoelectron signal. Using a custom built electron accelerator based on a CsI transmissive photocathode, LSO and YAP block crystals in geometries adapted to the anode of an X-HPD have been tested with single photoelectrons in the 10-30 keV energy range. The scintillation light was read out with a conventional PMT or a Si-PM. More than 30 photoelectrons per incident electron could be detected with the PMT

Tunable red-light source by frequency mixing from dual band Er/Yb co-doped fiber laser

International audienceWe report an all solid state laser device producing tunable dual wavelength emission in the near IR region (1060nm, and 1550 nm) by use of an Er/Yb co-doped fiber. Generation of continuous-wave radiation around 630 nm is then demonstrated by extra-cavity sum frequency mixing in a Periodically Poled Lithium Niobate (PPLN) crystal. Quasi phase matching conditions are obtained over 7 nm to generate tunable coherent light in the red spectral range

Impact of radon and thoron levels on technosphere objects in the total urban environment

Thoron and radon exhalation from earth's crust is the most important source of atmospheric radioactive gases, along with its daughter products present in the soil is one of the major contributors to the external gamma dose in the atmosphere, since its distribution in the earth's crust is important for controlling the production of 220Rn and 222Rn. In this study trace amount of 232Th, 238U permeate almost all soils and rocks, in part due to the influence of buildings from which radioactive gas can emanate over geological time scales. Results obtained from this study indicate that the region has background radioactivity levels within the natural limits and a detailed discussion of the results is presented in the work