AFTER, the front end ASIC of the T2K Time Projection Chambers

The T2K (Tokai-to-Kamioka) experiment is a long baseline neutrino oscillation experiment in Japan. A near detector, located at 280m of the production target, is used to characterize the beam. One of its key elements is a tracker, made of three Time Projection Chambers (TPC) read by Micromegas endplates. A new readout system has been developed to collect, amplify, condition and acquire the data produced by the 124,000 detector channels of these detectors. The front-end element of this system is a a new 72-channel application specific integrated circuit. Each channel includes a low noise charge preamplifier, a pole zero compensation stage, a second order Sallen-Key low pass filter and a 511-cell Switched Capacitor Array. This electronics offers a large flexibility in sampling frequency, shaping time, gain, while taking advantage of the low physics events rate of 0.3 Hz. We detail the design and the performance of this ASIC and report on the deployment of the frond-end electronics on-site

Bulk micromegas detectors for large TPC applications

A large volume TPC will be used in the near future in a variety of experiments including T2K. The bulk Micromegas detector for this TPC is built using a novel production technique particularly suited for compact and robust low mass detectors. The capability to pave a large surface with a simple mounting solution and small dead space between modules is of particular interest for these applications. We have built several large bulk Micromegas detectors (27 x 26 cm2) and we have tested them in the former HARP field cage setup with a magnetic field. Cosmic ray data have been acquired in a variety of experimental conditions. Good detector performances and space point resolution have been achieved

Time projection chambers for the T2K near detectors

The T2K experiment is designed to study neutrino oscillation properties by directing a high intensity neutrino beam produced at J-PARC in Tokai, Japan, towards the large Super-Kamiokande detector located 295 km away, in Kamioka, Japan. The experiment includes a sophisticated near detector complex, 280 m downstream of the neutrino production target in order to measure the properties of the neutrino beam and to better understand neutrino interactions at the energy scale below a few GeV. A key element of the near detectors is the ND280 tracker, consisting of two active scintillator-bar target systems surrounded by three large time projection chambers (TPCs) for charged particle tracking. The data collected with the tracker is used to study charged current neutrino interaction rates and kinematics prior to oscillation, in order to reduce uncertainties in the oscillation measurements by the far detector. The tracker is surrounded by the former UA1/Nomad dipole magnet and the TPCs measure the charges, momenta, and particle types of charged particles passing through them. Novel features of the TPC design include its rectangular box layout constructed from composite panels, the use of bulk micromegas detectors for gas amplification, electronics readout based on a new ASIC, and a photoelectron calibration system. This paper describes the design and construction of the TPCs, the micromegas modules, the readout electronics, the gas handling system, and shows the performance of the TPCs as deduced from measurements with particle beams, cosmic rays, and the calibration system

Evidence of a positive effect of hydrolysis rate of fish peptones on Escherichia coli culture kinetics.

International audienceThe aim of this work was to evaluate the potential use of a fish hydrolysate as microbial substrate, and the effect of an increased (acidic) hydrolysis rate on the cell yield. With this objective, we compared E. coli growth kinetics on fish hydrolysates and on casein hydrolysates as a reference. We measured lag-phase durations, growth rates in exponential phase, and maximum cell densities. On casein hydrolysates, the lag phase was shorter, and the growth rate and maximum cell density were higher as compared to that on fish protein hydrolysates. For both substrates, when the concentration in the medium was increased five times, the maximum cell density was also increased approximately five times, showing that the quality, or the concentration, of these nitrogen sources were the limiting factors in our conditions. Following hot hydrochloric acid hydrolysis of both enzymatic hydrolysates, both substrates showed an approximately 170% increase of the maximum cell density compared to the untreated ones. These results suggest that the rate of hydrolysis of proteins dramatically affects the final cell density in cultures. Therefore, at least for our E. coli strain, the quality of the protein hydrolysate seems to be highly related to the hydrolysis rate

Enzymatic hydrolysis of proteins from yellowfin tuna (Thunnus albacares) wastes using Alcalase

International audienceEnzymatic hydrolysis of tuna stomach proteins by Alcalase was investigated in a batch reactor. The influence of the process variables (enzyme/substrate ratio; effect of intermediate substrate and enzyme addition) was studied with regards to the extent of proteolytic degradation and to the molecular weight distribution of the peptides. A linear correlation was found between the degree of hydrolysis (DH) and the enzyme concentration. After addition of extra substrate during the course of hydrolysis, the final DH obtained was proportional to the substrate added, suggesting that the concentration of hydrolysable bonds was one of the main factors controlling the hydrolysis rate. Preliminary results showed that tuna protein hydrolysates performed effectively as nitrogenous source in microbial growth media

Utilisation de souches non pathogenes de Fusarium pour lutter contre les fusarioses: situation actuelle dans la pratique

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Low-noise HEMTs for Coherent Elastic Neutrino Scattering and Low-Mass Dark Matter Cryogenic Semiconductor Detectors

International audienceWe present the noise performance of high electron mobility transistors (HEMT) developed by CNRS/C2N laboratory. Various HEMT’s gate geometries with 2 pF to 230 pF input capacitance have been studied at 4  K. A model for both voltage and current noises has been developed with frequency dependence up to 1  MHz. These HEMTs exhibit low dissipation, excellent noise performance and can advantageously replace traditional Si-JFETs for the readout of high impedance thermal sensor and semiconductor ionization cryogenic detectors. Our model predicts that cryogenic germanium detectors of 30  g with 10  eV heat and 20  eV$_\mathrm{ee}$ baseline resolution are feasible if read out by HEMT-based amplifiers. Such resolution allows for high discrimination between nuclear and electron recoils at low threshold. This capability is of major interest for coherent elastic neutrino scattering and low-mass dark matter experiments such as Ricochet and EDELWEISS