Fast Luminosity Monitoring using Diamond Sensors for the Super Flavor Factory SuperKEKB

ISBN 978-3-95450-132-8 - http://accelconf.web.cern.ch/AccelConf/IPAC2014/papers/thpme090.pdfInternational audienceSuper luminous flavor factories, as SuperKEKB in Japan, aim to achieve very high luminosity thanks to a newly employed concept, the nano-beam scheme, where ultra-low emittance beams collide at very large crossing angle. Luminosity optimisation and dynamic imperfections require fast luminosity measurements. The aimed precision, 10−3 in 10 ms, can be achieved thanks to the very large cross-section of the radiative Bhabha process at zero-photon scattering angle. As a result of huge particle fluxes, diamond sensors are chosen to be placed just outside the beam-pipe, downstream of the interaction point, at locations with event rates consistent with the aimed precision and small enough contamination by backgrounds from single-beam particle losses. We will present the results concerning the investigation of the optimal positioning of our diamond sensors, taking into account the rate of Bhabha particles as well as their interactions with the beam pipe material

Diagnosis of focal liver lesions from ultrasound using deep learning

PURPOSE: The purpose of this study was to create an algorithm that simultaneously detects and characterizes (benign vs. malignant) focal liver lesion (FLL) using deep learning. MATERIALS AND METHODS: We trained our algorithm on a dataset proposed during a data challenge organized at the 2018 Journées Francophones de Radiologie. The dataset was composed of 367 two-dimensional ultrasound images from 367 individual livers, captured at various institutions. The algorithm was guided using an attention mechanism with annotations made by a radiologist. The algorithm was then tested on a new data set from 177 patients. RESULTS: The models reached mean ROC-AUC scores of 0.935 for FLL detection and 0.916 for FLL characterization over three shuffled three-fold cross-validations performed with the training data. On the new dataset of 177 patients, our models reached a weighted mean ROC-AUC scores of 0.891 for seven different tasks. CONCLUSION: This study that uses a supervised-attention mechanism focused on FLL detection and characterization from liver ultrasound images. This method could prove to be highly relevant for medical imaging once validated on a larger independent cohort

Non-planar four-mirror optical cavity for high intensity gamma ray flux production by pulsed laser beam Compton scattering off GeV-electrons

As part of the R&D toward the production of high flux of polarised Gamma-rays we have designed and built a non-planar four-mirror optical cavity with a high finesse and operated it at a particle accelerator. We report on the main challenges of such cavity, such as the design of a suitable laser based on fiber technology, the mechanical difficulties of having a high tunability and a high mechanical stability in an accelerator environment and the active stabilization of such cavity by implementing a double feedback loop in a FPGA

Production of gamma rays by pulsed laser beam Compton scattering off GeV-electrons using a non-planar four-mirror optical cavity

As part of the positron source R&D for future $e^+-e^-$ colliders and Compton based compact light sources, a high finesse non-planar four-mirror Fabry-Perot cavity has recently been installed at the ATF (KEK, Tsukuba, Japan). The first measurements of the gamma ray flux produced with a such cavity using a pulsed laser is presented here. We demonstrate the production of a flux of 2.7 $\pm$ 0.2 gamma rays per bunch crossing ($\sim3\times10^6$ gammas per second) during the commissioning

Characteristics and mass distribution of extraterrestrial dust from the Greenland Ice Cap

International audienceExtraterrestrial grains with sizes ≳50 µm can now be extracted in large numbers from terrestrial sediments but their origins are still uncertain. At least 99% of these grains have been thought to be spherules1,2 resulting from the melting of their parent bodies in the atmosphere, which destroyed their mineralogical composition. Here we present analyses of extraterrestrial grains extracted from six samples of cryoconite3 (black dust) collected from the melt zone of the Greenland ice cap. In addition to families of grains never reported before, we have found a surprisingly high abundance of unmelted chondritic fragments, in which the nonvolatile component of the parent bodies has been well preserved. The mass distribution of the grains is very similar to that of the micrometeorite flux at 1 AU (ref. 4), indicating that most of the grains are micrometeorites, and not ablation products of larger meteorites. These results yield new constraints on the ablation of such Greenland micrometeorites, as well as guidelines for using them as glaciological and geological markers