Cosmic Results Research Articles

Cosmic results with the final Micromegas sectors for the ATLAS Muon upgrade

With the upgraded beam luminosity in LHC Run 3, the detector technology for the innermost end-cap muon station (small wheel) of the ATLAS detector needs to be upgraded. The new technology should be able to meet the demands of spatial resolution, high efficiency as well as fast response of the present system at the expected higher background rate, up to 20 kHz/cm2. The detectors which perform precision tracking and triggering in the New Small Wheel (NSW) are Micromegas (MM) and small-strip Thin Gas Chamber (sTGC) respectively. The detectors are also complementary to each other. The Micromegas quadruplets are delivered to CERN from the different construction sites. Two Micromegas quadruplets are integrated to build a double wedge. After the electronic integration, the double wedges are tested with cosmic muons at the cosmic stand at CERN. The final high voltage configuration is verified and various parameters like the efficiency, cluster size, strip multiplicity per readout layer are measured. The double wedge of the Micromegas sector is qualified for the final integration with the sTGC wedges before mounting on the NSW. The procedure and the cosmic test results of the final validation of Micromegas double wedges is presented.

Extraction of electron density profiles with geostationary satellite-based GPS side lobe occultation signals

GPS radio occultation (RO) measurements recorded on the geostationary earth orbit (GEO) satellite TJS-2 have been investigated for electron density profile (EDP) retrieval. The total electron content derived from TJS-2 single-frequency excess phase is refined by a moving average filter to smooth high-frequency errors, which outperforms the single-difference technique. The side lobe GPS RO signals have been used to estimate electron densities up to several thousand kilometers in height for the first time. By comparison with the ground-based digisonde, the IRI 2016 model and the Constellation Observing System for Meteorology, Ionosphere, and Climate satellite (COSMIC) EDPs, the TJS-2 ionospheric EDPs show good agreement with correlation coefficients exceeding 0.8. The TJS-2 average NmF2 differences compared to digisondes and COSMIC results are 12.9% and 1.4%, respectively, while the hmF2 differences are 1.65 km and 1.76 km, respectively. Our results reveal that GEO-based RO signals can estimate EDPs to altitudes up to several thousand kilometers at specific locations with daily repeatability, which makes it a very suitable technique for routinely monitoring EDP variations.

COSMIC GPS Observations of Northern Hemisphere winter stratospheric gravity waves and comparisons with an atmospheric general circulation model

COSMIC satellite temperature data are used to derive the 2006/07 winter mean stratospheric Northern Hemisphere potential energy Ep from gravity waves with vertical wavelengths less than 7 km in grid cells of size 10° × 5°; and to study longitudinal and latitudinal variability in cells of size 20° × 5° × 7 days. Large Ep at 17–23 km is mostly associated with the sub‐tropical jet and shows significant longitudinal variability. Some contribution to total Ep from local orographic sources may occur above the Canadian Rockies, Scandinavia and northern Japan, but not above the Himalayas, due to the background wind conditions. Many of the waves are likely to have low ground‐based phase speeds, as observed by filtering around the 0–10 m s−1 background zonal wind. COSMIC results are compared with a T106L60 AGCM, confirming sub‐tropical jet related generation, upward propagation and low phase speeds of the observed gravity waves.