Tunneling scheme for Tel Aviv Metro Line M2 – Preliminary design

2025-05-08

The Metro M2 is a heavy rail metro line designed to significantly enhance public transportation in Tel Aviv alongside two other lines (M1 and M3), thereby improving connectivity and reducing congestion within the city. The project calls for advanced engineering techniques to address the complexities of construction while minimizing disruption in a busy urban environment. The line spans approximately 23 kilometers underground including 21 underground stations. The twin-tube running tunnels will be constructed using 6.5-meter internal diameter Tunnel Boring Machines (TBMs). The underground stations will be excavated using both the Cut & Cover method and conventional tunnelling techniques (mining). Specifically, eight out of the twenty-one stations will be mined, platform caverns will be approximately 20 meters wide and 15 meters high. Additionally, the project includes the construction of nine crossovers, a mined terminus, and a mined security tunnel. The ground conditions present significant challenges, primarily consisting of various types of sand ranging from very loose to weak sandstone, as well as clay and chalk in the eastern section of the alignment. The groundwater table is high, resulting in a substantial portion of the stations and running tunnels being situated below it. The project’s complexity requires significant international expertise and cutting-edge engineering solutions, particularly addressing with the challenging ground conditions in the wide range of works involved in this project. Several aspects of this project, such as the mined stations, will be carried out for the first time in Tel Aviv metropolitan area. Given the scale of this project, a large and skilled workforce will be required in the coming years.

Mitigation of the Brighter-fatter Effect in the LSST Camera

Publications of the Astronomical Society of the Pacific · 2024-04-01 · 6 citations

Abstract Thick, fully depleted charge-coupled devices are known to exhibit nonlinear behavior at high signal levels due to the dynamic behavior of charges collecting in the potential wells of pixels, called the brighter-fatter effect (BFE). The effect results in distorted images of bright calibration stars, creating a flux-dependent point-spread function that if left unmitigated, could make up a large fraction of the error budget in Stage IV weak-lensing (WL) surveys such as the Legacy Survey of Space and Time (LSST). In this paper, we analyze image measurements of flat fields and artificial stars taken at different illumination levels with the LSST Camera (LSSTCam) at SLAC National Accelerator Laboratory in order to quantify this effect in the LSSTCam before and after a previously introduced correction technique. We observe that the BFE evolves anisotropically as a function of flux due to higher-order BFEs, which violates the fundamental assumption of this correction method. We then introduce a new method based on a physically motivated model to account for these higher-order terms in the correction, and then we test the modified correction on both data sets. We find that the new method corrects the effect in flat fields better than it corrects the effect in artificial stars, which we suggest is the result of sub-pixel physics not included in this correction model. We use these results to define a new metric for the full-well capacity of our sensors and advise image processing strategies to further limit the impact of the effect on LSST WL science pathways.

Deep learning models of the discrete component of the Galactic interstellar <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>γ</mml:mi></mml:math>-ray emission

Physical review. D/Physical review. D. · 2023-03-17 · 3 citations

A significant pointlike component from the small-scale (or discrete) structure in the ${\mathrm{H}}_{2}$ interstellar gas might be present in the Fermi-LAT data, but modeling this emission relies on observations of rare gas tracers only available in limited regions of the sky. Identifying this contribution is important to discriminate $\ensuremath{\gamma}$-ray point sources from interstellar gas, and to better characterize extended $\ensuremath{\gamma}$-ray sources. We design and train convolutional neural networks to predict this emission where observations of these rare tracers do not exist, and discuss the impact of this component on the analysis of the Fermi-LAT data. In particular, we evaluate prospects to exploit this methodology in the characterization of the Fermi-LAT Galactic center excess through accurate modeling of pointlike structures in the data to help distinguish between a pointlike or smooth nature for the excess. We show that deep learning may be effectively employed to model the $\ensuremath{\gamma}$-ray emission traced by these rare ${\mathrm{H}}_{2}$ proxies within statistical significance in data-rich regions, supporting prospects to employ these methods in yet unobserved regions.

Mitigation of the Brighter-Fatter Effect in the LSST Camera

2023-12-07

Thick, fully depleted charge-coupled devices (CCDs) are known to exhibit non-linear behavior at high signal levels due to the dynamic behavior of charges collecting in the potential wells of pixels, called the brighter-fatter effect (BFE). This particularly impacts bright calibration stars, which appear larger than their intrinsic shape, creating a flux-dependent point-spread function (PSF) that if left unmitigated, could make up a large fraction of the error budget in Stage IV weak-lensing (WL) surveys such as the Legacy Survey of Space and Time (LSST). In this paper, we analyze image measurements of flat fields and artificial stars taken at different illumination levels with the LSST Camera (LSSTCam) at SLAC National Accelerator Laboratory in order to quantify this effect in the LSST Camera before and after a previously introduced correction technique. We observe that the BFE evolves anisotropically as a function of flux due to higher-order BFEs, which violates the fundamental assumption of this correction method. We then introduce a new sampling method based on a physically motivated model to account these higher-order terms in the correction, and then we test the modified correction on both datasets. We find that the new method corrects the effect in flat fields better than it corrects the effect in artificial stars which we conclude is the result of a unmodeled curl component of the deflection field by the correction. We use these results to define a new metric for the full-well capacity of our sensors and advise image processing strategies to further limit the impact of the effect on LSST WL science pathways.

Mitigation of the Brighter-Fatter Effect in the LSST Camera

arXiv (Cornell University) · 2023-12-05 · 2 citations

Thick, fully depleted charge-coupled devices (CCDs) are known to exhibit non-linear behavior at high signal levels due to the dynamic behavior of charges collecting in the potential wells of pixels, called the brighter-fatter effect (BFE). This particularly impacts bright calibration stars, which appear larger than their intrinsic shape, creating a flux-dependent point-spread function (PSF) that if left unmitigated, could make up a large fraction of the error budget in Stage IV weak-lensing (WL) surveys such as the Legacy Survey of Space and Time (LSST). In this paper, we analyze image measurements of flat fields and artificial stars taken at different illumination levels with the LSST Camera (LSSTCam) at SLAC National Accelerator Laboratory in order to quantify this effect in the LSST Camera before and after a previously introduced correction technique. We observe that the BFE evolves anisotropically as a function of flux due to higher-order BFEs, which violates the fundamental assumption of this correction method. We then introduce a new sampling method based on a physically motivated model to account these higher-order terms in the correction, and then we test the modified correction on both datasets. We find that the new method corrects the effect in flat fields better than it corrects the effect in artificial stars which we conclude is the result of a unmodeled curl component of the deflection field by the correction. We use these results to define a new metric for the full-well capacity of our sensors and advise image processing strategies to further limit the impact of the effect on LSST WL science pathways.

Improved modeling of the discrete component of the Galactic interstellar <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>γ</mml:mi></mml:mrow></mml:math>-ray emission and implications for the <i>Fermi</i>–LAT Galactic Center excess

Physical review. D/Physical review. D. · 2023-06-29 · 1 citations

The aim of this work is to improve models for the $\ensuremath{\gamma}$-ray discrete or small-scale structure related to ${\mathrm{H}}_{2}$ interstellar gas. Reliably identifying this contribution is important to disentangle $\ensuremath{\gamma}$-ray point sources from interstellar gas, and to better characterize extended $\ensuremath{\gamma}$-ray signals. Notably, the Fermi--LAT Galactic center (GC) excess, whose origin remains unclear, might be smooth or pointlike. If the data contain a pointlike contribution that is not adequately modeled, a smooth GC excess might be erroneously deemed to be pointlike. We improve models for the ${\mathrm{H}}_{2}$-related $\ensuremath{\gamma}$-ray discrete emission for a $50\ifmmode^\circ\else\textdegree\fi{}\ifmmode\times\else\texttimes\fi{}1\ifmmode^\circ\else\textdegree\fi{}$ region along the Galactic plane via ${\mathrm{H}}_{2}$ proxies better suited to trace these features. We find that these are likely to contribute significantly to the $\ensuremath{\gamma}$-ray Fermi--LAT data in this region, and the brightest ones are likely associated with detected Fermi--LAT sources, a compelling validation of this methodology. We discuss prospects to extend this methodology to other regions of the sky and implications for the characterization of the GC excess.

Improved Modeling of the Discrete Component of the Galactic Interstellar Gamma-ray Emission and Implications for the Fermi-LAT Galactic Center Excess

arXiv (Cornell University) · 2022-06-06

The aim of this work is to improve models for the gamma-ray discrete or small-scale structure related to H2 interstellar gas. Reliably identifying this contribution is important to disentangle gamma-ray point sources from interstellar gas, and to better characterize extended gamma-ray signals. Notably, the Fermi-LAT Galactic center (GC) excess, whose origin remains unclear, might be smooth or point-like. If the data contain a point-like contribution that is not adequately modeled, a smooth GC excess might be erroneously deemed to be point-like. We improve models for the H2-related gamma-ray discrete emission for a $50^\circ \times 1^\circ$ region along the Galactic plane via H2 proxies better suited to trace these features. We find that these are likely to contribute significantly to the gamma-ray Fermi-LAT data in this region, and the brightest ones are likely associated with detected Fermi-LAT sources, a compelling validation of this methodology. We discuss prospects to extend this methodology to other regions of the sky and implications for the characterization of the GC excess.

Deep Learning Models of the Discrete Component of the Galactic Interstellar Gamma-Ray Emission

arXiv (Cornell University) · 2022-06-06

A significant point-like component from the small scale (or discrete) structure in the H2 interstellar gas might be present in the Fermi-LAT data, but modeling this emission relies on observations of rare gas tracers only available in limited regions of the sky. Identifying this contribution is important to discriminate gamma-ray point sources from interstellar gas, and to better characterize extended gamma-ray sources. We design and train convolutional neural networks to predict this emission where observations of these rare tracers do not exist and discuss the impact of this component on the analysis of the Fermi-LAT data. In particular, we evaluate prospects to exploit this methodology in the characterization of the Fermi-LAT Galactic center excess through accurate modeling of point-like structures in the data to help distinguish between a point-like or smooth nature for the excess. We show that deep learning may be effectively employed to model the gamma-ray emission traced by these rare H2 proxies within statistical significance in data-rich regions, supporting prospects to employ these methods in yet unobserved regions.

Dark matter interpretation of the <i>Fermi</i>-LAT observations toward the outer halo of M31

Physical review. D/Physical review. D. · 2021-01-29 · 37 citations

An excess $\ensuremath{\gamma}$-ray signal toward the outer halo of M31 has recently been reported. Although other explanations are plausible, the possibility that it arises from dark matter (DM) is valid. In this work we interpret the excess in the framework of DM annihilation, using as our representative case WIMP DM annihilating to bottom quarks, and we perform a detailed study of the systematic uncertainty in the $J$-factor for the M31 field. We find that the signal favors a DM particle with a mass of $\ensuremath{\sim}45--72\text{ }\text{ }\mathrm{GeV}$. While the mass is well constrained, the systematic uncertainty in the cross section spans 3 orders of magnitude, ranging from $\ensuremath{\sim}5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}27}--5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}24}\text{ }\text{ }{\mathrm{cm}}^{3}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$. This high uncertainty is due to two main factors, namely, an uncertainty in the substructure nature and geometry of the DM halos for both M31 and the Milky Way (MW), and correspondingly, an uncertainty in the contribution to the signal from the MW's DM halo along the line of sight. However, under the conditions that the minimum subhalo mass is $\ensuremath{\lesssim}{10}^{\ensuremath{-}6}\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$ and the actual contribution from the MW's DM halo along the line of sight is at least $\ensuremath{\sim}30%$ of its total value, we show that there is a large overlap with the DM interpretations of both the Galactic center (GC) excess and the antiproton excess, while also being compatible with the limits for the MW dwarf spheroidals. More generally, we summarize the results from numerous complementary DM searches in the energy range 10 GeV--300 GeV corresponding to the GC excess and identify a region in parameter space that still remains viable for discovery of the DM particle.

The <i>Fermi</i>–LAT Galactic Center Excess: Evidence of Annihilating Dark Matter?

Annual Review of Nuclear and Particle Science · 2020-10-19 · 57 citations

The center of the Galaxy is one of the prime targets in the search for a signal of annihilating (or decaying) dark matter. If such a signal were to be detected, it would shed light on one of the biggest mysteries in physics today: What is dark matter? Fundamental properties of the particle nature of dark matter, such as its mass, annihilation cross section, and annihilation final states, could be measured for the first time. Several experiments have searched for such a signal, and some have measured excesses that are compatible with it. A long-standing and compelling excess is observed in γ-rays by the Fermi Large Area Telescope ( Fermi–LAT). This excess is consistent with a dark matter particle with a mass of approximately 50 (up to ∼200) GeV annihilating with a velocity-averaged cross section of ∼10 −26 cm 3 s −1 . Although a dark matter origin of the excess remains viable, other interpretations are possible. In particular, there is some evidence that the excess is produced by a population of unresolved point sources of γ-rays—for example, millisecond pulsars. In this article, I review the current status of the observation of the Fermi–LAT Galactic center excess, the possible interpretations of the excess, the evidence and counterevidence for each, and the prospects for resolving its origin with future measurements.