arXiv subjects

B. Schmitt

Publications and source records attributed to B. Schmitt.

At least 37 records · Page 2Linked to original sources

arXiv2025

Progress in the Development of Multi-Element Monolithic Germanium Detectors in LEAPS-INNOV Project: Insights from Detector Performance Simulation

This study presents a detailed simulation-based analysis of the detection limits of multi-element monolithic Germanium (Ge) detectors to cadmium traces in environmental soil samples. Using the capabilities of the Geant4 Monte Carlo toolkit in combination with the Solid State Detector Package, we evaluated the detection limit variation with the sample-to-detector distances and photon flux. These simulations were conducted to mimic realistic conditions, with a photon flux measured by the SAMBA beamline at the SOLEIL synchrotron facility. Our findings for the detection limit for trace amounts of pollutants in low concentrations like cadmium in the soil provide valuable insights for optimizing experimental setups in environmental monitoring and synchrotron-based applications, where precise detection of trace elements is critical.

physics.ins-det↗

arXiv2025

BICEP/Keck XVIII: Measurement of BICEP3 polarization angles and consequences for constraining cosmic birefringence and inflation

We use a custom-made calibrator to measure individual detectors' polarization angles of BICEP3, a small aperture telescope observing the cosmic microwave background (CMB) at 95GHz from the South Pole. We describe our calibration strategy and the statistical and systematic uncertainties associated with the measurement. We reach an unprecedented precision for such measurement on a CMB experiment, with a repeatability for each detector pair of $0.02°$. We show that the relative angles measured using this method are in excellent agreement with those extracted from CMB data. Because the absolute measurement is currently limited by a systematic uncertainty, we do not derive cosmic birefringence constraints from BICEP3 data in this work. Rather, we forecast the sensitivity of BICEP3 sky maps for such analysis. We investigate the relative contributions of instrument noise, lensing, and dust, as well as astrophysical and instrumental systematics. We also explore the constraining power of different angle estimators, depending on analysis choices. We establish that the BICEP3 2-year dataset (2017--2018) has an on-sky sensitivity to the cosmic birefringence angle of $σ= 0.078°$, which could be improved to $σ= 0.055°$ by adding all of the existing BICEP3 data (through 2023). Furthermore, we emphasize the possibility of using the BICEP3 sky patch as a polarization calibration source for CMB experiments, which with the present data could reach a precision of $0.035°$. Finally, in the context of inflation searches, we investigate the impact of detector-to-detector variations in polarization angles as they may bias the tensor-to-scalar ratio r. We show that while the effect is expected to remain subdominant to other sources of systematic uncertainty, it can be reliably calibrated using polarization angle measurements such as the ones we present in this paper.

astro-ph.CO↗

arXiv2024

Optimizing Charge Transport Simulation for Hybrid Pixel Detectors

To enhance the spatial resolution of the MÖNCH 25 \textmu m pitch hybrid pixel detector, deep learning models have been trained using both simulation and measurement data. Challenges arise when comparing simulation-based deep learning models to measurement-based models for electrons, as the spatial resolution achieved through simulations is notably inferior to that from measurements. Discrepancies are also observed when directly comparing X-ray simulations with measurements, particularly in the spectral output of single pixels. These observations collectively suggest that current simulations require optimization. To address this, the dynamics of charge carriers within the silicon sensor have been studied using Monte Carlo simulations, aiming to refine the charge transport modeling. The simulation encompasses the initial generation of the charge cloud, charge cloud drift, charge diffusion and repulsion, and electronic noise. The simulation results were validated with measurements from the MÖNCH detector for X-rays, and the agreement between measurements and simulations was significantly improved by accounting for the charge repulsion.

physics.ins-det↗

arXiv2023

Composition and thermal properties of Ganymede's surface from JWST/NIRSpec and MIRI observations

JWST NIRSpec IFU (2.9-5.3 mu) and MIRI MRS (4.9-28.5 mu) observations were performed on both the leading and trailing hemispheres of Ganymede with a spectral resolution of ~2700. Reflectance spectra show signatures of water ice, CO2 and H2O2. An absorption feature at 5.9 mu is revealed and is tentatively assigned to sulfuric acid hydrates. The CO2 4.26-mu band shows latitudinal and longitudinal variations in depth, shape and position over the two hemispheres, unveiling different CO2 physical states. In the ice-rich polar regions, which are the most exposed to Jupiter's plasma irradiation, the CO2 band is redshifted with respect to other terrains. In the leading northern polar cap, the CO2 band is dominated by a high wavelength component at ~4.27 mu, consistent with CO2 trapped in amorphous water ice. At equatorial latitudes (and especially on dark terrains) the observed band is broader and shifted towards the blue, suggesting CO2 adsorbed on non-icy materials. Amorphous ice is detected in the ice-rich polar regions, and is especially abundant on the leading northern polar cap. In both hemispheres the north polar cap ice appears to be more processed than the south polar cap. A longitudinal modification of the H2O ice molecular structure and/or nano/micrometre-scale texture, of diurnal or geographic origin, is observed in both hemispheres. Ice frost is observed on the morning limb of the trailing hemisphere, possibly formed during the night from the recondensation of water subliming from the warmer subsurface. Reflectance spectra of the dark terrains are compatible with the presence of Na-/Mg-sulfate salts, sulfuric acid hydrates, and possibly phyllosilicates mixed with fine-grained opaque minerals, having an highly porous texture. Mid-IR brightness temperatures indicate a rough surface and a very low thermal inertia of 20-40 J m-2 s-0.5 K-1, consistent with a porous surface.

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arXiv2022

Detection of MeV electrons using a charge integrating hybrid pixel detector

Electrons are emerging as a strong complement to X-rays for diffraction based studies. In this paper we investigate the performance of a JUNGFRAU detector with 320 um thick silicon sensor at a pulsed electron source. Originally developed for X-ray detection at free electron lasers, JUNGFRAU features a dynamic range of 120 MeV/pixel (implemented with in-pixel gain switching) which translated to about 1200 incident electrons per pixel and frame in the MeV region. We preset basic characteristics such as energy deposited per incident particle, resulting cluster size and spatial resolution along with dynamic (intensity) range scans. Measurements were performed at 4, 10 and 20 MeV/c. We compare the measurements with GEANT4 based simulations and extrapolate the results to different sensor thicknesses using these simulations.

physics.ins-det↗

arXiv2022

A Predicted Dearth of Majority Hypervolatile Ices in Oort Cloud Comets

We present new, ice species-specific New Horizons/Alice upper gas coma production limits from the 01 Jan 2019 MU69/Arrokoth flyby of Gladstone et al. (2021) and use them to make predictions about the rarity of majority hypervolatile (CO, N$_2$, CH$_4$) ices in KBOs and Oort Cloud comets. These predictions have a number of important implications for the study of the Oort Cloud, including: determination of hypervolatile rich comets as the first objects emplaced into the Oort Cloud; measurement of CO/N$_2$/CH$_4$ abundance ratios in the proto-planetary disk from hypervolatile rich comets; and population statistical constraints on early (< 20 Myr) planetary aggregation driven versus later (> 50 Myr) planetary migration driven emplacement of objects into the Oort Cloud. They imply that the phenomenon of ultra-distant active comets like C/2017K2 (Jewitt et al. 2017, Hui et al. 2018) should be rare, and thus not a general characteristic of all comets. They also suggest that interstellar object 2I/Borisov did not originate in a planetary system that was inordinately CO rich (Bodewits et al. 2020), but rather could have been ejected onto an interstellar trajectory very early in its natal system's history.

astro-ph.EP↗

arXiv2021

Volatile transport modeling on Triton with new observational constraints

Neptune's moon Triton shares many similarities with Pluto, including volatile cycles of N2, CH4 and CO, and represents a benchmark case for the study of surface-atmosphere interactions on volatile-rich KBOs. Within the context of New Horizons observations of Pluto as well as recent Earth-based observations of Triton, we adapt a Plutonian VTM to Triton, and test its ability to simulate its volatile cycles, thereby aiding our understanding of its climate. We present VTM simulations exploring the volatile cycles on Triton over long-term and seasonal timescales for varying model parameters. We explore what scenarios and model parameters allow for a best match of the available observations. In particular, our set of observational constraints include Voyager 2 observations, ground-based NIR (0.8 to 2.4 μm) disk-integrated spectra and the evolution of surface pressure as retrieved from stellar occultations. Our results show that Triton's poles act as cold traps for volatile ices and favor the formation of polar caps extending to lower latitudes through glacial flow. As previously evidenced by other VTMs, North-South asymmetries in surface properties can favor the development of one cap over the other. Our best-case simulations are obtained for a global reservoir of N2 ice thicker than 200 m and a bedrock thermal inertia larger than 500 SI. The large N2 ice reservoir implies a permanent N2 southern cap extending to the equator. Our results also suggest that a small permanent polar cap exists in the northern (currently winter) hemisphere if the internal heat flux remains radiogenic (< 3 mW m-2). Finally, we provide predictions for the evolution of ice distribution, surface pressure, CO and CH4 atmospheric mixing ratios in the next decades. We also model the thermal lightcurves of Triton in 2022, which serve as predictions for future JWST observations.

astro-ph.EP↗

arXiv2020

Spectral investigation of Ceres analogue mixtures: in-depth analysis of crater central peak material (ccp) on Ceres

In order to investigate the causes of different spectral slope in ccps, different grain-sizes of Ceres analogue mixtures were produced, heated to remove absorption of atmospheric water, and spectrally analyzed. First, the end-members which compose the Ceres surface (using the antigorite as Mg-phyllosilicate, the NH4-montmorillonite as NH4-phyllosilicate, the dolomite as carbonate and the graphite as dark component), were mixed, obtaining mixtures with different relative abundance, and identifying the mixture with the reflectance spectrum most similar to the average Ceres spectrum. The mixtures were obtained with grain size of 0-25 μm, 25-50 mic and 50-100 mic, were heated and spectrally analysed at T= 300 K and T=200 K (typical for surface Ceres temperature during VIR observations). The most similar Ceres analogue mixture is composed of dolomite (18%), graphite (27%), antigorite (32%) and NH4-montmorillonite (29%) and the results of this work suggest that this mixture is more similar to the Ceres youngest region than to the Ceres average, in particular for the negative slope of spectrum. Small variation in the composition and grain size of end-members need to be considered, in addition to the occurrence of a dark component dispersed in fine size. Furthermore, the positive spectral slope that characterizes the mean Ceres spectrum can be obtained by the application of some processes simulating the space weathering on Ceres (as micro-meteoritic impacts and solar wind irradiation), i.e. laser and ion irradiation. As conclusion, youngest ccps on Ceresare probably composed by fresher and weakly processed mixture with fine dark material intimately dispersed: as a result, the reflectance spectra of youngest material show a negative slope in the 1.2-1.9 mic range. The redder slope observed in the older ccps is probably the consequence of the space weathering effects on fresher material

astro-ph.EP↗

arXiv2020

Mineralogy, chemistry and composition of organic compounds in the fresh carbonaceous chondrite Mukundpura: CM1 or CM2?

We present here several laboratory analyses performed on the freshly fallen Mukundpura CM chondrite. Results of infrared transmission spectroscopy, thermogravimetry analysis and reflectance spectroscopy show that Mukundpura is mainly composed of phyllosilicates. The rare earth trace elements composition and ultrahigh resolution mass spectrometry of the soluble organic matter (SOM) give results consistent with CM chondrites. Finally, Raman spectroscopy shows no signs of thermal alteration of the meteorite. All the results agree that Mukundpura has been strongly altered by water on its parent body. Comparison of the results obtained on the meteorite with those of other chondrites of known petrologic types lead to the conclusion that Mukundpura is similar to CM1 chondrites, which differs from its original classification as a CM2.

astro-ph.EP↗

arXiv2020

On the Origin and Thermal Stability of Arrokoths and Plutos Ices

We discuss in a thermodynamic, geologically empirical way the long-term nature of the stable majority ices that could be present in Kuiper Belt Object 2014 MU69 after its 4.6 Gyr residence in the EKB as a cold classical object. Considering the stability versus sublimation into vacuum for the suite of ices commonly found on comets, Centaurs, and KBOs at the average ~40K sunlit surface temperature of MU69 over Myr to Gyr, we find only 3 common ices that are truly refractory: HCN, CH3OH, and H2O (in order of increasing stability). NH3 and H2CO ices are marginally stable and may be removed by any positive temperature excursions in the EKB, as produced every 1e8 - 1e9 yrs by nearby supernovae and passing O/B stars. To date the NH team has reported the presence of abundant CH3OH and evidence for H2O on MU69s surface (Lisse et al. 2017, Grundy et al. 2020). NH3 has been searched for, but not found. We predict that future absorption feature detections will be due to an HCN or poly-H2CO based species. Consideration of the conditions present in the EKB region during the formation era of MU69 lead us to infer that it formed "in the dark", in an optically thick mid-plane, unable to see the nascent, variable, highly luminous Young Stellar Object-TTauri Sun, and that KBOs contain HCN and CH3OH ice phases in addition to the H2O ice phases found in their Short Period comet descendants. Finally, when we apply our ice thermal stability analysis to bodies/populations related to MU69, we find that methanol ice may be ubiquitous in the outer solar system; that if Pluto is not a fully differentiated body, then it must have gained its hypervolatile ices from proto-planetary disk sources in the first few Myr of the solar systems existence; and that hypervolatile rich, highly primordial comet C/2016 R2 was placed onto an Oort Cloud orbit on a similar timescale.

astro-ph.EP↗

arXiv2020

Style and intensity of hydration among C-complex asteroids: a comparison to dessicated carbonaceous chondrites

Here we report a comparison between reflectance spectroscopy of meteorites under asteroidal environment (high vacuum and temperature) and Main Belt and Near Earth Asteroids spectra. Focusing on the OH absorption feature around 3μm, we show that the asteroidal environment induces a reduction of depth and width of the band, as well as a shift of the reflectance minimum. We then decompose the OH feature into several components with a new model using Exponentially Modified Gaussians. Unlike previous studies, we confirme the link between these components, the aqueous alteration history and the amount of water molecules inside of the sample, using the shape of this spectral feature only. We then apply this deconvolution model to asteroids spectra which were obtained with a space-borne telescope and two space probes, and find a strong similarity with the components detected on meteorites, and among asteroids from a same type. Based on the conclusions drawn from our meteorites experiment, we suggest to use the 3-μm band as a tracer of the alteration history of the small bodies. Using the 3-μm band only, we show that Ryugu has been heavily altered by water, which is consistent with its parent body being covered with water ice, then went through a high temperature sequence, over 400°C. We also point out that the 3-μm band of Bennu shows signs of its newly discovered surface activity.

astro-ph.EP↗

arXiv2020

Ammonium salts are a reservoir of nitrogen on a cometary nucleus and possibly on some asteroids

The measured nitrogen-to-carbon ratio in comets is lower than for the Sun, a discrepancy which could be alleviated if there is an unknown reservoir of nitrogen in comets. The nucleus of comet 67P/Churyumov-Gerasimenko exhibits an unidentified broad spectral reflectance feature around 3.2 micrometers, which is ubiquitous across its surface. On the basis of laboratory experiments, we attribute this absorption band to ammonium salts mixed with dust on the surface. The depth of the band indicates that semivolatile ammonium salts are a substantial reservoir of nitrogen in the comet, potentially dominating over refractory organic matter and more volatile species. Similar absorption features appear in the spectra of some asteroids, implying a compositional link between asteroids, comets, and the parent interstellar cloud.

astro-ph.EP↗

arXiv2020

Color, Composition, and Thermal Environment of Kuiper Belt Object (486958) Arrokoth

The outer Solar System object (486958) Arrokoth (provisional designation 2014 MU$_{69}$) has been largely undisturbed since its formation. We study its surface composition using data collected by the New Horizons spacecraft. Methanol ice is present along with organic material, which may have formed through radiation of simple molecules. Water ice was not detected. This composition indicates hydrogenation of carbon monoxide-rich ice and/ or energetic processing of methane condensed on water ice grains in the cold, outer edge of the early Solar System. There are only small regional variations in color and spectra across the surface, suggesting Arrokoth formed from a homogeneous or well-mixed reservoir of solids. Microwave thermal emission from the winter night side is consistent with a mean brightness temperature of 29$\pm$5 K.

astro-ph.EP↗

arXiv2020

Optical Design and Characterization of 40-GHz Detector and Module for the BICEP Array

Families of cosmic inflation models predict a primordial gravitational-wave background that imprints B-mode polarization pattern in the Cosmic Microwave Background (CMB). High sensitivity instruments with wide frequency coverage and well-controlled systematic errors are needed to constrain the faint B-mode amplitude. We have developed antenna-coupled Transition Edge Sensor (TES) arrays for high-sensitivity polarized CMB observations over a wide range of millimeter-wave bands. BICEP Array, the latest phase of the BICEP/Keck experiment series, is a multi-receiver experiment designed to search for inflationary B-mode polarization to a precision $σ$(r) between 0.002 and 0.004 after 3 full years of observations, depending on foreground complexity and the degree of lensing removal. We describe the electromagnetic design and measured performance of BICEP Array low-frequency 40-GHz detector, their packaging in focal plane modules, and optical characterization including efficiency and beam matching between polarization pairs. We summarize the design and simulated optical performance, including an approach to improve the optical efficiency due to mismatch losses. We report the measured beam maps for a new broad-band corrugation design to minimize beam differential ellipticity between polarization pairs caused by interactions with the module housing frame, which helps minimize polarized beam mismatch that converts CMB temperature to polarization ($T \rightarrow P$) anisotropy in CMB maps.

astro-ph.IM↗

arXiv2020

Design and performance of the first BICEP Array receiver

Branches of cosmic inflationary models, such as slow-roll inflation, predict a background of primordial gravitational waves that imprints a unique odd-parity B-mode pattern in the Cosmic Microwave Background (CMB) at amplitudes that are within experimental reach. The BICEP/Keck (BK) experiment targets this primordial signature, the amplitude of which is parameterized by the tensor-to-scalar ratio r, by observing the polarized microwave sky through the exceptionally clean and stable atmosphere at the South Pole. B-mode measurements require an instrument with exquisite sensitivity, tight control of systematics, and wide frequency coverage to disentangle the primordial signal from the Galactic foregrounds. BICEP Array represents the most recent stage of the BK program, and comprises four BICEP3-class receivers observing at 30/40, 95, 150 and 220/270 GHz. The 30/40 GHz receiver will be deployed at the South Pole during the 2019/2020 austral summer. After 3 full years of observations with 30,000+ detectors, BICEP Array will measure primordial gravitational waves to a precision $σ(r)$ between 0.002 and 0.004, depending on foreground complexity and the degree of lensing removal. In this paper we give an overview of the instrument, highlighting the design features in terms of cryogenics, magnetic shielding, detectors and readout architecture as well as reporting on the integration and tests that are ongoing with the first receiver at 30/40 GHz.

astro-ph.IM↗

arXiv2020

Characterizing the Sensitivity of 40 GHz TES Bolometers for BICEP Array

The BICEP/Keck (BK) experiment aims to detect the imprint of primordial gravitational waves in the Cosmic Microwave Background polarization, which would be direct evidence of the inflation theory. While the tensor-to-scalar ratio has been constrained to be r_0.05 < 0.06 at 95% c.l., further improvements on this upper limit are hindered by polarized Galactic foreground emissions and removal of gravitational lensing polarization. The 30/40 GHz receiver of the BICEP Array (BA) will deploy at the end of 2019 and will constrain the synchrotron foreground with unprecedented accuracy within the BK sky patch. We will show the design of the 30/40 GHz detectors and test results summarizing its performance. The low optical and atmospheric loading at these frequencies requires our TES detectors to have low saturation power in order to be photon-noise dominated. To realize the low thermal conductivity required from a 250 mK base temperature, we developed new bolometer leg designs. We will present the relevant measured detector parameters: G, Tc, Rn, Psat , and spectral bands, and noise spectra. We achieved a per bolometer NEP including all noise components of 2.07E-17 W/sqrt(Hz), including an anticipated photon noise level 1.54E-17 W/sqrt(Hz).

astro-ph.IM↗

arXiv2020

SHADOWS: a spectro-gonio radiometer for bidirectional reflectance studies of dark meteorites and terrestrial analogs: design, calibrations, and performances on challenging surfaces

We have developed a new spectro-gonio radiometer, SHADOWS, to study in the laboratory the bidirectional reflectance distribution function of dark and precious samples. The instrument operates over a wide spectral range from the visible to the near-infrared and is installed in a cold room. This paper presents the scientific and technical constraints of the spectro-gonio radiometer, its design and additional capabilities, as well as the performances and limitations of the instrument.

astro-ph.IM↗

arXiv2020

A model of the 3-μm hydration band with Exponentially Modified Gaussian (EMG) profiles: application to hydrated chondrites and asteroids

We present here a new method to model the shape of the 3-μm absorption band in the reflectance spectra of meteorites and small bodies. The band is decomposed into several OH/H2O components using Exponentially Modified Gaussian (EMG) profiles, as well as possible organic components using Gaussian profiles when present. We compare this model to polynomial and multiple Gaussian profile fits and show that the EMGs model returns the best rendering of the shape of the band, with significantly lower residuals. We also propose as an example an algorithm to estimate the error on the band parameters using a bootstrap method. We then present an application of the model to two spectral analyses of smectites subjected to different H2O vapor pressures, and present the variations of the components with decreasing humidity. This example emphasizes the ability of this model to coherently retrieve weak bands that are hidden within much stronger ones.

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