[en] Despite the impressive results achieved by microcalorimeters and bolometers, their performance is still significantly worse than that predicted by Mather's ideal model (Appl. Opt. 21 (1982) 1125). The difference is due both to non-ideal effects and to excess noise of unknown origin. The non-ideal effects have been recently quantified and include hot-electron effect, absorber decoupling, thermometer non-ohmic behavior, and all related extra noise sources. The excess noise affects primarily Transition Edge Sensors (TES) and is currently under experimental and theoretical investigation. This paper reviews the origin of non-ideal effects in microcalorimeters and bolometers and their effect on energy resolution and noise equivalent power. It also reviews the results on the characterization and suppression of the excess noise in TES, and the recent theoretical investigations to explain its origin in relation to fundamental physics in superconductors

[en] The status of the Genoa ¹⁸⁷Re β experiment, the final objective of which is to place limits on the mass of the electron anti-neutrino, will be presented. The latest measurements from a rhenium detector, composed of a NTD-Ge thermistor coupled to a small polycrystalline rhenium foil, will be discussed. An investigation of the expected final experimental performances using Monte Carlo simulation is also reported. (orig.)

[en] An outlook on the relevant progresses in the rhenium experiment with cryogenic detectors that has been made in the past year will be presented. We will discuss how the surrounding environment causes a ripple-like perturbation on the energy spectrum called Beta Environmental Fine Structure (BEFS). In 3 months of effective data acquisition we collected about 6 millions of events, achieving the sensitivity to observe for the first time the BEFS effect in the energy range 300-1600 eV, where its amplitude is at level of 1%. This distortion will have to be taken into account in the experiment in order to identify the kink in the high-energy end of the decay spectrum caused by a light neutrino

[en] In the environment of the 'Manu' experiment for the electron anti-neutrino mass determination with microcalorimeters, we developed a full system to analyze data and extract sensible results. Here we report on data simulation and analysis. We show that, with a single detector with the energy resolution we obtained up to now (15 eV RMS) and a rate of 1 Hz, we may put an upper limit to the electron anti-neutrino mass of the order of 20 eV at 95% C.L. in three months of data taking

[en] The University of Miami has recently started developing and studying high-resolution microcalorimeters operating near 100 mK for X-ray and particle physics and astrophysics. These detectors will be based on Transition Edge Sensors technology fabricated using iridium thin films deposited via the Pulsed Laser Deposition technique. We report here the preliminary result of the room temperature characterization of the Ir thin films, and an overview of future plans to use the films as transition edge sensors

[en] The performance of Transition Edge Sensors (TES) is limited by excess noise that is not predicted by the current theory of microcalorimeters and bolometers. The nature of this noise is currently unknown, but is likely to be dominated by fundamental physics of supeconductors. The University of Miami has recently started a joint effort between the microcalorimeter group and the superconductivity group to study and characterize the noise in TES. In particular, we plan to investigate the effect of flux motion due to self-field and external field and the effect of fluctuating order parameter by measuring the para-conductivity due to fluctuations in the number of Cooper pairs near the transition. We also plan to characterize the fundamental physical parameters of the TES to better predict their properties. In this paper we report our preliminary qualitative assessment of the problem, based on the literature, and we illustrate the experimental techniques that we plan to use for the investigation

[en] A cryogenic micro-calorimeter detector using a small bulk iridium single crystal as both absorber and as transition edge thermometer has been prepared. The detector is voltage biased, and the current through it is measured with a DC-SQUID. In this mode of operation an improvement of the detector performance by the electrothermal feedback is expected. In fact, we observed a stabilization of the working temperature due to this effect. By irradiating the micro-calorimeter with an ²⁴¹Am X-ray and γ-ray source an RMS energy resolution of σ=150 eV for 14 keV X-rays and σ=250 eV for 60 keV γ-rays was observed. (orig.)

[en] We analyzed data from a shadow observation of the high density molecular cloud MBM36 (l ∼ 4°, b ∼ 35°) with Suzaku. MBM36 is located in a region that emits relatively weakly in the 3/4 keV band compared to the surrounding North Polar Spur (NPS)/Loop 1 structure and the Galactic Bulge (GB). The contrast between high and low density targets in the MBM36 area allows one to separate the local and distant contributors to the soft diffuse X-ray background, providing a much better characterization of the individual components compared to single pointing observations. We identify two non-local thermal components, one at kT ≈ 0.12 keV and one at kT ≈ 0.29 keV. The colder component matches well with models of emission from the higher latitude region of the GB. The emission of the warmer component is in agreement with models predicting that the NPS is due to a hypershell from the center of the Milky Way. Geometrical and pressure calculations rule out a nearby bubble as responsible for the emission associated with the NPS. Any Galactic Halo/circumgalactic halo emission, if present, is outshined by the other components. We also report an excess emission around 0.9 keV, likely due to an overabundance of Ne ix

[en] We present here the analysis of X-ray point sources detected in several observations available in the XMM-Newton public archive. We focused, in particular, on energies below 1 keV, which are of particular relevance to the understanding of the diffuse X-ray background (DXB). The average field of all the exposures is 0.09 deg^-2. We reached an average flux sensitivity of 5.8 x 10^-16ergs^-1cm^-2 in the soft band (0.5-2.0 keV) and 2.5 x 10^-16ergs^-1cm^-2 in the very soft band (0.4-0.6 keV). In this paper, we discuss the log N-log S results, the contribution to the integrated X-ray sky flux, and the properties of the cumulative spectrum from all sources. In particular, we found an excess flux at around 0.5 keV in the composite spectrum of faint sources. The excess seems to be a general property of all the fields observed suggesting an additional class of weak sources is contributing to the X-ray emission at these energies. Combining our results with previous investigations, we have also quantified the contribution of the individual components of the DXB in the 3/4 keV band.

[en] We develop an estimator for the correlation function which, in the ensemble average, returns the shape of the correlation function, even for signals that have significant correlations on the scale of the survey region. Our estimator is general and works in any number of dimensions. We develop versions of the estimator for both diffuse and discrete signals. As an application, we apply them to Monte Carlo simulations of X-ray background measurements. These include a realistic, spatially inhomogeneous population of spurious detector events. We discuss applying the estimator to the averaging of correlation functions evaluated on several small fields, and to other cosmological applications.