Emanuele Taralli - Academia.edu (original) (raw)

Papers by Emanuele Taralli

Experimental Astronomy

The Athena X-ray Integral Unit (X-IFU) is the high resolution X-ray spectrometer studied since 20... more The Athena X-ray Integral Unit (X-IFU) is the high resolution X-ray spectrometer studied since 2015 for flying in the mid-30s on the Athena space X-ray Observatory. Athena is a versatile observatory designed to address the Hot and Energetic Universe science theme, as selected in November 2013 by the Survey Science Committee. Based on a large format array of Transition Edge Sensors (TES), X-IFU aims to provide spatially resolved X-ray spectroscopy, with a spectral resolution of 2.5 eV (up to 7 keV) over an hexagonal field of view of 5 arc minutes (equivalent diameter). The X-IFU entered its System Requirement Review (SRR) in June 2022, at about the same time when ESA called for an overall X-IFU redesign (including the X-IFU cryostat and the cooling chain), due to an unanticipated cost overrun of Athena. In this paper, after illustrating the breakthrough capabilities of the X-IFU, we describe the instrument as presented at its SRR (i.e. in the course of its preliminary definition phase, so-called B1), browsing through all the subsystems and associated requirements. We then show the instrument budgets, with a particular emphasis on the anticipated budgets of some of its key performance parameters, such as the instrument efficiency, spectral resolution, energy scale knowledge, count rate capability, non X-ray background and target of opportunity efficiency. Finally, we briefly discuss the ongoing key technology demonstration activities, the calibration and the activities foreseen in the X-IFU Instrument Science Center, touch on communication and outreach activities, the consortium organisation and the life cycle assessment of X-IFU aiming at minimising the environmental footprint, associated with the development of the instrument. Thanks to the studies conducted so far on X-IFU, it is expected that along the design-to-cost exercise requested by ESA, the X-IFU will maintain flagship capabilities in spatially resolved high resolution X-ray spectroscopy, enabling most of the original X-IFU related scientific objectives of the Athena mission to be retained.

Review of Scientific Instruments, 2021

Uniform large transition-edge sensor (TES) arrays are fundamental for the next generation of x-ra... more Uniform large transition-edge sensor (TES) arrays are fundamental for the next generation of x-ray space observatories. These arrays are required to achieve an energy resolution ΔE < 3 eV full width at half maximum (FWHM) in the soft x-ray energy range. We are currently developing x-ray microcalorimeter arrays for use in the future laboratory and space-based x-ray astrophysics experiments and ground-based spectrometers. In this contribution, we report on the development and the characterization of a uniform 32 × 32 pixel array with 140 × 30 μm2 Ti/Au TESs with the Au x-ray absorber. We report on extensive measurements on 60 pixels in order to show the uniformity of our large TES array. The averaged critical temperature is Tc = 89.5 ± 0.5 mK, and the variation across the array (∼1 cm) is less than 1.5 mK. We found a large region of detector’s bias points between 20% and 40% of the normal-state resistance where the energy resolution is constantly lower than 3 eV. In particular, res...

Review of Scientific Instruments, 2021

In the frequency-domain multiplexing (FDM) scheme, transition-edge sensors (TESs) are individuall... more In the frequency-domain multiplexing (FDM) scheme, transition-edge sensors (TESs) are individually coupled to superconducting LC filters and AC biased at MHz frequencies through a common readout line. To make efficient use of the available readout bandwidth and to minimize the effect of non-linearities, the LC resonators are usually designed to be on a regular grid. The lithographic processes, however, pose a limit on the accuracy of the effective filter resonance frequencies. Off-resonance bias carriers could be used to suppress the impact of intermodulation distortions, which, nonetheless, would significantly affect the effective bias circuit and the detector spectral performance. In this paper, we present a frequency shift algorithm (FSA) to allow off-resonance readout of TESs, while preserving the on-resonance bias circuit and spectral performance, demonstrating its application to the FDM readout of an x-ray TES microcalorimeter array. We discuss the benefits in terms of mitigat...

Development of microwave multiplexer for the Super DIOS mission: 38 transition-edge sensor x-ray microcalorimeter readout with microwave multiplexing

X-Ray, Optical, and Infrared Detectors for Astronomy IX, 2020

We are developing an x-ray imaging spectrometer for Super DIOS satellite mission, a future x-ray ... more We are developing an x-ray imaging spectrometer for Super DIOS satellite mission, a future x-ray observatory, planned by JAXA, to be launched in 2030’s. Super DIOS will reveal the nature of the missing baryon in the warm-hot intergalactic medium because of its fine energy and angular resolution, large effective area and large field of view. A main detector on-board Super DIOS consists of a transition-edge sensor (TES) microcalorimeter array of over 30,000 pixels working at a temperature below 100 mK and it poses a considerable technical difficulty to the readout. A microwave superconducting quantum interference device (SQUID) multiplexing is promising technique and expected to achieve a large scale readout of more than 30,000 pixels. We describe our development of a 40-channel microwave SQUID multiplexer with low-noise characteristics∗ and a demonstration of simultaneously reading out 40-pixel TESs. Finally, we discuss a future prospect and a feasibility of reading out an array of more than 30,000 pixels.

Quantum Efficiency in small area Transition-Edge Sensors (TESs)

Frequency domain multiplexing technology of transition-edge sensors for x-ray astronomy

Space Telescopes and Instrumentation 2020: Ultraviolet to Gamma Ray, 2020

IEEE Transactions on Applied Superconductivity, 2021

We have measured and characterized the thermal crosstalk in two different arrays of transition-ed... more We have measured and characterized the thermal crosstalk in two different arrays of transition-edge sensor (TES) Xray micro-calorimeters with frequency-domain multiplexing (FDM) readout. The TES arrays are fabricated at SRON and are a 8×8 and a 32×32 "kilo-pixel" uniform array. The amount of crosstalk is evaluated as the ratio between the averaged crosstalk signal and the X-ray pulse amplitudes. The crosstalk ratios (CR) for our detectors are compliant with the requirements for future X-ray space missions, such as Athena X-IFU (CR< 10 -3 for first-neighbour pixels): we measured a nearest-neighbour thermal crosstalk ratio at a level of 10 -4 , with a highest crosstalk ratio of 4 × 10 -4 for the kilo-pixel array (worst case, center of array) and 1 × 10 -4 for the 8×8 array, with a margin of improvement achievable by optimizing the Cu metallization and the width of the Si supporting structures (muntins) in the backside of the TES array chip. Based on the measured crosstalk ratios, we have estimated the impact on the spectral resolution by means of noise equivalent power (NEP) considerations and a Monte Carlo simulation, finding an average degradation in quadrature of less than 40 meV, compliant with the < 0.2 eV requirement for Athena X-IFU.

Applied Physics Letters, 2020

We report very-low-noise, fast-response, middle-scale multiplexing in a microwave superconducting... more We report very-low-noise, fast-response, middle-scale multiplexing in a microwave superconducting quantum interference device multiplexer (MW-Mux) as a transition-edge sensor (TES) readout. Our MW-Mux is able to read 40 channels with 500 kHz sampling and has a low readout noise of 0.9 μΦ0/Hz (where Φ0 is the magnetic flux quantum), equivalent to 9 pA/Hz. By contrast, a multiplexer of less than 10 pixels with 500 kHz sampling and ∼2 μΦ0/Hz readout noise has so far been reported in the literature. Owing to the 500 kHz sampling, our MW-Mux exhibits a fast response to detect a TES pulse with a rise time around 12 μs. We demonstrated simultaneous readout of 38 pixels from an array of x-ray TES microcalorimeters. The measured full-width values at half-maximum spectral resolution ranged from 2.79 to 4.56 eV, with a median value of 3.30 eV at 5.9 keV, including a ∼10% contribution of readout noise, i.e., 0.9–1.7 eV.

IEEE Transactions on Applied Superconductivity, 2021

Large format arrays of transition edge sensor (TES) are crucial for the next generation of X-ray ... more Large format arrays of transition edge sensor (TES) are crucial for the next generation of X-ray space observatories. Such arrays are required to achieve an energy resolution of ∆E < 3 eV full-width-half-maximum (FWHM) in the soft X-ray energy range. We are currently developing X-ray microcalorimeter arrays as a backup option for the X-IFU instrument on board of ATHENA space telescope, led by ESA and foreseen to be launched in 2031. In this contribution, we report on the development and the characterization of a uniform 32×32 pixel array with (length×width) 140×30 µm 2 TiAu TESs, which have a 2.3 µm thick Au absorber for X-ray photons. The pixels have a typical normal resistance R n = 121 mΩ and a critical temperature T c ∼ 90 mK. We performed extensive measurements on 60 pixels out of the array in order to show the uniformity of the array. We obtained an energy resolutions between 2.4 and 2.6 eV (FWHM) at 5.9 keV, measured in a single-pixel mode at AC bias frequencies ranging from 1 to 5 MHz, with a frequency domain multiplexing (FDM) readout system, which is developed at SRON/VTT. We also present the detector energy resolution at X-ray with different photon energies generated by a modulated external X-ray source from 1.45 keV up to 8.9 keV. Multiplexing readout across several pixels has also been performed to evaluate the impact of the thermal crosstalk to the instrument's energy resolution budget requirement. This value results in a derived requirement, for the first neighbour, that is less than 1×10 -3 when considering the ratio between the amplitude of the crosstalk signal to an X-ray pulse (for example at 5.9 keV).

IEEE Transactions on Applied Superconductivity, 2021

We are developing a kilo-pixels Ti/Au TES array as a backup option for Athena X-IFU. Here we repo... more We are developing a kilo-pixels Ti/Au TES array as a backup option for Athena X-IFU. Here we report on single-pixel performance of a 32×32 array operated in a Frequency Division Multiplexing (FDM) readout system, with bias frequencies in the range 1-5 MHz. We have tested the pixels response at several photon energies, by means of a 55 Fe radioactive source (emitting Mn-Kα at 5.9 keV) and a Modulated X-ray Source (MXS, providing Cr-Kα at 5.4 keV and Cu-Kα at 8.0 keV). First, we report the procedure used to perform the detector energy scale calibration, usually achieving a calibration accuracy better than ∼ 0.5 eV in the 5.4 -8.9 keV energy range. Then, we present the measured energy resolution at the different energies (best single pixel performance: ∆EFWHM = 2.40 ± 0.

Journal of Low Temperature Physics, 2020

We are developing the frequency-domain multiplexing (FDM) readout for the SAFARI far-infrared spe... more We are developing the frequency-domain multiplexing (FDM) readout for the SAFARI far-infrared spectrometer on board the SPICA space observatory. Each readout channel comprises a set of ~ 160 TESs and LC filters and is read out with a SQUID preamplifier. Baseband feedback is applied to overcome the dynamic range limitations of the SQUID. We have carried out extensive characterization of a test readout system coupled to a 176-pixel TES bolometer array in order to understand and optimize the system. We present our latest measurements of this 176-pixel FDM demonstrator, focusing on the noise contribution from the SQUID.

Sensors, 2017

The increasing demand for light emitting diodes (LEDs) is driven by a number of application categ... more The increasing demand for light emitting diodes (LEDs) is driven by a number of application categories, including display backlighting, communications, signage, and general illumination. Nowadays, they have also become attractive candidates as new photometric standards. In recent years, LEDs have started to be applied as wavelength-selective photo-detectors as well. Nevertheless, manufacturers' datasheets are limited about LEDs used as sources in terms of degradation with operating time (aging) or shifting of the emission spectrum as a function of the forward current. On the contrary, as far as detection is concerned, information about spectral responsivity of LEDs is missing. We investigated, mainly from a radiometric point of view, more than 50 commercial LEDs of a wide variety of wavelength bands, ranging from ultraviolet (UV) to near infrared (NIR). Originally, the final aim was to find which LEDs could better work together as detector-emitter pairs for the creation of self-calibrating ground-viewing LED radiometers; however, the findings that we are sharing here following, have a general validity that could be exploited in several sensing applications.

Sensors, 2016

Transition-edge sensors (TESs) are single photon detectors attractive for applications in quantum... more Transition-edge sensors (TESs) are single photon detectors attractive for applications in quantum optics and quantum information experiments owing to their photon number resolving capability. Nowadays, high-energy resolution TESs for telecommunication are based on either W or Au/Ti films, demonstrating slow recovery time constants. We report our progress on the development of an Al/Ti TES. Since bulk aluminum has a critical temperature (T c ) of ca. 1.2 K and a sufficiently low specific heat (less than 10 ´4 J/cm 3 K 2 ), it can be employed to produce the sensitive material for optical TESs. Furthermore, exploiting its high T c , Al-based TESs can be trimmed in a wider temperature range with respect to Ti or W. A first Al/Ti TES with a T c « 142 mK, investigated from a thermal and optical point of view, has shown a response time constant of about 2 µs and single photon discrimination with 0.34 eV energy resolution at telecom wavelength, demonstrating that Al/Ti films are suitable to produce TESs for visible and NIR photon counting.

Quantum Matter, 2015

This paper's purpose is to review the results recently obtained in the Quantum Optics labs of the... more This paper's purpose is to review the results recently obtained in the Quantum Optics labs of the National Institute of Metrological Research (INRIM) in the field of single-and few-photon detectors calibration, from both the classical and quantum viewpoint. In the first part of the paper is presented the calibration of a single-photon detector with absolute methods, while in the second part we focus on photonnumber-resolving detectors, discussing both the classical and quantum characterization of such devices.

Nuovo Cimento- Societa Italiana di Fisica Sezione C

Transition-Edge Sensors (TESs) are microcalorimeters that measure the energy of incident single p... more Transition-Edge Sensors (TESs) are microcalorimeters that measure the energy of incident single photons by the resistance increase of a, superconducting film biased within the superconducting-to-normal transition. TES are able to detect single photons from IR. to X-ray with an intrinsic energy resolution and photon-number discrimination capability. Metrology, astronomy and quantum communication are the fields where these properties can be particularly useful. In this work, we report about characterization of different TESs based on Ti films. Single photons have been detected from 200 nm to 800 nm working at transition temperature T(c) similar to 100 mK. Using a pulsed laser at 690 nm we have demonstrated the capability to resolve up to five photons.

Full characterization of optical Transition-Edge Sensor by impedance spectroscopy measurements in a bandwidth extending to 1 MHz

2013 IEEE 14th International Superconductive Electronics Conference (ISEC), 2013

ABSTRACT Transition-Edge Sensors (TESs) are the most promising devices as single photon detectors... more ABSTRACT Transition-Edge Sensors (TESs) are the most promising devices as single photon detectors in the visible and infrared range. In particular ultra-fast TESs with few hundred ns response time and high quantum efficiency find application in different fields like quantum optics, quantum metrology and quantum information. The full characterization of such detectors from thermal, electrical and optical point of view is not so simple, because only some parameters are directly measurable. There are several works where various models and set of measurements are proposed to describe X- and γ-ray TES, devices with response time in the order of 100 μs. In this work, we analyze ultra-fast TES (10 μm × 10 μm area and 34 nm thick) combining for the first time TES bias curves, measurements of complex impedance, and noise measurements. In particular we perform complex impedance measurements up to 1 MHz. All the obtained results are explained using the simplest calorimeter thermal model, that is suitable for TES without external absorber.

Improvement of titanium film absorption with antireflection coatings

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2006

... E. Taralli a , Corresponding Author Contact Information , E-mail The Corresponding Author , C... more ... E. Taralli a , Corresponding Author Contact Information , E-mail The Corresponding Author , C. Portesi a , C. Ricciardi b , E. Tresso b and M. Rajteri a. ... [6] ED Palik, Handbook of Optical Constants of Solids, Academic Press, San Diego (1998). ...

Superconducting MgB2nanobridges and meanders obtained by an electron beam lithography-based technique on different substrates

Superconductor Science and Technology, 2008

ABSTRACT In this work, we report on the fabrication and characterization of MgB2 nanostructures o... more ABSTRACT In this work, we report on the fabrication and characterization of MgB2 nanostructures on different substrates, namely silicon nitride and sapphire. Magnesium diboride films are fabricated by an all-in situ method consisting of the co-evaporation of B and Mg followed by in situ annealing at higher temperature. Samples thus obtained are characterized at low temperature and show a Tc of about 34-38 K. The nanostructures are then defined by electron beam lithography combined with physical etching (reactive plasma etching and ion milling). In this way, MgB2 nanostructures and meanders have been obtained with rather good electrical and transport properties both on SiN and sapphire. The fabrication of superconducting MgB2 nanobridges on sapphire with a thickness of the order of a few tens of nanometers represents a step forward in the field of nanodevices, such as single-photon detectors, based on this mid-temperature superconducting material.

Fabrication and characterization of an MgB 2 bolometer

Superconductor Science and Technology, 2007

ABSTRACT In this work, we present the experimental results obtained in the fabrication and charac... more ABSTRACT In this work, we present the experimental results obtained in the fabrication and characterization of a superconducting MgB2 bolometer. The device was made from an MgB2 meander-like structure suspended on a 500 nm thick SiN membrane. The MgB2 meander line was 50 µm wide and 7.6 mm long and it was defined by optical lithography and dry etching. The SiN membrane had an area of 1.3 mm × 1.3 mm and it was obtained by a silicon micromachining technique. The electrical and thermal properties of the device were measured at low temperature in a closed-cycle cryocooler. The resulting Tc of the meander was unchanged with respect to the unprocessed film and the transport properties, measured in voltage-biased mode, indicated a value for Jc of the order of 105 A cm−2 at 27 K. The logarithmic sensitivity of the bolometer turned out to be higher than 150. The study of the thermal properties of the bolometer on the membrane showed a thermal conductance of the order 10−5 W K−1 at a working temperature of 32 K. The bolometer, irradiated by a chopped laser beam, showed a cut-off frequency of 94 Hz. The maximum experimental responsivity was estimated to be 2.3 × 103 V W−1.

Optics Express, 2011

Well characterized photon number resolving detectors are a requirement for many applications rang... more Well characterized photon number resolving detectors are a requirement for many applications ranging from quantum information and quantum metrology to the foundations of quantum mechanics. This prompts the necessity for reliable calibration techniques at the single photon level. In this paper we propose an innovative absolute calibration technique for photon number resolving detectors, using a pulsed heralded photon source based on parametric down conversion. The technique, being absolute, does not require reference standards and is independent upon the performances of the heralding detector. The method provides the results of quantum efficiency for the heralded detector as a function of detected photon numbers. Furthermore, we prove its validity by performing the calibration of a Transition Edge Sensor based detector, a real photon number resolving detector that has recently demonstrated its effectiveness in various quantum information protocols.

Experimental Astronomy

The Athena X-ray Integral Unit (X-IFU) is the high resolution X-ray spectrometer studied since 20... more The Athena X-ray Integral Unit (X-IFU) is the high resolution X-ray spectrometer studied since 2015 for flying in the mid-30s on the Athena space X-ray Observatory. Athena is a versatile observatory designed to address the Hot and Energetic Universe science theme, as selected in November 2013 by the Survey Science Committee. Based on a large format array of Transition Edge Sensors (TES), X-IFU aims to provide spatially resolved X-ray spectroscopy, with a spectral resolution of 2.5 eV (up to 7 keV) over an hexagonal field of view of 5 arc minutes (equivalent diameter). The X-IFU entered its System Requirement Review (SRR) in June 2022, at about the same time when ESA called for an overall X-IFU redesign (including the X-IFU cryostat and the cooling chain), due to an unanticipated cost overrun of Athena. In this paper, after illustrating the breakthrough capabilities of the X-IFU, we describe the instrument as presented at its SRR (i.e. in the course of its preliminary definition phase, so-called B1), browsing through all the subsystems and associated requirements. We then show the instrument budgets, with a particular emphasis on the anticipated budgets of some of its key performance parameters, such as the instrument efficiency, spectral resolution, energy scale knowledge, count rate capability, non X-ray background and target of opportunity efficiency. Finally, we briefly discuss the ongoing key technology demonstration activities, the calibration and the activities foreseen in the X-IFU Instrument Science Center, touch on communication and outreach activities, the consortium organisation and the life cycle assessment of X-IFU aiming at minimising the environmental footprint, associated with the development of the instrument. Thanks to the studies conducted so far on X-IFU, it is expected that along the design-to-cost exercise requested by ESA, the X-IFU will maintain flagship capabilities in spatially resolved high resolution X-ray spectroscopy, enabling most of the original X-IFU related scientific objectives of the Athena mission to be retained.

Review of Scientific Instruments, 2021

Uniform large transition-edge sensor (TES) arrays are fundamental for the next generation of x-ra... more Uniform large transition-edge sensor (TES) arrays are fundamental for the next generation of x-ray space observatories. These arrays are required to achieve an energy resolution ΔE < 3 eV full width at half maximum (FWHM) in the soft x-ray energy range. We are currently developing x-ray microcalorimeter arrays for use in the future laboratory and space-based x-ray astrophysics experiments and ground-based spectrometers. In this contribution, we report on the development and the characterization of a uniform 32 × 32 pixel array with 140 × 30 μm2 Ti/Au TESs with the Au x-ray absorber. We report on extensive measurements on 60 pixels in order to show the uniformity of our large TES array. The averaged critical temperature is Tc = 89.5 ± 0.5 mK, and the variation across the array (∼1 cm) is less than 1.5 mK. We found a large region of detector’s bias points between 20% and 40% of the normal-state resistance where the energy resolution is constantly lower than 3 eV. In particular, res...

Review of Scientific Instruments, 2021

In the frequency-domain multiplexing (FDM) scheme, transition-edge sensors (TESs) are individuall... more In the frequency-domain multiplexing (FDM) scheme, transition-edge sensors (TESs) are individually coupled to superconducting LC filters and AC biased at MHz frequencies through a common readout line. To make efficient use of the available readout bandwidth and to minimize the effect of non-linearities, the LC resonators are usually designed to be on a regular grid. The lithographic processes, however, pose a limit on the accuracy of the effective filter resonance frequencies. Off-resonance bias carriers could be used to suppress the impact of intermodulation distortions, which, nonetheless, would significantly affect the effective bias circuit and the detector spectral performance. In this paper, we present a frequency shift algorithm (FSA) to allow off-resonance readout of TESs, while preserving the on-resonance bias circuit and spectral performance, demonstrating its application to the FDM readout of an x-ray TES microcalorimeter array. We discuss the benefits in terms of mitigat...

Development of microwave multiplexer for the Super DIOS mission: 38 transition-edge sensor x-ray microcalorimeter readout with microwave multiplexing

X-Ray, Optical, and Infrared Detectors for Astronomy IX, 2020

We are developing an x-ray imaging spectrometer for Super DIOS satellite mission, a future x-ray ... more We are developing an x-ray imaging spectrometer for Super DIOS satellite mission, a future x-ray observatory, planned by JAXA, to be launched in 2030’s. Super DIOS will reveal the nature of the missing baryon in the warm-hot intergalactic medium because of its fine energy and angular resolution, large effective area and large field of view. A main detector on-board Super DIOS consists of a transition-edge sensor (TES) microcalorimeter array of over 30,000 pixels working at a temperature below 100 mK and it poses a considerable technical difficulty to the readout. A microwave superconducting quantum interference device (SQUID) multiplexing is promising technique and expected to achieve a large scale readout of more than 30,000 pixels. We describe our development of a 40-channel microwave SQUID multiplexer with low-noise characteristics∗ and a demonstration of simultaneously reading out 40-pixel TESs. Finally, we discuss a future prospect and a feasibility of reading out an array of more than 30,000 pixels.

Quantum Efficiency in small area Transition-Edge Sensors (TESs)

Frequency domain multiplexing technology of transition-edge sensors for x-ray astronomy

Space Telescopes and Instrumentation 2020: Ultraviolet to Gamma Ray, 2020

IEEE Transactions on Applied Superconductivity, 2021

We have measured and characterized the thermal crosstalk in two different arrays of transition-ed... more We have measured and characterized the thermal crosstalk in two different arrays of transition-edge sensor (TES) Xray micro-calorimeters with frequency-domain multiplexing (FDM) readout. The TES arrays are fabricated at SRON and are a 8×8 and a 32×32 "kilo-pixel" uniform array. The amount of crosstalk is evaluated as the ratio between the averaged crosstalk signal and the X-ray pulse amplitudes. The crosstalk ratios (CR) for our detectors are compliant with the requirements for future X-ray space missions, such as Athena X-IFU (CR< 10 -3 for first-neighbour pixels): we measured a nearest-neighbour thermal crosstalk ratio at a level of 10 -4 , with a highest crosstalk ratio of 4 × 10 -4 for the kilo-pixel array (worst case, center of array) and 1 × 10 -4 for the 8×8 array, with a margin of improvement achievable by optimizing the Cu metallization and the width of the Si supporting structures (muntins) in the backside of the TES array chip. Based on the measured crosstalk ratios, we have estimated the impact on the spectral resolution by means of noise equivalent power (NEP) considerations and a Monte Carlo simulation, finding an average degradation in quadrature of less than 40 meV, compliant with the < 0.2 eV requirement for Athena X-IFU.

Applied Physics Letters, 2020

We report very-low-noise, fast-response, middle-scale multiplexing in a microwave superconducting... more We report very-low-noise, fast-response, middle-scale multiplexing in a microwave superconducting quantum interference device multiplexer (MW-Mux) as a transition-edge sensor (TES) readout. Our MW-Mux is able to read 40 channels with 500 kHz sampling and has a low readout noise of 0.9 μΦ0/Hz (where Φ0 is the magnetic flux quantum), equivalent to 9 pA/Hz. By contrast, a multiplexer of less than 10 pixels with 500 kHz sampling and ∼2 μΦ0/Hz readout noise has so far been reported in the literature. Owing to the 500 kHz sampling, our MW-Mux exhibits a fast response to detect a TES pulse with a rise time around 12 μs. We demonstrated simultaneous readout of 38 pixels from an array of x-ray TES microcalorimeters. The measured full-width values at half-maximum spectral resolution ranged from 2.79 to 4.56 eV, with a median value of 3.30 eV at 5.9 keV, including a ∼10% contribution of readout noise, i.e., 0.9–1.7 eV.

IEEE Transactions on Applied Superconductivity, 2021

Large format arrays of transition edge sensor (TES) are crucial for the next generation of X-ray ... more Large format arrays of transition edge sensor (TES) are crucial for the next generation of X-ray space observatories. Such arrays are required to achieve an energy resolution of ∆E < 3 eV full-width-half-maximum (FWHM) in the soft X-ray energy range. We are currently developing X-ray microcalorimeter arrays as a backup option for the X-IFU instrument on board of ATHENA space telescope, led by ESA and foreseen to be launched in 2031. In this contribution, we report on the development and the characterization of a uniform 32×32 pixel array with (length×width) 140×30 µm 2 TiAu TESs, which have a 2.3 µm thick Au absorber for X-ray photons. The pixels have a typical normal resistance R n = 121 mΩ and a critical temperature T c ∼ 90 mK. We performed extensive measurements on 60 pixels out of the array in order to show the uniformity of the array. We obtained an energy resolutions between 2.4 and 2.6 eV (FWHM) at 5.9 keV, measured in a single-pixel mode at AC bias frequencies ranging from 1 to 5 MHz, with a frequency domain multiplexing (FDM) readout system, which is developed at SRON/VTT. We also present the detector energy resolution at X-ray with different photon energies generated by a modulated external X-ray source from 1.45 keV up to 8.9 keV. Multiplexing readout across several pixels has also been performed to evaluate the impact of the thermal crosstalk to the instrument's energy resolution budget requirement. This value results in a derived requirement, for the first neighbour, that is less than 1×10 -3 when considering the ratio between the amplitude of the crosstalk signal to an X-ray pulse (for example at 5.9 keV).

IEEE Transactions on Applied Superconductivity, 2021

We are developing a kilo-pixels Ti/Au TES array as a backup option for Athena X-IFU. Here we repo... more We are developing a kilo-pixels Ti/Au TES array as a backup option for Athena X-IFU. Here we report on single-pixel performance of a 32×32 array operated in a Frequency Division Multiplexing (FDM) readout system, with bias frequencies in the range 1-5 MHz. We have tested the pixels response at several photon energies, by means of a 55 Fe radioactive source (emitting Mn-Kα at 5.9 keV) and a Modulated X-ray Source (MXS, providing Cr-Kα at 5.4 keV and Cu-Kα at 8.0 keV). First, we report the procedure used to perform the detector energy scale calibration, usually achieving a calibration accuracy better than ∼ 0.5 eV in the 5.4 -8.9 keV energy range. Then, we present the measured energy resolution at the different energies (best single pixel performance: ∆EFWHM = 2.40 ± 0.

Journal of Low Temperature Physics, 2020

We are developing the frequency-domain multiplexing (FDM) readout for the SAFARI far-infrared spe... more We are developing the frequency-domain multiplexing (FDM) readout for the SAFARI far-infrared spectrometer on board the SPICA space observatory. Each readout channel comprises a set of ~ 160 TESs and LC filters and is read out with a SQUID preamplifier. Baseband feedback is applied to overcome the dynamic range limitations of the SQUID. We have carried out extensive characterization of a test readout system coupled to a 176-pixel TES bolometer array in order to understand and optimize the system. We present our latest measurements of this 176-pixel FDM demonstrator, focusing on the noise contribution from the SQUID.

Sensors, 2017

The increasing demand for light emitting diodes (LEDs) is driven by a number of application categ... more The increasing demand for light emitting diodes (LEDs) is driven by a number of application categories, including display backlighting, communications, signage, and general illumination. Nowadays, they have also become attractive candidates as new photometric standards. In recent years, LEDs have started to be applied as wavelength-selective photo-detectors as well. Nevertheless, manufacturers' datasheets are limited about LEDs used as sources in terms of degradation with operating time (aging) or shifting of the emission spectrum as a function of the forward current. On the contrary, as far as detection is concerned, information about spectral responsivity of LEDs is missing. We investigated, mainly from a radiometric point of view, more than 50 commercial LEDs of a wide variety of wavelength bands, ranging from ultraviolet (UV) to near infrared (NIR). Originally, the final aim was to find which LEDs could better work together as detector-emitter pairs for the creation of self-calibrating ground-viewing LED radiometers; however, the findings that we are sharing here following, have a general validity that could be exploited in several sensing applications.

Sensors, 2016

Transition-edge sensors (TESs) are single photon detectors attractive for applications in quantum... more Transition-edge sensors (TESs) are single photon detectors attractive for applications in quantum optics and quantum information experiments owing to their photon number resolving capability. Nowadays, high-energy resolution TESs for telecommunication are based on either W or Au/Ti films, demonstrating slow recovery time constants. We report our progress on the development of an Al/Ti TES. Since bulk aluminum has a critical temperature (T c ) of ca. 1.2 K and a sufficiently low specific heat (less than 10 ´4 J/cm 3 K 2 ), it can be employed to produce the sensitive material for optical TESs. Furthermore, exploiting its high T c , Al-based TESs can be trimmed in a wider temperature range with respect to Ti or W. A first Al/Ti TES with a T c « 142 mK, investigated from a thermal and optical point of view, has shown a response time constant of about 2 µs and single photon discrimination with 0.34 eV energy resolution at telecom wavelength, demonstrating that Al/Ti films are suitable to produce TESs for visible and NIR photon counting.

Quantum Matter, 2015

This paper's purpose is to review the results recently obtained in the Quantum Optics labs of the... more This paper's purpose is to review the results recently obtained in the Quantum Optics labs of the National Institute of Metrological Research (INRIM) in the field of single-and few-photon detectors calibration, from both the classical and quantum viewpoint. In the first part of the paper is presented the calibration of a single-photon detector with absolute methods, while in the second part we focus on photonnumber-resolving detectors, discussing both the classical and quantum characterization of such devices.

Nuovo Cimento- Societa Italiana di Fisica Sezione C

Transition-Edge Sensors (TESs) are microcalorimeters that measure the energy of incident single p... more Transition-Edge Sensors (TESs) are microcalorimeters that measure the energy of incident single photons by the resistance increase of a, superconducting film biased within the superconducting-to-normal transition. TES are able to detect single photons from IR. to X-ray with an intrinsic energy resolution and photon-number discrimination capability. Metrology, astronomy and quantum communication are the fields where these properties can be particularly useful. In this work, we report about characterization of different TESs based on Ti films. Single photons have been detected from 200 nm to 800 nm working at transition temperature T(c) similar to 100 mK. Using a pulsed laser at 690 nm we have demonstrated the capability to resolve up to five photons.

Full characterization of optical Transition-Edge Sensor by impedance spectroscopy measurements in a bandwidth extending to 1 MHz

2013 IEEE 14th International Superconductive Electronics Conference (ISEC), 2013

ABSTRACT Transition-Edge Sensors (TESs) are the most promising devices as single photon detectors... more ABSTRACT Transition-Edge Sensors (TESs) are the most promising devices as single photon detectors in the visible and infrared range. In particular ultra-fast TESs with few hundred ns response time and high quantum efficiency find application in different fields like quantum optics, quantum metrology and quantum information. The full characterization of such detectors from thermal, electrical and optical point of view is not so simple, because only some parameters are directly measurable. There are several works where various models and set of measurements are proposed to describe X- and γ-ray TES, devices with response time in the order of 100 μs. In this work, we analyze ultra-fast TES (10 μm × 10 μm area and 34 nm thick) combining for the first time TES bias curves, measurements of complex impedance, and noise measurements. In particular we perform complex impedance measurements up to 1 MHz. All the obtained results are explained using the simplest calorimeter thermal model, that is suitable for TES without external absorber.

Improvement of titanium film absorption with antireflection coatings

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2006

... E. Taralli a , Corresponding Author Contact Information , E-mail The Corresponding Author , C... more ... E. Taralli a , Corresponding Author Contact Information , E-mail The Corresponding Author , C. Portesi a , C. Ricciardi b , E. Tresso b and M. Rajteri a. ... [6] ED Palik, Handbook of Optical Constants of Solids, Academic Press, San Diego (1998). ...

Superconducting MgB2nanobridges and meanders obtained by an electron beam lithography-based technique on different substrates

Superconductor Science and Technology, 2008

ABSTRACT In this work, we report on the fabrication and characterization of MgB2 nanostructures o... more ABSTRACT In this work, we report on the fabrication and characterization of MgB2 nanostructures on different substrates, namely silicon nitride and sapphire. Magnesium diboride films are fabricated by an all-in situ method consisting of the co-evaporation of B and Mg followed by in situ annealing at higher temperature. Samples thus obtained are characterized at low temperature and show a Tc of about 34-38 K. The nanostructures are then defined by electron beam lithography combined with physical etching (reactive plasma etching and ion milling). In this way, MgB2 nanostructures and meanders have been obtained with rather good electrical and transport properties both on SiN and sapphire. The fabrication of superconducting MgB2 nanobridges on sapphire with a thickness of the order of a few tens of nanometers represents a step forward in the field of nanodevices, such as single-photon detectors, based on this mid-temperature superconducting material.

Fabrication and characterization of an MgB 2 bolometer

Superconductor Science and Technology, 2007

ABSTRACT In this work, we present the experimental results obtained in the fabrication and charac... more ABSTRACT In this work, we present the experimental results obtained in the fabrication and characterization of a superconducting MgB2 bolometer. The device was made from an MgB2 meander-like structure suspended on a 500 nm thick SiN membrane. The MgB2 meander line was 50 µm wide and 7.6 mm long and it was defined by optical lithography and dry etching. The SiN membrane had an area of 1.3 mm × 1.3 mm and it was obtained by a silicon micromachining technique. The electrical and thermal properties of the device were measured at low temperature in a closed-cycle cryocooler. The resulting Tc of the meander was unchanged with respect to the unprocessed film and the transport properties, measured in voltage-biased mode, indicated a value for Jc of the order of 105 A cm−2 at 27 K. The logarithmic sensitivity of the bolometer turned out to be higher than 150. The study of the thermal properties of the bolometer on the membrane showed a thermal conductance of the order 10−5 W K−1 at a working temperature of 32 K. The bolometer, irradiated by a chopped laser beam, showed a cut-off frequency of 94 Hz. The maximum experimental responsivity was estimated to be 2.3 × 103 V W−1.

Optics Express, 2011

Well characterized photon number resolving detectors are a requirement for many applications rang... more Well characterized photon number resolving detectors are a requirement for many applications ranging from quantum information and quantum metrology to the foundations of quantum mechanics. This prompts the necessity for reliable calibration techniques at the single photon level. In this paper we propose an innovative absolute calibration technique for photon number resolving detectors, using a pulsed heralded photon source based on parametric down conversion. The technique, being absolute, does not require reference standards and is independent upon the performances of the heralding detector. The method provides the results of quantum efficiency for the heralded detector as a function of detected photon numbers. Furthermore, we prove its validity by performing the calibration of a Transition Edge Sensor based detector, a real photon number resolving detector that has recently demonstrated its effectiveness in various quantum information protocols.