Bolometric Detectors Research Articles

A flexible and compact electronic system for the bolometric diagnostic with on-line calibration capability

At ENEA Frascati laboratories an updated electronic system for the bolometric diagnostic is under development. The system is based on the most recent electronic technology and it is able to manage a large number of channels. It is flexible, reliable and compact in order to be suitable for applications on large fusion experimental machines or reactors. The system has been conceived to be applied to bolometric detectors based on a resistive bridge, it is mainly based on the digital signal processing technology to guarantee high accuracy, large dynamic range and a high signal to noise ratio. It is also able to manage a large offset of the bridges. A further important feature of the system is the embedded calibration capability of the sensor detectors that allows for the calibration of each channel in parallel and in a very short time with the bolometer heads installed and without any manual intervention on the lay-out, thus also allowing for calibration just shortly before the plasma experiment. A further fast embedded on-line calibration capability allows for the estimation of the sensor temperature and of the temperature gradient in the bolometer head, inside the bolometer measurement temporal window. The paper describes the main concepts, the general architecture of the system and in detail the calibration and the on-line calibration functionalities.

First test of a Li2WO4(Mo) bolometric detector for the measurement of coherent neutrino-nucleus scattering

Abstract The first observation of coherent elastic neutrino-nucleus scattering (CE ν NS), reported by the COHERENT Collaboration in 2017, paved the way for a new generation of experiments using reactor ν e and aiming at precisely measuring this process. In this context, the BASKET (Bolometers At Sub-KeV Energy Thresholds) R&D project investigates the use of cryogenic detectors for a reactor CE ν NS experiment. This article reports on the first test of a Mo-doped lithium tungstate scintillating bolometer ( ⊘ 18 × 7 mm, 8 g), performed in an aboveground laboratory at CSNSM, Orsay (France). The detector bolometric performance (energy and time response, particle identification capabilities) and radiopurity have been studied and confirm the promising potential of lithium tungstate-based bolometric detectors for the measurement of CE ν NS at reactors.

Study of the effect of external noise pickups on the performance of a cryogenic bolometer.

This paper reports the detailed noise characterization, investigation of various noise sources, and its mitigation to improve the performance of a cryogenic bolometer detector for the TIN.TIN experiment. The noise spectrum has been measured for a sapphire bolometer test setup with an indigenously developed neutron transmutation doped Ge sensor in the cryogen free dilution refrigerator system at Mumbai. The effect of external noise, arising either from ground loops in the system or from the diagnostic and control electronics of the cryostat, on the performance of the bolometer is assessed. A systematic comparison of the influence of different noise pickups on the bolometer resolution is also presented. The best-achieved resolution (σE) at 15 mK is ∼15 keV for heater pulses and appears to be mainly limited by the noise due to the pulse tube cryocooler.

MBE-grown MCT hetero- and nanostructures for IR and THz detectors

We present an overview of our technological achievements in the implementation of detector structures based on mercury cadmium telluride (MCT) heterostructures and nanostructures for IR and THz spectral ranges. We use a special MBE design set for the epitaxial layer growth on (013) GaAs substrates with ZnTe and CdTe buffer layers up to 3” in diameter with the precise ellipsometric monitoring in situ . The growth of MCT alloy heterostructures with the optimal composition distribution throughout the thickness allows for the realization of different types of many-layered heterostructures and quantum wells to prepare the material for fabricating single- or dual-band IR and THz detectors. We also present the two-color broad-band bolometric detectors based on the epitaxial MCT layers that are sensitive in 150–300-GHz subterahertz and infrared ranges from 3 to 10 μm, which operate at the ambient or liquid nitrogen temperatures as photoconductors, as well as the detectors based on planar HgTe quantum wells. The design and dimensions of THz detector antennas are optimized for reasonable detector sensitivity values. A special diffraction limited optical system for the detector testing was designed and manufactured. We represent here the THz images of objects hidden behind a plasterboard or foam plastic packaging, obtained at the radiation frequencies of 70, 140, and 275 GHz, respectively.

Fast-Response Superconducting Titanium Bolometric Detectors

High time resolution optical/infrared (IR) astronomy will require fast response detectors. In order to meet such requirement, cryogenic optical/IR detectors, such as superconducting tunnel junctions and transition-edge sensors, are under development. Of these cryogenic detectors, superconducting titanium (Ti) bolometric detectors, with a transition temperature of around 300 mK, based on the electron-phonon decoupling mechanism, are promising in fast response. In this paper, we report on the characterization of electro-thermal properties of a small-size (1 μm × 1 μm × 37 nm) superconducting Ti detector. The low-frequency noise of Ti film was fitted by empirical Hooge model. A discrepancy between the Hooge constant of the Ti film and that of normal metals shows disorder in the Ti film. Thermal conductance was extracted via measured current-voltage curves at different bath temperatures. The time constant was calculated as tens of nanoseconds, which was faster than expected. The fast response potentially enables the high-speed optical/IR astronomical observations. Detailed experimental and analytical results are also presented.

Resolution enhancement with light/heat decorrelation in CUPID-0 bolometric detector

The CUPID-0 experiment searches for neutrinoless double beta decay using the first array of enriched Zn82Se scintillating bolometers with double (heat and light) read-out. To further enhance the CUPID-0 detector performances, the heat-light correlation has been exploited to improve the energy resolution. Different decorrelation algorithms have been studied and the best result is the average reduction of the full width at half maximum (FWHM) energy resolution to (90.5±0.6) % of its original value, corresponding to a change from FWHM=(20.7±0.5) keV to FWHM=(18.7±0.5) keV at the 2615 keV γ line.

CUPID-0: A double-readout cryogenic detector for Double Beta Decay search

CUPID-0 is the first large mass neutrino-less double beta decay (0νββ) experiment based on cryogenic calorimeters with dual read-out of light and heat for background rejection. The detector assembly, consisting of 26 ZnSe crystals, 2 natural and 24 enriched at 95% in 82Se, all coupled with bolometric light detectors, has been constructed respecting very strict protocols and procedures, from the material selection during crystal growth to the new and innovative detector framework, in the attempt to achieve the best performance of the array. The successful construction of the detector lead to promising preliminary results, here presented. The array is in fact taking data underground at LNGS (Italy) since March 2017 and the particle identification, enabled by the light read-out, provides an unprecedented background level, for cryogenic calorimeters, of only 3.2 countskeV−1t−1yr−1 in the region of interest of the 0νββ search for 82Se, namely around 3 MeV.

Improved temperature coefficient of resistance in La1-xCaxMnO3:Ag0.2 (0.25 ≤ x≤ 0.33) ceramics prepared by sol–gel method

A series of La1−xCaxMnO3:Ag0.2 (0.25 ≤ x ≤ 0.33) polycrystalline ceramic materials were prepared by sol–gel method using methanol as solvent. X-ray diffraction analysis showed that all samples consisted of pure perovskite structurewith no second phase. The grain size and morphology of the samples were studied by scanning electron microscopy. The results showed the samples with good crystallinity, large grain size, and high density. X-ray photoelectron spectroscopy measurement results shows that Ag exists in manganese oxides in two forms (Ag and Ag+). The resistivity temperature curves showed that all samples exhibited a sharp metal–insulator transition. At x = 0.28, the temperature coefficient of resistance was 78.8%·K−1. The magnetization-temperature curves also showed a sharp ferromagnetism–paramagnetism transition, and the Curie temperature increased gradually. These ceramics act as promising candidates for application in infrared and bolometric detectors.

Cryogenic light detectors with enhanced performance for rare event physics

We have developed and tested a new way of coupling bolometric light detectors to scintillating crystal bolometers based upon simply resting the light detector on the crystal surface, held in position only by gravity. This straightforward mounting results in three important improvements: (1) it decreases the amount of non-active materials needed to assemble the detector, (2) it substantially increases the light collection efficiency by minimizing the light losses induced by the mounting structure, and (3) it enhances the thermal signal induced in the light detector thanks to the extremely weak thermal link to the thermal bath. We tested this new technique with a 16 cm$^2$ Ge light detector with thermistor readout sitting on the surface of a large TeO$_2$ bolometer. The light collection efficiency was increased by greater than 50\% compared to previously tested alternative mountings. We obtained a baseline energy resolution on the light detector of 20~eV RMS that, together with increased light collection, enabled us to obtain the best $\alpha$ vs $\beta/\gamma$ discrimination ever obtained with massive TeO$_2$ crystals. At the same time we achieved rise and decay times of 0.8 and 1.6 ms, respectively. This superb performance meets all of the requirements for the CUPID (CUORE Upgrade with Particle IDentification) experiment, which is a 1-ton scintillating bolometer follow up to CUORE.

Graphene Aerogel Based Bolometer for Ultrasensitive Sensing from Ultraviolet to Far-Infrared.

This work uncovers that free-standing partly reduced graphene aerogel (PRGA) films in vacuum exhibit extraordinarily bolometric responses. This high performance is mainly attributed to four structure characteristics: extremely low thermal conductivity (6.0-0.6 mW·m-1·K-1 from 295 to 10 K), high porosity, ultralow density (4 mg·cm-3), and abundant functional groups (resulting in tunable band gap). Under infrared radiation (peaked at 5.8-9.7 μm), the PRGA film can detect a temperature change of 0.2, 1.0, and 3.0 K of a target at 3, 25, and 54 cm distance. Even through a quartz window (transmissivity of ∼0.98 in the range of 2-4 μm), it can still successfully detect a temperature change of 0.6 and 5.8 K of a target at 3 and 28 cm distance. At room temperature, a laser power as low as 7.5 μW from a 405 nm laser and 5.9 μW from a 1550 nm laser can be detected. The detecting sensitivity to the 1550 nm laser is further increased by 3-fold when the sensor temperature was reduced from 295 K to 12 K. PRGA films are demonstrated to be a promising ultrasensitive bolometric detector, especially at low temperatures.

QUBIC: Exploring the Primordial Universe with the Q&U Bolometric Interferometer

In this paper, we describe QUBIC, an experiment that will observe the polarized microwave sky with a novel approach, which combines the sensitivity of state-of-the-art bolometric detectors with the systematic effects control typical of interferometers. QUBIC’s unique features are the so-called “self-calibration”, a technique that allows us to clean the measured data from instrumental effects, and its spectral imaging power, i.e., the ability to separate the signal into various sub-bands within each frequency band. QUBIC will observe the sky in two main frequency bands: 150 GHz and 220 GHz. A technological demonstrator is currently under testing and will be deployed in Argentina during 2019, while the final instrument is expected to be installed during 2020.

Towards a physical model for energy deposition via cosmic rays into sub-K bolometric detectors

Cosmology space missions have been known to be particularly sensitive to systematic effects arising from the interaction between cosmic rays and highly sensitive detectors below 200 mK. To remove this signal, one must first understand the deposition and dissipation of energy into these detectors. Using a well-known NTD germanium composite bolometer, we simulate the effect of cosmic rays using a radioactive source in the laboratory. Through analysis of experimental data, we find that the glitch signal shape is a function of incoming particle position, as well as the incoming particle energy. We report also on nonlinear effects in the fit, in order to lay the groundwork towards a new physical model for this energy propagation in the bolometer.

IR and THz Bolometric Detectors with Absorbers Characterized by Frequency Dispersion of Conductivity

Application of thin metal absorbers allows one to significantly increase the absorption coefficient and sensitivity of matrix THz microbolometric detectors. It is shown that absorbers characterized by frequency dispersion of conductivity, in contrast to conventional nondispersive absorbers, can provide almost total IR absorption retaining high sensitivity in the THz range.

Enhancing performance of graphene-based bolometers at 1 THz

The detection in the THz band is significant due to practical importance in various fields requiring high sensitivity, detection accuracy, and cost reduction. The structures based on graphene / superconductor cause a significant increase in the supercurrent thanks to the inherent and unique properties of graphene, such as high mobility and density of the carriers in the tunneling process. In the meantime, due to its flexibility in controlling performance and compatibility with large-scale integration, the field effect transistor has been transformed to one of the best options for the implementation of tunabe THz detectors. Therefore, in this study, a graphene Bolometer detector based on a field effect transistor is proposed. The influence of various parameters such as temperature and gate voltage on the V-I characteristic was investigated. Thermal conductivity, equivalent noise power and coupling radiated power were evaluated. The calculations indicate high precision of low noise and optimal response to temperature variations.

The EBEX Balloon-borne Experiment—Gondola, Attitude Control, and Control Software

Abstract The E and B Experiment (EBEX) was a long-duration balloon-borne instrument designed to measure the polarization of the cosmic microwave background (CMB) radiation. EBEX was the first balloon-borne instrument to implement a kilopixel array of transition edge sensor (TES) bolometric detectors and the first CMB experiment to use the digital version of the frequency domain multiplexing system for readout of the TES array. The scan strategy relied on 40 s peak-to-peak constant-velocity azimuthal scans. We discuss the unique demands on the design and operation of the payload that resulted from these new technologies and the scan strategy. We describe the solutions implemented, including the development of a power system designed to provide a total of at least 2.3 kW, a cooling system to dissipate 590 W consumed by the detectors’ readout system, software to manage and handle the data of the kilopixel array, and specialized attitude reconstruction software. We present flight performance data showing faultless management of the TES array, adequate powering and cooling of the readout electronics, and constraint of attitude reconstruction errors such that the spurious B-modes they induced were less than 10% of the CMB B-mode power spectrum with r = 0.05.

The EBEX Balloon-borne Experiment—Optics, Receiver, and Polarimetry

Abstract The E and B Experiment (EBEX) was a long-duration balloon-borne cosmic microwave background (CMB) polarimeter that flew over Antarctica in 2012. We describe the experiment’s optical system, receiver, and polarimetric approach and report on their in-flight performance. EBEX had three frequency bands centered on 150, 250, and 410 GHz. To make efficient use of limited mass and space, we designed a 115 cm2 sr high-throughput optical system that had two ambient temperature mirrors and four antireflection-coated polyethylene lenses per focal plane. All frequency bands shared the same optical train. Polarimetry was achieved with a continuously rotating achromatic half-wave plate (AHWP) that was levitated with a superconducting magnetic bearing (SMB). This is the first use of an SMB in astrophysics. Rotation stability was 0.45% over a period of 10 hr, and angular position accuracy was 0.°01. The measured modulation efficiency was above 90% for all bands. To our knowledge the 109% fractional bandwidth of the AHWP was the broadest implemented to date. The receiver, composed of one lens and the AHWP at a temperature of 4 K, the polarizing grid and other lenses at 1 K, and the two focal planes at 0.25 K, performed according to specifications, giving focal plane temperature stability with a fluctuation power spectrum that had a 1/f knee at 2 mHz. EBEX was the first balloon-borne instrument to implement technologies characteristic of modern CMB polarimeters, including high-throughput optical systems, and large arrays of transition edge sensor bolometric detectors with multiplexed readouts.

A Path to High-Efficiency Optical Coupling for HIRMES

The high-resolution mid-infrared spectrometer (HIRMES) under development for Stratospheric Observatory for Infrared Astronomy is an instrument operating in the 25–122 μm spectral range with a spectral resolution R = Δλ/λ ~ 100,000 and has two absorber-coupled transition edge sensor bolometric detector focal planes. We have developed novel NbTiN low-stress absorber coatings which have the required optical impedance across the HIRMES operating band. The low intrinsic stress of these coatings allow for a peak-to-valley corrugation amplitude < 5 μm of the 450 nm thick, 1.4 mm × 1.7 mm detector pixels. Furthermore, these coatings have a superconducting transition temperature ~ 10 K, which allows them to simultaneously serve as an absorber in the desired signal band and a rejection filter at long wavelengths. This attribute makes them especially attractive for ultrasensitive absorber-coupled bolometric detector applications, because it helps in controlling the optical loading from out-of-band radiation. We also discuss a novel method for integrating a wedged-reflective absorber termination to the detector array.

CUPID-0: the first array of enriched scintillating bolometers for 0nu beta beta decay investigations

The CUPID-0 detector hosted at the Laboratori Nazionali del Gran Sasso, Italy, is the first large array of enriched scintillating cryogenic detectors for the investigation of ^{82}Se neutrinoless double-beta decay (0nu beta beta ). CUPID-0 aims at measuring a background index in the region of interest (RoI) for 0nu beta beta at the level of 10^{-3} counts/(keV kg years), the lowest value ever measured using cryogenic detectors. CUPID-0 operates an array of Zn^{82}Se scintillating bolometers coupled with bolometric light detectors, with a state of the art technology for background suppression and thorough protocols and procedures for the detector preparation and construction. In this paper, the different phases of the detector design and construction will be presented, from the material selection (for the absorber production) to the new and innovative detector structure. The successful construction of the detector lead to promising preliminary detector performance which is discussed here.

Commercialization of Micro-fabrication of Antenna-Coupled Transition Edge Sensor Bolometer Detectors for Studies of the Cosmic Microwave Background

We report on the development of commercially fabricated multi-chroic antenna coupled Transition Edge Sensor (TES) bolometer arrays for Cosmic Microwave Background (CMB) polarimetry experiments. CMB polarimetry experiments have deployed instruments in stages. Stage-II experiments deployed with O(1,000) detectors and reported successful detection of B-mode (divergent free) polarization pattern in the CMB. Stage-III experiments have recently started observing with O(10,000) detectors with wider frequency coverage. A concept for a Stage-IV experiment, CMB-S4, is emerging to make a definitive measurement of CMB polarization from the ground with O(400,000) detectors. The orders of magnitude increase in detector count for CMB-S4 requires a new approach in detector fabrication to increase fabrication throughput.and reduce cost. We report on collaborative efforts with two commercial micro-fabrication foundries to fabricate antenna coupled TES bolometer detectors. The detector design is based on the sinuous antenna coupled dichroic detector from the POLARBEAR-2 experiment. The TES bolometers showed the expected I-V response and the RF performance agrees with simulation. We will discuss the motivation, design consideration, fabrication processes, test results, and how industrial detector fabrication could be a path to fabricate hundreds of detector wafers for future CMB polarimetry experiments.

Characterisation of a new carbon nanotube detector coating for solar absolute radiometers

A new sprayable carbon nanotube coating for bolometric detectors aims to increase the absorptance compared to regular space qualified black paints. In collaboration with the National Institute of Standards and Technology (NIST), we have characterized the optical properties and mechanical and thermal stability of the carbon nanotube coating inside conical shaped cavity detectors.