Cryogenic Bolometers Research Articles

Offline data processing software for a Li2MoO4 bolometer demonstration experiment at China Jinping Underground Laboratory

A cryogenic scintillating bolometer demonstration experiment utilizing Li2MoO4 crystals is proposed for exploring neutrinoless double beta decay (0νββ) at China Jinping Underground Laboratory (CJPL). The hardware and software framework R&D for the entire detection system is currently in progress. In this study, we present a comprehensible offline data processing software designed for this project. The software facilitates event trigger and reconstruction by applying an optimal filter and Monte Carlo truth stream data generator. Based on the simulated stream data, a significant noise suppression and an increase on energy resolution are obtained, with an improvement of approximately 40% comparing to that estimated from the original pulse waveform.

First demonstration of 30 eVee ionization energy resolution with Ricochet germanium cryogenic bolometers

The future Ricochet experiment aims to search for new physics in the electroweak sector by measuring the Coherent Elastic Neutrino-Nucleus Scattering process from reactor antineutrinos with high precision down to the sub-100 eV nuclear recoil energy range. While the Ricochet collaboration is currently building the experimental setup at the reactor site, it is also finalizing the cryogenic detector arrays that will be integrated into the cryostat at the Institut Laue Langevin in early 2024. In this paper, we report on recent progress from the Ge cryogenic detector technology, called the CryoCube. More specifically, we present the first demonstration of a 30 eVee (electron equivalent) baseline ionization resolution (RMS) achieved with an early design of the detector assembly and its dedicated High Electron Mobility Transistor (HEMT) based front-end electronics with a total input capacitance of about 40 pF. This represents an order of magnitude improvement over the best ionization resolutions obtained on similar phonon-and-ionization germanium cryogenic detectors from the EDELWEISS and SuperCDMS dark matter experiments, and a factor of three improvement compared to the first fully-cryogenic HEMT-based preamplifier coupled to a CDMS-II germanium detector with a total input capacitance of 250 pF. Additionally, we discuss the implications of these results in the context of the future Ricochet experiment and its expected background mitigation performance.

An implementation of a channelizer based on a Goertzel Filter Bank for the read-out of cryogenic sensors

In this work we present an application of the Goertzel Filter for the channelization of multi-tonal signals, typically used for the read-out of cryogenic sensors which are multiplexed in the frequency domain (FDM), by means of Microwave Superconducting Quantum Interference Device (SQUID) Multiplexer (μMUX). We demonstrate how implementing a bank of many of these filters, can be used to perform a channelization of the multi-tonal input signal to retrieve the data added by the sensors. We show how this approach can be implemented in a resource-efficient manner in a Field Programmable Gate Array (FPGA) within the state-of-the-art, which allows great scalability for reading thousands of sensors; as is required by Radio Telescopes in Cosmic Microwave Background Radiation (CMB) surveys using cryogenic bolometers, particles detection like Neutrino mass estimation using cryogenic calorimeters or Quantum Computing.

ZnO-based scintillating bolometers: new prospects to study double beta decay of 64Zn

The first detailed study on the performance of a ZnO-based cryogenic scintillating bolometer as a detector to search for rare processes in zinc isotopes was carried out. A 7.2 g ZnO low-temperature detector, containing more than 80% of zinc in its mass, exhibits good energy resolution of baseline noise 1.0–2.7 keV FWHM at various working temperatures resulting in a low-energy threshold for the experiment, 2.0–6.0 keV. The light yield for β/γ events was measured as 1.5(3) keV/MeV, while it varies for α particles in the range of 0.2–3.0 keV/MeV. The detector demonstrates an effective identification of β/γ events from α events using time-properties of only heat signals. The radiopurity of the ZnO crystal was evaluated using the Inductively Coupled Plasma Mass Spectrometry, an ultra-low-background High Purity Ge γ-spectrometer, and bolometric measurements. Only limits were set at the level of 𝒪(1–100) mBq/kg on activities of 40K, 137Cs and daughter nuclides from the U/Th natural decay chains. The total internal α-activity was measured as 22(2) mBq/kg, with a major contribution caused by 6(1) mBq/kg of 232Th and 12(2) mBq/kg of 234U. Limits on double beta decay (DBD) processes in ^64Zn and 70Zn isotopes were set on the level of 𝒪(1017–1018) yr for various decay modes, profiting from 271 h of acquired background data in the above-ground lab. This study shows a good potential for ZnO-based scintillating bolometers to search for DBD processes of Zn isotopes, especially in 64Zn, with the most prominent spectral features at ∼ 10–20 keV, like the two-neutrino double electron capture. A 10 kg-scale experiment can reach the experimental sensitivity at the level of 𝒪(1024) yr.

Quantum state-resolved methane scattering from Ni(111) and NiO(111) by bolometer infrared laser tagging: The effect of surface oxidation.

We describe a novel ultrahigh vacuum state-to-state molecule/surface scattering apparatus with quantum state preparation of the incident molecular beam and angle-resolved quantum state detection of the scattered molecules. State-resolved detection is accomplished using a tunable mid-infrared laser source combined with a cryogenic bolometer detector and is applicable to any molecule with an infrared-active vibrational transition. Results on rotationally inelastic scattering of CH4 methane from a Ni(111) surface and NiO(111)/Ni(111) oxide film, obtained by the new apparatus, are presented. Molecules scattering from the oxidized surface, compared to those scattering from the bare nickel surface, are more highly excited rotationally and scatter into a broader distribution of angles. The internal alignment of molecular rotation is in addition found to be stronger in molecules scattering from the bare surface. Furthermore, the maxima of the state-resolved angular distributions shift toward and away from surface normal with increasing rotational quantum number J for the oxidized and bare surface, respectively. Finally, the rotational state populations produced in scattering from the oxidized surface are well-described by a Boltzmann distribution, while those produced in scattering from the bare surface exhibit large deviations from their best-fit Boltzmann distributions. These results point toward a marked enhancement in molecule-surface collisional energy exchange induced by oxidation of the nickel surface.

Effect of post-growth anneals in oxygen-containing atmosphere on the microhardness of single crystal calcium molybdate CaMoO4

Single crystal calcium molybdate CaMoO4 is a well-known material. However the interest to CaMoO4 has recently grown due to a number of its important applications including as a working material in cryogenic scintillation bolometers. CaMoO4 single crystals acquire blue color during growth due to the presence of color-center type defect centers which are unacceptable for optical applications. Color can be eliminated through annealing in an oxygen containing atmosphere, following which required optical components can be produced from the single crystals by mechanical treatment (cutting, polishing etc.). Therefore assessment of the mechanical properties of these single crystal materials is an important task for the optimal solution of issues occurring in the fabrication of optical components and their further practical application. There are but scarce data on the mechanical properties of CaMoO4, and the available ones have been reported without allowance for anisotropy. There is a significant scatter of data on the Mohs hardness of the single crystals, ranging from 3.3 to 6 in different publications. In this work we present data on calcium molybdate single crystals in the initial state and after high-temperature anneals of different durations in an oxygen containing atmosphere. We show that long-term annealing leads to decolorization of the crystals. Calcium molybdate single crystals prove to be quite brittle: the brittleness index Zp of the crystals in the initial state is the highest and equals 5, while annealing reduces the brittleness index to 4. The Palmqvist toughness factors S have been calculated The limit indentation destruction loads Flim have been determined and annealing in an oxygen containing atmosphere has been shown to increase Flim by 2.5 times for the Z cut and by 10 times for the X cut. The microhardness of the crystals has been shown to exhibit a II type anisotropy: the microhardness of all the specimens was higher for the Z cut than for the X cut. The microhardness anisotropy coefficients KH of the specimens have been evaluated. The bond ionicity degree I has been calculated on the basis of the experimentally measured microhardness.

Secular equilibrium assessment in a CaWO4 target crystal from the dark matter experiment CRESST using Bayesian likelihood normalisation

CRESST is a leading direct detection sub-GeVc−2 dark matter experiment. During its second phase, cryogenic bolometers were used to detect nuclear recoils off the CaWO4 target crystal nuclei. The previously established electromagnetic background model relies on Secular Equilibrium (SE) assumptions. In this work, a validation of SE is attempted by comparing two likelihood-based normalisation results using a recently developed spectral template normalisation method based on Bayesian likelihood. Albeit we find deviations from SE in some cases we conclude that these deviations are artefacts of the fit and that the assumptions of SE is physically meaningful.

Primary calibration of photodiodes with monochromatic X‐ray beams using an electrical‐substitution radiometer

AbstractThe electrical‐substitution cryogenic detector BOLometer for Use in the range of X‐rays (BOLUX), which was developed some years ago at CEA/DAM, has been set up and restarted now at LNHB. It has been used for the primary measurement of the intensity (total energy per unit time) of monochromatic synchrotron beams in the energy range from 3 to 30 keV. These well‐determined photon beams have been employed for the efficiency calibration of two photodiodes in terms of current induced per unit optical power at different photon energies. In a final step, we explored the possibility to use these primary‐calibrated photodiodes to determine the efficiency curve of an energy‐dispersive spectrometer based on a semiconductor detector (Silicon Drift Detector) using less intense monochromatic photon fluxes. The characteristics of the radiometer BOLUX and its principle of operation are described, and the measurements carried out at the synchrotron beamline are presented, including the determination of the beams' intensities, the direct calibration of photodiodes with respect to BOLUX and the use of one of those photodiodes as a standard transfer for the calibration of the SDD.

An analytical model for electronic noise in a cryogenic bolometer detector readout circuit

This paper presents an analytical model to quantify the measured noise in a cryogenic bolometer readout circuit. The model includes the contributions from the bias resistors and sensor resistors, voltage and current noise of amplifier, and cable capacitance. The model parameters are empirically estimated using frequency domain analysis of the measured noise data of indigenously developed Neutron Transmutation Doped (NTD) Ge sensors. The model is shown to describe noise data for NTD Ge sensorsover a wide range of resistances corresponding to temperatures in the range 20–70 mK.Relative contributions of different components are discussed and it is shown that the contribution to the overall noise from the differential amplifier at 300 K is the dominant source. It is observed that the amplifier flicker noise is significantly lower than that specified in the amplifier datasheet. The present study also indicates that a desirable value of resistance of NTD sensor (R NTD) from noise considerations is ≲ 1 GΩ at ∼ 20 mK.

Performance of the Li6Eu(BO3)3 crystal as a scintillating bolometer for studies of rare processes

In this article we report on a detailed study of the internal radioactive and chemical contamination of the Li6Eu(BO3)3 scintillating crystal operated as a cryogenic scintillating bolometer over 359 h. The excellent discrimination power of the detector allows to distinguish effectively beta/gamma events from alpha events. Whilst a weak activity of daughter nuclides from U/Th chains at the level few mBq/kg was observed, this crystal was found to be significantly contaminated by 147Sm, an alpha-active nuclide, at the level of about 0.5 Bq/kg. The light yield for β/γ events was determined to be 7.4(6) keV/MeV. The light yield and quenching factor for alpha particles vary in the range of (0.5–1.2) keV/MeV and (0.07–0.17), respectively, due to energy dependence of the emitted scintillating light in the energy interval (2.0–7.0) MeV. The integral luminescence intensity of the Li6Eu(BO3)3 crystal increases by more than four times only at low temperatures, below 80 K. Therefore, the Li6Eu(BO3)3-based cryogenic scintillating bolometers can be attractive detectors for direct neutron flux monitoring, to search for rare alpha decays or solar axions.

Study of a Coherent Elastic Neutrino-Nucleus Scattering experiment at a reactor with a PbWO4-based bolometer

The first observation of the Coherent Elastic Neutrino-Nucleus Scattering (CEνNS) by the COHERNET experiment using accelerator neutrinos rendered opportunities for abundant scientific and technological applications. To study the CEνNS process precisely, a project using cryogenic bolometer technology with lead tungstate (PbWO4) as a detector candidate and a nuclear reactor as a neutrino source is proposed. By taking a typical reactor, the China Taishan Nuclear Power Plant, as a reference, a flux of 6.7×1016 m−2 s−1 with energy below 10 MeV can be realized at an experimental site located approximately ∼30 meters away from one of the 4.6 GWth thermal power Taishan reactor cores. The specific heat of PbWO4, which is an important detector research and design parameter, was measured for the first time at O(500) mK, and the results were found to be consistent with the prediction of Debye model. The phonon-only response of a PbWO4 crystal to the energy deposits at very low temperatures may offer high sensitivity to the small nucleus recoil CEνNS signal. A configuration using a one-gram PbWO4 cube as a detector unit working at a temperature of O(10) mK, together with novel phonon sensor technology sensitive to nucleus recoil energy as low as O(10) eV, is hypothesized as the ideal experiment benchmark. Consequently, a signal rate of around 200 reactor neutrino coherent scattering events can be expected per day with a one-kilogram PbWO4 detector volume, against ∼20 background counts in the optimized signal region.

Phonon and Charge Signals from IR and X Excitation in the SELENDIS Ge Cryogenic Detector

The aim of the SELENDIS project within the EDELWEISS collaboration is to observe single $e^- h^+$ pairs in lightweight (3.3 g) cryogenic germanium bolometers with charge and phonon readout at biases up to $\sim 100$ V. These devices are ideal to characterize in detail the mechanism of charge creation and collection in cryogenic germanium detectors. Electron-hole pairs are produced in the bulk of the detector either by the injection of pulsed IR laser or by neutron activation of germanium inducing the K, L and M lines from $^{71}$Ge electron capture decays. Low-energy laser pulses are also used to probe the single $e^- h^+$ pair sensitivity of Ge bolometers. Preliminary results are used to compare these two modes of charge creation, an important step toward a detailed characterization of Ge bolometers for their use in sub-MeV Dark Matter (DM) searches.

Generalized electrical substitution methods and detectors for absolute optical power measurements

We have developed generalized methods for electrical substitution optical measurements, as well as cryogenic detectors which can be used to implement them. The new methods detailed here enable measurement of arbitrary periodic waveforms by an electrical substitution radiometer (ESR), which means that spectral and dynamic optical power can be absolutely calibrated directly by a primary standard detector. Cryogenic ESRs are not often used directly by researchers for optical calibrations due to their slow response times and cumbersome operation. We describe two types of ESRs with fast response times, including newly developed cryogenic bolometers with carbon nanotube absorbers, which are manufacturable by standard microfabrication techniques. These detectors have response times near 10 ms, spectral coverage from the ultraviolet to far-infrared, and are ideal for use with generalized electrical substitution. In our first tests of the generalized electrical substitution method with FTS, we have achieved uncertainty in detector response of 0.13% (k = 1) and total measurement uncertainty of 1.1% (k = 1) in the mid-infrared for spectral detector responsivity calibrations. The generalized method and fast detectors greatly expand the range of optical power calibrations which can be made using a wideband primary standard detector, which can shorten calibration chains and improve uncertainties.

Expected sensitivity to 128Te neutrinoless double beta decay with the CUORE TeO2 cryogenic bolometers

The CUORE experiment is a ton-scale array of hbox {TeO}_2 cryogenic bolometers located at the underground Laboratori Nazionali del Gran Sasso of Istituto Nazionale di Fisica Nucleare (INFN), in Italy. The CUORE detector consists of 988 crystals operated as source and detector at a base temperature of sim 10 mK. Such cryogenic temperature is reached and maintained by means of a custom built cryogen-free dilution cryostat, designed with the aim of minimizing the vibrational noise and the environmental radioactivity. The primary goal of CUORE is the search for neutrinoless double beta decay of ^{130}hbox {Te}, but thanks to its large target mass and ultra-low background it is suitable for the study of other rare processes as well, such as the neutrinoless double beta decay of ^{128}hbox {Te}. This tellurium isotope is an attractive candidate for the search of this process, due to its high natural isotopic abundance of 31.75%. The transition energy at (866.7 ± 0.7) keV lies in a highly populated region of the energy spectrum, dominated by the contribution of the two-neutrino double beta decay of ^{130}hbox {Te}. As the first ton-scale infrastructure operating cryogenic hbox {TeO}_2 bolometers in stable conditions, CUORE is able to achieve a factor >10 higher sensitivity to the neutrinoless double beta decay of this isotope with respect to past direct experiments.

Flux ramp modulation based hybrid microwave SQUID multiplexer

We present a hybrid microwave superconducting quantum interference device (SQUID) multiplexer that combines two frequency-division multiplexing techniques to allow multiplexing a given number of cryogenic detectors with only a fraction of frequency encoding resonators. Similar to conventional microwave SQUID multiplexing, our multiplexer relies on inductively coupling non-hysteretic, unshunted rf-SQUIDs to superconducting microwave resonators as well as applying flux ramp modulation for output signal linearization. However, instead of utilizing one resonator per SQUID, we couple multiple SQUIDs to a common readout resonator and encode the SQUID input signals in sidebands of the microwave carrier by varying the flux ramp modulation frequency for each SQUID. We prove the suitability of our approach using a prototype device and argue by means of fundamental information theory that our approach is particularly suited for reading out large cryogenic bolometer arrays.

Bolometric Double Beta Decay Experiments: Review and Prospects

This review aims to cover the history and recent developments on cryogenic bolometers for neutrinoless double beta decay (0ν2β) searches. A 0ν2β decay observation would confirm the total lepton charge non-conservation, which is related to a global U(1)LC symmetry. This discovery would also provide essential information on neutrino masses and nature, opening the door to new physics beyond the Standard Model. The bolometric technology shows good prospects for future ton-scale experiments that aim to fully investigate the inverted ordering region of neutrino masses. The big advantage of bolometers is the high energy resolution and the possibility of particle identification, as well as various methods of additional background rejection. The CUORE experiment has proved the feasibility of ton-scale cryogenic experiments, setting the most stringent limit on 130Te 0ν2β decay. Two CUPID demonstrators (CUPID-0 and CUPID-Mo) have set the most stringent limits on 82Se and 100Mo isotopes, respectively, with compatibly low exposures. Several experiments are developing new methods to improve the background in the region of interest with bolometric detectors. CUPID and AMoRE experiments aim to cover the inverted hierarchy region, using scintillating bolometers with hundreds of kg of 100Mo. We review all of these efforts here, with a focus on the different types of radioactive background and the measures put in place to mitigate them.

A new limit on the resonant absorption of solar axions obtained via 169Tm-containing bolometer

A newly developed experimental technique based on 169Tm-containing cryogenic bolometer detector was employed in order to perform the search for solar axions. The inclusion of target material into the active detector volume allowed for significant increase in sensitivity to axion parameters. A short 6.6 days measurement campaign with 8.18 g detector crystal yielded the following limits on axion couplings: and . The achieved results demonstrate high scalability potential of presented experimental approach.

Novel technique for the study of pileup events in cryogenic bolometers

Precise characterization of detector time resolution is of crucial importance for next-generation cryogenic-bolometer experiments searching for neutrinoless double-beta decay, such as CUPID, in order to reject background due to pile-up of two-neutrino double-beta decay events. In this paper, we describe a technique developed to study the pile-up rejection capability of cryogenic bolometers. Our approach, which consists of producing controlled pile-up events with a programmable waveform generator, has the benefit that we can reliably and reproducibly control the time separation and relative energy of the individual components of the generated pile-up events. The resulting data allow us to optimize and benchmark analysis strategies to discriminate between individual and pile-up pulses. We describe a test of this technique performed with a small array of detectors at the Laboratori Nazionali del Gran Sasso, in Italy; we obtain a 90% rejection efficiency against pulser-generated pile-up events with rise time of ~15ms down to time separation between the individual events of about 2ms.

Li2100deplMoO4 crystals grown by low-thermal-gradient Czochralski technique

For the first time, Li2MoO4crystals depleted in molybdenum-100 (100Mo) isotope were grown by Czochralski technique under low thermal gradient conditions (LTG Cz) that made it possible to obtain large crystals of given geometry and required quality. Depleted lithium molybdate crystals Li2deplMoO4 are excellent candidates for creating cryogenic scintillating bolometers with weight of up to 0.3 kg. Such bolometers can be used to reduce the internal radiation background of detectors and to increase sensitivity in physics and astrophysics experiments for rare events search. The grown Li2100deplMoO4 crystal was compared with the crystal samples of natural and enriched in 100Mo isotope in regard of their response to pulsed X-ray irradiation and Raman spectra.

New limits on the resonant absorption of solar axions obtained with a ^mathbf {169}Tm-containing cryogenic detector

A search for resonant absorption of solar axions by ^{169}mathrm {Tm} nuclei was carried out. A newly developed approach involving low-background cryogenic bolometer based on mathrm {Tm}_{3} mathrm {Al}_{5} mathrm {O}_{12} crystal was used that allowed for significant improvement of sensitivity in comparison with previous ^{169}mathrm {Tm} based experiments. The measurements performed with 8.18 g crystal during 6.6 days exposure yielded the following limits on axion couplings: |g_{Agamma } (g_{AN}^0 + g_{AN}^3) le 1.44 times 10^{-14},{{mathrm{GeV}}^{-1}} and |g_{Ae} (g_{AN}^0 + g_{AN}^3) le 2.81 times 10^{-16}.