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![The proportions of normal matter, DM and dark energy in the Universe as measured by the Planck spacecraft [22].](publication/360185205/figure/fig1/AS:11431281115585476@1675015401503/The-proportions-of-normal-matter-DM-and-dark-energy-in-the-Universe-as-measured-by-the.png)
The proportions of normal matter, DM and dark energy in the Universe as measured by the Planck spacecraft [22].
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Superconducting detectors have become an important tool in experimental astroparticle physics, which seeks to provide a fundamental understanding of the Universe. In particular, such detectors have demonstrated excellent potential in two challenging research areas involving rare event search experiments, namely, the direct detection of dark matter...
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... most abundant component, at 68.9%, is called dark energy, which is uniformly spread throughout the Universe and is responsible for the repulsive force that is accelerating the expansion of the Universe. The fractional contents of normal matter, DM, and dark energy in the Universe are illustrated in figure 1. ...
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... higher the input energy is, the more quasiparticles will be generated. These excess quasiparticles change the kinetic inductance of a microwave resonance circuit, which can be measured as a shift in the amplitude and phase of the resonance, as shown in figure 10 [164]. This is the basic working principle of a KID. ...
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... there is no single detection method that can cover such a wide range, a detector should be optimized for a rather narrow mass range. In figure 13, we provide a list of detection methods suitable for the direct detection of DM of different mass ranges as well as for 0νββ search experiments that share common detection schemes with the direct DM search experiments. ...
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... on the type of absorber material, this energy deposition can result in ionization (charge), scintillation (light) and/or heat (phonon) signals. The bottom right of figure 13 shows six different categories of target materials that allow single-or dual-channel measurements. Dual-channel measurements have the advantage of enhanced background rejection via PID, as explained below. ...
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... heat-scintillation, and ionization-scintillation), the ratio of the amplitudes of the two channels differs depending upon the type of particle that primarily receives energy upon interaction with a DM particle. For instance, in the heat-scintillation case, an energetic ion that results from NR due to DM-nucleon scattering generates much less scintillation light than electrons or photons (e/γ) of the same energy, as illustrated by figure 14. This effect is known as quenching of a scintillating material [198]. ...
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... instance, a tunable resonator composed of a microwave cavity or a superconducting lumped circuit has been developed to detect QCD axions, a strong DM candidate, through their conversion to photons under a high magnetic field (Primakoff conversion) [121]. This type of detection method, along with several ongoing projects, is illustrated at the bottom left of figure 13. Note that other promising technologies exist [39] that are not listed here, some of which we briefly discuss later in the section. ...
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... each successive phase, the CDMS detector design also continued to evolve. However, the core measurement scheme remained the same: the detector consists of multiple detector modules operating at cryogenic temperatures, each module is equipped with a sizeable disk-shaped Ge or Si crystal as the target for DM-normal matter interactions, and the temperature and ionization signals induced by an energy input in the target crystal are simultaneously measured by a temperature sensor and a field effect transistor (FET) amplifier, respectively, as illustrated in figure 13. The dual-channel measurement makes it possible to distinguish NR signals from electron recoil signals, thus significantly improving the detector sensitivity to NR-like DM signals, as previously discussed (see figure 14). ...
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... the core measurement scheme remained the same: the detector consists of multiple detector modules operating at cryogenic temperatures, each module is equipped with a sizeable disk-shaped Ge or Si crystal as the target for DM-normal matter interactions, and the temperature and ionization signals induced by an energy input in the target crystal are simultaneously measured by a temperature sensor and a field effect transistor (FET) amplifier, respectively, as illustrated in figure 13. The dual-channel measurement makes it possible to distinguish NR signals from electron recoil signals, thus significantly improving the detector sensitivity to NR-like DM signals, as previously discussed (see figure 14). ...
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... temperature sensors in the CDMS detectors, except for that in one early generation called the Berkeley Large Ionization-and Phonon-mediated (BLIP) detector, which is based on NTD Ge sensors, consist of thousands of tiny W TESs spread over the surface of the target crystal in a hierarchical arrangement, a unique feature of CDMS's Z-sensitive ionization and phonon-mediated (ZIP) detector. More specifically, CDMS I ZIP contained 4 independent phonon channels, with each channel consisting of 37 cells and each cell consisting of 12 TES elements coupled to Al 'fins' or 12 quasiparticle-assisted ETF transition-edge sensors (QETs) as shown in figure 15(a). In total, there were 4 × 444 TES elements for each target crystal. ...
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... QETs of the CDMS I ZIP detector had a fill factor of nearly 100% near the QET coverage area (82% of the top surface); because the average distance between generated quasiparticles and the nearest TES was larger than the diffusion length of the quasiparticles, some quasiparticles were unable to reach a TES within the time constant of the TES. To solve this problem, the number of TESs per channel was increased from 12 to 28, and the length of the Al fins was decreased in the CDMS II ZIP detector as shown in figure 15(b). There were even more upgrades in the Super-CDMS detectors, as described below. ...
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... on the basic working principle of the CDMS I and II ZIP detectors, SuperCDMS has involved significant upgrades in its new interleaved Z-sensitive Ionization and Phonon sensors (iZIP) detector. In this new detector, phonon sensors are patterned on both sides of the crystal and interleaved with ionization electrode lines, as shown in figure 16. The phonon sensors on the top and bottom surfaces are separated into four channels in the SuperCDMS Soudan iZIP and six channels in the SuperCDMS SNOLAB iZIP, covering the entire top and bottom surfaces of the crystal. ...
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... Cryogenic Rare Event Search with Superconducting Thermometers (CRESST) is another multiinstitution direct DM search experiment that uses TESs as sensors of the DM-normal matter interaction. CRESST is known for its use of scintillating crystals equipped with phonon-photon channel detection, as shown in figure 13. The collaboration recently completed the operation of CRESST-III Phase 1 [204] and is in the preparation stage for CRESST-III Phase 2. ...
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... first CRESST experiment (CRESST-I) used four sapphire (Al 2 O 3 ) crystals (262 g each) as the target material for the detection of DM-nucleon scattering events [205]. Sapphire crystals were chosen because of their high Debye temperature [206], which can make the specific heat of the detector very Figure 17. Schematic diagram of the active thermal feedback scheme. ...
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... achieve this very low T c , an α-phase W film was electron beam evaporated on heated sapphire crystals in an ultrahigh vacuum environment [148]. For stable operation of the detector at the T c of the W film of ∼15 mK, an active thermal feedback scheme in which the base temperature of the cryostat was maintained at ∼6.5 mK and an additional heater integrated into the detector maintained the detector temperature at the T c [208] was adopted, as shown in figure 17. The heater also served as a means to calibrate the detector. ...
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... certain scintillating crystals, electron-and photoninduced signals show a different light yield than that due to heavy ions or neutrons, as shown in figure 14. Among several different scintillating crystals the CRESST collaboration tested, CaWO 4 showed the best performance at cryogenic temperatures. ...
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... several different scintillating crystals the CRESST collaboration tested, CaWO 4 showed the best performance at cryogenic temperatures. Based on this finding, they made significant changes in their detector design (CRESST-II): the sapphire crystals were replaced with CaWO 4 , and light detectors were added, as shown in figure 18. ...
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... this purpose, the mass of the CaWO 4 crystals was reduced to 24 g each (a factor of 10 reduction), significantly lowering the detector threshold to below 50 eV [216]. Moreover, the new modules were designed to employ crystal supporting rods composed of CaWO 4 , and each rod had a TES film, as shown in figure 19. This was to veto any events caused by the thermal signal propagating to the target crystal through its holding structure, which could explain the excess events in the acceptance region. ...
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... TESs, CDMS and CRESST have shown remarkable progress and promising results in direct DM detection covering the lowmass region of the DM parameter space. Expérience pour Figure 19. Schematic diagram of the CRESST-III detector module. ...
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... absorber selections, scintillating crystals are preferred because unwanted background signals can be discriminated through the simultaneous detection of light (scintillation) and heat (phonon) signals, as shown in figure 14. Furthermore, these materials have better thermal properties than noncrystalline materials. ...
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... axions and ALPs emerge as strong candidates for wavelike DM of sub-eV mass, many detection technologies have been developed to search for these hypothetical particles. One powerful approach is to detect excess electromagnetic (photon) signals of a certain frequency converted from axions or ALPs in a strong magnetic field, the so-called inverse Primakoff effect, as illustrated in figure 13. Since the possible mass range of wave-like DM spans orders of magnitude, different detection schemes are required depending on the target mass (frequency) of the DM. ...
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... current most sensitive axion detectors were developed based on the axion haloscope proposed by Sikivie [121]. As shown in figure 21, in an axion haloscope, a microwave cavity is adopted to detect photons produced via the inverse Primakoff effect. The detection sensitivity of the axion-photon conversion is enhanced when the resonant frequency of a microwave cavity matches the axion mass. ...
Citations
... Each crystal is surrounded by a 65-µm-thick Vikuiti enhanced specular reflector film (VM2000) [21,22] and is assembled into a module using NOSV-grade copper frames with high thermal conductivity and low radioactivity, as shown in Fig. 2 [23]. The MMC measures the rise in the crystal temperature caused by radiation absorption [24][25][26][27]. A detachable photon detector is installed at the top of the copper frame [28,29]. ...
AMoRE-II aims to search for neutrinoless double beta decay with an array of 423 Li$_2$$^{100}$MoO$_4$ crystals operating in the cryogenic system as the main phase of the Advanced Molybdenum-based Rare process Experiment (AMoRE). AMoRE has been planned to operate in three phases: AMoRE-pilot, AMoRE-I, and AMoRE-II. AMoRE-II is currently being installed at the Yemi Underground Laboratory, located approximately 1000 meters deep in Jeongseon, Korea. The goal of AMoRE-II is to reach up to $T^{0\nu\beta\beta}_{1/2}$ $\sim$ 6 $\times$ 10$^{26}$ years, corresponding to an effective Majorana mass of 15 - 29 meV, covering all the inverted mass hierarchy regions. To achieve this, the background level of the experimental configurations and possible background sources of gamma and beta events should be well understood. We have intensively performed Monte Carlo simulations using the GEANT4 toolkit in all the experimental configurations with potential sources. We report the estimated background level that meets the 10$^{-4}$counts/(keV$\cdot$kg$\cdot$yr) requirement for AMoRE-II in the region of interest (ROI) and show the projected half-life sensitivity based on the simulation study.
... Thermal calorimetric detection in milli-Kelvin (mK) temperatures has become an important measurement tool for experiments requiring high energy sensitivities (e.g., resolution and threshold) [13,14]. Another advantage of cryogenic detectors is the potential to incorporate an additional readout channels for charge or light detection when using a semiconductor or scintillator as the target material, respectively. ...
We present the development of a dual-detector system designed for investigating the spectral shape of forbidden non-unique beta decays. Two PbMoO4\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_4$$\end{document} scintillating crystals were carefully prepared for heat and light detection at milli-Kelvin (mK) temperatures. Notably, one crystal was synthesized using archaeological lead, while the other was composed of natural modern lead. The significance of employing two crystals lies in their identical dimensions and proximity, resulting in similar environmental background exposure. Their distinct internal radioactivities, particularly associated with 210\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{210}$$\end{document}Pb, introduce a distinguishing factor between the spectra measured in the two detectors. Our detection method includes achieving clear particle identification through the relative amplitudes of light and heat signals for both crystals. This report compares the electron-induced spectra within energy regions both below and above the endpoint of 210\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{210}$$\end{document}Bi beta decay. This comparative study provides valuable insights into an exact measurement of the 210\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{210}$$\end{document}Bi decay spectrum, forbidden non-unique beta decay.
... Superconducting materials are commonly used in low-temperature detectors and are necessary for various applications, including astrophysics [1], particle physics [2] and quantum electronics [3,4]. The discovery in 2006 of the superconductivity in heavily boron-doped crystalline silicon obtained by gas immersion laser doping (GILD) technique allowed the intensification of research work on this material [5]. ...
In this paper, we discuss the characterization of boron-doped silicon superconducting thin films with a thickness of 70 nm made on silicon-on-insulator substrates by ion implantation and ultra-violet nanosecond laser annealing under nitrogen at atmospheric pressure. Two different ion-implanted doses of boron of 1 × 10¹⁶ and 2.5 × 10¹⁶ cm⁻² at 3 keV were tested in the study. Single laser pulses with energy densities in the range of 0.3–1.1 J/cm² were applied to activate the boron species in the silicon. A transition from partially (monocrystalline) to fully-melted (polycrystalline) silicon is observed when increasing the laser energy density. The critical temperature (Tc) and the upper critical magnetic field (Bc2) were measured for different samples. A maximum Tc of 100 mK was obtained in the monocrystalline phase of the silicon just before the transition into the polycrystalline phase. An obvious impact of the doping level and laser annealing energy density on the Tc values was observed. Different morphological and physical characterizations such as transmission electron microscopy, X-ray photoelectron spectroscopy and secondary ion mass spectrometry were performed and analyzed in order to compare the samples.
... In recent decades, detectors operating at millikelvin temperatures, known as low-temperature detectors (LTDs), have become essential tools across various scientific fields. These detectors play a key role in studying fundamental questions in particle, nuclear, and astroparticle physics [1][2][3][4][5][6]. In particular, LTDs utilizing scintillating crystals as absorbers are actively used in rare-event search experiments, such as experimental searches for neutrinoless double beta decay ( 0 ) and direct detection of dark matter (DM) [7][8][9]. ...
We present the development of a heat flow model utilizing a scintillating crystal for heat and light detection. By analyzing the measured light signals from α\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha$$\end{document}- and β\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\beta$$\end{document}/γ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\gamma$$\end{document}-induced events in a CaMoO4\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_4$$\end{document} crystal, we describe the time-dependent behavior of the scintillation emission and the subsequent generation of delayed phonons in the crystal. The phonon detection channel model incorporates both prompt and delayed generation of a thermal phonons; these are absorbed in a phonon collector film on the crystal surface or converted into a thermal phonon distribution in the crystal. A reasonable agreement is observed in the comparison between the measured signals and the simulated signals derived from the model study. We attribute the observed pulse shape discrimination to the presence of the delayed phonons associated with the scintillation process.
... Antenna-coupled kinetic inductance detector is the preferred choice [9,10]. And the readout system is also crucial for transient source detection [11,12]. This paper is mainly about the design and optimization of the optical system for SHOT. ...
The Space High-cadence Observing Telescope (SHOT) is proposed to conduct a wide-field survey in one of the frequency bands between 1 and 3 THz with an aperture of 0.8 m. It will provide complete terahertz and far-infrared photometry with low-resolution spectroscopy throughout the sky, promoting the study of fast radio bursts, the formation and evolution of stars, and other scientific goals. The telescope will adopt a superconducting kinetic inductance detector to achieve a wide survey of terahertz imaging. This work designs the optical system of SHOT to obtain a large FOV of up to 1.5 deg and match the detector with the size of 60 mm ×\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\times$$\end{document} 60 mm and pixel pitch of 0.8 mm. The primary optical system adopts a Ritchey–Chrétien design. By adding a corrector lens to the optical system and optimization, the aberrations mainly caused by the optical elements in the detector system are reduced. The influence of each component assigned to different terahertz materials is analyzed. The results show that TPX is more suitable than the other two materials. The performance of the optimized optical system is close to its diffraction limit. It will have the characteristics of high image quality and compact layout.
... Detectors operating at low temperatures within the range of tens to hundreds of millikelvin (mK) are pivotal in particle physics. These cryogenic detectors record particle interactions through the minuscule temperature elevation of the order of (µK) triggered by energy deposition in an absorber material, utilizing highly sensitive cryogenic sensors like Transition Edge Sensors (TESs), Neutron Transmutation Doped-thermistors (NTDs), Kinetic Inductance Detectors (KIDs), or Metallic Magnetic Calorimeters (MMCs) to read out the signals [1,2]. Over the past three decades, TESs based on superconducting thin films have been employed by various cryogenic experiments, ranging from world-leading, low-mass dark matter limits for direct detection searches [3][4][5] to coherent elastic neutrino-nucleus scattering (CEνNS) searches [6,7] and space based sky-mapping surveys [8]. ...
... In the last years, low-temperature detectors have significantly evolved, providing significant roles in scientific applications at subKelvin temperatures [5], [6]. These detectors employ superconducting materials to substantially improve detection limits and they have demonstrated significant results in terms of sensitivity within millimeter-wave bands [7], [8]. ...
Lumped-element kinetic inductance detectors (LEKIDs) based on sawtooth inductors for
$W$
-band are presented in this article. A careful analysis is carried out for the cross-polarization in the inductor geometry, which brings out the absorption of the nondesired
$E$
-field component of an incident wave plane. The proposed inductor geometry with sawtooth sections demonstrates improved cross-polarization. The analytical results are verified by comparison with 3-D electromagnetic (EM) simulations. As the first proof of concept,
$W$
-band optical response is demonstrated through quasioptical characterization at room temperature of an aluminum LEKID array. Moreover, a LEKID array based on bilayer superconducting titanium/aluminum (Ti/Al) thin film is developed for evaluating the performance at millikelvin temperatures. Darkness characterization confirms the high-quality factor of the fabricated detectors and the low-frequency design reliability. In addition, cryogenic optical experiments are performed for spectroscopic and detector sensitivity characterization. The proposed geometry opens the possibility of developing large-format polarimetric cameras based on on-chip LEKID structures for future astronomical experiments.
... for electrons (7) and ...
... 196 In addition to the TES type, the MMC type is utilized for XRS, γ-ray spectroscopy, neutrinoless double beta decay for Majorana nature of neutrinos, 197 neutrino mass measurement with electron capture in Ho, 198 MS for neutral fragments in ion storage rings, 199,200 and dark matter search. 7 The MMC type has no function for shortening τ fall of output pulses in a range of ∼ms. Nevertheless, the MMC type with the strong spin-phonon interaction has the fastest τ rise value of 70 ns among calorimeters, 201 which is advantageous to the timing measurement in imaging MS. 199,200 4. Superconductor strip (SS) type a. Excitations in superconductor thin-film nanostrips. ...
Analytical instruments or scientific instruments are indispensable for scientific research and industry. The analytical instruments require a detector that converts physical quantities to be measured (measurands) to electric signals. This Tutorial describes the basics of quantum and thermal detectors, the operation principles of superconductor detectors, and the ultimate performance of state-of-art analytical instruments with superconductivity. We still face fundamental issues, such as the classical Fano factor, the relation between energy gap and mean carrier creation energy, quasiparticle dynamics, and the intermediate state in the middle of superconducting transition; and engineering issues, such as the small sensitive area and the spatially nonuniform response. Nevertheless, enormous efforts have matured superconductor detectors, which enables us to solve the inherent problems of conventional analytical instruments. As an example of the analytical results, we describe x-ray spectroscopy and mass spectrometry at our institute by using three detector types: superconductor tunnel junction, transition edge sensor, and superconductor strip. Microwave kinetic inductance and metallic magnetic calorimetric types are also described. The analytical results may contribute to a wide range of fields, such as dentistry, molecular biology, energy-saving society, planetary science, and prebiotic organic molecules in space.
... b e-mail: yhk@ibs.re.kr c e-mail: krwoo@ust.ac.kr (corresponding author) Fig. 1 Principle of thermal calorimetric detection in a low-temperature detector composed of an absorber and a thermometer sensor. The amount of energy transfer E into the absorber is measured as the temperature increase δT by the thermometer equal to E/C where C is the sum of the heat capacities of the detector components Various sensor technologies have been developed as sensitive thermometers for high-resolution detection in LTD applications [1,12]. Magnetic microcalorimeter (MMC), also known as metallic magnetic calorimeter, is a type of mature sensor technologies that demonstrate high detector performance levels [13][14][15]; other mature sensor technologies include neutron transmutation doped (NTD) Ge thermistor [16,17] and transition edge sensor (TES) [18,19]. ...
... For rare event search experiments of astroparticle physics applications, many detectors have been developed that feature a dielectric crystal as an absorber and an MMC as a sensitive thermometer [12]. In this paper, MMC technologies used in rare event searches are presented, including their working principles and applications. ...
... The direct detection of DM is another important application of LTDs in astroparticle physics experiments. All the experiments, except the DAMA experiment, have found a null result for direct detection; however, the DM detectors of LTDs, based on the sensor technologies of TES and NTD readouts, have been the essential components of global progress over the past two decades [12]. Recently, the low energy threshold of LTDs has provided good sensitivity to cover the low-mass region of the parameter space for the DM mass and interaction cross section between ordinary and dark matter. ...
Magnetic microcalorimeters (MMCs) have become essential components of many science applications requiring high-resolution detection. MMCs serve as sensitive thermometers that measure the temperature increase in a thermal calorimetric detection system at mK temperatures. The MMC technology utilizes a superconducting circuit and electronics together with a magnetic sensor material of a gold or silver alloy doped with a small concentration of erbium. The metallic sensor material ensures the fast thermalization of the sensor itself, which is a critical parameter for achieving good energy resolution and timing resolution in cryogenic particle detection applications. A detector system consisting of a crystal absorber and an MMC is a sensitive detector with a wide dynamic energy range and good energy linearity. Moreover, light detectors based on MMC readouts are applicable to heat and light detection when using a scintillating crystal as an absorber. In this review, we present the methods by which a detector setup is configured with MMCs for rare event search experiments. The design concerns based on the thermal component models are presented for various rare event search applications of double beta decay experiments and dark matter searches.
... Low-temperature detectors (LTDs) have become one of the key detector technologies in astroparticle physics applications [1,2,3]. For neutrino physics in particular, the fundamental properties of neutrinos have been investigated in several outstanding LTD experiments of neutrinoless double beta decay [4,5,6,7]. ...
... A 1×1×1 cm 3 LiF crystal was employed as a hosting material for a 3 H source and a target absorber for the energetic electrons emitted from 3 H beta decay. 3 H can be embedded in LiF from the 6 Li(n,α) 3 H reaction. Because the natural abundance of 6 Li is 7.6% and 6 Li has a large cross-section for thermal neutrons, a considerable amount of 3 H can be created when a LiF crystal is exposed to a neutron flux. ...
... Because the natural abundance of 6 Li is 7.6% and 6 Li has a large cross-section for thermal neutrons, a considerable amount of 3 H can be created when a LiF crystal is exposed to a neutron flux. From the reaction, the 3 H ions are embedded in a LiF crystal and remain in the crystal until they decay to 3 He with a half-life of 12.32 years via a β -decay process [24,25]: ...
We developed a simple small-scale experiment to measure the beta decay spectrum of $^{3}$H. The aim of this research is to investigate the presence of sterile neutrinos in the keV region. Tritium nuclei were embedded in a 1$\times$1$\times$1 cm$^3$ LiF crystal from the $^6$Li(n,$\alpha$)$^3$H reaction. The energy of the beta electrons absorbed in the LiF crystal was measured with a magnetic microcalorimeter at 40 mK. We report a new method of sample preparation, experiments, and analysis of $^3$H beta measurements. The spectrum of a 10-hour measurement agrees well with the expected spectrum of $^3$H beta decay. The analysis results indicate that this method can be used to search for keV-scale sterile neutrinos.
