This work describes the design and implementation of optics for EXCLAIM, the EXperiment for Cryogenic Large-Aperture Intensity Mapping. EXCLAIM is a balloon-borne telescope that will measure integrated line emission from carbon monoxide at redshifts z < 1 and ionized carbon ([CII]) at redshifts z = 2.5 − 3.5 to probe star formation over cosmic time in cross-correlation with galaxy redshift surveys. The EXCLAIM instrument is designed to observe at frequencies of 420–540 GHz using six microfabricated silicon integrated spectrometers with spectral resolving power R = 512 coupled to kinetic inductance detectors. A completely cryogenic telescope cooled to a temperature below 5 K provides low-background observations between narrow atmospheric lines in the stratosphere. Off-axis reflective optics use a 90-cm primary mirror to provide 4.2′ full-width at half-maximum resolution at the center of the EXCLAIM band over a field of view of 22.5′. Illumination of the 1.7 K cold stop combined with blackened baffling at multiple places in the optical system ensures low (<−40 dB) edge illumination of the primary to minimize spill onto warmer elements at the top of the dewar.

Irradiation of high-temperature superconductor YBa2Cu3O7 (YBCO) with high-energy He+ ions is known to cause structural changes in the YBCO film, decreasing the critical temperature TC and finally leading to a superconductor-to-insulator transition. This allows one to pattern narrow insulating regions with a focused ion beam (FIB) and thus fabricate nanoscale Josephson junctions on YBCO films. Moreover, such ion irradiation is known to cause structural changes in the YBCO film. However, details of how these structural changes occur in nanoscale devices produced by FIB remain unknown. Using nanofocus X-ray diffraction, we study the changes in the YBCO crystal lattice and investigate how the nature of these changes depends on the size of the irradiated regions. These data provide an important understanding of how oxide superconductors can be tailored at the nanometer scale for various applications.

The EXperiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM) is a balloon-borne telescope designed to survey star formation over cosmological time scales using intensity mapping in the 420 - 540 GHz frequency range. EXCLAIM uses a fully cryogenic telescope coupled to six on-chip spectrometers featuring kinetic inductance detectors (KIDs) to achieve high sensitivity, allowing for fast integration in dark atmospheric windows. The telescope receiver is cooled to approximate to 1.7 K by immersion in a superfluid helium bath and enclosed in a superfluid-tight shell with a meta-material anti-reflection coated silicon window. In addition to the optics and the spectrometer package, the receiver contains the magnetic shielding, the cryogenic segment of the spectrometer readout, and the sub-Kelvin cooling system. A three-stage continuous adiabatic demagnetization refrigerator (CADR) keeps the detectors at 100 mK while a He-4 sorption cooler provides a 900 mK thermal intercept for mechanical suspensions and coaxial cables. We present the design of the EXCLAIM receiver and report on the flight-like testing of major receiver components, including the superfluid-tight receiver window and the sub-Kelvin coolers.

We present the first search for the Majoron-emitting modes of the neutrinoless double beta decay (0 nu beta beta chi 0) using scintillating cryogenic calorimeters. We analyzed the CUPID-0 Phase I data using a Bayesian approach to reconstruct the background sources activities, and evaluate the potential contribution of the 82Se 0 nu beta beta chi 0. We considered several possible theoretical models which predict the existence of a Majoronlike boson coupling to the neutrino. The energy spectra arising from the emission of such bosons in the neutrinoless double beta decay have spectral indices n = 1, 2, 3, or 7. We found no evidence of any of these decay modes, setting a lower limit (90% of credibility interval) on the half-life of 1.2 x 1023 yr in the case of n = 1, 3.8 x 1022 yr for n = 2, 1.4 x 1022 yr for n = 3 and 2.2 x 1021 yr for n = 7. These are the best limits on the 0 nu beta beta chi 0 half-life of the 82Se, and demonstrate the potentiality of the CUPID-0 technology in this field.

One of the most energetic events in the Universe are core-collapse Supernovae (SNe), where almost all the star's binding energy is released as neutrinos. These particles are direct probes of the processes occurring in the stellar core and provide unique insights into the gravitational collapse. RES-NOVA will revolutionize how we detect neutrinos from astrophysical sources, by deploying the first ton-scale array of cryogenic detectors made from archaeological lead. Pb offers the highest neutrino interaction cross-section via coherent elastic neutrino-nucleus scattering (CE$\nu$NS). Such process will enable RES-NOVA to be equally sensitive to all neutrino flavors. For the first time, we propose to use archaeological Pb as sensitive target material in order to achieve an ultra-low background level in the region of interest (\textit{O}(1keV)). All these features make possible the deployment of the first cm-scale neutrino telescope for the investigation of astrophysical sources. In this contribution, we will characterize the radiopurity level and the performance of a small-scale proof-of-principle detector of RES-NOVA, consisting in a PbWO$_4$ crystal made from archaeological-Pb operated as cryogenic detector.

We report on the results obtained with the global CUPID-0 background model, which combines the data collected in the two measurement campaigns for a total exposure of 8.82  kg×yr of ^{82}Se. We identify with improved precision the background sources within the 3 MeV energy region, where neutrinoless double β decay of ^{82}Se and ^{100}Mo is expected, making more solid the foundations for the background budget of the next-generation CUPID experiment. Relying on the excellent data reconstruction, we measure the two-neutrino double β-decay half-life of ^{82}Se with unprecedented accuracy: T_{1/2}^{2ν}=[8.69±0.05(stat)_{-0.06}^{+0.09}(syst)]×10^{19}  yr.

CUPID-0, an array of Zn^{82}Se cryogenic calorimeters, was the first medium-scale demonstrator of the scintillating bolometers' technology. The first project phase (March 2017-December 2018) allowed the most stringent limit on the neutrinoless double beta decay half-life of the isotope of interest, ^{82}Se, to be set. After a six month long detector upgrade, CUPID-0 began its second and last phase (June 2019-February 2020). In this Letter, we describe the search for neutrinoless double beta decay of ^{82}Se with a total exposure (phase I+II) of 8.82  kg yr^{-1} of isotope. We set a limit on the half-life of ^{82}Se to the ground state of ^{82}Kr of T_{1/2}^{0ν}(^{82}Se)>4.6×10^{24}  yr (90% credible interval), corresponding to an effective Majorana neutrino mass m_{ββ}<(263-545)  meV. We also set the most stringent lower limits on the neutrinoless decays of ^{82}Se to the 0_{1}^{+}, 2_{1}^{+}, and 2_{2}^{+} excited states of ^{82}Kr, finding 1.8×10^{23}  yr, 3.0×10^{23}  yr, and 3.2×10^{23}  yr (90% credible interval) respectively.

The past few decades have seen major developments in the design and operation of cryogenic particle detectors. This technology offers an extremely good energy resolution, comparable to semiconductor detectors, and a wide choice of target materials, making low temperature calorimetric detectors ideal for a variety of particle physics applications. Rare event searches have continued to require ever greater exposures, which has driven them to ever larger cryogenic detectors, with the CUORE experiment being the first to reach a tonne-scale, mK-cooled, experimental mass. CUORE, designed to search for neutrinoless double beta decay, has been operational since 2017 at a temperature of about 10 mK. This result has been attained by the use of an unprecedentedly large cryogenic infrastructure called the CUORE cryostat: conceived, designed and commissioned for this purpose. In this article the main characteristics and features of the cryogenic facility developed for the CUORE experiment are highlighted. A brief introduction of the evolution of the field and of the past cryogenic facilities are given. The motivation behind the design and development of the CUORE cryogenic facility is detailed as are the steps taken toward realization, commissioning, and operation of the CUORE cryostat. The major challenges overcome by the collaboration and the solutions implemented throughout the building of the cryogenic facility will be discussed along with the potential improvements for future facilities. The success of CUORE has opened the door to a new generation of large-scale cryogenic facilities in numerous fields of science. Broader implications of the incredible feat achieved by the CUORE collaboration on the future cryogenic facilities in various fields ranging from neutrino and dark matter experiments to quantum computing will be examined.

CUPID-0 is a pilot experiment in scintillating cryogenic calorimetry for the search of neutrino-less double beta decay. 26 ZnSe crystals were operated continuously in the first project phase (March 2017 - December 2018), demonstrating unprecedented low levels of background in the region of interest at the Q-value of $^{82}\rm{Se}$. From this successful experience comes a demonstration of full alpha to beta/gamma background separation, the most stringent limits on the $^{82}\rm{Se}$ neutrino-less double beta decay, as well as the most precise measurement of the $^{82}$Se half-life. After a detector upgrade, CUPID-0 began its second and last phase (June 2019 - February 2020). We present the latest results on the neutrino-less double beta decay of $^{82}\rm{Se}$ with the full isotope exposure of $8.82~\rm{kg}\times\rm{yr}$. We set a lower bound to the ground state half life $\rm{T}_{1/2}( ^{82}\rm{Se})>4.6\times10^{24}$ yr (90 % C.I.). We review the most recent results from a Bayesian search for spectral distortions to the $^{82}\rm{Se}$ double-beta decay spectrum due to exotic decay modes.

Abstract RES-NOVA is a newly proposed experiment for detecting neutrinos from astrophysical sources, mainly Supernovae, using an array of cryogenic detectors made of PbWO $$_4$$ 4 crystals produced from archaeological Pb. This unconventional material, characterized by intrinsic high radiopurity, enables low-background levels in the region of interest for the neutrino detection via Coherent Elastic neutrino-Nucleus Scattering (CE $$\nu $$ ν NS). This signal lies at the detector energy threshold, O(1 keV), and it is expected to be hidden by naturally occurring radioactive contaminants of the crystal absorber. Here, we present the results of a radiopurity assay on a 0.84 kg PbWO $$_4$$ 4 crystal produced from archaeological Pb operated as a cryogenic detector. The crystal internal radioactive contaminations are: $$^{232}$$ 232 Th <40 $$\upmu $$ μ Bq/kg, $$^{238}$$ 238 U <30 $$\upmu $$ μ Bq/kg, $$^{226}$$ 226 Ra 1.3 mBq/kg and $$^{210}$$ 210 Pb 22.5 mBq/kg. We also present a background projection for the final experiment and possible mitigation strategies for further background suppression. The achieved results demonstrate the feasibility of realizing this new class of detectors.

Understanding hydrogen intercalation and deintercalation in palladium is the key to utilizing palladium-based materials for hydrogen storage, hydrogen separations, and electrochemical hydrogen evolution and CO2 reduction catalysis. Here, we combine in situ synchrotron X-ray diffraction and coulometry measurements with density functional theory calculations to provide complementary insights on the dynamics of hydrogen intercalation and deintercalation under electrochemical conditions. By employing multimodal in situ characterization, we demonstrate that the interplanar d-spacing and the hydrogen/palladium ratio are decorrelated under certain conditions. Additionally, there is a clear hysteresis in the electrode potentials where the beta-phase of palladium hydride forms and disappears. Computed energetics of hydrogen intercalation and deintercalation predict this hysteresis. These calculations indicate that the potential-driven absorption of subsurface hydrogen during intercalation and oxidation of surface hydrogen during deintercalation could contribute to the observed hysteresis. These results suggest that surface processes during hydrogen intercalation and deintercalation are important, providing additional mechanistic understanding that is complementary to bulk phase transition theory. This multimodal in situ characterization and computational study provides new insights into hydrogen intercalation and deintercalation in palladium electrodes, which could lead to improvements in palladium-based materials needed in a sustainable energy economy.

Abstract. The experiment for cryogenic large-aperture intensity mapping (EXCLAIM) is a balloon-borne telescope designed to survey star formation in windows from the present to z  =  3.5. During this time, the rate of star formation dropped dramatically, while dark matter continued to cluster. EXCLAIM maps the redshifted emission of singly ionized carbon lines and carbon monoxide using intensity mapping, which permits a blind and complete survey of emitting gas through statistics of cumulative brightness fluctuations. EXCLAIM achieves high sensitivity using a cryogenic telescope coupled to six integrated spectrometers employing kinetic inductance detectors covering 420 to 540 GHz with spectral resolving power R  =  512 and angular resolution ≈4  arc min. The spectral resolving power and cryogenic telescope allow the survey to access dark windows in the spectrum of emission from the upper atmosphere. EXCLAIM will survey 305  deg2 in the Sloan Digital Sky Survey Stripe 82 field from a conventional balloon flight in 2023. EXCLAIM will also map several galactic fields to study carbon monoxide and neutral carbon emission as tracers of molecular gas. We summarize the design phase of the mission.

Localization and modeling of radioactive contaminations is a challenge that ultra-low background experiments are constantly facing. These are fundamental steps both to extract scientific results and to further reduce the background of the detectors. Here we present an innovative technique based on the analysis of α - α delayed coincidences in 232 Th and 238 U decay chains, developed to investigate the contaminations of the ZnSe crystals in the CUPID-0 experiment. This method allows to disentangle surface and bulk contaminations of the detectors relying on the different probability to tag delayed coincidences as function of the α decay position.

Rare event physics demands very detailed background control, high-performance detectors, and custom analysis strategies. Cryogenic calorimeters combine all these ingredients very effectively, representing a promising tool for next-generation experiments. CUPID-0 is one of the most advanced examples of such a technique, having demonstrated its potential with several results obtained with limited exposure. In this paper, we present a further application. Exploiting the analysis of delayed coincidence, we can identify the signals caused by the 220Rn-216Po decay sequence on an event-by-event basis. The analysis of these events allows us to extract the time differences between the two decays, leading to a new evaluation of 216Po half-life, estimated as (143.3±2.8) ms.

CUPID-0 is the first pilot experiment of CUPID, a next-generation project searching for neutrinoless double beta decay. In its first scientific run, CUPID-0 operated 26 ZnSe cryogenic calorimeters coupled to light detectors in the underground Laboratori Nazionali del Gran Sasso. In this work, we analyzed a ZnSe exposure of 11.34 kg year to search for the neutrinoless double beta decay of ^70 Zn and for the neutrinoless positron-emitting electron capture of ^64 Zn. We found no evidence for these decays and set 90 % credible interval limits of T_1/2^0νββ ( ^70 Zn) > 1.6 10^21 year and T_1/2^0ν EC β + ( ^64 Zn) > 1.2 × 10^22 year, surpassing by more than one order of magnitude the previous experimental results (Belli et al. in J Phys G 38(11):115107, https://doi.org/10.1088/0954-3899/38/11/115107 , 2011).

The nucleus is an extraordinarily complex object where fundamental forces are at work. The solution of this many-body problem has challenged physicists for decades: several models with complementary virtues and flaws have been adopted, none of which has a universal predictive capability. Double beta decay is a second order weak nuclear decay whose precise measurement might steer fundamental improvements in nuclear theory. Its knowledge paves the way to a much better understanding of many body nuclear dynamics and clarifies, in particular, the role of multiparticle states. This is a useful input to a complete understanding of the dynamics of neutrino-less double beta decay, the chief physical process whose discovery may shed light to matter-antimatter asymmetry of the universe and unveil the true nature of neutrinos. Here, we report the study of 2νββ-decay in 82Se with the CUPID-0 detector, an array of ZnSe crystals maintained at a temperature close to ‘absolute zero’ in an ultralow background environment. Thanks to the unprecedented accuracy in the measurement of the two electrons spectrum, we prove that the decay is dominated by a single intermediate state. We obtain also the most precise value for the 82Se 2νββ-decay half-life of T1/22ν=[8.6+0.2−0.1]×1019 yr.

The electrochemical CO2 reduction reaction (CO2RR) using Cu-based catalysts holds great potential for producing valuable multi-carbon products from renewable energy. However, the chemical and structural state of Cu catalyst surfaces during the CO2RR remains a matter of debate. Here, we show the structural evolution of the near-surface region of polycrystalline Cu electrodes under in situ conditions through a combination of grazing incidence X-ray absorption spectroscopy (GIXAS) and X-ray diffraction (GIXRD). The in situ GIXAS reveals that the surface oxide layer is fully reduced to metallic Cu before the onset potential for CO2RR, and the catalyst maintains the metallic state across the potentials relevant to the CO2RR. We also find a preferential surface reconstruction of the polycrystalline Cu surface toward (100) facets in the presence of CO2. Quantitative analysis of the reconstruction profiles reveals that the degree of reconstruction increases with increasingly negative applied potentials, and it persists when the applied potential returns to more positive values. These findings show that the surface of Cu electrocatalysts is dynamic during the CO2RR, and emphasize the importance of in situ characterization to understand the surface structure and its role in electrocatalysis.

We present a search for β/EC double beta decay of 120Te performed with the CUORICINO experiment, an array of TeO2 cryogenic bolometers. After collecting 0.0573 kg·y of 120Te, we see no evidence of a signal and therefore set the following limits on the halflife: T0ν 1/2 > 1.9 · 1021 y at 90% C.L. for the 0ν mode and T2ν 1/2 > 7.6 · 1019 y at 90% C.L. for the 2ν mode. These results improve the existing limits by almost three orders of magnitude (four in the case of 0ν mode). The discovery of neutrino oscillations [1] proved that neutrinos are massive, but there are fundamental issues that oscillation experiments cannot address: measuring the absolute neutrino mass and determining whether the neutrino is the antiparticle of itself, thus being of Majorana nature, or not. To answer these questions it is necessary to look for neutrinoless double beta, 0νββ, decays, which would bring conclusive evidence of the Majorana nature of the neutrino and whose decay rates constrain the absolute neutrino mass [2]. Double beta decays can occur by either emitting two electrons or two positrons. In the latter case, either of the positron emissions can be replaced by an electron capture (EC). While β−β− decays have the largest expected rates, β/EC and ββdecays provide clear signatures from the 511-keV annihilation gamma rays. Energy and momentum conservation in the EC/EC decay requires an extra radiative process, reducing the rate by several orders of magnitude. This paper reports on a search for β/EC decays 120Te →120 Sn + e and 120Te →120 Sn + e + 2ν with the CUORICINO experiment, an array of TeO2 cryogenic bolometers at the Gran Sasso National Laboratories. The 120Te isotope has been only minimally investigated from a theoretical point of view. No calculations of the half-life of 0νβ/EC decay of 120Te are available for comparison with our result. The predictions for the same decay mechanism in other nuclei, assuming the effective Majorana mass 〈mν〉 = 1 eV, range between 1026–1027 y [3, 4]. The larger value is mostly due to the need to have simultaneously a decay and a capture and to the reduced phase space available. The only reference for the two neutrino mode [5] yields a theoretical value for the half-life of 4.4 · 1026 y. In recent years, experimental limits on the 120Te decays have been set using an array of CdZnTe detectors located at the Gran Sasso Underground Laboratory [6, 7] and a HPGe detector at the Modane Underground Laboratory [8, 9]. The present best limits in the literature are T0ν 1/2 > 4.1 · 1017 y [7] and T (0ν+2ν) 1/2 > 1.9 · 1017 y [8]. The search strategy is the following: the emitted positron carries a kinetic energy up to Kmax = Q 2mec Eb, where Eb is the binding energy of the captured electron within the atomic Preprint submitted to Elsevier December 31, 2010 Figure 1: A sketch of the CUORICINO assembly showing the tower hanging from the mixing chamber, the various heat shields and the external shielding. shell and Q= (1714.8 ± 1.3) keV [10] is the difference in 120Te and 120Sn atomic masses. The electron capture is most likely to occur from the K shell, whose binding energy is 30.5 keV. The ratio of L-capture to K-capture for most elements is around 10% (12% for120Sb→ 120Sn EC decay) [11]. In the following we will always assume a capture from the K shell. The bolometer where the decay occurs will see the deposition of both the binding energy and the kinetic energy of the positron (maximum energy: E0 = Kmax + Eb = Q − 2mec = 692.8 keV, independent of Eb). Once at rest, the positron annihilates with an electron and two photons with an energy Eγ = 511.0 keV are emitted. These photons can interact with the same bolometer or by a nearby one, or they can escape undetected. The analysis presented here searches for the signatures with the best signal-to-noise ratio. This is not the case for the events where the entire energy is deposited inside the detector, due to the low detection efficiency (see Table 1). For the 0ν mode, where the positron is monochromatic, this means the coincidence between a bolometer with an energy deposition consistent with Eγ and one with either E0 or E0 + Eγ and the coincidence of one bolometer with a signal of E0 and two other bolometers with a signal of Eγ. For the 2ν mode, where the positron is emitted with a continuum of kinetic energies between 0 and Kmax, this means the triple coincidence of one bolometer with a signal between Eb and E0 and two others with a signal of Eγ. 1. The CUORICINO detector The CUORICINO experiment is detailed in Ref. [12]. Briefly, it is an array of TeO2 crystals acting as cryogenic bolometers at a working temperature of 8–10 mK and with heat 1Here and in the following we assume that the X-rays following the EC do not escape from the crystal where the decay occurs. capacity 2.3 · 10−9 J/K. To measure temperature variations corresponding to few keV (∆T ∼ 0.1 μK/keV) heavily doped highresistance germanium thermistors (NTD, Neutron Transmutation Doped) are glued to each crystal. The CUORICINO detector consists of 62 TeO2 crystals arranged in 13 planes. Each of the upper 10 planes and the lowest one consists of four 5 × 5 × 5 cm3 TeO2 crystals, while the 11th and 12th planes have nine, 3×3×6 cm3 crystals. All crystals have natural isotopic abundances except four of the smaller crystals, two of which are enriched to 82.3% in 128Te and two to 75% in 130Te. The natural abundance of 120Te is 0.096% [13], so the 39.4 kg of the CUORICINO experiment (enriched crystals are not included) contain Nββ = 1.43 · 1023 nuclei of 120Te . The experiment is shielded with two layers of lead of 10 cm minimum thickness each. The outer layer is made of common low radioactivity lead, while the inner layer is made of special lead with a low activity of 210Pb. The electrolytic copper of the refrigerator thermal shields provides an additional shield with a minimum thickness of 2 cm. An external 10 cm layer of borated polyethylene was installed to reduce the background due to environmental neutrons. The detector itself is shielded against the intrinsic radioactive contamination of the dilution unit materials by an internal layer of 10 cm of Roman lead [14], located inside the cryostat immediately above the tower. The background from the activity in the lateral thermal shields of the dilution refrigerator is reduced by a lateral internal 1.4 cm thick shield of Roman lead. Another 8 cm lead shield is located at the bottom of the tower. The refrigerator is surrounded by a Plexiglas antiradon box flushed with clean N2 from a liquid nitrogen evaporator and is also enclosed in a Faraday cage to eliminate electromagnetic interference. A sketch of the assembly is shown in Fig. 1. Signature [energies in keV] μ ε [%] (30.5 – 692.8) 1 3.00 ± 0.02 (30.5 – 692.8) + 511 2 3.40 ± 0.02 (30.5 – 692.8) + 511 + 511 3 0.45 ± 0.01 (541.5 – 1203.8) 1 16.28 ± 0.04 (541.5 – 1203.8) + 511 2 6.23 ± 0.03 (1052.5 – 1714.8) 1 10.04 ± 0.03 Table 1: Signatures of 120Te β/EC decay in an array of TeO2 detectors and their corresponding multiplicity (μ), that is the number of detectors with an energy deposition above threshold. The detection efficiency for the 0ν mode in CUORICINO is reported in the last column (ε). We denote with the + sign the coincidence of energies released in different detectors. For the 0ν mode the energy released in the detector where the decay occurred corresponds to the upper bound of the interval. The errors are statistical only. For the present analysis, the full CUORICINO statistics (data collected between May 2004 and May 2008) for a total exposure of 0.0573 kg·y of 120Te is used. The total energy spectrum of all detectors is shown in Fig. 2. Several peaks of radioactive isotopes are clearly visible, the most prominent are labeled.

AbstractCUPID-0 is the first pilot experiment of CUPID, a next-generation project searching for neutrinoless double beta decay. In its first scientific run, CUPID-0 operated 26 ZnSe cryogenic calorimeters coupled to light detectors in the underground Laboratori Nazionali del Gran Sasso. In this work, we analyzed a ZnSe exposure of 11.34 kg year to search for the neutrinoless double beta decay of $$^{70}$$70Zn and for the neutrinoless positron-emitting electron capture of $$^{64}$$64Zn. We found no evidence for these decays and set 90$$\%$$% credible interval limits of $$\hbox {T}_{1/2}^{0\nu \beta \beta }$$T1/20νββ($$^{70}$$70Zn) > 1.6 $$10^{21}$$1021 year and $$\hbox {T}_{1/2}^{0\nu EC \beta +}$$T1/20νECβ+($$^{64}$$64Zn) > 1.2$$\times 10^{22}$$×1022 year, surpassing by more than one order of magnitude the previous experimental results (Belli et al. in J Phys G 38(11):115107, https://doi.org/10.1088/0954-3899/38/11/115107, 2011).