The complex conductivity of a superconducting thin film is related to the quasiparticle density, which depends on the physical temperature and can also be modified by external pair breaking with ...photons and phonons. This relationship forms the underlying operating principle of Kinetic Inductance Detectors (KIDs), where the detection threshold is governed by the superconducting energy gap. We investigate the electromagnetic properties of thin-film aluminum that is proximitized with either a normal metal layer of copper or a superconducting layer with a lower <inline-formula><tex-math notation="LaTeX">T_{C}</tex-math></inline-formula>, such as iridium, in order to extend the operating range of KIDs. Using the Usadel equations along with the Nam expressions for complex conductivity, we calculate the density of states and the complex conductivity of the resulting bilayers to understand the dependence of the pair breaking threshold, surface impedance, and intrinsic quality factor of superconducting bilayers on the relative film thicknesses. The calculations and analyses provide theoretical insights in designing aluminum-based bilayer kinetic inductance detectors for detection of microwave photons and athermal phonons at the frequencies well below the pair breaking threshold of a pure aluminum film.
Direct detection of nuclear scatterings of sub-GeV dark matter (DM) particles favors low-Z nuclei. Hydrogen nucleus, which has a single proton, provides the best kinematic match. The characteristic ...nuclear recoil energy is boosted by a factor of a few tens from those for larger nuclei used in traditional Weakly Interacting Massive Particles searches. Furthermore, hydrogen is optimal for detecting spin-dependent nuclear scatterings of sub-GeV DM, where large parameter space still remains unconstrained yet. In this paper, we first introduce several hydrogen-rich targets, which emit two classes of signals under kinetic excitations. One class of the signals is infrared photons, which are from fundamental vibrational and rotational modes of molecules and at several characteristic wavelengths. Another is acoustic phonons and optical phonons that decay into acoustic phonons. We then discuss the technical status and future researches of low-
T
c
transition-edge sensor (TES) detectors, which measure the infrared photons and acoustic phonons with desirable sensitivities. Utilization of hydrogen-rich targets and ultra-sensitive low-
T
c
TES detectors for light DM detection requires both theoretical modeling and experimental prototyping.
We are developing a low-
T
c
TES-based large-area and low-threshold detector targeting a variety of potential applications. The detector consists of a 50.8-mm-diameter Si wafer as the substrate and ...radiation absorber, a single Ir/Pt bilayer TES sensor in the center, and normal metal Au pads added to the TES to strengthen the TES–absorber thermal coupling. Tight TES–absorber thermal coupling improves detector sensitivity and response uniformity. Here, we report on the electron–phonon (e–ph) coupling strengths for the Ir/Pt bilayer and Au that are measured with our prototype detectors and TES devices. We found that a second weak thermal link besides the one due to e–ph coupling in Ir/Pt or Au was required to explain our data. With the effects of the second weak link accounted for, the extracted e–ph coupling constant
Σ
for Ir/Pt bilayer in the
T
c
range between 32 and 70 mK is
1.9
×
10
8
WK
-
5
m
-
3
, and
Σ
’s for Au at 40 mK and 55 mK are
2.2
×
10
9
WK
-
5
m
-
3
and
3.2
×
10
9
WK
-
5
m
-
3
, respectively.
Coherent elastic neutrino-nucleus scattering (CEνNS) offers a valuable approach in searching for physics beyond the standard model. The
Ricochet
experiment aims to perform a precision measurement of ...the CEνNS spectrum at the Institut Laue–Langevin nuclear reactor with cryogenic solid-state detectors. The experiment plans to employ an array of cryogenic thermal detectors, each with a mass of around 30 g and an energy threshold of below 100 eV. The array includes nine detectors read out by transition-edge sensors (TES). These TES-based detectors will also serve as demonstrators for future neutrino experiments with thousands of detectors. In this article, we present an update on the characterization and modeling of a prototype TES detector.
Properties of Low TC AlMn TES Wang, G.; Bratrud, G.; Chang, C. L. ...
Journal of low temperature physics,
2024/5, Letnik:
215, Številka:
3-4
Journal Article
Recenzirano
Low T
C
AlMn transition-edge sensors (TESs) have been developed as sensitive thermometers for the Q-Array, which will use superconducting targets to measure the coherent elastic neutrino nucleus ...scattering spectrum in the RICOCHET experiment. The TESs are made of manganese-doped aluminum with a titanium and gold antioxidation layer. A prototype TES thermometer consists of two TESs in parallel, an input gold pad in metallic contact with the TESs and an output gold pad and gold thermal link meanders, which are each designed to control the flow of heat through the TESs. We have fabricated and measured low T
C
AlMn TES chips with or without thermal flow control structures. We present T
C
measurements of the TESs after the initial fabrication and further T
C
tuning by re-heating and summarize the thermal property studies of the prototype TES thermometer by measuring I-V curves and complex impedance.
Planar ortho-mode transducers (OMTs) are a commonly used method of coupling optical signals between waveguides and on-chip circuitry and detectors. While the ideal OMT–waveguide coupling requires ...minimal disturbance to the waveguide, when used for mm-wave applications the waveguide is typically constructed from two sections to allow the OMT probes to be inserted into the waveguide. This break in the waveguide is a source of signal leakage and can lead to loss of performance and increased experimental systematic errors. Here, we report on the development of new OMT-to-waveguide coupling structures with the goal of reducing leakage at the detector wafer interface. The pixel-to-pixel optical leakage due to the gap between the coupling waveguide and the backshort is reduced by means of a protrusion that passes through the OMT membrane and electrically connects the two waveguide sections on either side of the wafer. High-frequency electromagnetic simulations indicate that these protrusions are an effective method to reduce optical leakage in the gap by
∼
80
%
percent, with a
∼
60
%
filling factor, relative to an standard OMT coupling architecture. Prototype devices have been designed to characterize the performance of the new design using a relative measurement with varying filling factors. We outline the simulation setup and results and present a chip layout and sample box that will be used to perform the initial measurements.
One way of making a transition-edge sensor (TES) is by utilizing the proximity effect, in which the
T
C
of a superconducting film is reduced with a normal metal film in metallic contact. The
T
C
of a ...bilayer TES can be estimated by solving the Usadel equations with given boundary conditions. The classical boundary conditions of a bilayer include a specific interface resistance being temperature-independent. In this paper, we will introduce a temperature-dependent specific interface resistance. By fitting the measured
T
C
data of Ir/Au bilayers from the literature to a
T
C
calculation model, we will compare the fit parameters and fit errors with the temperature-dependent specific interface resistance described in this work and with the classical temperature-independent specific interface resistance.
The reference design for the next-generation cosmic microwave background (CMB) experiment, CMB-S4, relies on large arrays of transition-edge sensor (TES) bolometers coupled to Superconducting Quantum ...Interference Device (SQUID)-based readout systems. Mapping the CMB to near cosmic variance limits will enable the search for signatures of inflation and constrain dark energy and neutrino physics. AlMn TESes provide simple film manufacturing and highly uniform arrays over large areas to meet the requirements of the CMB-S4 experiment. TES parameters such as critical temperature and normal resistance must be tuned to experiment specifications and can be varied based on geometry and steps in the fabrication process such as deposition layering, geometry, and baking time and temperature. Using four-terminal sensing, we measured
T
C
and
R
N
of AlMn 2000 ppm films and devices of varying thicknesses fabricated at Argonne National Laboratory to motivate device geometries and fabrication processes to tune
T
C
to 150–200 mK and
R
N
to
∼
10 m
Ω
. Measurements of IV curves and time constants for the resulting devices of varying leg length were made using time-division SQUID multiplexing and determined
T
C
,
G
,
k
,
f
3
db
, and
R
N
. We present the results of these tests along with the geometries and fabrication steps used to tune the device parameters to the desired limits.
We propose a multiplexible kinetic inductance ammeter, which uses a high-quality-factor, superconducting, lumped-element, kinetic inductance resonator as a current sensor, a short, superconducting ...coplanar waveguide (CPW) for current input, and a CPW transmission line for the sensor readout. The resonator consists of an interdigitated capacitor and a superconducting loop that inductively couples to the input CPW. Current running through the central line of the input CPW generates magnetic fields which are focused into the gaps of the input CPW. These magnetic fields can be measured collectively as the magnetic flux through the superconducting loop. The kinetic inductance of the superconducting loop depends on the screening current for the magnetic flux, so the input current is converted to a change in the frequency of the resonator. We analyze the response and noise of a kinetic inductance ammeter with a high-resistivity NbN loop.
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