102 research outputs found
Axion search with a quantum-limited ferromagnetic haloscope
A ferromagnetic axion haloscope searches for Dark Matter in the form of
axions by exploiting their interaction with electronic spins. It is composed of
an axion-to-electromagnetic field transducer coupled to a sensitive rf
detector. The former is a photon-magnon hybrid system, and the latter is based
on a quantum-limited Josephson parametric amplifier. The hybrid system consists
of ten 2.1 mm diameter YIG spheres coupled to a single microwave cavity mode by
means of a static magnetic field. Our setup is the most sensitive rf
spin-magnetometer ever realized. The minimum detectable field is
T with 9 h integration time, corresponding to a limit on
the axion-electron coupling constant at 95% CL.
The scientific run of our haloscope resulted in the best limit on DM-axions to
electron coupling constant in a frequency span of about 120 MHz, corresponding
to the axion mass range -eV. This is also the first apparatus
to perform an axion mass scanning by changing the static magnetic field.Comment: 4 pages, 4 figure
Searching for galactic axions through magnetized media: QUAX status report
The current status of the QUAX R\&D program is presented. QUAX is a
feasibility study for a detection of axion as dark matter based on the coupling
to the electrons. The relevant signal is a magnetization change of a magnetic
material placed inside a resonant microwave cavity and polarized with a static
magnetic field.Comment: Contributed to the 13th Patras Workshop on Axions, WIMPs and WISPs,
Thessaloniki, May 15 to 19, 201
Cavity magnon polariton based precision magnetometry
A photon-magnon hybrid system can be realised by coupling the electron spin
resonance of a magnetic material to a microwave cavity mode. The quasiparticles
associated with the system dynamics are the cavity magnon polaritons, which
arise from the mixing of strongly coupled magnons and photons. We illustrate
how these particles can be used to probe the magnetisation of a sample with a
remarkable sensitivity, devising suitable spin-magnetometers which ultimately
can be used to directly assess oscillating magnetic fields. Specifically, the
capability of cavity magnon polaritons of converting magnetic excitations to
electromagnetic ones, allows for translating to magnetism the quantum-limited
sensitivity reached by state-of-the-art electronics. Here we employ hybrid
systems composed of microwave cavities and ferrimagnetic spheres, to
experimentally implement two types of novel spin-magnetometers.Comment: 7 pages, 3 figure
Comparative analysis of mesenchymal stromal cells biological properties
The stromal progenitors of mesodermal cells, mesenchymal stromal cells (MSCs), are a heterogeneous population of plastic adherent fibroblast-like cells with extensive proliferative capacity and differentiation potential. Human MSCs have now been isolated from various tissues including bone marrow, muscle, skin, and adipose tissue, the latter being one of the most suitable cell sources for cell therapy, because of its easy accessibility, minimal morbidity, and abundance of cells. Bone marrow and subcutaneous or visceral adipose tissue samples were collected, digested with collagenase if needed, and seeded in Iscove's medium containing 5% human platelet lysate. Nonadherent cells were removed after 2-3 days and the medium was replaced twice a week. Confluent adherent cells were detached, expanded, and analyzed for several biological properties such as morphology, immunophenotype, growth rate, senescence, clonogenicity, differentiation capacity, immunosuppression, and secretion of angiogenic factors. The results show significant differences between lines derived from subcutaneous fat compared to those derived from visceral fat, such as the higher proliferation rate of the first and the strong induction of angiogenesis of the latter. We are convinced that the identification of the peculiarities of MSCs isolated from different tissues will lead to their more accurate use in cell therapy
Out-of-equilibrium phonons in gated superconducting switches
Recent experiments have suggested that superconductivity in metallic nanowires can be suppressed by the application of modest gate voltages. The source of this gate action has been debated and either attributed to an electric-field effect or to small leakage currents. Here we show that the suppression of superconductivity in titanium nitride nanowires on silicon substrates does not depend on the presence or absence of an electric field at the nanowire, but requires a current of high-energy electrons. The suppression is most efficient when electrons are injected into the nanowire, but similar results are obtained when electrons are passed between two remote electrodes. This is explained by the decay of high-energy electrons into phonons, which propagate through the substrate and affect superconductivity in the nanowire by generating quasiparticles. By studying the switching probability distribution of the nanowire, we also show that high-energy electron emission leads to a much broader phonon energy distribution compared with the case where superconductivity is suppressed by Joule heating near the nanowire
High quality factor photonic cavity for dark matter axion searches
Searches for dark matter axion involve the use of microwave resonant cavities
operating in a strong magnetic field. Detector sensitivity is directly related
to the cavity quality factor, which is limited, however, by the presence of the
external magnetic field. In this paper we present a cavity of novel design
whose quality factor is not affected by a magnetic field. It is based on a
photonic structure by the use of sapphire rods. The quality factor at cryogenic
temperature is in excess of for a selected mode.Comment: 6 pages, 7 figure
Galactic axions search with a superconducting resonant cavity
To account for the dark matter content in our Universe, post-inflationary
scenarios predict for the QCD axion a mass in the range
(10-10^3)\,\mu\mbox{eV}. Searches with haloscope experiments in this mass
range require the monitoring of resonant cavity modes with frequency above
5\,GHz, where several experimental limitations occur due to linear amplifiers,
small volumes, and low quality factors of Cu resonant cavities. In this paper
we deal with the last issue, presenting the result of a search for galactic
axions using a haloscope based on a 36\,\mbox{cm}^3 NbTi superconducting
cavity. The cavity worked at T=4\,\mbox{K} in a 2\,T magnetic field and
exhibited a quality factor for the TM010 mode at 9\,GHz.
With such values of the axion signal is significantly increased with
respect to copper cavity haloscopes. Operating this setup we set the limit
g_{a\gamma\gamma}<1.03\times10^{-12}\,\mbox{GeV}^{-1} on the axion photon
coupling for a mass of about 37\,eV. A comprehensive study of the NbTi
cavity at different magnetic fields, temperatures, and frequencies is also
presented
Search for galactic axions with a high-Q dielectric cavity
A haloscope of the QUAX-- experiment, composed of an high-Q resonant
cavity immersed in a 8 T magnet and cooled to ~K is operated to
search for galactic axion with mass . The design of
the cavity with hollow dielectric cylinders concentrically inserted in a OFHC
Cu cavity, allowed us to maintain a loaded quality-factor Q
during the measurements in presence of magnetic field. Through the cavity
tuning mechanism it was possible to modulate the resonance frequency of the
haloscope in the region ~GHz and thus acquire different
dataset at different resonance frequencies. Acquiring each dataset for about 50
minutes, combining them and correcting for the axion's signal
estimation-efficiency we set a limit on the axion-photon coupling
GeV with the confidence level
set at
- …