317 research outputs found
Heat Capacity and Thermal Conductance Measurements of a Superconducting-Normal Mixed State by Detection of Single 3 eV Photons in a Magnetic Penetration Thermometer
We report on measurements of the detected signal pulses in a molybdenum-gold Magnetic Penetration Thermometer (MPT) in response to absorption of one or more 3 eV photons. We designed and used this MPT sensor for x-ray microcalorimetry. In this device, the diamagnetic response of a superconducting MoAu bilayer is used to sense temperature changes in response to absorbed photons, and responsivity is enhanced by a Meissner transition in which the magnetic flux penetrating the sensor changes rapidly to minimize free energy in a mixed superconducting normal state. We have previously reported on use of our MPT to study a thermal phonon energy loss to the substrate when absorbing x-rays. We now describe results of extracting heat capacity C and thermal conductance G values from pulse height and decay time of MPT pulses generated by 3 eV photons. The variation in C and G at temperatures near the Meissner transition temperature (set by an internal magnetic bias field) allow us to probe the behavior in superconducting normal mixed state of the condensation energy and the electron cooling power resulting from quasi-particle recombination and phonon emission. The information gained on electron cooling power is also relevant to the operation of other superconducting detectors, such as Microwave Kinetic Inductance Detectors
Study of the Dependency on Magnetic Field and Bias Voltage of an AC-Biased TES Microcalorimeter
At SRON we are studying the performance of a Goddard Space Flight Center single pixel TES microcalorimeter operated in an AC bias configuration. For x-ray photons at 6 keV the pixel shows an x-ray energy resolution Delta E(sub FWHM) = 3.7 eV, which is about a factor 2 worse than the energy resolution observed in an identical DC-biased pixel. In order to better understand the reasons for this discrepancy we characterized the detector as a function of temperature, bias working point and applied perpendicular magnetic field. A strong periodic dependency of the detector noise on the TES AC bias voltage is measured. We discuss the results in the framework of the recently observed weak-link behaviour of a TES microcalorimeter
Fabrication of Microstripline Wiring for Large Format Transition Edge Sensor Arrays
We have developed a process to integrate microstripline wiring with transition edge sensors (TES). The process includes additional layers for metal-etch stop and dielectric adhesion to enable recovery of parameters achieved in non-microstrip pixel designs. We report on device parameters in close-packed TES arrays achieved with the microstrip process including R(sub n), G, and T(sub c) uniformity. Further, we investigate limits of this method of producing high-density, microstrip wiring including critical current to determine the ultimate scalability of TES arrays with two layers of wiring
Current Status of the Solar Neutrino Problem with Super-Kamiokande
We perform an updated model-independent analysis using the latest solar
neutrino data obtained by Cl and Ga radiochemical experiments,
and most notably by a large water-Cherenkov detector SuperKamiokande with their
504 days of data taking. We confirm that the astrophysical solutions to the
solar neutrino problem are extremely disfavored by the data and a
low-temperature modification of the standard solar model is excluded by more
than 5 . We also propose a new way of illuminating the suppression
pattern of various solar neutrino flux without invoking detailed flavor
conversion mechanisms. It indicates that the strong suppression of Be
neutrinos is no more true when the neutrino flavor conversion is taken into
account.Comment: RevTex file, 10 pages, 7 postscript figure
Implications of New Gallex Results for the MSW Solution of the Solar Neutrino Problem
We compare the implications for 7Be and pp neutrinos of the two MSW fits to
the new GALLEX solar neutrino measurements . Small mixing angle solutions tend
to suppress the former as electron-neutrinos, but not the latter, and large
angle solutions tend to reduce both by about a factor of 2. The consequences
for BOREXINO and similar solar neutrino--electron scattering experiments are
discussed.Comment: 7 pages (plus 3 figures available upon request) UTAPHY-HEP-
Superconducting Effects in Optimization of Magnetic Penetration Thermometers for X-ray Microcalorimeters
Like MMCs, MPTs enable high energy microcalorimeters with zero bias power dissipation and potential resolution < 1 eV. MPTs can provide d(phi)/dT as large as 1000 (Phi)(sub 0)/K, with no excess noise, thereby reducing the importance of SQUID noise. Long coherence length in a Type-I superconducting MoAu film offers multiple advantages for efficient flux expulsion in MPT. Region of steepest d(phi)/dT is the Meissner effect in the small device; flux is expelled/penetrates to minimize free energy. Steepness of transition can be engineered with choice of film thickness and coil pitch relative to lambda(sub eff)(0), ratio of T/T(sub c), and bias circuit inductance
Modeling a Three-Stage SQUID System in Space with the First Micro-X Sounding Rocket Flight
The Micro-X sounding rocket is a NASA funded X-ray telescope payload that
completed its first flight on July 22, 2018. This event marked the first
operation of Transition Edge Sensors (TESs) and their SQUID-based multiplexing
readout system in space. Unfortunately, due to an ACS pointing failure, the
rocket was spinning during its five minute observation period and no scientific
data was collected. However, data collected from the internal calibration
source marked a partial success for the payload and offers a unique opportunity
to study the response of TESs and SQUIDs in space. Of particular interest is
the magnetic field response of the NIST MUX06a SQUID readout system to tumbling
through Earth's magnetic field. We present a model to explain the baseline
response of the SQUIDs, which lead to a subset of pixels failing to "lock" for
the full observational period. Future flights of the Micro-X rocket will
include the NIST MUX18b SQUID system with dramatically reduced magnetic
susceptibility.Comment: 6 pages, 6 figures, LTD19 conference proceeding
Close-packed Arrays of Transition-edge X-ray Microcalorimeters with High Spectral Resolution at 5.9 keV
We present measurements of high fill-factor arrays of superconducting transition-edge x-ray microcalorimeters designed to provide rapid thermalization of the x-ray energy. We designed an x-ray absorber that is cantilevered over the sensitive part of the thermometer itself, making contact only at normal metal-features. With absorbers made of electroplated gold, we have demonstrated an energy resolution between 2.4 and 3.1 eV at 5.9 keV on 13 separate pixels. We have determined the thermal and electrical parameters of the devices throughout the superconducting transition, and, using these parameters, have modeled all aspects of the detector performance
How Well Do We (and Will We) Know Solar Neutrino Fluxes and Oscillation Parameters?
Assuming neutrino oscillations occur, the pp electron neutrino flux is
uncertain by at least a factor of two, the flux by a factor of
five, and the flux by a factor of forty-five. Calculations of the
expected results of future solar neutrino experiments (SuperKamiokande, SNO,
BOREXINO, ICARUS, HELLAZ, and HERON) are used to illustrate the extent to which
these experiments will restrict the range of the allowed neutrino mixing
parameters. We present an improved formulation of the ``luminosity constraint''
and show that at 95\% confidence limit this constraint establishes the best
available limits on the rate of creation of pp neutrinos in the solar interior
and provides the best upper limit to the neutrino flux.Comment: 37 pages, uuencoded Z-compressed postscript file (with figures);
Submitted to Physical Review
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