[en] We propose a new superconducting electronic device, which can provide amplification of low-level electrical signals at low temperatures. The device, which we call the quatratran, is based on quasiparticle trapping from a superconductor into a normal metal, coupled with normal-insulator-superconductor (NIS) tunnel junctions. Quasiparticles injected into the S electrode of a first junction are trapped in an N layer, producing excited charge carriers. This N layer is also used as the N electrode of a second NIS junction, which produces an amplified signal. We explain the principles of operation and describe the electronic characteristics. Results from test devices demonstrate the soundness of the principles. We also suggest how quatratrans can be applied to the detection of particles and radiation

[en] We present the multiplexed readout of two γ-ray microcalorimeters made from transition-edge sensors. We use a frequency-domain multiplexing scheme in which each sensor is biased at an identifying frequency. We obtain an energy resolution of about 60 eV at 60 keV for each sensor

[en] We present a design for a novel electronic refrigerator having a base temperature of about 18 mK when operating from a bath temperature as high as 1.5 K. This all-electronic refrigerator is a factor of 10⁴ smaller and lighter than dilution and adiabatic demagnetization refrigerators, and is compatible with conventional photolithographic fabrication. The refrigerator, based on the unique thermal transport properties of a normal-insulator-superconductor (NIS) tunnel function, preferentially removes electrons whose energy is higher than the Fermi energy from a normal metal. Electrons with an average energy equal to the Fermi energy are returned to the metal by a superconductor contact. Consequently, high energy thermal excitations are removed from the normal metal, thus cooling the electrons. In our configuration, the junction is deposited on a Si₃N₄ membrane of submicron thickness that thermally isolates the normal electrode from the bath. As a result, both electrons and phonons in the metal are cooled below the bath temperature. We calculate a cooling power of 2 nW at 100 mK, and a base temperature of 18 mK for a refrigerator area of about 100X100μm². Using 10⁵ such refrigerator circuits, the cooling power can be increased to 200 μW

[en] We present time-of-flight measurements of biological material ejected from bacterial spores following laser irradiation. Ion impacts are registered on a microchannel plate detector and on a Superconducting Tunnel Junction (STJ) detector. We compare mass spectra obtained with the two detectors. The STJ has better sensitivity to massive ions and also measures the energy of each ion. We show evidence that spores of different bacillus species produce distinctive mass spectra and associate the observed mass peaks with coat proteins

[en] In Section 1, we describe how the creation of quasiparticles by current flow through a normal-insulator-superconductor (NIS) junction degrades the cooling performance of the junction. Degradation occurs due to the absorption of recombination phonons in the normal electrode and due to a reduction in the cooling power. In Section 2, we describe how vibrations from a pulse tube mechanical cooler affect X-ray measurements performed with a superconducting tunnel junction

[en] We describe the design, fabrication and performance of a fully lithographically patterned magnetic microcalorimeter X-ray detector. The detector is fabricated on the same chip as a low-noise SQUID that measures the change in the magnetic sensor film's magnetization as the film is heated by absorbed X-rays. Our proof-of-principle detectors use a 100 μmx100 μm-2 μm paramagnetic Au:Er film coupled to a low-noise on-chip SQUID via a meandering superconducting pickup loop that also provides the magnetic field bias to the film. Absorption of 6 keV X-rays in the film causes heating on the order of 1 mK with a decay time of 1 ms or less, the fastest reported using a magnetic calorimeter. However, the resolution is currently poor due to poor Au:Er film properties and non-optimized coupling to the SQUID. We describe the design and fabrication of this device and present measurements of the heat capacity, decay time constant and effective thermal conductance of the microcalorimeter as a function of temperature. Because the SQUID and calorimeter are lithographically patterned on the same substrate, this technology can be readily applied to the fabrication of arrays of multiplexed magnetic microcalorimeter detectors

[en] We discuss results on the superconducting and electron-transport properties of Mn-doped Al produced by sputter deposition. The critical temperature of Al has been systematically reduced to below 50 mK by doping with 1000-3000 ppm Mn. Values of the α parameter are in the range of 450-500, indicating sharp normal-to-superconductor transitions. This material is thus of significant interest for both transition-edge sensors operating in the 100 mK regime and superconductor/insulator/superconductor and superconductor/insulator/normal devices, in the latter case where appropriately doped Al-Mn replaces the normal metal

[en] We present the multiplexed readout of two gamma-ray microcalorimeters made from transition-edge sensors. We use a frequency-domain multiplexing scheme in which each sensor is biased at an identifying frequency. We show that the energy resolution of the sensors is unaffected by multiplexing, and that crosstalk between the sensors is negligible. Our results indicate the feasibility of multiplexing 30 sensors or more to one readout line. (c) 2002 American Institute of Physics

[en] We report recent progress at NIST on Mo/Cu Transition-Edge Sensors (TESs). While the signal-band noise of our sensors agrees with theory, we observe excess high-frequency noise. We describe this noise and demonstrate that it can be strongly suppressed by a magnetic field perpendicular to the plane of the sensor. Both the excess noise and α=(T/R)(dR/dT) depend strongly on field so our results show that accurate comparisons between devices are only possible when the field is well known or constant. We also present results showing the noise performance of TES designs incorporating parallel and perpendicular normal metal bars, an array of normal metal islands, and in wedge-shaped devices. We demonstrate significant reduction of high-frequency noise with the perpendicular bar devices at the cost of reduced α. Both the bars and the magnetic field are useful noise reduction techniques for bolometers

[en] We are developing arrays of Mo/Cu transition edge sensor-based detectors for use as X-ray microcalorimeters and sub-millimeter bolometers. We have fabricated 8x8 pixel X-ray microcalorimeter arrays using surface micromachining. Surface-micromachining techniques hold the promise of scalability to much larger arrays and may allow for the integration of in-plane multiplexer elements. In this paper we describe the surface micromachining process and recent improvements in the device geometry that provide for increased mechanical strength. We also present X-ray and heat pulse spectra collected using these detectors