Bulletin of the American Physical Society
2007 APS March Meeting
Volume 52, Number 1
Monday–Friday, March 5–9, 2007; Denver, Colorado
Session W6: Keithley Award |
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Sponsoring Units: GIMS Chair: Stan Tozer, National High Magnetic Field Laboratory, Florida State University Room: Colorado Convention Center 207 |
Thursday, March 8, 2007 2:30PM - 3:06PM |
W6.00001: Keithley Award Talk Invited Speaker: Superconducting transition-edge sensors (TES) operated at temperatures below 1 K are a sensitive tool for the detection of electromagnetic radiation from microwaves through gamma rays, and for the measurement of the energy of particle interactions and nuclear decays. They have evolved beyond the research and development phase, and they are being used in applications as diverse as astronomy, nuclear and particle physics, and materials science. The low noise, low source impedance, and low operating temperature of superconducting quantum interference devices (SQUIDs) make them the preamplifier of choice for TES devices. In order to realize their full potential, it has been necessary to develop arrays of thousands of SQUID-coupled transition-edge sensors. Due to constraints on cryogenic wiring and circuit complexity, SQUID multiplexing is necessary to realize these advances. In this talk, I will describe the development of large arrays of TES detectors integrated with multiplexed SQUID amplifiers. SQUID multiplexers use an orthogonal basis set (usually time- or frequency-division) to encode the signal from many input channels into a single wire. I will discuss both fundamental limits and practical issues of implementation, including bandwidth-limiting filters, power dissipation, and crosstalk. I will highlight work done by our group at the National Institute of Standards and Technology to develop time-division multiplexed arrays of thousands of SQUID amplifiers, and collaborations with different groups to integrate them into large arrays of TES sensors for a variety of applications. I will also discuss future trends, including the development of microwave techniques to read out even larger arrays of SQUID amplifiers in high-Q resonant circuits. [Preview Abstract] |
Thursday, March 8, 2007 3:06PM - 3:42PM |
W6.00002: Cold Probes of the Hot Universe Invited Speaker: High-resolution x-ray spectroscopy is becoming a powerful tool for studying the hot (1 - 100 MK) and dynamic universe. The grating spectrometers on the XMM and Chandra satellites have sparked a new era in x-ray astronomy, but there is need to deploy instrumentation that can provide higher spectral resolution with high throughput in the Fe-K band (around 6 keV) and for extended sources. These new spectrometers will be based on arrays of microcalorimeters operated at 0.1 K and below. A microcalorimeter measures a small amount of heat in a weakly heatsunk thermal mass by sensing a temperature change in the presence of thermodynamically unavoidable temperature fluctuations. Low temperature operation is required in order to minimize this thermal noise and to reduce the heat capacity. The most advanced microcalorimeter technology to date is based on using a temperature-dependent resistance for the thermometer element, either a semiconductor thermistor or a superconducting transition-edge sensor (TES). At Goddard, we have been developing microcalorimeters for x-ray astrophysics since our pioneering work in 1984, and we have pursued both silicon and TES technology, and optimizations for different telescopes and energy bands. In our latest TES design, we have achieved a resolution of 2.5 eV at 6 keV. I will review the microcalorimeter research at Goddard and will discuss prospects for getting such an instrument deployed in orbit. [Preview Abstract] |
Thursday, March 8, 2007 3:42PM - 4:18PM |
W6.00003: The Cosmic Microwave Background Invited Speaker: Measurements of the Cosmic Microwave Background (CMB) provide our earliest direct information about the evolving Universe. This talk will begin with a summary of how the CMB was produced and why it is important. The focus will than shift to the nature of the experimental challenge of extracting Cosmological information from the CMB. Examples will be given of technology development in small-scale experiments leading to major space missions which produce definitive data sets. The millimeter-wave spectral range of the signals corresponds to the crossover between coherent (radio) techniques and bolometric (optical) techniques. These challenges have stimulated enormous development of bolometric detectors, which are used to measure both the spectrum and the anisotropy of the CMB. The next generation of CMB experiments will require a new generation of bolometric detectors in large format arrays. This year, the Keithly Prize is given to Kent Irwin for ideas that have made this next step possible. [Preview Abstract] |
Thursday, March 8, 2007 4:18PM - 4:54PM |
W6.00004: Dark Matter Invited Speaker: |
Thursday, March 8, 2007 4:54PM - 5:30PM |
W6.00005: Quantum Calorimeter Gamma-ray Detectors: New Tools for Non-proliferation Invited Speaker: High resolution $\gamma$-ray spectroscopy is an important tool for non-destructive analysis of nuclear materials and is often used by safeguards inspectors to help verify the inventories of nuclear materials held around the world. The energy spectrum of photons emitted from isotopes of uranium or plutonium in the $40-1000$ keV energy range give unique signatures that, if accurately measured, give inspectors important information about the age and enrichment of the material and therefore its intended purpose. In this talk I will describe recent work by a team of researchers from the Unversity of Denver, the National Institute of Standards and Technology, and Los Alamos National Laboratory on $\gamma$-ray spectrometers with more than an order of magnitude improvement in energy resolution over standard techniques. The heart of this improved tool for non-proliferation is a microcalorimeter $\gamma$-ray detector that combines a micromachined thermal isolation structure with a bulk absorber and a highly sensitive superconducting transition-edge thermometer optimized for operation well below $1$ K. In the last several months, we have assembled and tested arrays of these microcalorimeters, with many detector pixels on a single chip. When read out with SQUID multiplexers, these arrays dramatically increase the speed of data collection, allowing ultra-high resolution $\gamma$-ray spectra to be acquired in roughly the same time needed for traditional detector technologies. In addition to presenting high-resolution $\gamma$-ray spectra of nuclear materials such as plutonium, I will describe the physics of the microcalorimeter, which ranges from the lifetime of quasiparticles in bulk superconductors to the thermal properties of glue. [Preview Abstract] |
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