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Full-Text Articles in Physics
A Grazing Incidence X-Ray Streak Camera For Ultrafast, Single-Shot Measurements, J. Feng, K. Engelhorn, B. I. Cho, H. J. Lee, M. Greaves, Christopher P. Weber, R. W. Falcone, H. A. Padmore, P. A. Heimann
A Grazing Incidence X-Ray Streak Camera For Ultrafast, Single-Shot Measurements, J. Feng, K. Engelhorn, B. I. Cho, H. J. Lee, M. Greaves, Christopher P. Weber, R. W. Falcone, H. A. Padmore, P. A. Heimann
Physics
An ultrafast x-ray streak camera has been realized using a grazing incidence reflection photocathode. X-rays are incident on a gold photocathode at a grazing angle of 20° and photoemitted electrons are focused by a large aperture magnetic solenoid lens. The streak camera has high quantum efficiency, 600 fs temporal resolution, and 6 mm imaging length in the spectral direction. Its single shot capability eliminates temporal smearing due to sweep jitter, and allows recording of the ultrafast dynamics of samples that undergo nonreversible changes.
Influence Of Functionalized Fullerene Structure On Polymer Photovoltaic Degradation, Brian H. Johnson, Enaanake Allagoa, Robert L. Thomas, Gregory Stettler, Marianne Wallis, Justn H. Peel, Thorsteinn Adalsteinsson, Brian J. Mcnelis, Richard P. Barber Jr.
Influence Of Functionalized Fullerene Structure On Polymer Photovoltaic Degradation, Brian H. Johnson, Enaanake Allagoa, Robert L. Thomas, Gregory Stettler, Marianne Wallis, Justn H. Peel, Thorsteinn Adalsteinsson, Brian J. Mcnelis, Richard P. Barber Jr.
Physics
The time dependence of device performance has been measured for photocells using blends containing the conjugated polymer, poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) with two different functionalized C60 electron acceptor molecules: commercially available [6,6]-phenyl C61 butyric acid methyl ester (PCBM) or [6,6]-phenyl C61 butyric acid octadecyl ester (PCBOD) produced in this laboratory. Performance was characterized by the short-circuit current output of the devices, with the time dependence of PCBM samples typically degrading exponentially. Variations in the characteristic lifetime of the devices were observed to depend on the molar fraction of the electron acceptor molecules (calculated with respect to the MEH-PPV monomer fraction). In comparison …
Josephson Scanning Tunneling Microscopy: A Local And Direct Probe Of The Superconducting Order Parameter, Richard P. Barber Jr., Hikari Kimura, Shuhei Ono, Yoichi Ando, Robert C. Dynes
Josephson Scanning Tunneling Microscopy: A Local And Direct Probe Of The Superconducting Order Parameter, Richard P. Barber Jr., Hikari Kimura, Shuhei Ono, Yoichi Ando, Robert C. Dynes
Physics
Direct measurements of the superconducting superfluid on the surface of vacuum-cleaved Bi2Sr2CaCu2O8+ BSCCO samples are reported. These measurements are accomplished via Josephson tunneling into the sample using a scanning tunneling microscope STM equipped with a superconducting tip. The spatial resolution of the STM of lateral distances less than the superconducting coherence length allows it to reveal local inhomogeneities in the pair wave function of the BSCCO. Instrument performance is demonstrated first with Josephson measurements of Pb films followed by the layered superconductor NbSe2. The relevant measurement parameter, the Josephson ICRN product, is discussed within the context of both BCS superconductors …
Emergence Of The Persistent Spin Helix In Semiconductor Quantum Wells, J. D. Koralek, Christopher P. Weber, J. Orenstein, B. Andrei Bernevig, Shou-Cheng Zhang, S. Mack, D. D. Awschalom
Emergence Of The Persistent Spin Helix In Semiconductor Quantum Wells, J. D. Koralek, Christopher P. Weber, J. Orenstein, B. Andrei Bernevig, Shou-Cheng Zhang, S. Mack, D. D. Awschalom
Physics
According to Noether’s theorem1, for every symmetry in nature there is a corresponding conservation law. For example, invariance with respect to spatial translation corresponds to conservation of momentum. In another well-known example, invariance with respect to rotation of the electron’s spin, or SU(2) symmetry, leads to conservation of spin polarization. For electrons in a solid, this symmetry is ordinarily broken by spin–orbit coupling, allowing spin angular momentum to flow to orbital angular momentum. However, it has recently been predicted that SU(2) can be achieved in a two-dimensional electron gas, despite the presence of spin–orbit coupling2. The …
Scanning Josephson Tunneling Microscopy Of Single Crystal Bi2Sr2Cacu2O8+Δ With A Conventional Superconducting Tip, Richard P. Barber Jr., Hikari Kimura, Shuhei Ono, Yoichi Ando, Robert C. Dynes
Scanning Josephson Tunneling Microscopy Of Single Crystal Bi2Sr2Cacu2O8+Δ With A Conventional Superconducting Tip, Richard P. Barber Jr., Hikari Kimura, Shuhei Ono, Yoichi Ando, Robert C. Dynes
Physics
We have performed both Josephson and quasiparticle tunneling in vacuum tunnel junctions formed between a conventional superconducting scanning tunneling microscope tip and overdoped Bi2Sr2CaCu2O8+δ single crystals. A Josephson current is observed with a peak centered at a small finite voltage due to the thermal-fluctuation-dominated superconducting phase dynamics. Josephson measurements at different surface locations yield local values for the Josephson IcRn product. Corresponding energy gap measurements were also performed and a surprising inverse correlation was observed between the local IcRn product and the local energy gap.
Dancing With Physics, Richard P. Barber Jr., David Popalisky
Dancing With Physics, Richard P. Barber Jr., David Popalisky
Physics
Teaching physics by way of the forces on the human body experienced during dance can be an effective way to bring Newton's laws to life.
Nondiffusive Spin Dynamics In A Two-Dimensional Electron Gas, Christopher P. Weber, J. Orenstein, B. Andrei Bernevig, Shou-Cheng Zhang, Jason Stephens, D. D. Awschalom
Nondiffusive Spin Dynamics In A Two-Dimensional Electron Gas, Christopher P. Weber, J. Orenstein, B. Andrei Bernevig, Shou-Cheng Zhang, Jason Stephens, D. D. Awschalom
Physics
We describe measurements of spin dynamics in the two-dimensional electron gas in GaAs=GaAlAs quantum wells. Optical techniques, including transient spin-grating spectroscopy, are used to probe the relaxation rates of spin polarization waves in the wave vector range from zero to 6 x 104 cm-1. We find that the spin polarization lifetime is maximal at a nonzero wave vector, in contrast with expectations based on ordinary spin diffusion, but in quantitative agreement with recent theories that treat diffusion in the presence of spin-orbit coupling
Negative Magnetoresistance, Negative Electroresistance, And Metallic Behavior On The Insulating Side Of The Two-Dimensional Superconductor-Insulator Transition In Granular Pb Films, Richard P. Barber Jr., Shih-Ying Hsu, James M. Valles Jr., Robert C. Dynes, Rolfe Eldridge Glover Iii
Negative Magnetoresistance, Negative Electroresistance, And Metallic Behavior On The Insulating Side Of The Two-Dimensional Superconductor-Insulator Transition In Granular Pb Films, Richard P. Barber Jr., Shih-Ying Hsu, James M. Valles Jr., Robert C. Dynes, Rolfe Eldridge Glover Iii
Physics
Granular Pb thin films on the insulating side of the two-dimensional superconductor-insulator transition are observed to exhibit a large negative magnetoresistance and electroresistance change in resistance with electric field at low temperatures. At high measurement voltages and low temperatures, the film resistances become temperature independent creating a "metallic" state. These phenomena are explained as manifestations of transport due to intergranular quasiparticle tunneling. This explanation might also provide insights into the similar behavior observed in other superconductors.
Superconducting Transition Edge Sensor Using Dilute Almn Alloys, S. W. Deiker, W. Doriese, G. C. Hilton, K. D. Hilton, W. H. Rippard, J. N. Ullom, L. R. Vale, S. T. Ruggiero, A. Williams, Betty A. Young
Superconducting Transition Edge Sensor Using Dilute Almn Alloys, S. W. Deiker, W. Doriese, G. C. Hilton, K. D. Hilton, W. H. Rippard, J. N. Ullom, L. R. Vale, S. T. Ruggiero, A. Williams, Betty A. Young
Physics
We have fabricated a bolometer using a transition-edge sensor (TES) made of Al doped with Mn to suppress the superconducting critical temperature (Tc) of Al from ∼1Kto∼100mK. The resulting detector exhibits low-frequency noise consistent with theory, with a noise-equivalent power of 7.5×10−18W/√Hz. The addition of Mn impurities did not significantly increase the heat capacity of the TES. In addition, the detector is surprisingly insensitive to applied magnetic fields. The use of AlMn alloy films in arrays of TES detectors has advantages in simplicity of fabrication when compared to traditional bilayer fabrication techniques.
New Results From The Cryogenic Dark Matter Search Experiment, D. S. Akerib, J. Alvaro-Dean, M. S. Armel, M. J. Attisha, L. Baudis, D. A. Bauer, A. I. Bolozdynya, P. L. Brink, R. Bunker, Blas Cabrera, D. O. Caldwell, J. P. Castle, C. L. Chang, R. M. Clarke, M. B. Crisler, P. Crushman, A. K. Davies, R. Dixon, D. D. Driscoll, L. Duong, J. Emes, R. Ferril, R. J. Gaitskell, S. R. Golwala, M. Haldeman, J. Hellmig, M. Hennessey, D. Holmgren, M. E. Huber, S. Kamat, M. Kurylowicz, A. Lu, R. Mahapatra, V. Mandic, J. M. Martinis, P. Meunier, N. Mirabolfathi, S. W. Nam, H. Nelson, R. Nelson, R. W. Ogburn, J. Perales, T. A. Perera, M. C. Perillo Isaac, W. Rau, A. Reisetter, R. R. Ross, T. Saab, B. Sadoulet, J. Sander, C. Savage, R. W. Schnee, D. N. Seitz, T. A. Shutt, G. Smith, A. L. Spadafora, J.-P. F. Thompson, A. Tomada, G. Wang, S. Yellin, Betty A. Young
New Results From The Cryogenic Dark Matter Search Experiment, D. S. Akerib, J. Alvaro-Dean, M. S. Armel, M. J. Attisha, L. Baudis, D. A. Bauer, A. I. Bolozdynya, P. L. Brink, R. Bunker, Blas Cabrera, D. O. Caldwell, J. P. Castle, C. L. Chang, R. M. Clarke, M. B. Crisler, P. Crushman, A. K. Davies, R. Dixon, D. D. Driscoll, L. Duong, J. Emes, R. Ferril, R. J. Gaitskell, S. R. Golwala, M. Haldeman, J. Hellmig, M. Hennessey, D. Holmgren, M. E. Huber, S. Kamat, M. Kurylowicz, A. Lu, R. Mahapatra, V. Mandic, J. M. Martinis, P. Meunier, N. Mirabolfathi, S. W. Nam, H. Nelson, R. Nelson, R. W. Ogburn, J. Perales, T. A. Perera, M. C. Perillo Isaac, W. Rau, A. Reisetter, R. R. Ross, T. Saab, B. Sadoulet, J. Sander, C. Savage, R. W. Schnee, D. N. Seitz, T. A. Shutt, G. Smith, A. L. Spadafora, J.-P. F. Thompson, A. Tomada, G. Wang, S. Yellin, Betty A. Young
Physics
Using improved Ge and Si detectors, better neutron shielding, and increased counting time, the Cryogenic Dark Matter Search (CDMS) experiment has obtained stricter limits on the cross section of weakly interacting massive particles (WIMPs) elastically scattering from nuclei. Increased discrimination against electromagnetic backgrounds and reduction of the neutron flux confirm WIMP-candidate events previously detected by CDMS were consistent with neutrons and give limits on spin-independent WIMP interactions which are >2× lower than previous CDMS results for high WIMP mass, and which exclude new parameter space for WIMPs with mass between 8 and 20 GeV/c2 .
Resistive Transitions In Quench-Condensed Bi Films Near A Normal-Metal Ground Plane, Richard P. Barber Jr., Ben Kain
Resistive Transitions In Quench-Condensed Bi Films Near A Normal-Metal Ground Plane, Richard P. Barber Jr., Ben Kain
Physics
We report observations of the zero-field resistive transitions of superconducting quench-condensed Bi0.97Tl0.03 films both near electrically isolated normal-metal ground planes and on clean fire-polished glass. Transition temperatures, obtained by fitting the data with the two-dimensional Aslamazov-Larkin theory of fluctuation conductance, were found to be significantly enhanced for films deposited over ground planes versus those deposited onto insulating substrates. Conductivity enhancement due to superconducting fluctuations was found to be much less than expected for the thinnest samples. This suppression was coincident with broadened superconductor transitions that are consistent with nonuniform sample thickness. Sufficiently thick films showed reasonable agreement with both the …
Exclusion Limits On The Wimp-Nucleon Cross Section From The Cryogenic Dark Matter Search, D. Abrams, D. S. Akerib, M. S. Armel-Funkhouser, L. Baudis, D. A. Bauer, A. Bolozdynya, P. L. Brink, R. Bunker, B. Cabrera, D. O. Caldwell, J. P. Castle, C. L. Chang, R. M. Clarke, M. B. Crisler, R. Dixon, D. Driscoll, S. Eichblatt, R. J. Gaitskell, S. R. Golwala, E. E. Haller, J. Hellmig, D. Holmgren, M. E. Huber, S. Kamat, A. Lu, V. Mandic, J. M. Martinis, P. Meunier, S. W. Nam, H. Nelson, T. A. Perera, M. C. Perillo Isaac, W. Rau, R. R. Ross, T. Saab, B. Sadoulet, J. Sander, R. W. Schnee, T. Shutt, A. Smith, A. H. Sonnenschein, A. L. Spadafora, G. Wang, S. Yellin, Betty A. Young
Exclusion Limits On The Wimp-Nucleon Cross Section From The Cryogenic Dark Matter Search, D. Abrams, D. S. Akerib, M. S. Armel-Funkhouser, L. Baudis, D. A. Bauer, A. Bolozdynya, P. L. Brink, R. Bunker, B. Cabrera, D. O. Caldwell, J. P. Castle, C. L. Chang, R. M. Clarke, M. B. Crisler, R. Dixon, D. Driscoll, S. Eichblatt, R. J. Gaitskell, S. R. Golwala, E. E. Haller, J. Hellmig, D. Holmgren, M. E. Huber, S. Kamat, A. Lu, V. Mandic, J. M. Martinis, P. Meunier, S. W. Nam, H. Nelson, T. A. Perera, M. C. Perillo Isaac, W. Rau, R. R. Ross, T. Saab, B. Sadoulet, J. Sander, R. W. Schnee, T. Shutt, A. Smith, A. H. Sonnenschein, A. L. Spadafora, G. Wang, S. Yellin, Betty A. Young
Physics
The Cryogenic Dark Matter Search (CDMS) employs low-temperature Ge and Si detectors to search for weakly interacting massive particles (WIMPs) via their elastic-scattering interactions with nuclei while discriminating against interactions of background particles. For recoil energies above 10 keV, events due to background photons are rejected with >99.9% efficiency, and surface events are rejected with >95% efficiency. The estimate of the background due to neutrons is based primarily on the observation of multiple-scatter events that should all be neutrons. Data selection is determined primarily by examining calibration data and vetoed events. Resulting efficiencies should be accurate to ∼10%. Results of …
Tuning The Transition Temperature Of Superconducting Ag/Pb Films Via The Proximity Effect, Richard P. Barber Jr., Ben Kain, S. R. Khan
Tuning The Transition Temperature Of Superconducting Ag/Pb Films Via The Proximity Effect, Richard P. Barber Jr., Ben Kain, S. R. Khan
Physics
We report measurements of the transition temperature (TC) of superconducting films composed of various combinations of Ag and Pb layers. For samples with good electrical contact between the layers, the measured TC values show reasonable agreement with the Cooper model of the proximity effect. In poorly coupled samples, the normal layers appear to cause little if any suppression of the TC. We present a simple predictive expression for TC as a function of Ag content.
Effect Of Implanted Metal Impurities On Superconducting Tungsten Films, Betty A. Young, T. Saab, Blas Cabrera, A. J. Miller, P. L. Brink, J. P. Castle
Effect Of Implanted Metal Impurities On Superconducting Tungsten Films, Betty A. Young, T. Saab, Blas Cabrera, A. J. Miller, P. L. Brink, J. P. Castle
Physics
The superconducting transition temperature of more than 30 thin-film tungsten samples was measured using a dilution refrigerator. The samples were fabricated using a 99.999% pure tungsten target and a dc magnetron sputtering system. Individual films were then doped with metal impurity ions using an accurate ion implantation technique. The effect of the metal–ion doping on the superconducting transition temperature was measured for samples with superconducting transitions in the range of 40–150 mK. Magnetic dopant species including Ni, Co, and Fe resulted in suppressed values of the tungsten Tc. The suppression was linear with increasing dopant concentration, for concentrations …
A Testing Strategy For The Mass Production Of Cdms Ii Detectors, D. Driacoll, D. S. Akerib, D. Abrams, D. Bauer, P. L. Brink, B. Cabrera, J. P. Castle, C. Chang, M. B. Crisler, R. J. Gaitskell, J. Hellmig, S. Kamat, V. Mandic, P. Meunier, T. A. Perera, M. C. Perillo Isaac, W. Rau, T. Saab, B. Sadoulet, R. W. Schnee, D. N. Seitz, G. Wang, Betty A. Young
A Testing Strategy For The Mass Production Of Cdms Ii Detectors, D. Driacoll, D. S. Akerib, D. Abrams, D. Bauer, P. L. Brink, B. Cabrera, J. P. Castle, C. Chang, M. B. Crisler, R. J. Gaitskell, J. Hellmig, S. Kamat, V. Mandic, P. Meunier, T. A. Perera, M. C. Perillo Isaac, W. Rau, T. Saab, B. Sadoulet, R. W. Schnee, D. N. Seitz, G. Wang, Betty A. Young
Physics
The Cryogenic Dark Matter Search (CDMS) employs detectors which are capable of simultaneously measuring the ionization and phonon energies deposited by a particle collision. These detectors are 1-cm-thick, 7-cm-diameter crystals of either germanium or silicon with a thin film of aluminum and tungsten patterned on the surface. This presentation discusses the testing regimen that a typical CDMS detector undergoes before it gets approval for final installation at the CDMS II deep site in Soudan, MN which will come online in early 2002. Now that our technology is relatively stable, the main focus of our test facilities is to provide quality …
Crossover From Phase Fluctuation To Amplitude-Dominated Superconductivity: A Model System, Richard P. Barber Jr., L. Merchant, J. Ostrick, Robert C. Dynes
Crossover From Phase Fluctuation To Amplitude-Dominated Superconductivity: A Model System, Richard P. Barber Jr., L. Merchant, J. Ostrick, Robert C. Dynes
Physics
We have experimentally studied a model system that demonstrates the crossover from a superconductor that is dominated by phase fluctuations, to one in which the amplitude of the order parameter is the controlling influence on Tc. This model system is comprised of two-dimensional granular Pb with an overlayer of Ag. The system displays many aspects of the phase diagram of the concentration dependence of Tc in the high-Tc superconductors, and this crossover has been applied to explain the phase diagram in that case. We point out the similarities and differences between the model system presented in this paper and the …
Low-Frequency Crossover Of The Fractional Power-Law Conductivity In Srruo3, J. S. Dodge, Christopher P. Weber, J. Corson, J. Orenstein, Z. Schlesinger, J. W. Reiner, M. R. Beasley
Low-Frequency Crossover Of The Fractional Power-Law Conductivity In Srruo3, J. S. Dodge, Christopher P. Weber, J. Corson, J. Orenstein, Z. Schlesinger, J. W. Reiner, M. R. Beasley
Physics
We combine the results of terahertz time-domain spectroscopy with far-infrared transmission and reflectivity to obtain the conductivity of SrRuO 3 over an unprecedented continuous range in frequency, allowing us to characterize the approach to zero frequency as a function of temperature. We show that the conductivity follows a simple phenomenological form, with an analytic structure fundamentally different from that predicted by the standard theory of metals.
Superconductor-Insulator Transition In Granular Pb Films Near A Superconducting Ground Plane, Richard P. Barber Jr., S. R. Khan, Eric Morre Pedersen, Ben Kain, A. J. Jordan
Superconductor-Insulator Transition In Granular Pb Films Near A Superconducting Ground Plane, Richard P. Barber Jr., S. R. Khan, Eric Morre Pedersen, Ben Kain, A. J. Jordan
Physics
We report observations of the zero-field superconductor-insulator transition in granular quench-condensed Pb for samples within 10-15 nm of relatively thick superconducting ground planes. Resistance vs temperature measurements of sufficiently thick Pb samples exhibit broadened superconductor transitions consistent with previous results on clean dielectric substrates. The lack of any measurable influence by the superconducting planes on the Pb film resistance is discussed within the context of zero-field vortex-antivortex unbinding explanations for the transition broadening.
Measurement Of TC Suppression In Tungsten Using Magnetic Impurities, Betty A. Young, T. Saab, Blas Cabrera, J. J. Cross, R. M. Clarke, R. A. Abusaidi
Measurement Of TC Suppression In Tungsten Using Magnetic Impurities, Betty A. Young, T. Saab, Blas Cabrera, J. J. Cross, R. M. Clarke, R. A. Abusaidi
Physics
We have measured the effects of dilute magnetic-atom doping on the superconducting transition temperature of tungsten thin films. Our “Tc tuning” technique is accurate, precise, and simple. Experiments were performed using dc-magnetron-sputtered tungsten films with undoped values of Tc in the range of 70–150 mK. The magnetic-atom doping was achieved using ion implantation. Specific Tc suppressions of between 5% and 65% were targeted and observed in this study. The transition width of each undoped sample was ≈1 mK and the transition widths remained sharp after implantation with 56Fe+ ions. Our data are in good agreement …
Charge Dynamics In The Half-Metallic Ferromagnet Cro2, E. J. Singley, Christopher P. Weber, D. N. Basov, A. Barry, J. M. D. Coey
Charge Dynamics In The Half-Metallic Ferromagnet Cro2, E. J. Singley, Christopher P. Weber, D. N. Basov, A. Barry, J. M. D. Coey
Physics
Infrared spectroscopy is used to investigate the electronic structure and charge carrier relaxation in crystalline films of CrO2 which is the simplest of all half-metallic ferromagnets. Chromium dioxide is a bad metal at room temperature but it has a remarkably low residual resistivity (<5 >μΩ cm) despite the small spectral weight associated with free carrier absorption. The infrared measurements show that low residual resistivity is due to the collapse of the scattering rate at ω<2000 >cm-1. The blocking of the relaxation channels at low v and T can be attributed to the unique electronic structure of a …
Spume Drops Produced By The Wind Tearing Of Wave Crests, Richard P. Barber Jr., Magdalena Anguelova, Jin Wu
Spume Drops Produced By The Wind Tearing Of Wave Crests, Richard P. Barber Jr., Magdalena Anguelova, Jin Wu
Physics
The wind tearing of breaking wave crests produces spume drops. The authors report preliminary laboratory data from direct and unambiguous observation of this process under various wind conditions using a video imaging technique. Results include the size distribution and production rates of these drops. The curves for production rates at different wind speeds merge effectively when normalized by the number of breaking events. This confirms that wave breaking occurrence, not the wind speed, is a dominant factor in spume production.
Saturation In “Nonmagnetic” Stainless Steel, Christopher P. Weber, J. Fajans
Saturation In “Nonmagnetic” Stainless Steel, Christopher P. Weber, J. Fajans
Physics
Scientific equipment often uses “nonmagnetic” stainless steel, relying on the steel’s nonmagnetic behavior to leave external magnetic fields unaltered. However, stainless steel’s permeability can rise significantly when it is welded or machined, possibly perturbing an external field. Such perturbations will diminish well above the stainless steel’s saturation point. The authors measured the permeability of both welded and machined 304 stainless steel as a function of an external magnetic field, and found that both saturate at fields of approximately 0.25 T.
Sea Brightness Temperature And Effects Of Spray And Whitecaps, Richard P. Barber Jr., Jin Wu
Sea Brightness Temperature And Effects Of Spray And Whitecaps, Richard P. Barber Jr., Jin Wu
Physics
Following the approach of Tang [1974], the microwave brightness of the sea surface is recalculated with recent parameterizations in terms of wind velocity for the slope distribution and whitecap coverage of the sea surface and the contribution of sea spray. The difference between this revised calculation with no free parameters and the earlier one becomes more significant as the wind velocity increases; it reaches 10 K or more at a wind velocity of 20 m s-1. Present predictions compare favorably with experimental results, suggesting that this model does include the essential physical mechanisms.
Charge Collection And Trapping In Low‐Temperature Silicon Detectors, M. J. Penn, Brian L. Dougherty, Blas Cabrera, R. M. Clarke, Betty A. Young
Charge Collection And Trapping In Low‐Temperature Silicon Detectors, M. J. Penn, Brian L. Dougherty, Blas Cabrera, R. M. Clarke, Betty A. Young
Physics
Charge collection efficiency measurements in silicon detectors at low temperature (T < 0.5 K) and low applied electric field (E=0.1–100 V/cm) were performed using a variety of high‐purity, p‐type silicon samples with room‐temperature resistivity in the range 2–40 kΩ cm. Good charge collection under these conditions of low temperature and low electric field is necessary for background suppression, through the simultaneous measurement of phonons and ionization, in a very low event rate dark matter search or neutrino physics experiment. Charge loss due to trapping during drift is present in some samples, but the data suggest that another charge–loss mechanism is also important. We present results which indicate that, for 60 keV energy depositions, a significant fraction of the total charge loss by trapping occurs in the initial electron‐hole cloud near the event location which may briefly act as a shielded, field‐free region. In addition, measurements of the lateral size, transverse to the applied electric field, of the initial electron‐hole cloud indicate large transverse diffusion lengths. At the lowest fields a lateral diameter on the order of 1 mm is found in a detector ∼5 mm thick.
A Quasiparticle Trap Assisted Transition Edge Sensor For Phonon Mediated Particle Detection, K. D. Irwin, S. W. Nam, Blas Cabrera, B. Chugg, Betty A. Young
A Quasiparticle Trap Assisted Transition Edge Sensor For Phonon Mediated Particle Detection, K. D. Irwin, S. W. Nam, Blas Cabrera, B. Chugg, Betty A. Young
Physics
ABSTRACT We have demonstrated the operation of composite superconducting tungsten and aluminum transition‐edge sensors which take advantage of quasiparticle trapping and electrothermal feedback. We call these devices W/Al QETs (quasiparticle‐trap‐assisted electrothermal feedback transition‐edge sensors). The quasiparticle trapping mechanism makes it possible to instrument large surface areas without increasing sensor heat capacity, thus allowing larger absorbers and reducing phonon collection times. The sensor consists of a 30‐nm‐thick superconducting tungsten thin film with Tc∼80 mK deposited on a high‐purity silicon substrate. The W film is patterned into 200 parallel lines segments, each 2 μm wide and 800 μm long. Eight …
Ion‐Implanted Charge Collection Contacts For High Purity Silicon Detectors Operated At 20 Mk, Betty A. Young, K. M. Yu
Ion‐Implanted Charge Collection Contacts For High Purity Silicon Detectors Operated At 20 Mk, Betty A. Young, K. M. Yu
Physics
We have developed a technique for fabricating high resolution, ohmic contacts for cryogenic silicon detectors operated at temperatures well below 1 K. In this paper, we give a detailed description of the techniques used to fabricate these boron‐implanted contacts, and present characterization data obtained on 24 test samples studied during the design phase of our program. We then describe the fabrication and operation of a 23 g prototype silicon hybrid detector which simultaneously senses both the phonons and ionization produced by a single event, and which incorporates these new contacts into its design. Finally, we present data obtained using a …
Collection Of Athermal Phonons Into Doped Germanium Thermistors Using Quasiparticle Trapping, S. M. Grannan, Betty A. Young, Andrew E. Lange, S. Labov, Bernard Sadoulet, J. Emes, Eugene E. Haller
Collection Of Athermal Phonons Into Doped Germanium Thermistors Using Quasiparticle Trapping, S. M. Grannan, Betty A. Young, Andrew E. Lange, S. Labov, Bernard Sadoulet, J. Emes, Eugene E. Haller
Physics
We have developed a low‐temperature particle detector that uses a novel quasiparticle trapping mechanism to funnel athermal phonon energy from an 80 mg Ge absorber into a 1.6 mg doped Ge thermistor via a superconducting Al film. We report on pulse height spectra obtained at 320 mK by scanning a 241Am alpha source along the device, and show that up to 20% of the energy deposited in the Ge absorber by a 5.5 MeV alpha particle interaction can be collected into a thermistor via quasiparticle trapping. We show that this device is sensitive to the position of an alpha …
Tunneling Into Granular Pb Films In The Superconducting And Insulating Regimes, Richard P. Barber Jr., L. Merchant, Porta Arthur La, Robert C. Dynes
Tunneling Into Granular Pb Films In The Superconducting And Insulating Regimes, Richard P. Barber Jr., L. Merchant, Porta Arthur La, Robert C. Dynes
Physics
Tunneling measurements have been performed on both sides of the insulator-superconductor transition in quench-condensed granular Pb films. The results indicate that the Pb film consists of fully superconducting grains with essentially bulk values for the superconducting energy gap and transition temperature, even when the film exhibits insulating behavior in transport measurements. The density of states inferred from measurements in perpendicular magnetic field are consistent with magnetic spin-flip broadening.
Low-Field Magnetoresistance In Granular Pb Films Near The Insulator-Superconductor Transition, Richard P. Barber Jr., Robert C. Dynes
Low-Field Magnetoresistance In Granular Pb Films Near The Insulator-Superconductor Transition, Richard P. Barber Jr., Robert C. Dynes
Physics
We have studied the insulator-superconductor transition in quench-condensed granular Pb films from 0.1 to 10 K. Resistance measurements were made in zero magnetic field and low noise conditions. Magnetoresistance measurements were also performed for low magnetic fields (less than 100 G). The magnetoresistance results on the superconducting side of the transition suggest that we are directly probing the finite length scales associated with the range of phase coherence in these granular materials.
Simultaneous High Resolution Meausurement Of Phonons And Ionization Created By Particle Interactions In A 60 G Germanium Crystal At 25 Mk, Tom Shutt, N. Wang, B. Ellman, Y. Giraud-Héraud, C. Stubbs, Peter D. Barnes Jr., A. Cummings, Angela Da Silva, John Emes, Eugene E. Haller, Andrew E. Lange, J. Rich, R. R. Ross, B. Sadoulet, G. Smith, W. Stockwell, S. White, Betty A. Young, D. Yvon
Simultaneous High Resolution Meausurement Of Phonons And Ionization Created By Particle Interactions In A 60 G Germanium Crystal At 25 Mk, Tom Shutt, N. Wang, B. Ellman, Y. Giraud-Héraud, C. Stubbs, Peter D. Barnes Jr., A. Cummings, Angela Da Silva, John Emes, Eugene E. Haller, Andrew E. Lange, J. Rich, R. R. Ross, B. Sadoulet, G. Smith, W. Stockwell, S. White, Betty A. Young, D. Yvon
Physics
We demonstrate simultaneous high energy resolution (rms≊800 eV) measurements of ionization and phonons created by particle interactions in a semiconductor crystal of macroscopic size (60 g germanium) at 25 mK. We present first studies of charge collection at biases below 1 V/cm, and find that, contrary to commonly held opinion, the full recoil energy of particle interactions is recovered as phonons when charge trapping is negligible. We also report an unanticipated correlation between charge collection and phonon energy at very low bias, and discuss this effect in terms of charge trapping.