Showing 1–7 of 7 results for author: Reed, W

Citizen CATE 2024: Extending Totality During the 8 April 2024 Total Solar Eclipse with a Distributed Network of Community Participants

Authors: Sarah A. Kovac, Amir Caspi, Daniel B. Seaton, Paul Bryans, Joan R. Burkepile, Sarah J. Davis, Craig E. DeForest, David Elmore, Sanjay Gosain, Rebecca Haacker, Marcus Hughes, Jason Jackiewicz, Viliam Klein, Derek Lamb, Valentin Martinez Pillet, Evy McUmber, Ritesh Patel, Kevin Reardon, Willow Reed, Anna Tosolini, Andrei E. Ursache, John K. Williams, Padma A. Yanamandra-Fisher, Daniel W. Zietlow, John Carini , et al. (218 additional authors not shown)

Abstract: The Citizen CATE 2024 next-generation experiment placed 43 identical telescope and camera setups along the path of totality during the total solar eclipse (TSE) on 8 April 2024 to capture a 60-minute movie of the inner and middle solar corona in polarized visible light. The 2024 TSE path covered a large geographic swath of North America and we recruited and trained 36 teams of community participan… ▽ More The Citizen CATE 2024 next-generation experiment placed 43 identical telescope and camera setups along the path of totality during the total solar eclipse (TSE) on 8 April 2024 to capture a 60-minute movie of the inner and middle solar corona in polarized visible light. The 2024 TSE path covered a large geographic swath of North America and we recruited and trained 36 teams of community participants ("citizen scientists") representative of the various communities along the path of totality. Afterwards, these teams retained the equipment in their communities for ongoing education and public engagement activities. Participants ranged from students (K12, undergraduate, and graduate), educators, and adult learners to amateur and professional astronomers. In addition to equipment for their communities, CATE 2024 teams received hands-on telescope training, educational and learning materials, and instruction on data analysis techniques. CATE 2024 used high-cadence, high-dynamic-range (HDR) polarimetric observations of the solar corona to characterize the physical processes that shape its heating, structure, and evolution at scales and sensitivities that cannot be studied outside of a TSE. Conventional eclipse observations do not span sufficient time to capture changing coronal topology, but the extended observation from CATE 2024 does. Analysis of the fully calibrated dataset will provide deeper insight and understanding into these critical physical processes. We present an overview of the CATE 2024 project, including how we engaged local communities along the path of totality, and the first look at CATE 2024 data products from the 2024 TSE. △ Less

Submitted 15 December, 2025; originally announced December 2025.

Journal ref: Solar Physics, Vol. 301, 12 (42pp); 2026 January 22

Transient lensing from a photoemitted electron gas imaged by ultrafast electron microscopy

Authors: Omid Zandi, Allan E Sykes, Ryan D Cornelius, Frank M Alcorn, Brandon Zerbe, Phillip M Duxbury, Bryan W Reed, Renske M van der Veen

Abstract: Understanding and controlling ultrafast non-equilibrium charge carrier dynamics is of fundamental importance in diverse fields of (quantum) science and technology. Here, we create a three-dimensional hot electron gas through two-photon photoemission from a copper surface in vacuum. We employ an ultrafast electron microscope to record movies of the subsequent electron dynamics on the picosecond-nan… ▽ More Understanding and controlling ultrafast non-equilibrium charge carrier dynamics is of fundamental importance in diverse fields of (quantum) science and technology. Here, we create a three-dimensional hot electron gas through two-photon photoemission from a copper surface in vacuum. We employ an ultrafast electron microscope to record movies of the subsequent electron dynamics on the picosecond-nanosecond time scale. After a prompt Coulomb explosion, the subsequent dynamics is characterized by a rapid oblate-to-prolate shape transformation of the electron gas, and exceptionally periodic and long-lived electron cyclotron oscillations inside the magnetic field of the objective lens. In this regime, the collective behavior of the oscillating electrons causes a transient, mean-field lensing effect and pronounced distortions in the images. We derive an analytical expression for the time-dependent focal length of the electron-gas lens, and perform numerical electron dynamics and probe image simulations to determine the role of Coulomb self-fields and image charges. This work paves the way for the direct visualization of cyclotron oscillations inside two-dimensional electron-gas materials and the elucidation of electron/plasma dynamics and properties that could benefit the development of high-brightness electron and X-ray sources. △ Less

Submitted 5 January, 2020; originally announced January 2020.

Griffiths Physics in an Ultracold Bose Gas

Authors: M. E. W. Reed, Z. S. Smith, Aftaab Dewan, S. L. Rolston

Abstract: Coupled XY model systems consisting of three-dimensional (3D) systems with disordered interlayer physics are of significant theoretical interest. We realize a set of coupled quasi-2D layers of $^{87}$Rb in the presence of disordered inter-layer coupling. This is achieved with our high bandwidth arbitrary optical lattice to obviate restrictions on the dimensionality of disorder with speckle-generat… ▽ More Coupled XY model systems consisting of three-dimensional (3D) systems with disordered interlayer physics are of significant theoretical interest. We realize a set of coupled quasi-2D layers of $^{87}$Rb in the presence of disordered inter-layer coupling. This is achieved with our high bandwidth arbitrary optical lattice to obviate restrictions on the dimensionality of disorder with speckle-generated optical fields. We identify phase crossover regions compatible with the existence of a pair of intermediate Griffiths phases between a thermal state and the emergence of bulk 3D superfluidity. △ Less

Submitted 16 July, 2019; v1 submitted 19 June, 2018; originally announced June 2018.

Comments: 7 pages, 8 figures; updated to match published version

Journal ref: Phys. Rev. A 99, 063611 (2019)

Various Compressed Sensing Set-Ups Evaluated Against Shannon Sampling Under Constraint of Constant Illumination

Authors: Wouter Van den Broek, Bryan W. Reed, Armand Béché, Abner Velazco, Johan Verbeeck, Christoph T. Koch

Abstract: Under the constraint of constant illumination, an information criterion is formulated for the Fisher information that compressed sensing measurements in optical and transmission electron microscopy contain about the underlying parameters. Since this approach requires prior knowledge of the signal's support in the sparse basis, we develop a heuristic quantity, the detective quantum efficiency (DQE)… ▽ More Under the constraint of constant illumination, an information criterion is formulated for the Fisher information that compressed sensing measurements in optical and transmission electron microscopy contain about the underlying parameters. Since this approach requires prior knowledge of the signal's support in the sparse basis, we develop a heuristic quantity, the detective quantum efficiency (DQE), that tracks this information criterion well without this knowledge. It is shown that for the investigated choice of sensing matrices, and in the absence of read-out noise, i.e. with only Poisson noise present, compressed sensing does not raise the amount of Fisher information in the recordings above that of Shannon sampling. Furthermore, enabled by the DQE's analytical tractability, the experimental designs are optimized by finding out the optimal fraction of on-pixels as a function of dose and read-out noise. Finally, we introduce a regularization and demonstrate, through simulations and experiment, that it yields reconstructions attaining minimum mean squared error at experimental settings predicted by the DQE as optimal. △ Less

Submitted 11 January, 2019; v1 submitted 8 January, 2018; originally announced January 2018.

Comments: 18 pages, 13 figures. New Monte Carlo simulations in Figure 13 showing the behavior of the single-pixel camera under various magnitudes of read-out noise

Journal ref: IEEE Transactions on Computational Imaging, 2019

GHz Laser-free Time-resolved Transmission Electron Microscopy: a Stroboscopic High-duty-cycle Method

Authors: Jiaqi Qiu, Gwanghui Ha, Chunguang Jing, Sergey V. Baryshev, Bryan W. Reed, Yimei Zhu, June W. Lau

Abstract: A device and a method for producing ultrashort electron pulses with GHz repetition rates via pulsing an input direct current (dc) electron beam are provided. The device and the method are based on an electromagnetic-mechanical pulser (EMMP) that consists of a series of transverse deflecting cavities and magnetic quadrupoles. The EMMP modulates and chops the incoming dc electron beam and converts i… ▽ More A device and a method for producing ultrashort electron pulses with GHz repetition rates via pulsing an input direct current (dc) electron beam are provided. The device and the method are based on an electromagnetic-mechanical pulser (EMMP) that consists of a series of transverse deflecting cavities and magnetic quadrupoles. The EMMP modulates and chops the incoming dc electron beam and converts it into pico- and sub-pico-second (100 fs to 10 ps) electron pulse sequences at >1 GHz repetition rates. Applying the EMMP to a transmission electron microscope (TEM) with any dc electron source, a GHz stroboscopic high-duty-cycle TEM can be realized. Unlike in many recent developments in time-resolved TEM that rely on a sample pumping laser paired with a laser launching electrons from a photocathode to probe the sample, there is no laser in the presented experimental set-up. This is expected to be a significant relief for electron microscopists who are not familiar with laser systems. The EMMP and the sample are externally driven by a radiofrequency (RF) source synchronized through a delay line. With no laser pumping the sample, the problem of the laser induced residual heating/damaging the sample is eliminated. As many RF-driven processes can be cycled indefinitely, sampling rates of 1-50 GHz become accessible. Such a GHz stroboscopic TEM would open up a new paradigm for in situ and in operando experiments to study samples externally driven electromagnetically. Complementary to the lower (MHz) repetition rates experiments enabled by laser photocathode TEM, new experiments in the high rep-rate multi-GHz regime will be enabled by the proposed RF design. In this article, we report an optimal design of the EMMP and an analytical generalized matrix approach in the thin lens approximation, along with detailed beam dynamics taking actual realistic dc beam parameters in a TEM operating at 200 keV. △ Less

Submitted 16 August, 2015; originally announced August 2015.

Disorder-Driven Loss of Phase Coherence in a Quasi-2D Cold Atom System

Authors: M. C. Beeler, M. E. W. Reed, T. Hong, S. L. Rolston

Abstract: We study the order parameter of a quasi-2D gas of ultracold atoms trapped in an optical potential in the presence of controllable disorder. Our results show that disorder drives phase fluctuations without significantly affecting the amplitude of the quasi-condensate order parameter. This is evidence that disorder can drive phase fluctuations in 2D systems, relevant to the phase-fluctuation mechani… ▽ More We study the order parameter of a quasi-2D gas of ultracold atoms trapped in an optical potential in the presence of controllable disorder. Our results show that disorder drives phase fluctuations without significantly affecting the amplitude of the quasi-condensate order parameter. This is evidence that disorder can drive phase fluctuations in 2D systems, relevant to the phase-fluctuation mechanism for the superconductor-to-insulator phase transition (SIT) in disordered 2D superconductors. △ Less

Submitted 22 March, 2012; v1 submitted 5 November, 2011; originally announced November 2011.

Journal ref: New J. Phys. 14 073024 (2012)

A Problem in Paleobiology

Authors: Barry D. Hughes, William J. Reed

Abstract: We present a stochastic model for the size of a taxon in paleobiology, in which we allow for the evolution of new taxon members, and both individual and catastrophic extinction events. The model uses ideas from the theory of birth and death processes. Some general properties of the model are developed, and a fuller discussion is given for specific distributions of the time between catastrophic e… ▽ More We present a stochastic model for the size of a taxon in paleobiology, in which we allow for the evolution of new taxon members, and both individual and catastrophic extinction events. The model uses ideas from the theory of birth and death processes. Some general properties of the model are developed, and a fuller discussion is given for specific distributions of the time between catastrophic extinction events. Long tails in the taxon size distribution arise naturally from the model. △ Less

Submitted 20 November, 2002; originally announced November 2002.

Comments: 4 pages, LaTex2e (revtex4)