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Search Publications by: Bradley Alpert (Fed)

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Displaying 1 - 25 of 45

Noise-resilient deep tomographic imaging

April 24, 2023
Author(s)
Zhen Guo, Zhiguang Liu, George Barbastathis, Qihang Zhang, Michael Glinsky, Bradley Alpert, Zachary H. Levine
X-ray tomography is a non-destructive imaging technique that reveals the interior of an object from its projections at different angles. Under limited-angle and low-photon sampling, a regularization prior is required to retrieve a high-fidelity

A Tabletop X-Ray Tomography Instrument for Nanometer-Scale Imaging: Reconstructions

April 14, 2023
Author(s)
Zachary H. Levine, Bradley Alpert, Amber Dagel, Joseph Fowler, Edward Jiminez, Nathan J. Nakamura, Daniel Swetz, Paul Szypryt, Kyle Thompson, Joel Ullom
We show three-dimensional reconstructions of a region of an integrated circuit from a 130 nm copper process. The reconstructions employ x-ray computed tomography, measured with a new and innovative high-magnification x-ray microscope. The instrument uses a

Physics-assisted Generative Adversarial Network for X-Ray Tomography

June 10, 2022
Author(s)
Zhen Guo, Jungki Song, George Barbastathis, Michael Glinsky, Courtenay Vaughan, Kurt Larson, Bradley Alpert, Zachary H. Levine
X-ray tomography is capable of imaging the interior of objects in three dimensions non-invasively, with applications in biomedical imaging, materials study, electronic inspection, and other fields. The reconstruction process can be an ill-conditioned

Toward a New Primary Standardization of Radionuclide Massic Activity Using Microcalorimetry and Quantitative Milligram-Scale Samples

February 24, 2022
Author(s)
Ryan P. Fitzgerald, Bradley Alpert, Dan Becker, Denis E. Bergeron, Richard Essex, Kelsey Morgan, Svetlana Nour, Galen O'Neil, Dan Schmidt, Gordon A. Shaw, Daniel Swetz, R. Michael Verkouteren, Daikang Yan
We present a new paradigm for the primary standardization of radionuclide activity per mass of solution (Bq/g). Two key enabling capabilities are 4π decay-energy spectrometry using chip-scale sub-Kelvin microcalorimeters and direct realization of mass by

Advantage of Machine Learning over Maximum Likelihood in Limited-Angle Low-Photon X-Ray Tomography

January 20, 2022
Author(s)
Zhen Guo, Jungki Song, George Barbastathis, Michael Glinsky, Courtenay Vaughan, Kurt Larson, Bradley Alpert, Zachary H. Levine
Limited-angle X-ray tomography reconstruction is an ill-posed inverse problem in general. Especially when the projection angles are limited and the measurements are taken in a photon-limited condition, reconstructions from classical algorithms such as

Near-Field, Spherical-Scanning Antenna Measurements With Nonideal Probe Locations

October 12, 2021
Author(s)
Ronald C. Wittmann, Bradley Alpert, Michael H. Francis
We introduce a near-field, spherical-scanning algorithm for antenna measurements that relaxes the usual condition requiring data points to be on a regular spherical grid. Computational complexity is of the same order as for the standard (ideal-positioning)

Absolute energies and emission line shapes of the x-ray lines of lanthanide metals

February 1, 2021
Author(s)
Joseph Fowler, Galen O'Neil, Bradley K. Alpert, Douglas Bennett, Edward V. Denison, William Doriese, Gene Hilton, Lawrence T. Hudson, Young I. Joe, Kelsey Morgan, Daniel Schmidt, Daniel Swetz, Csilla I. Szabo-Foster, Joel Ullom
We use an array of transition-edge sensors, cryogenic microcalorimeters with 4 eV energy resolution, to measure the x-ray emission-line profiles of four elements of the lanthanide series: praseodymium, neodymium, terbium, and holmium. The spectrometer also

A Robust Principal Component Analysis for Outlier Identification in Messy Microcalorimeter Data

November 12, 2019
Author(s)
Joseph W. Fowler, Bradley K. Alpert, Young I. Joe, Galen C. O'Neil, Daniel S. Swetz, Joel N. Ullom
A principal component analysis (PCA) of clean microcalorimeter pulse records can be a first step beyond statistically optimal linear filtering of pulses toward a fully nonlinear analysis. For PCA to be practical on spectrometers with hundreds of sensors

Approaches to the Optimal Nonlinear Analysis of Microcalorimeter Pulses

March 8, 2018
Author(s)
Joseph W. Fowler, Christine G. Pappas, Bradley K. Alpert, William B. Doriese, Galen C. O'Neil, Joel N. Ullom, Daniel S. Swetz
We consider how to analyze microcalorimeter pulses for quantities that are nonlinear in the data, while preserving the signal-to-noise advantages of linear optimal filtering. We apply the approach to compute the electrothermal feedback energy deficit (the

A Reassessment of Absolute Energies of X-ray L Lines of Lanthanide Metals

June 28, 2017
Author(s)
Bradley Alpert, W.Bertrand (Randy) Doriese, Gene C. Hilton, Lawrence T. Hudson, Young I. Joe, Kelsey Morgan, Carl D. Reintsema, Dan Schmidt, Daniel Swetz, Csilla Szabo-Foster, Joel Ullom, Joseph Fowler, Galen O'Neil, Douglas Bennett
We introduce a new technique for determining x-ray fluorescence line energies and widths, and we present measurements made with this technique of 22 x-ray L lines from lanthanide-series elements. The technique uses arrays of transition-edge sensors

Fast Updating Multipole Coulombic Potential Calculation

June 6, 2017
Author(s)
Thomas Hoft, Bradley Alpert
We present a numerical method to efficiently and accurately re-compute the Coulomb potential of a large ensemble of charged particles after a subset of the particles undergoes a change of position. Errors are bounded even after a large number of such

Ultrafast time-resolved x-ray absorption spectroscopy of ferrioxalate photolysis with a laser plasma x-ray source and microcalorimeter array

February 17, 2017
Author(s)
Galen C. O'Neil, Joel N. Ullom, Luis Miaja Avila, Young Il Joe, Joseph W. Fowler, Carl D. Reintsema, Daniel S. Swetz, Kevin L. Silverman, Daniel R. Schmidt, Bruce D. Ravel, Gene C. Hilton, William B. Doriese, Bradley K. Alpert, Ralph Jimenez
Using a table-top apparatus based upon a laser plasma x-ray source and an array of cryogenic microcalorimeter x-ray detectors, we have measured the transient x-ray absorption spectrum during the ferrioxalate photoreduction reaction. We observe the Fe K

When "Optimal Filtering" Isn't

December 7, 2016
Author(s)
Joseph Fowler, Bradley Alpert, W.Bertrand (Randy) Doriese, James P. Hays-Wehle, Young I. Joe, Kelsey Morgan, Galen O'Neil, Joel Ullom, Dan Schmidt, Daniel Swetz
The so-called ''optimal filter'' analysis of a microcalorimeter's x-ray pulses is statistically optimal only if all pulses have the same shape, regardless of energy. The shapes of pulses from a nonlinear detector can and do depend on the pulse energy

Ultrafast time-resolved hard x-ray emission spectroscopy on a table top

September 27, 2016
Author(s)
Luis Miaja Avila, Galen C. O'Neil, Young Il Joe, Bradley K. Alpert, Niels Damrauer, William B. Doriese, Steven Fatur, Joseph W. Fowler, Gene C. Hilton, Ralph Jimenez, Carl D. Reintsema, Daniel R. Schmidt, Kevin L. Silverman, Daniel S. Swetz, Hideyuki Tatsuno, Joel N. Ullom
Chemical reactions driven by light are fundamental to biology and a source of inspiration for engineering materials to perform tasks such as solar energy harvesting and data storage. Observing and understanding photodynamics requires experimental tools

Code-division-multiplexed readout of large arrays of TES microcalorimeters

September 15, 2016
Author(s)
Kelsey M. Morgan, Bradley K. Alpert, Douglas A. Bennett, William B. Doriese, Joseph W. Fowler, Johnathon D. Gard, Gene C. Hilton, Kent D. Irwin, Young Il Joe, Galen C. O'Neil, Carl D. Reintsema, Edward V. Denison, Daniel R. Schmidt, Joel N. Ullom, Daniel S. Swetz
Code-division multiplexing (CDM) offers a path to reading out large arrays of transition edge sensor (TES) X-ray micro-calorimeters with excellent energy and timing resolution. We demonstrate the readout of X-ray TESs with a 32-channel flux-summed code

Algorithms for Identification of Nearly-Coincident Events in Calorimetric Sensors

December 29, 2015
Author(s)
Bradley K. Alpert, Elena Ferri, Douglas A. Bennett, Marco Faverzani, Joseph W. Fowler, Andrea Giachero, James P. Hays-Wehle, Angelo Nucciotti, Daniel S. Swetz, Joel N. Ullom
For experiments with high arrival rates, reliable identification of nearly-coincident events can be crucial. For calorimetric measurements to directly measure the neutrino mass such as HOLMES, unidentified pulse pile-ups are expected to comprise a leading

The Practice of Pulse Processing

November 12, 2015
Author(s)
Joseph W. Fowler, Bradley K. Alpert, William B. Doriese, Young Il Joe, Galen C. O'Neil, Joel N. Ullom, Daniel S. Swetz
The analysis of data from x-ray microcalorimeters requires great care; their excellent intrinsic energy resolution cannot usually be achieved in practice without a statistically near-optimal pulse analysis and corrections for important systematic errors

Microcalorimeter Spectroscopy at High Pulse Rates: a Multi-Pulse Fitting Technique

August 24, 2015
Author(s)
Joseph W. Fowler, Bradley K. Alpert, William B. Doriese, Young Il Joe, Galen C. O'Neil, Cherno Jaye, Joel N. Ullom, Daniel A. Fischer, Daniel S. Swetz
Transition edge sensor microcalorimeters can measure x-ray and gamma-ray energies with very high energy resolution and high photon-collection efficiency. For this technology to reach its full potential in future x-ray observatories, each sensor must be

Operation of gamma-ray microcalorimeters at elevated count rates using filters with constraints

May 15, 2013
Author(s)
Bradley K. Alpert, Robert D. Horansky, Douglas A. Bennett, William B. Doriese, Joseph W. Fowler, Andrew Hoover, Michael W. Rabin, Joel N. Ullom
We introduce a filter construction method for pulse processing that differs in two respects from that in standard optimal filtering, in which the average pulse shape and noise power spectral density are combined to create a convolution filter for

A high resolution gamma-ray spectrometer based on superconducting microcalorimeters

September 28, 2012
Author(s)
Douglas A. Bennett, Robert D. Horansky, Daniel R. Schmidt, Andrew Hoover, Ryan Winkler, Bradley K. Alpert, James A. Beall, William B. Doriese, Joseph W. Fowler, Gene C. Hilton, Kent D. Irwin, Nathan J. Hoteling, Vincent Y. Kotsubo, John A. Mates, Galen C. O'Neil, Michael W. Rabin, Carl D. Reintsema, Francis J. Schima, Daniel S. Swetz, Leila R. Vale, Joel N. Ullom
Improvements in superconductor device fabrication, detector hybridization techniques, and superconducting quantum interference device readout have made square-centimeter-sized arrays of gammaray microcalorimeters, based on transition-edge sensors (TESs)

Legendre Fit to the Reflection Coefficient of a Radiating Rectangular Waveguide Aperture

August 1, 2012
Author(s)
Dylan F. Williams, Mohammad T. Ghasr, Bradley K. Alpert, Zhongxiang Shen, Alexander Arsenovic, Robert M. Weikle, Reza Zoughi
We accurately calculate the reflection coefficient and normalized admittance of radiating open-ended rectangular waveguides and fit our results with a linear combination of Legendre polynomials. We verify the expression to an accuracy of 0.005 with other

Optimization of the TES-bias circuit for a multiplexed microcalorimeter array

January 27, 2012
Author(s)
William B. Doriese, Bradley K. Alpert, Joseph W. Fowler, Gene C. Hilton, Alex S. Hojem, Kent D. Irwin, Carl D. Reintsema, Daniel R. Schmidt, Greg Stiehl, Daniel S. Swetz, Joel N. Ullom, Leila R. Vale
In the detector-bias circuit of a transition-edge-sensor (TES) microcalorimeter, the TES-shunt resistor (Rsh) and the thermal conductance to the cryogenic bath (G) are often considered to be interchangeable knobs with which to control detector speed