Physics
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The Physics department is committed to education and research in physics, the study of the fundamental universal laws that govern the behavior of matter and energy, and the exploration of the consequences and applications of those laws. Our department is widely known for its excellent teaching and student mentoring. Our department plays an important role in the university’s Core Curriculum. We have strong academic programs with several options for undergraduate physics majors, leading to the B.S. degree, as well as graduate curricula leading to the M.S. and Ph.D. degrees. Our research groups span a variety of fields within physics. Our principal concentrations are in Astrophysics, Relativity, Gravitation and Cosmology, Condensed Matter Physics, Lasers and Optics, Physics Education, Solar Physics, and the Space Science and Engineering Lab.
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Item Performance of the multilayer‐coated mirrors for the MultiSpectral Solar Telescope Array(1994-02-01) Allen, Maxwell; Willis, Thomas D.; Kankelborg, Charles; O'Neal, Ray H.; Martinez-Galarce, Dennis S.; DeForest, Craig; Jackson, Lisa R.; Plummer, James D.; Walker, Arthur B.C. II; Barbee, Troy W. Jr.; Weed, J.W.; Hoover, Richard B.The Multi-Spectral Solar Telescope Array, a rocket-borne solar observatory, was successfully flown in May, 1991, obtaining solar images in eight XUV and FUV bands with 12 compact multilayer telescopes. We report on recent measurements of the performance of multilayer coated mirrors for the Multi Spectral Solar Telescope Array, carried out at the Stanford Synchrotron Radiation Laboratory.Item Multi‐Spectral Solar Telescope Array VIII: the second flight(1995-06-20) Walker, Arthur B.C. II; Allen, Maxwell; DeForest, Craig; Kankelborg, Charles; Martinez-Galarce, Dennis S.; Plummer, James E.; Hoover, Richard B.; Barbee, Troy W. Jr.; Gore, David B.The Multi Spectral Solar Telescope Array (MSSTA) is a rocket borne observatory that utilizes an array of multi-layer and interference film coated telescopes to observe the solar atmosphere from the chromosphere to the corona, over a broad spectral range (VUV - soft x rays). The MSSTA is continuously evolved to incorporate new instruments, and to improve its ability to investigate specific topics related to the structure and dynamics of the solar atmosphere. We describe chromospheric and coronal observations recorded during the second flight of the MSSTA on November 3, 1994 at 1915 UT.Item Calibration of multilayer mirrors for the Multi‐Spectral Solar Telescope Array II(1995-06-20) Kankelborg, Charles; Plummer, James E.; Martinez-Galarce, Dennis S.; O'Neal, Ray H.; DeForest, Craig; Walker, Arthur B.C. II; Barbee, Troy W. Jr.; Weed, J.W.; Hoover, Richard B.; Powell, Forbes R.The Multi-Spectral Solar Telescope Array II (MSSTA II), a rocket-borne solar observatory, was successfully flown on November 3, 1994 obtaining solar images in multiple XUV and FUV bands with an array of compact multilayer telescopes. Extensive measurements have recently been carried out on some of the multilayer telescopes at the Stanford Synchrotron Radiation Laboratory. These measurements are the first high spectral resolution calibrations of newly introduced MSSTA II instruments and instruments with lambda0 less than 130 angstrom. Previous measurements and/or calculations of telescope throughputs have been confirmed with greater accuracy. Results are presented on Mo/Si multilayer bandpasses, and multilayer bandpass changes with time.Item Optical focusing and alignment of the Multi‐Spectral Solar Telescope Array II payload(1995-06-20) Gore, David B.; Hadaway, James B.; Hoover, Richard B.; Walker, Arthur B.C. II; Kankelborg, CharlesThe Multi-Spectral Solar Telescope Array (MSSTA) is a sounding rocket borne observatory designed to image the sun at many spectral lines in soft x-ray, EUV, and FUV wavelengths. Of the nineteen telescopes flown on November 3, 1994 the two Cassegrain telescopes and three of the six Ritchey-Cretien telescopes were focussed at NASA/Marshall Space Flight Center (MSFC) with a Zygo double-pass interferometer to determine the best positions of back focus. The remaining three Ritchey-Cretien and eleven Herschellian telescopes were focussed in situ at White Sands Missile Range by magnifying the telescopic image through a Gaertner traveling microscope and recording the position of best focus. From the data obtained at visible wavelengths, it is not unreasonable to expect that many of our telescopes did attain the sub-arc second resolution for which they were designed.Item Design and performance of thin foil XUV filters for the Multi‐Spectral Solar Telescope Array II(1995-06-20) Plummer, James E.; DeForest, Craig; Martinez-Galarce, Dennis S.; Kankelborg, Charles; Gore, David B.; O'Neal, Ray H.; Walker, Arthur B.C. II; Powell, Forbes R.; Hoover, Richard B.; Barbee, Troy W. Jr.; Weed, J.W.The redesigned payload of the Multi-Spectral Solar Telescope Array (MSSTA), the MSSTA II, was successfully flown on November 3, 1994. The multilayer mirrors used in the normal incidence optical systems of the MSSTA II are efficient reflectors for soft x-ray/extreme ultraviolet (EUV) radiation at wavelengths that satisfy the Bragg condition, thus allowing a narrow band of the soft x-ray/EUV spectrum to be isolated. When applied to solar observations the temperature response of an optical system is quite sensitive to telescope bandpass because of the high density of lines in the coronal spectrum. We have designed a set of thin foil filters in conjunction with our multilayer optics to eliminate contaminant lines and specular reflectivity, thus enhancing the temperature diagnostic capabilities of our instruments. Extensive measurements have recently been carried out on the thin foil filters at the Stanford Synchrotron Radiation Laboratory. We describe here the design and performance of thin foil filters developed for the MSSTA II.Item High‐resolution imaging with multilayer telescopes: resolution performance of the MSSTA II telescopes(1999-09-29) Martinez-Galarce, Dennis S.; Walker, Arthur B.C. II; Gore, David B.; Kankelborg, Charles; Hoover, Richard B.; Barbee, Troy W. Jr.; Boerner, P.The Multi-Spectral Solar Telescope Array (MSSTA) is a sounding rocket-borne observatory composed of a set of normal-incidence multilayer-coated telescopes that obtained selected bandpass spectroheliograms of the Solar atmosphere. These spectroheliograms were recorded on specially fabricated XUV and FUV 70mm Kodak film. Rocket launches of this instrument payload took place in 1991 and 1994 at the White Sands Missile Test Range in New Mexico, sponsored by the NASA sounding rocket experiment program. Immediately prior to the 1994 launch, visible light focusing test of each telescope were performed in-situ using a 1951 Standard Air Force High Resolution Test-target, to measure optical resolution performance. We determined that the MSSTA II telescopes performed at diffraction-limited resolutions down to 0.70 arc-second at visible wavelengths. Based on these measurements, we calculated an upper-bound to the focusing errors that incorporate the sum of all uncorrelated system resolution errors that affect resolution performance. Coupling these upper-bound estimates with the in-band diffraction limits, surface scattering errors and payload pointing jitter, we demonstrate that eleven of nineteen MSSTA II telescopes - having negligible figures of focus errors in comparison to the corresponding visible diffraction limits - performed at sub arc-second resolution at their operation FUV/EUV/XUV wavelengths during flight. We estimate the in-band performance down to 0.14 +/- 0.08 second of arc.Item Simultaneous imaging and spectroscopy of the solar atmosphere: advantages and challenges of a 3‐order slitless spectrograph(2001-12-10) Kankelborg, Charles; Thomas, Roger J.The dynamic solar atmosphere poses a severe observational challenge for imaging spectroscopy in EUV. The traditional method of building up images by rastering a slit spectrograph has so far proven too slow to keep up with the Sun's rapidly changing transition region and corona. We describe a new approach, using a slitless imaging spectrograph operating in a narrow band, with imaging detectors at three orders. This arrangement offers cotemporal imaging and spectroscopy at high spatial, spectral, and temporal resolution. The prospect of disentangling spatial and spectral information is greatly improved by choosing a narrow band containing only two spectral lines, and by imaging at several spectral orders. This paper discusses several advantages and challenges of the multiorder slitless approach. We derive a mathematical description of the null space of spatialspectral signatures to which an ideal threeorder slitless spectrograph has zero response. An exploration of the null space helps to clarify the capabilities and limitations of this instrument type. We infer that the threeorder slitless spectrograph is sensitive to line intensity, doppler shift and line width; but insensitive to line asymmetry. Strategies are developed to minimize the ambiguity in interpreting the multiorder data. A proof of concept sounding rocket payload, the MultiOrder Solar EUV Spectrograph (MOSES), is under development with an anticipated launch in Spring, 2004.Item Data inversion for the Multi‐Order Solar Extreme‐Ultraviolet Spectrograph(2003-11-05) Fox, J. Lewis; Kankelborg, Charles; Metcalf, Tomas R.The Multi-Order Solar Extreme Ultraviolet Spectrograph (MOSES) is a high resolution, slitless imaging spectrometer that will observe the Sun in extreme ultraviolet near 304A. MOSES will fly on a NASA sounding rocket launch in spring 2004. The instrument records spatial and spectral information into images at three spectral orders. To recover the source spectrum, an illposed inversion must be performed on these data. We will explore two of the techniques by which this may be accomplished: Fourier backprojection and Pixons, constrained by the spatially integrated spectrum of the Sun. Both methods produce good results, including doppler shifts measured to 1/3pixel accuracy. The Pixon code better reproduces the line widths.Item Narrow‐band EUV multilayer coating for the MOSES sounding rocket(2005-09-08) Owens, Scott M.; Gum, Jeffery S.; Tarrio, Charles; Grantham, Steven; Dvorak, Joseph; Kjornrattanawanich, Benjawan; Keski-Kuha, Ritva; Thomas, Roger J.; Kankelborg, CharlesThe Multiorder Solar EUV Spectrograph (MOSES) is a slitless spectrograph designed to study solar He II emission at 303.8 Å (1 Å = 0.1 nm), to be launched on a sounding rocket payload. One difference between MOSES and other slitless spectrographs is that the images are recorded simultaneously at three spectral orders, m = 1, 0, +1. Another is the addition of a narrowband multilayer coating on both the grating and the fold flat, which will reject outofband lines that normally contaminate the image of a slitless instrument. The primary metrics for the coating were high peak reflectivity and suppression of Fe XV and XVI emission lines at 284 Å and 335 Å, respectively. We chose B4C/Mg2Si for our material combination since it provides excellent peak reflectivity and rejection of outofband wavelengths. Measurements of witness flats at NIST indicate the peak reflectivity at 303.8 is 39.0% for a 15 bilayer stack, while suppression ranges from 7.5x to 12.9x at 284 Å and from 3.4x to 15.1x at 335 Å for the individual reflections in the optical path. We present the results of coating the MOSES flight gratings and fold flat, including the spectral response of the fold flat and grating as measured at NIST's SURF III and Brookhaven's X24C beamline, respectively.Item Reconnectionless CME Eruption: Putting the Aly‐Sturrock Conjecture to Rest(2009-03-09) Rachmeler, L.A.; DeForest, C.E.; Kankelborg, CharlesWe demonstrate that magnetic reconnection is not necessary to initiate fast Coronal mass ejections (CMEs). The AlySturrock conjecture states that the magnetic energy of a given forcefree boundary field is maximized when the field is open. This is problematic for CME initiation because it leaves little or no magnetic energy to drive the eruption, unless reconnection is present to allow some of the flux to escape without opening. Thus, it has been thought that reconnection must be present to initiate CMEs. This theory has not been subject to rigorous numerical testing because conventional magnetohydrodynamics (MHD) numerical models contain numerical diffusion, which introduces uncontrolled numerical reconnection. We use a quasiLagrangian simulation technique to run the first controlled experiments of CME initiation in the complete lack of reconnection. We find that a flux rope confined by an arcade, when twisted beyond a critical amount, can escape to an open state, allowing some of the surrounding arcade to shrink, and releasing magnetic energy from the global field. This mechanism includes a true ideal MHD instability. We conclude that reconnection is not a necessary trigger for fast CME eruptions.