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This Week's Colloquium: John Krizmanic, Oct. 18, 2012

John Krizmanic
CRESST/USRA/NASA/GSFC

Thursday, Oct. 18, 2012
102 JFB

Refreshments: 3:30 pm in 219 JFB
Lecture 4:00pm (102 JFB)

Title: Phase Fresnel Lens Development for X-ray & Gamma-Ray Astronomy

Abstract:

Angular resolution and effective area are two key parameters that define the performance of a telescope. Historically, X-ray and gamma-ray telescopes have not achieved the angular resolution and flux sensitivity possible at longer wavelengths due to the difficulty in collecting and focusing high-energy photons. Currently, the best imaging ability in the X-ray band is given by the Chandra telescope, which has achieved sub-arcsecond imaging below 10 keV. The use of diffractive optics, especially Phase Fresnel Lenses (PFLs), offers a path to significantly improved high-energy performance. In principle, PFLs can achieve diffraction-limited angular resolution, which is orders of magnitude better than the current state-of-the-art, with high throughput at X-ray and gamma-ray energies, and the capability of scaling to meter-size dimensions. Micro-arcsecond angular resolution in the X-ray and gamma-ray band is achievable, which would allow for the direct imaging of the event horizon surrounding Black Holes. We have successfully fabricated PFLs in silicon using Micro-Electro-Mechanical-System (MEMS) fabrication techniques and measured near diffraction-limited performance at X-ray energies at the GSFC 600-meter Interferometry Testbed. The results demonstrate the superior imaging potential in the X-ray/gamma-ray energy band for PFL-based optics in a format that is scalable for astronomical applications.

In this talk I will discuss the astronomical motivation for improving in X-ray and gamma-ray imaging performance, the physics principles behind diffractive optics, our fabrication and characterization of PFLs, and describe potential space-based telescopes employing these optics.

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University of Utah Awarded $1 Million By Keck Foundation to Study Cosmic Rays


John Belz, radar project director & research associate professor.

Grant Will Assist Researchers in Developing New Radar Technique to Study Origin, Energy, and Composition of Universe's Most Energetic Particles

The University of Utah today announced that the W.M. Keck Foundation awarded $1 million to university researchers to study high-energy cosmic rays in Utah’s western deserts that are hurtling their way toward Earth. These rays — 10 trillion times more energetic than particles emitted in a nuclear explosion — originate from violent cosmic events deep within the universe.

The Keck grant will assist a team of researchers in developing a new tool for understanding how the universe evolved. Employing a technique known as “Bistatic Radar,” researchers will attempt to use analog television transmitters and high-speed digital receivers to observe the range, direction and strength of high-energy particles in order to track these rays back to their point of origin. Bistatic Radar will be much less expensive than traditional cosmic ray detection techniques, which employ surface radiation detectors covering thousands of square kilometers of the Earth’s surface and cost tens of millions of dollars.

The new facility created under the auspices of this grant will be known as The W.M. Keck Radar Observatory. The Keck Radar Observatory will be located in Millard County Utah, where it will initially be co-located with Utah’s Telescope Array, currently the largest “conventional” cosmic ray observatory in the Northern Hemisphere. This will enable comparison of the Keck Observatory’s findings with those of a conventional observatory on an event-by-event basis and allow for the evaluation of radar scattering models.

Utah’s western deserts offer low levels of light pollution and atmospheric aerosols, making Utah an ideal location for detecting and studying cosmic rays. In addition, Utah’s deserts are highly “radio-quiet” with low levels of human-generated high-frequency interference, which makes it uniquely suitable for tests of the radar technique.

“We are at the frontier in our understanding of the origin of the universe’s most energetic particles,” said John Belz, radar project director and research associate professor of physics and astronomy at the University of Utah. “These particles are hundreds of thousands of times more energetic than particles emitted from supernova explosions. Our main goal is to understand the origins of these rare cosmic rays, in order to gain a better understanding of some of the most violent processes shaping the universe.”

 

Learn more.

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This Weeks Colloquium: Andy Smith, Sept. 27, 2012

Andy Smith
University of Utah

Thursday, Sept. 27, 2012
102 JFB

Refreshments: 3:30 pm in 219 JFB
Lecture 4:00pm (102 JFB)

Title: TeV Gamma-ray Astrophysics: A Window To The Violent Universe

Abstract:

We are currently in the golden age of high energy gamma-ray astrophysics. While only 8 years ago the number of confirmed sources of TeV radiation in the cosmos numbered less than 5, due to the success of the current generation of Imaging Atmospheric Cherenkov Telescopes (IACTs) such as VERITAS, HESS, and MAGIC, the number of catalogued TeV sources now exceeds 150. Due to the energy budget necessary for TeV gamma-ray production, the study of the universe in this regime reveals key information about some of the most exotic and violent objects in the universe such as the cores of AGN, pulsar winds, and supernova remnants. Additionally, gamma-ray astrophysics also stands to make key measurement on the particle physics properties and cosmic distribution of particle dark matter. In this talk I will review the detection technique used by ground based gamma-ray observatories and survey the most important results from the recent generation of IACTs. I will highlight the contributions of UU Physics and Astronomy in the recent progress of this field as well as illustrating our departments outlook for contributing to VERITAS, HAWC, and the next generation Cherenkov Telescope Array (CTA). CTA is expected to come on-line by the end of the decade and to significantly extend and expand the field of TeV astronomy by utilizing an array of over 50 telescopes.

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Zayd Ma Thesis Defense 09/25/12

Thesis Defense

Zayd Ma

Tuesday, September 25, 2012
10:00am (110 INSCC)

Title: The fundamental physics of spin-exchange optical pumping (SEOP) and a few applications of the resultant hyperpolarized 129Xe

Abstract:

This thesis is focused on the fundamental physics of spin-exchange optical pumping (SEOP) and a few applications of the resultant hyperpolarized 129Xe.

During SEOP, noble-gas and Rb atoms repeatedly collide. During these collisions the Rb valence-electron wavefunction overlaps with the noble-gas nucleus and if either the noble-gas nucleus or Rb electron are highly spin-polarized then the other will experience, on average, a small additional magnetic field that will manifest itself as a shift in the Larmor frequency. The size of the frequency shift is proportional to the magnetization of the polarized atoms and consequently can be used to perform polarimetry. Pulsed NMR was used to measure 3He and 129Xe Larmor frequency shifts, and optically detected continuous-wave electron paramagnetic resonance (EPR) was used to monitor the 87Rb hyperfine transition frequencies.

A successful calibration of the size of the frequency shift due to 129Xe-Rb collisions was done and, using this calibration, initial 129Xe polarimetry data was acquired by monitoring the 87Rb EPR frequency as a function of Xe concentration. The 129Xe polarimetry results were inconclusive due to an unexplained result regarding the sign of the frequency shift, however extensive progress was made in understanding the systematics associated with this type of measurement.

Hyperpolarized 129Xe from the Utah flow-through polarizer was also used in a biological application. The Larmor frequency of dissolved hyperpolarized 129Xe was used to detect and characterize the binding of Xe to wild-type and several mutations of bovine pancreatic trypsin inhibitor (BPTI) protein. In addition to hyperpolarized 129Xe NMR, 1H and 15N heteronuclear single quantum coherence (HSQC) NMR was done on Y23A BPTI in the presence of dissolved Xe. The results confirmed the existence of Xe binding to the cavity in Y23A and were consistent with the hypothesis that smaller cavities lead to bigger 129Xe chemical shifts.

Full program available here (PDF).

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