Bulletin of the American Physical Society
2007 APS April Meeting
Volume 52, Number 3
Saturday–Tuesday, April 14–17, 2007; Jacksonville, Florida
Session K12: Experimental Gravity |
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Sponsoring Units: GGR Chair: Peter F. Michelson, Stanford University Room: Hyatt Regency Jacksonville Riverfront City Terrace 8 |
Sunday, April 15, 2007 1:15PM - 1:27PM |
K12.00001: Test of F=ma for small accelerations Stephan Schlamminger, Chris Spitzer, Ki-Young Choi, Jens Gundlach, Brian Woodahl, Jennifer Coy, Ephraim Fischbach We have used a torsion balance to test Newton's second law in the limit of small forces and accelerations. We were able to verify the proportionality between force and acceleration down to accelerations of $5 \times 10^{-14}\; \mbox{m}/\mbox{s}^2$. This is approximately three orders of magnitude lower than a previous measurement and provides a stringent constraint on theories involving a modification of Newtonian dynamics to explain the flatness of galactic rotation curves. [Preview Abstract] |
Sunday, April 15, 2007 1:27PM - 1:39PM |
K12.00002: An apparatus for measuring short-range deviations from Newtonian gravity including a magnetic force calibration Andrew Geraci, David Weld, Sylvia Smullin, John Chiaverini, Aharon Kapitulnik Several recent theories suggest that new physics related to gravity may appear at short length scales. For example, light moduli or particles in ``large'' extra dimensions could mediate macroscopic forces of(super)gravitational strength at length scales below a millimeter. We have built an apparatus utilizing cryogenic micro-cantilevers capable of measuring atto-Newton forces [1] which now includes a magnetic analog for force calibration. Our most recent experimental constraints on Yukawa-type deviations from Newtonian gravity will be presented. References: [1] J. Chiaverini, S. J. Smullin, A. A. Geraci, D. M. Weld, A. Kapitulnik, Phys.Rev.Lett. {\bf{90}}, 151101 (2003). S. J. Smullin, A.A.Geraci, D.M.Weld, J.Chiaverini, S.Holmes, and A. Kapitulnik, Phys. Rev. {\bf{D 72}}, 122001 (2005). [Preview Abstract] |
Sunday, April 15, 2007 1:39PM - 1:51PM |
K12.00003: APOLLO: Testing Gravity with Millimeter-precision Lunar Laser Ranging James Battat, Thomas Murphy, Eric Adelberger, C.D. Hoyle, Russet McMillan, Eric Michelsen, Kenneth Nordtvedt, Adam Orin, Christopher Stubbs, H. Erik Swanson Based on the discovery of the accelerating universe and dark energy, along with our inability to unite quantum mechanics and General Relativity, there is a clear need to probe deeper into gravitational physics. The Earth-Moon-Sun system is a natural, fertile laboratory for such tests. The Apache Point Observatory Lunar Laser-ranging Operation (APOLLO) bounces laser light off of man-made retro-reflectors on the lunar surface to measure the Earth-Moon separation with one millimeter precision. These measurements of the lunar orbit enable improved constraints of gravitational phenomena such as the Weak Equivalence Principle, the Strong Equivalence Principle, de Sitter precession and dG/dt by an order of magnitude or better. I will describe the APOLLO project and its current status, as well as prospects for constraining PPN parameters and the universality of free-fall. [Preview Abstract] |
Sunday, April 15, 2007 1:51PM - 2:03PM |
K12.00004: Faraday Isolator Performance at High Laser Power R.M. Martin, V. Quetschke, G. Mueller, D.H. Reitze, D.B. Tanner As part of the Advanced LIGO upgrade, optical powers as high as 180 W will be required for increased detection sensitivity. Consequently, optical absorption in the Faraday isolators, as well as aspects like thermal lensing, thermal drift, and thermal birefringence will need to be reconsidered. We performed high power tests on Faraday isolators in two different configurations: first using our self-compensating Faraday rotator with a combination of a thin film polarizer (TFP) and a calcite wedge (CW) and, second, using two identical calcite wedges. In each configuration we investigated optical isolation, thermal drift, and compensation for thermal lensing. We found isolation as high as 39 dB for the TFP/CW and 49 dB for the double wedge at 100 W input power. The isolation ratio is practically power invariant for the first configuration and varies by less than 5 dB over 0--100 W for the second. These measurements were made using a beam diameter of 3.9 mm, within 10 \% the value intended for use in Advanced LIGO. Each configuration has advantages; however, both meet requirements for isolation. In order to decide which one will be used in Advanced LIGO, other aspects, like thermal drift, amount of stray light produced, and space available for proper beam separation, should be considered. [Preview Abstract] |
Sunday, April 15, 2007 2:03PM - 2:15PM |
K12.00005: Adaptive Heating for Thermal Compensation in Advanced LIGO Muzammil A. Arain, David H. Reitze, D.B. Tanner, Guido Mueller, Phil Willems We present an adaptive technique to produce and control the asphericity in optical systems via controlled heating of optical materials. The proposed system will play a vital role in the thermal compensation system of advanced LIGO. It will use compensation plates and the mode matching telescope mirrors to mitigate the aspheric thermal aberrations in the test masses. These aberrations are caused by absorption of the high power laser radiation in the arm cavities. Although the specific details of the proposed technique are given for Advanced LIGO, the technique can also be used in other optical systems where controlled shaping of modal properties is required. Furthermore, other applications might require one to match spatial laser modes to cavities that have non-spherical mirror shapes. One example is the Mesa cavity where a `Mexican Hat' mirror profile in the arm cavities is required. Mode matching into such cavities requires non-spherical optics. Thermal adaptive heating can provide the needed profiles. [Preview Abstract] |
Sunday, April 15, 2007 2:15PM - 2:27PM |
K12.00006: Requirement for and characterization of electro-optic modulators for next- generation gravitational wave detector Wan Wu, Volker Quetschke, Ira Thorpe, Rodrigo Delgadillo, Guido Mueller, David Reitze, David Tanner Advanced LIGO is going to have a factor of 10 better strain sensitivity than LIGO through the planned instrument modification and detection scheme optimization. Advanced LIGO's dual recycling optical configuration provides us the ability to detune the signal recycling cavity to achieve much better sensitivity for particular signal sources. However, the complex interferometer configuration plus the proposed application of a high power laser in order to improve the shot noise sensitivity will impose stringent requirement on laser intensity noise, which leads to a higher technical standard of the core optical components such as the electro-optic phase modulator (EOM) in the input optics part. The modulation index variation of the EOM will create laser intensity noise on the carrier light which is going to be used to sense the motion of arm cavities in the DC sensing scheme. This talk will present the stability requirement on the modulation index of the Advanced LIGO EOM and the technique developed to measure the extra amplitude and phase noises generated by the EOM. [Preview Abstract] |
Sunday, April 15, 2007 2:27PM - 2:39PM |
K12.00007: Modeling the Pioneer anomaly Jacques Leibovitz Scientists continue their attempts to model the observed Pioneer anomaly (PA) as an artifact of measurement or of equipment operation. Scientists also explore ``new physics'' as a possible explanation, but they have eliminated dark matter (DM). Here, the main arguments used to eliminate DM are refuted and then the anomaly is modeled by application of Newton laws to the observed macroscopic properties of DM. Around a central mass M, the modeling predicts a DM distribution that produces the PA at short distances (R smaller than 188 AU) from a star like the Sun, and a flat rotation curve at sufficiently large distances from the center of a galaxy. Below about 188 AU from the Sun, the modeling predicts that the anomaly may be expressed as PA = 8.3E-8 {\{}[R\^{}(-2)] -- 1{\}} cm (s)\^{}(-2). It shows that the anomaly remains fairly constant down to 5 AU, decreases significantly from 5 AU to 1 AU where it becomes zero and changes sign below a distance of 1 AU, then increases rapidly in magnitude as R decreases in that range. Verifiable tests are proposed. Some related topics for future research are proposed. [Preview Abstract] |
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