From 0b1a56db66d4dd7d8c19f1a1dc2aa5cd3f893227 Mon Sep 17 00:00:00 2001 From: bryan newbold Date: Sun, 13 Jul 2008 02:00:24 -0400 Subject: spell checked some files; moved and added images; fixed some links; added warnings --- physics/LIGO | 48 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+) create mode 100644 physics/LIGO (limited to 'physics/LIGO') diff --git a/physics/LIGO b/physics/LIGO new file mode 100644 index 0000000..23fba64 --- /dev/null +++ b/physics/LIGO @@ -0,0 +1,48 @@ +======================================================================= +LIGO: Laser Interferometer Gravitational Observatory +======================================================================= + +.. warning:: This is a rough work in progress!! Likely to be factual errors, poor grammer, etc. + +.. note:: Most of this content is based on a 2002 Caltech course taught by + Kip Thorn [PH237]_ + +Noise Sources +~~~~~~~~~~~~~~~~~~~~~~ + +For initial LIGO, seismic noise dominates below about 60Hz, suspension thermal +noise between 60 and 180Hz, and radiation pressure shot noise above 180Hz. + +Sensitivity +~~~~~~~~~~~~~~~~~~~~~ + +Advanced LIGO will use 40kg sapphire test masses with sensitivity of about 10e-19 meters: 1/10000 of an atomic nucleus, 10e-13 of a wavelength, and half of the entire mirror's wave function. + +LISA +~~~~~~~~~~~~~ + +5e6 km separations between three spacecraft, 1 (astronomical unit, ~1.5e8 from the sun. 1 watt lasers. +The heterodyne detection is of the beat frequencies at each spacecraft of the +two incoming beams. Doppler shifts of spacecraft must be taken into account, +due not only to sun radiation pressure etc, but varying gravitational fields +from planetary orbits. + +The test masses inside LISA should be free falling and have relative +separations stable to 10e-9 cm (10e-5 wavelength of light). + +LISA's sensitivity is in the milihertz regime. + +.. note: (insert LISA noise curve?) + +Data Analysis +~~~~~~~~~~~~~~~~~~~~ + +Using matched filtering (eg, take cross correlation between two waveforms, +integrating their product), frequency sensitivity will be around the inverse +of the number of cycles of waveform (for LIGO, around 20,000 cycles, for LISA +around 200,000 cycles). + +This technique requires known, theoretically derived waveforms (within +phase/amplitude). There are other methods when we don't have good guesses +about the waveform we are looking for... + -- cgit v1.2.3