From c965293558913db57b7f31092d445ecbcf29bfe7 Mon Sep 17 00:00:00 2001
From: Christopher Wipf <wipf@ligo.mit.edu>
Date: Tue, 26 Jun 2018 05:46:18 -0700
Subject: [PATCH] newtonian: update Newtonian noise calculation Implements the
changes recommended by Jan Harms in
https://git.ligo.org/rana-adhikari/CryogenicLIGO/issues/45 Fixes #18
---
gwinc/ifo/A+.yaml | 8 +--
gwinc/ifo/CEcryo.yaml | 6 ++-
gwinc/ifo/Voyager.yaml | 6 ++-
gwinc/ifo/aLIGO.yaml | 8 +--
gwinc/noise/newtonian.py | 114 +++++++++++++--------------------------
5 files changed, 56 insertions(+), 86 deletions(-)
diff --git a/gwinc/ifo/A+.yaml b/gwinc/ifo/A+.yaml
index fd3b294..3f0ae0e 100644
--- a/gwinc/ifo/A+.yaml
+++ b/gwinc/ifo/A+.yaml
@@ -58,11 +58,13 @@ Seismic:
Site: 'LHO' # LHO or LLO (only used for Newtonian noise)
KneeFrequency: 10 # Hz; freq where 'flat' noise rolls off
LowFrequencyLevel: 1e-9 # m/rtHz; seismic noise level below f_knee
- Gamma: .8 # abruptness of change at f_knee
+ Gamma: 0.8 # abruptness of change at f_knee
Rho: 1.8e3 # kg/m^3; density of the ground nearby
- Beta: 0.6 # quiet times beta: 0.35-0.60
- # noisy times beta: 0.15-1.4
+ Beta: 0.8 # quiet times beta: 0.35-0.60
+ # noisy times beta: 0.15-1.4
Omicron: 1 # Feedforward cancellation factor
+ TestMassHeight: 1.5 # m
+ RayleighWaveSpeed: 250 # m/s
Suspension:
Type: 'Quad'
diff --git a/gwinc/ifo/CEcryo.yaml b/gwinc/ifo/CEcryo.yaml
index cda2758..ce81598 100644
--- a/gwinc/ifo/CEcryo.yaml
+++ b/gwinc/ifo/CEcryo.yaml
@@ -72,10 +72,12 @@ Seismic:
Site: 'LHO' # LHO or LLO (only used for Newtonian noise)
KneeFrequency: 10 # Hz; freq where 'flat' noise rolls off
LowFrequencyLevel: 1e-9 # m/rtHz; seismic noise level below f_knee
- Gamma: .8 # abruptness of change at f_knee
+ Gamma: 0.8 # abruptness of change at f_knee
Rho: 1.8e3 # kg/m^3; density of the ground nearby
- Beta: 1 # quiet times beta = 0.35-0.60; noisy times beta = 0.15-1.4
+ Beta: 0.8 # quiet times beta = 0.35-0.60; noisy times beta = 0.15-1.4
Omicron: 10 # Feedforward cancellation factor
+ TestMassHeight: 1.5 # m
+ RayleighWaveSpeed: 250 # m/s
#darmSeiSusFile: 'CryogenicLIGO/Sensitivity/GWINC/seismic.mat'
Suspension:
diff --git a/gwinc/ifo/Voyager.yaml b/gwinc/ifo/Voyager.yaml
index cde8105..bd0040d 100644
--- a/gwinc/ifo/Voyager.yaml
+++ b/gwinc/ifo/Voyager.yaml
@@ -70,10 +70,12 @@ Seismic:
Site: 'LHO' # LHO or LLO (only used for Newtonian noise)
KneeFrequency: 10 # Hz; freq where 'flat' noise rolls off
LowFrequencyLevel: 1e-9 # m/rtHz; seismic noise level below f_knee
- Gamma: .8 # abruptness of change at f_knee
+ Gamma: 0.8 # abruptness of change at f_knee
Rho: 1.8e3 # kg/m^3; density of the ground nearby
- Beta: 1 # quiet times beta = 0.35-0.60; noisy times beta = 0.15-1.4
+ Beta: 0.8 # quiet times beta = 0.35-0.60; noisy times beta = 0.15-1.4
Omicron: 10 # Feedforward cancellation factor
+ TestMassHeight: 1.5 # m
+ RayleighWaveSpeed: 250 # m/s
#darmSeiSusFile: 'CryogenicLIGO/Sensitivity/GWINC/seismic.mat'
Suspension:
diff --git a/gwinc/ifo/aLIGO.yaml b/gwinc/ifo/aLIGO.yaml
index 498f6ee..ea588e5 100644
--- a/gwinc/ifo/aLIGO.yaml
+++ b/gwinc/ifo/aLIGO.yaml
@@ -58,11 +58,13 @@ Seismic:
Site: 'LHO' # LHO or LLO (only used for Newtonian noise)
KneeFrequency: 10 # Hz; freq where 'flat' noise rolls off
LowFrequencyLevel: 1e-9 # m/rtHz; seismic noise level below f_knee
- Gamma: .8 # abruptness of change at f_knee
+ Gamma: 0.8 # abruptness of change at f_knee
Rho: 1.8e3 # kg/m^3; density of the ground nearby
- Beta: 0.5 # quiet times beta: 0.35-0.60
- # noisy times beta: 0.15-1.4
+ Beta: 0.8 # quiet times beta: 0.35-0.60
+ # noisy times beta: 0.15-1.4
Omicron: 1 # Feedforward cancellation factor
+ TestMassHeight: 1.5 # m
+ RayleighWaveSpeed: 250 # m/s
Suspension:
Type: 'Quad'
diff --git a/gwinc/noise/newtonian.py b/gwinc/noise/newtonian.py
index 15f9b10..a0d2d5e 100644
--- a/gwinc/noise/newtonian.py
+++ b/gwinc/noise/newtonian.py
@@ -1,7 +1,6 @@
from __future__ import division
import scipy.constants
-from numpy import pi, sqrt
-import logging
+from numpy import pi, sqrt, exp
def gravg(f, ifo):
@@ -9,100 +8,63 @@ def gravg(f, ifo):
N = GRAVG(F, IFO) returns the gravity gradient (Newtonian) noise
contribution in strain^2/Hz for four mirrors.
-
+
References:
-
+
Saulson 1984, http://dx.doi.org/10.1103/PhysRevD.30.732
Hughes and Thorne 1998, http://dx.doi.org/10.1103/PhysRevD.58.122002
-
+
Driggers and Harms 2011, ``Results of Phase 1 Newtonian Noise
Measurements at the LIGO Sites,'' February-March 2011. T1100237.
https://dcc.ligo.org/cgi-bin/private/DocDB/ShowDocument?docid=60064
-
- See also: ground.m
-
+
Written by Enrico Camagna (?)
-
+
added to Bench by Gregg Harry 8/27/03
seismic spectrum modified by Jan Harms 05/11/2010
Calculates gravity gradient noise for four mirrors
"""
- L = ifo.Infrastructure.Length
- G = scipy.constants.G
- rho = ifo.Seismic.Rho
+
+ fk = ifo.Seismic.KneeFrequency
+ a = ifo.Seismic.LowFrequencyLevel
+ L = ifo.Infrastructure.Length
+ gamma = ifo.Seismic.Gamma
+ ggcst = scipy.constants.G
+ rho = ifo.Seismic.Rho
# factor to account for correlation between masses
# and the height of the mirror above the ground
- beta = ifo.Seismic.Beta
+ beta = ifo.Seismic.Beta
+ h = ifo.Seismic.TestMassHeight
+ c_rayleigh = ifo.Seismic.RayleighWaveSpeed
- if 'Spectrum' in ifo.Seismic:
- seismic = ifo.Seismic.Spectrum
+ if 'Omicron' in ifo.Seismic:
+ omicron = ifo.Seismic.Omicron
else:
- seismic = ground(ifo.Seismic, f)
-
- # effective GG spring frequency, with G gravitational
- fgg = sqrt(G * rho) / (2*pi)
-
- # fixed numerical factors, 5/9/06, PF
- n = (beta*4*pi/L*(fgg**2/f**2)*seismic)**2
-
- # Feedforward cancellation
- n /= (ifo.Seismic.Omicron)**2
-
- return n
-
-
-def ground(Seismic, f):
- """Estimate of seismic displacement spectrum
-
- N = GROUND(SEISMIC, F) returns the estimated ground (seismic)
- displacement spectrum in meters / rtHz at frequencies F using
- parameters SEISMIC (usually a field of the IFOMODEL).
-
- Example usage:
-
- ifo = IFOModel();
- f = logspace(log10(1), log10(60), 101);
- n = ground(ifo.Seismic, f);
- loglog(f, n)
- ylabel('meters / rtHz');
- xlabel('Hz');
-
- This function is currently only used by gravg.m (Newtonian Noise).
-
- Jan says: The seismic NN is 90th percentile. But this was just to
- lift the spectra above the aLIGO GWINC sensitivity. 90th, 95th,
- whatever percentile does not matter since you want to guarantee
- that NN is not limiting at any time. So in the spectral plot the
- only important information is that NN can be high enough to be
- seen in the detector.
-
- References:
- Waldman and Fritschel, 'Reference Seismic Data for LLO', T0900312
- https://dcc.ligo.org/cgi-bin/private/DocDB/ShowDocument?docid=3315
-
- """
- fk = Seismic.KneeFrequency
- a1 = Seismic.LowFrequencyLevel
- a2 = a1*100
- gamma = Seismic.Gamma
+ omicron = 1
# a sort of theta function (Fermi distr.)
coeff = 1/(1 + 3**(gamma*(f-fk)))
- # modelization of seismic noise (velocity)
- if 'Site' not in Seismic:
- logging.info('defaulting to Livingston site')
- Seismic.Site = 'LLO'
+ # modelization of seismic noise (vertical)
+ ground = a*coeff + a*(1-coeff)*(fk/f)**2
+ if 'Site' in ifo.Seismic and ifo.Seismic.Site == 'LLO':
+ ground = a*coeff*(fk/f) + a*(1-coeff)*(fk/f)**2
- if Seismic.Site == 'LHO':
- n = (2*pi*f)**(4/3)*(a1*coeff + a1*(1-coeff)*(fk/f)**(9/3))
- elif Seismic.Site == 'LLO':
- n = a2*coeff + a2*(1-coeff)*(fk/f)**2
- else:
- raise 'Unknown seismic.site'
+ # effective GG spring frequency, with G gravitational
+ fgg = sqrt(ggcst * rho) / (2*pi)
+
+ # fixed numerical factors, 5/9/06, PF
+ n = (beta*4*pi/L*(fgg**2/f**2)*ground)**2
- # convert into displacement
- n /= 2*pi*f
+ # The following two terms are corrections due to Jan Harms
+ # https://git.ligo.org/rana-adhikari/CryogenicLIGO/issues/45
+ # (1) projection of NN force onto the direction of the arm
+ n = n * 1/2
+ # (2) exponential cutoff at frequency (seismic speed)/(test mass height)
+ n = n * exp(-4*pi*f*h/c_rayleigh)
+
+ # Feedforward cancellation
+ n /= (omicron**2)
- return n
+ return n * ifo.gwinc.sinc_sqr
--
GitLab