From 080b9fb9d2416070a2ee7a8403efb8513022875f Mon Sep 17 00:00:00 2001
From: Jameson Graef Rollins <jrollins@finestructure.net>
Date: Thu, 19 Sep 2019 23:55:09 -0700
Subject: [PATCH] suspension thermal noise simplification
new suspension_thermal() function for calculating thermal noise of a
single suspended optic.
ifo SuspensionThermal Noise class modified to handle specific case of
Fabry-Perot Michelson.
---
gwinc/ifo/noises.py | 3 ++-
gwinc/noise/suspensionthermal.py | 43 +++++++++++++++++---------------
2 files changed, 25 insertions(+), 21 deletions(-)
diff --git a/gwinc/ifo/noises.py b/gwinc/ifo/noises.py
index f203c827..81d56cd0 100644
--- a/gwinc/ifo/noises.py
+++ b/gwinc/ifo/noises.py
@@ -103,7 +103,8 @@ class SuspensionThermal(nb.Noise):
)
def calc(self):
- return noise.suspensionthermal.susptherm(self.freq, self.ifo)
+ n = noise.suspensionthermal.suspension_thermal(self.freq, self.ifo.Suspension)
+ return n * 4 * self.ifo.gwinc.dhdl_sqr
class CoatingBrownian(nb.Noise):
diff --git a/gwinc/noise/suspensionthermal.py b/gwinc/noise/suspensionthermal.py
index dcc34618..c5b4910a 100644
--- a/gwinc/noise/suspensionthermal.py
+++ b/gwinc/noise/suspensionthermal.py
@@ -1,39 +1,45 @@
+'''Functions to calculate suspension thermal noise
+
+'''
from __future__ import division
-from numpy import pi, imag, zeros
import numpy as np
+from numpy import pi, imag, zeros
from .. import const
-def susptherm(f, ifo):
- """Suspention thermal noise.
+def suspension_thermal(f, sus):
+ """Suspention thermal noise for a single suspended test mass
- 'Temp' must either be set for each stage individually, or globally
- in ifo.Suspension.Temp. The latter will be preferred if
- specified, so if you wish to use per-stage tempurature you must
- remove Suspension.Temp.
+ :f: frequency array in Hz
+ :sus: gwinc suspension structure
+
+ :returns: displacement noise power spectrum at :f:
+
+ :Temp: must either be set for each stage individually, or globally
+ in :sus.Temp:. The latter will be preferred if specified, so if
+ you wish to use per-stage tempurature you must remove :sus.Temp:.
Assumes suspension transfer functions and V-H coupling have been
- pre-calculated and populated into the relevant `ifo` struct
- fields.
+ pre-calculated and populated into the relevant `sus` fields.
"""
# Assign Physical Constants
kB = const.kB
# and vertical to beamline coupling angle
- theta = ifo.Suspension.VHCoupling.theta
+ theta = sus.VHCoupling.theta
noise = zeros((1, f.size))
# if the temperature is uniform along the suspension
- if 'Temp' in ifo.Suspension:
+ if 'Temp' in sus:
##########################################################
# Suspension TFs
##########################################################
- hForce = ifo.Suspension.hForce
- vForce = ifo.Suspension.vForce
+ hForce = sus.hForce
+ vForce = sus.vForce
##########################################################
# Thermal Noise Calculation
@@ -46,7 +52,7 @@ def susptherm(f, ifo):
# thermal noise (m^2/Hz) for one suspension
w = 2*pi*f
- noise = 4 * kB * ifo.Suspension.Temp * abs(imag(dxdF)) / w
+ noise = 4 * kB * sus.Temp * abs(imag(dxdF)) / w
# if the temperature is set for each suspension stage
else:
@@ -54,15 +60,15 @@ def susptherm(f, ifo):
# Suspension TFs
##########################################################
- hForce = ifo.Suspension.hForce_singlylossy[:, :]
- vForce = ifo.Suspension.vForce_singlylossy[:, :]
+ hForce = sus.hForce_singlylossy[:, :]
+ vForce = sus.vForce_singlylossy[:, :]
##########################################################
# Thermal Noise Calculation
##########################################################
dxdF = zeros(hForce.shape, dtype=complex)
- for n, stage in enumerate(reversed(ifo.Suspension.Stage)):
+ for n, stage in enumerate(reversed(sus.Stage)):
# add up the contribution from each stage
# convert to beam line motion. theta is squared because
@@ -74,7 +80,4 @@ def susptherm(f, ifo):
w = 2*pi*f
noise += 4 * kB * stage.Temp * abs(imag(dxdF[n, :])) / w
- # 4 masses, turn into gravitational wave strain
- noise *= 4 * ifo.gwinc.dhdl_sqr
-
return np.squeeze(noise)
--
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