Download - LOS Absorption Presentation for TCS Group
LIGO-G080428-00-L
LOS AbsorptionPresentation for TCS Group
Rupal S. AminTuesday, August 26, 2008
LIGO-G080428-00-L
Outline
• Motivation• Theory• Procedure• Data• Result
LIGO-G080428-00-L
Motivation
• Question:
• 1) What do we care about the absorption of the large optics?
• 2) What is the absorption value?
• Answer: Silica mirrors inside IFO unfortunately absorb resonant laser power.
LIGO-G080428-00-L
Motivation
• Ans (con’t): Mirrors expand due to temperature changes. Depending on absorption coefficient, mirrors may distort beyond or below design optimum.
Cold Hot
LIGO-G080428-00-L
Motivation
• Measuring absorption (especially the ITMS) allows TCS team to build effective absorption models (Mathematica, Matlab, Finesse, SIS)
• Correct setup scheme for Enhanced TCS. • So…We need the absorption values of the
large Fabry-Perot optics.
LIGO-G080428-00-L
Theory
• Crude theory– Mirrors have body modes
• Finite temperature Brownian motion– Frequencies are thermally dependent
• Due to Young’s modulus having a Y(T).– Track body mode frequency evolutions due to DT– Df yields power absorption
LIGO-G080428-00-L
Theory
• Crude theory
• Better theory
• We need f and ∆f to determine α*
D
D T
KJ
PKf
f abs
7390
1105.7 5
0
t s
tt
setT
Kt
ff
17000'105.10 17000
)'(5
LIGO-G080428-00-L
Procedure
• Power Cycle IFO during fully locked state.– Do this over several hours
• Save data from fast ASQ sample channels and temperature sensors.
• Download GBs of data from LDAS and analyze.
LIGO-G080428-00-L
ProcedurePwr
t
0 50 100 150 200 250 300-800
-600
-400
-200
0
200
400
600
Time (s)
AS
Q F
AS
T (c
ts)
0 1 2 3 4 5 6 7 8 9 1010
-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
Demod Freq from 9330 Hz
ITMY body mode near 9330 Hz
df/f
4 W
1 W
LIGO-G080428-00-L
Data
• Lock data from 899867714 s
• Thermal data: Mirror modes are history dependent
8.9982 8.9984 8.9986 8.9988 8.999 8.9992 8.9994 8.9996
x 108
293.06
293.08
293.1
293.12
293.14
293.16
293.18
293.2
293.22
293.24July 12, 2008 data: Temperature data from BSC 3
Tem
p (C
)
8.9985 8.9986 8.9987 8.9988 8.9989 8.999 8.9991 8.9992 8.9993 8.9994 8.9995
x 108
0
0.5
1
1.5
2
2.5x 10
4
QP
Dx
trans
(cts
)
GPS (x)
QPDx Transmission Data July 12, 2008
0 50 100 150 200 250 300-800
-600
-400
-200
0
200
400
600
Time (s)
AS
Q F
AS
T (c
ts)
LIGO-G080428-00-L
Thermal Resistances and Sources
•BSC and contents slow LVEA to ITM interaction time.
•Beam tubes: heat source but negligible
LIGO-G080428-00-L
Thermal Resistance
• Simulation of TM interaction with BSC. Small perturbations lead to simulation problems.
LIGO-G080428-00-L
Analysis using raw data
LIGO-G080428-00-L
Raw Data (noisy)
8.9985 8.9986 8.9987 8.9988 8.9989 8.999 8.9991 8.9992 8.9993 8.9994 8.9995
x 108
293.05
293.1
293.15
293.2
293.25July 12, 2008 data: Measured Frequency Shift of ITMy with a time shift
Tem
p (C
)
8.9985 8.9986 8.9987 8.9988 8.9989 8.999 8.9991 8.9992 8.9993 8.9994 8.9995
x 108
9325.3
9325.35
9325.4
9325.45
Mea
s. F
req.
(Hz)
LIGO-G080428-00-L
Fitting Data
G
Peak = (x0 , Amplitude)
DC based on noise average
LIGO-G080428-00-L
Analysis using fitted data
LIGO-G080428-00-L
Analysis
• ∆f/f for ITMy
8.9985 8.9986 8.9987 8.9988 8.9989 8.999 8.9991 8.9992 8.9993 8.9994 8.9995
x 108
101.5e-005
101.6e-005
101.7e-005
Mea
s. F
req.
(Hz)
delta f / f
LIGO-G080428-00-L
Results
• Total uncorrected slope = 1.3(3)e-6+/-1.3e-6 Hz/s
• Uncorrected for high power = 4.(43)e-7+/- 3. e-7 Hz/s
• Crudely Corrected slope = ?• Refined df/f = Need to do
LIGO-G080428-00-L
Ambient temperature f-drift
• Crude shift due to temperature fluctuations
8.9985 8.9986 8.9987 8.9988 8.9989 8.999 8.9991 8.9992 8.9993 8.9994 8.9995
x 108
-0.02
-0.015
-0.01
-0.005
0
0.005
0.01
0.015
0.02
GPS (s)
delta
f/f
delta f due to delta T from 9.325 kHz
LIGO-G080428-00-L
Questions?
• 1) What is your purpose?• 2) What is your favourite color?