Stefan Hild 1ILIAS WG1 meeting, Cascina, November 2006 Comparison of tuned and detuned...
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Transcript of Stefan Hild 1ILIAS WG1 meeting, Cascina, November 2006 Comparison of tuned and detuned...
Stefan Hild 1 ILIAS WG1 meeting, Cascina, November 2006
Comparison of tuned and detuned Signal-Recycling
Stefan Hild for the GEO-team
Stefan Hild 2 ILIAS WG1 meeting, Cascina, November 2006
Signal-Recycling in short
Two main parameters:
• Bandwidth (of the SR resonance)
• Tuning (Fourier frequency of the SR resonance)
narrowband
broadband
tuned
detuned
An additional recycling mirror (MSR) at the dark port allows:
• enhancing the GW signal
• shaping the detector responseMSR
Stefan Hild 3 ILIAS WG1 meeting, Cascina, November 2006
SR-Tuning in GEO so far
Downtuning in steps of 25 Hz, 6 Parameters need to be adjusted:• SR frequency• SR gain• SR phase• MI gain• MI phase• MI autoalignment gain
For various reason we are not able aquire lock for tuned SR. Lock takes place at a detuning of a few kHz. Afterwards the aquisition detector is tuned to ist operation point. So far tunings between 5kHz and 250 Hz had been realized.
Stefan Hild 4 ILIAS WG1 meeting, Cascina, November 2006
Motivation (1): Detuned SR complicates noise couplings and TFs
Frequency noise coupling to h(t) Laser intensity noise coupling to h(t)
In a detuned detector TF may become complicated due to interaction and different resonance conditions of various sidebands.
Stefan Hild 5 ILIAS WG1 meeting, Cascina, November 2006
Motivation (2): Sideband picture for tuned and detuned SR
Frequency of the light
Stefan Hild 6 ILIAS WG1 meeting, Cascina, November 2006
Motivation (2): Sideband picture for tuned and detuned SR
Frequency of the light
Carrier(GW-sidebands)
Stefan Hild 7 ILIAS WG1 meeting, Cascina, November 2006
Motivation (2): Sideband picture for tuned and detuned SR
Frequency of the light
Michelson CTRL SB
Michelson CTRL SB
Stefan Hild 8 ILIAS WG1 meeting, Cascina, November 2006
Motivation (2): Sideband picture for tuned and detuned SR
Frequency of the light
Signal recycling CTRL SB
Signal recyclingCTRL SB
Stefan Hild 9 ILIAS WG1 meeting, Cascina, November 2006
Motivation (2): Sideband picture for tuned and detuned SR
Frequency of the light
Comb ofEquidistant SR resonances
Stefan Hild 10 ILIAS WG1 meeting, Cascina, November 2006
Motivation (3): Sideband picture for detuned SR (510 Hz)
• MSR is locked onto upper SB => each SR resonances is 510 Hz left of a FSR of SRC.• Upper SR-SB resonant, lower SR-SB off resonance.• Lower MI-SB nearly resonant, upper MI-SB far off resonance.• Upper and lower GW signal see different completely different resonance condition.
Stefan Hild 11 ILIAS WG1 meeting, Cascina, November 2006
Motivation (4): Sideband picture for tuned SR
• Going form detuned (510Hz) to tuned: comb of SR resonances is shifted 510 Hz to the right.• Upper and lower SR-SB see the same resonance condition (nearly resonant).• Upper and lower MI-SB see the same resonance condition.• Upper and lower GW signal SB see the same resonance condition.
Stefan Hild 12 ILIAS WG1 meeting, Cascina, November 2006
Motivation for tuned SR
There is the possibility:
Get better noise performance due to symmetric sidebands.
Stefan Hild 13 ILIAS WG1 meeting, Cascina, November 2006
Phase noise in P originates from big DC in Q
We believe that a large contribution of the phase noise in P originates from a large DC signal in the Q quadrature.
Therefore it would be nice to reduce the DC signal in Q.
(see Josh‘s talk)
Stefan Hild 14 ILIAS WG1 meeting, Cascina, November 2006
Motivation for tuned SR
There is the possibility:
Get better noise performance due to symmetric sidebands.
Less RF amplitude modulation on main photodiode (reduction of potential saturation / nonlinear effects)
Stefan Hild 15 ILIAS WG1 meeting, Cascina, November 2006
Saturation in our main photo diode
We believe we saw some saturation in the main photodiode due to the large RF amplitude modulation (Q-DC).
The signal voltage (1V @15MHz) modulated the bias voltage (5V) by about 20%.
Problem was for the moment (higher bias, different circuit).
For long term it would be desirable to reduce Q-DC !!
Stefan Hild 16 ILIAS WG1 meeting, Cascina, November 2006
Motivation for tuned SR
There is the possibility:
Get better noise performance due to symmetric sidebands.
Less RF amplitude modulation on main photodiode (reduction of potential saturation / nonlinear effects)
Get simpler noise couplings and transferfunctions.
Get a better understanding of the detector.
--------------------------------------------------------------------
Nice research / demonstration project
Stefan Hild 17 ILIAS WG1 meeting, Cascina, November 2006
Signal-Recycling errorsignal
Nominal operating point,SR detuned,
upper sidebandSR detuned,
lower sidebandtuned SR
Derived from an RF modulation-demodulation technique.
Stefan Hild 18 ILIAS WG1 meeting, Cascina, November 2006
Why can‘t we tune down to tuned SR ?
When we tune below 250 Hz the controlsignal vanishes / goes „cracy“.
Tuning is done by changing the SR RF-modulation frequency.
-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 1010
0
Sig
nal
am
plit
ud
e [a
.u.]
Position of MSR [nm]
-4 -3 -2 -1 0 1 2 3 4
0
Sig
nal
am
plit
ud
e [a
.u.]
Position of MSR [nm]
SR Mod = 9017065 Hz,tuning = 330 HzSR Mod = 9017195 Hz,tuning = 200 HzSR Mod = 9017395 Hz,tuning = 0 Hz
SR Mod = 9016395 Hz,tuning = 1000 HzSR Mod = 9017065 Hz,tuning = 330 Hz
Stefan Hild 19 ILIAS WG1 meeting, Cascina, November 2006
Kicking MSR
Kicking MSR in a controlled way:• Fast enough that all other loops can‘t recognize.• 4 ms of acceleration and 4 ms of deceleration.
Works fine: Jumping to tuned and to the lower SR sideband
Stefan Hild 20 ILIAS WG1 meeting, Cascina, November 2006
Sideband picture for tuned and detuned SR
From detuned to tuned:CTRL-signals that are generated from ‚carrier‘ need to be adjusted for the different resonance condition of the carrier.
Stefan Hild 21 ILIAS WG1 meeting, Cascina, November 2006
Parameter adjustment
When jumping to tuned SR you need to change a few parameters / compensate for the pole of the SR cavity:
• MI long needs an additional differentiator switched in.
• MIAA gains need to be adjusted.
• Swap sign of SR_EP.
• Adjust SR long gain.
Simulations done with FINESSE
Stefan Hild 22 ILIAS WG1 meeting, Cascina, November 2006
Determine the optical gain for P- and Q-quadrature(TF from diff armlength change to detector output)
Stefan Hild 23 ILIAS WG1 meeting, Cascina, November 2006
Optical gain for tuned and detuned SR
Matches our expectations: Bandwidth of the TF goes down by a factor of 2.
102
103
105
Frequency [Hz]
Op
tica
l Gai
n [
]
102
103
-200
-100
0
100
200
Ph
ase
[deg
]
Frequency [Hz]
P Optical Gain, SR tunedQ Optical Gain, SR tunedP Optical Gain, SR tuning = 550 HzQ Optical Gain, SR tuning = 550 Hz
Ph
ase
[deg
]O
pti
cal G
ain
[V
/um
]
Stefan Hild 24 ILIAS WG1 meeting, Cascina, November 2006
Significantly recuded RF AM.
The signal from the Q-quadrature is in the tuned case reduced to nearly zero (red). RMS of Q-signal is reduced by a factor of 12 !!
0 5 10 15 20 25 30-3
-2
-1
0
1Time-series plot
Time [s]
Am
pli
tud
e [V
]
02: G1:LSC_MID_EP-Q_HP-debugtuned SR04: G1:LSC_MID_EP-Q_HP-debugSR detuned (550Hz)
0 5 10 15 20 25 30-0.2
-0.1
0
0.1
0.2
Time [s]
Am
pli
tud
e [V
]
01: G1:LSC_MID_EP-P_HP-debug tuned SR03: G1:LSC_MID_EP-P_HP-debug SR detuned (550Hz)
• Nice for the photodiode: Less potential saturation / nonlinearitis !!
• What is about phase noise in P-quadrature??
Stefan Hild 25 ILIAS WG1 meeting, Cascina, November 2006
OPN coupling @ tuned SR: P dramatically reduced, Q significantly reduced.
MI Oscillator phase noise (OPN)
Stefan Hild 26 ILIAS WG1 meeting, Cascina, November 2006
OAN coupling @ tuned SR: P and Q significantly reduced.
MI Oscillator amplitude noise (OAN)
Stefan Hild 27 ILIAS WG1 meeting, Cascina, November 2006
LIN coupling @ tuned SR: P and Q significantly reduced.
Laser intensity noise (LIN)
Stefan Hild 28 ILIAS WG1 meeting, Cascina, November 2006
Laser freq noise coupling @ tuned SR: P and Q worse (but structure slightly simpler).
Laser frequency noise
Stefan Hild 29 ILIAS WG1 meeting, Cascina, November 2006
Summary of noise couplings
• OPN coupling @ tuned SR: P dramaticcaly reduced, Q significantly reduced.
• OAN coupling @ tuned SR: in both quadratures clearly reduced.
• Laser frequency noise coupling @ tuned SR: worse in both quadratures.
• Laser intensity noise coupling @ tuned SR: P and Q significantly reduced.
In general:The size of TFs for the noise couplings are reduced on average and the structure of the TFs look a bit simpler.
Stefan Hild 30 ILIAS WG1 meeting, Cascina, November 2006
Calibration to starin sensitivity (frequency domain)
Stefan Hild 31 ILIAS WG1 meeting, Cascina, November 2006
Sensitivity: tuned vs detuned (550Hz) SR
102
103
10-22
10-21
10-20
10-19
10-18
Frequency [Hz]
STR
AIN
[1/
sqrt
(Hz)
]
01: G1:DER_DATA_HPfs = 8192 : 100s from 2006-09-07 00:00:00 - nfft=8192, nolap=0.50, enbw=1.5, navs=199Tuned SR, Pwr = 75 deg, HP
102
103
10-22
10-21
10-20
10-19
10-18
Frequency [Hz]
STR
AIN
[1/
sqrt
(Hz)
]
03: G1:DER_DATA_HQfs = 8192 : 100s from 2006-09-07 00:00:00 - nfft=8192, nolap=0.50, enbw=1.5, navs=199Tuned SR, Pwr = 75 deg, HQ
No improvement in sensitivity
(not surprising, as we are not limited by shotnoise at low frequencies and we did not optimize the detector / parameters for tuned SR)
Stefan Hild 32 ILIAS WG1 meeting, Cascina, November 2006
Noise projections for a time of S5
So far we don‘t understand why Q got worse
at high frequencies for tuned SR. (?)
Stefan Hild 33 ILIAS WG1 meeting, Cascina, November 2006
Summary
• Demonstrated controlled jumping to tuned SR.
• No sensitivity improvement for tuned SR at the moment (spend no time for optimization).
• Some of the noise couplings are significantly reduced for tuned, but their structure is still complicated.
• In tuned case the RF AM is reduced by a factor of 12
Outlook:To gain understanding of the noise couplings: seems important in order to speed up comissioning of GEO is essential for good design of next generation of instruments
Stefan Hild 34 ILIAS WG1 meeting, Cascina, November 2006
E n d
Stefan Hild 35 ILIAS WG1 meeting, Cascina, November 2006
Acquisition of Dual Recycling
9.01...MHz
14.905MHz