Robert Ward NAOJ seminar, March 1, 2006 1 The Caltech 40m
Prototype Detuned RSE Interferometer Robert Ward NAOJ seminar March
1, 2006 Osamu Miyakawa, Rana Adhikari, Matthew Evans, Benjamin
Abbott, Rolf Bork, Daniel Busby, Hartmut Grote, Jay Heefner,
Alexander Ivanov, Seiji Kawamura, Michael Smith, Robert Taylor,
Monica Varvella, Stephen Vass, and Alan Weinstein Slide 2 Robert
Ward NAOJ seminar, March 1, 2006 2 Signal and power enhancement
using Fabry-Perot cavity in each arm Power enhancement using Power
Recycling Michelson interferometer as a gravitational wave detector
Gravitational wave detection using Michelson interferometer BS FP
cavity Laser PRM BS FP cavity Laser Slide 3 Robert Ward NAOJ
seminar, March 1, 2006 3 LIGO:Power recycled FPMI Optical noise is
limited by Standard Quantum Limit (SQL) AdvLIGO:GW signal
enhancement using Detuned RSE Two dips in the quantum noise due
optical spring, optical resonance Has the potential to beat the SQL
QND detector Or allows quantum noise curve to be optimized in the
presence of thermal noise Advanced LIGO optical configuration
Detuning PRM BS FP cavity Laser GW signal Power Slide 4 Robert Ward
NAOJ seminar, March 1, 2006 4 AdLIGO noise curve Bench Active
Seismic Isolation External Seismic Pre- Isolation Quadruple
pendulum suspensions 40 kg, fused silica Test Masses 125W Laser
Fight the Fundamental Noise Sources: 1)Seismic 2)Thermal 3)Quantum
Slide 5 Robert Ward NAOJ seminar, March 1, 2006 5 Resonant Sideband
Extraction and Signal Recycling Resonant Sideband Extraction(RSE)
Decrease storage time of GW signal in IFO Allows high finesse arm
cavities Low power recycling, or power recycling not required Less
thermal effects Signal Recycling(SR) Increase storage time of GW
signal in IFO Low finesse arm cavities, or arm cavities not
required High power recycling required, so-called dual
recycling(DR) Higher thermal effects GEO600 AdLIGO LCGT LIGO VIRGO
TAMA300 Slide 6 Robert Ward NAOJ seminar, March 1, 2006 6 Caltech
40 meter prototype interferometer Objectives Develop a lock
acquisition procedure for suspended-mass detuned RSE interferometer
with power recycling, preferably one that will be applicable to
Advanced LIGO BS PRM SRM X arm Dark port Bright port Y arm
Characterize and optimize optical configuration (for robust control
and sensitivity) Characterize noise mechanisms Develop DC readout
scheme Test QND techniques Extrapolate to AdLIGO via simulation
Prototyping will yield crucial information about how to build and
run AdLIGO Slide 7 Robert Ward NAOJ seminar, March 1, 2006 7
Pre-Stabilized Laser(PSL) and 13m Mode Cleaner(MC) 10W MOPA126
Frequency Stabilization Servo (FSS) Intensity Stabilization Servo
Pre-Mode Cleaner (PMC) 13m Mode Cleaner MOPA126 FSS VCO AOM PMC 13m
MC 40m arm cavity PSL Detection bench Mode Cleaner BS ITMy ITMx
South Arm East Arm ETMx ETMy Slide 8 Robert Ward NAOJ seminar,
March 1, 2006 8 LIGO-I type single suspension Each optic has five
OSEMs (magnet and coil assemblies), four on the back, one on the
side The magnet occludes light from the LED, giving position
Current through the coil creates a magnetic field, allowing mirror
control Slide 9 Robert Ward NAOJ seminar, March 1, 2006 9 40m
Sensitivity Bench Not very likely that well actually detect any
gravitational waves here, but hopefully well learn some things
about operating interferometers, especially about the quantum
noise. Slide 10 Robert Ward NAOJ seminar, March 1, 2006 10 40m DARM
Optical Plant The 40m operates in a detuned RSE configuration,
which gives rise to two peaks in the DARM transfer function:
1)Optical Resonance 2)Optical Spring UGF Slide 11 Robert Ward NAOJ
seminar, March 1, 2006 11 Detune Cartoon Responses of GW USB and GW
LSB are different due to the detuning of the signal recycling
cavity. IFO Differential Arm mode is detuned from resonance at
operating point DARM Carrier frequency frequency offset from
carrier [Hz] Sideband amplitude [a.u.] FWHM USB LSB f sig IFO
DARM/CARM slope related to spring constant IFO Common Arm mode is
detuned from resonance at intial locking point PRCCARM SRC Slide 12
Robert Ward NAOJ seminar, March 1, 2006 12 Signal Extraction Scheme
Arm cavity signals are extracted from beat between carrier and f 1
or f 2. Central part (Michelson, PRC, SRC) signals are extracted
from beat between f 1 and f 2, not including arm cavity
information. Only +f 2 sideband resonates in combined PRC+SRC
Double demodulation Central part information f1f1 -f 1 f2f2 -f 2
Carrier Single demodulation Arm information PRM Slide 13 Robert
Ward NAOJ seminar, March 1, 2006 13 5 DOF for length control : L =(
L x L y ) / 2 : L = L x L y : l =( l x l y ) / 2 =2.257m : l = l x
l y = 0.451m : l s =( l sx l sy ) / 2 =2.15m Por t Dem. Freq. LL LL
ll ll l s SPf1f1 10-0.00100 APf2f2 0100.0010 SP f1 f2f1 f2
-0.002-0.0011-0.032-0.100 AP f1 f2f1 f2 -0.0010.0020.75010.070 PO
f1 f2f1 f2 0.0040.0030.460-0.0231 Signal Extraction Matrix
(in-lock, DC) Common of arms Differential of arms Power recycling
cavity Michelson Signal recycling cavity Laser ETMx ETMy ITMy ITMx
BS PRM SRM SP AP PO lxlx lyly l sx l sy L x =38.55m Finesse=1235 L
y =38.55m Finesse=1235 Phase Modulation f 1 =33MHz f 2 =166MHz 40m
Slide 14 Robert Ward NAOJ seminar, March 1, 2006 14 Disturbance by
sidebands of sidebands Sidebands of sidebands are produced by two
series EOMs. Beats between carrier and f 2 +/- f 1 disturb central
part. Original concept Real world f1f1 -f 1 f2f2 -f 2 Carrier f 1
=33MHz-f 1 f 2 =166MHz-f 2 Carrier PortDem. Freq. LL LL ll ll l s
SPf1f1 10-.00100 APf2f2 010.0010 SP f1 f2f1 f2 7.401-.033-.110 AP
f1 f2f1 f2 -0.00132.7101.071 PO f1 f2f1 f2 3.31.7.190-.0351 199MHz
133MHz Slide 15 Robert Ward NAOJ seminar, March 1, 2006 15
Mach-Zehnder interferometer on 40m PSL to eliminate sidebands of
sidebands Series EOMs with sidebands of sidebands EOM2 EOM1
Mach-Zehnder interferometer with no sidebands of sidebands PD EOM2
EOM1 PZT PMC trans To MC Locked by internal modulation f1f1 f2f2
f1f1 f2f2 PMC transmitted to MC Slide 16 Robert Ward NAOJ seminar,
March 1, 2006 16 Real Time Digital Control System Suspension
controllers Length Sensing and Control Interface to Operators Data
Acquisition Fiber communication network 16kHz Sampling Rate Also
have an extensive slow controls network (EPICS) Slide 17 Robert
Ward NAOJ seminar, March 1, 2006 17 Digital length sensing and
control system AP166 A/D mixer D/A Provides great flexibility to
try out new control/locking schemes Easy to optimize control matrix
Slide 18 Robert Ward NAOJ seminar, March 1, 2006 18 Digital
Controller Flexibility digital filtering smooth signal handoff
Diagnostics arbitrary transfer functions Reconfigurability
construct new control links, servos rapidly quickly change MIMO
servo filter Optimization can do automatic matrix diagonalization
Automation Slide 19 Robert Ward NAOJ seminar, March 1, 2006 19
Automation of Routine Tasks Using the digital control system, we
use shell scripts to automate routine tasks. Restores alignment of
ETM, ITM, mis-aligns other optics, sets up loop gains and control
flow, and engages lock acquisition routine. Steers ITM to center
transmitted beam on QPD, dithers input beam and ETM alignment,
servos to minimize dither signal in power level. Slide 20 Robert
Ward NAOJ seminar, March 1, 2006 20 Control Setting Log (conlog)
Constantly records all digital control settings (thousands of
channels). Log files accessible through a simple web interface
Useful for operators, commissioners, and data analysts. Slide 21
Robert Ward NAOJ seminar, March 1, 2006 21 40m Goal #1: Develop a
Lock Acquisition procedure for AdLIGO Version 1.0: Basically a
Brute Force technique All optics are aligned, all DOFs are
swinging. Do some fast normalization, switching on/off of feedback:
try to grab control without pumping too much energy into the system
Works much better with large available signals, strong actuators.
Suitability of procedure for AdLIGO to be extrapolated via
simulation. Slide 22 Robert Ward NAOJ seminar, March 1, 2006 22
Transmitted light is used as 40m Lock Acquisition part I:
Off-resonant lock scheme for a single cavity Off-resonant Lock
point Resonant Lock 10x higher finesse than LIGO Slide 23 Robert
Ward NAOJ seminar, March 1, 2006 23 40m Lock acquisition procedure
(v 1.0) Start with no DOFs controlled, all optics aligned. ITMy
ITMx BS PRM SRM SP DDM 13m MC 33MHz 166MHz SP33 SP166 AP DDM AP166
PO DDM Slide 24 Robert Ward NAOJ seminar, March 1, 2006 24 40m Lock
acquisition procedure (v 1.0) DRMI + 2arms with CARM offset ITMy
ITMx BS PRM SRM SP DDM 13m MC 33MHz 166MHz SP33 SP166 AP DDM AP166
PO DDM Average wait : 3 minute (at night, with tickler) T =7% I Q
1/sqrt(TrY) 1/sqrt(TrX) MICH: SP33Q PRC: SP33I SRC PO133I XARM: DC
lock YARM DC lock Less than 1% of maximum circulating power Slide
25 Robert Ward NAOJ seminar, March 1, 2006 25 40m Lock acquisition
procedure (v 1.0) ITMy ITMx BS PRM SRM SP DDM 13m MC 33MHz 166MHz
SP33 SP166 AP DDM AP166 To DARM PO DDM AP166 / sqrt(TrX+TrY) CARM
DARM + + Short DOFs -> DDM DARM -> RF signal CARM -> DC
signal 1/sqrt(TrX)+ 1/sqrt( TrY) CARM -> Digital CM_MCL servo
All done by script, automatically Slide 26 Robert Ward NAOJ
seminar, March 1, 2006 26 40m Lock acquisition procedure (v 1.0)
Reduce CARM offset: 1. Go to higher ARM power (10%) 2. Switch on
AC-coupled analog CM servo, using REFL DC as error signal. 3.
Switch to RF error signal (POX) at half-max power. 4. Reduce
offset/increase gain of CM. ITMy ITMx BS PRM SRM SP DDM 13m MC
33MHz 166MHz SP33 SP166 AP DDM AP166 To DARM REFL DARM PO DDM AP166
/ (TrX+TrY) script 1900W Slide 27 Robert Ward NAOJ seminar, March
1, 2006 27 DARM Optical response with fit to Buonanno & Chen
formula DARMin1 / DARMout ---------------------------- XARMin1 /
XARMout times arm cavity pole. Yields optical response, taking out
pendulum, analog & digital filtering, etc. XARM TF is
understood semi-quantitatively. Offset-locked CARM also has optical
spring peak, also well modeled. Anti-spring TF also well modeled.
Slide 28 Robert Ward NAOJ seminar, March 1, 2006 28 The DARM
anti-spring With SRM detuned in the wrong direction, will see an
anti- spring in DARM This is equivalent to resonating the f2 RF
sideband in SRC. Oddly, this is also easier to lock Slide 29 Robert
Ward NAOJ seminar, March 1, 2006 29 Detune Cartoon Responses of GW
USB and GW LSB are different due to the detuning of the signal
recycling cavity. IFO Differential Arm mode is detuned from
resonance at operating point DARM Carrier frequency frequency
offset from carrier [Hz] Sideband amplitude [a.u.] FWHM USB LSB f
sig IFO DARM/CARM slope related to spring constant IFO Common Arm
mode is detuned from resonance at intial locking point PRCCARM SRC
Slide 30 Robert Ward NAOJ seminar, March 1, 2006 30 Simple picture
of optical spring in detuned RSE Move arms differentially, X arm
longer, Y arm shorter from operating point Power X arm down, Y arm
up X arm down, Y arm down X arm up, Y arm down Radiation pressure X
arm down, Y arm up X arm down, Y arm down X arm up, Y arm down
Spring constant Negative(optical spring) N/A Positive(no optical
spring) DARM (Lx-Ly) Power(W) BRSE Correct SRM position Wrong SRM
position X arm Y arm Slide 31 Robert Ward NAOJ seminar, March 1,
2006 31 Changing the DARM quadrature 1.Lock IFO with CARM offset
2.Handoff DARM to RF 3.Adjust RF demodulation phase 4.Reduce CARM
offset 5.This changes the quadrature of the signal. As we are not
compensating for this by adjusting the demod phase, the shape of
the response changes. demodulation phase b1 b2 Unbalanced Sideband
Detection: Slide 32 Robert Ward NAOJ seminar, March 1, 2006 32
Changing the DARM quadrature Squares are data, solid lines are from
Optickle. Optickle results are generated by measuring response in a
single quadrature while changing the CARM offset. This should be
analogous to how the data was taken (reducing the CARM offset while
always measuring with the same RF demod phase). Blackboard Slide 33
Robert Ward NAOJ seminar, March 1, 2006 33 CARM optical springs
Solid lines are from TCST Stars are 40m data Max Arm Power is ~80
Also saw CARM anti-springs, but dont have that data Slide 34 Robert
Ward NAOJ seminar, March 1, 2006 34 Relationship between the CARM
and DARM springs at the 40m With the 40m Lock Acquisition scheme,
we only see a CARM spring if theres also a DARM spring.
XarmYarmDARMCARM ++xx --0+ +-xx -++- Using the DC-locking scheme
for the arms, there are, prima facie, four locking points
corresponding to the four possible gain combinations, but only two
will acquire lock. XarmYarmDARMCARM ++0- --xx +--+ -+xx Correct SRM
position Incorrect SRM position Slide 35 Robert Ward NAOJ seminar,
March 1, 2006 35 Will it lock? NO YES x-axis: EY position y-axis:
signal blue:X err green: Y err black: DARM red: CARM modeled with
FINESSE (open loop) Slide 36 Robert Ward NAOJ seminar, March 1,
2006 36 Compensating the resonances 4kHz >> UGF no
compensation AdLIGO: 180 Hz ~ UGF 40Hz < UGF no compensation
AdLIGO: 70Hz? 1kHz -> 100Hz ~ UGF dynamic
compensationcompensation 0->100Hz ~ UGF Not yet coherently
compensated Compensation Filters for the two resonances associated
with the signal cavity: OpticalOpto-mechanical DARM CARM UGFs ~
250Hz Slide 37 Robert Ward NAOJ seminar, March 1, 2006 37 Dynamic
compensation filter for CARM servo Optical gain of CARM Open loop
TF of CARM Optical gain (normalized by transmitted arm power) shows
moving peaks due to reducing CARM offset. We have a dynamic
compensative filter having nearly the same shape as optical gain
except upside down. Designed using FINESSE. Open loop transfer
function has no phase delay in all CARM offset. Slide 38 Robert
Ward NAOJ seminar, March 1, 2006 38 Mode healing/injuring at Dark
Port Negative spring constant with optical spring Positive spring
constant with no optical spring Repeatable The same alignment
quality Carrier power at DP is 10x smaller Slide 39 Robert Ward
NAOJ seminar, March 1, 2006 39 Next steps Stable operation and
noise hunting More lock acquisition schemes More lock acquisition
schemes Modeling/E2E simulation for AdLIGO Modeling/E2E simulation
for AdLIGO DC readout with Output Mode Cleaner DC readout with
Output Mode Cleaner Squeezed Vacuum in the Dark Port Squeezed
Vacuum in the Dark Port Active Alignment control with wave front
sensors LF RF modulation scheme Alternatives to Mach-Zender
Alternatives to Mach-Zender Slide 40 Robert Ward NAOJ seminar,
March 1, 2006 40 Other Lock Acquisition Schemes Alternative Locking
Schemes are on the way! Deterministic Locking: Locking occurs in
stages, with each stage having robust control Each stage can (and
should) lock on the first fringe, or be robust to fringes.
Transitions between stages are smooth and robust: example-PR-FPMI
Advantages: Easier to diagnose problems Should require less
actuation potential If we can lock a single arm cavity, we can lock
the IFO. No statistical characterization (i.e., mean-time-to-lock).
40M: 7 mN 1.3 kg test mass f/m = 5 AdLIGO 200 N 40 kg test mass f/m
=5e-3 Slide 41 Robert Ward NAOJ seminar, March 1, 2006 41
Deterministic Locking: PRFPMI Example Procedure to lock the PRFPMI:
Mis-align PRM,SRM Lock ARMs with DC-signal (offset) normalized by
power in recycling cavity Lock MICH with DC-signal (offset) dark
port power normalized recycling cavity power Slowly re-align the
PRM Stable in this stage (power in IFO fluctuates as PRM swings,
but the other optics are not disturbed as this power is normalized
out) Lock PRC with SP33I Reduce MICH offset, handoff to SP33Q
Reduce ARM offset (not done yet) Slide 42 Robert Ward NAOJ seminar,
March 1, 2006 42 e2e SIMULATION: 4Om/AdvLIGO package Comparison
between real data (black) and e2e simulated data (red) of the
transmitted light for both the arms (full IFO): the mirror
velocities used in E2E simulation are the values obtained fitting
the real data Real data have been used to estimate relative mirror
velocity for both the arms: V xarm = (0.35 0.13) m/s V yarm = (0.26
0.13) m/s E2E real data Tr X Tr Y Slide 43 Robert Ward NAOJ
seminar, March 1, 2006 43 E2E DARM TF to I and Q 5W Input Arms
controlled with POX, POY (no DARM) no MICH control Hiro Yamomoto
Slide 44 Robert Ward NAOJ seminar, March 1, 2006 44 Optickle:
Frequency Domain IFO Simulation Optickle is a new frequency domain
IFO modeling tool: Written in Matlab Matlab allows easy integration
to other modeling efforts (a frequency- domain e2e, like LinLIGO)
Easily Extensible Uses Matlab classes for generality Uses the
methods outlined in T. Corbitt et al: Mathematical framework for
simulation of quantum fields in complex interferometers using the
two-photon formalism ( LIGO-P030071-00R ) to calculate the IFO
opto-mechanical frequency response. Designed for concrete units
(Watts, meters, Hz) Slide 45 Robert Ward NAOJ seminar, March 1,
2006 45 Optickle example: detuned FP cavity Response of front
mirror to back mirror excitation 1 nm detune finesse ~ 1200 Slide
46 Robert Ward NAOJ seminar, March 1, 2006 46 Optickle Example:
AdLIGO Easy to create a frequency dependent coupling matrix, useful
for, e.g., estimating the contribution of loop noise to DARM. This
plot is Open Loop. Closed loop coming soon! Slide 47 Robert Ward
NAOJ seminar, March 1, 2006 47 DC Readout Quantum Noise: Heterodyne
vs Homodyne Quantum noise curves plotted using formulas in: A.
Buonanno, Y. Chen, N. Mavalvala, Quantum noise in
laser-interferometer gravitational-wave detectors with a heterodyne
readout scheme PHYSICAL REVIEW D 67,122005 2003 Slide 48 Robert
Ward NAOJ seminar, March 1, 2006 48 What is DC Readout and how does
it relate to Homodyne Detection? DC Readout is Homodyne detection,
using light circulating in the interferometer as a local
oscillator. Advantage: LO light has been filtered by the
