40m TAC, 10/13/05 1 Report to the 40m Technical Advisory Committee October 13, 2005 The 40m Team Ben...
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Transcript of 40m TAC, 10/13/05 1 Report to the 40m Technical Advisory Committee October 13, 2005 The 40m Team Ben...
40m TAC, 10/13/05 1
Report to the 40m Technical Advisory Committee
October 13, 2005
The 40m TeamBen Abbott, Rana Adhikari, Dan Busby, Jay Heefner, Osamu
Miyakawa, Mike Smith, Bob Taylor, Monica Varvella, Steve Vass, Rob Ward, Alan Weinstein
with lots of help from: Matt Evans, Helena Armandula, Rolf Bork, Alex Ivanov, SURF students, etc…
40m TAC, 10/13/05 2
Status as of October 2005
Slides 3 through 11: presented at August LSC meeting, included for your review, skip for now.
Status of lock acquisition (Rob, Osamu, Matt, Rana) e2e simulation (Monica) DC readout (Smith, AJW, all) Proposal for squeezing-enhanced gravitational wave
interferometer at the 40m (Nergis)
40m TAC, 10/13/05 3
Caltech 40 meter prototype interferometer
Objectives Develop lock acquisition procedure of detuned Resonant Sideband
Extraction (RSE) interferometer, as close as possible to AdLIGO optical design
BSPRM SRM
X arm
Darkport
Brightport
Y arm
Characterize noise mechanisms Verify optical spring and optical
resonance Develop DC readout scheme Extrapolate to AdLIGO via
simulation
40m TAC, 10/13/05 4
AdLIGO signal extraction scheme
Arm cavity signals are extracted from beat between carrier and f1 or f2.
Central part (Michelson, PRC, SRC) signals are extracted from beat between f1 and f2, not including arm cavity information.
f1-f1 f2-f2
Carrier (Resonant on arms)
• Single demodulation• Arm information
• Double demodulation• Central part information
Mach-Zehnder installed to eliminate sidebands of sidebands.
Only + f2 is resonant on SRC. Unbalanced sidebands of +/-f2 due
to detuned SRC produce good error signal for Central part.
ETMy
ETMx
ITMy
ITMxBSPRM
SRM
4km
4k
mf2
f1
40m TAC, 10/13/05 5
5 DOF for length control
: L=( Lx Ly) / 2
: L= Lx Ly
: l=( lx ly) / 2
=2.257m: l= lx ly = 0.451m
: ls=( lsx lsy) / 2
=2.15m
Port Dem. Freq.
L L l l l s
SP f1 1 -3.8E-9 -1.2E-3 -1.3E-6 -2.3E-6
AP f2 -4.8E-9 1 1.2E-8 1.3E-3 -1.7E-8
SP f1 f2 -1.7E-3 -3.0E-4 1 -3.2E-2 -1.0E-1
AP f1 f2 -6.2E-4 1.5E-3 7.5E-1 1 7.1E-2
PO f1 f2 3.6E-3 2.7E-3 4.6E-1 -2.3E-2 1
Signal Extraction Matrix (in-lock)
Common of armsDifferential of armsPower recycling cavity
MichelsonSignal recycling cavity
Laser
ETMy
ETMx
ITMy
ITMxBS
PRM
SRM
SPAP
PO
lx
ly
lsx
lsy
Lx =38.55m
Finesse=1235
Ly=38.55m
Finesse=1235Phase Modulationf1=33MHzf2=166MHz
T =7%
T =7%
GPR=14.5
40m TAC, 10/13/05 6
Differences betweenAdvLIGO and 40m prototype
100 times shorter cavity length Arm cavity finesse at 40m chosen to be = to AdvLIGO ( = 1235 )
» Storage time is x100 shorter.
Control RF sidebands are 33/166 MHz instead of 9/180 MHz» Due to shorter PRC length, less signal separation.
LIGO-I 10-watt laser, negligible thermal effects» 180W laser will be used in AdvLIGO.
Noisier seismic environment in town, smaller stack» ~1x10-6m at 1Hz.
LIGO-I single pendulum suspensions are used» AdvLIGO will use triple (MC, BS, PRM, SRM) and quad (ITMs, ETMs)
suspensions.
40m TAC, 10/13/05 7
DRMI lock using double demodulation with unbalanced sideband by detuned cavity
August 2004August 2004DRMI locked with carrier resonance (like GEO configuration)DRMI locked with carrier resonance (like GEO configuration)November 2004November 2004DRMI locked with sideband resonance (Carrier is anti resonant preparing for RSE.)DRMI locked with sideband resonance (Carrier is anti resonant preparing for RSE.)
Carrier
33MHz
Unbalanced166MHz
Belongs tonext carrier
Belongs tonext carrier
Carrier33MHz166MHz
ITMy
ITMxBS
PRM
SRM
OSA DDM PD
DDM PD
DDM PD
Typical lock acquisition time : ~10secLongest lock : 2.5hour
40m TAC, 10/13/05 8
Lock acquisition procedure towards detuned RSE
ITMy
ITMxBSPRM
SRM
ETMx
ETMy
Shutter
Shutter
Carrier33MHz166MHz
DRMI using DDM Off-resonantarms using DC lock
(POX/TrX),(POY/TrY)
SP166/PRC,AP166/PRC
(POX/TrX) + (POY/TrY), (POX/TrX) – (POY/TrY)
(TrX + TrY), (TrX – TrY) / (TrX + TrY)
Ideas for armcontrol signal
RSE
Done In progressDone
40m TAC, 10/13/05 9
All 5 degrees of freedom under controlledwith DC offset on L+ loop
Both arms locked with DRMIBoth arms locked with DRMI Lock acquisition time ~1 minLock acquisition time ~1 min Lasts ~ 20 minLasts ~ 20 min Can be switched to Can be switched to
common/differential controlcommon/differential controlLL- : AP166 with no offset- : AP166 with no offsetLL+ : Trx+Try with DC offset+ : Trx+Try with DC offset
Yarm lockXarm lock
Arm power
Error signal
Ideal lockpoint
Offset lockOffset lock
Have started trying toreduce offset from L+ loop
But…
40m TAC, 10/13/05 10
Progress in last 6 months
For the last 6 months , we have been able to control all 5DOF, but with CARM offset.
Reducing the CARM offset has been made difficult by technical noise sources. We have spent last 6months reducing them;
»suspension noise, vented to reduce couplings in ITMX
»improved diagonalization of all suspensions
»improved frequency noise with common mode servo
»automation of alignment and lock acquisition procedures
»improved DC signals and improved RF signals for lock acquisition.
We can now routinely lock all 5 DOFs in a few minutes at night.
40m TAC, 10/13/05 11
-150
-100
-50
0
50
100
150
Pha
se[d
eg]
102 3 4 5 6 7 8
1002 3 4 5 6 7 8
10002 3 4 5 6
Frequency[Hz]
50
40
30
20
10
0
-10
-20
Mag
[dB
]
Measured optical gain Calculated by Thomas's tool
RSE peak
RSE peak!• Optical gain of L- loop
DARM_IN1/DARM_OUT divided by pendulum transfer function
• No offset on L- loop• ~60pm offset on L+ loop• Phase includes time delay of
the digital system.
• Optical resonance of detuned RSE can be seen around the design RSE peak of 4kHz.
• Q of this peak is about 7.• Effectively the same as Full
RSE with GPR=1.4 with 1W input laser.
• Model was calculated by Thomas’s tool.
• We will be looking for optical spring peak.
Design RSEpeak ~ 4kHz
40m TAC, 10/13/05 12
Lock acquisition procedure towards detuned RSE
Start withno DOFscontrolled, all optics aligned.Re-align each 1.5 hours.
ITMy
ITMxBS
PRM
SRM
SP DDM
13m MC
33MHz
166MHz
SP33SP166
AP DDM
AP166
PO DDM
40m TAC, 10/13/05 13
Lock acquisition procedure towards detuned RSE
DRMI + 2armswith offset
ITMy
ITMxBS
PRM
SRM
SP DDM
13m MC
33MHz
166MHz
SP33 SP166
AP DDM
AP166
PO DDM
Average wait : 1 minute (at night, with tickler)
T =7%
T =7%IQ
1/sqrt(TrY)
1/sqrt(TrX)
40m TAC, 10/13/05 14
Lock acquisition procedure towards detuned RSE
Scripto-matic:
ITMy
ITMxBS
PRM
SRM
SP DDM
13m MC
33MHz
166MHz
SP33 SP166
AP DDM
AP166To DARM
PO DDM
AP166 / (TrX+TrY)
CARM
DARM+
-1+
Short DOFs -> DDMDARM -> RF signalCARM -> DC signal
1/sqrt(TrX)+ 1/sqrt( TrY)
Discretionary:CARM -> Digital
CM_MCL servo
40m TAC, 10/13/05 15
Lock acquisition procedure towards detuned RSE
Reduce CARM offset:Go to higher ARM power, switch
on AC-coupled analog CM_AO servo,
using REFL DC as error signal.
Locks somewhat stable at 85% of
maximum power.
ITMy
ITMxBS
PRM
SRM
SP DDM
13m MC
33MHz
166MHz
SP33
SP166
AP DDM
AP166To DARMREFL
DARM-1
PO DDM
AP166 / (TrX+TrY)
GPR=5
Up next:
RF control of CARM: REFL166 (POX/POY 33 ?)
40m TAC, 10/13/05 16
Ready for Transition to RF CARM
40m TAC, 10/13/05 17
Progress in last 2 months
Use CARM DC signal to creep closer to full arm resonance (signal goes away at resonance)
» combined PRC and arm gain as high as 60, 85% of the way to peak, corresponding to offset of 8 pm, assuming arm losses of 200ppm (inferred).
Progress due largely to improvements in loop filtering, to obtain more gain and reduce noise
Significant improvements in automation of lock procedures. All DOFs diagonalized: 3x3 (SRC/PRC/MICH) + 2x2 (DARM/CARM) Lock is lost because of large frequency noise (presumably). Effort to reduce frequency noise using CM servo
» digital CM servo to MC works well» analog servo using DC signal seems to work, RF under development» frequency noise may be coming from in-vac PZTs. Not beam jitter noise.
Much effort to reduce other noise sources» better diagonalization of MC suspensions, core optics suspensions» continual battle with 60 Hz harmonics
40m TAC, 10/13/05 18
Development of e2e simulation: 4Om/AdvLIGO package
Monica Varvella (visitor from LAL/Orsay) has developed a 4Om/AdvLIGO package with a DRFPMI optical plant, and is developing the control plant with help from Matt Evans and Hiro Yamamoto
Tests include a careful comparison with Twiddle, as well as comparison of error signal sweeps between simulation and 40m data.
Can be used to extract the velocity of the mirrors in the 40m under controlled circumstances: lock all degrees of freedom, CARM offset, and then HOLD the CARM servo and watch error signal as mirrors sweep through arm resonance.
40m TAC, 10/13/05 19
Error signal sweeps at 10-9 m/s for the 40m IFO obtained in
E2E framework and compared with TWIDDLE predictions
Example:DARM @ AP 166 MHz
TWIDDLE and E2E comparison
e2e SIMULATION:4Om/AdvLIGO package
TWIDDLE
E2E
40m TAC, 10/13/05 20
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:
Vxarm= (0.35 ± 0.13) μm/s
Vyarm= (0.26 ± 0.13) μm/s
E2E
E2E
real data
real data
Tr X
Tr Y
40m TAC, 10/13/05 21
e2e SIMULATION: 4Om/AdvLIGO package
Comparison between real data , e2e simulated data and the
theoretical prediction V(t) of the SP error signal @ 166 MHz
The τ and the velocity v is the value obtained fitting real data
τ = 0.7 msv = 0.26 μm/s
V(t) ~ exp(t/τ) sin( a t2)
with a = (k v) / (2 T)
40m TAC, 10/13/05 22
DC Readout at the 40m DC Readout eliminates several sources of technical noise (mainly due to the RF
sidebands): – Oscillator phase noise – Effects of unstable recycling cavity. – The arm-filtered carrier light will serve as a heavily stabilized local
oscillator. – Perfect spatial overlap of LO and GW signal at PD.
DC Readout has the potential for QND measurements, without major modifications to the IFO.
We may not be able to see shot noise at low frequency, given our noise environment. We may not even see any noise improvements, but we might!
The most important thing we will learn is : How to do it » How to lock it?» How best to control the DARM offset?» What are the unforeseen noise sources associated with an in-vacuum OMC?» How do we make a good in-vac photodiode? What unforeseen noise
sources are associated with it?
40m TAC, 10/13/05 23
DC readout equipment
Most in-vac optics and opto-mechanics have been ordered» Most mirror mounts and mirrors» Output mode-matching telescope with picomotor focus» two Piezo-Jena steering mirrors» but NOT the PZT drivers. Jay Heefner has committed to designing these (also
maybe needed at sites for RBS system). Design based on IO PZTs. Need strain gauge readback.
OMC design from Mike Smith» 4-mirror design» super-mirrors with REO coatings coming from LIGO Lab spares
DC PD assembly and electronics under design (Abbott, Adhikari) OMC control, DC PD readout, and monitoring electro-optics and
readout, under design (Heefner), mostly using existing infrastructure and equipment.
Alignment on bench, in air, and in vacuum seem feasible.
40m TAC, 10/13/05 24
Output Optical Train
Mike Smith
SRM
1st PZT steering mirror
2nd PZT steering mirror
gets a little tightaround IMMT
OOC IOC
BSC
40m TAC, 10/13/05 25
Output Optic Chamber
Mike Smith
from SRM
to AS RF beamline(roughly 1/3 of AS power)
also a convenient path for autocollimator beam, for initial alignment in air
to OMCR beamline
to OMCT beamline
from PSL to IMC
IMCR, IMCT, and SP beamlines
2nd PZT steering mirror
PZT steering mirrors and their controls are duplicates of a pair that we have
already installed and commissioned for steering from IMC to main IFO (in-vac);
controls are fully implemented in the ASC system (by Rolf). Similar systems
can be used for “LIGO I.V”.
Piezosystem Jena PSH 5/2 SG-V, PZT tilting mirror mount with strain gauge, and associated drivers and
power supplies
Existing in-vac seismically isolated
optical table (OOC)Mike Smith has designed a
compact, monolithic MMT, similar to our input MMT, using spherical
mirrors.
4-mirror monolithic OMC.Pair of DC PDswith in-vac electronics
on monolithic base.
40m TAC, 10/13/05 26
OMC, four mirror design
Mike Smith
• Mirrors mounted mechanically, on 3 points (no glue)• curved mirror: off-the-shelf CVI laser mirror with ROC = 1 m ± 0.5%• Fixed spacer should be rigid, vented, offset from table OMC length signal:
Dither-lock? >> Should be simple; we’ll try this first. PDH reflection? >> There’s only one sideband, but it will still work.
Servo: Will proceed with a simple servo, using a signal generator and a lock-in amp. Feedback filters can easily be analog or digital.
Can use a modified PMC servo board for analog. Can use spare ADC/DAC channels in our front end IO processor for digital.
PZT actuation
From MMT
to DCPD
PZT mirror
SS fixed spacer
~ 20 cm
reflected beam
mechanical clamps
(no glue)
40m TAC, 10/13/05 27
OMC design in SolidWorks Small number of pieces HV compatible
» a bit of glue on the PZT mirror Mirrors mounted mechanically,
on silver washers (no glue) ALGOR FEA: lowest mech
resonance at ~770 Hz Construct out of well-damped
material, to minimize effect of resonances
» Brass? Copper?» Or just stick with aluminum?
All high-quality (REO super-polished and coated) mirrors available from LIGO lab spares (well, the 4th HR mirror, 0o incidence, may need to come from Newport) Mike Smith
40m TAC, 10/13/05 28
In-vac DC photodiodes
Three views of an in-vacuum DC PD assembly, showing a 50% beamsplitter, two photodiodes, a beam-dump, and a vacuum can to hold electronics. The base will not be made of marble. Electronics under design (Abbott, Adhikari)
Ben Abbott