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Report to the 40m Technical Advisory Committee cit40m/Docs/40m_TAC_051013.pdf · PDF file 2005-10-13 · Report to the 40m Technical Advisory Committee October 13, 2005 The 40m Team

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  • 40m TAC, 10/13/05 1

    Report to the 40m Technical Advisory Committee

    October 13, 2005

    The 40m Team Ben 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

    Dark port

    Bright port

    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 m

    f2

    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

    1-2.3E-24.6E-12.7E-33.6E-3f1 × f2PO

    7.1E-217.5E-11.5E-3-6.2E-4f1 × f2AP

    -1.0E-1-3.2E-21-3.0E-4-1.7E-3f1 × f2SP

    -1.7E-81.3E-31.2E-81-4.8E-9f2AP

    -2.3E-6-1.3E-6-1.2E-3-3.8E-91f1SP

    l sl−l+L−L+Dem. Freq.

    Port

    Signal Extraction Matrix (in-lock)

    Common of arms Differential of arms Power recycling cavity

    Michelson Signal recycling cavity

    Laser

    ETMy

    ETMx

    ITMy

    ITMxBS

    PRM

    SRM

    SP AP

    PO

    lx

    ly

    lsx

    lsy

    Lx =38.55m Finesse=1235

    Ly=38.55m Finesse=1235

    Phase Modulation f1=33MHz f2=166MHz

    T =7%

    T =7%

    GPR=14.5

  • 40m TAC, 10/13/05 6

    Differences between AdvLIGO 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 2004 §§DRMI locked with carrier resonance (like GEO configuration)DRMI locked with carrier resonance (like GEO configuration) November 2004November 2004 §§DRMI locked with sideband resonance (Carrier is anti resonant prDRMI locked with sideband resonance (Carrier is anti resonant preparing for RSE.)eparing for RSE.)

    Carrier

    33MHz

    Unbalanced 166MHz

    Belongs to next carrier

    Belongs to next carrier

    Carrier 33MHz 166MHz

    ITMy

    ITMx BS

    PRM

    SRM

    OSA DDM PD

    DDM PD

    DDM PD

    Typical lock acquisition time : ~10sec Longest lock : 2.5hour

  • 40m TAC, 10/13/05 8

    Lock acquisition procedure towards detuned RSE

    ITMy

    ITMxBSPRM

    SRM

    ETMx

    ETMy

    Shutter

    Shutter

    Carrier 33MHz 166MHz

    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 arm control signal

    RSE

    Done In progressDone

  • 40m TAC, 10/13/05 9

    All 5 degrees of freedom under controlled with 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 control LL-- : AP166 with no offset: AP166 with no offset LL+ : + : Trx+TryTrx+Try with DC offsetwith DC offset

    Yarm lock Xarm lock

    Arm power

    Error signal

    Ideal lock point

    Offset lock Offset lock

    Have started trying to reduce 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

    P ha

    se [d

    eg ]

    10 2 3 4 5 6 7 8

    100 2 3 4 5 6 7 8

    1000 2 3 4 5 6

    Frequency[Hz]

    50

    40

    30

    20

    10

    0

    -10

    -20

    M ag

    [d B

    ]

    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 RSE peak ~ 4kHz

  • 40m TAC, 10/13/05 12

    Lock acquisition procedure towards detuned RSE

    Start with no DOFs controlled, all optics aligned. Re-align each 1.5 hours.

    ITMy

    ITMx BS

    PRM

    SRM SP DDM

    13m MC

    33MHz

    166MHz

    SP33 SP166

    AP DDM

    AP166

    PO DDM

  • 40m TAC, 10/13/05 13

    Lock acquisition procedure towards detuned RSE

    DRMI + 2arms with offset

    ITMy

    ITMx BS

    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%I Q

    1/sqrt(TrY)

    1/sqrt(TrX)

  • 40m TAC, 10/13/05 14

    Lock acquisition procedure towards detuned RSE

    Scripto-matic:

    ITMy

    ITMx BS

    PRM

    SRM SP DDM

    13m MC

    33MHz

    166MHz

    SP33 SP166

    AP DDM

    AP166 To DARM

    PO DDM

    AP166 / (TrX+TrY)

    CARM

    DARM +

    -1 +

    Short DOFs -> DDM DARM -> RF signal CARM -> 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

    ITMx BS

    PRM

    SRM SP DDM

    13m MC

    33MHz

    166MHz

    SP33

    SP166

    AP DDM

    AP166 To 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

    § Sig

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