1  of  14  

Status  of  Advanced  LIGO  

Denis  Martynov  

August  22,  2015  

2  of  14  

Overview:  

•  GravitaAonal  waves  astronomy  

•  OpAcal  layout  and  control  

•  SensiAvity  analysis  

•  Current  R&D  projects  

3  of  14  

GravitaAonal  waves  

In  the  weak  field  regime  

 

we  get  wave  equaAon  

 

and  soluAon          

Astrophysics  sources  

– Binary  neutron  stars  

– Binary  black  holes  

– BH+NS  pairs  – Pulsars  

– Bursts  – StochasAc  background  

gij =ηij + hij

(∇2 −1c2

∂2

∂t2)hij = 0

hij =

0 0 0 00 −h+ h× 00 h× h+ 00 0 0 0

#

$

%%%%%

&

'

(((((

cos(ωt − kz)

4  of  14  

GravitaAonal  waves  detectors  

Ground  based  opAcal  interferometers:  •  LIGO  Livingston  •  LIGO  Hanford  •  GEO  •  VIRGO  •  KAGRA  •  LIGO  India  •  Einstein  telescope  •  LUNGO  

Other  techniques:  •  Resonant  bars  •  Torsion-­‐bar  antennas  •  Atom  interferometers  •  LISA  •  DECIGO  

5  of  14  

OpAcal  configuraAon  

6  of  14  

Parameters  of  control  system  •  Instrument  has  5  coupled  

longitudinal  and  20  angular  degrees  of  freedom    

•  Linewidths  are  small  

•  Ground  moves  with  velocity  of  0.5-­‐2um/sec  

•  RMS  of  opAc  angular  velocity  is  100nrad/sec  

•  Actuators  are  weak  to  meet  noise  requirements  

DARM   200pm  

CARM   7pm  

PRCL   1nm  

MICH   10nm  

SRCL   40nm  

Length offset, um-0.25 -0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2 0.25

Sign

al, a

rb

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1IQ

7  of  14  

Lock  losses  •  Parametric  instabiliAes  

•  Earthquakes  •  Glitches  in  controls  system  

8  of  14  

Noises  

•  Fundamental  noises  

•  Charging  noise  

•  ActuaAon  and  sensing  

•  Intensity  and  ji`er  •  Auxiliary  loops  

•  Residual  gas  

9  of  14  Frequency, Hz

101 102 103

Dis

plac

emen

t, m

/Hz1/

2

10-22

10-21

10-20

10-19

10-18

10-17

10-16 DARM 25WSeismic noiseBosem noiseLaser amplitude noiseSuspension thermal noiseCoating brownian noiseDark noiseQuantum noiseLength couplingAngular controlsPUM actuator noiseESD noiseInput jitter noiseOscillator noiseSqueeze film dampingX-end potential noiseGas phase noiseSum of noises

Total  noise  budget  

10  of  14  

Sca`ering  modulates  sensiAvity  Sca`ered  light  noise  is  non-­‐staAonary.  Coupling  is  modulated  by  alignment  dric  of  uncontrolled  degrees  of  freedom  on  Ame  scale  of  1-­‐2  hours  

11  of  14  

List  of  R&D  projects  (not  complete)  

•  Cryogenic  interferometer    •  Interferometer  with  long  arms  (40km)  

•  Space  mission  (try  to  make  it  cheap)  

•  Robust  control  system  

•  Filter  cavity  for  the  squeezer  

•  OpAmizaAon  of  opAcal  configuraAon  

12  of  14  

Constraining  EoS  of  neutron  stars  

A.  Bauswein  and  H.-­‐T.  Janka.  Measuring  Neutron-­‐Star  ProperAes  via  GravitaAonal  Waves  from  Neutron-­‐Star  Mergers.  PRL,  6  JAN  2012  

13  of  14  

OpAmizing  signal  recycling  cavity  

SRMSR3

SR2

SR2_BSR2_C

PD_A PD_BFROMIFO

•  Replace  some  of  the  passive  mirrors  with  acAve  caviAes  •  Tune  round-­‐trip  phase  of  the  caviAes  to  opAmize  response  in  the  

parAcular  frequency  band  

Frequency, Hz101 102 103 10410-21

10-20

10-19

10-18

10-17

aLIGO design, SRM T=0.36Compound SR2, no detuningDetuned SR2, big massDetuned SR2, small mass

14  of  14  

Conclusions  

•  Lock  acquisiAon  algorithm  is  robust  

•  Parametric  instabiliAes  cause  most  of  lock  losses  

•  Advanced  LIGO  will  start  its  first  observaAonal  run  in  September  2015  

•  Current  sensiAvity  is  factor  of  3  higher  compared  to  iniAal  LIGO  

•  R&D  projects  towards  LIGO  III  are  ongoing  

15  of  14  

AddiAonal  slides  

16  of  14  

SensiAvity  using  different  topologies  

10−1 100 101 102 103 10410−21

10−20

10−19

10−18

10−17

10−16

10−15

10−14

Frequency, Hz

Qua

ntum

noi

se, m

/Hz1/

2

Simple MIPower recycled MIDual recycled MIaLIGO design

17  of  14  

OpAcal  detecAon  schemes  

•  Longitudinal  sensing  – Homodyne  readout  – Heterodyne  readout  – Auxiliary  lasers    

•  Angular  sensing  – Quadruple  photodetectors  – Wave  front  sensors  

18  of  14  

Homodyne  vs  heterodyne  readout  

Phase, pi-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

Sign

al, a

rb

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

PD_A + PD_B, no reference fieldPD_A - PD_B, phase shift = 0.3radPD_A - PD_B, phase shift = 1rad

Length offset, um-0.25 -0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2 0.25

Sign

al, a

rb

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1IQ

19  of  14  

Auxiliary  laser  •  Auxiliary  laser  is  locked  to  the  cavity,  and  frequency  of  transmission  

beam  is  determined  by  the  cavity  eigen  mode  •  IR  light  is  picked  off  from  the  main  laser  and  doubled  in  frequency  •  Difference  between  frequencies  of  the  main  laser  light  and  cavity  

eigen  mode  is  derived  from  the  beat  signal  

Frequency  of  auxiliary  laser  is  doubled  to  tune  cavity  finesse  and  transmission  of  readout  opAcs  for  the  main  and  auxiliary  laser  beams  

20  of  14  

Alignment  of  opAcal  caviAes  

IX EXcavity axis

central axisinput beam axis

Goals:  •  Input  beam  should  be  coaligned  with  the  cavity  axis  to  maximize  power  build  up  

•  Cavity  axis  goes  through  opAcs  center  to  reduce  geometrical  losses  

21  of  14  

Angular  sensors  

ITM ETM

DC  sensing:  QPDs  set  in  transmission  or  pick  off  port.  Signal  is  derived  from  the  beat  between  TEM00  and  TEM01  carrier  modes    RF  sensing:  WFS  set  in  reflecAon  of  the  cavity.  Signal  is  derived  from  the  beat  between  TEM00  sideband  and  TEM01  carrier  mode  

22  of  14  

RelaAve  arm  alignment  •  Residual  misalignment  lec  acer  funning  iniAal  alignment  procedure  •  Control  to  ETMs  misaligns  arm  caviAes  •  RadiaAon  pressure  applies  torque  on  the  test  masses    

−140 −120 −100 −80 −60 −40 −20 0−1

−0.8

−0.6

−0.4

−0.2

0

0.2

0.4

0.6

0.8

1 x 104

CARM offset, pm

Res

pons

e, W

atts

/ ra

d

AS A PITCHAS B PITCHAS A YAWAS B YAW

AS WFS B TO A TRANSITION POINT

23  of  14  

Noise  couplings  

24  of  14  Frequency, Hz

101 102 103

Dis

plac

emen

t, m

/Hz1/

2

10-21

10-20

10-19

10-18

10-17

10-16

DARM 25WSeismic noiseGravity gradientsSuspension thermalCoating Brownian noiseThermo-optic noiseSubstrate Brownian noiseQuantum noiseSum of noises

Fundamental  noises  

25  of  14  

Noises:  charge  on  test  masses  

TEST  MASS  

   

   

RING  HEATER  

ESD  BLADES  

METAL  

20nV/Hz1/2  

1uV/Hz1/2  

•  Surface  charge  of  1nC  was  measured  on  ETM  surfaces  •  Front  surface  was  discharged  by  introducing  ions  into  the  chamber  

•  Back  surface  can  be  discharged  only  if  chamber  is  open  •  Voltage  fluctuaAons  on  surrounding  metal  couple  to  DARM  

26  of  14  Frequency, Hz101 102 103

Dis

plac

emen

t, m

/Hz1/

2

10-21

10-20

10-19

10-18

10-17

10-16

10-15

Measured noiseETMY potentialGwinc noises

Noises:  ETMY  potenAal  

27  of  14  Frequency, Hz

101 102 103

Dis

plac

emen

t, m

/Hz1/

2

10-21

10-20

10-19

10-18

10-17

10-16

10-15

Measured noiseDark noiseESDQuad L2 High RangeQuad L2 Low NoiseBS M2 High RangeBS M2 Low NoiseGwinc noises

Sensing  and  actuaAon  

28  of  14  Frequency, Hz101 102 103

Dis

plac

emen

t, m

/Hz1/

2

10-21

10-20

10-19

10-18

10-17

10-16

10-15

Measured noiseOld PMCLaser amplitudeInput jitterOscillator amplitudeGwinc noises

Noises:  intensity  and  ji`er  

29  of  14  

Noises:  Auxiliary  loops  •  MICH  –  coupling  on  the  sensing  side  

•  SRCL  –  coupling  through  radiaAon  pressure  

•  CARM  –  coupling  through  arm  imbalances  and  losses  

•  Angular  moAon  –  coupling  through  beam  decentering  and  interferometer  misalignments  and  coil  imbalances  

30  of  14  Frequency, Hz101 102 103

Dis

plac

emen

t, m

/Hz1/

2

10-17

10-16

10-15

10-14

10-13

10-12

MICHPRCLSRCL

Noises  of  auxiliary  loops  

31  of  14  Frequency, Hz101 102 103

Dis

plac

emen

t, m

/Hz1/

2

10-21

10-20

10-19

10-18

10-17

10-16

10-15

Measured noiseMICH couplingPRCL couplingSRCL couplingFrequency noiseAngular controlsOscillator phase noiseGwinc noises

Noises:  auxiliary  loops  

32  of  14  Frequency, Hz

101 102 103

Dis

plac

emen

t, m

/Hz1/

2

10-21

10-20

10-19

10-18

10-17

10-16

10-15

DARM 25WSqueezed dampingPhase noiseFundamental noises

Residual  gas  

33  of  14  

Non-­‐staAonary  noises  and  lines  

•  Narrowband  lines  

•  Parametric  instabiliAes  

•  Glitches  

•  Sca`ering  

34  of  14  

Lines  

•   30Hz  comes  from  HVAC  at  Y-­‐end  staAon  •   60Hz,  180Hz  lines  come  from  potenAal  fluctuaAon  at  end  staAons  

•  120Hz,  240Hz  come  from  amplitude  noise  of  Marconi  RF  generator  

•  300Hz  comb  likely  comes  from  violin  modes  of  triple  suspensions  and  PSL  beam  ji`er  

•  500Hz  comb  and  harmonics  are  violin  modes  of  test  mass  suspensions  

•  845Hz  line  is  downconversion  from  parametric  instability;  true  mode  frequency  is  15.5kHz  

•  1600Hz  comb  comes  from  OMC  dither  alignment  

35  of  14  

Parametric  instability  

36  of  14  

Glitches:  DAC  zero  crossings,  IPC  errors,  RF  crosstalk  

Time (s)0 0.5 1 1.5 2 2.5 3

Sign

al

-4

-2

0

2

4

6

Time series

T0=05/08/2014 07:57:20.300048 Avg=1/Bin=4

L1:LSC-PRCL_IN1

Time series

Time (s)0 0.5 1 1.5 2 2.5 3

Sign

al

-1000

-500

0

500

1000

Time series

T0=05/08/2014 07:57:20.300048 Avg=1/Bin=4

L1:SUS-PRM_M3_COILOUTF_UL_OUT

Time series

37  of  14  

•  Interferometer  input  

•  Arm  caviAes  

•  Chamber  walls  

•  OMC  backsca`ering  

Sources  of  sca`ered  light  noise  

38  of  14  

•  Sca`ered  noise  coupling  to  DARM  through  phase  modulaAon  and  radiaAon  pressure  (T1300354):  

Sources:  arm  caviAes  

DARM ( f ) ~ λ 2 +Const( P0Mf 2

)2Aripple2 Ltube( f )

14.38Hz   45Hz   90Hz  Measured  noise  at  10W,  m/Hz1/2   <1.3e-­‐20   <5.8e-­‐22   1.8e-­‐22  Current  sensiAvity  at  25W,  m/Hz1/2   1.5e-­‐18   7e-­‐20   5e-­‐20  

Designed  sensiAvity  at  125W,  m/Hz1/2   2.5e-­‐19   2.7e-­‐20   1.4e-­‐20  

•  Measurement  at  LLO  

39  of  14  

Sources:  OMC  backsca`ering  

Sources  of  low  frequency  moAon:  •  HAM5-­‐HAM6  

relaAve  •  SRM  control  to  

stabilize  SRC  length  •  Output  ji`er   Frequency, Hz

101 102

DAR

M, m

/Hz1/

2

10-20

10-19

10-18

10-17

10-16

10-15

10-14

BackgroundHAM5 FF OFF

Fringe  wrapping  is  seen  during  winter  Ame  when  seismic  noise    is  high.  Field  reflecAvity  measured  in  full  lock  is  r  =  10-­‐4  (LLO)  and  depends  on  beam  posiAon  on  OFI,  r=10-­‐5  (LHO)  

40  of  14  

MiAgaAon:  feedforward  cancellaAon  

EAS = EDC +Esc = EDC + kEDCe4πiL/λ

L = Llf +Lhf ;Llf ~ λ;Lhf << λ

e4πiL/λ ≈ e4πiLlf /λ (1+ 4πiLhf / λ)

Consider  sca`ering  path    at  the  output  port:  

Frequency (Hz)10 210 310

)1/

2A

mpl

itude

(m/H

z

-1410

-1310

-1210

-1110

-1010

Power spectrum

T0=17/02/2015 00:00:29 Avg=412 BW=1.49999

L1:PEM-CS_ACC_HAM6_OMC_XL1:PEM-CS_ACC_ISCT6_OMC_X

Power spectrum

Frequency (Hz)10 210 310

Coh

eren

ce

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Coherence between 2 accelerometers

*T0=16/02/2015 23:52:01 Avg=412 BW=1.49999

10cm

40cm

100cm

Coherence between 2 accelerometersLow  frequency  moAon  can  not  be  neglected.  Feedforward  scheme  should  use  blended  seismometer  and  accelerometer  signals.  

41  of  14  

MiAgaAon:  feedforward  cancellaAon  

Frequency (Hz)

-210 -110 1 10 210

)1

/2A

mp

litu

de (

m/H

z

-1410

-1310

-1210

-1110

-1010

-910

-810

-710

-610

-510

Power spectrum

T0=17/02/2015 05:42:35 Avg=11/Bin=11L BW=0.0117178

L1:ISI-BS_ST1_GNDSTSINF_B_X_IN1

L1:ISI-BS_ST1_GNDSTSINF_B_X_IN1(RMS)

L1:ISI-BS_ST1_GNDSTSINF_B_Z_IN1

L1:ISI-BS_ST1_GNDSTSINF_B_Z_IN1(RMS)

Power spectrum