LIGO-G030423-00-D M. Landry – Hanover LSC Meeting, August 18, 2003

LIGO S2 CalibrationMichael Landry

LIGO Hanford Observatory

Representing the calibration team:Rana Adhikari, Peter Fritschel, Gabriela Gonzalez,

Luca Matone, Brian O’Reilly, Hugh Radkins, Patrick Sutton, Akiteru Takamori

LIGO-G030423-00-D M. Landry – Hanover LSC Meeting, August 18, 2003

Current status

• Online calibration with accuracy of ~20% was available with 1 hour latency

• Interim calibration issued with corrected DC calibration

• Final calibration to include hardware measurements: accurate representation of the actuation function

• Additional Wednesday talks relating to calibration include: Brian O’Reilly, Patrick Sutton, Xavier Siemens, and Soumya Mohanty

LIGO-G030423-00-D M. Landry – Hanover LSC Meeting, August 18, 2003

Calibration Basics I

R(f): Response Function Scale Factor (from Calibration Line)G(f): Open Loop Gain = C(f)D(f)A(f)

Xi / AS_Q(fi,t) = R(fi,t) = [1 + (t) (t) G(fi) ] / (t) C(fi)

Xi = AS_Q(fi,t) . R(fi,t)

LIGO-G030423-00-D M. Landry – Hanover LSC Meeting, August 18, 2003

Calibration Basics II

• We choose a time t0 and measure 0 ,G0 and R0 .

• This allows us to extrapolate to any time t using the amplitude of the calibration line (or lines).

• The amplitude (t) is a function of the alignment, dependent on the carrier power in the arms and the sideband power in the recycling cavity.

• (t) is tracked throughout the science segments.

R(fi,t) = [ 1 + (t) (t) G(fi) ] / (t) C(fi)

LIGO-G030423-00-D M. Landry – Hanover LSC Meeting, August 18, 2003

DC calibrations

• Have redundant measurements, including sign toggling, fringe counting, free-swinging and PZT fine actuator

• Gained confidence with multiple methods during S2; excellent agreement

• Will limit the number of redundant measurements during the S3 run; making some of these beforehand

• Concentrate on reducing error

LIGO-G030423-00-D M. Landry – Hanover LSC Meeting, August 18, 2003

L1 anti-imaging filter

LIGO-G030423-00-D M. Landry – Hanover LSC Meeting, August 18, 2003

New model comparison

LIGO-G030423-00-D M. Landry – Hanover LSC Meeting, August 18, 2003

LHO open loop gains

LIGO-G030423-00-D M. Landry – Hanover LSC Meeting, August 18, 2003

Propagating the calibration:

LLO

LIGO-G030423-00-D M. Landry – Hanover LSC Meeting, August 18, 2003

Propagating the calibration:

LHOH1

LIGO-G030423-00-D M. Landry – Hanover LSC Meeting, August 18, 2003

Contributions to the Error

Magnitude: 2

4

22

4

22

4

2222

1

1

1

1

1

1G

G

G

G

G

G

G

G

G

D

D

A

A

R

R

Phase: 2

4

22222

4

2222

1

1

1

1GDAR

G

GGG

G

G

R(fi,t) = 1 + (t) (t) G(fi)

(t) C(fi)

LIGO-G030423-00-D M. Landry – Hanover LSC Meeting, August 18, 2003

Estimating errors in L1 ’s

LIGO-G030423-00-D M. Landry – Hanover LSC Meeting, August 18, 2003

Violins in H1

Independent check by

Rachel Berkowitz (SURF), and Fred Raab – modelling of violin modes in H1

LIGO-G030423-00-D M. Landry – Hanover LSC Meeting, August 18, 2003

S2 strains

LIGO-G030423-00-D M. Landry – Hanover LSC Meeting, August 18, 2003

LLO epoch comparsion

LIGO-G030423-00-D M. Landry – Hanover LSC Meeting, August 18, 2003

Conclusions

• Necessary to incorporate more realistic filters in model, i.e. measurements instead of as-designed filter

• Final calibration with errors to be issued by next Monday

• Expectations for S3: same 1hr latency for online calibration, with accuracy as per existing (final) calibration – we learn more each time