1. ALLEGRO calibration for the LLO-ALLEGRO stochastic analysis
Martin McHugh
Loyola University New Orleans
Stochastic sub-group: S. Bose, S. Heng, W. Johnson, J. Romano, T. Regimbau, J. Whelan, P. Zhang
LIGO-G Z
LSC meeting, LIGO Livingston Observatory 18 March, 2004

2. LLO - ALLEGRO correlation
Good overlap (40 km separation) – sensitive to higher frequency range than LLO-LHO
Modulate – rotate to align/misalign/anti-align antenna patterns
Another independent detector
40 km apart, explore PEM correlations at intermediate distances
LIGO-G Z
LSC meeting, LIGO Livingston Observatory 18 March, 2004

3. LSC meeting, LIGO Livingston Observatory 18 March, 2004
Outline of technique
correlate A1 with L1, equal time stretches
Sampling rate very different (250Hz for A1, 2048Hz for L1)
A1 data is heterodyned – 250Hz band around ~900Hz
match bins in frequency domain
resonant nature of the detector means long time constant for excitations in the raw data. Easier to calibrate all of the data and then work with h(t)
Store in frames, coordinate with other groups doing h(t) frames
LIGO-G Z
LSC meeting, LIGO Livingston Observatory 18 March, 2004

4. LSC meeting, LIGO Livingston Observatory 18 March, 2004
LIGO-G Z
LSC meeting, LIGO Livingston Observatory 18 March, 2004

5. LSC meeting, LIGO Livingston Observatory 18 March, 2004
Signal path
LIGO-G Z
LSC meeting, LIGO Livingston Observatory 18 March, 2004

6. LSC meeting, LIGO Livingston Observatory 18 March, 2004xI
Bar response
R(f) x
z[i]
Heterodyne
and
Low-pass F(f)
DAQ xQ
Feedback
damping
H(f)
LIGO-G Z
LSC meeting, LIGO Livingston Observatory 18 March, 2004

7. LSC meeting, LIGO Livingston Observatory 18 March, 2004
Calibration
determine T[k] F[k]
Simple model for bar response (R)
track mechanical mode frequencies
track mode Q’s (accounts for feedback – (H))
determine overall gain (counts/strain), T and F combined
need to get phase shifts not included in mechanical response model (electronic -- F)
also need phase of heterodyne reference with respect to overall time standard (gps)
Tests indicate we can stitch together strain time series with overlapping stretches
LIGO-G Z
LSC meeting, LIGO Livingston Observatory 18 March, 2004

8. LSC meeting, LIGO Livingston Observatory 18 March, 2004
Calibration line
Detector resonances
Extra mechanical resonances
LIGO-G Z
LSC meeting, LIGO Livingston Observatory 18 March, 2004

9. transducer current changed temperature fluctuations
LIGO-G Z
LSC meeting, LIGO Livingston Observatory 18 March, 2004

10. LSC meeting, LIGO Livingston Observatory 18 March, 2004
Calibration line
Extra mechanical resonances
LIGO-G Z
LSC meeting, LIGO Livingston Observatory 18 March, 2004

11. LSC meeting, LIGO Livingston Observatory 18 March, 2004
Calibration pulses in raw and strain time series
calibration line off
calibration line on
calibration pulses
LIGO-G Z
LSC meeting, LIGO Livingston Observatory 18 March, 2004

12. LSC meeting, LIGO Livingston Observatory 18 March, 2004
LIGO-G Z
LSC meeting, LIGO Livingston Observatory 18 March, 2004

13. LSC meeting, LIGO Livingston Observatory 18 March, 2004
Is this calibration good enough?
ALLEGRO currently running – same mechanical system as S2, mostly same electronics
Allows us to perform some tests to verify model, measure phase shifts
Have begun with noise injection measurement done by LSU group
LIGO-G Z
LSC meeting, LIGO Livingston Observatory 18 March, 2004

14. LSC meeting, LIGO Livingston Observatory 18 March, 2004
LIGO-G Z
LSC meeting, LIGO Livingston Observatory 18 March, 2004

15. LSC meeting, LIGO Livingston Observatory 18 March, 2004
LIGO-G Z
LSC meeting, LIGO Livingston Observatory 18 March, 2004

16. LSC meeting, LIGO Livingston Observatory 18 March, 2004
LIGO-G Z
LSC meeting, LIGO Livingston Observatory 18 March, 2004