10-meter Interferometer Results M. Woods (special thanks to Steve Myers and Tim Slaton) Jan. 31, 2000 Commissioning Setup System Noise Monte Carlo simulation Temperature sensitivity Study of frequency sweeping, matching interferometer arm lengths Stability and response with piezo excitation on one end mirror

Optical Anchor Overview Goal: suppress vibrations of final doublet use a closed loop feedback system with - laser interferometer sensor - piezoelectric supports for quad doublet Optical Anchor SchematicInteraction Region Schematic

Interferometer Schematic l 1 = L 1 +  l 1 l 2 = L 2 +  l 2  l =  l 1 -  l 2

In practice, we do the following Measuring the displacement,  l (cont.)

Laser Requirements 1. Laser Power want photon statistics adequate up to 100 Hz N     for T = 0.01s 2. Laser Intensity Stability  I/I <  3. Laser Frequency Stability let (l 1 -l 2 ) < 1cm

Environmental Requirements  air STP 1.1 x He STP 1.3 x n - index of refraction Let  n be change in relative index of refraction for 2 arms  P,  T be changes in relative pressure, temperature for 2 arms  P < 2.7 x Torr (air) 2.3 x Torr (He)  T < 1 x o K (air) 9 x o K (He) (but slow drifts are acceptable)

10-meter Interferometer Test Setup in Sector 10 Alignment Room

Nov. 2, 1999 Runs 5A, 5B, 5AB Photodiode Array Mean Signals Beam A Beam B Beams A and B

Photodiode Signals over 100 seconds Measured Displacement over 100 seconds Nov. 2, 1999 Run 5AB 256 Hz DAQ rms = 0.2nm

Power Spectra for Photodiode Array Signals Nov. 2, 1999 Run 5AB

Integrated Power Spectra for Photodiode Array Signals Nov. 2, 1999 Run 5AB

Displacement Power Spectra and Integrated Power Spectra Nov. 2, 1999 Run 5AB

Run MC001 Photodiode Array Mean Signals Monte Carlo Simulation Beam ABeam B Beams A and B

Input Displacement over 100 secondsReconstructed displacement over 100 seconds Run MC001 10nm ramp over 100 seconds 0.2nm input jitter per point 256 Hz ‘DAQ’

Residual (measured - input) displacement vs input displacement (photodiode spacing correct) Residual displacement vs input displacement with 10% error in photodiode spacing Monte Carlo simulation

Photodiode Signals over 100 seconds Run MC001

Displacement Power Spectra and Integrated Power Spectra Run MC001

Photodiode Signals over 100 seconds Measured Displacement over 100 seconds Nov. 21, 1999 Run 3AB 256 Hz DAQ

Power Spectra for Photodiode Array Signals Nov. 21, 1999 Run 3AB

Displacement Power Spectra and Integrated Power Spectra Nov. 21, 1999 Run 3AB

Photodiode Signals over 15 hours Measured Displacement over 15 hours Nov. 4, 1999 Run 2AB 1 Hz DAQ

Sector 10 Room Temperature over 20 hours Sector 10 Room Temperature over 40 hours Nov. 11, 1999 Temprun1 0.5 Hz DAQ (Avg. 100 pts online) Nov. 2, 1999 Run 1AB 1 Hz DAQ (Avg 100 pts offline)

Studying Temperature Effects on Interferometer Stability 30 seconds into run, put 1 fingertip on one of the 3 beamlines (A,B,C) for 30 seconds. (C is the common beamline before the beamsplitter.) A B C Nov. 11, 1999 Run 2AB Nov. 11, 1999 Run 3AB Nov. 11, 1999 Run 4AB

Studying Frequency Sweeping effects of Laser with and without mismatch in lengths of interferometer arms Nov. 11, 1999 Run 6AB Nov. 11, 1999 Run 10AB No length mismatch 1” length mismatch Prior to these runs, the laser was turned off for 60 seconds and then on for 60 seconds. Then the run is started. This results in laser not being frequency-stabilized during run.

Piezo installed on end mirror for Interferometer Arm B 10 Hz Sine Wave 10 Hz Square Wave Nov. 21, 1999 Run 9AB Nov. 21, 1999 Run 11AB 2560 Hz DAQ for 1-second for these 2 runs

SUMMARY System Resolution/Noise - typically IPS(1Hz) < 0.5nm; this is adequate for initial prototyping and interfacing with quad simulator - have demonstrated adequate resolution/noise for 10-meter arms and with anchoring of optics to floor - these good results are achieved in a good lab setting, ie. Sector 10 Alignment Room -- IPS floor (3Hz) < 10nm, and very good temperature stability (<0.3degC over 24 hours) - for actual IR installation, expect will need vacuum in the interferometer arms (or at least very good thermal isolation) MonteCarlo simulation gives reasonable modeling of results Demonstrated use of laser frequency sweeping to study matching of interferometer arm lengths Demonstrated good sensitivity and low noise with piezo actuator on an end mirror For future:- Tom Mattison is taking over this interferometer operation - it is ready for development of piezo excitation / feedback and for integration with a quad simulator