Photodiode Signals over 100 seconds
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Transcript Photodiode Signals over 100 seconds
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 Schematic
Interaction Region Schematic
Interferometer Schematic
l1 = L1 + dl1
l2 = L2 + dl2
dl = dl1 - dl2
Measuring the displacement, dl
Let S = photodiode signal
dis the equilibrium phase difference
between the two arms
then S N 1 cos
dS N sin 0d
Choose sin
dS
d
S
d
2nm
; d 0.02
For dl = 1nm and = 633nm,
2 633nm
1nm displacement
2% intensity change on photodiode
Measuring the displacement, dl (cont.)
In practice, we do the following
s f cos
tan 1
s fsin
1
disp (633nm)
2
2
Laser Requirements
1. Laser Power want photon statistics adequate up to 100 Hz
2 for T = 0.01s
2
N
>d
d
P
T s
0.02 2.0eV 1.6 10 19 J
P
2
0.01 s
eV
P 10 13W
2. Laser Intensity Stability
3. Laser Frequency Stability
let (l1-l2) < 1cm
DI/I < d
dI
I
0.02
Df
l1 l2 d
2
f
2
Df
10 7
f
Environmental Requirements
n - index of refraction
n 1 a
P(Torr )
T ( K )
airSTP
HeSTP
a
1.1 x 10-4
1.3 x 10-5
Let dn be change in relative index of refraction for 2 arms
dP, dT be changes in relative pressure, temperature for 2 arms
a
aP
dn dP 2 dT
T
2L
T
d
dn
2
dn 10 10
dP < 2.7 x 10-4 Torr (air)
2.3 x 10-3 Torr (He)
dT < 1 x 10-4 oK (air)
9 x 10-4 oK (He)
(but slow drifts are acceptable)
10-meter Interferometer
Test Setup in Sector 10 Alignment Room
Photodiode Array Mean Signals
Beam B
Beam A
Beams A and B
Nov. 2, 1999
Runs 5A, 5B, 5AB
rms = 0.2nm
Measured Displacement over 100 seconds
Photodiode Signals over 100 seconds
Nov. 2, 1999
Run 5AB
256 Hz DAQ
Power Spectra for Photodiode Array Signals
Nov. 2, 1999
Run 5AB
Integrated Power Spectra for Photodiode Array Signals
Nov. 2, 1999
Run 5AB
Nov. 2, 1999
Run 5AB
Displacement Power Spectra and Integrated Power Spectra
Photodiode Array Mean Signals
Monte Carlo Simulation
Beam A
Beam B
Beams A and B
Run MC001
Input Displacement over 100 seconds
Reconstructed 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
Run MC001
Photodiode Signals over 100 seconds
Run MC001
Displacement Power Spectra and Integrated Power Spectra
Measured Displacement over 100 seconds
Photodiode Signals over 100 seconds
Nov. 21, 1999
Run 3AB
256 Hz DAQ
Power Spectra for Photodiode Array Signals
Nov. 21, 1999
Run 3AB
Nov. 21, 1999
Run 3AB
Displacement Power Spectra and Integrated Power Spectra
Measured Displacement over 15 hours
Photodiode Signals over 15 hours
Nov. 4, 1999
Run 2AB
1 Hz DAQ
Nov. 2, 1999
Run 1AB
1 Hz DAQ
(Avg 100 pts offline)
Sector 10 Room Temperature over 20 hours
Nov. 11, 1999
Temprun1
0.5 Hz DAQ
(Avg. 100 pts online)
Sector 10 Room Temperature over 40 hours
Studying Temperature Effects on Interferometer Stability
B
A
Nov. 11, 1999
Run 2AB
Nov. 11, 1999
Run 3AB
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.)
C
Nov. 11, 1999
Run 4AB
Studying Frequency Sweeping effects of Laser
with and without mismatch in lengths of interferometer arms
1” length mismatch
No length mismatch
Nov. 11, 1999
Run 6AB
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.
Nov. 11, 1999
Run 10AB
Piezo installed on end mirror for Interferometer Arm B
10 Hz Sine Wave
2560 Hz DAQ for 1-second
for these 2 runs
Nov. 21, 1999
Run 9AB
10 Hz Square Wave
Nov. 21, 1999
Run 11AB
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
-- IPSfloor(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