Документ взят из кэша поисковой машины. Адрес оригинального документа : http://zebu.uoregon.edu/~uochep/talks/talks00/schofield_talk.pdf Дата изменения: Wed May 3 22:16:45 2000 Дата индексирования: Tue Oct 2 12:04:58 2012 Кодировка: Поисковые слова: m 5

Some Effects of Earthquakes, Temperature, Wind Stor ms and Barometric Pressure on the Inter ferometer at Hanford

Robert Schofield Masahiro Ito Rauha Rahkola Evan Mauceli Ray Frey David Strom Jim Brau University of Oregon


Some Concerns With Low Frequency Influences

· Loss of lock

· Need for increased servo loop gain

· May eat up actuator range

· Possible increased background in the LIGO frequency band

· Possible modulation of noise in the LIGO band


Guralp Seismometer and Applied Geomechanics Tilt Meter


Optical Lever Pier and Vacuum Chamber for X-arm 2k Input Test Mass
The test mass, 2k ITMX, is 33m away in the BSC just visible in the background.


Calibration Factors, March 14, 2000

Signal
Seismometers Tilt meters Shadow sensors Optical levers on input test masses Optical levers on end test masses Control Signal

Calculation
((1 m/s) / 800 V) * (4 V / 65536 counts) (100 µR/V) * (4 V / 65536 counts) (1x10-3 m / 1.5 V) * (4 V / 65536 counts) (1x10-3 m/ 1.75 V) / 66.6 m (1x10-3 m/ 1.75 V) / 12.2 m

Calibration Factor
0.076 µm/s per count 0.0061 µR per count 0.041 µm per count 17 µR per volt (EPICS channel) 46.8 µR per volt (EPICS channel) 0.00118 µm per count

Error*
17% 16% 40% 40% 40% 4%

direct calibration

* 15% uncertainty range for adc's (variation obtained from a couple of actual calibrations) + maximum variation of instrument calibration (e.g. the most extreme factory calibration for an individual seismometer axis is 816 giving 2% for a total uncertainty of 17%) - Robert


MAX MIN

Optic Motion from October 16, 1999 M7.1 Hector Mine Earthquake (Near Joshua Tree Ca.)
Envelope of optical lever signal: pitch of the Y-arm 2k interferometer corner-station test-mass (damping on)

2

1

Volts

0

-1

-2 99-10-16 08:52:48 3000

99-10-16 09:52:48

99-10-16 10:52:48

99-10-16 11:52:48

99-10-16 12:5

Envelope of seismometer signal: X-arm mid-station Z-axis

2000

Volts * 16,000

1000

0

-1000

-2000

-3000 99-10-16 08:52:48

99-10-16 09:52:48

99-10-16 10:52:48

99-10-16 11:52:48

99-10-16 12:5





Rough Agreement of Tilt Meter, Seismometer and Shadow Sensor
Approximate Amplitude of Motion of the Optic Relative to the Optic Support Structure
Event 1/20/00 Oregon coast quake 1/20/00 Kermadic islands 1/20/00 microseismic peak Peak f 0.1 Hz From Tilt meter* 2.5 µm From Seismometer* 2.6 µm From Shadow sensor 3.2 µm

0.5 Hz 0.16 Hz

0.031 µm 0.15 µm

0.025 µm 0.15 µm

0.020 µm 0.076 µm

* The tilt meter was assumed to measure acceleration; accelerations calculated from the tilt meter and seismometer signals were assumed to be balanced by g sin() (DC approximation); the displacement of the optic from the support structure was calculated from this angle (the length of the pendulum was assumed to be 0.5 m).


Reference Cavity



X-end Davis Weather Station


MAX

Maximum Value by Minute from 99-12-18-0-11-39 to 99-12-18-20-10-39
Wind Speed at Mid-Y : H0:PEM-MY_WIND Pitch of Mid-Y Test Mass: H2:ASC-ETMY_OptLevPitchMon
-4

30

-5

20

uR (approximate)
99-12-18 05:11:23 99-12-18 10:11:08 99-12-18 15:10:53

-6

m/s

-7

10

-8

-9

99-12-18 00:11:38

0

99-12-18 20:10:38 99-12-18 00:14:23

-10

99-12-18 05:14:08

99-12-18 10:13:53

99-12-18 15:13:38

Mid-Y Seismometer, Y-Axis: H0:PEM-MY_SEISY
10 9 8 7 6 5 4 3 2 1 0
99-12-18 00:14:23

Mid-Y Seismometer, Z-Axis: H0:PEM-MY_SEISZ
10 9 8 7 6

um /s
99-12-18 05:14:08 99-12-18 10:13:53 99-12-18 15:13:38

um/s

5 4 3 2 1 0

-1

99-12-18 00:14:23

-1

99-12-18 05:14:08

99-12-18 10:13:53

99-12-18 15:13:38


Anemometer data - fast and slow channels
Slow is offset by a 2.25s integration delay and a 0.8 to 3s variable read out delay 20
18 16

Wind Speed (MPH)

14 12 10 8 6 4 2 0 Slow (EPICS) channel Fast (ADCU) channel (calculated from recorded clicks)

30

40

50

60

70

80

90

Seconds


Pre-Mode Cleaner
Piezo length control is on far side; cavity is open to atmosphere.


MAX MIN

Loss of Pre-Mode Cleaner Lock Due to Changes in Atmospheric Pressure
Voltage on the piezo ring that positions the pre-mode cleaner mirror (range: 0 - 400 V)

400

300

Volts

200

100

0 99-10-22 19:55:12

99-10-23 07:55:12

99-10-23 19:55:12
Atmospheric pressure in the mass storage room

99-10-24 07:55:12

99-10-24 1

100500

Pascals
99500 99-10-22 19:55:12

99-10-23 07:55:12

99-10-23 19:55:12

99-10-24 07:55:12

99-10-24 1


PMC - Piezo Range Needed to Hold Lock For Historical Barometric Pressure Fluctuations at Hanford
Index of refraction changes with barometric pressure cause a strain in optical path length of about 2.7x10-9 per Pascal. The optical path length of the pre-mode cleaner is about 0.4 m. Minimum Piezo Range (µm) 2.7 3.8

Time Span

Maximum Pressure (Pascals) 102,122 103,442

Minimum Pressure (Pascals) 96,806 95,993

1998 - 1999 1955 - 1999

In order to acquire lock at any pressure, an extra free spectral range (0.5 µm) is needed. Also, when lock is acquired, the piezo setting must be coordinated with pressure, or else the range must be further increased. Piezo range > 4.3 µm (a factor of 6.4 over present range of 0.67µm) or air-tight PMC.


Summary

Earthquakes are swinging optics 1 µR or more with some regularity (statistics to be determined). On at least 4 occasions in the last 5 months, motion has been greater than 50 µR. Building temperature fluctuations have shown up in control and optical lever signals. During a 25 m/s wind storm we observed test mass angular motion of up to about 4 µR. Gust meters are needed. The piezo range of the PMC must be increased by a factor of about 6 to maintain lock for pressure fluctuations of historical magnitude. Environmental channels are coming on line and we are beginning to use them to characterize the interferometer.