Документ взят из кэша поисковой машины. Адрес оригинального документа : http://zebu.uoregon.edu/~uochep/talks/talks06/G060152-00-1.pdf Дата изменения: Tue Aug 1 23:43:00 2006 Дата индексирования: Tue Oct 2 11:51:26 2012 Кодировка: Поисковые слова: light echo

Environmental Disturbances: Early S5 and S4
LIGO -G060152-00-Z

Robert Schofield, U of O Rana Adhikari, CIT, Richard McCarthy, John Worden, LHO

I. II. III. IV. V. VI.

HVAC flow rate reduction improves sensitivity Seismic up-conversion experiments S4 H1-H2 coincident events from site activity PEM injections Electronics rack diagnostic magnetometer Crab protection
1


Gravitational wave sensitivity improves when HVAC off

Blue: All site turbines and chiller pad equipment off; Red: normal

2


Half-normal flow rate about as good as fans off

DARM

Black: off; Blue: Ѕ flow; Red: full flow seismometer

3


Seismic noise likely from fan and plenum, not ducts (at X-end)
Black: off; Red: normal flow; Blue: like red but ducts closed off at plenum

4


Broad-band seismic signal from HVAC possibly produced by plenum turbulence
Pitch of blades controls flow rate through turbine

to duct turbulence

Flow from turbine ~50 mph

5


Summary: HVAC effect on range
·Shutting HVAC down improves H1 & H2 range about ѕ Mpc . ·Influence likely seismic ­ air flow into LVEA/VEA not needed for range reduction. ·Half-flow about as good as HVAC off (seismic level 55% of full flow in 1-50 Hz band). ·For ѕ LVEA flow level, seismic rms is only 61% of full flow level. This provides better temperature control and is what we are currently using. ·Seismic noise possibly from turbulence in supply plenum. ·DARM noise at 100 Hz was likely from up-conversion of lower 6 frequency HVAC seismic signal instead of direct coupling.


Simple back-scattering model doesn't explain tail
Predicted cutoff ~52 Hz

Predicted cutoff ~12 Hz

Tail not proportional to velocity (differs from single frequency injections)

7


Up-conversion not from "squeaky" optic suspension point

shadow sensors (displacement) large test mass displacement produces no upconversion smaller test mass displacement produces up-conversion

DARM

Blue peak is smaller than red in displacement and velocity but not in acceleration .8


Ground or isolation system motion not needed to produce up-conversion Black: ETMY coil injection; Red: ground shaking at ETMY DARM low f

matched ground and coil injections produce similar upconversion DARM high f thick lines: no injection
9


Up-conversion not from RF saturation

uncalibrated DARM (proportional to RF current)

large DARM_EXC injection does not produce upconversion

DARM

10


Up-conversion best predicted by acceleration of optic

DARM: acceleration

peak heights in acceleration plot (but not velocity or displacement) match up-conversion amplitude
DARM: displacement

11


Up-conversion summary
· At low seismic amplitudes, not consistent with backscattering · Not suspension point mechanical up-conversion · Ground or stack motion does not appear to be necessary (is produced by direct ETMY coil injection) · Acceleration of test mass predicts up-conversion better than velocity or displacement. · Not RF saturation · Up-conversion in actuation system? · Magnetic domain-flipping (Barkhausen) noise?
12


What produced coincident H1 H2 bursts during S4?

Accelerometers at time of S4 H1& H2 DARM burst

arrival not consistent

arrival not consistent

Accelerometers during jump in control room

13


Door slams and water bottle drop also not consistent (delay, amplitude, f), but fork lift set-down at shipping is.

Accelerometers at time of S4 H1 & H2 DARM burst

Agreement

Accelerometers during set-down of fork lift forks

14


"Floating" H2 dark port should reduce H1 -H2 coincidences

H1 DARM, H2 DARM during S4 event

H1 DARM, H2 DARM during forklift event: with floating H2 dark port, very little signal is seen on H2
15


S5 PEM Injections
· LLO: Dec 10 2005 elog has burst injection times and transfer functions. Summary: · ACOUSTIC/SEISMIC - coupling lower than S4; no coupling found in electronics bays. · MAGNETIC - coupling about the same as S4; we can not reduce DARM 60 Hz substatially without reducing 60 Hz ambient magnetic field; LVEA pulsed heati ng should be turned off. · RF - external sources loud enough to occasionally show up in DARM - radio channels areimportant veto channels

· LHO: Jan 8 2006 elog has burst injection times, transfer functions. Summary: · ACOUSTIC/SEISMIC-coupling 5x lower than S4; possible backscattering problem from end-station transmitted ports. · SEISMIC UPCONVERSION-same for all H1 and H2 out -stations, would be seen daily in H2 except for mystery noise. · RF- about the same as S4: signal on RADIO_LVEA about 100x SNR of DARM. · MAGNETIC -about the same as S4: a substantial or dominant contributor to DARM 60 Hz, 16 3 Hz sidebands need fixing...


Electronics racks magnetometer diagnostic
Magnetometer near electronics racks previously used to identify peaks in DARM from sources in electronics racks. During S5 break, broad band coherence between magnetometer and DARM led to discovery of bad board (which put ripple on power supply).

cohernce between DARM and magnetometer

before anti -imaging board replacement; after

17


Crab protection

Kyle Ryan improves the seismic isolation of the office area air handler, which has been running recently at 59.6 Hz

18


LVEA HVAC experiments

TOTAL LVEA SEIS_Z BAND (counts) CONFIGURATION FLOW (CFM) 33-50 Hz 1 -27 Hz ________________________________________________________________________________ A) Original fl ow B) 2 LVEA fans and labs at 50% flow C) Full LVEA flow with 2 fans. Labs at 50% D)Full LVEA flow with 3 fans. LABs at 50% E) 75% LVEA flow with 3 fans. LABS at 50% 40,000 20,000 40,000 40,000 30,000 15.7 8.6 12.3 9.2 9.2 52 29 40 37 32

--------------------------------------------------------------------- -----------F) 2 LVEA fans at 75% 2 LAB fans at 50% G) 2 LVEA fans at 50% 2 LAB fans at 75% 30,000 20,000 9.5 9.8 34 35

19