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LHO Cosmic Rays in S5
Ray. Frey, U Oregon

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Cosmic ray data for S5 starting 2/06 G060447-00-Z Late start: VME problem identified 8/05; addressed 1/06 Livetime ~70% (relative to calendar time) should be ~95%

Goals · Determine if there is an association between cosmic rays and IFO Direct momentum transfer to TM, or TM modes excitation (heat)
· Calculation says these are negligible, perhaps also for AdL

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Perturbation of the electrostatic charge distribution on TM Initial exploration reported here Veto ­ This is limited: Only one TM is instrumented: H1 ITMY (BSC1) Do not expect this to be an important issue now ­ whether this is true depends on the result of the association study Must consider this for the future.

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a CR event
A B Slow falloff (80 kHz sampling)

Fast rise GPS time stamp (10 ns resolution) C D

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Pulse height distributions

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Considerations for a CR-IFO effect
Momentum transfer (1/ f2 ) and TM mode ring up small ...except for an abnormally energetic and dense shower (~104 muons) Will look for this and characterize effect/limit Electrostatics · Test masses can charge up (eg due to contact to a different material) · Coulomb interactions between TM and environment give rise to displacement noise, as discussed by Rai Weiss (LIGO-T960137 and 2006 elog) Expect excess noise, if any, in 30-100 Hz with 1/f3 spectrum Confirmed by the S5 EQ stop­noise reduction event ?? · Hypothesis: A CR shower can perturb the charge distribution, giving rise to increased displacement fluctuations See also Braginsky, et al, , LIGO-G050457
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First look for a CR-IFO association
First, look at individual CR events · 1-sec spectrum starting at CR time = tcr · 1-sec spectrum at tcr -10
"a typical event"

Plots: Emelie Harstad

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the biggest CR showers (thru 7/26)

UTC time

Shower energy deposition 103 muons

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the biggest CR shower

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the biggest CR shower (contd)

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the biggest CR shower (contd)

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Next...
· · · Studies just getting underway Check all biggest individual events Sum over all CR events, compare on-time vs off-time For a range of time windows Spectra and blrms Determine excess noise (limit) as function of CR signal (# of charges) and time window (i.e. charge re-distribution relaxation time)

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Operations · Recent reliability issues with VME CPU/CDS (the "standard" stuff) LHO will take over operation of the DAQ elements (good!) · The S5 events will be put in the LIGO data base soon (ligo light weight) · LHO considering frames insertion · LLO ?? (Note: ITMY was where CR detector was originally located.)
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the biggest CR shower (contd)

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