Caltech: Albert Lazzarini, Peter Shawhan, John Zweizig
     LHO: Mike Landry, Vern Sandberg
     LLO: Brian O'Reilly, Giovanni Santostasi
     Louisiana Tech: Natalia Zotov
     Loyola: Marc Cenac, John Whelan
     Michigan: Keith Riles
     MIT: Erik Katsavounidis
     Oregon: Ray Frey, Robert Schofield
     UWM: Steve Fairhurst, Xavier Siemens

Preparing for June LSC meeting at Tufts

• Although the upcoming 2-day LSC meeting at Tufts is devoted mostly to status of astrophysical analysis, there will be one session late Sunday afternoon on particular detector characterization issues common to all four analysis groups. Tentative topics for that session include calibrations, low-byte corruption,  and PSD estimates. Other suggestions are welcome.

• Calibration:
• Update on S3 calibrations (Mike Landry, Brian O'Reilly)

Mike confirmed that the discrepancy Xavi reported two weeks ago in derived S3 L1 alpha/beta values between the frequency domain and time domain methods is real. The frequency domain numbers were based on a matlab model script which had a typo. The effect requires a modification of the response and sensing functions, and unfortunately, the actual inspiral ranges for L1 are about 30% worse than previously thought. The calibration team is working to understand in detail how the error crept in, without being picked up by the matlab-independent autocalibrator. They expect to have a version 1.2 calibration released in time for the June LSC meeting.
 
• Update on time domain calibration (Xavier Siemens)

Xavi showed the good agreement now obtained between frequency and time domain methods for alpha/beta, with the frequency domain model parameter fixed. There remains a discrepancy in beta at the 5% level, which may (or may not) arise from measurement error at the reference time interval SenseMon uses for its baseline.
 
• Update on hardware injections (Steve Fairhurst)

In trying to understand the large variance seen in effective inspiral distances for hardware-injected inspiral signals, Steve has tried varying alpha for injected chirps in software, applying different amplitudes and frequencies for a sinusoidal variation. He has tested the fidelity of this simple model by looking at not only the induced variance in effective distance, but also the chirp chi**2. He concludes that a 1-second periodicity of a relative variation of 5% agrees qualitatively with what is observed in hardware injections.
 
• Data quality -  Investigations: ( S2 , S3 ) Segment repository (S2 , S3 ) (John Zweizig, Keith Riles)

John gave an updated report on the low-order-byte corruption problem. For floating point channels (like AS_Q!), one nominally expects an effect at the 10**-5 level from corruption of the last 8 bits of the 32-bit word. John has tried simulating the kinds of corruptions (seen unambiguously in otherwise quiet integer channels), in which short clusters of  spikes separated by 16 bytes appear. The bottom line is that the effect on the AS_Q spectrum is indeed at the 10**-5 level. Albert wondered whether check sums could be implemented in the DAQ system to look for byte corruption. Vern mentioned that he has in mind a more demanding test of injecting known patterns into reflective memory (and perhaps further upstream), then checking the DAQ readout. Rolf Bork and Dave Barker are natural candidates to work on this diagnostic, but both are swamped with other work at the moment.


John has also been working on a new PSLMon version with line removal (frequency domain) from the band-limited RMS measurements and has now produced new minute trends for H1 and L1. He sees some improvement (more relative variation) than before, thanks to removal of dominant lines. He plans similar changes (but with time domain notch filters) in the PSLMon glitch finding.
 
• Related study (Albert Lazzarini)

Albert carried out a similar low-order-byte corruption simulation study in which he zeroed out the last 8 bits, 12 bits, 16 bits, etc. of AS_Q data samples (using a matlab script). He too sees an effect no worse than 10**-5 for 8-bit truncation.Studies are ongoing in the stochastic group to understand the effects on the Omega integral. Preliminary findings are a larger effect than naively expected from above, but still safely negligible.
 
• Timing (Szabi Marka, Daniel Sigg)

No update.
 
• Glitches / Burst/Inspiral search group vetoes (Laura Cadonati, Erik Katsavounidis)

Erik reported that the S2 glitch studies are now essentially complete, but that Robert and Masahiro did carry out a recent PEM study motivated by the four low-threshold WaveBurst candidates. The glitch team is now moving on to S3 studies, looking first at triggers stored in the database during online DMT running and focussing on playground data. The team is also paying more attention now to signal detection criteria
.
• Interchannel correlations  (Nelson Christensen)

Nelson couldn't make the telecon, but provided a new table summarizing microphone/AS_Q correlations seen in H1. The table is meant primarily for use by the pulsar group. More tables will be provided soon for H2 and L1, and summaries for other PEM channels, e.g., accelerometers produced.
Albert reminded everyone that the stochastic group has 2-month-long S2 and S3 coherences, where the H1/H2 coherences look much improved after the acoustic mitigation. KR wondered if the stochastic group sees a 0.25 Hz comb in coherence that appears in 2-month-long averages of 30-minute FFT spectral estimates (seen independently by Xavi and Vladimir Dergachev using different PSD programs). Albert wasn't aware of such a comb. KR will report at a future telecon on the effect seen in the PSD's.
 
• Bilinear couplings (Steve Penn)

No update.
 
• Correlated inter-site environmental transients & local environmental disturbances  (Robert Schofield)
  Robert reported that the intersite correlation code has now been run over the entire S3 data set and turned up some 3-sigma excess glitch coincidences between magnetometer and voltage monitor channels at the two sites. Vern wondered if these were seen in October, when solar flares were at an unusally high maximum. Robert will go back and check the times.
  
  Robert also gave an update on several environmental issues he discussed at the April 23 telecon:
• Dust glitches seem important only at the dark port table. Work is underway to quiet down the dust monitors that give magnetic glitches at motor startup (every minute or so). A prototype purged enclosure has also been built for testing.
• The pulsing of heater coils for the ductwork remains a problem. The pulsing not only introduces sidebands on 60 Hz harmonics, but may eventually dominate the 60 Hz line itself. Unfortunately, the schemes looked at so far for reducing the pulsing effects (staged heating of coils, replacement with coils of lower inductance, variac control of coil current, cold water with continuous heating) are all expensive. A decision has not been reached yet on how to proceed, but a low-inductance coil has been ordered for testing.
• Must decide soon whether to build acoustic enclosures around electronics racks in place or wait until after they are moved outside the LVEA.
• The source of dewar glitches is now suspected to be stick-slip of the internal container against bumpers attached to the outer container that are meant to limit excursions during transport. The bumpers are not easily accessible, or they would simply be removed. Right now one dewar has been tilted slightly away from the suspect bumper, but more glitches have been seen since then. Albert wondered if wrapping the dewar in insulation would ameliorate the temperature excursions of the outer container relative to the inner. Robert has looked into that possibility, but it's quite expensive. He mentioned that while large dewar glitches can lead to lock loss, smaller gltiches are a worry too. Nelson has found a small glitch that led to inspiral triggers. Albert also wondered if something like a kinematic mount with built-in "give" could be used to support the dewars instead of the present bolts on concrete. Robert will look into it.

A.O.B.

• Next detchar telecon:  Friday June 11 at 1:30 p.m. EDT  (DMT software)