1 / 9

Virgo ‘timing’ calibration

This document outlines the timing calibration performed during the VSR1 phase of the Virgo project, focusing on the dark fringe analysis and system errors identified. Key components include absolute timing measurement of the dark fringe, actuation timing chains, and the influence of high, low, and mid-frequency signals. The report details necessary corrections for systematic errors, including delays and phase discrepancies observed in different frequency ranges. Calibration methods, including DAQ timing and sensing adjustments, are discussed to enhance detector performance and accuracy.

maire
Télécharger la présentation

Virgo ‘timing’ calibration

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Virgo ‘timing’ calibration Loïc Rolland Note: Timing calibration during VSR1 in the Virgo codifier (VIR-028A-08, link) LSC-Virgo, Orsay- June 11th 2008

  2. Dark fringe (Pr_B1_ACp) (Cavity pole)-1 Timing calibration componants Absolute timing of the dark fringe (for multi-detector analysis) Hrec principle synoptic Delay from actuation to dark fringe Coil Pendulum + NE, WE, BS, PR zCorr Also used for the global TF measurements Coil current ΔL • Needs of timing calibration: • High frequency (> 100’s Hz): absolute DAQ timing and dark fringe sensing • Low frequency (<100’s Hz): actuation chain delay • Mid-frequency: combination of all effects LSC-Virgo, Orsay- June 11th 2008

  3. High frequency timing measurements High frequency timing • DAQ timing • Monitored during VSR1: 21 µs delay from DAQ • Systematic errors estimated in February 2008 • Effect corrected in h(t) ± 2 µs error on the DAQ delay • Dark fringe sensing • Photodiode readout electronics measured in October 2007 • Compensation of the compression and anti-alias filters • Effect corrected in h(t) • ± 30 mrad systematic errors (fit residuals) • ± 3 µs error on the sensing delay (different delays of both photodiodes) 30 mrad Pr_B1_d2_ACp Pr_B1_d3_ACp LSC-Virgo, Orsay- June 11th 2008

  4. High frequency phase systematics High frequency timing Residuals from DAQ and dark fringe sensing: ±30mrad and ±5 µs delay LSC-Virgo, Orsay- June 11th 2008

  5. Low frequency timing Delay from correction signals to ITF output NE, WE, BS z-corrections (zCorr) Main stream calibration based on data in free swinging Michelson configurations (< 1 kHz)  Understand the measured delays from zCorr to Pr_B1p DSP DAC zCorr  force • The measured delays include some filters: • actuation DAC anti-image filter • sensing ADC anti-alias filter • They are equivalent to pure delay below 1 kHz Coil driver Coil current Force applied on the mirror Mirror deformation Pendulum Optical response Dark fringe sensing ITF output channel (Pr_B1p) ΔL LSC-Virgo, Orsay- June 11th 2008

  6. Low frequency timing Actuation timing systematics: measurements NE, WE, BS z-corrections (zCorr) (delays in µs) DSP DAC zCorr  force Coil driver Coil current From calibration main stream Force applied on the mirror • Difference between overall expectations and measurements: • 7 µs for NE, WE • 34 µs for BS (20 mrad at 100 Hz) Mirror deformation Pendulum Optical response Dark fringe sensing ITF output channel (Pr_B1p) ΔL LSC-Virgo, Orsay- June 11th 2008

  7. Combination of actuation errors: phase systematics Low frequency timing Injection of lines on the NI mirror (non-controlled mirror): comparison of the phase of h(t)/injection to the actuation model phase (rad)  ± 100 mrad systematic errors PRELIMINARY LSC-Virgo, Orsay- June 11th 2008

  8. Phase systematic uncertainties vs frequency • ABSOLUTE TIMING SYSTEMATICS • DAQ timing: 2 µs delay • Dark fringe sensing model: 30 mrad + 3 µs delay • COMBINATION OF SIGNALS • NE, WE and BS actuation: <35 µs delay • NI model vs reconstructed phase: <100 mrad • Constant phase systematic: less than 100 mrad (conservative estimate)  Constant phase error (<100 mrad) up to a few kHz • 5 µs delay at high frequency PRELIMINARY LSC-Virgo, Orsay- June 11th 2008

  9. Pcal checks: timing and sign of hrec V2 h(t) ΔL(t) • Photon calibration injection advantages: • known side of the mirror • laser power always positive (known sign of injections)  Absolute sign of injections • Use of photon calibration: TF • corrected for: • absolute delay of the photodiode readout channel (not precisely calibrated) • pendulum mechanical response h(t) Phododiode_readout(t) • Fit of the phase: • 0 = 0 ± 0.01 rad • the sign of h(t) is correct • delay = 36 ± 4 µs • the timing of h(t) above 200 Hz is not completely off Phase (rad) PRELIMINARY Freq (Hz) LSC-Virgo, Orsay- June 11th 2008

More Related