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MIF (Noise Budget)
kentaro.komori - 16:51 Friday 06 December 2024 (31921) Print this report
Update of kagrapygwinc

Abstract:
I updated kagrapygwinc, enabling it to provide results that better align with on-site sensitivity measurements by incorporating more realistic models and inputs.

Detail:
The previous versions of kagrapygwinc and MATLAB code for calculating KAGRA's design sensitivity had limitations in reflecting on-site measurements accurately.
For instance, they did not account for the thermoelastic noise of the sapphire fibers, which is one of the dominant fundamental noise sources at 250 K.
Additionally, pitch thermal noise, another potential dominant noise source, was not included in the calculations.
To address these issues, I performed the following updates to kagrapygwinc:

  • Quantum Noise (precomp.py, quantum.py, KAGRA_O4b.yaml):
    Previously, users needed to specify the power before the beam splitter (BS), but now the code accepts inputs of the interferometer's input power and power recycling gain (PRG), which are directly measured and displayed in the control room.
    The quantum noise is calculated based on the inputs of ifo.Laser.Power and ifo.Laser.PRG in the YAML file.
    Additionally, users can input measured finesse and optical loss parameters to accurately estimate shot noise.

  • Thermal Noise (substratethermal.py, suspensionthermal.py):
    Michimura-san's code (as reported in klog:31720) has been integrated to calculate thermoelastic noise in substrates and suspensions at arbitrary temperatures.
    I also added functionality to compute pitch and vertical suspension thermal noises using a double-pendulum model, with inputs for resonant frequencies and Q-values of the blade springs and CuBe fibers (ifo.Suspension.BladeSpring.fp, ifo.Suspension.BladeSpring.fv, ifo.Suspension.CuBe.fp, and ifo.Suspension.CuBe.fv).
    These calculations now reflect the measured resonant frequencies, which differ from those assumed in the original design sensitivity, as the IM and TM are suspended from the MN instead of a fixed point.

  • Technical Noise (technical.py):
    A new feature allows users to plot technical noise as a force noise acting on the TM, based on the input for ifo.Technical.get.Noise100, which corresponds to the displacement sensitivity at 100 Hz.
    Users can now incorporate arbitrary force noise into the total noise budget for more comprehensive analysis.

Future Work:
Once this updated code is integrated into pastavi, users will be able to check the fundamental noise contributions in real-time using noise budgets generated based on parameters such as input power, PRG, and suspension Q-values.
Adding a dedicated section in pastavi to output the fundamental noise based on user-defined inputs would make it even more convenient and insightful for on-site operations and sensitivity analysis.

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