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Reports until 15:41, Thursday 29 October 2015
H1 SUS (SUS)
borja.sorazu@LIGO.ORG - posted 15:41, Thursday 29 October 2015 - last comment - 17:15, Thursday 29 October 2015(22959)
Violin mode injections at the 3rd harmonics

(Evan Hall, Borja Sorazu)

This is  a preliminary entry on the identification of 3rd violin mode harmonics with test masses (figures and further analysis will be entered later on). This information will be used to estimate mechanical losses.

Dates and times of injections: 2015-10-28 from 20:42:30 to 20:45:00 --> Injection on ITMX

                                                     2015-10-29 from 20:20:00 to 20:32:00 --> Injection on ITMY

                                                     2015-10-29 from 20:37:30 to 20:45:00 --> Injection on ETMX

                                                     2015-10-29 from 20:53:00 to 21:00:00 --> Injection on ETMY

 

Injection description: Fed back, in phase, DARM to penultimate mass coil drivers in pitch after bandpassing it between 1450 to 1500Hz.

Frequency modes identification (preliminary):

ITMX:

     1463.09Hz, increased by factor 4

     1467.96Hz, increased by factor 4

     1462.31Hz, decreased by factor 1.3

ITMY:

     1461.41Hz, increased by factor 4.6

     1462.03Hz, decreased by factor 4

    1463.09Hz, increased slightly

    1470.38Hz, decreased slightly

    1470. 83Hz, increased by factor 2

    1472.5Hz, decreased by factor 9

ETMX:

     1463.09Hz, decreased slightly by factor 1.077

     1471.93Hz, increased by factor 6.6

    1474.08Hz, increased by factor 4

    1475.25Hz, increased by factor 9

    1478. 17Hz, increased by factor 4

ETMY:

     1482.6Hz, increased by factor 1.75

     1484.67Hz, increased by factor of PI

 

Future measurement: We will do a similar injection with DARM fedback 90 degrees out of phase.

Comments related to this report
evan.hall@LIGO.ORG - 17:15, Thursday 29 October 2015 (22964)

The filters we used do do the feedback are scattered somewhat randomly, based on what SFMs were not in use for damping:

  • ITMX: mode 5, FM6
  • ITMY: mode 8, FM10
  • ETMX: mode 5, FM7
  • ETMY: mode 6, FM7

As Borja said, each of these FMs is a bandpass from 1450 Hz to 1500 Hz. They have 120 dB of gain, and we use an additional 100 dB in another filter module.

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