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Entry   High frequency noise, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics 
    Reply   High frequency noise, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics 
       Reply   High frequency noise, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics 
          Reply   High frequency noise, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics Accelerometer_on_door_wo_noise.pngAccelerometer_on_door_with_few_noise.pngAccelerometer_on_door_with_few_noise2.png
             Reply   High frequency noise, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics AC-line.png
Message ID: 458     Entry time: Wed Oct 1 10:14:12 2025     In reply to: 457     Reply to this: 459
 Author: Ronic Chiche 
 Status: Under Process 
 Type: issue 
 Category: lasers and optics | detectors and electronics 
 Location: ThomX igloo 
 Title: High frequency noise 

At the end of the day, we found out what was the origin of this noise : some road renovation work with jackhammer and road roller just at the entrance of the "Igloo".

this origin was 100% correlated with a large increase of the accelerometer signal.
but we clearly saw that the FPC is much more sensitive than the accelerometer... the signal can have a small increase or just one peak and the cavity lock is lost.

then, we can make the assumption that all the "high frequency noise" which produces some lock losses could come from acoustic noise due to the road traffic or from the equipments in the bunker itself.

Ronic Chiche wrote:

Today, the lock of the FPC was particularly bad (maybe the worst ever seen), with a lot of high frequency noise.
the lock was impossible during several minutes !

we tried to switch off all the equipments of the machine, one by one without any effect on the lock.

at the end, we looked at the accelerometer installed inside the housing to check if there was some correlation.
and for the 1st time we clearly saw a 100% correlation beween the accelerometer signal with a noise oscillating above +/-300mV
but we didn't find the origin of this noise.

 

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