Lucia, Kiwamu,
We are concluding that it s likely that the magnet for the test mass H2 coil-magnet actuator of ETMX fell off at one point.
Another possibility is the H2 magnet physically touching the coil, making us unable to actuate on the mirror. However, this seems unlikely as we don't see a significantly degraded mechanical Q in the mesured mechanical transfer functions.
[later edit]: one other possibility is that we are driving a coil of 77 Ohms which is distant from the magnet for some reason while the magnet is still on the mirror.
[Electronics seem fine]
Lucia and I went down to the X end station in this morning to check up the associated electronics as planned. This is for investigating the H2 coil issue in which the coild didn't respond to DAC request. Here is a summary of the checkup:
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The impedance of each of four coils was found to be healthy with a measured resistance value of around 77 ohms each.
- This means that there is no disconnection of the cables in chamber.
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The high power coil driver was functional.
- We were able to measure 7mA in each coil with a hand-held multimeter when a digital count of 2000 was requested at the very output of the digital system.
- Also, the voltmon showed a response to the DAC requiest in each coil.
- From these two observations, we determined that the elecronics were fine.
[Not so much Q-degradation in the mechanical transfer functoins]
Even though we still see the pitch resonances in the TMP-to-TMP transfer function at around the expected frequencies(6725), we wanted to double check if this is still the case for the TMY-to-TMY transfer function. So we measured it.
The attachment below shows the measured TMY-to-TMY transfer function of the day.
The blue trace is a reference taken by Miyamoto-kun on the 12th of August in this year. The q-value of each resonance seems degraded from the past somewhat, but not a lot. Considering this measurement and the fact that the mirror doesn't respond to the H2 coil current, we conclude that the H2 magnet is not coupled to the coil --- the magnet is likely gone.
The measurement is saved at
/users/VISsvn/TypeApayload/ETMX/TF/Measurement/20180826
Similarly, the mesurements from yesterday (6725) are saved at
/users/VISsvn/TypeApayload/ETMX/TF/Measurement/20180825
