Abstract
- We continued to survey the ADC noise issue on ITMX.
- We was able to confirm that there is no change in the glitch situation by the difference of KEPCO 30A power supply unit and a dedicated one.
- Presence of the 3rd AA (S2111159) seems to cause ADC glitches on the 1st and the 2nd ADCs though the 3rd ADC seems to be most quiet one.
- All measurements are stored in /users/DGS/measurements/ADC/K1IX1/2022/0520/*.xml
- After this work, I found too large glitches on MN_PS_V1.
- Now MN_DAMP_{R,P} cannot be engaged and Ushiba-kun implemented OLDAMP as temporal solution.
- We will check MN_PS issue on next Monday. (Hopefully Satellite box or CoilDriver was damaged.)
Details
As I reported in klog#20715, I found ADC noise can be removed by using a dedicated power supply unit for AA chassis on ITMX.
On the other hand, a dedicated power supply unit didn't work well on ETMY as reported in klog#20762.
The difference between surveys on ITMX and on ETMY was the number of AA chassis which was connected to the dedicated power supply unit.
Only the 1st AA (AA0) was connected on ITMX and all three AAs (AA0, 1, 2) were connected on ETMY.
Difference by power supply unit
In addition to the above uncertainty, a question that which KEPCO 30A power supply or a vacuum chamber side is cause of this problem.
In order to find the answer of them, we checked the ADC noise with various situation listed as follows.
- Only AA0 was connected to KEPCO 30A power supply
- All three AAs were connected to KEPCO 30A power supply
- Only AA0 was connected to the dedicated power supply
- All three AAs were connected to the dedicated power supply
At this time, all circuits except AA chassis were disconnected from power supply.
Only in the case 1. and 3., ADC noise became quiet and glitches presence in the case 2. and 4.
This means that there is no difference between KEPCO 30A power supply and the dedicated one.
And also, some of (or combination of) AAs are noise sources.
Combination of used AAs
As the next, we checked the combination of AAs which was turned ON as follows.
- Only AA0 was connected to the KEPCO power supply
- AA0 and AA1 were connected to the KEPCO power supply
- AA0 and AA2 were connected to the KEPCO power supply
- AA2 were connected to the KEPCO power supply
In the case 1. and 2., ADC noise became quiet and in the case 3. and 4., ADC glitches can be seen on all ADCs connected to AA.
(The case that all AAs were connected to the KEPCO power supply was already confirmed in the check of power supply difference.)
AA2 itself seemed to be healthy because channels on AA2 were most quiet in all AAs on ITMX.
But when AA2 was connected to same power supply with AA0 and/or AA1, glitches didn't occur only on ADC2, but also on ADC0 and/or ADC1.
Swap test of AA and ADC combination
Because of this results, we doubted the AA2 and/or ADC2 as the cause of ADC glitches.
Finally, we measured the ADC noise by swapping the combination of the connection between AA and ADC.
In this test, ADC0 and ADC2 were connected to AA2 and AA0, respectively.
A result is the ADC0-AA2 had many glitches and ADC2-AA0 didn't have.
So we concluded the cause of this issue was AA2, not ADC2.
We plan to replace AA2 as spare one and current AA2 will be tested at Mozumi in next week.
Accidental troubles on MN_PS_V1
After this work, we reverted all situation and tried to revert ITMX as ALIGNED.
But MN_PS_V1 has too loud glitches which cause the DAC saturation in DAMPED state.
This channel is assigned on CH4 of ADC1. Because we mainly touched ADC0 and ADC2 today, we cannot any idea about the reason why such a change in the situation...
Because we didn't enough time to investigate this problem, we plan to do detailed checks in next week.
Hopefully, coil driver and/or satellite box may be damaged at turning ON/OFF power switch of each circuit (not a damage on photo sensor in the vacuum...)
As the temporary solution, Ushiba-kun implemented the MN_OLDAMP filters. So ITMX can be damped and aligned now by using MNOL instead of PS.