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YuhangZhao - 16:43, Thursday 07 January 2021 (2328)Get code to link to this report
Investigation of 20kHz noise in SHG error signal

Marc and Yuhang

We used signal generator AFG3102 to modu/demodu SHG fields (instead of DDS1). At the same time, all DDS boards were taken out from rack. Then we locked SHG and checked error signal spectrum. We found 20kHz noise disappeared. Figure 1 (SHGNODDS.txt) shows error signal spectrum in this measurement.

After that we also checked the rack voltage, which may change due to large power consumption.

  no DDS all DDS
+24 24.04 24.04
-24 -24.04 -24.04
+12 12 12
-12 -12.03 -12.03
+6 5.837 5.837
-6 -5.995 -5.995

We measured error signals when there were DDS1 only (DDS1.txt), DDS2 only (DDS2.txt), DDS3 only (DDS3.txt) and clock removed (no clock.tx).

Comments related to this report
MarcEisenmann - 18:17, Thursday 07 January 2021 (2329)

Participants : Marc, Yuhang

Here are the figures :

First no DDS board connected to the rack : all the peaks disappear.

Then, DDS board connected one by one we can see that each DDS is causing one of the peak around 20 kHz.

DDS1 -> 18 112 Hz

DDS2 -> 17 728 Hz

DDS3 -> 21 312 Hz