B. Montanari, I. Nardecchia, F. Nocera, G. Sposito

Overdue entry with plots justifying the conclusions listed in the entry 66724.

After a few days of discussion of this topic it looks like some people are still confused regarding the pieces of the puzzle. Here's a brief recap.

The Ring Heater system for a given tower (in our case, WE) consists of
- one Keysight N6700 Modular Power Supply, which in turn is made of
    • a single mainframe, or chassis
    • 2 separate N6752A 100W Power Modules, each one driving one Ring Heater
- cabling, both in air and, after the flange, in vacuum
- 2 Rings, driven with opposite polarities.

A block diagram is provided, I hope that helps.

And now the measurements.

Fig. 1 shows the measurement taken on May 6th at the WE using the spare mainframe and one of the two already installed Power Modules. It shows that when the output is disabled, there is no 3 Hz comb, while when it is enabled is always there and with the same magnitude no matter what the required voltage and current are

Fig. 2 compares measurements taken at WE with the ones taken at NE. It shows that different power supplies have slightly different combs (frequency is not exactly the same) while comb magnitude does not change.

Fig.3 displays side by side 4 different power supplies (WE, NE, PR, WI) further confirming each has its own signature comb, as it is easily visible in Fig.4. a zoomed-in version of Fig. 3

Finally, a couple of points are addressed by the last two plots.
Fig. 5 shows that the comb is a characteristic of each power supply and is not influenced at all by where the power supply is located; the spectra for the spare one as measured at WE and in the Electronics Lab are the same.

Fig. 6 instead shows that the comb is a feature of the mainframe and not of the power modules it hosts (Ch1 and Ch2 are equal)