Akutsu-san, Miyo-san, Simon

Today we aimed for the first measurements of the damping and the heater of the baffle under cryogenic temperatures.
However, the results that we got were a little bit unexpected...

• At first, we measured the spectra of photosensors and OpLevs before the actuation started. It turned out that we don't have the 1Hz swing-eigenmode of the baffle anymore but therefore a 2Hz mode which didn't show-up before the cooling down (see picture 1)
• Then, we started the test with coil-magnet actuation (1V, 0.33A)
• The time-series of the sensor's output can be seen in picture 2. We did not get any oscillations from the swing-modes (X and Y photosensor) and a ~4Hz vertical oscillation (Z photosensor) where there was a 3.5Hz mode before cooling down. Instead of X and Y mode, we have the typical saturation-curve of an overdamped oscillator...
  (see picture 3 for the spectra rigth after coil-actuation)
• We think that the copper plates have now a conductibility which makes the Eddy-current damping too effective
• Then, we switched-on the heater with 11.4V and 0.39A, thus ~3.3W direct input to the heater, at around 14:15 and observed an immediate response of the temperature sensors on the WAB itself (1,2,3, and 4)
• The temperature curve showed some tendency to conjugate but even at 17:30, the temperature was still rising (from 26K to 57K). Sensors 5 and 6 remained at 40 and 42K, respectively. However, we had to break-up the heater-test at this point
• It seemed to us that the cooling for the baffle is too weak...

We want to repeat the heater-test tomorrow from the early morning to have more time in estimating the equilibrium temperature