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AOS (Baffles & Beam dumps)
simon.zeidler - 22:41 Tuesday 17 April 2018 (4736) Print this report
WAB cooling test: coil-magnet actuation and heater-effect

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

Images attached to this report
Comments to this report:
tomotada.akutsu - 23:43 Tuesday 17 April 2018 (4737) Print this report

> Then, we started the test with coil-magnet actuation (1V, 0.33A)

Actually, we used two current sources, and each of which showed 1V, 0.33A, and they are connected in serial, so actually, it was 2V, 0.33A.

 

About the heating, I often checked the temperature of the cooler heads and walls of 8K and 80K shields, and found no meaningful changes even in the cooler head that connects to the WAB; that was around 16-15K.

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