Report for last Friday 5/17

Conclusion: Thermal paste is of little use, but low current seems good enough to suppress solenoid heat.

the thermal conductivity of thermal paste is 16 W·m⁻¹·K⁻¹ 
the thermal conductivity of  steel is around 46 W·m⁻¹·K⁻¹ 

Because last Thursday we loose the spring of B2 solenoid and use the thermal paste  at the same time, the experiment condition is not good, so we recover the spring of B2 and test agaiin.

B2 with thermal paste,see Fig,1 :
During this test, first we increase the current to 240mA/18V, then down to  110mA.
The start temperature is 29.1 deg (time: 12:25), end temperature is 31.7 deg (time: 14:32) . The temperature just rise 3 deg, so we test A2 solenoid to confirm it.

From here we fix the FLIR camera on the top.

A2 without thermal paste,see Fig.2:  start current 210mA/15.7V, then down to 70mA/5.32

start point: time:15:30, 27.1 deg.
end point: time: 16:47, 27.4 deg (16:30, 27.7deg).

Then we increase the  current up to 280mA/22V for 30mins (similar as the shutter drive.16:47-17:18), the temperature up to 42.1 deg, (the temperature is 37.8 when time is 16:56, 9mins after increase current.Fig.6).
After that we down the current to 70mA/5V, it takes 45min to cool down to 27.7 deg (17:18-18:04). see Fig.3.

A2 wit thermal paste,see Fig.4:  start current 210mA/16V, then down to 70mA/5.2V.

start point: time:18:50, 26.2 deg.
end point: time: 19:52, 26.5 deg.

Then we increase the  current up to 280mA/22V for 9mins (similar as the shutter drive,19:52-20:08), the temperature up to 38.8 deg.see Fig.5.

Low current test (keep open at 70mA)

glue is thermal paste, temperature is deg C.

High current to imitate shutter driver (keep open at 280mA)

So the thermal paste is almost useless, might because its thermal conductivity is much smaller than shutter base (it is stainlesssteel). But the heat at low current is much lower than the heat at current provided by the shutter driver.
If we can make a new driver which can provide low current, it seems worthy to  test the shutter in PSL.