Today we test the B1 solenoid which is put on the optical bench in PSL, temperature of B1 is about 40 deg, then we uninstall B1 and put B2 on the shutter base, but B2 heat soon from 26 deg up to 47deg, at same time IMC become very noisy, in order to not disturb the commissioning work, we change B1 solenoid back and measure the temperature by FLIR camera, the temperature of B1 rise from 27 deg goes up to 44.5 deg in 12 mins.

After we come back to Mozumi, we test the A2 solenoid, it need lower current compare with A1, it also has lower heat.
It need aroud 210mA (votage is around15.8V) to close the solenoid, and the solenoid will open again when the current down to 60mA, during the heat test, first we adjust the current up to 210mA to close the solenoid, then we directly decrease the current down to 70mA (votage is around 5V), then we observe the temperature of the solenoid by FLIR camera.
At the beginning the temperature of A2 is 28 deg, then it goes up to 33.5 deg see in Fig.1 (13:13), then the temperature rises up to 36.2 deg see in Fig.2 (15:01).

Then we test the solenoid driver, it provide 24V votage and around 280 mA current for the solenoid, under this power supply all of the 3 solenoid (A1/A2/B2)  will heat  from around 30 deg up to 50 deg in 5mins.
B2-Fig.3, time: 16:18-16:23, temperature: 31.2 deg - 51.6 deg
A1-Fig.4, time: 16:25-16:30, temperature: 30.7 deg - 54.8 deg
A2-FIg.5, time: 16:42-16:47, temperature: 29.9 deg - 52.5 deg

Tomorrow the cooling fin will delivered, we will test it with the 3 solenoid.

Today we test B2 solenoid with shutter base and thermal paste,see Fig.1.

First we test the B2 solenoid without heat sink, we rise the current up to 240mA/18V to move the solenoid, then decrease the current down to 110mA/8.26V
The start temperature is 27.7 deg C (13:29), 90 mins later, the temperature rise to 34.6 (15:13),see Fig.2, this temperature is lower than yesterday's test which is without shutter base, the temperature of  the other side of the solenoid is 36.9 deg C, see Fig.3

Then we put the thermal paste on the surface between the soleniod and solenoid base, and the surface between solenoid base and shutter base, in this process, we found that the spring of the solenoid can be adjust manually, see FIg.4, we  loose the spring of A1 and test the current to move it, the current is about 200mA, and the minimum current is around 60mA, it is lower than before, actually it make sense, the needed force is smaller because the spring is loosed. Then we loose the spring of solenoid B2, it turn out that the it only need 180mA/13/5V to move the solenoid and the minimum current to keep it open is down to 85mA/6.38V, it was 240mA/110mA.

Finally we the the solenoid at lower minimum current (85mA/6.38V).
The start temperature is 31.2deg C (16:03), 2 hours later, the temperature rise to 34.1 (17:58),see Fig.5,  The temperature increase by only 3 deg, it might because of the lower current. And the hot part is on the bottom of the solenoid, the top part is not so hot, we believe that  this is due to thermal paste.
The temperature of  the other side of the solenoid is differ as the position of  the camera change see Fig.6-8,
Fig.6-36.5 deg C, 
Fig.7-34.9 deg C, 
Fig.6-31.8 deg C, 
Next we need figure out the calibration of the FLIR camera.

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.

Report for Tuesday (5/21), with Tomura san, Kokeyama san, Miyakawa san

Shutter solenoid heat can be suppress by draw low current/voltage

We found shutter drive circuit can provide a low voltage V2 see Fig.1, but there is no V2 power supply, so we modify the connection of shutter driver and directly connect V2 to  a DC power supply. We removed the diode, so when we close the shutter (remove 5V control signal), the voltage of V2 will change from V2 to -V2, see Fig.2, that mean the current on solenoid is same with it open.

We test low current condition  with B1 solenoid in PSL room.

Before we test B1 solenoid, we loose the spring of B1 to lower the minimum current, after several  test we choose 9V/110mA as V2 voltage, solenoid can be open under power supply is 8.8V/103mA,see Fig.3.

We also put FLIR camera to monitor the temperature, see Fig.4, after more than 12 hours, the temperature is still around 24 deg, under this configuration, IMC REFL signal is super stable. 

Next:
We will purchase a 9V regulator and install on  the shutter driver to provide a low voltage to V2, we will test it after finish the modification.