Post by karimadel on Mar 23, 2021 12:25:24 GMT -5
Hello,
I have recently purchased a vpf-100 cryostat, which works with LN2. To check that my experiment works properly, I have tried to calibrate the temperature on the substrate using a pt100 sensor and compare it to the reading of the silicon diode sensor at the top of the sample holder. As shown in the figure, I observe a large deviation in the reading of both sensors. At the beginning, I doubted the anchoring of the pt100 sensor, especially when you observe at around 200K, the reading increases instead of decreases !!
However, I started measuring my diode samples, which should show a very systematic increase in voltage while cooling down. Surprisingly, I found that at around 200K, the voltage decreased with decreasing temperature. Therefore, I concluded that it is the thermal anchoring of the sample which has a problem. I use Apiezon N grease for both the substrate and the sensor.
For completeness, I am using a custom made copper holder, which has a hole in the middle similar to the optical sample holder of Janis. I used 4 point measurement for the pt100 sensor. The substrate material is glass.
Any suggestions or ideas are welcome !
Thanks in advance
I have recently purchased a vpf-100 cryostat, which works with LN2. To check that my experiment works properly, I have tried to calibrate the temperature on the substrate using a pt100 sensor and compare it to the reading of the silicon diode sensor at the top of the sample holder. As shown in the figure, I observe a large deviation in the reading of both sensors. At the beginning, I doubted the anchoring of the pt100 sensor, especially when you observe at around 200K, the reading increases instead of decreases !!
However, I started measuring my diode samples, which should show a very systematic increase in voltage while cooling down. Surprisingly, I found that at around 200K, the voltage decreased with decreasing temperature. Therefore, I concluded that it is the thermal anchoring of the sample which has a problem. I use Apiezon N grease for both the substrate and the sensor.
For completeness, I am using a custom made copper holder, which has a hole in the middle similar to the optical sample holder of Janis. I used 4 point measurement for the pt100 sensor. The substrate material is glass.
Any suggestions or ideas are welcome !
Thanks in advance
