[Kira, Kevin]

We built and tested the heater circuit described in 40m:13272 in a rack mount box for the PSL lab. It seems to be working well and we will take a noise spectrum tomorrow.

The final version of the circuit as built is shown in the first attachment; the finished box is shown in the subsequent attachments. The resistor and capacitor added on the input from the DAC forms a 0.1 Hz low-pass filter. We also added +/-15V regulators to power the op-amp and LEDs to indicate when the board has power. The DAC input is from a D9 connector: pin 9 is the signal and pin 4 is ground. The output to the heater is with a LEMO connector. The board is powered with +/-24V with the connectors as described in D1002209. (The board is currently using the conventions for 18V, but Koji just gave me the 24V connectors so we can change them tomorrow.)

To test the circuit we wrapped a heater around an aluminum block attachment and then wrapped that in many layers of insulation as is shown in the last attachment. With 800 mV DAC voltage, the temperature rose from 27.2C to 31C in 10 minutes; after 45min it rose to 34.8C. The MOSFET did not get warm during this period.