FMCG/Operating procedure

This section will cover everything up to the noise measurement, and will assume everything from the "Experimental Setup" procedure has been completed.

FPGA and Arduino "Reset"

Both the FPGA and Arduino microcontroller tend to behave somewhat strangely after a computer restart, so it is a good idea to "reset" both of them before beginning.

1. Open up the Arduino code. The file is in the upper-right corner of the desktop and is named Decoupling Code (with LCD). Click the right arrow (under the "Edit" menu to upload the code to the Arduino.
2. Once you receive an "Upload Complete" message in the program, the code is ready. The LCD screen should read all zeroes (or whatever values the user specified). However, because of a feature of the code, the outputs of the Arduino (and consequently, the current outputs of the current supplies) are all sent to the rail.
3. To truly set the currents to zero, turn any one of the Field Adjust knobs on the current supply box by one click. Then turn the knob back one click to return all supplies to zero.
4. Now open up LabVIEW 2014 using the shortcut on the bottom taskbar. Open the FPGA Magnetometer.lvproj project. LabVIEW will then load a bunch of programs which takes ~60 seconds.
5. Once the project is opened, inside the Main Programs folder, open the Set_AO_Zero_(Host).vi program. When the program is run, it will send a zero (reset) signal to all of the outputs of the FPGA. If an error is output when this code is run, something caused the computer to lose connection with the NI chassis and the computer will have to be restarted.

Absorption Scan

Before proceeding with a noise measurement, it is a good idea to measure the rubidium absorption in each of the cells.

1. On the array, switch the detectors to SUM mode. This is accomplished by moving both the 4-socket leads from the detector and the 2-socket leads that carry signals out of the room to the set of header pins denoted by a Σ or + label.
2. If not done already, turn on the TEC and LD for the probe laser diode (the right-hand SRS LDC501 controller). We have historically and recently run at 170.00 mA of laser diode drive current on the probe. With this drive current, the D2 absorption line occurs at a "temperature" of roughly 7.05 kΩ and we generally do our magnetometry at a temperature of 8.5-9.5 kΩ.
3. Now return to the rear of the rack and, after verifying the probe tapered amplifier TEC 2000 temperature controller is enabled, enable the probe tapered amplifier output by pressing the output button on the Newport Model 560B driver. The drive current on the TA sets the eventual light intensity on the detectors. Historically, we have worked with currents as high as 1200 mA, though recently we have worked at much lower values around 750 mA, which delivers ~500 μW of laser power through a hot cell to the detector.