A mock-up of our pendulum hanging in our enclosure. The magnets are gold plated Neodymium magnets (1" diameter), and they sandwich the fiber between to identical aluminum disks. The final pendulum will have 4 magnets and the outer magnets will have 50mm diameter front surfaced mirrors super-glued in place; the aluminum disks are designed so that the pendulum will have equal moments of inertia about each principle axis.

Our machinist (Steve Innes) has finished the main enclosure. Now what’s left is for me to give him plans for the optical system. I’ll be designing two different optical systems. The first will mount on the rotating plate visible in the photograph and will be used for calibrating the pendulum (finding out the torsion constant and the moment of inertia — simultaneously; but that’s a story for a future post). This internal system will be removed after the calibration is complete, and replaced with an optical system on the exterior plate (removed so that you can see the interior).
Now, I’m awaiting a new quadrant photodiode, as I fried the old one by back-biasing the diode accidentally. If there’s good news in this, it is that I found a source that sells the same detector for a cheaper price — Pacific Silicon Sensor.

Tagged with: