first link doesn't work and a link to the manual with no comment. Not very helpful Mr. Pal

regards

Can be a reflection from APD. Try to cover the photodiode by a small sheet of paper.

Thanks,

I will try next time, when i have the possibility, the gravimeter is on tour right now.

I have to open the Interferometer to blank out the beam directly infront of the APD. Is that right?

Is that possible, when the gravimeter is assembled? What cover to open?

Regards

Erik

Just prepare the gravimeter for measurements and remove the small black cover from the rear of the interferometer. It is the same what you have to do for centering/focusing the photodiode in X-Y/Z direction with respect to the beam. Then you will see the photodiode and insert a small stripe of paper to block the beam.

Thank you very much for the quick and helpful answer.

regards

Erik

I'm not sure if it helps, just an idea...

regards, Vojtech

Dear E. Brachman,

Vojtech's idea is a good one - you can slip a piece of paper in front of the APD and see if it goes away.

My guess though is that it is actually a stray reflection from the surface of the Superspring cornercube (usually the cube is tilted enough so that its surface won't reflect into the field of the view of the telescope, but sometimes it does...). You can test *this* idea by simply blocking the test beam (it should go away with the "real" test beam). And/Or travel lock the spring and look in the telescope (the stray spot should have moved or be totally gone)

The beam is a bit annoying, but it isn't hurting anything - its large angle offset means it won't interfere with the real beams at the APD.

Happy measuring!

Cheers,

Derek van Westrum