Michael's Lab diary

Reviewing Computational Projects

2012-01-15T12:16:00.000-08:00

Currently i am in the process of reshaping my computational infrastructure. I got from a friend intersting comments about the N body system calculation. Currently i am trying to improve the performance of the PSim algorithm by porting the old code the an16 Processor cloud CPU.

Working on the Random Project

2012-01-15T12:11:00.000-08:00

I started to review a lot of my old projects. I am reshaping the random projects by creating a new setup for collecting background radiation data and deriving out of it data using a C++ evaluation program.

I finished most of the web page for the project.

http://www.michaelerdmann-berlin.de//Random/index.html

The automatic publishing of the measurements is under construction.

Getting rid of vibrations in my opticalbench

2012-01-04T21:47:00.000-08:00

I have setup an Michaelson Interferometer as shown below; this setup is very sensitive to vibrations.

I am using a photp diode to detect the intensity of the light in the project plane of the Michselson setup as shown above to detect vibrations.

Without an active laser I get a frequency spectra like this:

with actice laser I got a completely different frequency spectra.

This spectra seems to be caused by the vibrations MBUS frame which containes two power supplies. If i am turning the mbus off, the additional peaks do disappear.

A reasonable solution seems to use some commercially available gliders made of sleaze as dampers on the MBUS frame. After applying there dampers to the MBUS frame the frequency spectra looks as below:

Work is going on .. :)

Towards an stable Avalanche Photo Detector (APD)

2012-01-03T12:29:00.000-08:00

Currently i am working on a highly sensible photo detector based on an Avalanche Photo Diode. Like any photo diode it will be operated by biasing in such a way that no current flows because of the diode barrier. The APD will be operated very near the break through voltage. A group of photons will ionize the barrier creating free electrons which are accelerated by the bias of the diode; which in turn will create new free electrons. The mechanism is quite comparable to the geiger tube.

There are two major key factors controlling the operation of the APD:

Stability of the bias voltage
Temperature of the diode

The dark noise of the diode will be extremely reduced if the diode is cooled down to about -20 degrees. This is achieved by using a Peltier element.

The picture below shows the test setup. In front you can see the APD (the black part left) which is mounted on Peltier element for cooling which is mounted on a processor cooler with a fan. In the back you can see the power supplies and the experimentation board with the controller circuit.

The uppoer power supply operates as about 8V and provides the current for the Peltier element. The bottom one provides the voltage for the controller circuit shown below:

The results which have been achieved can be found here: http://www.michaelerdmann-berlin.de/hopeless/apd/cooling.pdf

The next step will be the implementation of a controller which which regulates the temperature of the APD. I put it on hold in favor of the Random project.

Starting my Lab Diary

2012-01-03T11:38:00.000-08:00

This will be my lab diary for http://www.michaelerdmann-berlin.de/. Have fun reading it :-)