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photodiode
Oct. 18th, 2008 04:23 amWork at the lab lately has been quite satisfying. Working with Stefan and Hartmut, our current visitors, has been quite a pleasure. I feel more confident, and have had more time to think about things on my own. Also, we've made a lot of progress.
Part of today's excitement was in replacing a photodiode.
Our gravitational wave detector consists mainly of vacuum, enclosed by a steel tube and bounded by a collection of mirrors, and full of photons. The photons, little packets of light, carry all of the information. When the photons come out of the machine, we detect them with photodiodes, which turn streams of photons into streams of electrons, which feed through electrical circuits.
We use many photodiodes, several at each place where light comes out of the machine. A photodiode itself is a tiny piece of semiconductor, carefully mounted and connected via tiny wires to some bigger wires that poke out of its little can, and connect the photodiode to a collection of electronic circuits who are sensitive to variations in the intensity of the light at radio frequency, who gather this information, and send it out over a wire to more electronics, who feed the signal into computers, and servo systems, and data analysis algorithms. Servo systems that hold all our mirrors in exactly the right places. Data analysis algorithms that will tell us when we see a gravitational wave.
I don't know how much our photodiodes cost, or where we get them, but it is clear that they are very precious.
One of our photodiodes went bad recently, and today we replaced it. The new photodiode came as all new photodiodes do, mounted in a little metal can with a glass cover on top.
The glass cover protects the delicate photodiode and its delicate wires. But for us it is a problem; the small amount of light that gets reflected by the glass window instead of going through it corrupts our measurements. We have to take off the window, exposing the delicate photodiode.
This is done with a tool known as the "can opener," because it is used for opening photodiode cans. It is from ThorLabs, an company that makes scientific optical equipment, and as far as I can tell, it is specifically for this purpose.
I strongly appreciated Stefan's tutelage in this matter; he described how to perform the delicate operation, and then promptly left the room, leaving me to perform it. Trust leads to confidence. He's soloed an airplane; maybe the philosophy comes from there.
With the new photodiode, our gravitational wave detector is able to see 8.5 megaparsecs into space.
Part of today's excitement was in replacing a photodiode.
Our gravitational wave detector consists mainly of vacuum, enclosed by a steel tube and bounded by a collection of mirrors, and full of photons. The photons, little packets of light, carry all of the information. When the photons come out of the machine, we detect them with photodiodes, which turn streams of photons into streams of electrons, which feed through electrical circuits.
We use many photodiodes, several at each place where light comes out of the machine. A photodiode itself is a tiny piece of semiconductor, carefully mounted and connected via tiny wires to some bigger wires that poke out of its little can, and connect the photodiode to a collection of electronic circuits who are sensitive to variations in the intensity of the light at radio frequency, who gather this information, and send it out over a wire to more electronics, who feed the signal into computers, and servo systems, and data analysis algorithms. Servo systems that hold all our mirrors in exactly the right places. Data analysis algorithms that will tell us when we see a gravitational wave.
I don't know how much our photodiodes cost, or where we get them, but it is clear that they are very precious.
One of our photodiodes went bad recently, and today we replaced it. The new photodiode came as all new photodiodes do, mounted in a little metal can with a glass cover on top.
The glass cover protects the delicate photodiode and its delicate wires. But for us it is a problem; the small amount of light that gets reflected by the glass window instead of going through it corrupts our measurements. We have to take off the window, exposing the delicate photodiode.
This is done with a tool known as the "can opener," because it is used for opening photodiode cans. It is from ThorLabs, an company that makes scientific optical equipment, and as far as I can tell, it is specifically for this purpose.
I strongly appreciated Stefan's tutelage in this matter; he described how to perform the delicate operation, and then promptly left the room, leaving me to perform it. Trust leads to confidence. He's soloed an airplane; maybe the philosophy comes from there.
With the new photodiode, our gravitational wave detector is able to see 8.5 megaparsecs into space.
