User:Asampino
AS Spring 2015
Over the semester I worked on fiber production and the heating chamber construction and set up. My daily log can be found here.
Fibers
In order to properly fuse the light guides to the scintillating fibers a mirror finish was needed on each fusing face. To minimize polishing time, fibers were bundled with an adjustable collar so that many of them were polished at the same time. The fibers were aligned so that their faces were flush with each other and the collar was positioned about a millimeter below the faces so that they were protruding. The faces were then rubbed in a circular motion on two thousand grit sandpaper until all of the fibers had smoothed out. To remove residue, the faces were rubbed on clean printer paper until they were completely clear. This residue removal was the most time consuming part of the process. After thirty seconds of rubbing the faces on the paper most of the residue was gone, but due to slight variations in protrusion length from the face of the collar, not all of the residue would come off easily. To get every fiber the collar had to be loosened and the fibers realigned many times. It was found to be quicker to polish remaining unfinished faces individually after five to six times of attempting to polish in a bundle.
Heating Chamber
To be effective in the Tagger microscope the waveguides needed to be heated and bent in an 's' shape. This was planned to be done in a heating chamber, which utilizes a hot plate as a heat source. The box was made of thick durable styrofoam (for insulation purposes) and is held together by an insulating adhesive. The 'hot box' was preceded by a similar method, which heated water instead and was replaced due to unforeseen problems. Initial heating chamber design was simple and only included a hot plate fit into a cutout in the styrofoam along with four fans attached to heat sinks laid on top of the heater to blow hot air away. This design caused significant heat leaks and a large temperature difference across the box. To fix this, extra insulation was added around areas of air escape, the hotplate was put inside the box instead of in the cutout (which was filled), and additional fans were placed around the perimeter of the inside of the box. A Labview program was used to monitor the temperature of the box via thermistors and turn the hotplate on and off at a certain temperature. A netbooter was used to control the state of the hotplate and a DAQ was used to read voltages from the thermistors. Specifically, the program was created so that the hotplate turns off for two minutes if the temperature of the box rose above seventy two degrees celsius, then it would check the temperature again and if it was still greater than seventy two the hotplate would remain off otherwise it would turn on. The temperature seventy two was chosen since the waveguides need to be at at least seventy degrees celsius to bend properly.