BW March 2018

3/2: I ran one test in the morning on bundle 401, but the graphs did not look right. I talked with Jim about that, and he said we should ask Dr. Jones. We did not have a chance to address the issue.

I polished the bundle of sci-fis with 1000 grit until I decided I had gone on long enough, really too long, and it was time to change to 5 micron grit. I was consistently measuring a length around 0.798", which is acceptable since the goal is a length of 0.787" +/- 0.039". For the next bundle of sci-fis I will polish away more with the 400 grit. Maybe I should start using the 1000 grit when I am 0.012" from the goal of 0.787".

I polished one end of the bundle with 5 micron grit and started on the other end.

3/5: I ran one test this morning but after that the tests wouldn't complete. Jim said I should ask Dr. Jones whether the problem from Friday was solved before doing more tests. Dr. Jones said we could accept the data after run 1391 and did not need to discard runs 1392 or 1393.

He also said unplugging the cable would not fix the problem of runs not completing.

I practiced fusing again. Last month after Jim worked on the splicing unit I couldn't adjust the left pressure regulator. Today I found that if I pulled the knob up, I could twist it easily.

I polished the sci-fi bundle some more. I picked the end that looked better after the 5 micron grit as the fuse end. I will continue polishing the other end with finer grits, but when I get to the copier paper I want to see if that will improve the fuse end as well as the free end.

I helped Andrew Craig get started on polishing and fusing fibers.

I checked the results of runs 1392 to 1396, and the means were within a range of 10 pixels, so I unplugged the electronics, removed the pre-amp boards, and verified which color codes were in which chimneys.

3/6: Andrew and I continued polishing the sci-fi bundle with copier paper. I am not quite sure I am done. Striations and scratches are still visible on both ends. The fuse end has some steeper ones that may be deeper than those on the other end. I plan to leave that bundle in the collar for now and show someone at some point.

3/8: Andrew and I switched the strongest and weakest fibers in Bundle 401 and checked the position of all the fibers in the bundle. The fibers should remain in the same bundle positions for the rest of our normalization tests. The position numbers will not change.

I did some more fusing practice, and I cut some more short pieces and removed previous practice fuses from the long ones so I can reuse them.

3/9: I tried to align Bundle 401 for testing, but it proved unsatisfactory when I put it in the dark box. I want to develop a method of holding the fibers so they will keep the right alignment regardless of bending.

I prepared to polish another bundle of sci-fis. I tapped a new collar and put the fibers in it.

This time I want to twist the sci-fi guide to the right again (right in front and left in back), but always gently rather than sometimes putting too much force on it. Maybe then the sandpaper will reach all the fibers.

3/12: Andrew and I aligned the fibers in Bundle 401 for testing, and I ran some tests after putting the fibers in the dark box. I practiced fusing, and we continued polishing the sci-fi bundle started on March 9. We were using 400 grit. After Andrew left, I adjusted my polishing method and increased the rate of progress. I kept twisting left at the rear of the sci-fi guide, but at the front I no longer twisted right. I used my hand at the front to hold the sci-fi guide down and press forward right behind the collar.

With my new method, the sci-fi guide is still twisted right in front and left at the rear, but the twisting force is applied only at the rear. The fibers are held against the wheel with more force, so polishing goes faster.

3/14: I ran a fourth set of tests on light guide Bundle 401 with a middle fiber pushed back from the regular alignment to test how much results change when fibers are misaligned.

I also continued polishing the sci-fi bundle with 400 grit, and things went wrong while I was polishing. At some point I noticed that I had suddenly run almost out of polishing room on one end of the bundle. I had around 0.005" to go before the fibers would no longer be in contact with the sandpaper. That was startling because my micrometer measurements indicated that I needed to take off 0.04" or more to reach the target length for sci-fis. I thought the collar might be too narrow and I might need to use a piece of cardboard to bring the collar and the fibers closer to the wheel. Otherwise, with only 0.005" left I might not be able to polish adequately with the 1000 grit and finer grits.

However, before trying anything with cardboard I turned the collar around and began to polish the other end. Again the progress seemed very rapid until I noticed that the end with 0.005" left had changed. Now instead of barely sticking out beyond the collar it looked longer than the end I was polishing. Then I realized that the fibers were slipping back in the collar as I was polishing. Immediately I tightened the screws in the collar. They were indeed loose enough for the fibers to slip.

This slipping was a setback in polishing the bundle because it meant that the fibers were still not all the same length. The end of the bundle looked flat on the side I happened to be polishing, but the opposite end was uneven with some fibers sticking out farther than others. However, with around 0.04" left to remove, I had hope to correct the situation. The uneven end did not look too bad, and after some more polishing that took off another 0.02", that end looked flat again and the fibers did not seem to slip.

I think the screws may have been too loose to begin with, but they may have loosened further during polishing. In the future I have to make sure the screws are tight enough and keep checking them from time to time so they won't loosen and let the fibers slip.

3/15: I talked with Jim about polishing today. He said that if you change the twisting even at the end with finer grits, it can present a much different surface area to the paper than previously. If the fibers are twisted consistently and then changed, there may be a much smaller area of contact and therefore a much higher pressure than before. The higher pressure may melt the fibers. Also, it is not good to blow on the fibers because of the moisture in breath.