1. How to paint a masterpiece? American Gothic, 1930 Grant Wood

2. Paint by numbers! Everyone can be a Rembrandt!

3. Paint by which numbers? The numbers –Weight Measured with scale –Thickness Measured with a caliper The goal –To quantify the amount of paint applied to each cell –To define “layer” of paint

4. “Paint by numbers” instructions New cell, no paint –Weigh and measure Paint one face and two edges with four layers –Weigh and measure Paint the other face and other two edges with four layers –Weigh and measure –Sasha measures response Paint one face and two edges with four more layers –Weigh and measure Paint the other face and other two edges with four more layers –Weigh and measure –Sasha measures response

5. Logical trend? Cells with thicker paint tend to be heavier

6. Weight of paint

7. Weight of paint w/error bars

8. Change in weight for every four layers

9. Change in weight w/error bars

10. Problems in weighing The scale never settles down –It is constantly changing by about +-0.025 grams Maybe the scale needs to be in a location shielded from air currents and vibrations

11. Layer resolution via weighing Looks like we can resolve 0,4,8,12,16.. layers as f(weight) –4 layers = ~0.2 grams Doubtful that we could resolve 0,1,2,3…. layers –1 layer = ~0.05 grams which is the size of the error bar

12. Thickness of four layers

13. Problems in measuring thickness Don’t know what error bars to apply Measured the thickness at 3 corners and at one point across the fiber to the middle of the cell The surface across the fiber is VERY flat (due to Sasha’s cleaver and careful gluing technique!) However, noticed slightly different thicknesses for each corner 1 2 3 4

14. Problems in measuring thickness The problem is that ridges tend to form along the edges –Partly due to painting the edges –Partly due to gravity

15. Problems in measuring thickness As the number of layers increased, so did the height of the ridges around the edges This increase in the problem can be seen in the increase in the spread of the data with the number of layers (next slide) The thicknesses measured for a cell varied by ~0.05mm (for min amt of paint) to ~0.10mm (for max amt of paint) Compare to “average” thickness of 4 layers is ~0.25mm (next slide) ~0.05mm

16. Thickness of four layers

17. Problems in measuring thickness This made it impossible to obtain an accurate measurement of the thickness with a caliper But using a micrometer to measure the thickness at the interior of the cells worked quite well (next slide)

18. Caliper vs. micrometer

19. Next time? If the current strategy does not seem like it is worthwhile, we might want to pursue the light transmission idea which Manuel has a concrete scheme for OR I could try again: –Use the scale in a shielded area –Be more careful about painting edges to avoid ridges –Use a micrometer to measure thickness Then maybe I can get a better measure of what a layer is….

20. …and maybe then I’ll paint a masterpiece!

21. Paints Experimented with –EJ-510 100% Paint 80% paint, 20% water –Liquitex Medium viscosity 50% paint, 50% airbrush medium –Liquitex High viscosity 50% paint, 50% water

22. EJ-510 reflective paint EJ-510 Primarily intended for coating of blue-emitting plastic scintillators EJ-510 employs a blend of pigments selected aslo for enhanced reflectivity for longer wavelength scintillators This may be why its reflectivity is higher than that shown for TiO 2 in textbooks (next slide)

23. Reflectivity of TiO 2 Curve roughly superimposed using data from Techniques for Nuclear and Particle Physics Experiments, by W.R. Leo, p.200 Note that the BC-408 (the scintillator we are currently experimenting with) spectrum peaks at 425nm. BC-408 TiO 2 EJ-510

24. Microscopy for cells Contacted Prof Ito (NIU) –He’ll look at some samples of our cells with an optical scope, but will not have time for a couple of weeks –He said that the TEM (NIU) will not work for our samples (need thin section) –He said he could try the SEM (ANL) but was pessimistic that we could get any useful information from it The e- would scatter in plastic (the energy of the e- are ~125keV)