scintillator polishing

[bwsparxz]

What seems to be the best way to polish plastic scintillators? Like what grit to finish with and a final polishing compound. Any experience on this.

[ningauble]

Commercial plastic lens polishes are more abrasive than glass
polishes such as cerium oxide, they usually are a fine aluminium
oxide. Plastics can tolerate quite high polishing speeds if the
polish liquid has a high flow rate and chilled to about 5 deg C.

The tough part is that all plastic lens polishing is usually
done on toric section curves. Once a flat is attempted in
standard machines things tend to come loose and smash all
over the room. I polished my 5" scintillator by using rough, fine,
extra fine and finally cloth, self adhesive petal pads (optometry)
stuck to a glass sheet with alO plastic polish on the final cloth
glass polish pad. Be prepared to spend a lot of time and end up
with a slight turned down edge on the scintillator from the cloth
pad. If you can find an optom workshop to get petal pads from,
don't get the "One step" laps as they are a sandwich of two
different abrasive layers of which the upper one dissolves and
wears off so the finer abrasive can do it's work. Polycarbonate
pads are a better choice as they are wet and dry carborundum
in three grades up to a pre-polish.

Mark Harriss

[Tom Dressel]

I used progressively finer "wet or dry" sand paper (3M), on a sheet of plexiglass (flat), under running water, to wash away any loose abrasives that can cause scraches. Grit ranged from 350 to1500. Then finish off with rubbing compound on a lams wool buffing wheel in a drill press. The entire process from rough sanding to finished polish takes about 20 min.

Tom Dressel

[Richard Hull]

A final high polish can be had with NOVUS plastic polish, available in two grades. I use a terri-cloth towel and moisten it with the liquid paste polish. This can be found at any plastics supplier. Prior to this point and for the "rough-in" I use wet sand paper up to #1200 grit.

Finally, as you are forced to optically couple the scintillator, any scratches or micro pits will be filled and made totally transparent as the silicone optical coupling compund oozes under pressure into the imperfections.

Richard Hull