Problem with Square WLS Fiber Optic Cable A

Problem with Square WLS Fiber Optic Cable A report on the observations of the physical response to square WLS fiber optic cable being applied and glued in place into the Sigma Groove of the hexagonal scintillator tiles

What are We Doing? n n Measurements were taken at Fermilab with the WLS fibers applied, but glued/not glued into the Sigma Groove Both situations had the cells wrapped in Tyvek The scintillator tiles (hexagon (3, 4, and 5 mm thickness, 10 each) and square (5 mm, 10 total for each surface area), 9. 4 cm^2 and 6 cm^2 surface area each) from Eljen scintillator stock 9 hexagon, 9. 4 cm^2 surface area, 5 mm thick tiles from the extruder

What is being investigated? n n Light output at each instance (with and without gluing) of the many types of scintillator (Sasha’s Presentations) The condition of the fiber and cells as this process happens (this presentation)

What was done? n n A laser pointer was put to the end of the WLS fiber and the cell was illuminated The length of fiber was checked for cracks Cracks show up as bright slivers in the fiber of red light Each cell was documented as to the degree of damage there was

53 of 66 Were Damaged!!!

What kind of damage was observed? n n From just one small crack on the outer radial cladding to the entire outer cladding cracked the entire length of the glued part of the fiber This is mechanical stress damage Similar to stress and strain tests in material sciences. These are stress fractures. And, was the new Eljen glue responsible for the damage? ? ? Sasha and I are on the case!!!

How to use this data for the future investigations n n The square fiber is extremely sensitive to mechanical interactions Square fibers do not appear to be a usable WLS fiber solution Investigation of possible glue damage is in the works, without mechanical stress Round fibers appear to be a better solution from past experience, even with smaller sigma groove radius