P.S.Flower RAL PPD, CMS Meeting CERN, 1st. Feb The selection of an adhesive for bonding the VPTs to the PbWO 4 crystals in the end cap electromagnetic calorimeters P.S.Flower RAL

P.S.Flower RAL PPD, CMS Meeting CERN, 1st. Feb Contents Dow Corning RTV 3145 Adhesive Requirements Refractive index Transmission Radiation damage Gluing Drying of glue Handling Unbonding Conclusion

P.S.Flower RAL PPD, CMS Meeting CERN, 1st. Feb Requirements Refractive index between 1.5 and 2.18 Transmits UV Does not darken under radiation Does not embrittle under radiation Bonds well Does not impose stresses on crystal Stable for life of experiment Does not form bubbles Dries quickly Easy to use Can be unbonded

P.S.Flower RAL PPD, CMS Meeting CERN, 1st. Feb The effect of μ of adhesive

P.S.Flower RAL PPD, CMS Meeting CERN, 1st. Feb Refractive index of RTV a = b = c = d =

P.S.Flower RAL PPD, CMS Meeting CERN, 1st. Feb Sample preparation 1 mm quartz or glass plates Clean Ethyl alcohol Distilled water 2.5 % solution Decon 90 Distilled water Distilled water Adhesive 157 μ 898 μ 1586 μ

P.S.Flower RAL PPD, CMS Meeting CERN, 1st. Feb Calculation of transmission Use different thicknesses of adhesive Eliminate refractive index and glass absorption terms

P.S.Flower RAL PPD, CMS Meeting CERN, 1st. Feb Sample measurement Collimate beam Sample must be perpendicular to beam accurately positioned ±10 μ Reproducibly positioned λ 20 Dual beam spectrophotometer

P.S.Flower RAL PPD, CMS Meeting CERN, 1st. Feb Results

P.S.Flower RAL PPD, CMS Meeting CERN, 1st. Feb Absorption of DOW RTV3145 Comparison of results with published data, M.Montecchi RTV3145

P.S.Flower RAL PPD, CMS Meeting CERN, 1st. Feb γ Irradiation of samples Brunel 15 Gy/h 1.7 Ci 60 Co P Bonner MRC 3.16 kGy/h 2 off 2000Ci 60 Co

P.S.Flower RAL PPD, CMS Meeting CERN, 1st. Feb γ Irradiation, results 205 kGy in 64 hours, adhesive 1155 μ thick 205 kGy in 64 hours, adhesive 66 μ thick

P.S.Flower RAL PPD, CMS Meeting CERN, 1st. Feb Gluing procedure Fill syringe with RTV Dow 3145 Centrifuge for 1 min at app rpm, (2000 g) Dispense resin. Settings Gas 80 psi, Grey, taper tip nozzle, time 1.35 sec Press VPT on to crystal, allow meniscus to form. Hold in position for 2 hours EFD 1500XL Dispenser

P.S.Flower RAL PPD, CMS Meeting CERN, 1st. Feb Tests on resins 5 samples DOW RTV 3145, high viscosity Resin thickness ± mm Skew mean 3.9 m rad. One part resin, constant viscosity, long usable time 22 mm discs on 26 mm squares, cleaned 0.9mm microscope slides 4 samples DOW Sylgard, low viscosity Resin thickness ± mm Skew mean 0.7 m rad. Two part resin, variable viscosity, short usable time

P.S.Flower RAL PPD, CMS Meeting CERN, 1st. Feb Curing, Manufacturers Spec. Manufacturers spec Skin over time 50 min (25) Tack free time 1.5 hrs Cure, 0.5 mm 24 hours Cure 3.2 mm 72 hours Full cure 3.2 mm 7 days Cures by neutral alkoxy reaction with moisture in the air. Releases methanol on curing 98% Non volatile 50 % humidity at 23 ºC taken as normal At less than 30% humidity, curing slowed

P.S.Flower RAL PPD, CMS Meeting CERN, 1st. Feb Curing measurements Student, C Pattison, noticed adhesive in syringe picked up colour from rubber plunger This colour disappeared when adhesive dried

P.S.Flower RAL PPD, CMS Meeting CERN, 1st. Feb Drying tests Initially all thicknesses dry at same speed Curing is moisture diffusion process After 48 hours, when the glue has dried about 4 mm; 100 micron glue dries at about 1 mm/day 500 micron glue dries at about 1.4 mm/day

P.S.Flower RAL PPD, CMS Meeting CERN, 1st. Feb Handling Tests on Dow Corning RTV 3145 After 5 min no slip observed After 30 min 100 g supported After 35 min 200 g supported After 40 min 225 g broke free weight 32 mm dia glass bottle Glass plate

P.S.Flower RAL PPD, CMS Meeting CERN, 1st. Feb Unbonding Literature suggests acidulated dichloromethane dissolves RTV3145. Nitromorse paint stripper contains dichloromethane. Unstuck bottle, 24 hours after gluing with 20 hours soaking in nitromorse. RAL resin rotter is dichloromethane, phenol and formic acid.

P.S.Flower RAL PPD, CMS Meeting CERN, 1st. Feb Conclusion Dow Corning RTV3145 Refractive index UV Transmission Radiation darkening Radiation embrittlement Adhesive bonding Stresses on crystal Long term stability Bubbles Drying Ease of use Can be unbonded OK Not tested OK Not yet solved