Trident separator window investigation

1. Trident separator window investigation Matthew Brock (Oxford) 16th October 2012

2. Context The picture to the right from Roger Forty’s presentation at Davos on the 3rd September shows a concept for Trident requiring a window separating the gases. Two window concepts were proposed for investigation by finite element analysis • Glass of varying thickness • Polymer, possibly Mylar (polyester), possibly a film xd x0

3. Geometry

4. Loading • Sheet is split into 20 horizontal strips 250mm high • Differential pressure applied from 1.74 mbar at the top to -1.74 mbar at the bottom calculated assuming a density of 11.21 for C4F10 and 3.72 for CF4 • Fixed constraint around the external edges and at the beam pipe • Gravity also applied

5. 6 mm thick glass stress Glass failure stress of 30-90 MPa depending on grade so 6mm gives a reasonable margin.

6. 6 mm thick glass Displacement

7. Variation with glass thickness The model becomes less accurate with reduced thickness. Some random errors occur due to modelling problems. A single node error for 5mm and 8mm thickness means the peak stress is estimated.

8. Comparison of glass with polymers • Displacement is much larger for polymers due to the lower Youngs modulus • FE model becomes unstable at thicknesses lower than 4mm but displacements would be very large at this point. • Mylar film is available in 12-300 micron thicknesses but defection would be beyond the linear range. • The materials chosen were those in the standard materials database. Polyester is not in the database however the other polymers give an indication of the displacement.

9. Discussion points • The modelling shows some quite high displacements and it may be worth making some physical models to verify this. • What deflection of the window would be acceptable? • Should we be carrying out some optical modelling? • If we are going to consider a polymer which transparent material would best survive the environment?