LAV damage and repair – M. Moulson (Frascati) – Photon Veto WG – CERN – 5 April 2011 Damage to A3 during transport 2 10 blocks were broken during transport due to low temperatures Minimum temperature on vessel 4 ∘ C at 09:20 on 02 Dec. Most broken blocks on layers 0 and 4 (most accessible) List of blocks broken reconfirmed during A3 repair

LAV damage and repair – M. Moulson (Frascati) – Photon Veto WG – CERN – 5 April 2011 Summary of A3 repair mission 3 20 SunTransport of spare blocks from Frascati by car 21 MonInitial setup ECN3 crane out of service 22 TueSetup under TCC8 crane Radioprotection incident 23 WedNo work – RP survey 24 ThuPerformed repairs on layers 0 & 1 25 FriRotate vessel Experiment with repairs on layers 3 & 4 Work Package Assessment: People: Franco Cassese (Naples) Matthew Moulson, Massimo Santoni, Tommaso Spadaro (Frascati) Tonio De Oliveira (CERN) Schedule:

LAV damage and repair – M. Moulson (Frascati) – Photon Veto WG – CERN – 5 April 2011 A3 repair procedure 4 General procedure: 1.Remove endcaps and rotate to vertical position, layer 0 up 2.Repair and test the 6 damaged blocks on layer 0 3.Move back to rotation stand and rotate into upside-down vertical position, layer 4 up 4.Repair and test the 4 damaged blocks on layers 3 & 4 5.Rotate vessel to horizontal position, replace endcaps and store Repair of blocks and bananas: 1.Loosen signal, HV, LED cables by cutting cable ties on grille 2.Lift out damaged banana and rest on platform supported on adjacent banana 3.Unsolder signal/HV connections for damaged block only 4.Replace damaged block with spare and resolder connections 5.Reinstall banana in vessel

LAV damage and repair – M. Moulson (Frascati) – Photon Veto WG – CERN – 5 April 2011 Plans for A3 repair 5

LAV damage and repair – M. Moulson (Frascati) – Photon Veto WG – CERN – 5 April 2011 TCC8 setup for repair of layers 0 & 1 6

LAV damage and repair – M. Moulson (Frascati) – Photon Veto WG – CERN – 5 April 2011 Blocks replaced, layers 0 & 1 7 Replaced by ME1640Replaced by ME1983Replaced by MD9878 Replaced by ME2446 Replaced by ME3360 Replaced by ME

LAV damage and repair – M. Moulson (Frascati) – Photon Veto WG – CERN – 5 April 2011 Static load testing for damaged blocks 8 How likely are damaged blocks to detach? 6 broken blocks removed from A3 4 intact blocks with bad tubes deliberately exposed to cold at Frascati Testing in progress ME blocks (84 kg) ME blocks (120 kg) Glue holds Glass breaks One reinforcement supports weight of block

LAV damage and repair – M. Moulson (Frascati) – Photon Veto WG – CERN – 5 April 2011 Scratched blocks, layers 0 & 1 9 Seen as dark splotch in Feb exam Not seen in Dec (probably overlooked) Removed for further investigation Glass scratched at base of reinforcement plate, probably during cleaning Scratch can evidently propagate as crack in glass! 1-7-0

LAV damage and repair – M. Moulson (Frascati) – Photon Veto WG – CERN – 5 April 2011 Scratched blocks, layers 0 & 1 10 ME3141 (0-6-0) Taken inside vessel Similar to ME3060 Also removed to get closer look Clear evidence of scratch at base of reinforcement propagating as crack

LAV damage and repair – M. Moulson (Frascati) – Photon Veto WG – CERN – 5 April 2011 Testing of scratched blocks 11 Now that we know what to look for, many more scratched blocks found 3 blocks analyzed at Frascati ME3060, ME3141 – type 11 from A3 ME1305 – type 15 from A5 ME1305 Vibration applied with load No crack propagation seen ME3060 Flaw not easily visible at start Becomes visible as load applied No hysteresis Two temperature cycles applied Two-corner break ME3141 Load applied for 10 days Two corner break (maybe temp?) All blocks gradually loaded to 7 bricks (84 kg)

LAV damage and repair – M. Moulson (Frascati) – Photon Veto WG – CERN – 5 April 2011 Other repairs, layers 0 & 1 12 Torn Tyvek replaced Blocks ME2157 (0-1-2), ME1862 (0-1-3) Creased Tyvek replaced Block ME3102 (0-7-0)* Oil drops from TCC8 crane Block ME2918 (0-4-2)* Punctum dolens ME2451 (1-6-3) broken during replacement of ME3060 (1-7-0)

LAV damage and repair – M. Moulson (Frascati) – Photon Veto WG – CERN – 5 April 2011 Setup for repair of layers 3 & 4 13 Original idea to repair without access to cables essentially impossible To finish repairs, it will be necessary to have access to area underneath blocks

LAV damage and repair – M. Moulson (Frascati) – Photon Veto WG – CERN – 5 April 2011 A3 repair: Lessons learned 14 Studies on broken and scratched blocks: Blocks are highly resistant to mechanical stress Reinforcements do provide extensive safety margin Scratches can cause cracks, esp. combined with thermal stresses Avoid scratching blocks during cleaning Layers 3 & 4: Need access to cables – impossible to carry out repairs otherwise ECN3 crane: Need remote control Need to fix oil drip problem Residual radiation protection concerns in TCC8/ECN3

LAV damage and repair – M. Moulson (Frascati) – Photon Veto WG – CERN – 5 April TCC8 ECN3 Transport to CERN Transport to Frascati Frascati 911 upstairs