1. AdV cryotrap: cryostat surface is partially exposed to the near mirror (input ~ end). Its seismic shaking is amplified by LN2 boiling. The rest of vacuum chamber walls could be baffled out

2. CRYOTRAPS INNER DIAMETER IS TO BE FIXED Present figure of trap inner diameter is 0.86m. It could be enlarged to reduce the view factor or equipped with (metallic) baffles; on the contrary it could be narrow (0.7m for instance) for easier mechanical design, reduced cost and LN2 consumption Step 1, today: calculation method assessment Step 2: level of bubbles induced seism shall be estimated and comapred to the allowed limit calculated above (also the ‘baffles’ could be shaken above the ‘normal ground level’) -

3. Related documents: A plot about the bubbling of the present small trap: https://workarea.ego-gw.it/ego2/virgo/advanced-virgo/vac/diffused-light-vs-cryotraps- 11feb2010/24753_bubbletest_level2.gif/ https://workarea.ego-gw.it/ego2/virgo/advanced-virgo/vac/diffused-light-vs-cryotraps- 11feb2010/24753_bubbletest_level2.gif/ Seism measurement: https://workarea.ego-gw.it/ego2/virgo/advanced-virgo/vac/diffused-light-vs-cryotraps-11feb2010/seism_LARGEmicroseism.png/ https://workarea.ego-gw.it/ego2/virgo/advanced-virgo/vac/diffused-light-vs-cryotraps-11feb2010/seism_LARGEmicroseism.png/ Last AdV cryotrap drawings: https://workarea.ego-gw.it/ego2/virgo/advanced-virgo/vac/diffused-light-vs-cryotraps-11feb2010/last- cryotrap-drawings/ https://workarea.ego-gw.it/ego2/virgo/advanced-virgo/vac/diffused-light-vs-cryotraps-11feb2010/last- cryotrap-drawings/ Baffles calculation by JYVinet: https://workarea.ego-gw.it/ego2/virgo/advanced-virgo/vac/diffused-light-vs-cryotraps-11feb2010/cryox.pdf/ https://workarea.ego-gw.it/ego2/virgo/advanced-virgo/vac/diffused-light-vs-cryotraps-11feb2010/cryox.pdf/ Coupling factor estimation K ~ 2E-25: https://workarea.ego-gw.it/ego2/virgo/advanced-virgo/vac/diffused-light-vs-cryotraps- 11feb2010/Kcalc.pdf/ https://workarea.ego-gw.it/ego2/virgo/advanced-virgo/vac/diffused-light-vs-cryotraps- 11feb2010/Kcalc.pdf/ Summary doc about backscattering upconverions by Irene: https://workarea.ego- gw.it/ego2/virgo/advanced-virgo/vac/diffused-light-vs-cryotraps-11feb2010/minidocIrene_AdV_CryoT_BSnoiseProjection.doc/ https://workarea.ego- gw.it/ego2/virgo/advanced-virgo/vac/diffused-light-vs-cryotraps-11feb2010/minidocIrene_AdV_CryoT_BSnoiseProjection.doc/ Tube shaking test by Stefano: https://workarea.ego-gw.it/ego2/virgo/advanced-virgo/vac/diffused-light-vs-cryotraps- 11feb2010/Braccini_DiffusedLight_12022008.ppt/ https://workarea.ego-gw.it/ego2/virgo/advanced-virgo/vac/diffused-light-vs-cryotraps- 11feb2010/Braccini_DiffusedLight_12022008.ppt/