AdV-VAC meeting 21Apr’09 Agenda 1) results from the reviews (A.Pasqualetti) 2) present wbs, present project planning, baseline design (A.Pasqualetti) 3) vacuum control system ( F.Cavalier) 4) general HW & SW coordination (F.Carbognani) 5) cryotraps (J.vandenBrand, M.Doets) 6) liquid nitrogen supply (G.Gemme/A.Chincarini) 7) Diffused light issue (C.Bradaschia) 8) central area systems: scrolls, ions,... (A.Pasqualetti) 9) towers and UHV air upgrade (P.Mugnier) 10) towers displacement (F.Richard/R.Cosci/A.Paoli)

Internal Review 04March’09 The Internal committee (B. Canuel, V. Fafone, M. Punturo, F. Ricci (chair)) reviewed the ‘cryotrap’ motivations and design. Related documents available here: A ‘design’ document was prepared by the contributors, to be issued in the definitive format In conclusion, the reviewers express their appreciation for the high quality work of the Adv VAC team and strongly support the small trap proposed solution, seen the advantage in terms of cost and time installation. The review committee conclude by listing what it is still missing: ‐ Safety and related equipment are not yet considered. ‐ More details are needed for the nitrogen line transfer design and the automatic fill up system. ‐ The Advanced VIRGO plan should be updated by including the small cryotrap solution.

External Commitee Review 24March’09 We presented at ERC the task list, the WBS, the cryotraps as the main technical change. Results = no objections has been raised on the design. There are some questions on specific points. Answers are to be discussed with ERC the next 27April oAlthough it was reported that a bake-out system is present the costs and manpower issues of a potential tube bake-out need to be studied and reported. Answer:Main figures about tubes bake-out have not been presented due to the short time but are quoted in the slides: based on past experience (tubes have been already baked in 2000, 2001 reaching the goal of 10^-9 mbar) the estimated cost is 300keur + taxes (equipment rent, consumables) and the required manpower during the procedure is 6 FTE for 2 months. Less manpower is required for the baking preparation phase, to be started some months in advance. A more detailed plan of the baking procedure can be shown at the ERC final review.

oIf a proper bake of the towers is not acceptable, couldn’t a gentle vacuum bake to 50 or 60°C might be considered to speed up water desorption. Answer‘mild bake’ was indeed considered during the design phase of Virgo and experimented on large scale prototypes: unfortunately it requires very long times (>month) to get results comparable with the 150C baking. Furthermore the warm-up of the tower experimental equipment may have unpredictable effects on suspension and payload tunings. oSome technical remark/question: It was reported that the black body radiation of the environment to the cryo traps causes major heat losses (or rather gain) and causes high LN2 consumption. Would gold coating (having a high reflectivity at thermal wavelengths) of the cryotrap surface reduce this and still preserve stickiness for contaminants and water? Answer:We are currently optimizing the cryotrap design, evaluating different options also in terms of LN2 consumption. About the gold coating, its superior performance would be spoiled by the water deposit covering the trap surface ; (and also the trap ‘concave’ geometry doesn’t enhance the gain in reflectivity). Furthermore we should qualify the specific coating process for not including contaminants in the film (risk of mirrors pollution). In conclusion, gold coating is one of the design options that we will evaluate in the design finalization, comparing costs, production times, risks and performances.

oHow much do LN2 costs contribute to running budget? Answer:The estimated running cost is around 100keur per year, depending on the final rate of the LN2 supply contract. oLab commitments to ensure progress are still not clear to us. MOUs are good, but will they be sufficient? Answer:Work to formalize labs commitment is in progress at management level. It is worth to point out that interested labs started effectively their commitment, being fully involved in the present design activity. oA process was described for outgassing UHV components consisting of warming (60°C) under a flux of dry nitrogen. Would it be applicable to towers? Answer:This is the process that has been proposed for traps regeneration, to speed up the removal of the relatively ‘thick’ water film frozen on trap surfaces. Condensation water binding to surfaces is much weaker than that of water molecule layers addressed by bake-out procedure. If applied on towers for degassing purposes, the effect would be not better than the ‘mild bake’ described above, with severe concerns about de-tuning of experimental equipment.

Cryotraps : what is the highest possible temperature for this kind of device (keeping some efficiency, for residual gas pressure dominated by water) ? Wouldn’t it be possible to install some cryogenerator near traps (higher temperature than LN2) to avoid LN2 manipulation and storage? Answer: The ‘cryocooler’ option is being considered since the start of the cryotraps design. We have considered different types of cryocoolers, according the experience achieved in Virgo labs and related R&D facilities …. …. …. … it does not give clear and significant advantages: manpower, maintenance needs and running costs during the operating phase are comparable with the classical solution employing ‘LN2 dewar’. On the other hand the cryocooler option requires larger initial investments and involves risks associated to a not well-proven technique. It is not the ‘baseline solution’, and requires further analysis. It could be implemented in a second time without significant additional expenses (the same transfer lines will be used, while the LN2 dewars shall be sent back to the rent company).

Work Breakdown and Project Plan The WBS is written on a XLS file, containing the project informations, periodically updated and ‘automatically’ translated in the AdV plan (time schedule, manpower, cost): AdV coordinators ask for a critical review in the next days : 1) It is to be Checked for mistakes, for instance Is the foreseen manpower for cryotrap ok? Timing for the LN2 installation: to be ready in 2010? 2) Start cross-checking with the other subsystems the Interference during the asssmbly phase, for instance Area preparation for the LN2 dewars (IME) Superattenuator installation can be parallelized with ‘links’ installation? (SAT)

WBS last update: cost quality

Enlarged Link task We are looking for collaboration about the task ‘Enlarged Links’ - Design, procurement, installation of 6 enlarged links - A brief description of the work is available here:

Baseline design ‘AdV baseline design’ document to be prepared for 8 May, to be submitted to Virgo collaboration, to be sent to ERC the 15May proposed structure for the document (G.Losurdo): - Introductory chapter: design summary, reference sensitivity - Updated science case (using the new curve) - SS reference design. The average length of the chapters should not exceed 7-8 pages. Some flexibility will be required. Some crucial SS, like OSD, might require some more pages. Others, less defined at this stage, could be shorter. The SS chapters should describe the reference design: - Alternative options should not be described here (sometimes it can be appropriate mentioning them with reference to specific docs) - R&D results should not be described - Equations and plots must be inserted when absolutely necessary to justify a design choice or describe relevant specs or expected performance.

For each task: Verify and check the wbs and planning documents Contribute to the ‘baseline design doc’. A first version shall be prepared starting from the existing documents (‘preliminary design’and the various ‘reviews documents’ ) and circulated near the end of next week for comments and corrections Prepare a design meeting on Cryotrap during May Summary of next activity

Some points about Central area vacuum system Two configurations to be studied for the ‘baseline design’: 3 or 5 towers joined by links with 800mm free aperture : no valves?

Optical design baseline options: we have to exploit the vacuum system changes and tower accessibility in particular: procedure of opening and operating inside towers Other main figures : Residual pressure H2, H2O ~10 Pumping systems: ‘scroll‘ always ON but displaced in a suitable room, 4 large Ion pumps on links (IB, DT, MC. No turbos on towers lower parts) Air = double orings on towers bottom flanges (or metal sealings) + metal on bench towers. After AdV commissioning, if needed Perhaps: small traps on bench towers links, depending on optical design Some points about Central area vacuum system