Q&A Smalltraps RReview 19Feb2014

From C. Michel: Congratulations for the Vac Team: the project is mature and ready for the manufacturing step. Nevertheless I have some minor questions. 1)On the §4 Vacuum performances you compare efficiency of different solutions. I presume that value for the VIRGO+ cryotrap is a calculation. During VIRGO + have you been able to measure differential pressures? This will allow to validate your calculation. Yes, the data presented in §4 is a calculation; during V+ we monitored RGA signals (in particular we had an RGA at the trap outlet) verifying that contamination level was not increasing on the mirror tower side. The level of contamination in bench tower was almost 2 orders of magnitude higher than mirror towers. It is expected to be similar also for AdV. 2)Regeneration: what is planned: - natural heating or artificial heat? - gas exhaust valve? - pumping duration with the portable high vacuum pumping group? Natural heating is inherent in the first part (typically we don’t refill the trap when a regeneration is programmed, starting before the maintenance break) then we shall use electrical heaters to speed up the process. The GN2 goes out via its normal piping. Pumping is active through the whole process. 3) Does the 180 k€ cost estimation respect the foreseen budget? We got recently estimation for keur, the foreseen budget is slightly low =120keur. Design has been complicated using aluminum and multiple supporting structure. We have not updated the specific budget line yet because we saved budget in other items (SR tower rings, Enlarged links) that over compensate this difference.

4) The call for tender will close end of March. I think 2 weeks are necessary to place the order. So the beginning of the manufacturing will be mid-april. If 5 months are planned for the first small cryotrap delivery, installation can not started in August. Moreover 3 weeks are planned for the leak test and the schedule occurs during summer vacations, there is a risk of delay. True. August was from an earlier version of the document, we accumulated about one month of delay in discussing and refining the design (supporting structure in particular). By the way Sept is still a quite conservative schedule with respect to the general AdV plan, where smalltraps are needed to inject the beam on DT, foreseen for Apr ) Call for tender: - is it a public call for tender or only some "pre-selected" companies will be consulted (as I can imagine)? - offer selection: only price will be taken into account, nothing regarding technical considerations? Public tender is required for higher expenses; in our case we will follow the ‘procedura negoziata’, inviting some companies (minimum 3) with acknowledged experience in fabrication of uhv chambers and cryostats. In this case a ‘minimum’ technical quality is implicit. Pros and cons of adding a score for technical quality can be discussed at the review.

From A.Rocchi: I agree with Christophe in saying that the project is ready to go ahead and that the PO can be placed. I also have a few questions: 1) "Smalltraps description and technical specifications" document - section 4: it is said that the certificate of chemical analysis of the materials must be provided at the delivery. Wouldn't it be safer to get it as soon as the company purchases the material? It would avoid having bad surprises after the traps are delivered. Normally this certificate accompanies the raw material. We could ask for a ‘hold point’: once purchased the raw material, before going ahead with the production, the contractor will present the certification to ego. 2) "Smalltraps description and technical specifications" document - section 11: leak tests will be performed before and after the cooldown, why not during this phase? There is always the possibility of holes opening while the trap is cold and sealing when it is warm... Right, your recommendation is what we intended to write. We could rephrase in this way: “ He leak detection test will be repeated when cryostat has reached the cold status ‘’

3) "IB-DT Smalltraps for AdV: technical overview" document - section 3: it is said that the traps will be refilled twice per week and, in section 12, that the ITF break will last one hour. I wonder if the impact on the AdV duty cycle has been evaluated. In fact, if I remember well, during the Virgo+ operation, each time the trap was refilled it also took some time for it to "calm down". I cannot recall if any effect on the Virgo+ sensitivity was ever evidenced, but we must not forget that AdV will be ten times more sensitive (to noise sources also, unfortunately...). This said, I think that the "future improvement" described in section 12 (continuous LN2 supply), should be upgraded to a baseline design. We also think that best refill procedure is in ‘continuous mode’ for final AdV. In V+ ‘the bubbling noise’ showed some coherence around Hz and took some hours to disappear from sensitivity. The commissioning phase ( 2015) should not be much disturbed, while for the developed AdV we could have the LN2 lines and continuous operation (within end 2015 seems be feasible). Also, we have saved some budget from the tube cryotrap lines that could be used for this item

PR: also from my side there are no major remarks to the smalltraps design, which is quite mature. A few minor remarks: -I agree that having a leak test while the cryotraps are being cooled down could be important. Indeed, we have had experience in the past of leaks appearing only at a certain temperature, and any leak could be very dnagerous in our configuration. We agree (it occurred also on the first tube-cryotrap). It is infact foreseen in the document but not well written, we have rephrased the text in the tender letter. -Also the use of LN2 coming from the tube cryotraps to fill continuosly the small ones seems a good idea, that could simplify operation. It would be interesting to know how much it is realistic to implement this with the current AdV planning. The LN2 transfer line could be achieved in 6-7 months : for instance the tender of the central lines (just closed) took from mid Dec(= start of the tender) to mid May(=LN2 lines should be ready). Company needs about 2-3 months from contract signature to prepare materials, and shall take about 1-2 weeks working inside the central building. Another parallel activity is to prepare the automatic refill equipment, using a PID driver (integrated in PLC)+ a cryogenic needle valve, similarly to what used for the large cryotraps. This activity could be done along with the ‘smalltrap’ control rack preparation (started), to be completed within Then some weeks of pre-comissioning on the first installed smalltrap to tune the loops parameters will be needed. Manpower seems available (Genova, EGO, some from Nikhef). Task could be finished by mid 2015, tbc. In this case it should be wise to focus directly on this solution

- I see that any precaution has been taken to avoid acoustic or seismic effects from boiling LN2: is there yet any quantitative evaluation coming from measurements on the large cryotraps? First tests on large cryotraps were done at Nikhef last year. Boiling noise was not noticed, at least at ‘significant’ level. These results will be documented soon. -On the the call for tender: I think it is important to include always in the tender that the firm will be selected according first to a technical evaluation and then to proposed cost. You know that for the LN2 lines this prevented us to be forced to choose a solution more economical, but not technically sound. Normally if an offer is not respecting the minimum required technical aspects can be discarded. But also can be wise to include a formula to reward the technical quality, the preferred formula can be discussed at the review

B.M.: The IB-DT smalltraps looks well studied and documented. I only have a few questions 1. Could we install baffles on both sides of the smalltraps? Yes, we have foreseen a dedicated slot on both sides of smalltrap 2. About the possible permanent supply LN2 line: what would be the cost (money/manpower/planning)? Do you see any drawback? Economic cost could be <80 keur + taxes (in case of completely independent lines; about half if derived from existing lines of large cryotraps. The large cryotraps lines costed about 55keur + taxes). Manpower could be from Genova/EGO, as for the other lines. Considering the past experience, we could have the lines early Do we evaluate the need for regeneration of a trap just on LN2 consumption? What is our planning freedom for the regeneration process? (i.e. could we wait 3 months if we are starting a run for instance) In our case the main drawback should be the extra consumption of LN2, that is anyway tolerable at least for some time, so we should not be forced to regenerate stopping ITF when not convenient for AdV. A further drawback, even if not expected, could be extra boiling noise due to the larger heat input

4. Do we have some hard wired logic to detect a warm up of the trap and close the valves in case of unforeseen failure in the LN2 supply? Yes, it is a ‘standard’ feature on all cryotraps 5. I understand that the large viewport on the valves are not part of this review. However, could you say a few words about the associated safety? These are large pieces of glass, which will be moved, exposed to low temperature with people working just behind. We asked for expertize about this viewports. Calculations were done, for vacuum and thermal loads (also bakeout, for FS ), in order to verify the glass thickness proposed to VAT for the valve design. Concerning the ‘movement’ of the gate, and possibly associated shocks, a test + calculation was done for other viewport configurations (the standard ones), and shall be repeated for this case.

Characteristic frequencies update 14Feb config RR (lower rods 15deg) da 1.5Hz 5N/mm, 4Hz 500N/mm, 20Hz blocked Config. 2 with lower rods = 20deg: spring 500 N/mm gives first mode (beam direction) 5.2 Hz spring 1000 N/mm gives first mode (beam direction) di 7.1 Hz (note: upper rods w/t rubber, lower rod with spring in neutral position)