From Filippo.Resnati@cern.ch Wed Sep 16 14:29:31 2020 Date: Wed, 16 Sep 2020 18:29:17 +0000 From: Filippo Resnati To: Sowjanya Gollapinni , "maneira@lip.pt" Cc: Stephen Henry Pordes , Igor Kreslo , Theresa Marie Shaw , "clk@fnal.gov" , Nicola Mcconkey , Steve Herbert Kettell , Eric James Subject: Ionization Laser System Initial Design Review: Questions Dear Sowjanya and José, thank you and the other participants for today's presentations. Below you can find the issues that have been raised in the executive session. Some of them can be addressed for the Q&A session of tomorrow. It is recognised that some others need more time. Questions: 1) Is the mechanical support and the vibration isolation of the laser box sufficient? What are the relevant issues driving this kind of design decision? 2) What engineering analysis is envisaged going forwards to ensure that the evacuated tube can withstand all of the different cryogenic conditions during cool-down? 3) Is the connection between the top and bottom sections of the periscope adjustable / re-alignable after installation? 4) With such a long structure inserted into the cryostat with supported only at the top, is the periscope rigid enough given effects such as the temperature gradient and liquid argon movement?? What kind of scenarios are taken into account for the mechanical analysis of the stability of the system? 5) Welding the view-ports will introduce stress to the windows as well (compared to the standard gasket and bolts solution). welded view-ports cannot be replaced if they break. Typically view-ports developed for vacuum applications do not withstand much positive pressure. Are these considerations taken into account in the design? Should these view-ports be custom made? What is the advantage of welding the view-ports directly to the main flange? 6) What's the plan going forward for optimising the end-wall system? 7) Was the FEA for the field distortion done with the bottom section of the periscope made out of PEEK? 8) Considering that the ceramic insulation need to support more than 130 kg with a long lever arm, what mechanical analysis has been performed to show that it has adequate strength? 9) Is there adequate protection in place to prevent injuries from moving parts of the system? 10) Isn't 60 mJ/pulse direct on PiN too much? Any tests made or planned on this? 11) Are there documented details on the PMT / Camera system? They should be included in the system diagrams. 12) Has the MicroBooNE experience been used to estimate the amount of work involved in the project and compared it to the resources presently available? Are there particular aspects of the project that are of concern? Thank you. Best regards, Filippo (on behalf of the Review Committee) ----------------------------------------------------------------------- A couple of quick follow up questions just so we understand what is being asked: -- On Q6, what aspect of end-wall design optimization are you referring to? Are you referring to optimization of positions mentioned in page 29 of Jose's talk? We can provide a general answer but if there is something specific, please let us know. -- On Q10, is that about the photo diode in the laser box? or are you referring to the LBLS pin diode system? We think it is latter, but would like to confirm.  ----------------------------------------------------------------------------- Dear Sowjanya, the question 6 is quite general and broad, in fact. Sure it relates to what is mentioned on slide 29, but also to other aspects of the periscope that are not yet 100% defined, like the offset of the eccentric mechanics, the delicate beam alignment system, the second solution for the electrical break, ... Question 10 regards the LBLS pin diode system.