KAGRA cryogenic payload kickoff meeting 15th of Novermber 2013 (Fri) 10:00-13:00 311, Second Research Complex, Kashiwa campus Attendees: Aso, Chen, Hirose, Ishizaki, Khalaidovski, Ohashi, Saito, Sakakibara, Sekiguchi, Suzuki, Takahashi, Tokoku, Yamamoto SeeVogh: Akutsu, DeSalvo, Hayama, Kimura, Koike, Ono, Uchiyama 1. "Reporters" are assigned. Since there are a lot of items, "Reporter" reports the progress status of a bunch of items. And they check whether the progress in on time. If there are some problems, we must discuss issues in this meeting. The "Reporters" are as follows; 1. Overall design - Schematic structure : Eiichi Hirose 2. Sapphire monolithic suspension : Khalaidovski Alesandr 3. Vertical spring (blade metal spring) : Hideharu Izhizaki 4. Material : Toshikazu Suzuki 5. Control : Dan Chen (6. Manufacture of 1st payload : Kazuhiro Yamamoto) (7. Manufacture of bottom filter : Ryutaro Takahashi) (8. Manufacture of sapphire mirror : Eiichi Hirose) An important message from Takanori (from the point of view of the simulation) If some parameters should be decided for experiments, let know him. He trys to fix those parameters at first. 2. Sapphire monolithic suspension 2-1. Motivation : Since the situation is not so clear, Eiichi and Sascha presents the status. Kazuhiro's most important mission on the next week is to summarize the schedule and budget based on their presentation and so on. He must also show the priority. In short, the schedule about this topic on the Microsoft Project should be revised. 2-2. Eiichi's presentation Eiichi explained the three tests for 3D design. (a)Strength test at KEK (b)Thermal resistance measurement at ICRR (c)Assembly test (if flatness of cut surface is lambda(630nm)/10 and roughness is 20nm, it is OK for any cases). Discussion and comments about these tests; (i)Strength test is at 77K, probably. It is OK for us (although thermal expansion below 77K is quite small) ? (ii)In the strength test, a sample is cooled rapidly. Can thermal stress itself destroy the sample ? -> If we find so at the first experiment, we must consider. (iii)Homework from Saito-san (for lunch time or before we go to bed ?): Simulation for residual stress near bonding during cooling. Residual stress appears near surface of sapphire (3 micro meter) during cooling. Can indium compensate it ? (iv)In usual case, "strength test" implies "tensile strength test". Shear stress test is not so easy. Although the shear strength can be derived from the tensile strength if we discuss material, maybe, the story is different in the case of bonding. Schedule proposed by Eiichi. Middle of February : Decision based on test (a) and (b) Test (c) must be after this decision. But, we are afraid that it takes long time. Mechanical dissipation measurement is not included in his schedule. End of March : Geometry of mirror cut (drilling) should be fixd. In any cases, Finite Element Analysis is necessary and improtant. Eiichi's idea : screw. In his idea, the suspension consists of a mirror, ear, connector (it is some kinds of nail head, but, its volume is much larger), rod. There is no srews between mirror and ear. The ear and a connector is combined by screws. The connector and rod are also. Sapphire screw itself can be manifactured (Kazuhiro's comment; a female screw was made by Shinkosha. They said that manifacture of a male screw is easier). Some suggestions and discussion for sapphire screw (a)Bending length is about 5cm. We take it into account in any cases. (Some parts under ear ?) (b)It is better for the connetction between rod and connector is not screw (thermal resistance) (Eiichi also mentioned so). (c)It is better for the screw between the ear and connector to have a head. (Items below this sentence are concerns and some of them are speculation) (d)Material of screw: Eiichi said that it is metal (Cu ?). Is difference of thermal expansion a problem ? (e)"Optical contact" could grow between the ear and connector. They can not be separated a few months later. (f)Is contact surface enough (Only area under the screw head is contacted) ? (g)Is it tightened by hand ? (h)If a screw stacks, it is terrible. 2-3. Sascha's presentation He emphasises that it takes long time to prepare (procurement) and check bonding, fibers, blades and so on. Hydro Catalysis Bonding is excellent, but it is a nightmare when fibers are broken. Alternative : (Weld or brazing) Indium. In the case which Sascha shows, indium do not support a mirror. It is just a connection between an ear and a nail head of a fiber. But if it can support a mirror, it is excellent. Anyway, it is worth to try the strength test proposed by Eiichi and we should investigate how the strength depends on the thickness. Crucial point of indium : Control of thickness. Since mechanical loss of indium is large, thickness should be as small as possible. A student who comes from Hannover (supported by ELiTES) will investigate it in Japan. 2-4. Forgotten item Sascha ordered sapphire samples for the thermal resistance test (they will be delivered on the middle of December), but only for Hydro Catalysis Bonding. We need other blocks for other bonding technique. Kazuhiro will summarize how many we must order after he consult Eiichi. The direction of crystal axis and polish quality must be consider. 3. Other discussion Saito-san and Ohashi-san said that a member of SEO must attend this meeting. We hope that the fast decision for the schedule or budget will be possible (sometime, this member could decide in this meeting, maybe). This member will be decided in the Excective Office meeting in the next Monday morning and be announced in chief meeting in the next Monday afternoon. Most important message from Ohashi-san In any case, we must make efforts to win the budget even if it is quite difficult. That is the motivation to summarize the reseach plan, schedule, priority and so on. Next meeting : We will have the meeting 13:00 on every Tuesday (in principle, this is face to face meeting although the teleconference in SeeVogh will be reserved). So, the next meeting is on 13:00 of the 19th of Nov. However, this meeting is only to report and check the progress. In the meeting on 26th of Nov., Kazuhiro shows the schedule for sapphire monolithic suspension and Ishizaki-san explains the schedule for the cryogenic vertical spring.