件名 : RE: SCT GeoModel[Tue, 12 Sep 2006 10:02:54 +0100] 送信者 : Tricoli, A \(Alessandro\) 宛先 : Pat Ward >>> Dear Pat, Stephen and Taka, I went through Pat's useful comparisons between the current simulation and my recent model for the Barrel SCT. A general comment is that I agree with Pat that changes should be applied only if necessary and should be first agreed by all of us. As you will read below in my comments which are taged with "-.A.T.:", most of the differences between the current mass values and the ones in my model are either due to items not included in the simulation yet or to a reshuffle of same items in different simplified components. I think that most of the differences in mass highlighted by Pat have good explanations. Regarding volumes, I think we should try to be as close as possible to the drawing dimensions, but I also think that the final decision must be taken by Pat taking into account volume clashes in the simulation. A few mm shifts are reasonable I would think. Having said that, the volumes I have proposed so far are just suggestions which must be revised by Pat in the light of geometry restrictions. Further comments are indented below. Notes for discussion on new barrel services geometry. CPW 18/8/06 ==================================================== Dogleg ====== Current Alessandro ------- ---------- Thickness/mm (r) 1.0 0.34 Length/mm (phi) 36.0 76.8 Width/mm (z) 30.0 26.0 Volume/cc 1.08 0.78 Mass/g 6.9552 5.71 Density/(g/cc) 6.44 8.41 * Propose to keep current dimensions and position but update mass and composition. Length cannot be extended without overlapping cooling pipe. -A.T.: the thickness value I chose (0.34mm) includes only the power tape layers, does not take into account the opto package, fibres etc. for which I could not find dimension information. So I am happy to have it extendd to 1 mm in r. The length in phi in the current simulation seems rather short to me but this value has probably been chosen as the maximum allowed to avoid clashes. So that's fine. * Why is new mass lower? This is 'dogleg+top bracket' option. -A.T.: the lower mass in my computation is due to the placement of the "module clips" and "dogleg clips" into the "cooling block" model, the placement of the "lmt i/f board" and "redundancy arms" in the "straight harness" model and the addition of the opto-fibres in the "dogleg", not present before. Cooling Block ============= Current Alessandro ------- ---------- Thickness/mm (r) 1.5 5.0 Width/mm (phi) 8.0 8.0 Length/mm (z) 62.0 62.0 Volume/cc 0.74 2.48 Mass/g 2.418 3.62 Density/(g/cc) 3.25 1.46 * Suspect mass difference because Alessandro has included solder, clips, etc. and current value only include block (current material = Al). Is this so? -A.T.: Yes, I think so too. I cannot find any Taka's spread sheet with the list of items that enter the cooling block, but from the composition (only Al) and the weight it seems so. In fact in my calculation, the cooling block itself weighs 2.24g the rest is due to solder (most of the wieght), shunt shield, screws and clips. * Propose to keep current dimensions and position but update mass and composition. There is no room to increase thickness. -A.T.: the thickness value I quote is what I found in drawings, but I guess in the simulation has been reduced to avoid clashes. So that's fine. Cooling Pipe ============ Current Alessandro Drawing ------- ---------- ------- Radius/mm 2.0 1571.76 Length/mm 2.1 1471.6 Radial position/mm (3) 304.8 306.9 307.1/309.7 (4) 375.7 377.9 378.0/380.6 (5) 447.4 449.9 449.7/452.4 (6) 518.1 520.9 520.4/523.1 * Current positions (estimated from entry points of particles) are 2-3mm inside values suggested by Alessandro and drawings. Propose to leave them there - moving likely to cause huge problems. -A.T.: I don't understand the values in the first two rows under "current" and the "radius/mm" value under "Alessandro". (?) * Length will be updated to 'whatever is convenient'. I think the radius can be increased, but am not sure it is worth it. Mass and composition will be updated. Bottom Bracket ============== Current Alessandro ------- ---------- Thickness/mm (r) 4.0 3.2 Width/mm (phi) 8.0 7.5 Length/mm (z) 51.0 54.0 Volume/cc 1.63 1.30 Mass/g 4.94496 2.68 Density/(g/cc) 3.03 2.07 * Why the mass difference? Think Taka includes an 'interface PCB' and Alessandro does not (I think this is in Alessandro's harness). This needs checking. -A.T.: it is true that the "interface PCB" is placed in the harness in my model, but this accounts for only 1.43g extra, which added to 2.68 g gives 4.11 g. That means that 0.84g are missing. I notice that in Taka's excel sheet in http://atlas.kek.jp/si-soft/geometry.html the "bottom bracket" is actually 4.36g. The difference wrt my estimate is only 0.25 g in this case. Going through Taka's calculations I notice that he used both THIRD MOUNTING POINT UPPER and LOWER, whereas I only used an average between the two, since (if I understand correctly) either the lower or upper third mounting point is on each bracket assembly, depending whether the module is in the upper or lower position. Furthermore, I have one more screw (M1x4=0.027g) than Taka. In conlusion the differences between my description and taka's description are minor, whereas I do not know where the current value in the simulation (4.945g) comes from. Any idea Pat? * Propose to keep current dimensions and position, update mass and composition. -A.T.: that's fine with me. Harness (Power Tapes) ===================== Contained within a volume: Current Alessandro ------- ---------- Thickness/mm (r) 1.221 1.97 Width/mm (phi) 21.0 24.66 Length/mm (z) 1571.76 1423.1 Mass/g 33.5025 93.4 * Within this volume are 2*6 tapes (each thickness 1.221/6mm) stacked in r, running from the interlink to each dogleg. Propose to keep this structure, but increase tape thickness (to ?) and reduce length to make end at end of cylinder. -A.T.: I agree. The thickness is difficult to model since on top of the tapes there are the fibres and the clamps. All these items have different volumes along z. Any value of thicknes between 1.22 and 2 mm would be fine as long as they don't cause any clash with other volumes. * Why now so much more mass? Seems to be because the current 'power tapes' include only power tapes, whereas Alessandro's harness includes fibres, interface PCB, connectors as well. The power tape component of this is 33.34g which is similar to current power tapes - is the rest really so much more? I think some of the stuff Alessandro has included in the harness has probably been included by Taka in the dogleg or brackets - they should check, if they haven't already done so. In which case, do we want to move it into the harness, smeared out along z, or keep it in the doglegs and bracket, concentrated in z? -A.T.: Yes, most of the difference between the current value and my value for the harness is due to the absence in the current simulation of the "permenent clamps", 2.1g each (25.82 g per row) the interconnects and the fibres. Furthermore, as already mentioned, some of the connectors and the i/f PCB are placed in the harness in my model, whereas are in the dogleg in the current simulation. So the mass difference is explained. I have no strong arguments to keep the i/f PCB and the connectors on the harness, but I don't see any big impact on the simulation either if we move them into the dogleg: in fact in the simulation the straight part of the harness is split into 12 subsections along z (as you can see in the "HarnesSplit" sheet) so that the masses of these components are smeared only over a small area. However I am happy to follow Taka's approach if you think it is more appropriate. * Should the interlink volume be at |z| = 765, rather than current position just inside thermal shield? And where should thermal shield be? -A.T.: Stephen and I just started looking into the interlinks and thermal enclosure modeling, so we will get back to you on this soon. Cylinder, Flange, Clamp ======================= * Propose to change geometry here to match Alessandro's dimensions, layout and materials, except that the clamp will start outside the auxilliary layer, i.e. there will be a 2mm gap between the harness and the clamp (in r). -A.T.: OK. Cooling Inlet/OutLets and U-bends ================================= * Propose to implement a simplified model of these in the first instance: a tube with r_min = r_max of clamp r_max = r_min + 10 mm extending in z from the end of the modules (z = 747mm) to the end of the barrel (z = 765 mm). -A.T.: OK. At some future date, it would then be possible to split this tube into segments with alternate segments filled with different materials to simulate the in/outlets separately from the U-bends. And even to put smaller volumes inside the segments if necessary. But the overall envelope would be the same at each end, and the cooling pipe just runs between these envelopes. -A.T. I think it is a good strategy. Thank you, Alessandro