Sounds good to me. Just one more fact... I have measured the BCAL wedge that is here at jlab. It measures approx. 1.21 mm per layer. For the matrix height on the current dwg. (22.18cm) we would have 183 layers. George, would the 1st layer of lead against the aluminum plate be swaged? It appears the BCAL sample here at JLAB has a swaged piece and the hollows just fill with epoxy. There is 1 fiber used to orient the 1st lead layer. Is that the plan? Thanks, Tim George Lolos wrote: Hi Elton: Your proposal makes a lot of sense. Zisis will be back at the office on August 28th and given the amount of work he had put into writing a BCAL dimensions document and the calculations of radiation length, I suggest that it's best we wait until he can participate and we do the final exercise only once but with all the facts in front of us. Cheers, GeorgeElton Smith <elton@jlab.org> 08/12/08 11:13 AM >>>HI George, As we move into construction, we will need to firm up all the numbers that define the Bcal geometry, some critical to physics, others simply for proper integration into the overall detector. But all of these MUST be incorporated into the drawing package. This will be the definitive source for all dimensions. It is the only way we will be able to make sure that all work, integration, documentation, definitions for interfaces, etc are consistent. Therefore, I urge you, Zisis and everyone else to review what is presently in the drawings and send me and Tim comments and corrections. Again, you can find the drawings at http://www.jlab.org/Hall-D/reviews/Lehman-2008/Pre-Brief_Material-HallD/CD3_DRAWING_PACKAGE/01.DETECTOR/07.barrel.calorimeter.pdf These were presented at the Bcal review as well as Lehman, etc. They repreent the present "nominal" plan, but again updates and changes are welcome as we add more details to the 3-D model. It is not practical to keep updating the drawings daily, but they do need to be brought up-to-date for various milestones, such as the Bcal review. Changes should go through both Tim and I with Elke in the loop. I suggest we spend a little time at the next working group meeting (Monday) to review the procedure for this. Once we all agree on the dimensions, we can use the drawings for reference, without having to rely on our aging gray cells. Thanks, Elton. Elton Smith Jefferson Lab MS 12H5 12000 Jefferson Ave Suite # 16 Newport News, VA 23606 elton@jlab.org (757) 269-7625 (757) 269-6331 fax On Tue, 12 Aug 2008, George Lolos wrote:Hi Tim: The number of 65 cm to 90 cm was originally meant to accommodate the matrix only, resulting in the original 25 cm of matrix thickness.Thiswas later reduced to 23.5 cm plus the 2.54 cm of Al plate bringing the total thickness to 26 cm. I never recall a different thickness andallour plans were for the 200 layers, including the construction reports and calculations for materials. I have stated in writing that gluing the innermost Al plate on tofibersis not a good idea. Instead, I insisted that the Al plate should be glued on the last Pb sheet because the bond with the fibers will notbeas strong and shear stresses can shift the fibers. The innermost Al plate should be glued with industrial epoxy (the same we use to gluethebase Pb sheet on the base Al plate) on the last Pb sheet. Construction-wise, whether we go for 188 layers or 200 layers has a minimal effect on construction times so there's no issue on this. The difference is approximately one radiation length and we had already reduced it from the early design of 25 cm of matrix. Perhaps someone can simulate the new thickness and if it has no effect on physics,let'sgo with 188 layers. GeorgeTim Whitlatch <whitey@jlab.org> 08/12/08 6:33 AM >>>Good morning all, Here is my take. Addressing the issue of the number of layers............ We are currently using 22.18 cm of matrix in each wedge. We have an8mmal plate on the inside to take the place of 1 layer of lead (radiation length)(see drawing D00000-07-1008 from the link Elton supplied) Wealsohave a 1.25" thick aluminum plate on the outside for structural and mechanical reasons. This increased from 1", but only towards theoutsidethus not changing the matrix qty. Looking back at documents as farbackas 2004, the OD is 90cm and ID is 65cm. Subtracting the 2.54cm for the outer aluminum plate, we get 22.46 cm of matrix. I do not recall atimesince I have been involved that we had 23.5 cm of matrix. Removing 1 layer of lead on the inside for the 8mm aluminum plate gives us 22.41 cm. Another 1.5 mm removed because the outer al plate is flat yields 22.26 (very close to our current 22.18 cm). So 221.8 mm divided by1.18pitch yields 187.9 layers. Let's make it 188. I am in agreement with George that consistency of the swaging is whatisimportant here. If there is documented problems with the alloyed versions of the lead, we should go with the 99.98% pure. Does this increase the cost significantly? Cheers, Tim George Lolos wrote:Hi Elton: I will address comments to your comments on my comments, below :-) On 11-Aug-08, at 3:14 PM, Elton Smith wrote:On Mon, 11 Aug 2008, George Lolos wrote:Hi Elton and Elke: I went over the draft for the lead and I have some comments: 1. The purity, as I wrote last Friday, is 99.98% (known as "purelead"and "non-Cu alloyed")I will add this to the specs.2. The amount of lead required should be based on 200 layers per module NOT 187. The 200 layers will give us the ~23.5 cm of matrix. Therefore, the no-waste number is 9600 strips. This is the "base number" and the total mass of lead should be based on that number. Also, the minimum width we start with for the base layers is 13 cmnot12cm. After machining the base width is 11.8 cm.The current drawings for the Bcal call for 187 layers of lead. Seep.8 ofhttp://www.jlab.org/Hall-D/reviews/Lehman-2008/Pre-Brief_Material-HallD/CD3_DRAWING_PACKAGE/01.DETECTOR/07.barrel.calorimeter.pdfIf this is not correct, we need to update the drawings accordingly.Frankly, why the number of 187 layers has persisted so long, whileitis not right for the final module of 23.5 cm, I don't know. I have corrected it in the various submissions I have made but it survives unscathed. It should be corrected and the rough calculation here proves I am right :-) 23.5 cm matrix thickness/ 1.18 mm/layer = 199 and with the leadbeingthe topmost sheet makes it 200. Whether is a little over or under 200, 187 it's not.So, I would have 9600 sheets x 0.05 cm x 13 cm x 400 cm x 11.2gr/cm3 =28 metric tons of lead (no waste). Please check my calculationsagainbut I believe they are correct.Note that this number needs to be very precise, but for the sake of consistenty, we should use the same number for the density of Pb. From the PDG the density is 11.35 g/cm3. Does the "purity" result in adifferentnumber?You're correct. The density of lead is 11.35 g/cm3, I used thewrongnumber. This is the density of lead of purity we want.While the Modules 1 and 2 were built with lead we received inrolls,the latest shipment of lead was in sheets and Paul See from Vulcantoldmethat most likely the shipment will also be in sheets, no rolls.Inorder to reduce waste as much as possible, we should specifydesiredwidth for either rolls or sheets and desired length per sheet forthelatter. So, for length, we require an integer multiple of 400 cmandfor width an integer multiple of 13 cm as optimum.The request for rolls comes from your initial "specification"document.Please take a look at the document and make corrections to it sothatweput down what we want to request from the vendor. For example, the original request indicates that standard rolls of 20" would suitourpurpose. This seems to be a tad short, so do we ask for 13x4 = 52cm,orhow much extra is needed to account for cutting?The reason I was quoting a "standard" roll is because I was led to believe that that was indeed the case. Of course, with the huge amount we're going to order, "standard" is what we define. One more variable in the width definition is that with the step pyramiddesign,we have more flexibility in cutting strips off the roll or sheet. So, even with 20" (50.8 cm) width, we can use all of it by combinations of different width strips. Give me some time to comeupwith a number and get back to you. With rolls or sheets, but with rolls more subject to damage, theedgesare often damaged in transport and handling and from our experience that caused the most waste in the cutting operation as strips sometimes as wide as 3 cm along the edges had to be sacrificedbecauseof damage that could not be repaired. Cutting by itself does not really waste any lead and the only waste is due to damage, lengthandwidth mismatch. If we have the luxury of receiving shipments in batches, even though we place one order for a specific quantity, we can always adjust our estimates on fraction of waste as we go along quite early in the operation, once we know for sure how much we waste for one module given the construction technique and the shipment format.Let me know if this is fine and what further itterations werequire,ifany.We also need to think about a) what tests we require from thevendorandb) what tests we intend to do ourselves, first for thefirst-articletest and second for routine acceptance of shipments. Thoughts?Well, if the vendor can screw up the certification for lead purity, we're in deeper trouble than we could imagine. I think too much hey is being made about the purity of lead here. A pure lead, according to the industry standard, is fine. As long as the lead is not classified as "alloyed", we're fine. So, I would say that from the vendor we should require a certification of purity and we willperformour own tests of swaging and we can also spot check the lead for softness (Brinnel number) to match that of tables for pure lead (I think it's 5). The ultimate judgement is: does the lead swage evenly or not, allelseis irrelevant. My two bits, George |
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