1. IRC/SAC status Venelin Kozhuharov for the SAC/IRC working group NA62 Meeting 11.04.2014

2. IRC production Lead machining – chosen the same technology as for the SAC production (proven to lead to successful results): –Drawing of the disks with the holes –Production of a matrix –All lead disks are made using the single produced matrix MATRIX IS THE ORIGINAL Scintillator machining – chosen the CNC way –Drawing of the details with the holes –The drilling/cutting machine machines all the elements according to the specified drawing DRAWING IS THE ORIGINAL

3. Scintillator drilling The CNC @ Protvino: Positioning: 5um Repeatability: 3um

4. Further steps We should converge the two technologies in order to proceed: different scenarios could be considered: IHEP uses the matrix as a reference instead of the drawings - already available - only single original - each hole to be probed directly by the CNC Measure the coordinates of the holes and create a drawing out of the product - use the actual positions as a reference - can crosscheck matrix with lead - time scale Throw away the present lead and redo it with CNC - use a single original: drawings - safe time on measures, algorithm for matching, etc. - cost for material - cost for production - time scale All three scenarios were VALID! –Not sure which one is the optimal –We didn't succeed to agree on the first one so it was dropped –Proceed with the rest in the given order

5. Lead metrology Former measurements: –CERN: ~30 holes –IHEP: distances along several lines –PISA: three lead plates (578 measurements/plate) All the measurements indicated that the nominal positions should not be used as a reference for machining if we want to get best results A complete map of the holes is necessary –Even if we really didn't have an algorithm for matching the individual measurements in a best and consistent way Could match individual objects (holes, diameters), but lead is soft so the position of the lead ring is really defined by the holes grid itself! –Completely consistent with the fact that the original is the matrix

6. Procedure Throw away some of the previous measurements as not indicative: –Lead disks: 70 (IRC) + 10 (SPARE) + 3 (spare of the spares) –3 SoS did go any QC (the others we assembled in stacks with holes traversable by a 1.2mm stick) –Each (PISA, IHEP and CERN measured 1 of the SoS) Complete mapping of the holes, inner and outer diameter of –4 downstream disk –2 upstream disk –The matrix All measurements were done in PISA before and after the Christmas Perform a best matching fit Perform a best coordinate fit

7. Measurements

8. Plate/Plate correspondance Two spare disks Spare + SoS disk Two spare disks Best rigid transformation to fit one disk onto another –Rotation + translation: 3 parameters –Minimizing:  r i 2, sum over the fiber holes

9. Many disk matching Chosen a free fit method –(1140 + 3*N disks ) parameters –X i, Y i coordinates of the fiber holes –  j, a j, b j – rigid transformation parameters of the individual disks Compare the positions of the holes with the fitted one 6 disks: 2 upstream + 4 downstream mm The position of the holes seem to fit reasonably well

10. Matrix matching mm The fitted position is well in agreement with the matrix nominal hole's position

11. Holes fitting mm matrix fit Displacement of the holes with respect to nominal mm

12. Holes fitting

13. Possible problems with 3-5% of the fibers (560 in total) –A “mild” recovery seem possible –Need to measure the tube

14. Conclusion A study of the lead holes positioning done thanks to the measurements at INFN PISA –Participants in the work above: Cesidio Capoccia, Filippo Bosi, Marco Ceccanti, many thanks! Obtained coordinates to be provided for the scintillator drilling Both set of coordinates (fitting or matrix) show equal quality Could not have proceed further without that step Considering to assemble the IRC in Frascati –Better technical support –Possibility to test the detector at BTF