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This project involves etching the wall thickness of the VELO chamber down to 150μm to enhance particle transparency and detector resolution. The process, challenges, solutions, and outcomes are detailed.
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VELO RF Foil ThinningChemical Etching (continued) Pierre MAURIN Requestor : Massimiliano Ferro-Luzzi (PH-LHCb)
Summary «VELO» chamber project for LHC-b • Objective • Etch box wall thickness down to 150 μm to increase transparency for particles and improve detector resolution • Activities with spare VELO box (present geometry) • Process control • Average thickness • Mask product • Activities with new geometry half-box • Activities with 3D forged samples Pierre Maurin TE/VSC/SCC
Activities with the spare VELO box Etching VELO box prototype picture 1 • Chemical etching: ≈ 50 mm wide, remove 100 μm (picture 1) ~50mm (clear >36mm) • Tested the support (picture 2) with the VELO box picture 2 • Masked surface is always the one kept at 300 μm • Etched the surface during 90 min (picture 3) • Rinsed and dryed surface • Controled the etching surface zone mask • Removed the mask painting EN-AW5083 (AlMg3) zone etched 95% Aluminium (Mg 4%, Mn 0,4%) fromCERN stores picture 3 Pierre Maurin TE/VSC/SCC
Activities with the spare VELO box Problematics and solutions • Problems • Holes (figure 1) • Mask removal led to box deformation (figure 2) • How we solved the problems • New mask material replacement • Continuous temperature control • Splitting of the etching process in • at least two steps figure 1 figure 2 Pierre Maurin TE/VSC/SCC
Activities with the new geometry half-box • Thinningprocedure: • Degreasingwithultrasound agitation • Mask painting • 1st etchingwithNaOH (5M), approx. 75 microns • Control removedthickness (Chemical analysis) • by ICP/OES on bath sample • 2ndetchingwithNaOH (5M), approx. 75 microns • Control removed thickness (Chemical analysis) • by ICP/OES on bath sample • Removemasking • Degreasingwithoutultrasound agitation Half-Box prototype Aluminum type: W19 zacht AlMg3 (serie 5754) Pierre Maurin TE/VSC/SCC
Activities with the new geometry half-box Support box of etching and control tools • Support box chamber (PVC) • Digital thermometer to control the temperature of the solution • Digital thermometer to control the ambient air • Chronometer • Retention tray During the etching the box is tilted by 40° Pierre Maurin TE/VSC/SCC
Activities with the new geometry half-box 1st chemical etching 1st chemical etching: NaOH (200 g/l): 2000 ml Time: 45 min Start temperature: 22,3°C Finish temperature: 28,7°C Pierre Maurin TE/VSC/SCC
Activities with the new geometry half-box 2nd chemical etching 2nd chemical etching: NaOH (200 g/l): 2000 ml Time: 37 min Start temperature: 23,5°C Finish temperature: 31,5°C Pierre Maurin TE/VSC/SCC
Activities with the new geometry half-box Measurement of Aluminium concentration in NaOH 5M bath after etching by ICP-OES The composition of the AlMg3 EN-AW 5754 alloy used is 96,6465% aluminium (Mg 3,3535%). For the real surface of 300 cm2, the thickness of the alloy removed is 82 microns for the first etching and 92 microns for second etching. The total thickness removed is 174 microns. Pierre Maurin TE/VSC/SCC
Activities with the new geometry half-box Conclusion • The calculations showed that for a target • thickness removal of 150 microns • 174 microns (+24 microns) were attained. • Temperature changed between the first • and the second etching. • 1st etching: average Speed was 1,71 µm/min • 2nd etching: average etching speed was 2,48 µm/min • Temperature remains a critical parameter • in the process. Pierre Maurin TE/VSC/SCC
Activities with 3D forged sample • Thinningprocedure: • Degreasingwithoutultrasound • Sampleweighting • Mask painting • 1st etchingwithNaOH(5M), 30 minutes • Sampleweighting • 2ndetchingwithNaOH(5M), 30 minutes • Sampleweighting • 3rd etchingwith NaOH(5M), 10 minutes • Sampleweighting • 4th etchingwith NaOH(5M), 10 minutes • Sampleweighting 3D forgedsample 0,5 mm thickwall BLOC FORGE 3D ALLIAGE EN-AW 5083 ETAT H112 SELON EN 586-2 CONFORME FICHE TECHNIQUE Nº620-2 - EDMS 1516490 DIMENSIONS : 310 MM X 315 MM X 1200 MM Pierre Maurin TE/VSC/SCC
Activities with 3D forged sample 1st etching 2nd etching 3rd etching 4th etching Times: 30 min Times: 30 min Times: 10 min Times: 10 min X15 X15 Binocularpictureafter 1st ectching Binocularpictureafter 4th ectching Pierre Maurin TE/VSC/SCC
Activities with 3D forged sample Weight control of sample (0,5mm) Before etching (after masking surface), the weight of sample is 111,050 g The composition of the EN-AW 5083 alloy used is 94,8% aluminium (Mg 3,3535%, Mn 0,4%). For the real surface of 27 cm2, the total thickness removed is 148 microns. Pierre Maurin TE/VSC/SCC
Activities with 3D forged sample Conclusion • The calculations showed that for a target • thickness removal of 150 microns, • 148 microns (-2 µm ) were attained. • 1st etching: average etching speed was 1,76 µm/min • 2nd etching: average etching speed was 2,3 µm/min • 3rd etching: average etching speed was 1,4 µm/min • 4th etching: average etching speed was 1,3 µm/min • Control thickness metrology • Microscopic observation Pierre Maurin TE/VSC/SCC
Conclusion • For real box apply shorter steps • Future tests with different volumes/surfaces ratios Pierre Maurin TE/VSC/SCC
