Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 1 "Advances in Electro polishing of Niobium Resonators" Axel Matheisen, DESY Hamburg for the CARE JARI WP 5 collaboration partners

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 2 Short overview on Status at start of Jari 1 Hardware problems and improvements Quality control (acid management) Sulfur segregation and ethanol rinse Summary

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 3 Status of EP facilities at Start of Care Jari DESY multi cell EP bench: hardware set up in 2003 and operational in study mode Chemistry lab: under construction to be modified for EP test set CEA Saclay and INFN Legnaro Sample test facilities available Single cell setup to be ordered and to be installed at project start Changes in respect o proposal during the Program of WP 5 Set up and legal procedures for single cell EP apparatus took more time than expected For WP 5 the DESY EP bench is use to optimize parameters for EP processes.

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 4

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6 To study best parameters the following problems needed to be fixed System not operational due to high HF System operation: out gassing of HF from the acid mixture is extremely high commercial HF absorbers not sufficient Life time of acid and its influence on cavity gradients and the process Hardware problems and improvements

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 7

8 Operation data of DESY EP bench beginning of 2005

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 9 View on commercial wet Gas scrubber View on gas exhausting pipes of commercial gas scrubber Commercial EP absorber limits treatment time (low efficiency for large amounts of HF gases)

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 10 1€ / liter ; Volume 8*10 l in cascade cartige / life time 8*10Hours of EP Dry HF absorbent installed at the” point of appearance” HF Absorbent COSA D in commercial cartridge HF Absorbent COSA D in cascade cartridge (Part of Ouality control of acid mixtures)

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 11

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 12 Receipt most common and in use at DESY * Mix 9 volumes of H2SO4 (>96%) and 1 volume of HF (>45%) Apply 17 Volt DC voltage Studies in test mode showed best parameter for shine surfaces and optimized process time 1a) „theory“ of acid mixture Quality control (Acid management) Electro chemical reaction of the ep process

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 13 HF Evaporation 1:9 [HF(45%) / H2SO4 (96%) ] + H2O due to hygroscopic reaction of H2SO4!  H2SO4 + H2O ----> H2SO3 + H2SO4 + HF ----> FSO3H + H2O HF +H2OFSO3H H2SO3 H2SO4 HF 1.b“Reality” of the EP prescription HF Consumption

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 14 It was found that Out gassing strongly depending on way of mixing the acid  procedure to be fixed for acid mixing Observation a) strong differences in gaseous HF evaporation from batch to batch b) Differences in removal rates / current from batch to batch c) Differences in gaseous HF evaporation from supplier to supplier

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 15 2) Analysis of H2 content of acid mixture for different procedures of mixing

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 16 Conclusion from observations: QC methods have to be installed to control delivered acid!! define and control acid parameters to study the EP process

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 17 Diagramm 2:Versuch 1 bei 30°C, HF-Gehalt relativ zur frischen Säure 3a) Determine acid mixture by U/ I on test apparatus SRF Documents HF content in Mixture U/I diagram at 30 C treatment temperature

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 18 SRF Documents U/I diagram at 30 C treatment temperature 3a) Determine acid mixture by U/ I on test apparatus

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 19 3b)Measure removal rates indicator for “aging” of acid Removal rate calculated from weight difference before and after EP ( treatment time of more than 120 Min)

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 20 SRF Documents c) Aging of acid studied with U/I test apparatus

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 21  for large scale production find industrial acid management and instruments to be applied as QC and process control instrument Study on acid management by industry launched (Henkel Lohneletropolitur)  Study to be done in 3 phases 1: Define best instruments for research and production 1.1 Overview of commercial systems 1.2 examine commercial systems with standardized mixture 1. 3 evaluate best candidates 2: Define sensitivity and reproducibility of evaluated systems 3: Apply systems in process and examine handling

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 22 Part 1 published at TTC Meeting WG 3 by C.Hartmann TTC-Meeting at KEK 2006 Sept.25-28, 2006 Analysis technique of the HF-H2SO4-electrolyte Christian Hartmann Henkel Lohnpoliertechnik GmbH

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 23 Conclusion of study part 1 VerfahrenAnalyse Gerätekosten in € AnalysedauerAnalysekosten Empfehlung Henkel AASElementanalyse bis ,- 2 min / Analyse für 10 Elemente 128,-€ /Std. Labor nein ICP-OESElementanalyse Alle Elemente parallel ca ,- 3 min / Analyse für 20 Elemente 128,-€ /Std. Labor ja IC Ionenchromatographie Ionen (SO4, F-, FSO3H) ,- bis ,- 20 min / Analyse 128,-€ /Std. Labor ja TOC Total Carbon Org. Verunreinigungen bis ,- ca. 15 min / Analyse 128,-€ /Std. Labor ja FTIR-ATR (Infrarot) Ionen (SO4, F-, FSO3H ?) , ,- 3 min / Analyse Miete 500,-€ / Woche Evtl. tiefer einsteigen NMR Org. Verunreinigungen ,- bis 4 Mill. 15 min / Analyse 150,-€ / Analyse nein CE Kapillarelektrophorese Ionen (SO4, F-, FSO3H) bis ,- 60 min / Analyse 2.500,- / 10 Proben ja CE oder ITP ITP Isotachophorese Ionen (SO4, F-, FSO3H) ,- 20 min / Analyse 1.000,-€ + 70,-€ Probe ja CE oder ITP TitrationGesamtsäuregehalt bis ,- ca min / Analyse 1000,-€ pro Tag sinnvoll

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 24 Care conf srf Sulfur segregation and ethanol rinse Electro-polishing Surface Preparation for High Gradient Cavities at DESY A.Matheisen, H.Morales, B. Petersen, M.Schmökel, N. Steinhau-Kuehl Deutsches Elektronen Synchrotron DESY, Hamburg, Notkestraße 85, Hamburg, Germany PAC 2005

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 25 Observations on maintenance after 100 h of operation Electrode N2 overlay pipe located on top of electrode

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 26 Conclusion : En milieu sulfurique concentré ([H2SO4] théor. ≥ 8,94 ± 0,12 mol.L-1) et chaud (30 et 40°C), l’aluminium réagit avec les anions sulfates pour conduire : A la formation de soufre cristallisé, en quantité plus ou moins importante et à partir de la réaction (8) ou (8’) suivante : 2 Al + SO42– + 8 H+  2 Al3+ + S  + 4 H2O (8) 2 Al + 4 H2SO4 conc.  Al2(SO4)3 + S  + 4 H2O (8’) A la synthèse effective d’hydrogène sulfuré H2S gazeux, à partir du soufre précédemment formé et lorsque [H2SO4 / [H2O] > 1,00 ± 0,05 (tests A, B et G). Son mécanisme de formation s’écrit : 2 Al + 3 S + 6 H+  2 Al H2S  (9) ou 2 Al + 3S + 3 H2SO4 conc.  Al2(SO4)3 + 3 H2S  (9’) IMPURETES Aluminium et Soufre Dans Les Bains d’Electropolissage (Systèmes ternaires HF – H2SO4 – H2O) De Matrices Niobium A. ASPART, F. EOZENOU, C. ANTOINE DSM/DAPNIA/SACM/LESAR CARE-Pub Origin of sulfur in the EP process ?

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 27 PLANCHE PHOTOGRAPHIQUE8 ATTACK of Aluminumby H 2 SO mol.L -1 to T BATH = 40°C t =562 min, scale = x1000, e Al = 59.2 µm t =712 min, scale = x1000,e Al = 74.8 µm

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 28 4 Sulfur found in test set upSulfur sediments on DESY EP set up

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 29 PLANCHE PHOTOGRAPHIQUE6 ATTACK ofAluminumby H 2 SO mol.L -1 to T BATH = 30°C:Test"A" t = 955 min, scale = x500, eAl = 37.8 µm e Al = 37.8 µm t = 955 min, scale = x500, after washing by CHCl 3

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 30 Conclusion: Origin of sulfur found Not connected to Nb removal process Sulfur is build up inside the Cavity on the electrode Method's to cure A) Filter  not effective origin is inside the Cavity + S will plug filter B) Use inert metal for electrode  Platinum Solid electrode need: “body guard” for the electrode Plating: Only on short sections; acid exit hole can not be plated C) Dissolve without effecting the Nb surface quality

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 31 Experiments on tube with sulphur layer before after ethanol cleaning

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 32 [fe limit = 1*exp-2 mGy/min in vertical tests step DESY] Rf test results after fine EP treatment [no120 C bake!!!!] Limited by weld problem

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 33 Comment: FE Limit = Max. allowed radiation level (2*10 -2 mGY/min for module acceptance of Cavities measured in vertical insert at DESY Influence on 120 C baking on cavities with alcohol rinse applied

Axel Matheisen DESY CARE 07 Meeting Cern Switzerland 34 Summary The multi cell apparatus at DESY is reproducible in operation operational since a new HF absorber system with high reliability and low cost is installed Optimized parameters for the EP test bench of multi cell 1,3 GHz resonates are fixed Parameters for reproducible acid mixtures are fixed. A quality control and acid management system is launched and will be continued Source of sulfur causing fieldemission is located Application of ethanol rinse showed improvements on fieldemission level Basic studies don't show limitations related to apparatus or acid if all process parameters are set properly