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Statistics on EP treatment of EXFEL
cavities in series production
Some data after electropolishing of more
than 100 caviti...
The Electropolishing facility at Ettore Zanon SpA
for 1.3 GHz – 9 cell cavities
• New EP facility implemented by Zanon fac...
140 µm removal: how is it calculated?
3
Two different ways to estimate mean thickness removal
1. by cavity weight before a...
140 µm removal: how is it achieved?
Two main parameters: Time and Current
4
TIME
• With an error of ~10µm, duration of EP ...
140 µm removal: how is it achieved?
Two main parameters: Time and Current
5
CURRENT
Surface removal control by current is ...
Comparing surface removal and frequency variation
ΔF as a different method to estimate material removal
6
1. All methods p...
About removal at irises and equators
7
• Surface thickness measured by means of a ultrasonic thickness gauge.
▫ Krautkrame...
Thank you for your attention!
8
Statistics on EP treatment of EXFEL cavities in series production
TTC Meeting DESY – Hambu...
Ettore Zanon SpA follows the BCP flash production scheme:
• 140 µm EP as first cleaning,
• 10 µm BCP after helium tank int...
140 µm removal: how is it calculated?
10
Two different ways to estimate thickness removal:
1. By difference of cavity weig...
140 µm removal: how is it calculated?
11
2. By calculation of reacted Nb moles
(integral of current over time):
• 𝑟
𝜇𝑚
𝑚𝑖𝑛...
Comparing surface removal and frequency variation
ΔF as a different method to estimate material removal
12
1. ΔF determine...
• Aluminium cathode 99.5% purity:
▫ 5 mm holes for acid distribution,
▫ Teflon tape to shield cathode at irises.
• Fluorin...
EP facility: automation of the process
14
Experiences on Electropolishing set up at Ettore Zanon SpA
TTC Meeting DESY – Ha...
1. First configuration:
▫ 40 µm EP test  removal by weight: 42.8 µm
▫ vertical test failed!
▫ Hypothesis:
 polishing at ...
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WG1_RizziM_Statistics_on_EP_treatment_of_cavities_in_series_production

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WG1_RizziM_Statistics_on_EP_treatment_of_cavities_in_series_production

  1. 1. Statistics on EP treatment of EXFEL cavities in series production Some data after electropolishing of more than 100 cavities at Ettore Zanon SpA TTC Meeting DESY – Hamburg 24 - 27 March 2014 Speaker: Michela Rizzi
  2. 2. The Electropolishing facility at Ettore Zanon SpA for 1.3 GHz – 9 cell cavities • New EP facility implemented by Zanon factory. • More than 100 EPs from July 2013. • Now working at a rate of 5 cavities/week. • Treatment data: ▫ Horizontal EP, with cavity rotating ▫ 140 µm EP as first main polishing  Usually more than 140 µm are removed to be on the safe side ▫ Constant 17 V applied on cavity for 6 hours ▫ Mean current value: 270 A ▫ Mean temperature value: 31°C. 2 Statistics on EP treatment of EXFEL cavities in series production TTC Meeting DESY – Hamburg 24 - 27 March 2014 Cavity installed on EP facility
  3. 3. 140 µm removal: how is it calculated? 3 Two different ways to estimate mean thickness removal 1. by cavity weight before and after EP 2. by the integral of current over time No infos about actual removal at irises and equators  For this topic, see Ambra Gresele’s presentation Statistics on EP treatment of EXFEL cavities in series production TTC Meeting DESY – Hamburg 24 - 27 March 2014 µm = 𝑊 𝑏𝑒𝑓𝑜𝑟𝑒 −𝑊 𝑎𝑓𝑡𝑒𝑟 7.6 µm = (1.484 ∙ 10−3 ∙ 𝐼 ∙ ∆𝑡) 𝑡=𝑡 𝐸𝑃 𝑡=0
  4. 4. 140 µm removal: how is it achieved? Two main parameters: Time and Current 4 TIME • With an error of ~10µm, duration of EP is the best way to control total removal. + 10 minutes  + 5 micron Statistics on EP treatment of EXFEL cavities in series production TTC Meeting DESY – Hamburg 24 - 27 March 2014 Data used are from weight measurements
  5. 5. 140 µm removal: how is it achieved? Two main parameters: Time and Current 5 CURRENT Surface removal control by current is more difficult: • Current is not constant during EP • Not a free parameter: related to temperature Statistics on EP treatment of EXFEL cavities in series production TTC Meeting DESY – Hamburg 24 - 27 March 2014 Data used are from weight measurements
  6. 6. Comparing surface removal and frequency variation ΔF as a different method to estimate material removal 6 1. All methods presented can only estimate the MEAN REMOVAL 2. ΔF determines the cavity lenght after tuning ▫ Is it possible to predict correctly ΔF  cavity final lenght from EP variables? 3. Correlation between ΔF and µm removed by weight ▫ Data are scattered  no clear correlation Statistics on EP treatment of EXFEL cavities in series production TTC Meeting DESY – Hamburg 24 - 27 March 2014 Data used are from weight measurements
  7. 7. About removal at irises and equators 7 • Surface thickness measured by means of a ultrasonic thickness gauge. ▫ Krautkramer Branson CL3 Ultrasonic Thickness Gauge with sensor Alpha 20/125 016dry. ▫ Data taken from 4 cavities. • Removal at irises is higher than at the equators. ▫ 100 µm guaranteed also at equators. Statistics on EP treatment of EXFEL cavities in series production TTC Meeting DESY – Hamburg 24 - 27 March 2014 High measuring error It makes sense only with long EP treatment (es. 140 µm)
  8. 8. Thank you for your attention! 8 Statistics on EP treatment of EXFEL cavities in series production TTC Meeting DESY – Hamburg 24 - 27 March 2014
  9. 9. Ettore Zanon SpA follows the BCP flash production scheme: • 140 µm EP as first cleaning, • 10 µm BCP after helium tank integration. STEPS FOR EP TREATMENT 1. CLEANING BEFORE EP: a) Car wash and US cleaning in clean room of ISO7 standard 2. ELECTROPOLISHING: a) Installation of cavity in EP bench CAVITY is HORIZONTAL b) Pressure test with ultrapure water CAVITY is VERTICAL c) Draining with nitrogen CAVITY is VERTICAL d) Filling with acid CAVITY is HORIZONTAL e) 17 V applied for ~ 6 hours CAVITY is HORIZONTAL f) Draining with nitrogen CAVITY is VERTICAL g) Rinsing with ultrapure water to safe pH CAVITY is VERTICAL h) Removal from EP bench CAVITY is HORIZONTAL 3. CLEANING AFTER EP a) Transportation to clean room ISO7: car wash and US cleaning b) Inside rinsing to 12MΩ*cm c) 30 minutes 100bar high pressure rinsing (HPR) in ISO4 cleanroom Main EP sequence 9 Experiences on Electropolishing set up at Ettore Zanon SpA TTC Meeting DESY – Hamburg 24 - 27 March 2014
  10. 10. 140 µm removal: how is it calculated? 10 Two different ways to estimate thickness removal: 1. By difference of cavity weight before and after EP: • µm = ∆𝑊𝑐𝑎𝑣[𝑔] 𝑆 𝑐𝑎𝑣[𝑐𝑚3]∙𝜌 𝑁𝑏[ 𝑔 𝑐𝑚3] ∙ 104 = 𝑊 𝑏𝑒𝑓𝑜𝑟𝑒 −𝑊 𝑎𝑓𝑡𝑒𝑟 7.6 ; Scav = inner surface of a 1.3GHz cavity, 91 dm3, ΔWcav = difference of cavity weight ρNb = Niobium density, 8.57 g/cm3, Statistics on EP treatment of EXFEL cavities in series production TTC Meeting DESY – Hamburg 24 - 27 March 2014
  11. 11. 140 µm removal: how is it calculated? 11 2. By calculation of reacted Nb moles (integral of current over time): • 𝑟 𝜇𝑚 𝑚𝑖𝑛 = 𝐼∙𝑀 𝑁𝑏∙60∙105 𝑞 𝑒−∙5∙𝑁 𝐴∙𝜌 𝑁𝑏∙𝑆 𝑐𝑎𝑣 = 1.484 ∙ 10−3 𝐼 𝐴 , • µm = 1.484 ∙ 10−3 ∙ 𝐼 ∙ ∆𝑡 𝑡=𝑇 𝐸𝑃 𝑡=0 ; r = removal rate, as µm/min, I = current intensity [A], MNb = Niobium molecular mass, 92.9 g/mol, qe− = electron charge, 1.6*10-19 C, NA = Avogadro constant, ρNb = Niobium density, 8570 g/dm3, Scav = inner surface of a 1.3GHz cavity, 91 dm3, 5 = oxidation state of Niobium. Δt = 1 min Statistics on EP treatment of EXFEL cavities in series production TTC Meeting DESY – Hamburg 24 - 27 March 2014
  12. 12. Comparing surface removal and frequency variation ΔF as a different method to estimate material removal 12 1. ΔF determines the cavity lenght after tuning  Is it possible to predict correctly the cavity final lenght, depending on EP variables? 2. Correlation between ΔF and µm calculated by integral of current  Data are scattered  no clear correlation Statistics on EP treatment of EXFEL cavities in series production TTC Meeting DESY – Hamburg 24 - 27 March 2014 Data used are from current measurements
  13. 13. • Aluminium cathode 99.5% purity: ▫ 5 mm holes for acid distribution, ▫ Teflon tape to shield cathode at irises. • Fluorinated polymers PTFE, PVD, PFA ▫ For parts in contact with acid • Ultrapure water 18MΩ*cm • 99.999% pure nitrogen • Acid mixture: H2SO4+HF (9:1 ratio) • Usage up to 10 g/l Niobium dissolved EP facility: some details 13 Experiences on Electropolishing set up at Ettore Zanon SpA TTC Meeting DESY – Hamburg 24 - 27 March 2014 Cavity ready for installation on EP bench Cavity installed on EP facility 3D drawing
  14. 14. EP facility: automation of the process 14 Experiences on Electropolishing set up at Ettore Zanon SpA TTC Meeting DESY – Hamburg 24 - 27 March 2014 Process sequence handled by a PLC • Sensors for: temperature, pressure, flowrate, acid level • H2 and HF sensors for personnel and explosion safety. • Movements and rotation controlled by position sensors. Automatic control of current and temperature: ON/OFF controller on cooling line Reaction rate control
  15. 15. 1. First configuration: ▫ 40 µm EP test  removal by weight: 42.8 µm ▫ vertical test failed! ▫ Hypothesis:  polishing at equators not sufficient?  Surface not perfectly smooth? 2. Second configuration: ▫ 40 µm EP test  removal by weight: 50 µm ▫ vertical test OK! Tests with different cathode shielding made with teflon tape 15 Experiences on Electropolishing set up at Ettore Zanon SpA TTC Meeting DESY – Hamburg 24 - 27 March 2014 Constant V = 17V Mean I = 230A Mean T = 31°C Constant V = 17V Mean I = 267A Mean T = 30°C

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