cavity fabrication and preparation sequences for the tesla / ttf cavities at desy
DESCRIPTION
Cavity fabrication and preparation sequences for the TESLA / TTF cavities at DESY 1st ILC workshop at KEK Tsukuba Japan A.Matheisen for DESY and the TESLA Collaboration. Introduction Cavity Production steps Example and overview table comments on cavity fabrication - PowerPoint PPT PresentationTRANSCRIPT
Cavity fabrication and preparation sequences for the TESLA / TTF cavities at DESY
1st ILC workshop at KEK Tsukuba Japan A.Matheisen
for DESY and the TESLA Collaboration
•Introduction•Cavity Production steps
Example and overview tablecomments on cavity fabrication
•Cavity Preparation stepsExample and overview tablecomments on cavity fabrication
•Conclusion and remarks
Since 1990 DESY and the TESLA collaboration have put a lot of activities in the Since 1990 DESY and the TESLA collaboration have put a lot of activities in the field of srf cavities to study and prepare the build up of a TEV superconducting field of srf cavities to study and prepare the build up of a TEV superconducting linear accelerator / TESLAlinear accelerator / TESLA
The choice was made on 1.3 Ghz 9 cell geometryThe choice was made on 1.3 Ghz 9 cell geometry
State of the art of acceleration field gradient was 5 MV/m for multi-cell cavity in State of the art of acceleration field gradient was 5 MV/m for multi-cell cavity in “medium” scale production“medium” scale production
Lots of promising attempts and receipts on single cell were around ( HPP-Cornell / Lots of promising attempts and receipts on single cell were around ( HPP-Cornell / closed BCP /-SACLAY/ HPR - CERNclosed BCP /-SACLAY/ HPR - CERN
Within the TESLA collaboration a test and preparation facility was set up at DESYWithin the TESLA collaboration a test and preparation facility was set up at DESY
IntroductionIntroduction
Decision was made toDecision was made toOrder Cavities in Industry, qualify companies,Order Cavities in Industry, qualify companies,learn on large scale production learn on large scale production Preparation und testing at DESY Preparation und testing at DESY
( ( multiple choice of preparation/ no clear receipt /multiple choice of preparation/ no clear receipt / no specified facility available)no specified facility available)
Cavity fabrication
• Cavity fabrication was set up in close connection with industrial companies
• Each company had its characteristic in manufacturing and specially in welding technique
General fabrication steps applied in all companies are presented here
Cavity (9 Zeller)
Endhalbzell-Endrohr- Einheit
kurz
Endhalbzell- Endrohr- Einheit
lang
Flansch(Hauptkoppler-
Stutzen)
Flansch(Endflansch)
HOM-Kopplerkurze Seite
Rippe RippeAnbindung(end-kurz-lang)
Endhalbzellekurz
AntennenflanschNW 12
HOM-KopplerDESY
End-kurz-lang
Formteil F
Bordscheibelange Seite
Endhalbzellelang
Flansch(end-kurz-lang)
HOM-Kopplerlange Seite
Flansch(Endflansch)
Antennenstutzenlang
Endrohrlang
AntennenflanschNW 12
Formteil Flang
HOM-KopplerDESY
End-kurz-lang
Hauptkoppler-stutzen
Endrohrkurz
Cavity (9 cell TESLA /TTF design)
End group 1 End group 2Hantel
Normalhalb-Zelle
Normalhalb-Zelle
Stützring
Nb-BlechNormalhalelle
Nb-BlechNormalhalbzelle
Dumb-bell
Overview over cavity fabrication
Cavity (9 Zeller)
Cavity (9 Zeller)
Hantel
Normalhalb-Zelle
Normalhalb-Zelle
Stützring
Nb-BlechNormalhalelle
Nb-BlechNormalhalbzelle
dumb bell
Overview over cavity fabrication
Cavity fabrication : Example dumb bell / Cavity
7. Welding of Iris 8. Welding of stiffening rings9. Mechanical measurement of dumb-bells10. Reshaping of dumb bell if needed11. Cleaning 12. Rf measurement of dumb-bell13. Trimming of dumb-bells ( Equator regions )14. Cleaning 15. Intermediate chemical etching ( BCP /20- 40 µm )+ Rinsing16. Visual Inspection of the inner surface of the dumb-belllocal grinding if needed + (second chemical treatment + inspection )
Dumb- bell
1. Mechanical measurement2. Cleaning (by ultra sonic [us] cleaning +rinsing)3. Trimming of iris region and reshaping of cups if needed4. Cleaning 5. Rf measurement of cups 6. Buffered chemical polishing + Rinsing (for welding of Iris)
Dumb-bell ready for cavity
cups Dumb-bell pipes flanges Cone HOM coupler
Forming byForming by Deep drawing
trimming milling milling milling milling
Reshaping Reshaping Yes Yes Yes
Geometry checkGeometry check Yes Yes Yes Yes Yes Yes
cleaningcleaning Yes Yes Yes Yes Yes Yes
Rf measurementRf measurement Yes Yes Yes
trimmingtrimming Yes Yes Yes
cleaningcleaning Yes Yes Yes Yes Yes Yes
BCP for weldsBCP for welds Yes Yes Yes Yes Yes Yes
EB WeldingEB Welding Yes Yes Yes Yes Yes Yes
Geometry checkGeometry check Yes Yes Yes Yes
Rf measurementRf measurement Yes Yes Yes
shaping / trimmingshaping / trimming Yes Yes Yes Yes Yes Yes
BCP for visual BCP for visual inspectioninspection
Yes Yes Yes
grindinggrinding Yes Yes Yes Yes
Overview on fabrication steps for cavity subunits
Cavity welding: the general way There are differences of welding processes in industry
1. Degreasing and rinsing of parts2. Drying under clean condition3. Chemical etching at the welding area ( Equator)4. Careful and intensive rinsing with ultra pure water5. Dry under clean conditions6. Install parts to fixture under clean conditions7. Install parts into electron beam (eb) welding chamber
( no contamination on the weld area allowed)8. Install vacuum in the eb welding chamber <= 1E-5 mbar9. Welding and cool down of Nb to T< 60 C before venting10.Leak check of weld
1 1 pieces 3 1 piece2 7 pieces
Fabrication:1. Sequences need to be adopted to the company hardware2. Companies need to be trained an stay trained
learning curve to stable production 3. Control on subcontractors4. Dependency on major products of company training of personal
Experiences on cavity fabrication:
Deep drawing:1. Reproducibility depends on tool design and tool material specification – investigation in tooling2. Dependency on Nb supplier found 3. Different shape from ingot to ingot found (Hardness / grain size) Better quality control + specification reproducibility
Measurements: 1. Rf measurement of cups / dumb bells Time consuming2. Mechanical measurements of sub units Time consuming
( F part HOM tube / flanges /dumb-bell 3 D measurement complex
combination of mechanical and rf measurement possible ? ( 3 D imaging of units)
Cavity preparation
O Some steps of the preparation are related to the specific hardware With a modified hardware they might be eliminated
Example: Entering procedure for cleanroomProcedureCar wash + Ultrasonic cleaning + ultra pure water rinsing+ drying inside cleanroom
They will be display as
O Some steps are common for all processes independent on BCP or EP processing
They will be outlined by =
Actually more than 50 steps are in the line
General comment
italic letters
Cavity PreparationCavity Preparation
Standard treatment used forTTF Modules 1-5(BCP treatments +1400 C titanium post purification)
BCP
Standard treatment used forTTF Modules 1-5(BCP treatments +1400 C titanium post purification)
EP / 1
Treatment sequence used for the first batch of cavities electro-polishedin collaboration with KEKCombination ofBCP (80- 160 µm)+ EP (80- 100µm) at KEK+EP (20-50 µm) at DESYPart of production1400 C titanium post purified
EP / 2
Treatment sequence under study at DESYNo 1400 C Ti post purification Only EP applied (200 µm) Improved handling sequences
Actually there are 3 general lines
The preparation process can be split up into 4 major steps
Preparation step BFinal cleaning and assembly for vertical test
Preparation step CWelding of connection to He vessel / He vessel welding
Preparation step DFinal cleaning and assembly for module / horizontal test
Preparation step ARemoval of demage layer / post purification / tuning
Cavity preparation (BCP)
As example the BCP treatment use for sequence Module 1-5 at TTFTreatment includes post-purification by Titanium at 1400 C
Part A of preparation
1. Rf measurements and mechanical inspection
2. Chemical etching of cavity inside (CP 80 µm + clean water rinsing) 3. Chemical etching of cavity outside (>20 µm+ clean water rinsing)4. Annealing and H2 outgasing in UHV oven at 800 C
5. Rinsing in ultra pure water 6. Insertion to 1400 C UHV oven ( inside DESY cleanroom )7. Chemical etching (Removal of Titanium surface layer)
cavity inside (CP 80 µm + clean water rinsing) outside ( 40 µm+ clean water rinsing)
Part B of preparation
1. Tuning of field profile
2. Chemical etching of cavity inside (“final” BCP [ 20 µm ] + clean water rinsing)
3. High pressure rinsing4. Drying in class 10 clean room air 12 h5. Assembly of auxiliaries6. Vacuum leak check of flange connections 7. Venting and dismount pumping flange ( beampipe )8. 1st high pressure9. 2nd high pressure rinse10. Drying over night in class 10 cleanroom11. Install antenna for vertical rf measurements
Rf Measurement at 2 K
Cavity preparation (BCP)
1. Enter cleanroom after rf test
2. Venting of cavity3. Removal of variable Antenna 4. Installation of pumping valve5. Install Argon atmosphere inside cavity6. Transport for welding of interconnection ring NB to
Titanium
7. Venting of cavity8. Removal of flanges (beampipe / Input coupler port)9. Measure and install fieldprofile10.Weld helium vessel11. Leak check of vessel welds
Rf Measurement at 2 K
Cavity preparation (BCP)
Part C of preparationHere major differences for BCP and EP cavities appear !!!
Part D of preparation
1. Entering the clean room after tank welding
2. Chemical etching of cavity inside (BCP 20 µm + clean water rinsing)3. High pressure rinsing4. Drying in class 10 clean room air 12 h5. Assembly of HOM Coupler / Pick Up probe / Flanges6. Vacuum leak check of flange connections 7. Venting and dismount pumping flange ( beampipe )8. 1st high pressure9. 2nd high pressure rinse10.Drying over night in class 10 cleanroom11.Mount pumping port for leack check and mass spectrometry12.Leak check13.Mount horizontal platform14.Vent cavity for coupler installation 15.dismount coupler port blind flange 16.Install power coupler17.Final leak check
Cavity preparation (BCP)
Part C of Cavity preparation has major differences for electro polished cavities qualified to 35 MV/m
Cavity preparation for electro polished cavitiesCavity preparation for electro polished cavities
But up to now no qualified and reproducible procedure for This preparation step on Electro-polishing of cavities
with tanks is available
This part of the preparation was set up on the basis that a final surface treatment can be don when the helium vessel is installed
Part A of cavity preparation BCP EP1a EP1b EP2
Field profile measurement /mechanical inspection
OK OK OK OK
Chemical etching of outside
+ clean water rinse
BCP >20 µm BCP >20 µm BCP >20 µm BCP >20 µm
etching of cavity inside
+ clean water rinse
BCP80 µm BCP80 µm BCP80 µm EP 160 µm
Annealing and H2 out-gassing in UHV oven at 800 C
OK OK OK OK
Rinsing with clean water ok ok ok ok
TI post purification
Oven inside DESY cleanroom
1400 C 1400 C NO NO
Removal of Titanium layer
Chemical etching
inside + clean water rinse
BCP 80 µm BCP 80 µm no no
Chemical etching
outside + clean water rinse
BCP >= 40 µm
BCP >= 40 µm
no No
Field profile measurement /mechanical inspection
ok ok ok ok
Summary table for Part A of cavity preparation
BCP EP 1a EP 1b EP 2
Final treatmentFinal treatment BCP 20 µm (DESY) EP 100 µm (KEK) EP 100 µm (KEK) EP 40 µm (DESY)
High pressure rinseHigh pressure rinse ok at KEK at KEK At DESY
TransportationTransportation Yes Yes
fieldprofilefieldprofile tuning tuning
HP rinsesHP rinses yes yes
Assembly Assembly auxiliaries auxiliaries auxiliaries auxiliaries
High pressure rinseHigh pressure rinse 2 times 3-5 time 3-8 times 6 times
Drying in cl 10 12h cl 10 cleanroom 12h cl 10 cleanroom 12h cl10 cleanroom 12h cl 10 cleanroom
Install antenna for vertical rf test for vertical rf test for vertical rf test for vertical rf test
120 C baking120 C baking No Yes Yes Yes
resultsresults On AC Cavities average
28,6 MV/m
(26-32 MV/m)
2 cavities
35 MV/m
2 cavities 23MV/m field emission loaded
4 cavities field emission loaded
2 cavities <26MV/m limit: fabrication error
2 Cavities
<30 MV/mLimit: material
Additional Additional treatmentstreatments
5 µm BCP
1 cavity 35 MV/m
5 µm BCP
1 cavity 35 MV/m EP 40 µm (DESY)
2 Cavity 37 MV/m
Summary table for Part B of cavity preparation
Cavity preparation for electro polishing EP 1Cavity preparation for electro polishing EP 1
Part C of Cavity preparationReentering cleanroom after rf test
Remove variable Antenna Install bead pull and measure field profile inside cleanroomAdjust fieldprofile (outside of cleanroom
Installation of antennas for mode spectrum controlHigh pressure rinsingInstall Argon atmosphere inside cavityTransport for welding of interconnection ring NB to Titanium
Venting of cavityRemoval of antennas Install bead pull and measure field profile inside cleanroomHigh pressure rinsingAdjust fieldprofile outside of cleanroom
Remove bead pull systemHigh pressure rinsinginstall of antennas for mode spectrum analysisWeld helium vessel Leak check of vessel welds
2 cavities lost gradient due to not well established manipulation
This procedures are much too complicated
Way out is to install bead pull and rf antennas that go with the cavity on that process ?
cavity interior sealed inside the cleanroomhermetically until preparation for Module / horizontal test ( under investigation)
Way out development of final treatment on dressed cavities ?Light BCP ?Oxi polishing ?Cavity ep with tank ?
conclusion
Cavity production in industry has to set up with good results
We learned .That the Production is depending on company specific ways Industry need training and sensitization for the cavity productionThe rise up time until stable production is company depending
Procedures for cavity treatment are available
We learned that - Only when the procedures are followed strictly the results are stable- Any missing step leads to cavity performance degradation- Errors in the sequence need a step back in the process- Any changes in the process, even small once have impact on others steps
and needs a reestablishing and a new qualification of the procedure- Cavity results on single cell are not one to one transferable to multi-cells- Changes in a procedure has to be qualified on 9 cell cavities - For Electro polished cavities investigations on the reproducibility of the process are needed- Investigations on final treatment after vertical measurements have to be made to have a smooth and reliable process after vertical measurements
conclusion