ILC S0 Strategy

1
ILC S0 Strategy
GDE status ??? 4?28? (???????????????)

• Proposal
• FNAL 24.4.2008

2
S0 Status High Gradients

• Field emission has been reduced
• This is good news
• Monitoring the three approaches (Ethanol,
  Ultrasound or Fresh EP) needed
• Is there a significant advantage of one over the
  other?
• Data set for Fresh EP on multi-cells small
• Still rather large gradient differences are
  observed due to thermal breakdowns
• Needs improved understanding of the nature of
  these breakdowns
• E.g. some of the very low gradient breakdowns
  have been tracked to the equator region
• At higher gradients this is not yet obvious
• Need improved diagnostics
• High-resolution temperature maps and high
  resolution optical inspection
• There is a broad consensus on this in the SCRF
  community
• See recent TTC Meeting at DESY
• In the following a program to attack this problem
  is proposed

3
S0 Program Rationale

• Take a sample of cavities e.g. DESY 4th
  production
• May depend on manufacturer
• Assume cavities below a threshold (ltXX MV/m) have
  well identifiable defects (gt50 um)
• This is substantiated by the initial results on
  AES cavities
• Decision Point at threshold
• ltXX MV/m
• Identify and remove defect
• Retest
• Demonstrate effectiveness of guided repair
• 20 of cavities go this way if estimate from
  DESY 4th production
• gtXX MV/m
• need understand causes of cavity performance
  variability at high-gradient limit
• Possible Hypotheses
• Visible defects (with high-res optical
  inspection), but smaller
• contaminants from solvent/detergent rinse
• Process-test-reprocess-retest is required using
  thermometry
• This was done e.g. with Ichiro 5

4
ILC S0 Feedback Loop
Cavity Incoming QC
Feedback Improve Specification/QC
Huge Irregularities eg. Scratches
Countermeasure (Guided Repair)
Standard Cavity Preparation Cycle
Witness Samples
Identify Irregularities eg. pits
Standard Vertical Test Cavity
lt XX MV/m
Understand nature of high gradient
limitation e.g. does minor EP move quench
location
gt XX MV/m
Additonal Processing Cycle
Standard Vertical Test Cavity
Single Cells
Samples
Horizontal Tests or Module Assembly
5
Definition of the Cavity Processing Cycle

• Incoming cavity QC Niobium material and cavity
  fabrication
• Optical inspection of as-received cavity.
• Decision Continue or Repair
• Standard Processing Recipe
• Bulk electro-polishing of 150 um.
• Ultrasonic degreasing.
• High-pressure rinsing.
• QC Optical inspection
• Hydrogen degassing at 600 deg C.
• Field-flatness tuning.
• QC Optical inspection
• 20 um electro-polishing.
• Ultrasonic degreasing.
• High-pressure rinsing.
• Assembly and vacuum leak testing.
• 120 deg C bake.
• Vertical dewar test.
• Decision Optical inspection or send to module?
• QC Optical inspection

6
Definition of Standard Test

• Hold at 100 K during cool down to check for Q
  disease.
• Q vs. T measurement during cool down.
• Q vs. E measurement on p mode. RF process as
  needed.
• Q vs. E measurement on all other modes. RF
  process as needed.
• Final Q vs. E measurement on p mode.
• Notes
• All Q vs. E measurements to include radiation
  data logging.
• Utilize 9-cell T-mapping system if available.
• Diagnostic Techniques
• Determine limiting cells based on mode
  measurements.
• If 9-cell T-mapping was not employed, apply
  thermometry to limiting cells and retest.
• Perform optical inspection of limiting cells.

7
Definition of Countermeasures

• Defect is identified, size is known
• Possible Countermeasures
• Local
• Grinding and/or etch
• guided repair e.g. diamond proposed by Hayano
• Re-weld
• needs to be validated on samples first
• Full cavity
• Tumbling
• better for defects in equator region
• Full EP with sufficient removal
• especially effective in iris region
• Titanisation
• very time consuming treatment
• should be the last resort

8
Choice of the Threshold Gradient XX MV/m

• Repair and testing cycles are likely resource
  limited
• Some repair methods not yet available
• Overall resource issues
• Proposal
• Test of a set of cavities
• Subset of 20 low-performing cavities will be
  repaired
• Demonstrate the effectiveness
• Gradient should at least reach the average of the
  80 of the cavitiy set
• The threshold should therefore increase over time
  and is measure of the success of the program

9
Definition of a Single-Cell Program for S0

• Use a set of single-cells cavities to calibrate
  the systems mentioned i.e. optical inspection and
  thermometry
• A detailed analysis of the results is needed
• Need to determine
• the distribution of defects (size, location,
  type) with optical inspection
• the distribution of hotspots below maximum field
• the quench location
• final step could be the dissection of the cavity
• Check for correlation with the
• weld affected region e.g. overlap
• grain boundary
• grain size
• Re-treatment of several cavities is needed to
  verify whether the breakdown locations are
  changing or are locally invariant
• Sample cavities to included
• Fine grain, welded
• Large-grain (or single crystal), welded
• Compare EP and BCP
• Fine-grain seamless
• Acknowledgdement
• Some work has already started e.g on effects of
  grain boundaries

10
Requirements for a Sample Program for S0

• The sample program should investigate
• Quality of the weld region
• check for voids
• use as witness samples in fabrication
• simulate procedures at companies
• (RRR distribution See DESY results W. Singer et
  al.)
• Improvements of weld quality
• EP of weld regions before EBW
• Sample holder cavity
• Witness samples from preparation process
• Use all available surface inspection methods...
• Acknowledgdement
• Some work has already started e.g on residues
  from preparation processes
• This should be encouraged and intensified

11
Conclusion

• After reduction of field emission additional
  diagnostics methods need to be applied
  systematically
• High-resolution optical inspection and
  temperature-mapping have shown very encouraging
  results
• A plan has been developed to implement a feedback
  loop into the cavity production cycle
• Loop is designed to generate understanding of
  nature of defects
• E.g. origin and relevance of defects by optical
  inspection
• Need more data to substantiate results from Kyoto
• Supporting single-cell and sample program
• Standard test definition will allow to compare
  data across labs

12
Cavity Integration summary
H. Hayano April 25, 2008 ILC-SCRF meeting _at_FNAL
13
Followings were discussed

• Tuner performance
• Tuner Motor location
• Tuner specification profile table
• Input coupler industrialization
• Input coupler tunability
• Input coupler specification profile table
• S1 Global issues

14
Tuner performance

• Lorentz detuning simulation (Y. Yamamoto)
• discussion need more clear discussion why
  we need stiff tuner,
• cost of stiff vs. cost
  of robust piezo?
• Ball-screw tuner performance results (T. Saeki)
• preliminary report on LD compensation,
  dø/dt detuning measurement, microphonics, etc.
• Blade tuner update (C. Pagani)
• version 3 blade tuner tested at DESY,
  BESSY. 8 unit will be delivered to FNAL in May.
  
• Comment on tuner motor reliability (S. Noguchi)
• discussion difficult to estimate MTBF,
• need to compare benefit of motor outside vs.
  risk increase like vac leak.
• repaireble with minimum cost (with minimum
  design change and minimum risk ) should be
  consensus.

15
Spec. Profile Table (Slow tuner) _at_Apr.2008 GDE
FNAL meeting
Red box and red filled column will be decide later
16
Spec. Profile Table (Fast tuner) _at_Apr.2008 GDE
FNAL meeting
Red box and red filled column will be decide later
17
Plan for developing Tuner Work Package

• Finalize spec. profile table, today.
• Upload to EDMS team workspace now.
• Revise any spec. in any time, if it is
  inconsistent.
• Develop tuner comparison table and RD of each
  tuner for EDR baseline selection.
• Write and develop recommendation of
  motor/acutuator location according to the past
  presentations and RD, report it to PM by the
  next Chicago meeting.

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Example of comparison table
Slow Tuner Slow Tuner Slow Tuner Slow Tuner Slow Tuner Slow Tuner
TTF STF STF
Saclay -1 Blade Slide Jack Ball Screw
Lifetime Test ( 0.1mm x 10000 Times) is necessary. Lifetime Test ( 0.1mm x 10000 Times) is necessary. Lifetime Test ( 0.1mm x 10000 Times) is necessary. Lifetime Test ( 0.1mm x 10000 Times) is necessary.
Mechanism Double Lever BladeLeverScrew WedgeScrewGear ScrewWorm Gear
Blade has the potential Problem of Fatigue. Life time of Coating?
Stiffens N / ?m 40 25 290 1000
Not Stiff Not Stiff. If used to TESLA Cavity DLD at Flat-Top becomes 900Hz.
Stroke mm lt 2 3.5 Long enough
Location Beam Pipe Jacket Cylinder Jacket Cylinder Jacket Cylinder
The room for tuner is small. Top Heavy. Alignment?
Cost
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Cont.
Fast Tuner Fast Tuner Fast Tuner Fast Tuner Fast Tuner Fast Tuner Fast Tuner Fast Tuner
TTF STF STF
Saclay -1 Blade Slide Jack Ball Screw
Piezo(200V) Piezo(200V) Piezo(150V) PiezoBlade
Speed ? Blade has the potential Problem of Fatigue. Speed ?
NORIAC (1 Spare) NORIAC (1 Spare) Piezo Mechanic x 1 Piezo Mechanic x 1
Size Size mm mm 10 x 10 x 26 10 x 10 x 38 f20 x 18
Stiffness Stiffness N / ?m N / ?m 105 70 500
Max. Load Max. Load kN kN 4 4 14
StrokeRT StrokeRT ?m ?m 40 60 20
Stroke2k Stroke2k ?m ?m 4 6 2
Compensation Compensation ?m ?m 3.4 6 1
Speed Speed
Delay Delay 0.6 msec.

Repairability Repairability Repairability Repairability Repairability Repairability Repairability Repairability
Motor need Disassemble need Disassemble need Disassemble Outside Poor
Piezo need Disassemble need Disassemble need Disassemble Repairable need Disassemble
US Study on this Subject exists. US Study on this Subject exists. US Study on this Subject exists. US Study on this Subject exists. US Study on this Subject exists.
How to check Piezos just we install. There are no experience for long term operation in Pulsed mode. Life time Test is necessary. How to check Piezos just we install. There are no experience for long term operation in Pulsed mode. Life time Test is necessary. How to check Piezos just we install. There are no experience for long term operation in Pulsed mode. Life time Test is necessary. How to check Piezos just we install. There are no experience for long term operation in Pulsed mode. Life time Test is necessary. How to check Piezos just we install. There are no experience for long term operation in Pulsed mode. Life time Test is necessary.
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Coupler discussion

• XFEL coupler (S. Prat)
• Information on coupler industrialization
  status, plan, cost, etc.
• Fixed coupler operation (S. Noguchi)
• grouping cavity concept for maximum E
  operation with rough cost comparison.
• discussion gaussian cavity gradient
  distribution is feasible?
• optimistic estimation?
  Error will be more small.
• Cost minimum for
  matched condition?
• Small LLRF margin.
  
• Variable/Fixed coupler technical issue (E. Kako)
• Visualized discussion of variable/fixed
  coupler installation.

21
Spec. Profile Table _at_Apr.2008 GDE FNAL
meeting
Red box and red filled column will be decide
later
Yellow box are Revised in this Meeting.
22
Plan for developing Coupler Work Package

• Finalize spec. profile table, today.
• Upload to EDMS team workspace now.
• Revise any spec. in any time, if it is
  inconsistent.
• Develop pros/cons table for tunability.
• Write and develop recommendation of tunability
  according to the past presentations, report it to
  PM, by the next Chicago meeting.

23
S1-Global at KEK STF

• Technical points of S1-Global
• Two STF cryomodules have different design for
  STF-BL and LL cavities, respectively.
• Module A cryostat was designed for accommodating
  four BL cavities, and Module B cryostat for four
  LL cavities.
• The helium vessel design of STF-LL cavity has
  geometrically common concept with DESY and FNAL
  vessels. The design of STF-BL cavity package has
  many different points to DESY and FNAL vessels.
• Proposed combination of different types of
  cavities for S1-Global,
• Module A will consist of 4 BL cavities or 3 BL
  cavities 1 LL cavity.
• Module B will consist of 2 DESY cavities 2 FNAL
  cavities or DESY FNAL LL cavities.

Module A for BL cavities
Module B for LL cavities
DESY1 DESY2
FNAL1 FNAL2 gt32MV/m gt32MV/m
gt32MV/m gt32MV/m
S1 Global original concept
(DESY or US) BL2 BL5
BL6 gt32MV/m 29MV/m ??MV/m
??MV/m
( or BL7?)
( or LL 7? LL8?)
2 DESY cavities 2 FNAL cavities
4 KEK-BL cavities
DESY and FNAL cavities are considered to be
assembled in the Module B.
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Problem-1 Incompatibility between DESY FNAL
cavity package and STF cavity package
DESY FNAL Cavity Package
STF Cavity Package
Input couplers and LHe supply cross connect pipes
of KEK and DESY FNAL locate in the opposite
side with respect to the direction of cavity
package
25
Problem-2The length of the GRP is not enough
for supporting FNAL or DESY cavitieswhen they
are installed in STF module.
FNAL Cavity Package
STF-LL Cavity Package
26
Problem-3 Pipes support Interference
between DESY FNAL cavity package and STF GRP
LHe supply pipe
LHe supply pipe support
Support legs of GRP
Viewed from upper-side

1. FNAL LHe supply pipe cross connect and DESY LHe
   supply pipe support conflict with STF GRP support
   legs.
2. Locations of support legs and support tabs are
   not consistent.

27
Problem-4 Coupler port Interference between
Module-B cryostat and DESY FNAL cavity packages
DESY Input Coupler Flange Interference by 14.74mm
between the flange and the coupler port flange.
Input coupler port of the STF-Module-B cryostat
The coupler ports on the Module-B need to be
modified to accommodate both KEK Input Coupler
and DESY Input Coupler.
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Module A Module B Required items for construction S1-Global
C 1 4 KEK-BL cavities 2 DESY cavities 2 FNAL cavities Module A No requirement Module B Gas return pipe, LHe supply pipe, cooing pipes Vacuum vessel extension (1.2 m) Additional thermal shields of 5K and 80K Sliding C-clamp supports and sensors, etc Modification of coupler ports on vacuum vessel Connection parts between the couplers and the ports
C 2 3 KEK-BL cavities 1 KEK-LL cavities 2 DESY cavities 2 FNAL cavities Module A Additional components between support legs and tabs for LL cavity Additional flange for connecting the input coupler of LL cavity to the coupler port on the vacuum vessel No modification of Module A vacuum vessel Module B Same as case 1
C 3 4 KEK-BL cavities 4 cavities with DESY, FNAL and 1 KEK-LL cavities Module A No requirement Module B Re-designing the helium vessel of LL cavity to be matched to FNAL and DESY cavities Same items as Case-1, however, for three types of cavity packages
C 4 4 KEK- BL cavities 2 DESY cavities 2 FNAL cavities Module A No requirement Module C (Short Type III) No modification of STF-module B. Short vacuum vessel and cold mass by INFN (complete matching between cavities and cold-mass. KEK should make attachments of the assembly tools well functioned under the STF infrastructure by helps of DESY and FNAL groups. Connection bellows and flanges are supplied by DESY and FNAL.
C5 4 KEK- BL cavities 2 DESY cavities 2 FNAL cavities Module A No requirement Module C (Short Type III) No modification of STF-module B. Short vacuum vessel , cold mass and components by KEK KEK need all drawing for constructing the cryomodule.
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S1-Global cavity module combination

• Plan C4 and C5 are technically preferable
• No additional work for Module A, B ( except
  module connections )
• KEK will optimize the selection of cavities
  within module A
• Type III design can be used for Module B ( name
  it Module C).
• Minor modification is required, and the design
  must be checked. (LHe supply pipe position and
  cross-section design.)
• International collaboration more widely (INFN
  participation)
• KEK will have experience of Type-III. (3 regions
  have the same opportunity for assembly of the
  same cryomodule.)
• Need more consideration
• Conflict on schedule of STF-2 work.
• Production schedule of cavity-packages in each
  region.
• More consideration and discussion on module B
  modification or new module C production.

30
S1 Global Module-C
By Don Mitchell
31
?
Completing the design of S1-Global 6 months The
combination of cavities for S1-Global should be
decided in 2008.
Manufacturing components 6 months
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C4 and C5
Design modification and check
INFN Cold mass and vacuum vessel construction
13 months from T0
DESY cavities production tests
Clean room work at STF
FNAL cavities production tests with HTB
Time of starting work with INFN is critical.
Clean room work and assembly to Cryomodule at STF
FNAL cavities production tests without HTB ??
Clean room work and assembly to cryomodule at STF
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end