Technical Issues Related to Superconducting Accelerator Modules

1
Technical Issues Related to Superconducting
Accelerator Modules

• Lutz Lilje
• DESY -MPY-
• Lutz.Lilje_at_desy.de

2
Overview

• This is intended to be a summary of a series of
  discussions on
• Clean room assembly
• Cavity String
• Cavities
• Coupler
• HOMs
• Module, Tuner -gt Danilo Barni next talk
• This talk should serve as an introduction to the
  list of research topics and priorities (presented
  by D. Reschke)

3
Quality control (QC) and Quality assurance (QA)

• Definitions

'What is the difference between quality assurance
and quality control? Quality assurance is a
management or oversight function it deals with
setting policy and running an administrative
system of management controls that cover
planning, implementation, and review of data
collection activities and the use of data in
decision making. Quality control is a technical
function that includes all the scientific
precautions, such as calibrations and
duplications, that are needed to acquire data of
known and adequate quality. (Environmental
Protection Agency, www.epa.gov) 'The anatomy of
"quality assurance" is very similar with that of
quality control. Each compares actual quality
with the quality goal. Each stimulates corrective
actions as needed. What differs is the prime
purpose to be served. Under quality control, the
prime purpose is to serve those who are directly
responsible for conducting operations... Under
quality assurance, the prime purpose is to serve
those who are not directly responsible for
conducting operations but who have a need to
know... In this sense, quality assurance has a
similarity to insurance...(p.2.13, Juran Quality
Handbook from usenet- LL).
4
Clean room assembly

• Goal is to get a reliable preparation of
  cavities
• Low Field emission (FE)
• All components should be functioning and at the
  right place
• Note The clean room is of course not the only
  place where particles causing FE might
  introduced.
• Current status
• One-cells are usually not FE-loaded (exceptions
  exist unfortunately), regardless from which clean
  room is used
• Multi-cells are much more suffering from FE
• There exist multi-cells which are FE-free at very
  high gradients
• This means, the reliability of preparation needs
  improvement for a large machine, but there is no
  fundamental obstacle (like available technology)

5
Current clean room QC

• Currently already quite a few things are done
• QC of air filters
• QC of low pressure water circuit to some degree
  (resistivity, particle count)
• QC of clean room equipment like gloves
• QC of BCP acid
• Leak checks during a variety of assembly steps

6
Improvements needed

• QC for the high pressure rinsing system
• Online measurement of the particles which are in
  the waste water draining from the cavity
• Capillary should be introduced that allows to
  measure the particle content behind the last
  filter on the high pressure side
• QC of the TOC and bacteria needs to be
  (re-)introduced
• QC of assembly needs improvement
• QC of delivered parts (e.g. pick-ups, couplers,
  bellows etc.) before they enter the clean room
• some assembly/treatment procedures need to be
  revised (e.g. flange assembly) or developed (e.g.
  how do we treat electropolished cavities with a
  tank?)

7
Cavity String

• Several points need investigation
• Bellows show signs of damage
• Leaks on cavity flanges (vertical
  test/reassemblies in the string) -gt better
  reliability needed
• Position (probably in the center) and type of
  magnet package
• Type of pick-ups (likely to use Ti-pick-ups which
  show higher reliability
• Number of valves (Strahlschieber)
• Alignment procedure
• Components need to be developed to be compatible
  with clean room assembly (e.g.cleaning)
• Cold BPM
• TW absorber for higher order modes

8
Cavities I

• Reliability of procedures needs improvement (e.g.
  EP nine-cells)

9
Cavities II

• Surface treatment
• Detailed investigation of multi-cell
  electropolishing
• Optimum parameter set
• EP on cavities with tank
• EP on half-cells/dumb-bells for easier/cheaper
  preparation
• Other cleaning techniques
• CO2 cleaning
• Oxipolishing
• Material
• Detailed specification
• 800C vs 1400C furnace treatment
• 800C furnace parameters and literature study
  (e.g. SNS heat treatment)

10
Cavity III

• Processes
• Full description of cavity preparation and
  assembly
• Flanges
• have bee improved from the very first design
• still need higher reliability
• full investigation including more experiments on
• mechanical/thermal simulations
• surface quality
• improve current design
• larger torque (crush of the seal like SNS/CEBAF)
• improve assembly procedures further and develop a
  detailed specification for QC

11
Coupler I

• Assembly of the coupler has proven to be a very
  crucial item
• Problems on module 1 and 3
• Contact inner and outer conductor during assembly
• Copper deposits on niobium port of the cavity
• Difficult to understand the reason for misaligned
  antennas -gt investigation needed

12
RF Main Coupler Assembly Problems - Copper on
Niobium

• RF Main Coupler
• Inner conductor
• made from Cu
• Soft due to additional
• soldering
• bent / misaligned

Problems discovered and identified during the
disassenbly of module 3 Strong hint on similar
problems with cavities 2 and 6 of module 1
Cu
13
Coupler II

• Processing of couplers
• lengthy procedure on the module
• can be reduced by
• In-situ heating of the coupler (like in CHECHIA)
• pre-processing on test stand and proper storage
  under nitrogen

14
Processing on test stand
15
Processing in CHECHIA
16
Processing times
where treatment time
1st test on test stand after baking 70 130 h
CHECHIA stored under N2 and baked in situ 20 60 h (exeptional100 h)
Module, 8 couplers in parallel stored under N2 1800 h
17
Coupler III

• Leaks
• one leak in the copper material of the antenna
• e- pick up (see above)
• 2 ceramic leaks
• Fermi coupler after operation
• Ceramic brazing
• Handling
• Dents in bellows
• Design
• Bellow alignment
• 4K shield connection
• less/other sensors but still reliable operation

18
HOMs

• Detalied specification of HOM coupler
• Detailed specification for assembly/integration
• Improved design for easier mechanical assembly
  exists

19
Conclusion

• Already, its a long list...
• we need a priorization
• we need also an estimation of the effort
  necessary
• Proposal
• First try to normalize What time would it cost
  to do something assuming the available
  infrastructure (TFF and other labs) is
  completely available?
• In the second step try to be realistic and try to
  distribute workload
• ... and will be even longer -gt Danilo!