1. Technical Issues Related to Superconducting Accelerator Modules
Lutz Lilje
DESY -MPY-

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 -> Danilo Barni next talk
This talk should serve as an introduction to the list of research topics and priorities (presented by D. Reschke)
Lutz Lilje DESY

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,
'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]).
Lutz Lilje DESY

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)
Lutz Lilje DESY

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
Lutz Lilje DESY

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?)
Lutz Lilje DESY

7. Cavity String Several points need investigation:
Bellows show signs of damage
Leaks on cavity flanges (vertical test/reassemblies in the string) -> 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
Lutz Lilje DESY

8. Cavities I
Reliability of procedures needs improvement (e.g. EP nine-cells)
Lutz Lilje DESY

9. Cavities II Surface treatment Material
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
800°C vs 1400°C furnace treatment
800°C furnace parameters and literature study (e.g. SNS heat treatment)
Lutz Lilje DESY

10. Cavity III Processes Flanges
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
Lutz Lilje DESY

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 -> investigation needed
Lutz Lilje DESY

12. Assembly Problems - Copper on Niobium
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
Lutz Lilje DESY

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
Lutz Lilje DESY

14. Processing on test stand
Lutz Lilje DESY

15. Processing in CHECHIA
Lutz Lilje DESY

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
(exeptional:100 h)
Module, 8 couplers in parallel
stored under N2
1800 h
Lutz Lilje DESY

17. Coupler III Leaks Handling Design
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
Lutz Lilje DESY

18. HOMs Detalied specification of HOM coupler
Detailed specification for assembly/integration
Improved design for easier mechanical assembly exists
Lutz Lilje DESY

19. Conclusion Already, it‘s 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 -> Danilo!
Lutz Lilje DESY