Technical Issues Related to Superconducting Accelerator Modules Lutz Lilje DESY -MPY- Lutz.Lilje@desy.de

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 18.01.2019

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]). Lutz Lilje DESY 18.01.2019

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 18.01.2019

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 18.01.2019

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 18.01.2019

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 18.01.2019

Cavities I Reliability of procedures needs improvement (e.g. EP nine-cells) Lutz Lilje DESY 18.01.2019

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 18.01.2019

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 18.01.2019

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 18.01.2019

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 18.01.2019

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 18.01.2019

Processing on test stand Lutz Lilje DESY 18.01.2019

Processing in CHECHIA Lutz Lilje DESY 18.01.2019

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 18.01.2019

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 18.01.2019

HOMs Detalied specification of HOM coupler Detailed specification for assembly/integration Improved design for easier mechanical assembly exists Lutz Lilje DESY 18.01.2019

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 18.01.2019