Vacuum Quality Assurance in Practice

Transcription

1 Vacuum Quality Assurance in Practice Matthew Cox Head of Vacuum Diamond Light Source 1

2 Topics What is Diamond Light Source? Why is vacuum QA important to Diamond? QA in vacuum vessel procurement Diamond vacuum performance 2

3 What is Diamond Light Source? The UK national synchrotron facility Harwell Campus in South Oxfordshire Generates brilliant beams of light, from infra-red to X-rays, which are used in a wide range of applications, from structural biology through fundamental physics and chemistry to cultural heritage Construction began in early 2003 Operational on schedule in January 2007 Currently 16 beamlines operational Can ultimately host up to 40 beamlines The largest ultra-high vacuum (UHV) system in the UK 3

4 Diamond layout Booster synchrotron 3 GeV electron storage ring 562m circumference <10-9 mbar 100 MeV Linac Front end Beamline 4

5 Aerial view 5

6 Why ultra-high vacuum <10-9 mbar? To reduce scattering of circulating electrons by residual gas molecules If the pressure is too high Beam lifetime is reduced Unwanted Gas Bremsstrahlung radiation is produced Effects scale as Z 2 so high Z gases (Ar, Kr etc) must be minimised Hydrocarbons cause contamination of x-ray mirror optics Halogen-containing compounds (particularly fluorine) can poison Non-Evaporable Getter (NEG) pumps and coatings 6

7 Diamond Storage Ring Vacuum Equipment Construction components 500 complex vacuum vessels and fabricated components 2,000 vacuum construction components 20,000 welded joints 10,000 flange joints 150,000 flange bolts Pumps 500 ion pumps 50 titanium sublimation pumps 50 NEG cartridge pumps 8 NEG coated vessels Instrumentation 200 IMGs and 200 Piranis 80 RGAs Valves 50 RF shielded valves 50 all-metal gate valves to front ends / absorbers 150 right-angle manual valves 7

8 Why is vacuum QA important at Diamond? Large quantities of vacuum vessels and components. One rogue component can contaminate a whole section Vacuum construction time of only 12 months. Failures disrupt the build process 30 year reliability with little or no maintenance Full user program operating 24/7 delivering ca 5000 hours user beam in Beam interruptions to be avoided. No access to the storage ring during operations! In 2010 only 6 shutdowns planned for major work 8

9 Aspects of vacuum QA Functional Specification Design Procurement Build and installation Commissioning Operation Systems health monitoring Scheduled and unscheduled maintenance Development 9

10 Range of vacuum procurement Standard construction components Standard or modified standard active components = gauges, RGAs, valves, pumps, control units, cables etc Custom vacuum vessels, ranging from simple spool pieces right through to complex quadrupole vessels and dipole and crotch vessels Major systems complete front ends, superconducting RF cavities, beamline components such as monochromators, Linear accelerator 10

11 Dipole and crotch vessel Material 316LN stainless steel walls 316LN flanges OFHC copper absorbers CuBe spring contacts Processes TIG welding e-beam welding Explosion bonding Vacuum brazing Quantities Full prototype Production run 52 off (26 pairs) over 12 months 11

12 Vacuum QA Specification (1) Issued with every tender for vacuum vessels and assemblies Short version for vessels; longer version for assemblies Electronic copies available on request ( Vessels supplied clean and baked out (250 C 48h) r eady for installation Most small components such as elbows, tees, gauges, RGAs are not baked at the supplier for cost reasons but are almost always baked and leak tested at Diamond before installation 12

13 Vacuum QA Specification (2) Good vacuum design practice Materials Process and test equipment Flanges and fasteners Manufacturing including welding and brazing Cleaning Bakeout QA records including material and item traceability and test records Acceptance testing 13

14 Pressure Ranges Pressure Range Leak Rate Specific Outgassing Rate (mbar) (mbar l/s) (mbar l/s cm -2 ) Low Vacuum Medium Vacuum High Vacuum (HV) Very High Vacuum (VHV) Ultra High Vacuum (UHV) Extreme High Vacuum (XHV) < < < Default is UHV 14

15 Vacuum Cleanliness General Contaminants [ 1] Oil Contaminants [ 2] Chlorine Contaminants [ 3] CF Contaminants [ 4] (% of total P) (% of total P) (% of total P) (% of total P) Low Vacuum < 5 < 1 < 1 < 1 Medium Vacuum < 2 < 0.1 < 0.1 < 0.1 High Vacuum (HV) < 1 < 0.1 < 0.1 < 0.1 Very High Vacuum (VHV) < 0.5 < 0.1 < 0.1 < 0.1 Ultra High Vacuum (UHV) < 0.1 < 0.05 < 0.05 < 0.05 Extreme High Vacuum (XHV) < 0.01 < < < [1] The sum of AMUs 39, 41-43, 45 and above, excluding those listed elsewhere. [2] The sum of AMUs 69 and 77. [3] The sum of AMUs 35 and 37. [4] The sum of AMUs 19, 31, 50 and

16 Weld and Brazing QA BS EN : 2000 or equivalent Welding plan Weld procedure specifications Welder qualifications Weld inspection records Internal or full penetration external welding Cleaning before welding Backing gas protection from oxidation 16

17 Dimensional Inspection 17

18 Final Acceptance Test Visual inspection Vacuum Leak test before, during after bake Outgassing rate / ultimate pressure RGA before, during, after bake Dimensional inspection Hydrostatic, flow rate, He leak test on water circuits Electrical test on feedthroughs Magnetic permeability Functional test moving components, bakeout system Electrical safety tests, e.g. bakeout heaters Full documentation electronic format 18

19 Diamond Storage Ring Vacuum Performance (1) 3 years into operation, storage ring 2342 A.h of accumulated beam dose at 3 GeV Static pressure (no beam) 2.6 x mbar Dynamic pressure (250 ma) 5.6 x mbar Specified dynamic pressure < 10-9 mbar Gas composition according to RGA is mainly H 2, the balance mainly CO Beam current Storage ring pressure 19

20 Diamond Storage Ring Vacuum Performance (2) Cell 12 Arc RGA 1 10% 1% Adjacent to superconducting wiggler which cannot be baked 98% H 2, 2% CO, also CH 4, CO 2, H 2 O + some low level contaminants at the 0.05% level 0.1% 20

21 Challenges going forward Construction Phase Small number of large contracts Small number of experienced, wellequipped suppliers Few staff specifying vacuum items at Diamond Vacuum QA relatively easy to keep track of Operations and Development Phase Large number of small and medium sized contracts Some large contracts, e.g. complete front ends Large number of suppliers with varying experience and facilities Many different staff specifying vacuum items at Diamond with varying experience and knowledge Vacuum QA harder to keep track of 21

22 Experience from the build phase Suppliers (usually) start out intending to do a good job but it doesn t always work out that way Suppliers almost always deliver late, sometimes very late reasons many and varied Suppliers don t like telling you bad news unless they absolutely have to and as late as possible A visit concentrates minds and usually finds out something unexpected Suppliers don t always read and/or understand the specification Suppliers go through good and bad patches. Past good/bad performance doesn t guarantee future performance It is important to establish good working relationships and trust. Trust is hard gained and easily lost Always be reasonable and don t ask for the impossible too often 22

23 SR build (1) Vessel pre-assembly at the supplier Vessel dimensional inspection at the supplier Vessel delivery to Diamond 6 m long vacuum string assembly on trolley Vacuum string lifting into the bakeout oven Vacuum bakeout 23

24 SR build (2) Girder integration Girder installation Vacuum interconnections Girder installation complete Installing the 5 m long Al ID vessel for beamline I06 Storage ring complete 24

25 Summary A large number of vacuum vessels and components were procured for the Diamond project A great deal of hard work on the part of Diamond staff and the suppliers and their sub-contractors went into vacuum QA Attention to detail is very important and pays dividends As a result, the vacuum performance of the Diamond vacuum system is well within the specification 25

26 Thank you Conference Organisers Vacuum and Engineering Groups staff at Diamond Ron Reid for writing the first version of the Vacuum QA manual 26

27 Questions for discussion How does the Diamond approach compare with other purchasers of vacuum vessels? From a vacuum supplier perspective, what is Diamond like to work with? How could Diamond manage vacuum suppliers and contracts better and help its suppliers to deliver? 27