SSRF1 ALUMINUM ALLOY VACUUM CHAMBERS FOR SSRF L.X. Yin, D.K. Jiang, H.W. Du, X.L. Jiang SSRF Vacuum Group Shanghai National Synchrotron Radiation Center

SSRF2 CONTENTS Outline of SSRF vacuum system Aluminum Vacuum Chambers –Design –Fabrication of prototype –Test

SSRF3 Vacuum System Structure

SSRF4 Principle of Vacuum System Design Antechamber type structure Machined and welded aluminum alloy vacuum chambers SR photons are intercepted by OFHC photon stops except to beamline SR irradiate the photon stop surface in 10 ° angle Titanium sublimation pumps are located beneath the photon stops

SSRF5 Vacuum System Model

SSRF6 History of Aluminum Chambers Early 1970s Extrusion SPEAR, PF End of 1980s Antechamber extrusion SPring8, APS End of 1980s Machining + welding –Machining upper and lower halves out of aluminum plate and welding at the periphery ALS, PLS, SSRC

SSRF7 Requirements for SSRF Chambers A clean inner surface q ＜ 6.7× Pa.m 3 /s/m 2 Sufficient mechanical strength Deformation for BPM ＜ 0.03mm Flatness ＜ 0.5 mm Roughness ＜ 0.8 μ m Fit relative systems

SSRF8 Materials Aluminum alloy A5083-H321. –Nonheat treatable aluminum-magnesium alloy –A small amount of cold work –Stretched and stabilized –Good weldability and dimensional stability SS316L -- A6061-T6 explosion bonded plates –Checked by ultrasonic detector

SSRF9 Structural Design Different features on the external surface Support stages inside the chamber Enough space between the chamber and the magnets Conflat ® Flange with AL-SS transition material Helicoflex ® gaskets on BPM flanges Helicoil ® screws inside the screw holes High precision holes for survey Water-cooling channels in the chamber body

SSRF10 Chamber Structure (1)

SSRF11 Chamber Structure (2)

SSRF12 BM and Chamber

SSRF13 QM and Chamber

SSRF14 SM and Chamber

SSRF15 RF Shielded Flange

SSRF16 1m-long Chamber model

SSRF17 Machining Numerically controlled mill Dedicated milling cutters Water soluble metalworking fluid Spray cooling method No polish by sandpaper Constant temperature workshop

SSRF18 Machining Procedure Chamber piece –Blank the plate –Machine and weld the water - cooling channel –Rough machine the features –Release and keep free –Finish machine in two steps BPM hole –Rough machine –Assemble the two halves –Finish machine both of the BPM holes

SSRF19 Numerically controlled milling

SSRF20 Cleaning Purpose –Clean surface contamination –Eliminate the old surface layer –Form a new surface layer Procedure –Scrub, ALMECO 18, room temperature –Scrub, CITRANOX, room temperature –Scrub, ALMECO 18, ℃ –Rinse, distilled water –Dry, room temperature

SSRF21 XPS Test for Sample Element C O Al Oxide layer thickness Before clean 68.4% 23.6% 8.0% After clean 23.6% 71.2% 5.2% 61.7 Å

SSRF22 Welding AC TIG welding with filler Hand hold Surface protection from any contamination Humidity control in workshop Remove oxide layer Argon gas flowing inside chamber

SSRF23 Welding Structure Design

SSRF24 Welding Platform

SSRF25 TIG Welding for Chamber

SSRF26 Welding Crack

SSRF27 Dimensional Inspection Flatness (upper surface) 0.23 mm (bottom surface) 0.48 mm Max. error in transverse direction 1.4 mm Surface roughness (beam chamber) μ m (antechamber) μ m Max. deformation in vacuum load 0.28 mm

SSRF28 Max. Error in Transverse Direction

SSRF29 Vacuum Test Results Total leak rate （ Pa.m 3 /s ） ＜ 4.0 × Ultimate pressure （ Pa ） 4.9 × × Outgassing rate （ Pa.m 3 /s/m 2 ） 4.1 × RGA spectrum No contamination peak in Pa

SSRF30 Pumping Down Curve

SSRF31 Conclusion A complete process for the chamber prototype manufacture has been performed with acceptable dimensional accuracy and good vacuum properties. Many effects have been taken to solve corresponding problems. A lot of experiences have been accumulated. The large aluminum alloy UHV chamber for SSRF can be manufactured on domestic technology.

SSRF32 6m-long Chamber Prototype