1. NCSX Vacuum Vessel Fabrication
21st IEEE/NPSS Symposium on Fusion Engineering (SOFE 2005)
MFE Engineering, NCSX and EAST
Oral III.e – Sequoyah 3
4:00 PM
Mike Viola 1, T. Brown 1, P. Heitzenroeder 1, F. Malinowski 1, W. Reiersen 1,
L. Sutton 1, P. Goranson 2, B. Nelson 2, M. Cole 2, M. Manuel 3, D. McCorkle 3
1 Princeton Plasma Physics Laboratory, PO Box 451, Princeton NJ USA
2 Oak Ridge National Laboratory, Oak Ridge, TN USA
3 Major Tool and Machine, Inc., Indianapolis, IN 46218, USA
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2. NCSX Vacuum Vessel Fabrication
Introduction
The National Compact Stellarator Experiment (NCSX) is being constructed at the Princeton Plasma Physics Laboratory (PPPL) in conjunction with the Oak Ridge National Laboratory (ORNL).
A key element of this device is its highly shaped 3/8” thick Inconel- 625 vacuum vessel.
The vessel is being fabricated by Major Tool and Machine, Inc. (MTM) in three identical 120º vessel segments, corresponding to the three NCSX field periods, in order to accommodate assembly of the device at PPPL.
The vessel must have a total leak rate less than 5  10-6 t-l/s, magnetic permeability less than 1.02μ, and its contours must be within 0.188” (4.76 mm).
The VVSA’s are scheduled for completion in January 2006.
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3. NCSX Vacuum Vessel Fabrication
Stellarator Symmetry
Six identical 60° segments form the NCSX vacuum vessel.
120º vessel segments are formed by welding two 60º segments together.
Each 60º segment is fabricated by welding ten press-formed panels together over a collapsible welding fixture which is needed to precisely position the panels.
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4. NCSX Vacuum Vessel Fabrication
Process Summary
Ten Kirksite die sets (20 total – upper and lower) cast and machined
Ten Panels formed per 60° segment
Press – anneal – press – local rework
Upper and Lower 5 panel sets joined on a fixture to form 60° ½ segments
Each 60º upper and lower ½ segments welded together over a collapsible welding fixture.
Two 60º segments welded together on a fixture to form 120º segments.
Port holes bored and ports installed
Leak checked and thermal cycled
Ports cut off and shipped.
Reassembled at PPPL after Modular Coils installed.
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5. NCSX Vacuum Vessel Fabrication
Prototype Vacuum Vessel (PVVS)
Prototype vacuum vessel
Solicit interest
develop techniques
Statement of Work defined
manufacturing development activities for the 120º Vacuum Vessel Sub-Assembly (VVSA) and
production of a full-scale 20º prototype vacuum vessel segment (PVVS).
These activities were also meant to give the fabricator the experience needed to develop and submit a firm fixed price and schedule proposal for producing the three VVSA units.
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6. NCSX Vacuum Vessel Fabrication
Prototype Vacuum Vessel (PVVS)
Two companies were chosen that submitted competitive solutions with the most promising technique.
Both companies produced prototype vacuum vessels and Major Tool and Machine, Inc. was chosen for the production of the VVSA based on performance.
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7. NCSX Vacuum Vessel Fabrication
Panel Segmentation
Ten panel segmentation scheme was chosen for each 60° segment for optimization of complexity of forming vs. weld distortion.
60 panels (6 sets of 10) are required for the entire NCSX vacuum vessel.
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8. NCSX Vacuum Vessel Fabrication
Panel Forming
A set of ten kirksite dies were cast and machined
Press – anneal – press – local rework
Gauges facilitate rework
Rubber and wood carefully placed to make minor corrections
Each panel is a work of art
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9. NCSX Vacuum Vessel Fabrication
The 60° fixture is ingeniously designed with many features
Allows for the mounting of the ten panels in two 5-panel sections upper and lower.
Keyed and segmented to allow for easy disassembly after the 60° segment is welded.
Provides stiffness necessary to hold shape and control distortion of the segments during welding.
Bolted together as one assembly or as two individual upper and lower assemblies.
Cutouts allow a person to stand and weld within the fixture as well as allow for seams to be made which cross the fixture plates.
60° fixture
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10. NCSX Vacuum Vessel Fabrication
60° Fixture
Panels are tacked together in a three panel and a two panel configuration on the upper or lower fixture.
Partial assemblies are then joined into one complete upper or lower five panel segment.
Upper assembly
Lower assembly
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11. NCSX Vacuum Vessel Fabrication
Metrology measurements taken with a Laser Tracker CMM
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12. NCSX Vacuum Vessel Fabrication
60° Segments
Upper and lower segments are mounted back onto the complete 60° fixture and welded into their final configuration.
This completes the formation of a 60° segment.
Completed 60° segments
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13. NCSX Vacuum Vessel Fabrication
120° Fixture
The 120° fixture also has some unique features serving multiple needs. 
Positions and joins two 60° degree vessel segments together:
datum reference monuments,
strategically placed adjusting rods,
personnel access for completing weld.
It is designed to uniformly support the highly shaped vessel surfaces (minimizing gravity induced distortion) 
a separate center support structure
provide support and rigidity for machining the port holes
provide support during the installation of the port extensions and vacuum testing operations.
120° fixture
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14. NCSX Vacuum Vessel Fabrication
120° Fixture
The 120° fixture allows two 60° segments to be aligned and a best fit analysis is performed using Verisurf© software.
Alignment and distortion control are critical.
The final weld joins two 60° segments to form one completed 120° shell.
The port holes are bored on a 5-axis mill.
Completed 120° Segment
Boring Port Holes
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15. NCSX Vacuum Vessel Fabrication
Final Steps
The port extensions are welded on, leak checked, cut off within 1” of the vessel surface (provides stiffness as well as a weld stub) at MTM and then reattached at PPPL, to accommodate assembly of the close-fitting modular coils that surround the vessel.
The vessel is joined at assembly by welding custom machined 8” (20.3 cm) wide spacer “spool pieces.”
Port 2
Port 6
Port 15
Port 7
Port 11
Port 5
Port
NBI
Port 16
Port 10
Port 4
Port 8
Port 9
Port 18
Port 17
Port 12
Port 3 -
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16. NCSX Vacuum Vessel Fabrication
Acknowledgment
Thank You
Sketches and photographs provided by Major Tool and Machine Inc.
This research is supported by the U.S. DOE under contract DE-AC02-76CH03073 with Princeton University and contract DE-AC05-00OR22725 with UT-Battelle, LLC.
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