1. Concepts and Requirements for GIMM Structures
Thomas Kozub, Charles Gentile, Irving Zatz - PPPL
Mohamed Sawan - FTI UW
John Pulsifer, Mark Tillack - UCSD
Malcolm McGeoch - PLEX
Tom Lehecka - Penn State
POSTER HAPL-18, Santa Fe, NM
April 8 - April 9, 2008

2. Task Overview
A Conceptual Design for a Grazing Incidence Metal Mirror (GIMM) Structural Support System.
GIMM support project scope:
Each of the forty GIMM units consists of a mirror assembly contained within a long stainless steel vacuum duct
The duct which forms the beam line is contained within a large shielding block
All forty units are geometrically arranged around a shielding sphere centered around the target chamber
Together the GIMM units and shield sphere fill a volume of ~ 260,000m3.

3. Task Overview
The objective of this task is to develop a viable structural supporting system for the GIMM. The system design will need to address:
Static support of the GIMM structures to the facilities foundation.
Structural elements to maintain stability and alignment within the prescribed tolerances of the optical components.
A GIMM base that provides a mirror surface flatness to a quarter wavelength.
Elimination of high frequency vibration at GIMM that is beyond the dynamic tracking response of the steering mirrors.
Methods for mounting the GIMM within the vacuum beam duct at the several various required orientations.
Necessary features for the installation, adjustment, servicing and replacement of the GIMM components.

4. Drawing by Malcolm McGeoch

5. Facility structure supporting the individual GIMM shielding block and duct unit
GIMM base mounting inside beam line duct

6. GIMM Shielding Block Unit Section

7. GIMM Isolated Base Support

8. Initial Investigation of Structural Stability
Stainless Steel Frame FEA
Cylindrical Concrete Arch FEA

9. Steel Frame Supporting Large Mass
Large static deformations (>> 1-inch)
Numerous low frequency modes <10 Hz.
Prone to buckling and other instabilities
Conclusion – Unrealistically massive steel structures would be required to reduce these effects to an acceptable level
1st Mode << 1 Hz.

10. Cylindrical Concrete Arch Structure
Much smaller static
deformations
Much higher
frequency modes
Greater structural
stability
(Deformations are greatly
magnified for ease
of viewing)
Static Deformation
Delta Zmax = 0.06 in.
1st Mode = 6.5 Hz.

11. Integrated Facility Structure

12. Structurally Integrated GIMM Shield Blocks

15. Section View of Structure

16. Sources of Vibration
Reducing the sources of vibration to an minimum is as important as the attenuation of vibration.
Sources of vibration grouped by strength of coupling to the GIMM:
Sources acting directly on the GIMM.
IFE Process sources acting on the central core structure.
Facility and other sources dispersed throughout the plant.

17. Sources of Vibration Acting Directly on the GIMM
Thermal shock from target detonation
Impulse at rate ~5Hz
Thermal shock from laser pulse
Flow of GIMM coolant
Continuous source
Electromagnetic effects
To be determined

18. IFE Process Sources of Vibration Through the Facility Structure
Target detonation impulse
Ion, radiation and thermal impulse at ~5Hz
Magnetic Intervention field pulse
Field force response into structure at ~5Hz

19. Facility and Other Sources of Vibration
Rotating machinery: pumps, motors, etc.
Valves operating
Fluid flow through pipes
Transformers and other electrical devices
Elevators, cranes, trucks, doors
External sources through foundation
Atmospheric and Seismic

20. GIMM Dust and Contamination Issues
GIMM surface contamination from dust and other materials can compromise the performance of the mirror
The beam ducts will probably be a source of contamination
Counter gas flows may introduce excessive gas loading on the pumps and fuel recovery system to be effective
Electrostatic collection may be of some value

21. Path Forward /Future work
Complete static loading analysis
Detailed dynamic vibration analysis
Vibration isolator design
A further refinement in the integration of the GIMM shield units into the Infrastructure
GIMM cooling methods minimizing vibration
Access / Servicing features
Integrated facility structural details
Investigate dust mitigation and removal