# Presentation: 522960

## NCSX Design Overview

**M. Cole, G. Jones, P. Fogarty, P. Goranson, B. Nelson, D. Williamson (ORNL)**
**T. Brown, H-M. Fan, P Heitzenroeder, W. Reiersen (PPPL)**
**NCSX PVR**
**March 27, 2001**
**PPPL**

## A robust concept for stellarator core has been developed

- 8 Dec 00

## Modular coil requirements

**Meet performance requirements**
**1.7 T scenario with 0.46s flattop**
**1.2 T scenario with 1.24s flattop**
**2.0 T with reduced external iota**
**15 minute rep rate (5 minute rep rate for short pulse)**
**Provide flexibility**
**Independent control of modular and PF coils provided**
**Variable background TF field**
**+/- 1 mm assumed for winding accuracy**
**Coils must provide access for tangential NBI, RF, vacuum pumping, diagnostics, and personnel access**
**Limit conductor current to ~ 24 kA peak to match with existing TFTR power supplies**

- 8 Dec 00

## Modular coil configuration

**21 coils, 3 field periods**
**Symmetry coils pulled radially out 0.8m for tangential NBI access**
**Coils wound with flexible cable conductor into cast-and-machined forms**
**Coils pre-cooled to LN****2**** temperature to allow high current density**

- 8 Dec 00

## Continuous shell forms robust structure

**Shell consists of individual modular coil forms that are bolted together**
**Penetrations for access are provided wherever needed**
**Preliminary stress analysis of shell has been performed**
**Stresses are well within allowables except for a few localized “hot spots”**
**Local problems can be solved with minor changes in local thickness**

- 8 Dec 00

## Modular coils wound with flexible cable directly on coil structure

**Parameters:**
-  Coil Envelope = 2 x 110 x 37 mm
-  Current / Coil = 649-kA @ 2-T
-  Number of Turns = 32
-  Nominal current / turn = 20.3  kA
-  Conductor Size = 13 x 16 mm
-  Net Current Density = 14-kA/cm2
-  Total peak power ~ 55 MW
**Flexible cable used to wind coil**

- 8 Dec 00

## Modular coil manufacturing sequence

- 77”

- Rough casting

- Features are machined

- Conductor wound directly into structure

- Auxiliary support clamps are installed

**Continuous support for strength and accuracy of windings**
**Shell segments repeat 6 times for coils 1 thru 3, 3 times for coil 4**

- 8 Dec 00

## Vacuum vessel requirements

**Vessel must be bakeable to 150 C**
**Low permeability (< 1.02 nominal goal)**
**Provide as large a volume as possible for plasma shape flexibility and power and particle handling systems**
**Provide support for internal components such as internal liner, trim coils, magnetic sensors**
**Provide access ports for diagnostics, vacuum pumping, heating systems, and personnel access**

- 8 Dec 00

## Vacuum vessel design concept

**Shell material****	****	****Inconel 625**
**Thickness****	****	****.375 inch**
**Time constant****	****	****< 10 ms**
**Total wt w/ports****	****~ 12000 lbs**
**Bolted joints connect field periods**
**Traced with He gas lines for heating (to 150C) and cooling**
**Combination Microtherm and Solomide foam insulation between VV and cold mass**

**15 ft.**

- 8 Dec 00

## Access for tangential NBI

**Up to 4 neutral beams in combinations of co- and counter-**
**Vacuum pumping through NB ducts**

- 8 Dec 00

## Diagnostic and personnel access

**87 separate ports for ~100 different diagnostics**
**The number and sizes of ports appear to match diagnostic requirements**
**Geometric requirements for specific diagnostics will be addressed in more detail during conceptual design**
**Personnel access available through NBI or adjacent large ports**

- 8 Dec 00

## Vacuum vessel fabricated from formed panels

- Individual panels

- Half field period

- Full field period with port stubs

- 8 Dec 00

## PFC requirements

**Basic requirements **
**Carbon based, bakeable to 350C**
**NBI armor, limiters needed day 1 (at minimum)**
**3 MW for 0.5 s**
**2 cm from plasma inboard, 10 cm outboard **
**	****(*****TBR, working to maximize plasma-wall separation*****)**
**Provide penetrations, accommodate in-vessel diagnostics mounted on VV**
**Upgrade requirements**
**Full coverage of surfaces with carbon**
**12 MW for 1.2 s**
**Provision for divertor**

- 8 Dec 00

## PFC design concept

**Staged implementation planned**
**Initial coverage with ****low Z tiles**** mounted on poloidal ribs to form array of poloidal limiters**
**Panels for NB armor**** will also be provided**
**Full coverage provided by mounting ****molded carbon fiber composite (CFC) panels**** on poloidal ribs**
**Panel size based on advice from  BFG aerospace (~ 60 cm square, 1 cm thick)**
**Ribs are separately cooled / heated with He gas for bakeout (350C) and normal operation**
**Ribs are registered toroidally  to VV but allowed to grow radially and vertically**

- Poloidal ribs

- CFC panels mounted on poloidal ribs

- 8 Dec 00

## Trim coils

- Provided to mitigate field errors on m=5 and m=6 resonant surfaces
- Located close to inboard and outboard midplane at v=0 cross-section
- Mounted off vacuum vessel, behind liner
- Canned for vacuum compatibility

- 8 Dec 00

## TF Coils

**21 coils provide +/- 0.3 T**
**Mounted on radial support plates**
**Wound from hollow copper conductor**
**Pre-cooled to LN****2**** temperature (like modular coils)**

- 8 Dec 00

**Notes:**
Make labels bigger

## PF Coils

**4 pairs of PF coils provide inductive current drive and plasma position and shape control**
**Number and placement to be optimized in conceptual design**
**1.7T scenario requires 1Wb with a plasma current ramp rate of 3MA/s**
**PF coils located outside modular and TF coils, supported off radial plates**
**Wound from hollow copper conductor, glass-epoxy insulation**
**Pre-cooled to LN****2**** temperature (like modular and TF coils)**

- 8 Dec 00

## Cryogenic coils enclosed in a common cryostat

**Cryostat design uses commercial concept - ****s****ubstructure sprayed with urethane foam**
**Inexpensive construction facilitates maintenance access**
**Holes provided for all vacuum vessel port extensions**
**Silicon rubber “Gortiflex” boots to seal between vessel port extensions and cryostat**
**8” thickness reduces heat leaks to 2kW but still will require local heaters/blowers to avoid condensation**

- 8 Dec 00

## Modular and TF coils and VV will be pre-assembled in field periods

- Vessel period rotated into bore of symmetry coil

- 3-coil assemblies added to each end to complete 7 coil set

- Port extensions added to vessel to complete field period subassembly

**Adequate space exists in NCSX test cell for pre-assembly of field periods**
**TFTR test cell might be an even better place for pre-assembly (more space for pre-assembly, more space in NCSX test cell for final assembly)**

- 8 Dec 00

## Field periods are assembled on machine structure in NCSX test cell

- Field period lowered onto machine base in position 18 inches radially outward

- 3 field periods prior to radial assembly step

- Field periods connected after radial motion, PF coils raised/lowered into position

- 8 Dec 00

## Slide 21

- 8 Dec 00

## PPPL is an excellent site for NCSX 

- 8 Dec 00

## There is ample room for NCSX in the combined PLT and PBX test cells

- NCSX Test Cell

**The combined test cell can easily accommodate four beamlines**** **
**Field periods can be pre-assembled in either the NCSX or TFTR test cell**

- Dimensions in inches [mm]

- 8 Dec 00

## The PBX and PLT control rooms will be refurbished into a single large control room

**Space is available in adjacent rooms for offices and computers**

- A portion of the former PBX-M Control Room

- 8 Dec 00

## NCSX will re-use the 6MW PBX-M neutral beam system

**The four beamlines will be stored and refurbished at D-site**
**Two of the four beamlines will be installed initially and supply 3MW of heating power - the other two beamlines can be added later on**
**NCSX must accommodate 6MW of ICRF heating in addition to the 6MW of NBI**
**7-8MW of RF power (20-30MHz, suitable for mode conversion RF heating) is available from the 4 FMIT sources located in an area adjacent to the NCSX Test Cell**

- 8 Dec 00

## TFTR power supplies will be re-used for the modular, TF, and PF Coils

- TFTR Power Supply Building 	       TFTR Power Supplies

**TFTR power supplies will be shared with NSTX**
**Switching can be accomplished in a matter of minutes**
**PBX Robicon power supplies will be used for the trim coils**

- 8 Dec 00

## Existing cooling systems will be re-used

**The de-ionized water cooling system will serve the neutral beams, diagnostics, vacuum pumps, and vessel cooling**
**The PBX-M neutral beam helium refrigerator will supply helium for the neutral beams**
**A new 15,000 gallon LN2 tank will be located next to the existing tank for cooling the cryogenic (modular, TF, and PF) coils and structure**

- 8 Dec 00

## Priorities for conceptual design have been established

**Involve industry**
***Fund***** participation for manufacturing studies, R&D and prototypes**
**Improve modular coil geometry**
**Improve manufacturability, reduce cost, reduce J, eliminate sharp bends, improve access (18 coil solution)**
**Optimize design for flexibility**
**Optimize VV shape, liner configuration, and PF coil design**
**Optimize design for access**
**Address geometric requirements of diagnostic access, incorporate RF scheme into the engineering design, improve personnel access.**
**Finalize requirements**
**Finalize requirements well in advance of CDR (April ’02)**
**Establish defensible and achievable dimensional tolerances**
**Develop “bottoms up” schedule estimate**
**Need to determine project duration, critical path activities**
**Refine cost estimates**
**Pursue cost effective design and manufacturing solutions**

- 8 Dec 00

## Summary

**We have a ****robust design concept**** that meets performance requirements**** **
**We have an ****excellent site**** for this experiment with ample space and valuable site credits**** **
**We have ****plans for improving the design****, making it easier and cheaper to fabricate, and sharpening our cost and schedule estimates for a CDR in April ‘02**** **

- 8 Dec 00