1

NCSX Modular coil winding pack

To shim or not to shim?

NCSX WBS 1 Engineering Meeting

July 7, 2004

•What is requirement?

•What is baseline winding pack design?

•What are alternate winding pack designs?

•How will we figure out what to do?

•What do we need to do now?

2

What is winding requirement?

Winding current center must be within .06 inches of theoretical winding

If current center is more than 30 cm from plasma, some relaxation may be possible.

3

Tolerance budget apportioned in thirds

Element Tolerance budget

Comment

Winding form +/- 0.01 in. Baseline on drawing

Copper cladding TBD Could be used to improve winding form tolerance if shims are allowed

Insulated conductor size +/- 0.01 in. Based on NEEWC input

VPI process TBD Assumed to be small

Total for Coil Winding +/- 0.02

Assembly of coil in field period

+/- 0.02 Adjusted to best fit, coil-to-coil with custom shims

Assembly of field periods +/- 0.02 Adjusted to best fit with custom shims

Total tolerance +/- 0.06 in.

(+/- 1.5 mm)

Minimum value, may be relaxed according to location around winding

1/3 for winding

1/3 for field period assembly

1/3 for final machine assembly

4

Baseline design: accuracy achieved by shimming

Each conductor layer can be custom shimmed

1.5 mm radius

tolerance on winding center

Custom shim layer

to layer

Custom shims adjust flanged joints between adjacent coil winding forms

Custom lateral shim

Winding position continuously adjusted to AVOID TOLERANCE STACKUP Form machined to high accuracy (Flanges to +/- 0.01 in, Contours to +/- 0.01 in) Windings placed to high accuracy relative to each other and the form Final position of coil form in assembly adjusted for optimum fit

5

Baseline design: What are issues?

Each conductor layer can be custom shimmed

1.5 mm radius

tolerance on winding center

Custom shim layer

to layer

Custom lateral shim

Measurement of each layer could be time consuming What fraction of winding needs custom

shimming? What fraction can use standard shim?

Measurement tools may not work properly on insulation layer

Other issues

6

Lumped shim concept Estimate total keystoning at each position along

winding pack Shim between tee and ground wrap Mid-course correction, if necessary

Variation: perform trial winding to quantify shim thickness

Pros Less work measuring and shimming

Cons Must be able to predict keystoning a priori Hard to gage compressibility of winding pack

and shims – are turns evenly distributed?

What are alternate winding pack concepts?

No keystoning, max shims

Max keystoning, no shims

7

No-shim – use winding form as is Take what we get, no shims

Pros Less work measuring and shimming

Cons Art says this won’t work – islands too big

What are alternate winding pack concepts? (2)

current center shifts, but stellarator symmetry preserved

Current center, desired

Current center, actual

8

No-shim – variable section winding form Predict keystoning machine winding form with variable

section to put winding center in correct place without shims

Pros Less work measuring and shimming

Cons Must be able to predict keystoning a priori Winding pack size varies, so clamps,

cladding, chill plates must vary

What are alternate winding pack concepts? (3)

No shims, winding form maintains current center

9

Other ideas

Pros

Cons

What are alternate winding pack concepts? (4)

10

Need experience winding prototypical coil to select shimming technique Twisted racetrack will arrive this week Conductor has been ordered and is in house Ground wrap, insulation finalized Cladding, chill plate ideas are firming up Clamps are on order Lead block design nearly complete

Try two shimming approaches: Baseline on one side of coil Alternate approach on other side of coil (lumped shim) Trial winding first to determine lumped shim size

How do we make decision?

11

Order more conductor, if needed: Chrzanowski Figure out correspondence between layers of glass and

apparent thickness of shim: Chrzanowski et al Get drawings of new lead block design to PPPL: Fogarty Get drawings of new cladding to PPPL: Hargrove Test Romer arm scanner on insulated conductor: Raftopolous Order studs for stud welder: ? Make fixture for locating studs: ? Review TRT test objectives: Chrzanowski, Reiersen, Gettelfinger Finish test plan: Nelson

What do we do next?

12

Summary

We need to finalize winding pack shimming scheme

Trials on twisted racetrack will provide input

Recommend both the baseline concept and alternate concepts be included in winding / shimming trials on twisted racetrack