# Presentation: 184420

## Design and R&D Permanent Magnets for NLC

- James T Volk
- Fermilab

- James T Volk

## Magnet Team

- SLAC: Bobby McKee, C Rago, C Spencer
- LBL:    S Marks, K Robinson, R Schulter
- FNAL: B Fowler, V Kashihkin, S Makarov, V Tsvetkov, J Volk, K Ewald

- James T Volk

## Uses of Permanent magnets

- Automotive Industry
- Computer Industry
- Accelerators
- Wigglers
- Undulators
- Quads
- Correction Elements
- Fermilab Recycler

- James T Volk

## Types of magnet material

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## Fermilab Recycler

- 1 Dipole
- 141 Quadrupoles
- 385 Gradient
- 5 Lambertsons

- James T Volk

## Permanent magnet issues

- Strength
- Harmonics
- Temperature stability
- Life time

- James T Volk

## Gradient strength((measured - ideal)/ideal) *1000

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## Higher Harmonics((measured - ideal)/ideal) *1000

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## Temperature stability

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## Temperature Compensation

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## Life Time9.0 x 10-4 per decade

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## 20” Quad Grel comparison

- Difference in strength after 18 months

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## In a production environment it is possible to:

- Control Field Strength
- Control Harmonics
- Control Temperature Variation
- Achieve Time Stable Field
- Produce Magnets On time and at Budget with Minimal Staff

- James T Volk

## Process being followed for baseline designing -1

- ~5600 magnets of ~120 styles originally all electromagnets
- Need for cost reduction and enhanced reliability led us to consider which styles could be made as hybrid permanent magnets (= steel poles + permanent magnet material)
- Imposition of simple criteria led to ~57% of all magnets, comprising ~27 styles, being assigned as pms
- Need to quickly validate that
*a reasonably shaped* pm can meet the accelerator physics requirements
*the pm will cost less* than the electromagnet+power supply+cables

- James T Volk

## Process being followed for baseline designing - 2

- Developed set of analytical flux equations to test magnets
- Checked Dipoles, C-dipoles, Quads, sextupoles
- Use EXCEL spread sheets with adjustable parameters to calculate size of magnets and amount of magnetic material required
- Made cost estimated for magnets
- Developed generic fabrication scenario
- Currently proving theses designs with 2D models in PANDRIA

- James T Volk

## Selection Criterion

- Quadrupole
**Bp < 11 kG**
**Bore Radius < 3 cm**
**Effective Length >> Aperture**
**Tuneability < 20 % Bp Nominal**
**Radiation: Aperture too small (TBD)**
**Beam Based Alignment: < 1 micron center shift**
**We are experimentally determining if this criteria can be achieved.**
- Dipole
**Bp < 13 kG**
**Half Gap < 2 cm**
- Sextupole
**Bp < 5 kG**
**Bore Radius < 3 cm**
**Effective Length >> Aperture**

- James T Volk

## NLC Quad Specifications

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## Corner tunerRods rotate to adjust field

- Rotating tuning rods

- Permanent magnets

- Pole

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## Wedge QuadRods rotate to adjust field

- Rotating magnets

- Wedge Magnets

- Pole

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## Wedge Quad Pole

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## SSW and Wedge Quad

- Wire stages

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## Wedge Quad in Cooler

- Picnic Cooler

- Heater blanket

- RDT

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## Un Compensated Magnet

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## Temperature vs. Gradient

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## Gradient ((measured-average)/average)*10000

- FWHM  3 units

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## Center StabilityDifference between 5 successive measurements

- FWHM 2 microns

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## Calculated vs.Measured Field

- PANDIRA predicts 0.62 Tesla at 0.005 m for 0.202 m
- This is 25.05 Tesla
- SSW measures 21.02 Tesla
- 16% lower than predicted
- Br and Hci in calculation
- needs to be adjusted

- James T Volk

## Wobble0.65 Gauss per micron

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## FWSQ001

- Close to desired field
- Have 20% tunable range
- Need to measure Center stability during adjustment
- The FNAL test stand is capable of these measurements

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## Sliding Shunt

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##  Shunt Quad on SSW stand   

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## Shunt Quad Test

- Gradient    101.7 Tesla\meter
- Maximum field   32.96 Tesla
- Minimum Field   28.50  Tesla
- 13.5% change
- Center Shift ~ 11 microns
- From Max field to Min field

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## Rotational quad

- Permanent magnets

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## Issues to test

- Center Stability
- Strength
- Repeatability in Tuning
- Radiation Hardness

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## Status

- Have tested the conventional quad
- Have one wedge quad at SLAC and one at FNAL both under test
- Sliding quad assembled at FNAL under test
- Corner tuners parts ready for assembly

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## Electro Quad	

- A conventional electromagnetic quad has been made at SLAC
- Using water cooled copper coils
- EDM poles
- Current is 120 to 150 amps

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## Electro Quad Field 

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## Electro Quad Center

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## Conclusions

- Permanent magnets can be used for NLC
- Some applications will save money by simplifying installation and operations
- There are two prototype PM Quads that  are close to meeting the specifications
- Two more prototypes on the way
- More testing is needed

- James T Volk