permanent magnet diploes and quadrupoles for ffags

9/19/2005 1

Permanent Magnet Diploes and Quadrupolesfor FFAGs

Jinfang Liu and Peter Dent

Electron Energy Corporation

924 Links Ave, Landisville PA 17538

Phone: 717-898-2294 Fax: 717-898-0660

9/19/2005 2

(1) Permanent Magnet Overview

(2) Some Design Considerations

(3) Radiation Effect

(4) Permanent Magnet Dipoles

(5) Permanent Magnet Mangles

(6) Permanent Magnet Quadrupoles

(7) Summary

Outline

9/19/2005 3

Types of Commercial magnets

Nd-Fe-B MagnetsNd-Fe-B Magnets

Sm-Co MagnetSm-Co Magnet

Strontium FerriteStrontium Ferrite

Barium FerriteBarium Ferrite

PermanentMagnets

PermanentMagnets

Bonded Magnets(Rubber/Plastic)Bonded Magnets(Rubber/Plastic)

MetalMagnets

MetalMagnets

Ferrite MagnetsFerrite Magnets

RE MagnetsRE Magnets

Alnico MagnetsAlnico Magnets

Bonded Ferrite MagnetsBonded Ferrite Magnets

Bonded RE MagnetsBonded RE Magnets

SmCo 1:5SmCo 1:5

SmCo 2:17SmCo 2:17

Other MagnetsOther Magnets

Overview

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(BH)max versus Maximum Operating Temperature

Overview

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Some factors to consider:

(1) Magnetic performance(2) Corrosion resistance(3) Thermal stability(4) Radiation resistance(5) Magnetization direction(6) Manufacturability(7) Cost

Permanent Magnet Selection

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Typical magnetic properties, in terms ofenergy product, of selected commercialmagnets:

Sintered Nd-Fe-B magnets: up to 50 MGOe

Sintered Sm-Co magnets: up to 32 MGOe

Isotropic bonded Nd-Fe-B magnets: up to 10 MGOe

Sintered ceramic magnets: up to 4 MGOe

Cast Alnico magnets: up to 9 MGOe

Permanent magnets --- properties comparison

9/19/2005 7

Maximum operating temperature of sintered magnets

Magnets Maximum Operating Temp.*

NdFeB with iHc =12 kOe 80°C




Conventional SmCo magnets 300°C

EEC24-T400 magnets (patented & available) 400°C



Rare Earth Magnets

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15

20

25

30

35

40

45

50

100 200 300 400 500 600

Maximum Operating Temp. (oC)

(BH

) max

(MG

Oe)

NdFeB

SmCo

(BH)max Versus Maximum Operating Temperature

Rare Earth Magnets --Properties vs. Temperature

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Long-term Thermal Stability of SmCo Magnetsat 300°C in Air

0 4000 8000 12000 16000 20000 24000 28000-10

-9

-8

-7

-6

-5

-4

-3

-2

-1

0

1 Year

MagnetDimensions:

1 cm OD x 1 cm THK

2 Years 3 Years

T550C-16MGOe w/coatingT550C-16MGOeT500C-20MGOeT400C-24MGOeT330C-27MGOeT250C-31MGOe

Time at 300°C (Hours)

Mag

netic

Irre

vers

ible

Loss

es(%

)

-10

-9

-8

-7

-6

-5

-4

-3

-2

-1

0

9/19/2005 10

High temperature magnets

DoD initiated the More Electric Aircraft program,which requires magnets with maximum operatingtemperature more than 400°C

Funded by the Department of Defense, a series ofsintered SmCo 2:17 magnets were developed at EECwith maximum operating temperature as high as 550°C

These patented SmCo UHT magnets were introducedto the industry in 1999.

Rare Earth Magnets --- Materials Selection

9/19/2005 11

SmCo Rare Earth Magnets

550178.6EEC16-T550

500219.3EEC20-T500

40024.510.2EEC24-T400

3002710.8EEC2:17-27

2503111.6EEC2:17-31

Max. operating temp(oC)

(BH)max(MGOe)

Br (kG)(kG)

PM Grades

9/19/2005 12

Nd-Fe-B sintered magnets

Key features:

Highest (BH)max available (up to 50 MGOe)

Less expensive than Sm-Co magnets

Corrosion resistance is not good

Special coating is required

Maximum operating temperature is very low compared toSmCo magnets

Rare Earth Magnets --- Materials Selection

9/19/2005 13

Nd-Fe-B Type Rare Earth Magnets

18031-3411.3-11.7N33UH

12040-4312.8-13.2N42SH

10043-4613.2-13.6N45M

7043-4613.2-13.8N45

7048-5114-14.5N50

Max. operating temp(oC)

(BH)max(MGOe)

Br (kG)(kG)

PM Grades

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Permeance Coefficient Pc

Also known as load line or operating point

It is related to the dimensions of the magnets and the associatedmagnetic circuit

In the magnetic circuit, a magnet will operateat a specific point on its extrinsicdemagnetization curve:

Pc = Bd/HdBr

Bd

HdHcPc=Bd/Hd

Some Design Considerations

9/19/2005 15

Why straight-line demagnetization curves?

Application with load line #1: Both magnets are okay to use

Application with load line #2: Only magnet #1 is suitable

Bd1

Normal demagnetizationcurve for magnet #1

load line 2

Br

Hc 0

Knee

load line 1

Bd2

Hd1 Hd2

Br

Hc

Normal demagnetizationcurve for magnet #2

9/19/2005 16

The effects of radiation on permanentmagnets was studied at EEC under a NASASTTR Contract

All Samples have a L/D ratio of 1.25

Permanent Magnets Studied:EEC T500 and T300 SmCo 2:17 magnets

Nd-Fe-B Magnets

Radiation Source: Ohio State UniversityResearch Reactor

Radiation Effect

OSU Reactor

Samples in quartz tubes

9/19/2005 17

Permanent Magnets and Radiation Effect

C.H. Chen, J. Talnagi, J.F. Liu, P. Vora, A. Higgins and S. Liu,IEEE Trans. Magn. 41(2005)3832

9/19/2005 18

-100

-80

-60

-40

-20

0

20

1.E+13 1.E+14 1.E+15 1.E+16 1.E+17 1.E+18 1.E+19 1.E+20

Neutron Fluence (neu/cm2)

Mag

neti

cF

lux

Lo

ss(%

)L/d = 8.9

L/d = 4.8

L/d = 4.4

L/d = 3.1

L/d = 2.0

L/d = 0.9

L/d = 0.4

1013 1014 1015 1016 1017 1018 1019 1020

Cost et al.[ 7]

Recorded T =78°C, TL waslikely ~ 160°C

(Hci >17kOe)

If TL Tc, theloss will be100% for allthe samples

E = 0.1 to 10 MeV

Nd-Fe-B

J.R. Cost et al, IEEE Trans. Mag.24 (3), 2016-2018 (1988).

Working Point and Radiation Effect

9/19/2005 19

Radiation Effect

The major radiation damage is caused by radiation-induced thermal spikes

The dominant factor for radiation tolerance is thermalstability, which is related to the following factors:

(1) Curie temperature of permanent magnets

(2) Working point of permanent magnet in the system

(3) Intrinsic coercivity

9/19/2005 20

Permanent Magnet Dipoles

Magnets

Magnets

Return Path

d Bg = –––––BmAm

k1Ag

Am =Magnet area perpendicular to the direction of magnetization;Bm =Flux density of the magnet corresponding to the operating pointof the demagnetization curve;Bg =Flux density desired in the air gap;Ag =Cross section area of the air gap perpendicular to the flux lines.

The Air Gap Flux Density Is A Lot LowerThan The Br Of The Permanent Magnets

9/19/2005 21

Permanent Magnet Dipoles

Halbach PM DipoleStructures:

Bg = Br ln(OD/ID)ODID

There is no upper limit for air gap flux density inHalbach dipole structures according to aboveequation. But in reality it would be limited by:

(1) The realistic size

(2) The demagnetization effect

9/19/2005 22

Flux Density Map Vector Map

Halbach Dipole Example

9/19/2005 23

Vector MapFlux Density Map

Halbach Dipole Structure

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0o Position

Magnetic Mangles

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45o Position

Magnetic Mangles

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90o Position

Magnetic Mangles

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135o Position

Magnetic Mangles

9/19/2005 28

Combination of magnetic mangles and Habachstructures can make the air gap flux density adjustableto some degree

9/19/2005 29

4 Tesla PM prototypeHalbach cylinder wasmade in Japan.*

EEC has produced manyHalbach structures for avariety of applications.

Sintered SmCo or highHci NdFeB magnets aregood choices

Halbach Dipole for FFAGs

*M. Kumada et al, PAC2001, 3221.

9/19/2005 30

A Example of Halbach PM Quadrupole

9/19/2005 31

Adjustable magneticquadrupoles as reportedby Fermi lab andSLAC*:

Diametricallymagnetized SmCo 2:17tuning rods

Tuning rods rotationchanges the strength offield gradient

* J. T. Volk et al, PAC2001, p217

Adjustable Magnetic Quadrupoles

9/19/2005 32

Summary

Permanent magnet dipoles and quadrupoles canhave high air gap flux density if designed withHalbach principles.

Innovative designs can make the air gap fluxdensity adjustable.

Permanent magnet selection might include trade-offs between cost and performance.

SmCo magnets are far superior to NdFeB magnetswith respect to radiation resistance.

9/19/2005 33

Contact Information

Jinfang Liu, Director of TechnologyPeter Dent, Director of Sales and MarketingMichael Walmer, President

Electron Energy Corporation924 Links Ave.Landisville, PA 17538(717) 898-2294 Phone(717) 898-0660 [email protected]

permanent magnet diploes and quadrupoles for ffags

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