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9/19/2005 1
Permanent Magnet Diploes and Quadrupolesfor FFAGs
Jinfang Liu and Peter DentElectron 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
Permanent Magnets
Permanent Magnets
Bonded Magnets(Rubber/Plastic)
Bonded Magnets(Rubber/Plastic)
Metal Magnets
Metal Magnets
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
9/19/2005 4
(BH)max versus Maximum Operating Temperature
Overview
9/19/2005 5
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
9/19/2005 6
Typical magnetic properties, in terms of energy product, of selected commercial magnets:
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
NdFeB with iHc =17 kOe 120°C
NdFeB with iHc =20 kOe 150°C
NdFeB with iHc =25 kOe 180°C
Conventional SmCo magnets 300°C
EEC24-T400 magnets (patented & available) 400°C
EEC20-T500 magnets (patented & available) 500°C
EEC16-T550 magnets (patented & available) 550°C
Rare Earth Magnets
9/19/2005 8
15
20
25
30
35
40
45
50
100 200 300 400 500 600
Maximum Operating Temp. (oC)
(BH
) max
(M
GO
e)
NdFeB
SmCo
(BH)max Versus Maximum Operating Temperature
Rare Earth Magnets --Properties vs. Temperature
9/19/2005 9
Long-term Thermal Stability of SmCo Magnets at 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
Magnet Dimensions:1 cm OD x 1 cm THK
2 Years 3 Years
T550C-16MGOe w/coating T550C-16MGOe T500C-20MGOe T400C-24MGOe T330C-27MGOe T250C-31MGOe
Time at 300°C (Hours)
Mag
netic
Irre
vers
ible
Los
ses
(%)
-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 operating temperature more than 400°C
Funded by the Department of Defense, a series of sintered SmCo 2:17 magnets were developed at EEC with maximum operating temperature as high as 550°C
These patented SmCo UHT magnets were introduced to the industry in 1999.
Rare Earth Magnets --- Materials Selection
9/19/2005 11
SmCo Rare Earth Magnets
PM Grades Br (kG) (kG)
(BH)max(MGOe)
Max. operating temp (oC)
EEC2:17-31 11.6 31 250
EEC2:17-27 10.8 27 300
EEC24-T400 10.2 24.5 400
EEC20-T500 9.3 21 500
EEC16-T550 8.6 17 550
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 to SmCo magnets
Rare Earth Magnets --- Materials Selection
9/19/2005 13
Nd-Fe-B Type Rare Earth Magnets
PM Grades Br (kG) (kG)
(BH)max(MGOe)
Max. operating temp (oC)
N50 14-14.5 48-51 70
N45 13.2-13.8 43-46 70
N45M 13.2-13.6 43-46 100
N42SH 12.8-13.2 40-43 120
N33UH 11.3-11.7 31-34 180
9/19/2005 14
Permeance Coefficient Pc
Also known as load line or operating point
It is related to the dimensions of the magnets and the associated magnetic circuit
In the magnetic circuit, a magnet will operate at a specific point on its extrinsic demagnetization 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 demagnetization curve for magnet #1
load line 2
Br
Hc 0
Knee
load line 1
Bd2
Hd1 Hd2
Br
Hc
Normal demagnetization curve for magnet #2
9/19/2005 16
The effects of radiation on permanent magnets was studied at EEC under a NASA STTR 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 University Research 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
netic
Flu
x 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 was likely ~ 160°C
(Hci >17kOe)
If TL ≥ Tc, the loss will be 100% for all the 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 thermal stability, 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 Lower Than The Br Of The Permanent Magnets
9/19/2005 21
Permanent Magnet Dipoles
Halbach PM Dipole Structures:
Bg = Br ln(OD/ID)ODID
There is no upper limit for air gap flux density in Halbach dipole structures according to above equation. But in reality it would be limited by:
(1) The realistic size
(2) The demagnetization effect
9/19/2005 22Flux Density Map Vector Map
Halbach Dipole Example
9/19/2005 23Vector MapFlux Density Map
Halbach Dipole Structure
9/19/2005 24
0o Position
Magnetic Mangles
9/19/2005 25
45o Position
Magnetic Mangles
9/19/2005 26
90o Position
Magnetic Mangles
9/19/2005 27
135o Position
Magnetic Mangles
9/19/2005 28
Combination of magnetic mangles and Habachstructures can make the air gap flux density adjustable to some degree
9/19/2005 29
4 Tesla PM prototype Halbach cylinder was made in Japan.*
EEC has produced many Halbach structures for a variety of applications.
Sintered SmCo or high Hci NdFeB magnets are good 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 magnetic quadrupoles as reported by Fermi lab and SLAC*:
Diametrically magnetized SmCo 2:17 tuning rods
Tuning rods rotation changes the strength of field gradient
* J. T. Volk et al, PAC2001, p217
Adjustable Magnetic Quadrupoles
9/19/2005 32
SummaryPermanent magnet dipoles and quadrupoles can
have high air gap flux density if designed with Halbach principles.
Innovative designs can make the air gap flux density adjustable.
Permanent magnet selection might include trade-offs between cost and performance.
SmCo magnets are far superior to NdFeB magnets with respect to radiation resistance.
9/19/2005 33
Contact InformationJinfang 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]