Design of DC septum magnets based on measurements and 3D calculation of

an R&D septum magnet

for Rapid Cycle Synchrotron of J-PARC

　 Masao Watanabe,

Accelerator Group, JAERI

J-PARC overview RCS and the septum magnets overview

Comparison of measurements and

3D calculation of an R&D septum magnet 3D calculation of RCS septum magnets

Outline

Overview of J-PARC

181MeV (400MeV)

RCS and Septum magnets

Injection

Dump

Extraction

3 Septum magnets

2 Septum magnets

2 Septum magnetsCircumference: 348m

3 GeV(B=12.8Tm)

181 MeV(B=2.03Tm)

Septum magnets of RCS are required for

7 Septum magnets [2(injetion) 、 3(extaction) 、 2(dump)],

large aperture for low losses of high intensity beam (1 MW),

high durability to minimize the maintenance after the high activation.

RF acceleration

Design parameters of septum magnets

Injection Dump Extraction 　

　 Unit SEPI-1 SEPI-2SEPD-

1SEPD-

2SEPE-

1SEPE-

2SEPE-

3R&D(SEPE-

3)

number of magnets

　 1 1 1 1 1 1 1 1

max. field T 0.487 0.439 0.501 1.086 0.695 1.402 1.659 1.13

effective length mm 1400 800 1000 1000 900 1000 1000 1000

gap width mm 370 348 368 622 336 521 743 760

gap height mm 136 136 136 140 223 189 166 142

wave form 　 DC 　environment 　 Air (not in vacuum) 　septum thickness mm 87 45 51 340 34 90 260 185

material of core 　 Electromagnetic soft iron (JIS SUYP-1; block) 　excitation current A 6246 5650 6787 5603 11176 12312 11035 12800(MAX)

turn number of coils

turn 8 8 8 24 10 16 20 10

max. voltage of coil

V 20 14 19 53 33 28 17 10

cooling of coils 　 Water

J-PARC overview RCS and the septum magnets overview

Comparison of measurements and

3D calculation of an R&D septum magnet 3D calculation of RCS septum magnets

Outline

Schematic diagram of the R&D septum magnet

Upper view

Side view (without edge shield)

90097 163

4040

1010

SUS tickness

Mag

net

ic s

hie

ld t

ick

ne

ss(S

oft

-iro

n b

loc

k)

Magnetic shield tickness (Silicon steel sheet:0.5tmm*20)

Mag

net

ic s

hie

ld t

ick

ne

ss(S

oft

-iro

n b

loc

k)

1022

142

760

1200

Coil(Copper bar):10turn Core(Soft-iron block)

440

Photographs of the septum magnet and the measurement

Septum magnet

Hall device probe

3D stageDC power supply

Photograph of the coil inside the shield

Ceramic is employed against the high radiation for the electronic insulation of the coils.

Schematic diagram of cross section of the gap

OPERA3D modelWhole view Core and coil

Coil (2 turns)Magnetic Shield (Silicon steel)

Core (soft-iron)

Magnetic Shield (soft-iron)Core (soft-iron)

(1/2 model)

Comparison of measurements and 3D calculation

S(mm)

S(mm)

Leakage field was not agreed.

Field distribution (By) at X=0

Magnetic field in the gap was agreed.

90097 163

4040

1010

Magnetic shield

Core

Coil

Magnetic field in the gap.

Leakage field.

X(mm)

Leakage field distribution (By) at X=-334mm(Distance of 18mm from the septum shield)

-1.2 104-1 104-8000

-6000

-4000

-2000

0

2000

-150 -100 -50 0 50 100 150

By(Gauss)

S(cm)

MeasurementCalculation

Why?-150

-100

-50

0

50

100

-150 -100 -50 0 50 100 150

By(Gauss)

S(cm)

Edge shieldposition

Calculation

Measurement

Upper view

BH curves

1.6 104

1.62 104

1.64 104

1.66 104

40 50 60 70 80 90 100

By(Gauss)

X(cm)

Calculation 2

Calculation 1

Effects of BH curves near the saturation

Leakage field distribution (By) at X=-334mm

-150

-100

-50

0

50

100

-150 -100 -50 0 50 100 150

By(Gauss)

S(cm)

Calculation 2

Calculation 1

Measurement

Edge shieldposition

0

0.5

1

1.5

2

0 5000 1 104 1.5 104 2 104

H(A/m)

B(T

)

Calculation 1 (Catalog data)

Calculation 2 (The near lower limit of the standard)

Near saturation

-1.5 104-1 104-5000

0

5000

1 1041.5 1042 104

-50 -25 0 25 50 75 100

By(Gauss)

X(cm)

Calculation 2Calculation 1

Field distribution (By) on the median plane at S=0

Schematic diagram of the core

Cross sectional area of the bolt holes are

only 0.17% of the one of the return yoke.

Effects of the bolt holes near the saturation

Leakage field distribution (By) at X=-334mm

Distribution of B on the surface of the core

-150

-100

-50

0

50

100

-150 -100 -50 0 50 100 150

By(Gauss)

S(cm)

Calculation 2

Calculation 3

Measurement

Edge shieldposition

0

5000

1 104

1.5 104

2 104

-50 -40 -30 -20 -10 0 10 20 30 40 50

|B|(Gauss)

S(cm)Edge of the yoke Edge of the yoke

Distribution of B near the surface (Y=500mm) at center of the bolt holes

440mm:Return yoke thickness

33:Bolt holes

900m

m

0.014T

2.24T

Effects of the bolt holes near the saturation 2

1.6 104

1.65 104

1.7 104

1.75 104

-40 -20 0 20 40

|B|(Gauss)

S(cm)Edge of the yoke Edge of the yoke

Distribution of B near the surface (Y=500mm) at center of the bolt holes

Distribution of B on the surface of the core

0.014T

2.24T

we have to operate the core in the low magnetic field region which means the permeability is high enough. Our standard is 1.5 Tesla in maximum to be operated.

Attention points in design of RCS septum magnets

1.To suppress the leakage field,

When we operate not only the shield but also the return yoke at near saturation region.

2. When we cannot to obtain the shield or the yoke thickness enough,

(by weight limit, space limit and so on)

we have to take into account effects of dispersion of BH curves and bolt holes.

Design parameters of septum magnets

Injection Dump Extraction 　

　 Unit SEPI-1 SEPI-2SEPD-

1SEPD-

2SEPE-

1SEPE-

2SEPE-

3R&D(SEPE-

3)

number of magnets

　 1 1 1 1 1 1 1 1

max. field T 0.487 0.439 0.501 1.086 0.695 1.402 1.659 1.13

effective length mm 1400 800 1000 1000 900 1000 1000 1000

gap width mm 370 348 368 622 336 521 743 760

gap height mm 136 136 136 140 223 189 166 142

wave form 　 DC 　environment 　 Air (not in vacuum) 　septum thickness mm 87 45 51 340 34 90 260 185

material of core 　 Electromagnetic soft iron (JIS SUYP-1; block) 　excitation current A 6246 5650 6787 5603 11176 12312 11035 12800(MAX)

turn number of coils

turn 8 8 8 24 10 16 20 10

max. voltage of coil

V 20 14 19 53 33 28 17 10

cooling of coils 　 Water

Schematic diagram of the third extraction septum magnet

Side view (without edge shield) Upper view

100 100900

160

40

Ma

gn

eti

c s

hie

ld t

ickn

ess

(So

ft-i

ron

blo

ck

)

771.5742.5

1514

77

1.5

16

6

17

09

30

40

45

0

38

0

The gap between the coil has 1 mm slope.

Core(Soft-iron block)

Mag

net

ic s

hie

ld t

ickn

es

s(S

oft

-iro

n b

loc

k)

Coil(Copper bar):20turn

SUS tickness

Schematic diagram of extraction septum magnets

232.5

3.96°

51.6

3.1

61. 4

9. 55°

471.2

4

45

1.74°

141.5

Extraction septum 3

Extraction septum 2

Extraction septum 1

OPERA3D modelWhole view Core and coil

Coil (2 turns) Core (soft-iron)Magnetic Shield (soft-iron)

Core (soft-iron)

BH curves of soft iron

Field distribution (By) on the median plane

2D calculation and effects of BH curve

0

0.5

1

1.5

2

0 5000 1 104 1.5 104 2 104

H(A/m)

B(T

)

Calculation 1 (Catalog data)

Calculation 2 (The near lower limit of the standard)

-2 104-1.5 104-1 104-5000

0

5000

1 1041.5 104

-50 0 50 100 150

By(Gauss)

X(cm)

Calculation 2

Calculation 1

Not saturated in the shield

3SEPE3.3

F:\MASAO\MYDOCU~1\FILE\SUPERF~1\RFBUNC~1\3SEPE3~1.AM 2-27-2005 3:25:40

0

20

40

60

80

100

120

140

0

20

40

60

80

100

120

140

-60 -40 -20 0 20 40 60 80 100 120

More than 1.5T region.

Leakage field of the extraction septum 3

-5

-4

-3

-2

-1

0

1

-300-250-200-150-100 -50 0 50 100 150

By(Gauss)

S(cm)

End of the shield

Center of the core

Leakage field distribution (By) at the central orbit on the RCS

OPERA3D model

Central orbit on the RCS

BH curves of soft iron

0

0.5

1

1.5

2

0 5000 1 104 1.5 104 2 104

H(A/m)B

(T)

Calculation 1 (Catalog data)

Calculation 2 (The near lower limit of the standard)

Magnetic fields of an R&D septum magnet were measured and calculated by OPERA3D (TOSCA).The core was operate in high magnetic field region. This means the permeability is low. Leakage fields depended on not only the dispersion of BH curves but also bolt holes to fasten the return yoke.We obtained a standard ; the core should be excited less than 1.5 Tesla.On the basis of the results of the R&D magnet, the third extraction septum magnet was designed. The magnetic field in the core and the leakage field were estimated.

Conclusions