1. HTS and LTS Magnet Design and Prototyping for RAON
Do Gyun Kim
Institute for Basic Science

2. Contents Layout of IF separator HTS dipole & quadrupole magnet
LTS dipole & quadrupole magnet
Prototyping of HTS & LTS coil
Conclusions

3. Layout of IF separator Dipole magnet (8)
Beam
Dump
Wedge
Degrader
Pre Separator
Main Separator
High radiation region
Dipole magnet (8)
- Magnetic rigidity: ~10 Tm
Quadrupole magnet triplet (17)
- Field gradient: ~15 T/m
Sextupole magnet (14)
- Maximum field strength: 20~50 T/m2

4. HTS & LTS magnet
In the front end of the pre-separator, so called target region, magnets are under the influence of high radiation.
Magnets would be subjected to high radiation heat loads, and it should be resistant to the radiation damage.
In the target region, we plan to use superferric dipole and quadrupole magnets based on the high-Tc superconducting (HTS) coils to remove radiation heat more efficiently at the temperature of 20~50 K.
High radiation region: Superferric magnet based on the HTS coil
- HTS dipole magnet (1)
- HTS quadrupole magnet (6)
- Resistive sextupole magnet (2): Mineral insulated cable
Other site: Superferric magnet based on the low-Tc superconducting (LTS) coil
- LTS or Resistive dipole magnet (7)
- LTS quadrupole magnet triplet (15)
- LTS sextupole coil (12): Winding on the cold bore tube of LTS quadrupole magnet triplet

5. Top view of dipole magnet
Magnetic rigidity of the dipole magnet is chosen to be 10 Tm considering the upgrade plan of beam energy of the driver linac to 400 MeV/u for uranium beam.
Dipole magnets have a bending angle of 30 degree, bending radius of 6 m, and a maximum field of 1.7 T. The pole gap and width are designed to be 150 mm and 600 mm, respectively.
Parameters
Value
Bending angle
30 deg
Bending radius
6 m
Maximum field
~1.7 T
Pole gap
150 mm
Pole width
600 mm
Yoke length
3.6 m
Yoke width
1.8 m
Yoke height
1.3 m
Yoke mass
~50 tons
Top view of dipole magnet

6. Quadrupole magnet
Five different types of quadrupole magnet are considered.
Aperture sizes were determined according to beam optics, and will be further optimized along with the results of prototyping and magnetic field mapping.
LTS quadrupole magnets share the same design besides the magnet length.
Q-magnet
HQs
HQ1
HQ2
LQ1
LQ2
Type
HTS
LTS
Number of magnet 1 3 2 30 15
Warm bore radius (mm)
120
170
Yoke length (mm)
480
450
800
Field gradient (T/m) 20 14 16

7. HTS dipole magnet
A warm iron HTS dipole magnet will be used in the target region.
In the current design each coil is composed of two layers of the same pancake windings.
Parameters
Value
Bend angle
30 deg
Bend radius
6 m
Pole gap
150 mm
Coil size
(2 layer)
750 mm2
(30*25)
One turn length
~8.1 m
Total current
~120 kA
Maximum field
~1.7 T
Max stored energy
~0.57 MJ

8. HTS dipole magnet cooling
Coil winging
- Double layer of pancake winding
- D-shaped (no negative curvature)
Coil vessel
- Protect and support the windings
- He gas channel for cooling
- Conduction cooling by using He gas
- Coil vessel will be wrapped with MLI
Support
- Ti rods support the coil vessel
- 14 supports: 6 (horizontal), 8 (vertical)

9. Bmax in the Coil (Bmod, Bn)
HTS Quadrupole magnet
Three layers of pancake winding of HTS coil with each section area of 480 mm2 are included in the cryostat.
The magnet pole was shaped to accommodate the cryostat.
Parameters
Value
Pole tip radius
170 mm
Yoke outer radius
500 mm
Yoke length
450 mm
Coil overall length
650 mm
Coil size
(3 layer)
1440 mm2
(40*12*3)
Total current
~315 kA
Max field gradient
~15 T/m
Max stored energy
~400 kJ
Bmax in the Coil (Bmod, Bn)
4.7 T (Bmod)
3.3 T (Bn)

10. HTS Q-magnet Cooling
HTS coils and coil support structure are cooled to reduce the cold mass.
Conduction cooling by using He gas of 20~50K.
Currently cryostat design is similar to that developed at BNL for FRIB
BNL design of HTS Q-magnet [1]
Cross section of HTS quadrupole magnet
[1] IEEE Trans. Appl. Supercond, vol. 21, pp. 1888, 2001

11. LTS dipole magnet
Design parameters of LTS dipole are similar to those of the HTS dipole magnet.
Required total current is 125 kA, and the maximum stored energy is 0.6 MJ.
The LTS coil of dipole magnet will be cooled by using liquid helium.
Parameters
Value
Coil size
900 mm2
(30*30)
Total current
~125 kA
Maximum field
~1.7 T
Max stored energy
~0.57 MJ

12. Resistive dipole magnet
Hollow conductor coil will be used for water cooling.
Required total current is 115 kA, and the maximum stored energy is 0.5 MJ.
Maximum power consumption will be about 220 kW when the coil packing fraction (f) is assumed to be 0.5.
(f: the ratio of conductor area to the gross area of coil made of copper wire)
Parameters
Value
Coil size
324 cm2
(18*18)
Total current
115 kA
Maximum field
~1.7 T
Max stored energy
~0.46 MJ
Max power
(packing fraction=0.5)
~220 kW

13. LTS Quadrupole magnet
We plan to construct 15 triplets of same design to reduce the construction cost and time.
A sextupole coil will be wound on the cold bore tube of a triplet for chromatic aberration correction.
Parameters
Value
Pole tip radius
170 mm
Warm bore radius
120 mm
Yoke outer radius
480 mm
Thickness of yoke
200 mm
Yoke length (LQ1, LQ2)
450, 800 mm
Coil size
1500 mm2
(30*50)
Length of coil (LQ1, LQ2)
650, 1000 mm
Mass of yoke (LQ1, LQ2)
2.3, 3.9 ton

14. Cryostat for LTS Q-magnet triplet
A cold iron LTS quadrupole magnet triplet is placed in one cryostat, and it is cooled by using liquid helium.
Two types of cryostat are considered for actual installation.
- Dewar type (external LHe supply), Stand-alone type (cryocooler)
Prototype of cryostat will use two GM cryocoolers 4K)
Estimation of LHe (4K) heat load of cryostat
Parameters
Value
Shield radiation
1.2 W
Support
link
0.2 W
He port
0.9 W
Current
lead
0.4 W
Total
2.7 W

15. Design of Quadrupole magnet
For the prototype of LTS quadrupole magnet, three types of designs having different pole and coil shapes were studied to minimize multi-pole components.
The ratio of integrated dodecapole field to the integrated quadrupole field along the magnet axis at the radius of 120 mm was compared.
The shape of type B shows a smaller overall variation in the ratio of integrated dodecapole field to the integrated quadrupole field.
Solid line
Dashed line
Type
Pole
Coil A
Hyperbola
Rectangular RT B
Modified C
Modified RT
Type
Int(B6)/Int(B2)
Int(B10)/Int(B2) A
-0.2% ~ 0.9%
-0.01% ~ 0.2% B
-0.4% ~ 0.5%
-0.03% ~ 0% C
-0.4% ~ 0.7%

16. Prototyping of HTS coil
One or two HTS coils for quadrupole magnet will be prototyped to ensure the technique of coil winding and to study quench properties and quench protection.
For the prototype of HTS coil, 2G HTS wire manufactured by SuNam, a domestic company, will be used.
In the HTS coil winding, we plan to co-wind a metal tape made of such as stainless steel for insulation.
HTS tape of SuNam
Superconductor
GdBCO
Substrate
Hastelloy
Width
12mm
Thickness
0.1 mm
77K
~400A
Architecture of SuNam 2G HTS wire

17. Radiation damage study of HTS wire
Proton beam irradiation test on the HTS tape was carried out at KIRAMS (Korea Institute of Radiological & Medical Sciences)
- Beam energy: 30 MeV, Current: 20 uA, Size: ~ Φ3cm
- Width of HTS tape: 4 mm
- Beam irradiation time: 3, 15, 30, 60, 120 min
(equivalent operation time: 0.5, 2.5, 5, 10, 20 year, Radiation dose: ~10 MGy/year)
To study the radiation damage on the HTS wire, critical current of HTS tape will be measured soon.

18. Prototyping of LTS coil
Prototype of LTS quadrupole and sextupole coils being manufactured to ensure the technique of coil winding and coil encapsulation. Quadrupole coil is a racetrack type, and sextupole coil is a saddle type.
A LTS quadrupole magnet will be prototyped by end of this year.
We chose rectangular NbTi wire manufactured by Bruker for the prototype of LTS coil. The bare size of NbTi wire is 1.2x0.8 mm2, and the Cu/Sc ratio is 5.3.
Sextupole coil (Saddle type)
Quadrupole coil (Racetrack)

19. Conclusions & Future plans
The designs of superconducting magnets in the IF separator for the RISP have been studied.
In the high radiation region, high temperature superconducting dipole and quadrupole magnet will be used. Besides the high radiation region, resistive or LTS dipole and LTS quadrupole magnet will be used.
Optimization of the pole and coil shape to reduce the integrated multi-pole components in the operation field range has been carried out.
Prototype of HTS and LTS coil for quadrupole and sextupole magnet will be prepared and tested.
After testing a fully assembled LTS quadrupole magnet in the LHe dewar, cryostat containing a quadrupole magnet triplet will be constructed for magnetic field mapping.

20. Thank You for Your Attention