1. Cyclotron System of RAON
RISP workshop on Acceleration systems, May 21, 2013
Cyclotron System of RAON
Jaehong Kim
IF·RF Team

2. 70MeV Cyclotron for ISOL System
Proton (70 MeV, 1 mA)
CW and pulsed beam operation
Driver for the ISOL target (Uniform Beam)
Cyclotron

3. Cyclotron and ISOL Fission Target Configuration

4. Specification of Commercial Cyclotrons
Categories
BEST
IBA
Sumitomo*
Local (RFT-30)
Accelerated particle
Proton (E_max, I_max)
35~70MeV, 1mA*
30~70MeV, 750uA
70MeV, 1mA
15~30MeV, 217uA
Energy spread
70MeV
70MeV
TBD
No. of Magnet Sectors 4
Sector Angle (degree)
50o
54o ~ 58o
45o
48o
Fields_ave (Hill, Vally)
1.6T, 0.12T
1.7T, 0.12T
1.7T, 0.5T
1.05T
RF System
No. of Dees 2
Dee Angle
35o
30o
39o
Harmonics
Frequency (MHz)
56.2 30 73
63.96
Dee Voltage (kV)
60 to 70 50
Injection System
Ion Source Type
multi cusp
Arc MultiCUSP/ECR
Volumic CUSP
Multi-CUSP
H- Current
15 ~ 20 mA
5mA
10mA
max. 10mA
Inflector
spiral
Extraction System
No. exit port/beam lines
2. / 4.
2. / 6.
2/4
Carbon foil (life time/uAh)
1mA Carousel with 6 foils
30,000
0.5mA 1.0mA
Beam Emittance(x,y/mm.mrad)
6.2, 3.8
horizontal 4 pi
~15 pi / 5 pi
Vacuum System
< 1.5x10-7 Torr
1x10-7 mbar
< 10-4 Pa
2.5x10-7 Torr
Control System
PLC　
LabView, cFP/LAN　
Pulsed Beam Extraction
Yes　
TBD　
Operating Cyclotron
INFN, Legnaro(2013)
ARRONAX, France
N/A
KAERI
* Proposed values

5. Major components of Cyclotron
Ion Source
- produces particles to be accelerated
Magnet
- keeps particles on a circular motion
RF system
- accelerates beams
Extraction System
- guides particles out of the cyclotron
Vacuum System
Cooling System
Diagnostics
Ref : Livingood, Cyclic Particle Accelerators

6. Extraction system with Carbon foil
B=1.36Tesla
E=[(qB)2/2m]r2
(1) Sectors, (2) Dees, (3) Conuter-dees, (4) Valleys, (5) Accelerating Gap,
(6) Stripper (carbon foil). Green solid line indicates for H- ion trajectory and dotted line for H+ ion trajectory.

7. Cyclotron structure
IBA 235 MeV
IBA Cyclone 18 MeV

8. Key Issues for Cyclotron at RISP
Carbon foil lifetime for 1mA Proton
- 30,000uAh average accumulated for 30MeV 250uA operating
2. Pulsed beam for Neutron TOF measurements
3. Uniform Beam Distribution for ISOL Targets

9. Carbon foil lifetime extension
Autoradiograph of the stripper foil after several H- runs. (Olof Solin at Åbo Akademi, Turku, Finland.)
Before Used
After Used
for ~ 20,000uAh

10. Principle of Stripper
Carbon foils to extract positive protons by stripping two electrons from accelerated negative protons.
Therefore a good quality of carbon foil is necessary to extract proton beam stable for a long time.
The lifetime of stripping foils is limited by several factors- extracting currents, the foil thickness, the repetition rate
Ref : Submitted, J.H.Kim et al., JKPS (2012)

11. Energy by protons : (1.70keV) x (1x10-3A) = 1.70W
Theory of heat transfer -1
□ Energy deposition:
Instantaneous power going through the carbon foil with 70MeV 1mA with a 6-mm circular diameter.
Power going through the carbon foil (1um thickness) can be defined as the product of energy loss (∆W) and current :
P = ∆W x I (1)
Energy by protons : (1.70keV) x (1x10-3A) = 1.70W
Ener. by electrons : (70MeV/1,836) x 2mA = 76.26W
□ Temperature Increase + Thermal Radiation:
The power P is equal to the sum of the increase in thermal energy of the stripper material:
P = ΔW∙I = m∙c∙(dT/dt) + 2ε∙σ∙(T4-To4) ∙S (2)

12. Stopping power was estimated by SRIM program (8.51MeV(g/cm2))
PSTAR : Stopping Power for Protons
Stopping power was estimated by SRIM program (8.51MeV(g/cm2))
(reference:

13. ESTAR : Stopping Power for Electrons
Stopping power was estimated by ESTAR program (7.25MeV(g/cm2)) (

14. T converges to the equilibrium temperature
Theory of heat transfer -2
T converges to the equilibrium temperature
(To can be neglected if T>>To). It could be led to a simple form following:
T = (ΔW∙I/2ε∙σ∙S)1/ (3)
The highest (averaged) temperature is reached at the center of the beam distribution where the current density is maximum. Considering a Gaussian beam distribution in the transverse plane:
Tmax = (ΔW∙I/4∙𝜋∙ε∙σ∙<x><y>)1/4 (4)

15. Estimated Temperature
Summary of estimated power deposited through the carbon foil by 70MeV negative protons with 1mA current (assume 2mm diameter)
*Assumed the surface density of carbon foil as 2g/cm3.
** stopping power was calculated by SRIM program
*** Kinetic energy of electrons were used 70MeV/1,836 = 38.13keV.
Two electrons are to be assumed release their kinetic energies into the foils. Two electrons are released, therefore the power is estimated as 38.13keV x 2mA = 76.26W.
Thickness
(μm)*
100μg/cm2
(0.5)
200μg/cm2
(1.0)
400μg/cm2
(2.0)
800μg/cm2
(4.0)
By stopping
power(W)**
0.85
1.70
3.40
6.80
By electrons
(W)***
76.26
Total (W)
77.11
77.96
79.66
83.06
Temperature
(K)
2,430
2,270
2,090
1,910

16. Experimental Setup with Electron Beam

17. Beam Size and Temperature Variation

18. with electron beam irradiation
Before and after foils
with electron beam irradiation
After

19. Surface Temperatures as a function
of Beam current

20. Foil Temperature and Lifetime Expectation

21. Summary and Future Work
The thermal distribution of carbon foils by electrons simulated as a function of foil thickness at extracting 70MeV 1mA protons.
Investigated the correlation between carbon foil thickness and its lifetime, a thicker foil is longer then thinner one.
Reducing the peak temperatures with proper methods will increase the foil’s lifetime.
To extend its lifetime at 1mA extraction, the wide beam size and a thicker foil should be considered for the long run.

22. 2. Pulsed Beam Generation for Neutron
(30~60MHz  10k ~ 1MHz)
Injection line (low energy Buncher + Chopper)
2. High Energy Chopper
3. RF Modulation

23. Resonance Cyclotron Frequency (30MHz)
Pulsed Beam Generation Scheme for
Neutron TOF measurement system
Current
Time
Ion Source
Continuous
beam
Chopper
Buncher
Low frequency
Matching
Beam
Resonance Cyclotron Frequency (30MHz)
RF System
High
frequency A B C D E
Target E

24. Characteristic Continuous Wave (CW)
Ipeak
Intensity
Tp=33nsec
Iave
Time
τp=3nsec
□ Resonance Frequency (f) = 30MHz
□ Pulse Period(Tp) = 33nsec
□ Average Beam Current (Iave) = 1mA
□ Number of particles per pulse (n) = Iave /f = 2x108 (particles/pulse)
□ Peak Current (Ipeak) = n/τp = 10mA
□ Average Current (Iave) = n/Tp = 1mA
≈ Peak Current (Ipeak) x Duty factor

25. Particles per macrobunch / Repetition rate
100ns Bunch Length / 5MHz Repetition Rate
□ Num. per macropulse (N) = τbunch /Tp∙2x108
□ Macrobunch Current (Imac) = N∙Q/τbunch ≅ 1mA
□ Average Current (Iave) ≈ N∙Q/2∙τbunch = 0.5mA
Particles per macrobunch / Repetition rate
Intensity
Time
Ipeak
Iave
τp=3nsec
Tp=33nsec
macropulse
macrobunch
τbunch=100nsec
Imac

26. Beam currents at Ipeak=10mA, f=30MHz
Parameters
Feasibility
Macrobunch length
Repetition Rate (Hz)
Particles per macrobunch
Macrobunch average current
Average current
3 ns
1 MHz (1µs)
2x108
10 mA
30 µA
0.1 MHz (10µs)
3 µA
0.1 KHz (10ms)
0.003 µA
100 ns
1 MHz(1µs)
6x108
1 mA
100 µA
0.1 MHz(10µs)
10 µA
0.1 KHz(10ms)
0.01 µA
10 µs
6x1010
1,000 µA
1 µA
10 Hz(100ms)
0.1 µA
Ipeak
High Peak Current is Required?
Intensity
τbunch
Repetition Rate
Time

27. Injection system for pulsing Beam with high current ion source
Beam Optics and Pulsing Effect
Matching the Beam Phase Space of longitudinal direction (Bunching)

28. Trace 3D Simulation for axial injection line
Input parameters:
Rest mass : 931 MeV, Kinetic energy : 30 keV, Current : 15 mA, Charge state : -1, Transverse emittance : 300 pi mm-mrad, Beam size : 10 mm, alpha : 0,
Energy spread : 1 %, Total length : 2.2 m, Focal length of thin lens : 22 cm,
Solenoid length : 40 cm, Solenoid strength : 1470 G, Quadrupole strength : 0.
J.Y. Lee (Postec)

29. 3. Uniform Beam Generation for ISOL Target
Passive Scattering
- Energy degradation and Beam Loss
2. Active Scanning
- Wobbling methods to produce a uniform irradiation field
Multipole Magnets
- Particles in beam tail are folded into the center region by the nonlinear field effects

30. Transfer beam line design after stripping extraction
Based on the results from the beam optics calculation, the idiographic magnets in the lines including quadrupoles, bending magnets, steering magnet, switching magnets. Wobbling magnet is used in this case to enhance the good uniformity of beam distribution.
Transport Beam Line
Uniform Beam Distribution for ISOL Target
High Transport Efficiency

31. Uniform Beam Generation Scheme for ISOL Target System
K.R.Kim et al., Proceedings of IPAC’10, Kyoto, Japan (2010)

32. Various Wobbling Methods
Beam pattern(left), Magnetic field wave form (right)

33. Formation of a Uniform Ion Beam using Multipole Magnets
It is possible to fold the tails of the transverse beam profile to the inside, or even to make the beam intensity distribution uniform in a beam transport system by means of a nonlinear focusing method. A two-dimensionally uniform beam has been formed using sextupole and
octupole magnets. An example of an off-center Gaussian beam approximately uniform only with sextupole and octupole Magnets.
FORMATION OF A UNIFORM ION BEAM USING MULTIPOLE MAGNETS, Y. Yuri et al., Proceedings of PAC09, Vancouver, BC, Canada

34. Uniform Beam using Multipole Magnets
Layout of the magnets. QF (QD) denotes the horizontally focusing (defocusing) quadrupole magnet. Two couples of sextupole (effective axial length: 33 cm, maximum gradient: 3.0×102 T/m2) and octupole magnets (effective axial length: 33 cm, maximum gradient: 1.3×104 T/m3)
2D intensity distribution of
a 10 MeV proton beam
on the target.
FORMATION OF A UNIFORM ION BEAM USING MULTIPOLE MAGNETS, Y. Yuri et al., Proceedings of PAC09, Vancouver, BC, Canada

35. Applications

36. Ref : SPES project at INFN

37. Medical radioisotope development
Is a Nuclear Medicine
the New Clear Medicine?

38. Thank you for your attention