1. SC ISOL Linac of KoRIA
Tae-Sun Park (SKKU)

2. Layout of ISOL Linac ISOL system Frequency = 70 MHz
E=0.3 MeV/u,
A/q ≤ 8
E≥17.5 MeV/u,
A/q ≤ 8
Frequency = 70 MHz
Energy for charge stripper (of IFF Linac) ≥ 17.5 MeV/u
Max. A/q value: 8
Consists of
2 kinds of SC quarter wave resonators (QWRs)
24 cavities of βopt= 4 %
88 cavities of βopt= 10 %
E≥17.5 MeV/u,
A/q ≤ 3

3. ISOL Linac Design Goals
Beam energy:
Input from RFQ: E = MeV/u, A/q ≤ 8
for low-energy ISOL exp.: E ≥ MeV/u, A/q ≤ 8
for high-energy ISOL exp.: E ≥ MeV/u, A/q ≤ 8
after charge stripper: E ≥ MeV/u, A/q ≤ 3
Available beam energy [MeV/u] w.r.t A/q
Cf) Available beam energy: From ~0.16 MeV/u to the above curves

4. ISOL Linac Design Goals
Good beam quality
Minimize emittance growth
Minimize beam loss
Multi-charge acceleration
Available beam current of “rare” isotopes : increased more than two times
|Δq/q| ≤ 5 %
Energy variation
0.16 ≤ E [MeV/u] ≤ 17.5
High feasibility
Simplified cavity shape, ample margins in cryostat design
Operating temperature : 4.5 K (rather than 2 K)

5. Cryo-modules
x 11
x 4
βopt=0.04
QWR
βopt=0.10
QWR

6. Cryo-modules Summary of overall specifications βopt =0.04 βopt =0.10
Total
Number of SC cryo-modules 4 11 15
Number of SC cavities
6*4=24
8*11=88
112
Number of solenoids
3*4=12
3*11=33 45
Total length
∼ 15 m
~ 75 m
~ 90 m

7. Low-β SC QWRs
βopt = (βG = 0.036), ϕ=172 mm, bore radius=15 mm

8. High-β SC QWRs
βopt = 0.10 (βG = 0.091), ϕ=340 mm, bore radius=15 mm

9. Ez(0,0,z) [MV/m]
βopt=0.04
βopt=0.10

10. TTF curve w.r.t.β
Red: A/q=3
Green: A/q=7
Blue: A/q=9

11. Voltage gain curve w.r.t.β

12. Beam energy w.r.t. z[m]
Red: A/q=3
Green: A/q=7
Blue: A/q=8

13. Specs of QWRs low-β high-β βopt 4.0% 10.0% f0 (frequency) 70 MHz
a0 (bore radius)
15 mm
L (diameter of O.C)
172 mm
340 mm
V0 (Input)
0.9 MV
2.0 MV Ep
30 MV/m
33 MV/m
E0= V0 /L
5.23 MV/m
5.88 MV/m
Topt
0.87
0.89
Q0 R=20 nΩ)
0.7 x 109
1.4 x 109
R=20 nΩ)
2.2 Watt
4.4 Watt
R/Q (with TTF include)
412 Ω
510 Ω

14. Dipole steering of QWRs
Steering: Δy’ [mrad] with respect to β
after beam axis shift
Dipole steering effect of QWR can be mitigated by
Tilting beam port faces
Race-track shaped beam port
Shifting beam-axis
We chose ‘3’ for simplicity, but either ‘1’ or ‘2’ will be used for actual fabrication
before beam axis shift
By shifting beam axis mm and 0.26 mm upward, steering (~0.7 mrad) reduced to ≤ 0.1 mrad

15. SC Solenoids
Two SC (Nb-Ti) solenoids (44 cm and 68 cm long) will be used.
XY-correcting coils will be employed
Design parameters
1st kind
2nd kind
Operating temperature
4.5 K
Coil material
Nb-Ti
Mechanical length
44 cm
68 cm
Max field strength
9 Tesla
∫B2 dz
9.7 T2·m
29.2 T2·m
Fringe field at neighboring
cavity wall
≤ 0.2 Gauss
Number of solenoids 12 33

16. Beam simulation with TRACK code
Reference isotope: 132Sn
Simulations have been done for
Single-charge
Typical: 132Sn18+
Highest A/q : 132Sn16+
De-acceleration of 132Sn18+ (E: 0.3 → 0.16 MeV/u)
Multi-charge case (132Sn17+,18+,19+ : Δq/q = 5.6 %)

17. Single-charge case with 132Sn18+
E= 0.3 MeV/u, εnx,y = 0.10 mm mrad, εnz = 5.1 deg/KeV/u
E= 18.3 MeV/u, εnx,y = 0.11 mm mrad, εnz = 5.5 deg/KeV/u
Synchronous phase φs is set to be - 22°

18. Single-charge case with 132Sn18+
Transverse & longitudinal emittance
Beam envelop (max and rms)

19. Single-charge case with 132Sn16+, A/q= 8.24
E= 0.3 MeV/u, εnx,y = 0.10 mm mrad, εnz = 5.1 deg/KeV/u
E= 17.5 MeV/u, εnx,y = 0.11 mm mrad, εnz = 5.4 deg/KeV/u
Synchronous phase φs is set to be - 22°

20. Single-charge case with 132Sn16+, A/q= 8.24
Transverse & longitudinal emittance
Beam envelop (rms)

21. De-acceleration with 132Sn18+
E= 0.3 MeV/u, εnx,y = 0.10 mm mrad, εnz = 5.1 deg/KeV/u
E= 0.16 MeV/u, εnx,y = 0.11 mm mrad, εnz = 5.6 deg/KeV/u
Synchronous phase φs is set to be - 160°
Field level cavities are adjusted

22. De-acceleration with 132Sn18+
Transverse & longitudinal emittance
Beam envelop (max and rms)

23. Multi-charge case with 132Sn17+,18+,19+
E= 0.3 MeV/u, εnx,y = 0.10 mm mrad, εnz = 5.1 deg/KeV/u
E= 18.3 MeV/u, εnx,y = 0.11 mm mrad, εnz = deg/KeV/u
Synchronous phase φs is set to be - 22°

24. Multi-charge case with 132Sn17+,18+,19+
Transverse & longitudinal emittance
Beam envelop (max and rms)

25. MEBT (from RFQ to ISOL Linac)
There are many possible different options
One example: 3-m long 1-rebuncher system
Design of more flexible 2-rebuncher MEBT for multi-charge RIBs is under progress

26. 180°bending section This is to insert ISOL beams into the IFF Linac
Consists of two symmetric, achromatic 90° sections

27. Charge stripping section
Charge stripping section is located at the end of ISOL Linac, just before the bending section, with a carbon-foil of thickness 0.3 mg/cm2
Lise++ code has been used for simulation for 132Sn isotope
Charge distribution w.r.t. beam energy

28. Energy [KeV/u] and angular [mrad] struggling w.r.t. foil-thickness
At E=17.5 MeV/u, 98 % of beams will be captured (with Δq/q ≤ 5 %)

29. Trace3D simulation for on-momentum
Trace3D simulation for off-momentum (Δp/p= 5 %)

30. Discussions
Some elementary parts of “Conceptual Design of SC ISOL Linac” have been done, but there remain tons of further works to be done: Microphonics issues, tuners, RF power couplers, end-to-end simulations with errors, and so on.
To secure successful construction of KoRIA, we need
To put much more efforts,
To build the lab where we can fabricate/test prototypes of SC cavities as soon as possible,
Strong international cooperation,
and so on.

31. Alternatives for overall ISOL-Linac Layout
“Option A” is our original choice, which is the simplest choice but most in-efficient (requires huge banding magnets)
“Option B & C” are more efficient, but the overall system becomes complicated