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

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

ISOL Linac Design Goals Beam energy: Input from RFQ: E = 0.3 MeV/u, A/q ≤ 8 for low-energy ISOL exp.: E ≥ 2.1 MeV/u, A/q ≤ 8 for high-energy ISOL exp.: E ≥ 17.5 MeV/u, A/q ≤ 8 after charge stripper: E ≥ 17.5 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

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)

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

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

Low-β SC QWRs βopt = 0.040 (βG = 0.036), ϕ=172 mm, bore radius=15 mm

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

Ez(0,0,z) [MV/m] βopt=0.04 βopt=0.10

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

Voltage gain curve w.r.t.β

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

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 Pdiss(@ R=20 nΩ) 2.2 Watt 4.4 Watt R/Q (with TTF include) 412 Ω 510 Ω

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 0.024 mm and 0.26 mm upward, steering (~0.7 mrad) reduced to ≤ 0.1 mrad

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

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 %)

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°

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

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°

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

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

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

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 = 64.3 deg/KeV/u Synchronous phase φs is set to be - 22°

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

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

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

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

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 %)

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

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.

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