1. Overview of the RISP SCL
Dong-O Jeon
representing the SCL Team
Rare Isotope Science Project

2. Overview of the RISP
IF Facility + ISOL Facility

3. RF Frequency Choice
Higher frequency generally means better efficiency.
No show-stoppers have been found for the choice of base frequency higher than 70 MHz considering design aspects including beam dynamics.
Broad infra base exists for MHz family (ANL, FNAL, TRIUMF, IMP ...) and 88 MHz family (SPIRAL2, CERN, ESS, SARAF …).
Recommendation is made to choose between MHz and 88 MHz.
Decision is made to choose MHz as the RISP base frequency.

4. Superconducting Linac Conceptual Design
Frequency choice is made : base frequency is MHz.
SC linac lattice is reviewed and alternative design is proposed with normal conducting quadrupoles.
Design of the charge stripping station is reviewed and alternative design is proposed.
Alternative charge stripping schemes are investigated and enough space is reserved in the lattice.

5. Choice of optimal geometric beta
SSR2
SSR1
For U beam
QWR
HWR
RISP: 0.047, 0.120, 0.30, 0.53
FRIB: 0.041, 0.085, 0.29, 0.53

6. Driver SC Linac Lattice
Design to accelerate high intensity ion beams
Flexile operation to meet the needs of various user groups
QWR
SC cavity
NC quadrupole
beam box
HWR
Previous Driver SCL
with SC solenoids
Driver SCL
with NC doublets

7. Schematic drawing of the SCL 1
quadrupole
beam box
Schematic drawing of the b1 segment
beam box example
(courtesy of SPIRAL2)
quadrupole
beam box
Schematic drawing of the b2 segment

8. Schematic drawing of the SCL 2
SSR1
quadrupole
344 mm
Schematic drawing of the b3 325 MHz segment
SSR2
quadrupole
486 mm
Schematic drawing of the b4 325 MHz segment

9. Driver SCL lattice change
SC solenoid lattice option has the following challenges : 1. Alignment of SC solenoids is not trivial to control. It is known that components in a cryomodule move no less than a millimeter during cool-down. 2. Small misalignment of SC solenoids by 0.5 mm generates significant emittance growth for the previous design. 3. Heat deposit by beam loss in the SC solenoids can be an issue. 4. Operation of the SC Linac is not trivial  for example due to magnetization of surrounding elements in the cryomodule.

10. Driver SCL lattice change
NC quadrupole option has the following merits:
1. High intensity beam acceleration & operation are easy Linac cost seems to be in error range compared with the SC solenoid option. ( removal of costly SC solenoids ) Accurate alignment of NC quadrupoles is feasible Preliminary cryo-load comparison suggests that overall cryo-load may not be an issue.  difference is small compared with the dynamic load Better beam quality Operation is more straightforward.
Linac length decrease : 97 m  90 m for the SCL 1, compared with the previous design.

11. ISOL post-accelerator
For the ISOL SCL lattice, we are planning to share the same doublet lattice as the driver SCL to reduce cost and R&D efforts.
EBIS is considered rather than ECR IS, generating higher A/q beams.
Design optimized for A/q ≤ 4.

12. Cost of Doublet Lattice
Cost estimation was done including cavity, tuner, coupler, internal cryogenics, vacuum system, cryomodule and process + cryomodule assembly cost.
Keeping the same lattice type for the driver SCL and ISOL SCL, cost estimation is done.
Cost change is less than 2% and is in error range of estimation.
Cost is not an issue.

13. Static cryo-load estimation of the SCL 1
TRIUMF type cryomodules (4 cav + 1 SC solenoid) K (excluding SC solenoid cryo-load).
Proposed SCL lattice K
Dynamic load is estimated to be K for the SCL 1.
Compared with dynamic load, the static load difference seems small.

14. Comparison of doublet and solenoid lattice with the previous design
Hyung Jin Kim
Parameters
Doublet
Solenoid
Comment
Length [m] 90 97
Drift 50cm in btwn cryomodules
Input energy [MeV]
0.5
Energy [MeV]
18.5
# of cryomodule 59 15
# of quadrupole
118 -
# of solenoid 60

15. Beam Simulations
Hyung Jin Kim
xrms
yrms
DW/Wrms
4ex
4ey
4ez

16. Phase advance in the SCL 1
Hyung Jin Kim
s / m
s / period a b

17. Error specification Parameters SCRF Cavity Warm Quadrupole SC Solenoid
Hyung Jin Kim
Parameters
SCRF Cavity
Warm Quadrupole
SC Solenoid
Distribution
Displacement (mm) 1
0.15
0.5
Uniform
Rotation (mrad) - 5
Phase (deg)
3σ Gaussian
Amplitude (%)

18. Error simulations in β1 section (baseline/solenoid)
Hyung Jin Kim
Max. envelope
Centroid
Emittance
76% increase
10% increase
baseline
350% increase
130% increase
solenoid
The shade region represents the bounds of envelope, centroid and e mittance due to misalignment and field errors.
The aperture of quadrupole and solenoid is 2 cm.

19. QWR is being optimized 8 cm Matlabjon Sattorov 77.8 cm 2 cm 7.68 cm
 = 0.047, f = MHz

20. QWR geometry & fields for f= 81.25 MHz
Matlabjon Sattorov

21. Quantitative dependence of the design parameters
in % as a function of the geometry
Matlabjon Sattorov

22. HWR dimensions and Field plots
parameter
value
Frequency, MHz
162.5
 value
0.12
Epeak, MV/m
30.0
Bpeak, mT
28.2
R/Q, Ohm
Gap voltage, MV
0.595
RsQ, 
r, mm
48.5
R, mm
107.8
d, mm
lint, mm
g, mm
rdt , mm 60
rs , mm
r1 , mm 25
h, mm
936
2r1 d rs
rdt h g
lint 2R
Eabs
Habs

23. Stripping Station Conceptual Design
Change from 180º chicane to 90º bend.
Conforms better to the topography of the site.
Shorter in length  better control in longitudinal plane.
Better in radiation activation control for the downstream section.

24. RISP Site Plan
SCL

25. Charge Selection with 180º Chicane Structure
Chicane structure for charge selection (length: ~ 27 m)
Charge selection slit
Stripping foil
Correction
Sextupole
Slit
20º bending
dipole
Quadrupole
doublet
using TRANSPORT code
Beam optics with off-momentum,
Δp/p = 5% Q=79±2
Beam optics with on-momentum
Vertical envelope
Dipole
Quad.
Focusing
Sextupole
Transverse position (1 cm/div.)
Transverse position (4 cm/div.)
Quad.
Defocusing
Without
correction
Horizontal dispersion
Charge selection:
Minimum beta
Large dispersion
Horizontal envelope
Aperture limitation (half: 10 cm)
With sextupole correction
Longitudinal position (2 m/div.)
Longitudinal position (2 m/div.)

26. Present Charge Stripping Section – 90° bend
Hye-Jin Kim

27. Sufficient space reserved for liquid Li and/or Carbon strippers

28. Charge Stripper
Previously carbon foil was considered as the charge stripper.
We are designing the charge stripper section for liquid Li or He gas charge stripper.
Courtesy of FRIB

29. Temp SCRF and Magnet Test Facility
A contingency plan for the temporary Superconducting RF and Magnet Test Facility is being developed, considering a possible delay in procuring the site.
Plan and cost estimation are developed.
Cost is 2856 M KRW (= $2.4 M) for SRF Facility and 1200 M KRW for Magnet Test Facility (20m x 20m)

30. Summary Base frequency of the SCL is determined.
For the SCL, NC quadrupole lattice is adopted rather than the SC solenoid lattice.
The SCL with NC quadrupole is better for beam quality control.
Cavity types and geometric betas are determined.
90º charge stripper design is adopted.
Contingency plan for the Superconducting RF and Magnet Test Facility is developed.

31. Thanks for your attention!
To the goal, Cheers!!

32. Beam envelope before and after stripper
SCL to stripper
Past stripper