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

Overview of the RISP IF Facility + ISOL Facility

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 81.25 MHz family (ANL, FNAL, TRIUMF, IMP ...) and 88 MHz family (SPIRAL2, CERN, ESS, SARAF …). Recommendation is made to choose between 81.25 MHz and 88 MHz. Decision is made to choose 81.25 MHz as the RISP base frequency.

Superconducting Linac Conceptual Design Frequency choice is made : base frequency is 81.25 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.

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

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

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

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

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.

Driver SCL lattice change NC quadrupole option has the following merits: 1. High intensity beam acceleration & operation are easy. 2. Linac cost seems to be in error range compared with the SC solenoid option. ( removal of costly SC solenoids ) 3. Accurate alignment of NC quadrupoles is feasible. 4. Preliminary cryo-load comparison suggests that overall cryo-load may not be an issue.  difference is small compared with the dynamic load. 5. Better beam quality 6. Operation is more straightforward. Linac length decrease : 97 m  90 m for the SCL 1, compared with the previous design.

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.

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.

Static cryo-load estimation of the SCL 1 TRIUMF type cryomodules (4 cav + 1 SC solenoid) 294 W @ 4K (excluding SC solenoid cryo-load). Proposed SCL lattice 372 W @ 4K Dynamic load is estimated to be 0.81 kW @ 2K for the SCL 1. Compared with dynamic load, the static load difference seems small.

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

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

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

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 (%)

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.

QWR is being optimized 8 cm Matlabjon Sattorov 77.8 cm 2 cm 7.68 cm  = 0.047, f = 81.25 MHz

QWR geometry & fields for f= 81.25 MHz Matlabjon Sattorov

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

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 132.285 Gap voltage, MV 0.595 RsQ,  41.8138 r, mm 48.5 R, mm 107.8 d, mm 107.7956 lint, mm 135.5907 g, mm 34.8975 rdt , mm 60 rs , mm r1 , mm 25 h, mm 936 2r1 d rs rdt h g lint 2R Eabs Habs

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.

RISP Site Plan SCL

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.)

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

Sufficient space reserved for liquid Li and/or Carbon strippers

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

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)

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.

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

Beam envelope before and after stripper SCL to stripper Past stripper