EffiCAS Efficient Facility for Ions at CAS Alick, Heiko, Iker, Rihua Goal: Radioactive/Rare Ion beam facility (RIB), 500 kW primary beam Heart of EffiCAS: 380 m long drive beam Linac Drive Linac fully optimized for U28/29+ → U72+ → U88+: 400 MeV/u With some phase adjustments protons will go up to 1 GeV/u 500 kW protons at 1 GeV → 0.5 mA CW → CW, high beam power, low beta → Superconducting LINACs! Target for production of secondary beams Linear post accelerator accelerating fragments up to 10 – 15 MeV/u Five experimental halls with wide range of beam characteristics All machines appearing in this work are fictitious. Any resemblance to real accelerators, planned or built, is purely coincidental.

6-cell large aperture structures at 704 MHz Overview – Drive beam Quarter wave res. at 88 MHz Ekin = 0.1…0.26 GeV Ekin = 10…40 MeV Ekin = 0.4…1.0 GeV Optimized ECR sources for protons and ions Ekin = 500 keV Spoke cavities at 352 MHz 6-cell large aperture structures at 704 MHz p+ LEBT RFQ1 Low b Medium b Main LINAC Ion U72+ U88+ LEBT RFQ2 Ion U28/29+ b = 0.032 2× Low energy beam transport (LEBT) 2× Radio frequen- cy quadrupoles (RFQ) b = 0.14…0.29 b = 0.43…0.62 b = 0.71…0.87 Stripper Stripper ~ 380 m

Overview – Target and secondary beams Ekin = 10…15 MeV Exp. Exp. Exp. Exp. Fragment separator stopper Gas Exp. Switching mag. Target RFQ NC-Linac Dump Dump Five experimental halls with different beam characteristics Hall for primary beams Three experiments with filtered secondary RIBs Experimental hall for post-accelerated RIBs

Final Beam Energy (GeV) Ion sources The source considered available for heavy ions with high current and high charge state, ECR is the only choice for CW operation (DC beam), Reliable, many labs are/will be operated with ECRs (CERN,RIKEN, RIA). The voltage of the ECR platform needs to be adjustable Output Beam current? Output Beam Energy: Particle A Q VECR(kV) IBeam(mA) Final Beam Energy (GeV) Final Beam Power (kW) p 1 12 0.5 1 GeV 500 kW . . .   U 238 28/29 100 400 MeV/u 200 kW

LEBT The DC beam from ECR source has to be bunched and transported to the RFQ with the correct parameters Solenoids will be used for focusing ions (field up to 0.8 T). The required field should be adjusted in order to reduce emittance growth. A 88 MHz buncher to separate different charged particles in alternative bunches if needed Target output beta ~0.03 Based on ESS-Bilbao design

RFQ To get a good beam quality (adequate transverse and longitudinal acceptance with the required beam energy and power), to reduce the risk, and to keep redundancy, two RFQs- two ECR sources scheme is considered (for light ions and heavy ions separately) Normal conducting IH-type RFQs (power efficiency structure, higher shunt impedance, better loss distribution, smaller dipole modes), 88MHz Input energy? Output energy? 12 keV/u, 500 keV/u

1st stage: Low beta accelerating section From b = 0.032 (U28+ and p) to b = 0.14 or 0.29 → Need adjustable b Same beta for U28+ and p at the input Individually phased SC l/4-resonators with low number (2 or 4) of gaps per resonator Energy Tetrode Acc. voltage per cavity: 2.5 MV Eeff = 1 MV/m (due to quadrupoles, cryo., beam instr.) → L = 40 m RF frequency: 88 MHz (352/4 MHz) Each cavity powered by separate tetrode amplifier → Maximum b flexibility

Medium beta accelerating section From b = 0.14 to 0.43 (U72+) or b = 0.29 to 0.62 (p+) → Moderate b adjustment Superconducting spoke cavities ANL RF voltage per cavity about 5 MV/m Eeff = 2.2 MeV/m (phase slippage due to var. b) → L = 100 m Operating frequency 4 · 88 = 352 MHz High power CW klystrons available on the market (CERN LEP type) Splitters + high power (but slow!) phase shifters to phase cavity groups

High beta accelerating section: Workhorse U88+: 100 → 400 MeV/u and protons 265 MeV → 1 GeV (75%) From b = 0.43 to 0.71 (U72+) or b = 0.62 to 0.87 (p+) → Little b adjustment Bell shape SC multi-cell cavities: Very high gradient with large aperture 5 MV/m with 2/3 covered by RF Eeff = 3.3 MV/m L = 220 m RF frequency 704 MHz (2×352) Well in range of cheap TV IOTs 130 kW per tube

Isotope beam production High Energy Beam from Driver LINAC => magnetic switching Direct to Expt => beam instrumentation, intensity control (collimation) Transport to Target area: Production of isotope beams Target Conversion: ion beams onto medium thickness targets (Liquid Li) Reaction products transported to large acceptance fragment separator Δp/p of 10% => collection efficiency: 60% (projectile), ~30% (fission) reduces unwanted activation in downstream Gas Stopper Isotope beam construction: Gas Stopper to thermalise ions then capture with DC+RF fields to collect isotopes: Gas = He Motivation: High Efficiency without “brute force” issues of standard spallation and fission technique DC +RF Gas flow Fast separation efficiency ~50% in ~10ms

Post-acceleration stage and beam dump Re-acceleration RFQ with wide initial acceptance β range and β ~0.01 at output Staged RFQ: charge stripping if needed for accel gradient and focusing (low q/m issue) large acceptance => 80% transmission efficiency limited by bunching efficiency 2nd Stage Linac: Envisage off the self design: NC Cavities to take beam to 10-15 MeV/u Option: Boost RFQ to match β so that can clone/use 1st stage of driver linac ? Beam Dump after target and separator Wide area coverage: Must absorb 500 kW (target malfunction) Dump design: Robust units ~20 radiation lengths of Cu: => 10cm length Survivability + cooling + remote handling Shielding of target + dump complex at least 8 m of standard concrete High level of radiation (~5x109 Bq/cm3 per month) Dump + collimation

Thank you for your attention! Issues and outlook Concerns: “Never leave the beam unattended” Need high resolution separator after target (Δm/m ~ 1/20000) => Big!! Control of beam spot energy density on target: beam spot ~ 1mm Target activation: ~30…60 % of beam power is lost in target => 6 MW/cm3 Issues of target survivability (1 month?) and remote handling Project continuation dependent on CAS budget Upgrade options Additional Ion sources Extension of 2nd Stage LINAC to bring isotope beams to higher energies Addition of different particle fragmentation methods (ISOL etc) Fast RF switches to distribute beam at stages along the beam line Thank you for your attention!