1. 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.

2. 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

3. 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

4. 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

5. 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

6. 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

7. 1st stage: Low beta accelerating section
From b = (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

8. 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

9. 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

10. 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

11. 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 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

12. 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!