Transcript Kein Folientitel

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+:
With some phase adjustments protons will go up to
500 kW protons at 1 GeV → 0.5 mA CW
400 MeV/u
1 GeV/u
→ 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
Medium b
U72+
Stripper
Ekin = 0.4…1.0 GeV
6-cell large aperture
structures at 704 MHz
Main LINAC
~ 380 m
U88+
Stripper
b = 0.71…0.87
• 2× Low energy
beam transport
(LEBT)
• 2× Radio
frequen- cy
quadrupoles
(RFQ)
RFQ2
b = 0.14…0.29
Ion
LEBT
U28/29+
Low b
Ion
Ekin = 0.1…0.26 GeV
RFQ1
Spoke cavities
at 352 MHz
b = 0.43…0.62
LEBT
b = 0.032
p+
Ekin = 10…40 MeV
Optimized ECR
sources for
protons and ions
Quarter wave res. at 88 MHz
Ekin = 500 keV
Overview – Drive beam
Dump
Gas
stopper
RFQ
Dump
Five experimental halls with different beam characteristics
→ Hall for primary beams
→ Three experiments with filtered secondary RIBs
→ Experimental hall for post-accelerated RIBs
NC-Linac
Exp.
Exp.
Exp.
Fragment
separator
Switching mag.
•
Exp.
Target
Exp.
Ekin = 10…15 MeV
Overview – Target and secondary beams
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
1
12
0.5
1 GeV
500 kW
238
28/29
100
400 MeV/u
200 kW
.
.
.
U
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
of EPAC
2002,energy
Paris, France
with theProceedings
required
beam
and power), to reduce the risk, and to keep
redundancy, two RFQs- two ECR sources scheme is considered (for light ions
romagnetic Design of an 80.5 MHz RFQ for the RIA Driver Linac
and heavy ions separately)
odlech, U. Ratzinger, Institut f¨ur Angewandte Physik, 60325 Frankfurt, Germany
lov, W. Hartung, F. Marti, X. Wu, R.C. York, NSCL, East Lansing, MI 48824, USA
• Normal conducting IH-type RFQs (power efficiency structure, higher shunt
impedance, better loss distribution, smaller dipole modes), 88MHz
B
A-B
outer girder
otope Accelerator (RIA) [1] requires a high
outer girder
pable of accelerating all ions through urainner girder
es 400 MeV/u with a beam power of 100 to
holder ring
holder
longitudinal
holder width
rst accelerating structure would be an RFQ.
holder ring
electrodes
holder
simulations using the MAFIA code [2]
ring
spacing
r2
electrodes
arcade
ormed to optimize the RFQ resonator. We
girder width
depth
tank
ign of an IH-RFQ (Interdigital H-Type) and
FQ. The operation frequency is 80.5 MHz
inner girder
ator has a length of 493 cm. Because of
A
w operation, optimization of the shunt im• requirements
Input energy?
Output
energy?
12 keV/u, 500 keV/u
e cooling
are major issues.
It
Figure 2: ’Slice’ of an IH type RFQ.
d that an RF power of 20 kW/m (IH RFQ)
4-Rod RFQ) would be required to reach the
of 60 kV.
(See fig. 2). Due to the small distance between the support
rings ( 10 cm) the losses on the electrodes are very small
r1
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
Gas flow
Fast separation efficiency ~50%
in ~10ms
DC +RF
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
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!