session 5: fast cycling injectors session 7... · 2004. 11. 11. · nuclotron, superferric magnet...
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SESSION 5: Fast Cycling Injectors
from: R. Garoby, High Brightness Beams for LHC: Needs and Means, Section 5
chairman W. Scandale (CERN), scientific secretary L. Bottura (CERN)WEDNESDAY 10 NOVEMBER 09:00-13:00Overview of Linac4 and SPL to generateLHC beams with higher brightness, and CERNPSB+PS: present performance and possible upgrades R. Garoby (CERN) &M. Benedikt(CERN)09:00-10:00SIS100/300 & High Energy Beam Transport (slides)P. Spiller (GSI)10:00-10:30COFFEE BREAK & POSTER SESSION 10:30-11:00Fast pulsed SC magnets for SIS and super-SPSG. Moritz (GSI)11:00-11:30SPS impedance and intensity limitationsE. Shaposhnikova (CERN)11:30-12:00Multi-turn extraction and injectionM. Giovannozzi (CERN)12:00-12:30Possible role of FFAG's for the upgradeof the LHC/GSI accelerator complex F. Meot (CEA& IN2P3 LPSC)12:30-13:00
LHC injector chain limits in view of anLHC upgrade
The schemes presently used in the injectors’complexcan provide the nominal beam for LHC with 25 nsbunch spacing, as well as the 75 ns bunch train andvarious test beams.
The ultimate beam is not yet feasible today.
Space charge is the primary limitation, both in thePSB and in the PS, and solutions are proposed.
Beam experiments will be necessary to discover andaddress further limitations in the existing machines.
from: R. Garoby, High Brightness Beams for LHC: Needs and Means, Section 5
** w.r.t. ultimate in LHC *** Transmission PS-> LHC= 0.85* LHC Project report 626
Needs of various LHC luminosityupgrade scenarios
2.4 ×10112.0 ×10111.21 long bunch @1ADC
91c
10 ?
10
7.8
(e clouds ?)
4.6
3.6
Luminosity×1034 cm-2s-1
> 1.7 ×1011
3.2 ×1011
2.9 ×1011
1.7 ×1011
2.6 ×1011
Protons in 25 ns(εn=3.75 µm)
> 2.0 ×1011> 1Beam beamcompensation2
3.7 ×10111.9~ 80 long bunches
@ 1.6 ADC1d
3.3 ×10111.7Phase 1a +
15 ns bunchspacing
1b
2.0 ×10111.0Low β +
Large crossingangle
1a
3.1 ×10111.5Large crossingangle0
Protons ejectedfrom the PS***
(εn=3 µm)
Brightnessfactor**
CommentPhase*
courtesy of R. Garoby
Consequences
Work is needed to understand and minimisethe beam losses.
Improvements are mandatory to prepare forthe ultimate beam and the future LHCupgrades
Beam experiments are necessary toinvestigate the potential of the existingaccelerators, and especially the SPS (needsearly upgrade of the lower energy injectors)
from: R. Garoby, High Brightness Beams for LHC: Needs and Means, Section 5
Actions proposed
A solution based on RF gymnastics in the PS can beconsidered, but it will never cover the full range ofpossibilities envisaged for the LHC upgrade,
The solution based on LINAC 4 as new PSB injectorgives the potential to investigate most possibilities,and to operate with high reliability.
Ultimately, if a higher energy accelerator like the SPLreplaces the PSB, very high performance beamwould be available at the PS exit.
Other options are open to considerations, such asRapid Cycling Synchrotrons. Issues of dynamic rangefor a superconducting RCS (typical limit 15) need tobe addressed
from: R. Garoby, High Brightness Beams for LHC: Needs and Means, Section 5
Brightness increase in the PSthrough Batch Compression
PSB injects 7 (4+3) or possibly 8 (4+4) bunches from two PSBbatches into the PS (h=9),
accelerate up to intermediate energy where space charge isreduced,
compress adiabatically into ≈1/2 of the PS circumference,changing h from 9 to 14
accelerate the beam up to 25 GeV,
split the bunches into 84 using RF
A train of 42 or 48 bunches, spaced by 25 ns
is sent to the SPS every 3.6 s.
Best expected performance: 2.6x1011 ppb @ PS ejection
from: R. Garoby, High Brightness Beams for LHC: Needs and Means, Section 5
Tim
e
BucketHeight
(arb. units)
Batch compression (7 bunches case)
courtesy of R. Garoby
Batch compression in the PS (6): Pro’s and Con’s
• Manpower intensive preparation• Need for much machine time
• Fast & “Low cost” (low level RF)Implementation
Potential(ppb at PSejection)
Operation
Stage
• 42 bunches every 3.6 s with2.6×1011 ppb [ΔQ ~ 0.25]
• Delicate operation (manpowerintensive & prone to imperfection)
• Lower LHC filling factor (~ -7 %)• Longer LHC filling time (~ × 1.35)• Reduced availability for other users• 1.2 s flat porch in the PS with high
space-charge• SPS capability ?
Limitations & drawbacksAdvantages
courtesy of R. Garoby
Increasing brightness in the PSB withLinac 4: Pro’s and Con’s
Cost (P+M ~ 70 MCHF)
Construction time (~ 3years)
Implementation
Potential
(ppb at PSejection)
Operation
Stage
Safe
Possibly OK
72 bunches every 2.4 s with 2×1011 ppb[ΔQ ~ 0.3]
48 bunches every 2.4 s with 3×1011 ppb[ΔQ ~ 0.44]
Need for similar RFgymnastics than today inthe PS
Capability to accept a ΔQof 0.44 for a short durationat 1.4 GeV in the PS ?
SPS capability ?
Reliability (simple & robust operation forthe 72 bunches scheme)
Short dwelling time at high space charge Reduced LHC filling time (~ × 0.82 with 72
bunches)
Increased beam availability for other users
Limitations &drawbacks
Advantages
(25 ns bunch spacing)
courtesy of R. Garoby
Replacing the PSB by an SPL: Pro’sand Con’s
Cost (P+M ~ 500 MCHF)
Construction time (~ 5-6 years)Implementation
Potential
(ppb at PSejection)
Operation
Stage
Train of 1-80 bunches every 2.4 s withup to 4×1011 ppb [ΔQ ~ 0.31]
SPS capability ?
Renewed & modern PS injector
No need for RF gymnastics in the PS
Reliability (simple & robust operation)
Short dwelling time at high spacecharge
Reduced LHC filling time (~ × 0.82with 80 bunches)
Increased beam availability for otherusers
Limitations &drawbacks
Advantages
courtesy of R. Garoby
Replacing the PSB by an RCS:Pro’s and Con’s
Cost (P+M ~ xy0 MCHF)
Construction time (~ 3-4 years)Implementation
Potential
(ppb at PSejection)
Operation
Stage
Train of 72 bunches every 2.4 s withup to 4×1011 ppb [ΔQ ~ 0.31]
Need for similar RF gymnasticsthan today in the PS
SPS capability ?
Renewed & modern PS injector
Reliability (simple & robust operationfor the 72 bunches scheme)
Medium dwelling time at high spacecharge
Reduced LHC filling time (~ × 0.82with 80 bunches)
Increased beam availability for otherusers
Limitations &drawbacks
Advantages
courtesy of R. Garoby
The issue of the dynamic range
The maximum acceptable dynamic range in a pulsed,superconducting synchrotron (e.g. a Super-SPS) isaround 15, lower values make operation definitivelyeasier
both in the case of the use of an SPL to replace theinjector chain, as well as in the case of a RCS chain,the dynamic range of a Super-SPS for an energy andluminosity upgrade must be reduced (use the presentSPS as a high energy booster up to 150 to 200GeV?)
This fact may have a large impact in the globaloptimization of the chain
Comparative summary(25 ns bunch spacing)
2.4 s2.4 s2.4 s3.6 sRepetition period
Reliableoperation + all
upgrades
Reliableoperation + all
upgrades
Reliable operation+ 50% ofupgrades
Exploratory testsBEST USE
4 × 1011 ppb4 × 1011 ppb2 × 1011 ppb(3 × 1011)2.6 × 1011 ppbPotential intensity
per PS bunch
721-8072 (48)42Number of bunches /PS pulse
Comfort ++Reliability ++
Comfort ++Reliability +++
Comfort +Reliability +
DelicateLimited reliability
Operation
Setting-upperiod during
start-up
Setting-upperiod during
start-up
Setting-up periodduring start-upMD intensive
Implementation3-4 years5-6 years3 yearsFastDelay
> 150 MCHF~ 500 MCHF50 – 70 MCHFLowCost (P+M)
RCSSPLLinac 4Batch compressionin PS
courtesy of R. Garoby
The SPS (1)
courtesy of E. Shaposhnikova
The SPS (2)
courtesy of E. Shaposhnikova
courtesy of E. Shaposhnikova
Latest news from SPS
In September 2004 during extensive MDs fixed target(CNGS) beam with total intensity of 5.3 x 1013 wasaccelerated in the SPS from 14 GeV/c to 400 GeV/cwith ≈ 10% beam loss.
This is 15% above CERN intensity record of 1997and almost twice more than presently used forphysics.
This is also slightly above ultimate total intensity ofLHC beam in the SPS (which will be “only" 4:9 x 1013
but circulating in 1/3 of the ring)
First Stage: Second Stage: Acceleration + Acceleration + Compression Stretcher
U28+
U92+
U28+
p
Reference Ions
300 Tm100 TmMagnet. rigidity
1083 m1083 mCircumference
1 · 1012 /s
1 · 109 /s
1- 2 · 1012
2.5 · 1013
Number ofParticles
2.7 GeV/u
34 GeV/u
2.7 GeV/u
29 GeV
Energy
d.c.
slow ext.
25 – 90ns
< 50 ns
Compressed
bunch length
6 T2 TDipole FluxDensity
1 T/s4 T/sRamp Rate
s.c. cosΘs.c. wfMain magnettechnology
SIS300SIS100
SIS300SIS100
New : Circumference may be enlarged to 5.5 x SIS18 : 1192 m
SIS100/SIS300 Design Parameters
courtesy of P. Spiller
Fast pulsed SC Magnets R&D at GSI
SIS-100 aim at an efficient (low cryogenic loss) and sturdy (100
Mcycles) synchrotron Nuclotron, superferric magnet design from Dubna loss reduction, mostly through iron R&D
SIS-200 former option at 200 Tm rigidity improvement of the RHIC, single-layer design, mostly
through cable R&D
SIS-300 two-layer design, at present based on the UNK prototype
dipole cross section
This R&D is directly relevant for a RCS option in theinjector chain of CERN
Superconducting Magnets for SIS100
Collaboration: JINR (Dubna) Iron Dominated (window frame type) superferric design Maximum magnetic field: 2 T Ramp rate: 4 T/s Hollow-tube superconducting cable, indirectly cooled Two-phase helium cooling
Nuclotron Dipole
R&D goals
•Improvement of DC-field quality• 2D / 3D calculations
•Guarantee of long term mechanical stability (≥ 2⋅108 cycles )
•concern: coil restraint in thegap, fatigue of the conductor
•Reduction of eddy / persistent current effects(field, losses)
courtesy of G. Moritz
Vision of the final SIS-100 magnet
• cold mass: coil + yoke• Ceramic aperture spacer• Laminated and horizontallycut endblocks• Rogowski end profile• negative shimming• Homogenisation slits• more rigid coil structure• Coil ends restrained• Stainless Steel end plates
courtesy of G. Moritz
Fast pulsed SC Magnets R&D
(obsolete) SIS-200 option powered to B > 4 T during long, continuous
pulses at 2 T/s (relevant for acceleratoroperation)
powered to B = 4 T in a sequence of 2ramps at 4 T/s
measured AC loss in satisfactoryagreement with expectations
60 % of the AC loss is due to hysteresis, callingfor a reduction of the filament diameter
Superconducting Accelerator Magnets:SIS 200 / 300
RHIC dipole Collaboration with BNL Coil dominated: cosθ Maximum field: 3.5 T ⇒ 4 T Ramp rate: 70 mT/s ⇒ 1 T/s !!! Supercond. Rutherford cable One-phase helium cooling
courtesy of G. Moritz
R&D Goals for RHIC type dipole
Reduce the effects due tothe high ramp rate: lower loss in wire, cable and
iron better AC field quality
Improve the cooling of theRutherford cable open Kapton insulation with
laser cut holes
Use collars to ensure long-term mechanical stability collar
courtesy of G. Moritz
Further ideas: Multi-turn extraction
Multi-turn extraction
Principle proven in dedicated testsperformed in the past 2 years
Negligible losses in the formation of theislands
Allows manipulating the transverseemittance in a synchrotron
Left: initial phaseLeft: initial phasespace topology. Nospace topology. Noislands.islands.Right: intermediateRight: intermediatephase space topology.phase space topology.Islands are createdIslands are creatednear the centre.near the centre.
Bottom: final phaseBottom: final phasespace topology.space topology.Islands are separatedIslands are separatedto allow extraction.to allow extraction.
Novel multi-turn extraction principle
courtesy of M. Giovannozzi
Further ideas: Fixed Field AlternatingGradient Synchrotrons (FFAGS)
Old idea (from the 50’s) Revived recently within the scope of
studies on neutrino factories hadron therapy machines proton driver at FNAL and other projects…
FFAGS: a new hope ?
courtesy of F. Meot
Conclusions
revise parameters for the LHC upgrade andnarrow scope to few interesting and realisticalternatives
examine all possibilities for an upgrade of theinjector chain at CERN upgrade of present facilities new facilities (SPL/RCS)
investigate synergies with other physicsrequests
list technical issues and define relevant R&Dto come to a decision
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