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