LHC Beam Production in the Injectors in...

LHC Beam Production in the Injectors in 2016

R. Steerenberg 1 February 2016 OP Shutdown Lectures 2016 2

Rende Steerenberg, BE-OP

Acknowledgement: Hannes Bartosik, Heiko Damerau, Alan Findlay, Brennan Goddard, Steve Hancock, Klaus Hanke, Verena Kain, Malika Meddahi, Bettina Mikulec, Giovanni Rumolo, Guido Sterbini, Injector operations and coordination teams

Inspired from my Chamonix 2016 presentation

LHC Injector Beam Menu • LHCPROBE• LHCINDIV Standard & VdM & High Intensity• LHC 50 ns Standard & BCMS• LHC 25 ns Standard & BCMS• LHC 100 ns (Used for 90 m run)• LHC doublet (scrubbing SPS & LHC)• LHC 25 ns 8b4e• LHC 25 ns 80b4e (study/development stage)• LHC Ions (Early & Nominal)


Time Structure

Classical Filling of the LHC with Protons


1.2 seconds

PSB

PS

SPS

Time

= Field in main magnets= Proton beam intensity (current)= Beam transfer

To LHC clock-wise or counter clock-wise

450 GeV

26 GeV

1.4 GeVBeam Brightness

Energy & Trains

PS Booster Multi-turn InjectionEmittance increases linearly with intensity


PSB bunch intensity to be divided by 12 for LHC 25 ns bunch intensity

10 20 30 40 50 60 70 80-30

-20

-10

0

10

20

30

123

x

x’

What will be different with LINAC 4 ?


beam bumpers

H- ions Stripping foil

Injected protons

Circulating protons

What will be different with LINAC 4 ?

As a result the dependence of the

transverse emittance on the intensity will

be different


PSB bunch intensity to be divided by 12 for LHC 25 ns bunch intensity

See also lecture by Klaus Hanke on February 4th

LHC 50 & 25 ns Standard Beam Production (PS)• LHC cycles commissioned with

2.5 GeV intermediate flat top• Triple splitting moved to 2.5 GeV

• Lower space charge, Larger bucket

• Two times splitting at 26 GeV/c• Non-adiabatic bunch rotation before

extraction è 4ns bunch length (4σ)• For 25 ns PSB bunch intensity

divided by a factor 12• ILHC = 1.2x1011 ppb à IPSB = 14.4x1011 ppb

• Transverse emittance determined by PSB (multi-turn injection)


50 ns

25 ns: Each PSB bunch divided by: 12 à 6 x 3 x 2 x 2 = 7250 ns: Each PSB bunch divided by: 6 à 6 x 3 x 2 = 36

72 bunchesEject 36 orInject 4+2 bunches

h = 7 h = 21 h= 84

Eject 36 or72 bunches

Controlled blow-upsγtr

Triple splitting at Ekin = 2.5 GeV Split in four at flat top energy25 ns

E kin

= 2.

5 G

eV

2nd

inje

ctio

n

26 G

eV/c

LHC 50 & 25 ns BCMS Beam Production (PS)• BCMS = Batch Compression,

Merging & Splitting• Same cycle with BCMS at 2.5 GeV• For same LHC bunch intensity PSB

bunch intensity and transverse emittance is ~50% of standard scheme

• For 25 ns the intensity of 2 PSB bunches are divided by a factor 6 each• ILHC = 1.2x1011 ppb à IPSB = 7.2x1011 ppb


BCMS

50 ns

25 ns: PSB bunches ‘divided’ by: 6 à 8/2 x 3 x 2 x 2 = 4850 ns: PSB bunches ‘divided’ by: 3 à 8/2 x 3 x 2 = 24


h = 9 h = 21 h= 84



Batch Compression, merging & splitting Split in four at flat top energy25 ns

E kin

= 2.

5 G

eV

2nd

inje

ctio

n

26 G

eV/c

High brightness

LHC 25 ns 8b4e Beam Production (PS)• 8b4e = 8 bunches & 4 empty

buckets (repeatedly)• As mitigation scheme for

electron cloud in LHC• Already proposed and tested

R. Garoby et al., in 2000• Triple splitting at 2.5 GeV

replaced by double splitting


Each PSB bunch divided by 2 leaving 1 bucket empty at h=21At high energy each bunch/bucket split in 4 à 8b4e

72 bunchesEject 36 orInject 4+2 (3) bunches

h = 7 h = 21 h= 84



Double splitting at Ekin = 2.5 GeV Split in four at flat top energy

25 ns

E kin

= 2.

5 G

eV

26 G

eV/c

High brightness Empty buckets

LHC 25 ns 8b4e: Some Results• LHC 25 ns 8b4e was tested in October 2015, injecting

into the LHC


Beam in SPS with 6 bunches from PSBhence 48 bunches in total

• With:• Up to 56 bunches per PS batch

possible• Up to 1.7x1011 ppb• ~ 3 µm transverse emittance

• Combining with BCMS gives smaller transverse emittance

Doublet Scrubbing beam production scheme• Based on production scheme of

LHC 25 ns standard beam

• With final bunch rotation, using 40 MHz, but no 80 MHz cavities

• Different phasing at PS extraction

• Transverse emittance is not 1st order critical parameter for scrubbing

• Intensity is more important• ~1.7x1011 p/doublet


0 10 20 30 40 50 60 70

Long

. bea

m p

rofil

e

0 10 20 30 40 50 60 70Time [ns]

ΔE

0 10 20 30 40 50 60 70Long

. bea

m p

rofil

e

0 10 20 30 40 50 60 70Time [ns]

ΔE

0 10 20 30 40 50 60 70Long

. bea

m p

rofil

e

0 10 20 30 40 50 60 70Time [ns]

ΔE

25 ns

Non adiabatic splitting at SPS injection

20 ns5 ns

LHC 25 ns 80b4e ns Beam Production (PS)• Based on standard 25 ns beam

• Inject 7 bunches in h = 7 (instead of 6)• Perform triple splitting è 21 bunches• Use Transverse FeedBack (TFB) to

eliminate one of the 21 bunches at 2.5 GeV

• Accelerate 21b1e and perform two time splitting, including non-adiabatic bunch rotation as usual

• Similar performance as standard 25 ns beam, uses same intensities in PSB


Beam studies and TFB development ongoing

50 ns

25 ns: Each PSB bunch divided by: 12 à 6 x 3 x 2 x 2 = 7250 ns: Each PSB bunch divided by: 6 à 6 x 3 x 2 = 36


h = 7 h = 21 h= 84



Triple splitting at Ekin = 2.5 GeV Split in four at flat top energy25 ns

E kin

= 2.

5 G

eV

2nd

inje

ctio

n

26 G

eV/c

Performance Exclusion Plot• Increasing longitudinal emittance and bunch length will put the PS

space charge limit in the shadow of the PSB space charge limit


Same intensity limit (SPS) with smaller transverse

emittance possible, hence brighter beams

Most likely quite a few Machine Developments on

this topic in 2016

Beam Quality Tracking• Regular beam quality measurements are very

important• Interpret them correctly • Document them in the logbook • Ensure that they are logged properly in the logging data

base

• Transverse Brightness was tracked manually in 2012 per machine

• Was automated in 2015, using logging database and linked to LHC fill number through Accelerator and Performance Statistics webpage

• To be consolidated for 2016 run• Translate all to LHC bunch intensity/brightness


2016 Injector Performance Reach


PSBextraction PSextraction SPSextractionIp /ring ɛh andɛv nb nb Ip /bunch ɛh andɛv nb Ip/bunch ɛh andɛv nb[x1011] [mm·mrad] batches bunches [x1011] [mm·mrad] bunches [x1011] [mm·mrad] bunches

1σ,norm. 1σ,norm. 1σ,norm.LHC25(STD) initialspec. 13.8 ≤2.5 2 4+2 1.15 ≤3 72 1.15 ≤3.5 1– 4x72è 288LHC25(STD)2015 16 1.9 2 4+2 1.2 2.3 72 1.15 2.5 1– 2x72è 144LHC25(STD)2016 16.5 2 2 4+2 1.3 2.5 72 1.2 2.6 1– 4x72è 288LHC25(STD) Stretched 17 2.4 2 4+2 1.35 2.5 72 1.3 2.4 1– 4x72è 288

LHC25(BCMS)Operational 7.5 0.8 2 4+4 1.2 1 48 1.15 1.4 1– 4x48è 192LHC25(BCMS)Stretched 8.5 0.9 2 4+4 1.4 1.1 48 1.3 1.3 1– 4x48è 192

LHC258b4e(STD) 14 ~1.9 2 4+2 1.7 ~2.2 48 1.6 ~2.4 1– 4x48è 192

LHC50(STD) 11 1.5 2 4+2 1.8 1.6 36 1.7 1.7 1- 4x36è 144LHC50(BCMS) 6 0.9 2 4+4 1.8 1 36 1.7 1.1 1– 4x24è 96

Good scrubbed SPS required, HB beams require continuous tuning in Injectors




LHC258b4e(STD) 14 ~1.9 2 4+2 1.7 ~2.2 48 1.6 ~2.4 1– 4x48è 192





Design, documented in 2004




LHC258b4e(STD) 14 ~1.9 2 4+2 1.7 ~2.2 48 1.6 ~2.4 1– 4x48è 192





Done in 2015, but now possible with 288 bunches and SPS batch spacing of 225 ns




LHC258b4e(STD) 14 ~1.9 2 4+2 1.7 ~2.2 48 1.6 ~2.4 1– 4x48è 192





If we increase PSB bunch length and

longitudinal emittance




LHC258b4e(STD) 14 ~1.9 2 4+2 1.7 ~2.2 48 1.6 ~2.4 1– 4x48è 192





In case LHC e-cloud under control, can be blown up transversely






LHC258b4e(STD) 14 ~1.9 2 4+2 1.7 ~2.2 48 1.6 ~2.4 1– 4x48è 192



The 80B4e is not yet on this table and needs to be developed

However performance should be similar to standard 25ns

Beam StatusScheme PSB PS SPS LHC

25ns/50ns STD25ns/50ns BCMSDoublet100 ns25ns 8b4e25ns 80b4e


= Available = Ongoing / Considered

Conclusions• In 2015 LHC did not (yet) push the injectors for higher beam brightness, this

will/should change in 2016, provided e-cloud can be managed

• Both LHC 25 ns standard and BCMS beams were already very close to the injectors limits in 2015, leaving little room for further improvement

• In 2016 regular beam quality measurements are really necessary to ensure high brightness beam for the LHC.

• Sufficient scrubbing of the SPS is vital to reach top performance• Quite a few magnets were changed and machine was opened• Realistically: 1.2x1011 ppb in 2.6 µm at SPS extr. with 288 bunches and 25 ns• …..but, of course, we will have continue to try and push the limits further…..


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