LINAC4 as BKP for LINAC2

LINAC4 as BKP for LINAC2

Alessandra M. Lombardi for the LINAC4 beam dynamics team

1. How to accelerate and transport protons2. 50 MeV and 160 protons 3. Limitation to intensity and emittance4. Comparison with LINAC25. Conclusions

A. Lombardi – LINAC4 as BKP for LINAC2 – IEFC workshop -23 march 2011

Layout of LINAC4


Layout of LINAC4


45keV 3MeV 3MeV 50MeV 102MeV

RFQ MEBT DTL CCDTL PIMS

45keV

Radio Frequency Quad.

352.2MHz3 m

Low Energy beam transport2 solenoid

1.8 m

MEBT11 EMQ3 Cavities2 Chopper units.

352.2MHz3.9 m

Drift Tube Linac3 Tanks114 PMQ1 EMQ

352.2MHz19 m

Cell-Coupled Drift Tube Linac7 Modules7 EMQ14 PMQ352.2MHz25 m

Π-mode Structure12 Modules12 EMQ

352.2MHz22.9 m

LEBTH-

160MeV

•Up to 3 MeV “charge insensitive”•In the MEBT line we have to respect the chopping dynamics•We need to match to a permanent focusing channel in the DTL and CCDTL

Match from the RFQ

Match to the DTLChop

Chopper line dynamics-removing micro-bunches (150/352) to adapt the 352MHz linac bunches to the 1 MHz booster frequency


Accelerating protons

• Rematch the chopper line :» Exactly same dynamics as for the H- until the dump» Rematch to the DTL with the last 4 quadrupoles


0.00E+00

1.00E-03

2.00E-03

3.00E-03

4.00E-03

5.00E-03

6.00E-03

7.00E-03

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

rms b

eam

size

-m

eter

s

distance along the chopper line - meters- RFQout to DTLin

x RMS [m]

y RMS [m]

160 MeV protons• Once re-matched at the DTL input we are OK until the end of the PIMS


0.00E+00

5.00E-04

1.00E-03

1.50E-03

2.00E-03

2.50E-03

3.00E-03

3.50E-03

0 10 20 30 40 50 60 70

rms b

eam

size

, m

eter

s

distance along the linac -meters - DTL to PIMS

x RMS [m]

y RMS [m]

50 MeV

100 MeV

160 MeV

E = 0.35 pi rms norm

DW=120 keV (1 rms)

40 mA

160 MeV

400 μsec

50 MeV protons• Switch off or do not install CCDTL and PIMS• Install all the quadrupoles-retune PIMS quads


0.00E+00

5.00E-04

1.00E-03

1.50E-03

2.00E-03

2.50E-03

3.00E-03

3.50E-03

4.00E-03

0 10 20 30 40 50 60 70

rms b

eam

size

-m

eter

s

distance along the linac - meters - DTL to PIMS

x RMS [m]

y RMS [m]

50 MeV

E = 0.28 pi rms norm

DW=250 keV (1rms) (can be improved)

40 mA

50MeV

400 μsec

Energy spread


0.00E+00

5.00E-05

1.00E-04

1.50E-04

2.00E-04

2.50E-04

0 10 20 30 40 50 60 70 80distance along the linac - meters - DTL to PIMS

rms energy spread (GeV)

CCDTL and PIMS off

CCDTL-IV at half the voltage

Transfer lines-50MeV


• Re-matched up to BHZ20. • all quadrupoles values are lower than for the 160MeV case. • De-buncher switched off

• Envelopes ok.

Horizontal (blue) and vertical (red) envelopes in the transfer line – PIMSout to BHZ20

At the PSB distributor


energy current Pulse length(4rings)

Emittance(rms mm mrad)

Energy spread (rms –keV)

LINAC4 50MeV 40 mA 400μs 0.3 250 100 (CCDTL mod4)

LINAC4 160 MeV

40 mA 400μs 0.3 120

LINAC2 50 MeV 160mA 100μs 1 160 (measured 3/2011)

Current in linac4 is limited by the klystron (beam loading)

Present distributor is limited to 15 turns (100μs)

We could profit from smaller emittance with the new distributor

Recap on conventional Multiturn Injection – C. Carli

• Septum (magnetic for PSB) separates space in – Region for incoming beam – Region for circulating beam

• Different injected turns in distinct regions of phase space

• Limited phase space density in receiving synchrotron– High beam current required– Small emittances required

• Note on H- charge exchange Injection– No septum … different turns injected in

same phase space regions– Longer pulse and lower beam current

with Linac4


Sketch of conventional multiturn injection (betatron tacking in hor. phase space from P. Van der Stok, CERN/PS/BR 81-28

X’

X

X

X’

Injection of protons from Linac4 into the PSB – C. Carli• 50 MeV protons from Linac 4

– Beam current about a factor four lower (40 mA instead of 160 mA)

– Horizontal (norm. rms) emittance about a factor three lower (~0.3 mm instead of ~1.0 mm)

– Pessimistic scaling for intensity reduction (for LHC and high intensities)

• Keep the same injection bump, number of turns …

• Intensity larger than ¼ the one available with Linac2 (better injection efficiency)

– Optimistic scaling• Reduction only by ratio of brightness from Linac: factor 3/4• Slower injection bump (KSWs) and more injected turns

– Simulations of injection required for more precise picture

– May-be useful depending on LHC request (e.g. 75 ns LHC beam with double batch PS filling)

• 160 MeV protons from Linac4– Technical issues: strengths of Linac2 equipments in the injection line (distributor, vertical septum, vertical

bend, injection septum & bumpers …)

– Not of interest:

• Less intensity with shorter revolution period (1.0 μs instead of 1.6 μs @50MeV)• Higher energy not of interest to mitigate space charge effects (lower intensity)


Summary


LINAC2 50 MeV 160mA 100μs1Hz

15 turns Present situation

LINAC4 + present PSB injection

50MeV 40 mA(chopped)

400μs1Hz

15 turns(limit of present distributor)

Can make some of the LHC beams, needs simulation.

LINAC4 + new distributor

50MeV 40 mA(chopped)

400μs1Hz

25 turns Can we profit from smaller emitt?

LINAC4 + DIS+ SMV +SMH?

160MeV 40 mA 400μs1Hz

25 turns PSB can handle 160MeV proton w/o major refurbishing.Will not profit from higher injection energy because of the low current.

Conclusions• Linac4 can accelerate protons both to 50 and 160MeV

• Linac4 (low current - long pulse ) is not optimal for delivering protons to the PSB

• Linac4 could deliver enough 50 MeV protons to make some LHC beams, but PBS simulations are needed to confirm.

• Linac4 can deliver a 160MeV proton beam with the same qualities as the nominal H- beam. Injection into the PSB is not straightforward.


LINAC4 as BKP for LINAC2

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