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Introduction Main limitations (some of) acceptances & emittances space-charge

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IS IT POSSIBLE TO INCREASE THE p INTENSITY FOR CNGS BY A FACTOR 2 OR 3 ?R. CAPPI / SL Seminar, 21.03.2002

- Introduction
- Main limitations (some of)
- acceptances & emittances
- space-charge
- double batch injection
- bunch flattening
- 5 turn Continuous Transfer
- new 5t CT
- List of various schemes
- Conclusion

Introduction

- The talk is a ‘simplified’ summary of the paper:CERN/PS 2001-041 (AE) or CERN/SL 2001-032
- speculations => studies & experiments
- all results are PRELIMINARY and generally OPTIMISTIC
- the talk will be mainly devoted to PSB-PS issues
- I will not talk about collective effects ( except sp. ch.), longit. beam dynamics issues , transition crossing, etc.

Introduction: basic limitations

- NB: The present scheme is “consistent”
- i.e. LINAC, PSB, PS and SPS are all close to their limits,
- i.e. there is not a single weak point
- Linac2
- Close to its max Ip
- PSB
- Space charge ~limited
- Ek,max limited (1.4GeV)
- PS
- Acceptance ~limited
- Space charge ~limited
- 5t Continous Transfer
- ….
- SPS
- Acceptance limited
- ….
- Common: T & L collective effects, losses, transition, PRF , etc.

recent results

Acceptance & emittance issues

PS acceptance: Ax=60mm, Ay=20mm ex2< 22mm, ey2< 9mm

LHC ~ 5 5

Ex2

Experiments

Ax limit

Ey2

Ay limit

Courtesy of R.Steerenberg

PS

SPS

Present scenario & associated problems

L2

50 MeV

Limit

Nt = 3.3

ex< 22

ey< 9

1.4 GeV, h<0.9

DQ x,y~ 0.13 , 0.23

ex= 25

ey= 12

Nt = 3

14 GeV/c; 5t CT ; h=0.8

- NB: in all transparencies:
- ex= 4sx2/bx in mm
- intensities Nt are in 10^13 p
- 3) h is the transfer efficiency
- 4) yp is the p flux on target in 10^13p/s

X

Limit

ex= 4.2/3 = 1.4

ey= 2.5

ex< 3

ey< 2

Nt = 4.8

G.Arduini

filling time = 1.2s

yp = 4.8/6 = 0.8 G = 1

Space charge (at low energy in the PS)

Self field tune shift:

In the PS, to be safe :

If : T=1.4 GeV, ex = 22mm, ey = 9mmNt < 4.8 E13 p/p

(Kb=8)

to reach it WE NEED ADOUBLE BATCH INJECTION

NB: the SPS filling time will increase by 1.2 s (or 0.6 s if PSB can pulse 2x faster* )

PS LIMIT

*) M.Benedict et al. , undergoing study

PS

SPS

Double batch injection into PS: forecastL2

50 MeV

Limit

Nt = 2 x 2.4

ex< 22

ey< 9

1.4 GeV; h=1

ex= 21

ey= 9.2

DQ x,y~ 0.21 ; 0.35

Nt = 4.8 => Intensity limit

for a PS @ 1.4 GeV

14 GeV/c; old 5t CT;h=0.8

Limit

X

ex= 3.4/3 = 1.13

ey= 1.4

ex< 3

ey< 2

Nt = 7.7

yp = 7.7/7.2 = 1.07 G = 1.34

yp = 7.7/6.6 = 1.17 if [email protected], G = 1.46

Recent results of high intensity double batch injection studies

Experiments

PS transformer

Beam

intensity

( E10 p/p)

1st batch

2nd batch

Time (ms)

Courtesy E. Metral

Comparing with LHC “ultimate beam”

DQ = 0.20, 0.26

PS transformer

Beam

intensity

( E10 p/p)

Time (ms)

Courtesy G.Metral,E. Metral

Can we improve space charge limits?

- Increase injection energy

(e.g. with SPL)

- Reduce Ip by ‘bunch flattening’ techniques:
- (gain <1.5)

time

Bunch flattening in PSB: recent results

Final bunch

Initial bunch

Experiments

DQ reduction of ~28%

Courtesy C.Carli

5 turn Continuous Transfer

It is the way the PS uses to fill the SPS (at 14 GeV/c)

CSPS = 11 x CPS

PS

PS

SPS

Present system:

+ it works

- it is lossy (~20%)

x’

2

Qx = 6.25

3

1

5

x

Extracted beam

4

.

TT2 transfo

1

2

3

4

5

ES blade

time, 2ms / div

Final state

Simulation results

Simulation results

Proposal for a new 5t CT(*)The principle:

- the beam is adiabatically captured into 4 islands of a 4th

order resonance properly adjusted with sextupoles and octupoles,

ES

2) then the beam is extracted similarly to the present scheme.

(*) M.Giovannozzi, R.Cappi ; Phys. Rev. Lett., V.88, i.10

n 5t CT: pro / con

+ it should be less lossy (~5%)

+ the five beamlets will match the phase space topology better =>

less betatron mismatch at injection in the SPS=> lower transv. emittance beam to SPS =>

lower losses => higher intensity

- it has to be tested experimentally

n5tCT: x-x’ measurement results

Courtesy M.E.Angoletta, A-S.Muller, M.Martini,…)

Courtesy A-S.Muller

Courtesy A-S.Muller

PS

SPS

Expected results from: double batch+ n5tCT

L2

50 MeV

Nt = 2 x 2.4

ex< 22

ey< 9

1.4 GeV, h=0.9

ex= 21

ey= 9.2

Nt = 4.8

14 GeV/c; new5t CT; h=0.9

ex= 3.4/5 = 0.68

ey= 1.4

ex< 3

ey< 2

RMKS:

10% improvement => h=0.9

=>lower transfer losses,

better matching, etc.

Nt = 8.6

filling time = 2.4s

yp = 8.6/7.2 = 1.19 G = 1.49

yp = 8.6/6.6 = 1.30 if [email protected] G = 1.63

What about the SPS ?

- Single bunch coll. effects:
- 8.6E13ppp => 2 E10 p/b [LHC~10 E10; e-cloud > 4 E10 (5ns?)]
- Transverse impedance strongly reduced since 2002 => ~OK
- Beam loading:
- 8.6E13ppp => 0.4 E13/ms [ LHC~0.5 E13p/ms]~OK
- better if p=26GeV/c
- Transv. & long. Feedbacks
- HW modifications? 20=>100 MHz?
- octupoles :YES (some e x,y b.u. accepted) ~OK ?
- Transition:
- now 5% losses,
- better if p=26GeV/c
- Etc.

K.Cornelis, T.Linnecar, E.Schaposnikova,…

Conclusion

- first studies show encouraging results not onlyfor CNGS but for LHC itself and for cleaning up the machines by improving reliability
- a gain in p flux of ~1.5 seems feasible though difficult (cost ~0-2MCHF)
- a gain of ~2 is maybe possible but will be more expensive(~50MCHF)
- a gain of 3 will be VERY expensive ( ~300MCHF) and probably technically unrealistic
- we need a.s.a.p. clear priorities to continueat efficient speed.

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