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 - PowerPoint PPT PresentationTRANSCRIPT
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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
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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.
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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.
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Acceptance & emittance issues
transv. emittances at PSB extraction vs PS total intensity
0
5
10
15
20
25
30
0 1 2 3 4 5Nt [10+13 ppp]
Ex2
, E
y2 [
10-6
m]
PS acceptance: Ax=60m, Ay=20m x2 < 22m, y2 < 9m
LHC ~ 5 5
Ex2
Ey2
Ay limit
Ax limit
Courtesy of R.Steerenberg
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Present scenario & associated problems
PSB
PS
SPS
50 MeV
1.4 GeV,
14 GeV/c; 5t CT ;
x= 25
y= 12
x< 22
y< 9
x< 3
y< 2
Nt = 3
x= 4.2/3 = 1.4
y= 2.5
X
Nt = 4.8
Nt = 3.3
Q x,y~ 0.13 , 0.23
NB: in all transparencies:
1) x= 4x2/x in m
2) intensities Nt are in 10^13 p
3) is the transfer efficiency
4) p is the p flux on target in 10^13p/s
filling time = 1.2sp = 4.8/6 = 0.8 G = 1
L2Limit
Limit
G.Arduini
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Space charge (at low energy in the PS)
32,
, yx
pyx
IQ Self field tune shift:
In the PS, to be safe : 3.0Q
If : T=1.4 GeV, x = 22m, y = 9m Nt < 4.8 E13 p/p(Kb=8)
to reach it WE NEED A DOUBLE 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
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Double batch injection into PS: forecast
PSB
PS
SPS
L2 50 MeV
1.4 GeV; 1
14 GeV/c; old 5t CT;
x= 21
y= 9.2
x< 22
y< 9
x< 3
y< 2
Nt = 4.8 => Intensity limit
for a PS @ 1.4 GeV
x= 3.4/3 = 1.13
y= 1.4
Nt = 7.7
p = 7.7/7.2 = 1.07 G = 1.34p = 7.7/6.6 = 1.17 if [email protected], G = 1.46
Nt = 2 x 2.4
Q x,y~ 0.21 ; 0.35
Limit
LimitX
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Recent results of high intensity double batch injection studies
Time (ms)
Beam
intensity
( E10 p/p)
1st batch 2nd batch
Courtesy E. Metral
PS transformer
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Comparing with LHC “ultimate beam”
Time (ms)
Beam
intensity
( E10 p/p)
Courtesy G.Metral,E. Metral
PS transformerQ = 0.20, 0.26
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Can we improve space charge limits?
• Increase injection energy (e.g. with SPL)
) ) 6.2
GeV4.132
GeV2.232
• Reduce Ip by ‘bunch flattening’ techniques:
(gain <1.5)
time
12Courtesy C.Carli
Q reduction of ~28%
Bunch flattening in PSB: recent resultsInitial bunch Final bunch
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5 turn Continuous TransferIt is the way the PS uses to fill the SPS (at 14 GeV/c)
CSPS = 11 x CPS
PS PS
SPS
x’
x1
2
3
4
5
Qx = 6.25
ES blade
Present system:
+ it works
- it is lossy (~20%)
Extracted beam
time, 2s / div
.TT2 transfo1 2 3 4 5
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Proposal for a new 5t CT (*)
The principle:1) the beam is adiabatically captured into 4 islands of a 4th order resonance properly adjusted with sextupoles and octupoles,
(*) M.Giovannozzi, R.Cappi ; Phys. Rev. Lett., V.88, i.10
Initial state
Simulation results
Final state
Simulation results
2) then the beam is extracted similarly to the present scheme.
ES
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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
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n5tCT: (x, x’ ) topology
Courtesy M.Giovannozzi0.244
0.245
0.246
0.247
0.248
0.249
0.25
0.251
0.252
0.253
0 2000 4000 6000 8000 10000 12000 14000 16000 18000
Turn number
Fra
ctio
nal
tu
ne
a) Initial state: no islands
Extraction
c)Transport within islands
Mixing
b) Capture process
qx
time~ 30 ms
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n5tC
T:
x-x
’ m
easu
rem
en
t re
su
lts
Court
esy
M.E
.Angole
tta, A
-S.M
ulle
r, M
.Mart
ini,…
)
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Expected results from: double batch+ n5tCT
PSB
PS
SPS
L2 50 MeV
1.4 GeV,
14 GeV/c; new5t CT;
x= 21
y= 9.2
x< 22
y< 9
x< 3
y< 2
Nt = 4.8
x= 3.4/5 = 0.68
y= 1.4
Nt = 8.6
filling time = 2.4sp = 8.6/7.2 = 1.19 G = 1.49p = 8.6/6.6 = 1.30 if [email protected] G = 1.63
RMKS: 10% improvement => =>lower transfer losses, better matching, etc.
Nt = 2 x 2.4
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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/s [ LHC~0.5 E13p/s] ~OK – better if p=26GeV/c –
• Transv. & long. Feedbacks– HW modifications? 20=>100 MHz?
– octupoles :YES (some x,y b.u. accepted) ~OK ?
• Transition:– now 5% losses, – better if p=26GeV/c
– Etc.
K.Cornelis, T.Linnecar, E.Schaposnikova,…
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The various schemes
# Description N sps [1013p/p]
POT flux [1013p/s]
Gain = / 0.8
~Cost~ [MCHF]
Remarks
0 present nominal scheme (reference)
4.8 4.8 / 6 = 0.8 1 0 Already difficult
1.1 =0 + double batch PS inj. 7.7 7.7 / 7.2 = 1.07 1.34 0 Higher Nsps but longer cycle
1.1a 1.1 + PSB @ 0.6s 7.7 7.7 / 6.6 = 1.17 1.46 1 Important HW modifications (?) Improvements for ISOLDE
1.2 1.1 + new5-turnCT 8.6 8.6 / 7.2 = 1.19 1.49 1 Better transfer efficiency (lower losses)
1.2a 1.2 + PSB @ 0.6s 8.6 8.6 / 6.6 = 1.30 1.63 2 Best of group 1
1.3 1.2 + 26GeV/c 8.6 8.6 / 8.4 = 1.02 1.28 3 No transition in SPS CT @ 26GeV/c ?
1.3a 1.3 + displaced & shortened PSB cycle
8.6 8.6 / 7.2 = 1.2 1.5 3 Very attactive
2.1 1.2 + a new H- 120MeV Linac
8.6 8.6 / 6 = 1.43 1.79 60 Improvements also for LHC, ISOLDE,…
3.1 SPL at 2.2GeV + new 5-turnCT at 14GeV/c
23 23 / 6 = 3.83 4.79 300 Extremely high coll. effects =>UNREALISTIC
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Conclusion
• first studies show encouraging results not only for 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 continue at efficient speed.