Booster Beam DynamicsChristian Carli
On behalf of the team working on and contributing to the study: M. Aiba did all ORBIT simulations (Booster modelling …. injection) R. Garoby: elaboration of longitudinal painting scheme, Booster with Linac4 in the CERN complex B. Goddard and team: injection hardware, help implementing it in ORBIT M. Martini carried out ACCSIM simulations M. Chanel: experience on PS Booster operation and 160 MeV measurements S. Cousinau and her colleagues at SNS for help and advice on ORBIT F. Ostiguy for advice and help with ESME F. Gerigk, D. Montillot …..
Linac4 Machine Advisory Committee - Booster beam dynamics C. Carli 2/1529th January 2008
Overview of the presentation
Introduction PS Booster Overview PS Booster with Linac4
Injection studies Active longitudinal Painting Simulations of longitudinal Painting ORBIT Simulations of the PS Booster Injection
Benchmark effort ACCSIM versus Measurements
Integration in the CERN complex Further potential Topics and Studies Summary
Linac4 Machine Advisory Committee - Booster beam dynamics C. Carli 3/1529th January 2008
Introduction - PS Booster Overview
Constructed in the 70ies to improve the performance (intensity) of the PS Four superimposed rings (chosen instead of fast cycling synchrotron or 200 MeV Linac) 16 cells with triplet focusing, phase advance >90o per period Large acceptances: 180 m and 120 m in the horizontal and vertical plane,
respectively Multiturn injection with betatron stacking and septum at 50 MeV Acceleration to 1400 MeV (was 800 MeV at the beginning) Double harmonic RF (now: h=1 and h=2), resonance compensation, dynamic working
point … Intensities of up to 1013 protons per ring (i.e. four times design) obtained Maximum direct space charge tune shifts larger than 0.5 in the vertical plane Vesatile machine - many different beams with different caracteristics
Sketch of the PS Booster with: - Distribution of Linac beam into 4 rings - Recombination prior to transfer
Linac4 Machine Advisory Committee - Booster beam dynamics C. Carli 4/1529th January 2008
Introduction - PS Booster with Linac4
PSB to PS transfer energy increased in two steps from 800 MeV to 1400 MeV: To alleviate direct space charge effects at PS injection Creation of a bottleneck due to direct space charge in the Booster at low
energy PS Booster with Linac4:
Increase of PS Booster injection energy from 50 MeV to 160 MeV and 2 by factor 2
(Beam stays (a bit) longer with large direct space charge detuning) Goal: Increase of intensity within given emittances by factor 2
> Nominal LHC beam with PS single batch filling, Save generation of ultimate LHC beam with PS double (and single ?) batch filling, Increase of number of protons available for other experiments
H- charge exchange injection and Linac4 beam chopping: Opens possibility for painting (in all three planes ?) and further gain in performance
Losses and activation ?? Losses (on septum) inherent to conventional multiturn injection disappear Losses (during times with large direct space charge detuning) at higher energy
Some bottleneck at transfers PS Booster -> PS and PS -> SPS ?!
Linac4 Machine Advisory Committee - Booster beam dynamics C. Carli 5/1529th January 2008
Introduction - PS Booster with Linac4Beams to delivered: Beams considered challenging:
In addition various beams (less challenging ?): LHC single bunch beams: Pilot beam, Probe beam, single bunch physics
beam Beams for PS physics: Slow ejection east hall, AD, nTof … MD beams … Many of these beam may be even easier with Linac4 (Painting of small
longitudinal emittances, no sieve reducing the Linac2 intensity needed … )
Beam PSB intensity per ring
(1012 protons/ring)
PSB Transv. Emittances
(rms, normalised)
PS intensity after injection (1012 protons)
LHC nominal – single batch PS filling (3 out of 4 PSB rings used)
> 2.76 and < 3.25 (2 bunches per ring)
2.5 m (H) 2.5 m (V)
> 8.3 and < 9.8
(6 bunches) LHC ultimate - double batch PS filling (6 bunches from two shots)
>2.04 (1 bunches per ring)
2.5 m (H) 2.5 m (V)
>12.24
(6 bunches) LHC ultimate – single batch PS filling (3 of 4 rings, feasible with losses ?)
> 4.08 (2 bunches per ring)
2.5 m (H) 2.5 m (V)
>12.24
(6 bunches) CNGS - single batch PS filling >8 and <12.5
(2 bunches per ring) 11.5 m (H)
4.6 m (V) >32 and <50
(8 bunches) ISOLDE up to 16
(1 bunch per ring) 12 m (H) 7 m (V)
-
Remark: Intensities needed depend on losses in downstream accelerators (at present ~15% loss PS and SPS for nominal LHC beam).
Linac4 Machine Advisory Committee - Booster beam dynamics C. Carli 6/1529th January 2008
Injection - active longitudinal Painting With Linac4: similar RF system than at present
Double harmonic fundamental h=1 and h=2
systems to flatten bunches reduces maximum tune shifts
Injection with d(B)/dt = 10 Tm/s (no need for injection with small ramp rate with painting any more)
Little (but not negligible) motion in longitudinal phase space.
No way for painting from synchrotron motion (large harmonic numbers and RF voltages ruled out)
Need for active painting (aim: fill bucket homogeneously) and energy modulation
Linac4 Machine Advisory Committee - Booster beam dynamics C. Carli 7/1529th January 2008
Injection - active longitudinal Painting
Principle: Triangular energy modulation (slow, ~20 turns for LHC) Beam on/off if mean energy inside a contur ~80% of acceptance Nominal LHC: intensity with 41mA (!!!) after 20 turns High intensity: several and/or longer modulation periods
Potential limitations: Linac4 jitter, debunching of Linac4 structure in Booster
Linac4 Machine Advisory Committee - Booster beam dynamics C. Carli 8/1529th January 2008
Injection - Simulations of
longitudinal motion
Simulation with ESME for nominal LHC beam: Energy modulation 1.1 MeV, plus rms spread 120 keV About 98 % of particles at the and buching factor ~0.60.
High intensity (reduced bucket hight due to direct space charge): Similar results with reduced E modulation
After 10 turns after 20 turns (completed injection) after~3000 turns
Linac4 Machine Advisory Committee - Booster beam dynamics C. Carli 9/1529th January 2008
Injection - first Results with ORBIT
Combines: Transverse painting as designed by team working on new injection hardware Active longitudinal painting
In Case of Dispersion Missmatch: Blow-up of horizontal emittance Large/small emittance dependant on position in longitudinal phase space Investigations with/without dispersion mismatch
Evolution of rms emittances after injection - blow-up (extrapolation ?) may be too large(slightly larger relative blow-up for 99% and 100% emittances)
from M. Aiba
Linac4 Machine Advisory Committee - Booster beam dynamics C. Carli 10/1529th January 2008
Injection - first Results with ORBIT
from M. Aiba
-20 x(mm) 20
-15 y(mm) 15
-180o phase 180o-2 E
(M
eV
)
2
-6 y’
(m
rad
)
6-3
x’
(m
rad
)
3
-180o phase 180o
0 y(m) 100
0 x(m) 100-20 x(mm) 20
-15 y(mm) 15
-180o phase 180o-2 E
(M
eV
)
2
-6 y’
(m
rad
)
6-3
x’
(m
rad
)
3
-180o phase 180o
0 y(m) 100
0 x(m) 100
Dispersion at injection matched D mismatch (line ends with D=0m, Dbooster~-1.4m)
Linac4 Machine Advisory Committee - Booster beam dynamics C. Carli 11/1529th January 2008
Injection - first Results with ORBIT
from M. Aiba Only nominal LHC beam
considered so far No simulations for high
intensity yet 240 000 macro-particles over
5000 turns (~5ms) Feasible within a reasonable
time for the job to run No acceleration, nor injection
foil scattering, nor machine imperfections
No dramatic effect of dispersion mismatch
Blow-up difficult to extrapolate (straight line, saturation …) Simulation over more turns and
with more particles ?
Linac4 Machine Advisory Committee - Booster beam dynamics C. Carli 12/1529th January 2008
Benchmark Efforts -ACCSIM versus Measurements
Benchmark measur’ts (M. Chanel): High intensity (1013 protons in one
ring) beam at 160 MeV plateau Time evolution of emittances and
intensity Long bunches (see fig.) tune shifts
~0.25 Short bunches (second harmonic RF in
phase) -> more losses Different working points ….
(2)=(100, 47) m
(2)= (93, 52) m
Simulation (M. Martini) with ACCSIM: Only short times (computation time) In general overestimation of growth
rates (except long bunches & and hor. plane)
Insufficient statistics ? Attempt to compare with ORBIT ?
As well significant ACCSIMORBIT benchmark effort: Moderate agreement only so far
6
8
1 0
1 2
1 4
1 6
1 8
2 0
0 2 0 4 0 6 0 8 0 1 0 0 1 2 0 1 4 0 1 6 0 1 8 0 2 0 0 200 Time (ms)
1000
0
p
roto
ns
10
13
0 time(ms) 2000
rm
s*
2
0
Dashed: measurement (interpolatio)Solid: simulation
v* long bunch
v* short bunch
H* short bunch
H* long bunch - fair agreement
Linac4 Machine Advisory Committee - Booster beam dynamics C. Carli 13/1529th January 2008
Integration into the CERN Complex - present Ideas, under InvestigationProposals made (R. Garoby et al.) for demanding Beams:
Nominal LHC Beam with single batch PS transfer: Splitting in the Booster, transfer of beam from three rings into hPS=7 buckets (rest
similar to present scheme with Linac2, but no double batch), details/options under discussion:
hPSB=1 (and hPSB=3) component to adjust spacing to hPS= 7 Shorter bunches due to ejection kicker, bunch rotation in PS, adiabatic RF voltage decrease … No hPSB=1 component and injection off the bucket center for blow-up
Ultimate LHC Beam (several options): Increase intensity (if feasible) of scheme for nominal LHC beam With double batch PS filling:
Like with Linac2 for nominal LHC beam, but higher intensities Tunes shifts and spreads in PS acceptable ? (some margin for bunch length)
“Exotic” schemes with single batch PS filling using all four PSB rings: Four Booster rings with hPSB=3 fill 12 out hPS=14 buckets … Four Booster rings with hPSB=2 fill 8 out hPS=10 buckets …
High Intensity (CNGS like): Schemes similar to present case hPSB=2 and hPS=8 with Linac2 (possibly higher
intensities)
Other beams with similar characteristics to present situation with Linac2: No problems for transfer to PS (just the injection into the Booster changes)
Linac4 Machine Advisory Committee - Booster beam dynamics C. Carli 14/1529th January 2008
Further Studies Injection studies with validation & optimization of the painting scheme:
Add acceleration and injection foil, possibly machine imperfections Tracking over longer times, check parameters to avoid numerics problems Check filamentation of structure from injection - especially with dispersion mismatch Limitations: Linac4 energy jitter, debunching in Booster and associated energy spread Elaborate scenarios for the generation of all beams needed
Integration into the CERN Complex - Elaborate detailed scenarios for all beams needed
Check limitations of present Booster hardware: Instabilities (existing damper with higher intensities) (Cure beam loading problems of h=2 cavities for h=1 beams to remove a potential
limitations for ISOLDE beams) Injection losses and associated activation (“normal” losses, failure scenarios …):
Desirable, in collaboration with or by injection hardware team (resources ?) Possibly advanced Studies on slow Beam Losses, and Activation and Collimation
….: Feasibility (computational tools, resources) unclear Most (all) accelerators with large direct space charge designed without detailed
simulations Losses in ring during period with large direct space charge effects:
Prerequisite: Benchmark measurements/simulations (160 MeV) to judge feasibility Estimate losses and induced radiation Possibly devise simple collimation (scraping needed before PS transfer)
Linac4 Machine Advisory Committee - Booster beam dynamics C. Carli 15/1529th January 2008
Summary Linac4 to improve Booster performance
Double 2 and, thus, intensities (within fixed emittances) by a factor two Versatility of the Booster must be maintained Active longitudinal Painting proposed: gain: ~10 % intensity for fixed
emittances Studies carried out so far
ESME simulations for longitudinal painting First ORBIT Runs of the complete Injection Benchmarks ORBITACCSIM and ACCSIMMeasurements
agreement not (yet?) satisfying Outlook
Complete injection simulations (acceleration, foils …) Validate longitudinal painting (energy jitter, Linac4 debunching) Complete study on integration of Linac4 & Booster into the CERN complex Injection Losses highly desirable Possibly check other potential problems (cavities, instabilities & damper …) Possibly advanced performance estimates with simulations:
Agreement simulations/measurements a prerequisite Study of Losses & Blow-up during Acceleration, Activation, Rudimentary
Collimation ?