Primary Beam Lines for the Project at CERN
description
Transcript of Primary Beam Lines for the Project at CERN
Primary Beam Lines for the Project at CERN
C.Bracco, G. Rumolo, F.M. Velotti J. Bauche , E. Gschwendtner, J. Hansen, L.K. Jensen, P. Muggli, A. Petrenko
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Outlines
Reminder and updates: p+ beam line e- beam line
Common beam line: detailed overview on different options (side-injection and on-axis injection): Requirements and constraints Challenges and possible solutions
Summary and conclusions
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Beam parameters & Assumptions
Protons Electrons
Momentum 400 GeV 10-20 MeV
Particles per bunch 3e11 1.2e9
Norm. emittance 3.5 mm mrad 2 mm mrad
Bunch length 12 cm 3 mm
Spot size @ focal point 0.2 mm 0.250 mm
Focal point from plasma cell entrance
0 m 0 – 6 m
Envelope (radius) 6 s 3 s
Max. Momentum spread 2‰ 5‰
Mechanical tolerance ± 1 mm ± 1 mm
Trajectory variation ± 1 mm *sqrt(b/bmax) ± 1 mm*sqrt(b/bmax)
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Proton Beam Line
Not real bottleneck
Plasma cell
Laser
Proto
n
1 s = 202 mm
Laser, p+ beam line (20 m)
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Not real bottleneck
Plasma cell
Laser
Proto
n
BP
M
BL
M
p+ & Laser beam
Mirror alignment wrt p+ beam: adjust p+ beam to reference trajectory mirror scan (losses)
Possible interlocks: BPMs (2 needed) and BLM stop SPS extraction if beyond limits to avoid damaging mirror.
BP
M
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p+ & Laser beam
Requirements:0.1 mm & 0.02 mrad
pointing precision for p+ beam at cell
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Diagnostics
Plasma cell
- Plasma cell: 40 mm external Ø, 38 mm inner Ø (isolation, etc. 30 cm Ø)
- 1 m drift (40 mm external Ø, 38 mm inner Ø) with irises up/downstream of plasma cell to intercept Rb
- 2 BTVs (OTR screens) located ~1.5 m up/downstream of plasma cell profile and position measurements, used during setup to align p+ beam and laser (screens for laser and p+!). Spot size: 1sup=250 mm and 1sdown=0.8 mm
- 3/4 BPGs (pickups) located at 1-6 m up/downstream of plasma cell define reference during setup and interlocked during operation (total accuracy ≤50 mm). Spot size: 1sup=500-230 mm and 1sdown=0.75-1.00 mm
- To measure: current (intensity) + synchronization p+ and laser (< 100 ps)
38 mm
30 cm
10 m
1 m drift with irises
1 m drift with irises
BPG BPGBPG BTV BTV BPG
e- Spectrometer
2.6 m
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Plasma cell 7% slope
Geometric constraints for e- beam
Laser, p+ and e- beam line
1.34 m
4.9 m
RF gun
RF gun
20% slope
RF gun
p+
e-
20% slope
~5 m
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Electron beam line design
22 main magnets
Both injection schemes possible*
s = 0.25 mm at merging point
Focal point variable between plasma-cell entrance to 6 m using last 3 quadrupoles
Side & on-axis injection
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17 main magnets
s = 0.25 mm at merging point
Focal point variable between plasma-cell entrance to 6 m using last 3 quadrupoles
On-axis injection
Electron beam line design
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Side and on-axis injection design: both injection schemes possible Very good control of dispersion
functions 30 % more magnets needed Worst behaviour w.r.t. static
errors
Pure on-axis injection: Oscillating vertical dispersion
function Less magnets, hence more
space for beam instrumentation Better behaviour w.r.t. static
errors
Side and on-axis injection design
Pure on-axis injection design
Electron beam line design
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Proposed design for side-injection
Any discontinuity in shielding e- from p+ disruptive two separate valves or pipe+ window for electrons
Proposed design for side-injection
Any discontinuity in shielding e- from p+ disruptive two separate valves or pipe+ window for electrons
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Side-Injection
1.5 m
15 mm
Experiment wish list:Vary merging point between 2 and 6 m from beginning of plasma cellVary angle between 5 and 20 mrad
1 mrad divergence from entrance of plasma cell induced by plasma on p+ beam
e-
p+
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Side-Injection
1.5 m
15 mm
D1fixed
20 mrad merging point @ 1.25 m + 0.75 m = 2.0 m from beginning plasma cell
1.25 m
D2movable
Experiment wish list:Vary merging point between 2 and 6 m from beginning of plasma cellVary angle between 5 and 20 mrad
1 mrad divergence from entrance of plasma cell induced by plasma on p+ beam
e-
p+
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Side-Injection
1.5 m
15 mm
D1fixed
D2movable
D2movable
20 mrad merging point @ 1.25 m + 0.75 m = 2.0 m from beginning plasma cell3 mrad merging point @ 1.25 m + 5 m = 6.25 m from beginning plasma cell
No screen over 4 m!! Region where e- approaching p+??
4.5 m e beam not shielded!
1.25 m
Experiment wish list:Vary merging point between 2 and 6 m from beginning of plasma cellVary angle between 5 and 20 mrad
1 mrad divergence from entrance of plasma cell induced by plasma on p+ beam
e-
p+
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Side-Injection
15 mm
D1fixed
D2movable
D2movable
20 mrad merging point @ 3.75 m + 0.75 m = 4.5 m from beginning plasma cell6.5 mrad merging point @ 3.75 m + 2.3 m = 6.05 m from beginning plasma cell
Need correctors around plasma (x-y steering)
3.75 m
4 m
Experiment wish list:Vary merging point between 2 and 6 m from beginning of plasma cellVary angle between 5 and 20 mrad
1 mrad divergence from entrance of plasma cell induced by plasma on p+ beam
e-
p+
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Dipoles around Plasma cellAngle[mrad]
Magnetic length [m]
Mechanical length [m]
B [Gauss]
Gap[m]
NI[A]
D1 & D2
20 0.5 0.7 27 0.3 637
3 0.5 0.7 4 0.3 95
6.5 0.5 0.7 8.5 0.3 204
- Dynamic range: - 5 - 30 Gauss Max field Bmax= 32 Gauss 15% - 85% Bmax
- 100-640 A Max current Imax = 750 A 15% - 85% Imax
Reasonably achievable dynamic range:6.5 – 20 mrad 4.5 -6 m merging (could be < 4.5 but effect of missing screen to be evaluated)
- Mechanical length of dipoles maybe too small longer magnets maximum kick <20 mrad (15 mrad)
- Material in dipoles gap (plasma cell) any effect on magnetic field?
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Vacuum chamber for side injection 1/2
- 1 mm thick walls, also in between the 2 beams (shield)
- p+ beam offset by -6.5 mm- e- beam offset by 8.5 mm- 15 mm offset e-p beams
e-
p+
e-
p+
e-
p+
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e-
p+
Vacuum chamber for side injection 1/2
e-
p+
e-
p+
p+ beam: inner diameter 15 mm, outer 18 mm
E- beam: Ellipse: - 32 mm x 21 mm inner- 34 mm x 23 mm outer
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Magnets design for side-injection
Magnets for e-beam (beam centred, mandatory for quadrupoles!): minimum aperture = 57 mm diameter + tolerance > 60 mm
p+ losses!
e-
p+
e-
p+
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Diagnostics
Plasma cell38 mm
30 cm
10 m
1 m drift with irises
1 m drift with irises
BPG BPGBPG BTV BTV BPG
e- Spectrometer
2.6 m
5 m e-/p+ common line
e-
p+
e-
p+
e-
p+
e-
p+
- Shielding between e- and p+ beam: last BPG (active control on pointing precision) possible? Space for pickups? Not possible moving the BPG upstream in the non-common part loose accuracy on angle!
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Diagnostics
- Shielding between e- and p+ beam: last BPG (active control on pointing precision) possible? Space for pickups? Not possible moving the BPG upstream in the non-common part loose accuracy on angle!
- Conflict e-beam magnets (last dipole ~1m upstream cell) and BI ( possible move plasma cell and BI slightly downstream)
- BTVs used also for e- beam line only during setup (additional screen or filters) 1 additional monitor downstream of plasma cell (position of spectrometer? Quadrupoles for e- after plasma needed?) 0.5-1m between the two BTVs. Spot size: 1sup=3.5 mm, 1sdown = 3 mm
- Special design for diagnostics! (2 years from specs.)
- Synchronization e-, p+ and laser
30 cm
10 m
1 m drift with irises
BPG BTVs BPG
e- Spectrometer
2.6 m
Plasma cell38 mm
1 m drift with irises
BPGBPG BTV
5 m e-/p+ common line
See Patric’s talk!
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Effect of p+ beam on e- beam~5 m
38 m
me-
p+
y
s
15 mm
zz’
Effect of p-beam on e-beam
b
Kick induced on e-beam
Charge density in p-beam slice dz’ @ z’
Ne = 1.2e9 electrons (longitudinal distribution in the e- bunch not taken into account as a first approximation)
Total energy e-beam = 20 MeV
total wake field behind the source (slice l(z’)dz’ of protons) acting on the witness (electron bunch) per unit length of the pipe (W/m2)
Dyp
Dye
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~5 m
38 m
me-
p+
y
s
15 mm
zz’
Effect of p-beam on e-beam
bDyp
Dye
Only for small displacements (|Dyp| and |Dye|<< b)and if the source is highly relativistic (g>>1)
Here Dyp = - 6.5mm, Dye = 8.5mm, g = 480 and b = 19 mm
So g>>1, but |Dyp| = 0.3 b and |Dye| = 0.4 b the linear expansion in dipolar and quadrupolar wakes is not applicable! Detailed studies are needed (existing model N. Mounet)
Dipolar component (kick)
Quadrupolar component (defocusing/focusing?)
Effect of p+ beam on e- beam
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~5 m
38 m
me-
p+
y
s
15 mm
zz’
Effect of p-beam on e-beam
bDyp
Dye
Total kick per unit length on the electrons from the part of proton bunch traveling in front of the electron bunch:
Assuming that the kicks do not significantly change the electron beam trajectory along the common chamber*, we can calculate the total kick received by the electron beam as
* It depends on the geometry (different aperture, irises, diagnostics, etc.)
Effect of p+ beam on e- beam
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The wake is the integrated electromagnetic force, the wake per unit length is just the force
x
yEffect of p+ beam on e- beam
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The wake is the integrated electromagnetic force, the wake per unit length is just the force
x
y
First difference with the be = bp caseSecond difference with the be = bp case:An additional term that needs to be evaluated with a large coefficient
Effect of p+ beam on e- beam
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The wake is the integrated electromagnetic force, the wake per unit length is just the force
x
y
First difference with the be = bp caseSecond difference with the be = bp case:An additional term that needs to be evaluated with a large coefficient
Effect of p+ beam on e- beam
Not possible to infer the effect of p+ on e- beams analytically using other models as reference (i.e. SPS 26 GeV) tracking studies with detailed geometry need to be performed
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On-axis Injection with shielding
e-
p+
20 mm
New design for vacuum chambersMagnets: >60 mm pole distance
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On-axis Injection with shielding
e-
p+
20 mm
New design for vacuum chambersMagnets: >60 mm pole distance
Plasma cell38 mm
1 m drift with irises
BPGBPG BTV
5 m e-/p+ common line
Wakefield studies at merging!
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Effect of p+ beam on e- beam for On-axis inj.~5 m
38 m
me-
p+
y
s
15 mm
zz’b
|Dyp| and |Dye| = 0 Dipolar component (kick) ~0
Quadrupolar component (defocusing/focusing?)
Bigger vacuum chamber, 58 mm inner Ø, over 4 m (last m 38 mm inner Ø)? x3.5 gain for resistive wall (1/b3)! Check effect of aperture variations induced wake fields (irises, diagnostics, etc.)
Merging point between e- and p+ beam to be studied!
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On-axis injection without shielding
e-
p+
e-
p+
- 1 mm thick walls- 38 mm inner Ø, 40 mm outer Ø
all along e- beam line
Alternative solution:- 58 mm inner Ø, 60 mm outer Ø
over first 4 m (impact on magnet aperture > 60 mm )
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Diagnostics
Plasma cell
- No conflict e-beam magnets (last dipole <1.5 m upstream cell) and BI
- Conventional BPGs and BTVs mechanical design (60 mm Ø)
- Need dedicated screens (hole for p+?) to steer and measure e- beam in presence of p+ beam (compensate for perturbations) during setup (laser?).
38 mm
30 cm
10 m
1 m drift with irises
1 m drift with irises
BPG BPGBPG BTV BTVs BPG
e- Spectrometer
2.6 m
5 m e-/p+ common line
See Patric’s talk!
p+ p+e-
e-
1sp=250 mm1se=2.5 mm
Upstream Downstream
1sp= 1 x 0.6 mm1se= 2 x 6 mm23
Diagnostics
Plasma cell
- No conflict e-beam magnets (last dipole <1.5 m upstream cell) and BI
- Conventional BPGs and BTVs mechanical design (60 mm Ø)
- Need dedicated screens (hole for p+?) to steer and measure e- beam in presence of p+ beam (compensate for perturbations) during setup (laser?).
- No need for dipoles around plasma cell !!
- Synchronization e-, p+ and laser
- This diagnostics scheme (+1 additional BTV downstream of plasma cell) is compatible with on-axis injection with shielding between e- and p+.
38 mm
30 cm
10 m
1 m drift with irises
1 m drift with irises
BPG BPGBPG BTV BTVs BPG
e- Spectrometer
2.6 m
5 m e-/p+ common line
See Patric’s talk!
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Interface p+ and e- beam: summary 1/2
Side-injection with shielding: New design needed for vacuum chamber and diagnostics (to be
confirmed if feasible, two years from specs for design, production and tests, cost!)
Conflict with last BPG for p+ beam (interlocked!) Blind inside plasma cell, how can we measure Patric’s talk Dipoles around plasma cell: large aperture (30 cm) and movable. What
are the materials around the plasma cell? Requirements on magnetic field from experiment? Correctors for fine steering.
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Interface p+ and e- beam: summary 2/2
On-axis injection with shielding: New design needed for vacuum chambers!
Do we need the shielding? Detailed tracking studies with complete geometry (restrictions, irises,
discontinuities, diagnostics) must be performed!
On-axis injection without shielding: Standard design for vacuum chambers and beam diagnostics
mechanics New screens are needed to measure e- beam (profile and position) in
presence of p+ to compensate for any effect (steering/focusing?) Effect of p+ beam on e- from wake fields to be quantified (quadrupolar
component) possible to further mitigate with larger aperture.
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Conclusions
Proton beam: Line and optics design are frozen (synchronization meas. still to be defined) Requirements for beam diagnostics are defined including measurements for
alignment of the mirror wrt p+ beam and laser and p+ beam all along plasma cell interlocks!
Electron beam Many constraints! Different flexible optics are defined:
Focal point from 0 to 6 m inside plasma cell On-axis injection Side-injection (convertible into on-axis injection with shielding)
New design for different components needed (depending on chosen option)
Suggestion: On-axis injection until LS2 (impedance studies for side injection) e- beam magnets design: 70 mm pole distance (to be confirmed by experts) ok
for all options! Vacuum chambers common part: 58 mm inner Ø and 60 mm outer Ø over 4 m +
38 mm and 40 mm over last 1 m? Any issue with vacuum? 26
On-axis injection
e-
p+
e-
p+
- 1 mm thick walls- 38 mm inner Ø, 40 mm outer Ø
all along e- beam line
Alternative solution:- 58 mm inner Ø, 60 mm outer Ø
over first 4 m (impact on magnet aperture > 60 mm )
Preferred option!
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On-axis Injection
e-
p+
20 mm
New design for vacuum chambersMagnets: >60 mm pole distance
Backup option if clear indication of
disruptive effects on e- beam!
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THANK YOU FOR YOUR ATTENTION
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Monte Carlo simulation to preliminary evaluate the effect of static errors in the line
Correction strategy: 1vs1 BPM – correctors
Correction method: SVD implemented in MAD-X
Only maximum beam envelope variation checked Aim: 3s <= 20 mm
Electron beam line design
Side and on-axis injection design
Pure on-axis injection design
Elements Errors Value Distribution
Dipoles B/B0 s = 0.3e-2 Norm(2s)
Quads g/g0 s = 0.2e-2 Norm(2s)
Quads Miasalign s = 200 mm
Norm(4s)
BPM Read +/- 0.5 mm
Uniform
BPM ON/OFF 2% -
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Side-injection no screen
e-
p+
7.5 mm
Side-injection
Reduce offset between p+ and e- beam
Centre p+ beam in vacuum chamber reduce losses and resistive wall impedance (studies!)
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Side-injection no screen
e-
p+
7.5 mm
Side-injection
Reduce offset between p+ and e- beam
Centre p+ beam in vacuum chamber reduce losses and resistive wall impedance (studies!)
Possibility of performing on-axis injection! (optics ready!)
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Side-injection no screen
e-
p+
7.5 mm
Side-injection
Reduce offset between p+ and e- beam
Centre p+ beam in vacuum chamber reduce losses and resistive wall impedance (studies!)
Possibility of performing on-axis injection! (optics ready!)
Possible use standard vacuum chambers
Magnets for e-beam: minimum aperture 55 mm