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

2

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

3

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)

4

Proton Beam Line

Not real bottleneck

Plasma cell

Laser

Proto

n

1 s = 202 mm

Laser, p+ beam line (20 m)

5

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

6

p+ & Laser beam

Requirements:0.1 mm & 0.02 mrad

pointing precision for p+ beam at cell

7

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


BPG BPGBPG BTV BTV BPG

e- Spectrometer

2.6 m

8

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

9

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

10

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


11

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


12

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

12

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+

13

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



e-

p+

13

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



e-

p+

13

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



e-

p+

13

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?

14

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+

15

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

15

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+

16

Diagnostics

Plasma cell38 mm

30 cm

10 m



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!

17

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


BPG BTVs BPG

e- Spectrometer

2.6 m

Plasma cell38 mm


BPGBPG BTV


See Patric’s talk!

17

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

18

~5 m

38 m

me-

p+

y

s

15 mm

zz’


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

18

~5 m

38 m

me-

p+

y

s

15 mm

zz’


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.)


18

The wake is the integrated electromagnetic force, the wake per unit length is just the force

x

yEffect of p+ beam on e- beam

19


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


19


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


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

19

On-axis Injection with shielding

e-

p+

20 mm

New design for vacuum chambersMagnets: >60 mm pole distance

20

On-axis Injection with shielding

e-

p+

20 mm


Plasma cell38 mm


BPGBPG BTV


Wakefield studies at merging!

20

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!

21

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 )

22

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



BPG BPGBPG BTV BTVs BPG

e- Spectrometer

2.6 m



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



BPG BPGBPG BTV BTVs BPG

e- Spectrometer

2.6 m



23

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.

24

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.

25

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!

27

On-axis Injection

e-

p+

20 mm


Backup option if clear indication of

disruptive effects on e- beam!

28

THANK YOU FOR YOUR ATTENTION

43

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


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% -

44

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!)

45


e-

p+

7.5 mm

Side-injection



Possibility of performing on-axis injection! (optics ready!)

46


e-

p+

7.5 mm

Side-injection



Possibility of performing on-axis injection! (optics ready!)

Possible use standard vacuum chambers

Magnets for e-beam: minimum aperture 55 mm

primary beam lines for the project at cern

Documents

e beam laser

sqrtbbmax3proton beam

bpm5p laser beam requirements

p disruptive

cern primary beam lines

axis injection design

plasmacell entrance

plasma cell entrance0