CNGS Proton beam line:
news since NBI2002
OUTLINE
1. Overview
2. Beam optics
3. Trajectory correction scheme
4. Beam stability
5. Aperture checks
6. Need of a collimator
7. Summary

7-11 November 2003

NBI 2003
Presentation by Malika Meddahi.

1Overview

7-11 November 2003

NBI 2003
Presentation by Malika Meddahi.

2Nominal beam parameters
Beam parameters

Nominal CNGS beam

Nominal energy [GeV]400

Normalized emittance [µm]H=12Emittance [µm]V=7

H=0.028

V= 0.016

Momentum spread ∆ p/p

0.07 % +/- 20%# extractions per cycle

2 separated by 50 ms# of train per extraction

1# of bunches per train

2100

Intensity per extraction [1013 p]

2.4

Bunch length [ns] (4σ )2r.m.s. bunch length [cm]15

Bunch spacing [ns]Train length [µs]57-11 November 2003

Upgradephase:
3.5 1013 p

10.5

NBI 2003
Presentation by Malika Meddahi.

3

Optics at Target (1)Nominal parameters : • Beta at focus in both planes : 10 m
• σx , σy at 400 GeV [mm]: 0.53 / 0.4• σ’x, σ’y at 400 GeV [mrad]: 0.05 / 0.4

7-11 November 2003

NBI 2003
Presentation by Malika Meddahi.

4

Optics at Target (2)• Round beams• Increase σ

βx[m]

2.5

102030σx[mm]

0.260.53

0.75

0.91

βy [m]

2.5

102030σy [mm]

0.2

0.4

0.56

0.7

Going to 30 m: feasible but reaching the power supply
limit and aperture limit (swapped power supplies)
7-11 November 2003

NBI 2003
Presentation by Malika Meddahi.

5Trajectory correction scheme (1)AIM:• Is the proposed scheme sufficient?
• Can we save some correctors or monitors?
• What happens if something goes wrong (w.r.t. faulty
correctors or monitors)

Took into account:Beam line errors (quad displacement, beam position monitor,dipole field and tilt, extraction from SPS)

7-11 November 2003

NBI 2003
Presentation by Malika Meddahi.

6Trajectory correction scheme (2)2-in-3 scheme: 2 consecutive half cells per plane out of 3 areequipped with Beam Position Monitors (BPMs) and correctors.
Phase advance per cell: π/2
Produce π bumps which may not be visible as the trajectory is heavily
under-sampled.
Problem worsen when some BPMs are malfunctioning Reading of the positions in both planes (X, Y) for all BPMs
 Add one BPM

7-11 November 2003

NBI 2003
Presentation by Malika Meddahi.

7Trajectory correction scheme (3)Corrector strength and efficiency scrutinized
3000 trajectory corrections
Max. Strength for the new dipole correctors: 60 µrad
Two correctors were removed from the scheme
Use some bending magnets as additional correctors.

7-11 November 2003

NBI 2003
Presentation by Malika Meddahi.

8Trajectory correction scheme (4)RMS max

Trajectory max.
(mm)

X before trajectory. Correction
X after trajectory correction

3.57 (3.58)
0.65 (0.65)

10.98 (15.02)
2.02 (2.68)

Y before trajectory. Correction
Y after trajectory correction

3.24 (3.20)
0.49 (0.62)

7.50 (8.02)
1.42 (2.52)

Reminder: max. trajectory excursion allowed: 4.3 mm
The proposed correction scheme is sufficient

7-11 November 2003

NBI 2003
Presentation by Malika Meddahi.

9Aperture checks (1)AIM:
Investigate the aperture of the proton beam line

Method:- Generate 100 000 particles according to Gaussian distribution tofollow the contour of the emittance ellipse- Populate tails of distribution

7-11 November 2003

NBI 2003
Presentation by Malika Meddahi.

10Aperture checks (2)Horizontal phase space
mrad

mrad

Start of the line

At target

10σ

10σ6σ6σmm
7-11 November 2003

NBI 2003
Presentation by Malika Meddahi.

mm
11

Aperture checks (3)Vertical phase space
mrad

mrad

Start of the line

10σ

At target

10σ6σ6σmm
7-11 November 2003

NBI 2003
Presentation by Malika Meddahi.

mm
12Aperture checks (4)Fraction of particles lost for different aperture misalignments andmomentum offsets.
100000 particles trackedFor nominal parameters, no particle losses are observed.
Losses occur for larger aperture misalignments or larger momentum
offsets

7-11 November 2003

NBI 2003
Presentation by Malika Meddahi.

13

Beam stability at the target (1)AIM:
Investigate the beam spot stability at the targetÆ Target resistance to non-centered beam

Took into account:Beam line imperfections (quad displacement, beam position monitor,
main dipole field and tilt, extraction, power supply precision)

7-11 November 2003

NBI 2003
Presentation by Malika Meddahi.

14

Type of error

Error
magnitudeHorizontal σx Horizontal σ’x
at target
at target(mm)(µrad)

Magnet errors

As defined

0.12 mm

11 µradHorizontal extraction angle

10 µrad r.m.s.

0.11mm

5 µradHorizontal extraction position 0.5 mm r.m.s.

0.32 mm

21 µradExtraction angle and position

As above0.34 mm

21 µradMagnet and extraction errors

As above

0.36 mm

22 µradNominal beam size [r.m.s.]

0.53 mm

53 µradEffective beam size [r.m.s.]

0.64 mm

57 µrad7-11 November 2003

NBI 2003
Presentation by Malika Meddahi.

15Beam stability at the target (3)Horizontal plane spot size is dominated by extraction errors
Vertical beam spot size is not increased, vertical beam position
is determined by trajectory errors.

7-11 November 2003

NBI 2003
Presentation by Malika Meddahi.

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Overall beam stability at the target (4)Injection and magnet errors(horizontal σ at target)
Total BPM rms incertainty
Target overall precision

0.36 mm0.32 mm (?)
0.30 mm (?)

Total:~0.60 mmFor β=10 m, nominal σbeam = 0.53 mm
On target first 2 rods (5 mm diameter) :2.5 mm – (3σbeam + 0.6mm) = 0.31 mm
On target following rods (4 mm diameter) :2.0 mm – (3σbeam + 0.6mm) = -0.19mm
7-11 November 2003

NBI 2003
Presentation by Malika Meddahi.

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Need of a collimator (1)7-11 November 2003

NBI 2003
Presentation by Malika Meddahi.

18

9mm
7mm
75.55
3.5
4.5

3.2+/- 6 σ

10.3m+/- 6 σ

3.2
3.5
4.5

5.5

5
77mm
14 mm diameter
Collimator
7-11 November 2003

NBI 2003
Presentation by Malika Meddahi.

9mmHorn neck19Summary
Beam dynamics studies confirmed earlier preliminary studies.
Results on trajectory corrections, apertures studies, beam stabilities,
need of a collimator to protect the horn neck.
Proton beam line “on schedule”

General services:
Equipment:
Cold check-out:
Test with beam:

7-11 November 2003

October 2004 to July 2005
August 2005 to January 2006
Feb-March 2006
April 2006

NBI 2003
Presentation by Malika Meddahi.

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