LINAC 2004
XXII International Linear Accelerator Conference
Lübeck, Germany, 17 August 2004
CLIC Magnet Stabilization Studies
(TUP88)
R. Assmann, W. Coosemans, G. Guignard,
S. Redaelli, D. Schulte, I. Wilson, F. Zimmermann
CERN AB-ABP
Geneva, Switzerland
1.
2.
3.
4.
Introduction
CLIC Stability Study - experimental setup
Highlights of experimental achievements
Conclusions
1. Introduction - Stability issues in linear colliders
Ne = particles per bunch
Nb = number of bunches
frep = repetition frequency
x,y = colliding beam sizes
Pb = beam power
CLIC:
Luminosity in linear colliders:
Ecm = 3 - 5 TeV
L = 0.8 x 1035 cm-2s-1
Pb 2 x 15 MW
x x y = 60 nm x 0.7 nm
The luminosity depends strongly on
the relative beam-beam offset:
Final focus
quadrupole
Final focus
quadrupole
y
Beam 1
*IP
Final focus quads must be
stable to a fraction of the
colliding beam size!!
Beam 2
Tolerances for 2% luminosity reductions
S.R., LINAC04
Magnet
Linac
Final Focus
Nmagnet
2600
2
fmin
4 Hz
4 Hz
Ix
14 nm
4 nm
Iy
1.3 nm
0.2 nm
Is this really
achievable?
page 2
2. CLIC Stability Study
Activities from January 2001 to December 2003
People: R. Assmann, W. Coosemans, G. Guignard,
S. Redaelli, D. Schulte, I. Wilson, F. Zimmermann
Goal:
Demonstrate the feasibility of colliding
nanometre-size particle beams in CLIC
How well can we stabilize magnets in a
real accelerator environment?
Our approach: use state-of-the-art stabilization devices to stabilize CLIC
prototype quadrupoles in a normal working environment.
S.R., LINAC04
page 3
The CLIC test stand for vibration measurements and magnet stabilization:
The experimental
setup includes:
S.R., LINAC04
• Sensors for vibration measurements (geophones)
• Honeycomb table (virtually) with no internal resonances
• Prototypes accelerator magnets
• State-of-the-art stabilization equipment
• Stretched-wire system for alignment measurements
page 4
3. Achieved quadrupole stability
RMS vibrations above 4 Hz
Quad Ground
[nm]
[nm]
Vertical
0.43
6.20
Horizontal
0.79
3.04
Longitud.
4.29
4.32
Integrated RMS motion [ nm ]
Integrated vertical RMS motion versus frequency
10
Floor (Normal working area)
1.3 nm
1
Quadrupole
0.2 nm
0.1
Toleran.
of linac
quads
Toleran.
of FF
quads
Beam-based
feedbacks correct
motion below 4Hz
0.01
1
4 Hz
10
100
Frequency [Hz]
CLIC prototype magnets stabilized to the sub-nanometre level !!
Above 4Hz: 0.43 nm on the quadrupole instead of 6.20 nm on the ground.
S.R., LINAC04
page 5
Vertical RMS motion above 4 Hz [ nm ]
S.R., LINAC04
12
0
2 Quadrupole
Saturday
Friday
Thursday
Wednesday
Tuesday
Monday
Sunday
Saturday
Friday
Thursday
14
19:35
03:15
10:55
18:35
02:15
09:55
17:35
01:15
08:55
16:35
00:15
07:55
15:35
23:15
06:55
14:35
22:15
05:55
13:35
21:15
04:55
12:35
20:15
03:55
11:35
19:15
02:55
10:35
18:15
01:55
09:35
Ok, this is good. But is it stable?
Jeûne Genevois
Day
10
10 nm
Ground
8
6
4
Linac tolerance
1.3 nm
Time
Quadrupole vibrations kept below the 1 nm level
over a period of 9 consecutive days!
page 6
4. Conclusions
The CLIC Stability Team has demonstrated the principle feasibility of
colliding nanometre-size beams in future linear accelerators like CLIC:
For the first time, a prototype quadrupole was stabilized
to 0.5 nm above 4 Hz in a normal working area.
Stabilization below 1 nm continuously for several days.
Horizontal stability within tolerances.
Simulations of time-dependent CLIC luminosity indicate that
70% of the nominal luminosity can be achieved!
Outlook
Stabilization performance on more realistic quadrupole prototypes
Study integration of tested devices in the CLIC detector region
S.R., LINAC04
page 7