Transcript Linear Colliders R. Brinkmann, DESY EPS-HEP Conference, Aachen, July 17, 2003 EPS-HEP Aachen 2003 R.

Linear Colliders
R. Brinkmann, DESY
EPS-HEP Conference, Aachen, July 17, 2003
EPS-HEP Aachen 2003
R. Brinkmann, DESY
The energy and luminosity challenges for
a future e+e- linear collider:
“It’s only an order of magnitude in energy (0.5  1
TeV) and three to four orders of magnitude in
luminosity (>1034 cm-2 s-1) from the SLC…”
EPS-HEP Aachen 2003
R. Brinkmann, DESY
Lessons from the SLC
• Sophisticated on-line modeling of non-linear
beam physics.
• Correction techniques (trajectory and emittance),
from hands-on by operators to fully automated
control, slow/fast feedback theory and practice.
10
10
9
9
8
8
sX * sy
7
6
6
5
5
2
7
4
SLC Design
(sx * sy)
4
sX
3
3
sY
2
2
1
1
0
0
1985
1990 1991 1992 1993 1994 1996 1998
Year
EPS-HEP Aachen 2003
R. Brinkmann, DESY
s x*s y (microns )
New Territory in Accelerator Design and
Operation
Beam Size (microns)
IP Beam Size vs Time
FFTB beamline at the
end of the SLAC linac.
FFTB
Collaboration
BINP (Novosibirsk/Protvino)
DESY
Fermilab
10
IBM
1997
B
Kawasaki
KEK
LAL (Orsay)
Number of Occurrences
8
6
4
2
MPI(Munich)
0
0
25
50
75
Beam Size (nm)
Rochester
SLAC
EPS-HEP Aachen 2003
1994
Vertical beam size of 60-70 nm …
demagnification needed for any LC.
R. Brinkmann, DESY
100
Linear Collider Parameter Overview
f / GHz
E-cms / GeV
g / MV/m
Lumi / 1034
Power p. beam
/ MW
sy at IP / nm
Beamstrahlung
dB / %
Site length / km
Site power /
MW
Cost§ (stage-I)
NLC/JLC
11.4
500 – 1000
TESLA
1.3
500 – 800
50
2–3
6.9 – 13.8
SLC
2.9
100
23 – 35
3.4 – 5.8
11.2 – 17
CLIC
30
3000 –
5000
150
~10
~15
2.7 – 2.1
3.2 – 4.3
5 – 2.8
3.4 – 7.5
1
21
500
<0.1
30
195 – 350
33
140 – 200
~35
~400
3.5
~3.5B$
3.14B€+7k p.y.
~20
.0003
0.04
?
§ numbers quoted at Snowmass 2001, no pre-operation, escalation and
contingency included
EPS-HEP Aachen 2003
R. Brinkmann, DESY
International Linear Collider Technical Review Committee
2nd Report 2003 (480 pages), Chair: G. Loew, SLAC
www.slac.stanford.edu/xorg/ilc-trc/2002/2002/report/03rep.htm
• Asses technical status of 500 GeV LC designs
• Potential for reaching higher energies
• Identify R&D work to be done  ranking list
R1(feasibility demonstration) … R4(desirable for
technical/cost optimisation)
EPS-HEP Aachen 2003
R. Brinkmann, DESY
500 ( 800) GeV e+e- Linear
Collider
Based on superconducting linac
technology
EPS-HEP Aachen 2003
R. Brinkmann, DESY
Why superconducting?
• High efficiency ACbeam (>20%, ~10% normal c.)
• Low frequency:
– Long pulses with low RF peak power
– Small beam perturbations from wakefields
– Intra-train feedback on beam orbit, energy, luminosity…
• First proposed in 1960s (M. Tigner)… show stopper
was too low acc. Gradient, too high cost
EPS-HEP Aachen 2003
R. Brinkmann, DESY
Accelerating gradient on test stand reached 25 MV/m on
average for 1999/2000 cavity production
cw-cavity tests, 1st and best results
35
best test
g [MV/m]
30
25
20
15
10
1st test
5
0
1/1/95
5/15/96
9/27/97
2/9/99
date of measurement
EPS-HEP Aachen 2003
R. Brinkmann, DESY
6/23/00
Test of complete accelerator modules in the TTF linac at
DESY (>13,000h beam operation 1997 - 2003)
EPS-HEP Aachen 2003
R. Brinkmann, DESY
Higher performance cavities: energy reach  800 GeV
1st step: no add. investment, 2nd step: add cryo+RF power
TESLA luminosity vs. cm-energy, baseline & upgrade
L / 10^34 cm^-2 s^-1
7
6
5
4
no add. cost
3
RF & cryo upgrade
2
1
0
400
500
600
700
800
900
E_cm / GeV
EPS-HEP Aachen 2003
R. Brinkmann, DESY
1000
Improvement of Nb surface quality with electro-polishing
(pioneering work done at KEK)
BCP
EP
• Several single cell cavities at g > 40 MV/m
• 4 nine-cell cavities at ~35 MV/m
EPS-HEP Aachen 2003
R. Brinkmann, DESY
CHECHIA test in pulsed mode
TESLA 500 –
800 design
EPS-HEP Aachen 2003
R. Brinkmann, DESY
NLC
X-band technology
(SLAC/KEK & coll. Inst.)
SLC-like 20MV/m, 3 GHz  50MV/m (65 unloaded), 11.4GHz
EPS-HEP Aachen 2003
R. Brinkmann, DESY
The NLCTA with 1.8 m accelerator
structures (ca 1997).
Demonstration of Xband concept,
wakefield control,
beamloading
compensation,…
But: acc. Gradient
limited < 40 MV/m
EPS-HEP Aachen 2003
R. Brinkmann, DESY
Structure damage from RF breakdown
EPS-HEP Aachen 2003
R. Brinkmann, DESY
Operation History of Several Test Structures
90
Unloaded Acceleration Gradient
(MV/m)
80
Damage
( )
6
17
Snowmass 2001
<1
3.5
70
60
50
40
30
20
10
0
DDS3
Vg = 12% c
DS2S
Vg = 5% c
T20/T105
Vg = 5% c
T53’s
Vg = 3% c / 5% c
1500 hrs
1700 hrs
500 hrs
500 hrs
(In Progress)
Hours of Operation at 60 Hz
EPS-HEP Aachen 2003
R. Brinkmann, DESY
Test Structure Run History
(T-Series 2003, not final version for linac)
Unloaded Gradient (MV/m)
1 Trip per 25 Hrs
NLC/JLC Goal:
Less than 1 trip per 10 Hrs at 65 MV/m
400 ns Pulse Width
No Observed Change in Microwave Properties
Time with RF On (hr)
EPS-HEP Aachen 2003
R. Brinkmann, DESY
CLIC two-beam accelerator approach
CERN & coll. Inst.
EPS-HEP Aachen 2003
R. Brinkmann, DESY
EPS-HEP Aachen 2003
R. Brinkmann, DESY
P_rf and E_acc at CTF-2 vs pulse length
CAS E_acc / MV/m
160
320
140
120
280
240
CTF-2
100
80
CLIC 3TeV
200
160
60
40
120
80
20
0
40
0
1
10
100
CAS gradient/MV/m
CLIC design E_acc
peak power/MW
CLIC design P_rf
1000
rf pulse / ns
Successful demonstration of 30 GHz twobeam concept at CTF-II
But: serious structure damage from RF
breakdown at high gradient
EPS-HEP Aachen 2003
R. Brinkmann, DESY
Systematic study of high-g RF breakdown/damage
problem:
RF breakdown vs. frequency
damage vs. different material of irises (Cu, W, Mo)
EPS-HEP Aachen 2003
R. Brinkmann, DESY
Peak Accelerating field (MV/m)
200
150
100
3.5 mm tungsten iris
3.5 mm tungsten iris after ventilation
3.5 mm copper structure
3.5 mm molybdenum structure
CLIC goal loaded
CLIC goal unloaded
50
0
0
EPS-HEP Aachen 2003
0.5
1
1.5
No. of shots
R. Brinkmann, DESY
2
2.5
3
x 10
6
CTF3 (under construction)
LOW CURRENT BUNCH
TRAIN
COMBINATION
streak camera images of beam in the ring
1st turn - 1st bunch train from linac
time
2nd turn
• First demonstration in June 2002
• Tested combination factors 4 & 5
3rd turn
Final intensity profile
4th turn
EPS-HEP Aachen 2003
R. Brinkmann, DESY
combination factor 4
Luminosity challenge: beam quality & stability
• Damping rings: emittances required ~factor 3…5
below best values obtained to date at SR sources
and ATF-DR (KEK)
• Wakefields  fRF3  tighter alignment tolerances &
more precise beam diagnostics for higher frequency
linacs
• Dynamic stability: higher rep. Rate of n.c. linacs
compensates (partially) for tighter tolerances
EPS-HEP Aachen 2003
R. Brinkmann, DESY
LC DR design emittances vs. achievements
12
eps_y / pm
10
ATF
ESRF
8
6
X-band
ALS
4
TESLA
2
CLIC
0
0
2
4
6
eps_x / nm
EPS-HEP Aachen 2003
R. Brinkmann, DESY
8
10
12
Luminosity stability: “Start-to-end” simulations,
including ground motion
50 s
EPS-HEP Aachen 2003
2s
R. Brinkmann, DESY
Power spectral density
Ground motion: varies form “quiet” (model A) to “noisy”
(model C), depending on site
EPS-HEP Aachen 2003
1
p( f )  4
f
R. Brinkmann, DESY
Seismic measurements: TESLA LC central site (Ellerhoop) more
quiet than HERA (data taken on a Monday, 0.00h – 1.00h)
HERA
tunnel
Ellerhoop
(barn)
EPS-HEP Aachen 2003
R. Brinkmann, DESY
There are a number of subtle effects in LC beam
dynamics… e.g. the banana effect (amplification of
bunch deformations during collision): (TESLA beam-beam
simulation)
EPS-HEP Aachen 2003
R. Brinkmann, DESY
Choice of technology: hybrid collider??
superconducting
Normal conducting
Doesn’t work….
EPS-HEP Aachen 2003
R. Brinkmann, DESY
Towards a Global Linear Collider…
• International Linear Collider Steering Committee
(Chair: M. Tigner, Cornell) will select the linac
technology with the help of a group of “Wise persons”
(~ mid 2004)
• Establish GLC design group  Technical Design
Report as basis for site selection and project
approval
• Worldwide organisation at political level
• Start project construction ~2007
EPS-HEP Aachen 2003
R. Brinkmann, DESY