1. Machine Plans for the LHC Upgrade
Frank Zimmermann
CERN, AB/ABP
Thanks to Ralph Assmann, Michael Benedikt, Rama Calaga, Ulrich Dorda, Angeles Faus-Golfe, Roland Garoby,Jean-Pierre Koutchouk, Javier Resta, Francesco Ruggiero, Rogelio Tomas, Walter Scandale
ATLAS Upgrade Workshop, 1 October 2006

2. ATLAS Upgrade Workshop, 1 October 2006
Large Hadron Collider (LHC)
c.m. energy 14 TeV
7x Tevatron
design luminosity
1034 cm-2s-1
~100x Tevatron
transverse beam
energy density
1 GJ/mm2
~1000x Tevatron
nominal LHC already a very challenging machine!
ATLAS Upgrade Workshop, 1 October 2006

3. ATLAS Upgrade Workshop, 1 October 2006
outline
1) motivation
2) pushing the luminosity
3) beam scenarios & upgrade schemes
- luminous region
- lifetime & integrated luminosity
4) IR upgrade
5) intensity limitations
6) injector upgrade
7) towards higher energy
8) questions to ATLAS
9) summary
ATLAS Upgrade Workshop, 1 October 2006

4. ATLAS Upgrade Workshop, 1 October 2006
(1) motivation
ATLAS Upgrade Workshop, 1 October 2006

5. time scale of an LHC upgrade
Jim Strait, 2003
radiation
damage limit
~700 fb-1
time to halve error
integrated L
L at end of year
ultimate
luminosity
design
luminosity
(1) life expectancy of LHC IR quadrupole magnets is estimated to be <10 years due to high radiation doses
(2) statistical error halving time exceeds 5 years by
→ it is reasonable to plan a machine luminosity upgrade based on new low-b IR magnets around ~
ATLAS Upgrade Workshop, 1 October 2006

6. ATLAS Upgrade Workshop, 1 October 2006
European Accelerator Network on
November 2004: 1st CARE-HHH-APD Workshop (HHH-2004) on
‘Beam Dynamics in Future Hadron Colliders and Rapidly Cycling High-Intensity Synchrotrons’, Proc. CERN
September 2005: 2nd CARE-HHH-APD Workshop (LHC-LUMI-05)
on ‘Scenarios for the LHC Luminosity Upgrade’, Proc. CERN
October 2006: 3rd CARE-HHH-APD Workshop (LHC-LUMI-06)
‘Towards a Roadmap for the Upgrade of the LHC and GSI Accelerator Complex’ .../LUMI-06/LHC-LUMI-06-invitation.pdf
High Energy
High Intensity
Hadron Beams
ATLAS Upgrade Workshop, 1 October 2006

7. ATLAS Upgrade Workshop, 1 October 2006
upgrade stages
push LHC performance w/o new hardware
luminosity →2.3x1034 cm-2s-1, Eb=7→7.54 TeV
LHC IR upgrade
replace low-b quadrupoles after ~7 years
peak luminosity →4.6x1034 cm-2s-1
LHC injector upgrade
peak luminosity →9.2x1034 cm-2s-1
LHC energy upgrade
Eb→13 – 21 TeV (15 → 24 T dipole magnets)
ATLAS Upgrade Workshop, 1 October 2006

8. (2) pushing the luminosity
ATLAS Upgrade Workshop, 1 October 2006

9. ATLAS Upgrade Workshop, 1 October 2006
luminosity
parameters that enter:
ATLAS Upgrade Workshop, 1 October 2006

10. ATLAS Upgrade Workshop, 1 October 2006
there are many parameter constraints, for example
e limited by arc aperture and field quality at injection
b* limited by final triplet aperture & crossing angle
& long-range beam-beam & collimation
& chromatic correction (& beam lifetime)
qc limited by geometric luminosity loss & long-range
collisions & triplet aperture & triplet field errors
nbNb ~ total current, limited by collimation, machine
protection, beam dump
nb limited by electron cloud heating
Nb limited by image-current heating & collimation &
pile-up events
ATLAS Upgrade Workshop, 1 October 2006

11. ATLAS Upgrade Workshop, 1 October 2006
nominal crossing angle “at the edge”
Piwinski angle
luminosity reduction factor
nominal LHC
ATLAS Upgrade Workshop, 1 October 2006

12. ATLAS Upgrade Workshop, 1 October 2006
another important constraint is the (head-on) beam-beam
tune shift
total beam-beam tune shift at two
IPs with alternating crossing
DQbb < , beam-beam limit for hadron colliders (from experience)
ATLAS Upgrade Workshop, 1 October 2006

13. ATLAS Upgrade Workshop, 1 October 2006
for operation at the beam-beam limit
luminosity equation can be rewritten as
injector upgrade
LHC+
injector
changes
LHC +
injector
changes
IR upgrade
ATLAS Upgrade Workshop, 1 October 2006

14. (3) beam scenarios & upgrade schemes
ATLAS Upgrade Workshop, 1 October 2006

15. ATLAS Upgrade Workshop, 1 October 2006
parameter
symbol
nominal
ultimate
baseline
alternative
backup
transverse emittance
e [mm]
3.75
7.5
protons per bunch
Nb [1011]
1.15
1.7
3.4 6
bunch spacing
Dt [ns] 25
12.5 75
beam current
I [A]
0.58
0.86
1.72 1
longitudinal profile
Gauss
flat
rms bunch length
sz [cm]
7.55
3.78
14.4
beta* at IP1&5
b* [m]
0.55
0.5
0.25
full crossing angle
qc [murad]
285
315
445
630
430
Piwinski parameter
qcsz/(2*sx*)
0.64
0.75
2.8
peak luminosity
L [1034 cm-2s-1]
2.3
9.2
8.9
events per crossing 19 44 88
176
510
Initial lumi lifetime
tL [h] 22 14
7.2
4.5
effective luminosity
(Tturnaround=10 h)
Leff [1034 cm-2s-1]
0.46
0.91
2.7
2.1
Trun,opt [h]
21.2
17.0
12.0
9.4
(Tturnaround=5 h)
0.56
3.6
2.9
15.0
8.5
6.6
e-c heat SEY=1.4(1.3)
P [W/m]
1.07 (0.44)
1.04 (0.59)
13.34 (7.85)
2.56 (2.05)
0.26
SR heat load K
PSR [W/m]
0.17
0.29
image current heat
PIC [W/m]
0.15
0.33
1.87
3.74
0.96
gas-s. 100 h (10 h) tb
Pgas [W/m]
0.04 (0.38)
0.06 (0.56)
0.113 (1.13)
0.11 (1.13)
0.07 (0.7)
ATLAS Upgrade Workshop, 1 October 2006

16. ATLAS Upgrade Workshop, 1 October 2006
bunch structure
plus:
can use crab cavities
event pile up tolerable
more (&shorter) bunches
nominal & ultimate LHC
concerns:
e-cloud
LRBB
impedance
~12.5 ns
upgrade
path 1
25 ns
upgrade
path 2
upgrade
path 3
longer (&fewer) bunches
25 ns
bigger (&shorter?)
bunches
75 ns
plus:
no e-cloud?
less current
concerns:
event pile up
impedance
concerns:
impedance heating,
LR compensation,
may need 1-TeV
injector
plus:
limited e-cloud
limited pile up
transitions by bunch merging or splitting;
new rf systems required for cases 1 and 3
ATLAS Upgrade Workshop, 1 October 2006

17. ATLAS Upgrade Workshop, 1 October 2006
luminosity upgrade: baseline schemes
1.0
reduce sz
by factor ~2
using higher
frf & lower e||
(larger qc ?)
0.58 A
qc>qmindue to LR-bb
increase Nb
increase Ff
BBLR
compen-sation
yes bb
limit?
crab cavities
reduce qc
(squeeze b*)
2.3 no
0.86 A
reduce b* by
factor ~2
new IR
magnets
use large qc
& pass each beam
through separate
magnetic channel
4.6
0.86 A
if e-cloud, dump &
impedance ok
increase either nb or
(Nb&e) by factor ~2
simplified IR design
with large qc
peak luminosity gain
9.2
beam current
1.72 A
ATLAS Upgrade Workshop, 1 October 2006

18. ATLAS Upgrade Workshop, 1 October 2006
luminosity upgrade: backup scheme
decrease Ff
reduce b* by
factor ~2
new IR
magnets
1.0
increase szqc
0.58 A
flatten profile
increase Nb
reduce #bunches
by 1/3 to limit total
current
yes no
8.9 ?
luminosity gain
1.0 A
beam current
ATLAS Upgrade Workshop, 1 October 2006

19. ATLAS Upgrade Workshop, 1 October 2006
due to the crossing angle, colliding long
bunches does not mean the events are spread
out over a large area
rms length of luminous region
nominal
ultimate
baseline
alternative
backup
sl [cm]
4.5
4.3
2.1
3.5
luminous region is largest for nominal LHC
ATLAS Upgrade Workshop, 1 October 2006

20. ATLAS Upgrade Workshop, 1 October 2006
optimum run time, integrated luminosity, etc.
collisions, gas scattering
intensity evolution for collisions only
intrabeam scattering (IBS) growth
burn-off collision lifetime with s~100 mbarn, nIP~2:
Lpeak=1034 cm-2s-1 in 2808 bunches, Nb~1.15x1011:
t~45 h (luminosity lifetime 22 h)
Lpeak=1035 cm-2s-1 in 5616 bunches, Nb~1.7x1011:
t~14 h (luminosity lifetime 7 h)
tgas > 100 h (luminosity lifetime 50 h)
tIBS~105 h (horizontal emittance growth time;
luminosity lifetime 210 h)
burn-off dominates over gas scattering and IBS
ATLAS Upgrade Workshop, 1 October 2006

21. ATLAS Upgrade Workshop, 1 October 2006
luminosity time evolution
average luminosity
optimum run time →
Lpeak [cm-2 s-1]
beam lifetime teff [h]
Tturnaround [h]
Trun [h]
Int L over 200 days
[fb-1]
1034 45 10 21 79 5 15 97
1035 14 12
473 8
629 6x 8x
ATLAS Upgrade Workshop, 1 October 2006

22. ATLAS Upgrade Workshop, 1 October 2006
(4) IR upgrade
ATLAS Upgrade Workshop, 1 October 2006

23. ATLAS Upgrade Workshop, 1 October 2006
IR upgrade
T. Sen et al., PAC2001
T. Taylor, EPAC02
J. Strait et al., PAC2003
F. Ruggiero et al., EPAC04
goal: reduce b* by factor 2-5
options: NbTi ‘cheap’ upgrade, NbTi(Ta), Nb3Sn
new quadrupoles
new separation dipoles
maximize magnet aperture,
minimize distance to IR
factors driving IR design:
minimize b*
minimize effect of LR collisions
large radiation power directed towards the IRs
crab cavities or beam-beam compensators,
integration of elements inside detector
compatibility with upgrade path
ATLAS Upgrade Workshop, 1 October 2006

24. I R U P G A D E “quadrupoles first” minimum chromaticity
“dipole first”
reduced # LR collisions;
collision debris hits first dipole
N. Mokhov et al.,
PAC2003
“open midplane s.c. dipole”
(studied by US LARP)
ATLAS Upgrade Workshop, 1 October 2006

25. ATLAS Upgrade Workshop, 1 October 2006
IR schemes with D0 dipole deep inside detector (e.g., ~3 m from IP)
triplet magnets
D0 dipole
triplet magnets
D0 dipole
less LR
collisions.
no geometric
lumi. loss
not so short bunches &
near head-on collision
near head-on collision
but large separation
IR schemes with Q0 doublet deep inside detector (7.5 or 13 m from IP)
triplet magnets
triplet magnets
Q0 doublet
BBLR
crab cavity
triplet quads
much easier,
less Q’,
could be
combined
with D0
short bunches &
minimum crossing
angle & BBLR
Q0 doublet
crab cavities &
large crossing angle
ATLAS Upgrade Workshop, 1 October 2006

26. higher-luminosity IR optics
web site
Candidate solutions:
Combined function NbTi magnets with large l* (O. Bruning)
Dipole first options with Nb3Sn (CERN & FNAL)
Quad 1st Nb3Sn (T. Sen)
Quad 1st “pushed” NbTi (O. Bruning, R. Ostojic, F. Ruggiero)
Quad 1st with detector-integrated dipole (J.-P. Koutchouk)
Quad 1st flat beam (S. Fartoukh)
Quad 1st Nb3Sn or NbTi plus crab cavities (R.Tomas & F.Z.)
Detector-integrated quadrupole doublet (E. Laface, W. Scandale, et al)
Rating criteria: aperture, energy deposition, technology,
chromatic correction, beam-beam compensation,…,
risks, development time scales, operational difficulties
ATLAS Upgrade Workshop, 1 October 2006

27. (5) intensity limitations
ATLAS Upgrade Workshop, 1 October 2006

28. ultimate LHC intensity limitations
electron cloud
long-range & head-on beam-beam effects
collimator impedance & damage
injectors
beam dump & damage
machine protection …
ATLAS Upgrade Workshop, 1 October 2006

29. ATLAS Upgrade Workshop, 1 October 2006
electron cloud in the LHC
schematic of e- cloud build up in the arc beam pipe,
due to photoemission and secondary emission
[Courtesy F. Ruggiero]
ATLAS Upgrade Workshop, 1 October 2006

30. ATLAS Upgrade Workshop, 1 October 2006
arc heat load vs. spacing, Nb=1.15x1011, ‘best’ model
R=0.5
cooling capacity
ATLAS Upgrade Workshop, 1 October 2006

31. long-range beam-beam collisions
perturb motion at large transverse amplitudes, where particles come close to opposing beam
may cause high background, poor beam lifetime
increasing problem for SPS, Tevatron, LHC,...
#LR encounters
SPS 9
Tevatron Run-II 70
LHC
120
ATLAS Upgrade Workshop, 1 October 2006

32. ATLAS Upgrade Workshop, 1 October 2006
long-range beam-beam
compensation by wire
prototype wire compensator “BBLR” installed in the SPS
ATLAS Upgrade Workshop, 1 October 2006

33. ATLAS Upgrade Workshop, 1 October 2006
crab cavities
crab cavity x
more effective than
bunch-shortening rf!
crab voltage compared with bunch-shortening rf
ATLAS Upgrade Workshop, 1 October 2006

34. ATLAS Upgrade Workshop, 1 October 2006
crab-cavity timing tolerance jitter tolerances
KEKB
Super-KEKB
ILC
Super-LHC
sx*
100 mm
70 mm
0.24 mm
11 mm qc
22 mrad
30 mrad
10 mrad
1 mrad Dt
6 ps
3 ps
0.03 ps
0.002 ps
(0.02 ps XFEL!)
IP offset of
0.6 nm,
~5x10-5 s*
IP offset of 0.2 sx*
tight jitter tolerance might
prevent this scheme
ATLAS Upgrade Workshop, 1 October 2006

35. graphite collimator impedance renders nominal LHC beam unstable
complex coherent
tune shift plane
+ 43 collimators
resistive wall
& broadband
stability border(s) from
Landau octupoles
LHC is limited to 40% of nominal intensity
until “phase-2 collimation”
Elias Metral
ATLAS Upgrade Workshop, 1 October 2006

36. LHC phase-2 collimation options
high chromaticity and/or transverse feedback (poor lifetime & emittance growth)
consumable low-impedance collimators (rotating metal wheels; prototype from US LARP / SLAC to be installed in 2008)
nonlinear collimation; pairs of sextupoles to deflect halo particles to larger amplitudes & open collimator gaps
use crystals to bend halo particles to larger amplitudes & open collimator gaps
several proposed solutions
ATLAS Upgrade Workshop, 1 October 2006

37. ATLAS Upgrade Workshop, 1 October 2006
Channeling in flat crystal
( Landau and Lifshitz, Mechanics) U0 θ1
Channeled
Y. Ivanov, PNPI
ATLAS Upgrade Workshop, 1 October 2006

38. ATLAS Upgrade Workshop, 1 October 2006
Channeling and reflection in bent crystal U0 θ1 θ3 θ2
Reflected
Channeled
reflecting crystals could
serve as primary collimators
Y. Ivanov, PNPI
ATLAS Upgrade Workshop, 1 October 2006

39. crystal channeling & reflection demonstrated in SPS H8 -12.09.2006
Si-strip
detector
65 m behind
Crystal
400 GeV p
10-mrad
reflection
over 1 mm
distance ↔
~20000 T field!
>99%
efficiency
unperturbed
or scattered
reflected
channeled
ATLAS Upgrade Workshop, 1 October 2006

40. ATLAS Upgrade Workshop, 1 October 2006
(6) injector upgrade
ATLAS Upgrade Workshop, 1 October 2006

41. injector upgrade - motivations
raising beam intensity (higher bunch charge, shorter spacing etc.), for limited geometric aperture, L~eN, may be essential for alternative scheme
reduction of dynamic effects (persistent
currents, snapback, etc.)
→ improvement of turn-around time by
factor ~2, effective luminosity by ~50%
benefit to other CERN programmes
(n physics, b beams,…)
ATLAS Upgrade Workshop, 1 October 2006

42. ATLAS Upgrade Workshop, 1 October 2006
LHC injector upgrade
SPS+
extraction energy 450 GeV →1 TeV
PS2 or PS2+
extraction energy 26 GeV → 50 or 75 GeV
LHC+
injection energy 450 GeV → 1 TeV
Super ISR is alternative to Super PS
Superferric ring “pipetron” in LHC tunnel is
alternative to Super SPS – issue: detector bypass
ATLAS Upgrade Workshop, 1 October 2006

43. ATLAS Upgrade Workshop, 1 October 2006
parameter lists for new injectors under construction
ATLAS Upgrade Workshop, 1 October 2006

44. ATLAS Upgrade Workshop, 1 October 2006
Upgraded CERN Complex
fast cycling dipoles for Super-LHC injectors
Super-LHC
Super-SPS
Super-Transferlines
PS2
PS2?
ATLAS Upgrade Workshop, 1 October 2006

45. (7) towards higher energy
ATLAS Upgrade Workshop, 1 October 2006

46. ultimate LHC “upgrade”: higher beam energy
7 TeV→14 (21) TeV?
R&D on stronger magnets
ATLAS Upgrade Workshop, 1 October 2006

47. ATLAS Upgrade Workshop, 1 October 2006
Six institutes: CCLRC/RAL (UK), CEA/DSM/DAPNIA (France), CERN/AT (International), INFN/Milano-LASA & INFN/Genova (Italy), Twente University (the Netherlands), Wroclaw University (Poland).
Three s.c. wire manufacturers (also contributing financially): Alstom/MSA (France), ShapeMetal Innovation (the Netherlands), Vacuumschmelze (now European Advanced Superconductors, Germany)
develop and construct a large-aperture (up to 88 mm), high-field (up to 15 T) dipole magnet model
that pushes the technology well beyond present LHC limits.
Next European Dipole
European Joint Research Activity
proof-of principle & world record: 16 T at 4.2 K at LBNL (in 10 mm aperture).
(S. Gourlay, A. Devred)
ATLAS Upgrade Workshop, 1 October 2006

48. proposed design of 24-T block-coil dipole for LHC energy tripler
P. McIntyre, Texas A&M,
PAC’05
magnets are
getting
more efficient!
ATLAS Upgrade Workshop, 1 October 2006

49. ATLAS Upgrade Workshop, 1 October 2006
(8) questions to ATLAS
ATLAS Upgrade Workshop, 1 October 2006

50. ATLAS Upgrade Workshop, 1 October 2006
questions to ATLAS
is the back up solution with peak pile up of 500 events per crossing a viable option?
can “slim" s.c. magnets be installed deep inside the upgraded ATLAS detector, and, if so, under which boundary conditions, such as envelope, volume, material, or fringe field?
ATLAS Upgrade Workshop, 1 October 2006

51. ATLAS Upgrade Workshop, 1 October 2006
(9) summary
ATLAS Upgrade Workshop, 1 October 2006

52. ATLAS Upgrade Workshop, 1 October 2006
nominal LHC is extremely challenging
three paths to 10x higher luminosity
LHC experience will determine the choice
IR upgrade alone: factor 2-3 increase; integration of D0 or Q0 in ATLAS? questions of joint interest
raising beam intensity: factor ~4 gain
new injectors: ~3x higher peak & average luminosity; 1st step of energy upgrade
vigorous R&D programme needed
ATLAS Upgrade Workshop, 1 October 2006

53. ATLAS Upgrade Workshop, 1 October 2006
2008: LHC Upgrade Conceptual Design Report
2010: LHC Upgrade Technical Design Report
2015: New IR, Beam-Beam Compensation
>2015: Luminosity ~5x1034 cm-2s-1
Francesco Ruggiero
ATLAS Upgrade Workshop, 1 October 2006

54. thank you for your attention!
ATLAS Upgrade Workshop, 1 October 2006