Transcript Summary of Session 1: Optics and Layout

Summary of Session 1:
Optics and Layout
P. Raimondi
US-LARP Progress
on
IR Upgrades
Tanaji Sen
FNAL
Topics
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IR optics designs
Energy deposition calculations
Magnet designs
Beam-beam experiment at RHIC
Strong-strong beam-beam simulations
Future plans
IR designs
• Quadrupoles first – extension of baseline
• Dipoles first – triplet focusing
• Dipoles first – doublet focusing (appealing
but a new world for the beam-beam)
All solutions in principle duable in terms of
quads gradients and stay clear
Energy deposition more tricky
Energy Deposition in Quads First
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Energy deposition and radiation are major issues for new IRs.
In quad-first IR, Edep increases with L and decreases with quad aperture.
– Emax > 4 mW/g, (P/L)max > 120 W/m, Ptriplet >1.6 kW
at L = 1035 cm-2 s-1.
– Radiation lifetime for G11CR < 6 months at hottest spots. More radiation
hard material required.
N, Mokhov
A. Zlobin et al, EPAC 2002
Energy deposition in dipoles
Problem is even more severe for dipole-first IR.
Cosine theta dipole
On-axis field sprays particles
horizontally
power
deposition is concentrated in
the mid-plane
L = 1035 cm-2 s-1
Emax on mid-plane (Cu spacers)
~ 50 mW/g;
Emax in coils ~ 13 mW/g
Quench limit ~ 1.6 mW/g
Power deposited ~3.5 kW
Power deposition at the non-IP end of D1
N. Mokhov et al, PAC 2003
Open mid-plane dipole
R. Gupta et al, PAC 2005
Open mid-plane => showers
originate outside the coils; peak
power density in coils is reasonable.
Tungsten rods at LN temperature
absorb significant radiation.
Magnet design challenges addressed
• Good field quality
• Minimizing peak field in coils
• Dealing with large Lorentz forces w/o a
structure between coils
• Minimizing heat deposition
• Designing a support structure
RHIC – Wire compensator
New LARP Task for FY06
RHIC provides unique environment
to study experimentally long-range
beam-beam effects akin to LHC
Possible location of wire
IP6
Parasitic interaction
Phase advance from parasitic to wire = 6o
Proposal: Install wire compensator
In summer of 2006, downstream of
Q3 in IR6
Proposed Task
Design and construct a wire
compensator
Install wire compensator on
movable stand in a ring
First study with 1 proton bunch in
each ring with 1 parasitic at flat top.
Compensate losses for each
separation with wire
Test robustness of compensation
w.r.t current ripple, non-round
beams, alignment errors, …
RHIC – Wire compensator
New LARP Task for FY06
RHIC provides unique environment
to study experimentally long-range
beam-beam effects akin to LHC
Possible location of wire
IP6
Parasitic interaction
Phase advance from parasitic to wire = 6o
Proposal: Install wire compensator
In summer of 2006, downstream of
Q3 in IR6
Proposed Task
Design and construct a wire
compensator
Install wire compensator on
movable stand in a ring
First study with 1 proton bunch in
each ring with 1 parasitic at flat top.
Compensate losses for each
separation with wire
Test robustness of compensation
w.r.t current ripple, non-round
beams, alignment errors, …
Possible Dipole First Options and
Challenges
motivation and advantages:
- alternative solution to nominal layout  pro & cons
- early beam separation  less long range interactions
- no crossing-angle bump inside triplet magnets
 requires less aperture inside triplet magnets
(assuming equal b-function values)
 no feed-down errors & simpler correction
options
 local field error correction per triplet assembly
- reduced radiation inside the triplet magnets
 relaxed magnet design and more aperture
LHC LUMI 2005; 1.9.2005; Arcidosso
Oliver Brüning
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Possible Dipole First Options and
Challenges
dis-advantages & challenges:
- increased quadrupole distance from IP  larger bmax
 requires larger aperture inside triplet magnets
 implies larger chromatic aberrations
-large radiation levels for dipole magnets
 magnetic TAS (spectrometer dipole & absorber)
 transfers design challenges for triplet quadrupole
to
D1
is itdipole
a validdesign
assumption that large aperture, high
field dipole magnets are easier to design
compared
to large aperture, high gradient quadrupoles?
LHC LUMI 2005; 1.9.2005; Arcidosso
Oliver Brüning
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Long Range Beam-Beam Interactions
beam separation:
-the nominal IR layout features 32 long range beam-beam
interactions for a bunch spacing of 25ns:
D1
Q3 Q2
24 m
35 m
Q1
ca. 10 long range interactions
IP
Q1 Q2 Q3
D1
2 x 23 m
35 m
13 long range
interactions
24 m
ca. 10 long range interactions
 all layout options benefit from reduced L*!
 changing the sequence of D1 and triplet magnets
cuts
the number of long range interaction in half!
LHC LUMI 2005; 1.9.2005; Arcidosso
Oliver Brüning
12
Options For a Dipole First Layout
1) Simple swap of D1 and triplet
magnets
IP
Q3 Q2 Q1
D1
D1
Q3
Q1 Q2
2 x 23 m
separated beams
13 long range
interactions
separated beams
 changing the sequence of D1 and triplet magnets
cuts
the number of long range interaction in half!
 Increased L* increases beam size in triplet magnets
LHC LUMI 2005; 1.9.2005; Arcidosso
Oliver Brüning
13
Aperture Requirements
single bore design requires aperture for beam separation:
-10 s beam envelope
-10 s beam separation
-20% beta beat
-closed orbit error (4
mm)
-alignment errors
+ beam screen (3mm)
d(triplet) > 33 s + 7 mm
10 s
10 s
10 s
with s = b e + D2 d2
LHC LUMI 2005; 1.9.2005; Arcidosso
Oliver Brüning
14
Aperture Requirements
2-in-1 magnet design requires no aperture for beam separatio
-10 s beam envelope
-20% beta beat
-closed orbit error (4
mm)
-alignment errors
+ beam screen 3mm?
10 s
10 s
(economic use of space
 flat beam screen)
d(triplet) > 22 s + 7 mm
with s = b e + D2 d2
LHC LUMI 2005; 1.9.2005; Arcidosso
Oliver Brüning
15
Summary
beam-beam interaction:
 dipole first layout reduces number of long range
beam-beam interactions
radiation:
 any luminosity upgrade requires a TAS upgrade
 a dipole first layout provides efficient magnetic TAS
 a dipole first layout requires 2-in-1 magnets with central
whole for neutron flux!
dipole first layout options:
 four options have been identified so far but only one is
being studied in detail
LHC LUMI 2005; 1.9.2005; Arcidosso
Oliver Brüning
16
Summary
aperture:
 all IR upgrade options benefit from smaller L*
 dipole first layout does not require larger magnet aperture
and allows an efficient implementation of beam screens
optics:
 chromaticity increases with b-funtion inside triplet magnet
 dipole first layout implies larger chromatic aberrations
aspects related to crossing angle generation:
 2-in-1 magnet design allows large crossing angles (v-xing?
aspects related to field error corrections:
 2-in-1 magnet design provides efficient field error correctio
LHC LUMI 2005; 1.9.2005; Arcidosso
Oliver Brüning
17
Possible Quadrupole-first
Options with beta* <= 0.25 m
J-P Koutchouk , CERN
Requirements and objectives
The IR upgrade design cannot be split in slices, as before. All
requirements must be incorporated from the start and the
technology is leading the dance. →Need for a global
model
1. A clear view of the performance objective
a) Make up for a beam current that does not reach nominal
value
b) Contribute in a significant way to the factor 10 in lumi
increase.
c) The ideal being a lego system that allows both.
2. Be ready for installation in 2012/2015
3. Robust design to cope for unknowns if a new
technology is to be used.
4. Maximize the probability for an efficient take-off
5. Depending on the objective, the behavior versus the energy
deposition and radiation lifetime are obviously major issues.
General Advantages and
Drawbacks
Advantages
Drawbacks
Minimization of βmax, optical
aberrations and sensitivity:
most robust optics solution.
Larger potential for beta*
reduction
The magnet most exposed to
debris is as well the less
sensitive (sweeps less)
Builds on the operational
experience of 1rst
generation: potential gain in
∫dt
Strong coupling to other
upgrade options thru Xing
angle and aperture: goal must
be well defined
A priori, long-range beambeam stronger
The two LHC rings remain
coupled: operations more
involved but large experience
The yield from a reduced beta*
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Luminosity
increase vs
beta*:
rel. luminosity
4.5
4
3.5
3
2.5
2
1.
no Xing angle,
2.
nominal Xing and
bunch length,
3.
BBLR?,
4.
Bunch length/2
1.5
0.1
0.2
0.3
beta
0.4
0.5
For both options and even more for the Q first, pushing
the low-beta makes sense if simultaneously the impact of
the Lumi. geometrical factor is acted upon.
Partial conclusion on an
upgrade using Nb3Sn
technology (1)
• A solution very similar to the baseline triplet exists with coil
diameter of 95 mm, dipole length of 5.5 m with a 1.5 increase
in .
•For the full upgrade (Ib×2), the diameter and length required
increase to 121mm and 6.7m. With BBLR/HH Xing, this
increase is not needed and  increases further.
•Luminosity and feasibility both increase when pushing the
triplet towards the IP:
Back to the Xing angle issue
An “easy” way to reduce
or cancel the Xing angle
at the IP and gain 20%
to 50% in luminosity.
Orbit
corrector
Q1
Q3
Q2
Is it possible for the
detectors?
Conclusions (1)
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The baseline triplet or “small” variations around
it offer a very modest potential for luminosity
improvement.
The NbTi(Ta) technology can offer an
improvement in luminosity of the order of 40%
but requires some 120 mm diameter at 23m
from the IP. At 18m, this is reduced to 105 mm.
This option does not seem compatible with an
increase of the beam intensity.
These limits are removed by the Nb3Sn
technology. A significant improvement in the
performance and feasibility is observed with
BBLR and when moving the triplet toward the IP.
• Several solutions are presented each with its own
sets of benefits
• The more appealing cases require intense R&D (e.g.
Nb3Sn quads or crab cavities)
• R&D required in almost all the cases to cope with the
increased heat load
• Symulations of all the crytical issues (optics,
background etc) very detailed and useful to
understand where to go
• Critical choices for the more ambitious improvement
strongly linked to R&D results and LHC experience
• Probably still to early to reduce the number of
options to one (or even two)
Optical requirements for the
magnetic lattice of the high
energy injectors (SSPS in the
SPS tunnel)
G. Arduini – CERN-AB/ABP
Outline
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Constraints from SPS tunnel
Expected functionalities
Arc aperture
SPS to SSPS transfer
Slow extraction in the SSPS
Fast extraction
Other issues
Constraints for SSPS in the SPS
tunnel
RF
BI – TAIL CLEANING
INJ. – BEAM DUMP
Constraints for SSPS in the SPS
tunnel
Required functionalities
1.
2.
3.
4.
5.
Injection
Acceleration
Fast extraction 1 to LHC (LSS4 if we want to use the TI8 tunnel)
Fast extraction 2 to LHC (LSS6 if we want to use the TI2 tunnel)
Slow resonant extraction (LSS2 if we want to use the TT20 tunnel
to North area)
6. Beam dump
7. Betatron collimation
8. Momentum collimation
Need to combine 2 functions in at least 2 LSSs
Arc aperture
• Peak dispersion 4.5 to 3 m  Required halfaperture in the arcs: 46 / 82 (H) × 27 (V) mm (10
% gain in the aperture at injection)
• Useful if together with increased bH at ES
proper insertions with independent powering of
the quadrupoles in the dispersion suppressor, in
the straight section and possibly in 1 arc cell
might be required.
SPS to SSPS transfer
• Cohabitation with the SPS in the SPS tunnel will imply
hosting the SPS fast extraction to the SSPS and the
injection in the SSPS in the same straight section
• In order to gain space might need to install the SPS fast
extraction kickers in the missing dipole section providing
an H kick towards a Lambertson magnet in the following
dispersion free section bending the beam vertically
• The Injection in the SSPS could be “symmetric” to the
SPS extraction. This solution might be incompatible with
a reduction of the cell length.
Tentative summary
• Only a few issues have been sketched
• Constraint on the length of the straight sections and
increased energy impose to design dedicated insertions
(no simple FODO lattice)
• Slow-extraction and dispersion drive and/or contribute
significantly to the aperture in the arcs  proper
matching and insertion design
• Cohabitation of different functionalities in the same
straight section is necessary and implications need to be
studied