Transcript US-LARP Progress on IR Upgrades Tanaji Sen FNAL Topics IR optics designs Energy deposition calculations Magnet designs Beam-beam experiment at RHIC Strong-strong beam-beam simulations Future plans Tanaji Sen US-LARP: IR Upgrades.

US-LARP Progress
on
IR Upgrades
Tanaji Sen
FNAL
Topics
IR optics designs
Energy deposition calculations
Magnet designs
Beam-beam experiment at RHIC
Strong-strong beam-beam simulations
Future plans
Tanaji Sen
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US-LARP effort on IR designs
Main motivation is to provide guidance for
magnet designers
Example: aperture and gradient are no longer
determined by beam optics alone. Energy
deposition in the IR magnets is a key component
in determining these parameters
Use as an example for field quality requirements
Examine alternative scenarios
Not intended to propose optimized optics
designs
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IR designs
Quadrupoles first – extension of baseline
Dipoles first – triplet focusing
Dipoles first – doublet focusing
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Triplet first optics
Lattice Vers. 6.2
Nominal β* = 0.5
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β* = 0.25
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J. Johnstone
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Gradients, beta max – quads first optics
Quad
B’[T/m]
Left
B’[T/m]
Right
βmax[m]
Left
βmax[m]
Right
Q1
Q2
Q3
Q4
Q5
Q6
Q7
Q8
Q9
Q10
QT11
QT12
QT13
-200
200
-200
82
-67
59
-199
150
-164
184
57
-43
-40
-Q1.L
-Q2.L
-Q3.L
-Q4.L
-Q5.L
-58
199
-155
166
-193
-56
-55
-QT13.L
4537
9189
9333
9440
3322
1559
984
285
241
291
141
170
176
4545
9205
9350
9424
3327
1561
986
285
261
270
154
179
174
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Dipole first optics
Additional TAS absorber in the present layout – per N. Mokhov
IP
D1a
TAS2
D1b
TAN
Earlier layout
(PAC 03)
Present layout
D1 dipole
10m long
TAN absorber
After D1
β*
βmax
0.26 m
23 km
D1a 1.5m long,
D1b 8.5m long
TAS2, after D1a
TAN after D1b
0.25 m
27 km
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Dipoles First - Matching
Beams in separate focusing channels
Matching done from QT13(left) to QT13(right)
Lattice Version 6.2
Triplet quads Q1 – Q3 at fixed gradient = 200
T/m, exactly anti-symmetric
Positions and lengths of magnets Q4-QT13 kept
the same
Strengths of quads Q4 to Q9 < 200 T/m
Q10 on the left has 230 T/m. Could be changed
if positions and lengths of Q4-Q7 are changed.
Trim quad strengths QT11 to QT13 < 160T/m
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Dipole first – collision optics, triplets
 TAS1 absorber (1.8m) before D1a
 Dipole D1a starts 23 m from IP
 TAS2 absorber (1.5m) after D1a
 0.5m space between D1a-TAS2
and TAS2-D1b
 L(D1b) = 8.5m
 D1, D2 – each 10m long, ~14T
 5m long space after D2 for a
TAN absorber
 Q1 starts 55.5 m from the IP
 L(Q1) = L(Q3) = 4.99 m,
 L(Q2a) = L(Q2b) = 4.61m
Collision optics β*= 0.25m
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Gradients, beta max – dipoles first, triplets
Quad
B’[T/m]
Left
B’[T/m]
Right
βmax[m]
Left
βmax[m]
Right
Q1
Q2
Q3
Q4
Q5
Q6
Q7
Q8
Q9
Q10
QT11
QT12
QT13
-200
200
-200
78
-104
80
-146
107
-92
230
170
161
-158
-Q1.L
-Q2.L
-Q3.L
-112
137
-38
172
-196
31
-120
41
-156
-160
18478
26936
27135
8183
3441
2858
2185
953
1418
210
192
185
176
18619
27143
26926
8253
3845
932
3089
460
164
206
210
167
174
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Coil aperture
2(1.1*9*σ+8.6+
4.5+3) mm
93
106
106
73
60
56
57
46
49
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Dipoles first and doublet focusing
Features
• Requires beams to be in
separate focusing channels
Q1
• Fewer magnets
D2
• Beams are not round at the IP
Q2
IP
D1
D2
• Opposite polarity focusing at other
IR to equalize beam-beam tune shifts
Focusing symmetric about IP
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• Polarity of Q1 determined by
crossing plane – larger beam
size in the crossing plane to
increase overlap
• Significant changes to outer triplet
magnets in matching section.
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Doublet Optics – Beta functions
J. Johnstone
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Gradients, beta max – dipoles first, doublets
Quad
B’[T/m]
Left
B’[T/m]
Right
βmax[m]
Left
Q1
Q2
Q3
Q4
Q5
Q6
Q7
Q8
Q9
Q10
QT11
QT12
QT13
-200
200
46
-50
0
-155
-31
147
-204
186
-98
-27
92
Q1.L
Q2.L
Q3.L
-Q4.L
-Q5.L
-Q6.L
-Q7.L
-147
205
-198
78
-44
-108
24446
24446
4462
3908
1549
1354
443
388
267
199
185
168
176
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βmax[m]
Right
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24446
24446
4462
3909
1547
1367
512
356
257
209
190
170
173
Coil aperture
2(1.1*9*σ+8.6+
4.5+3) mm
102
102
62
60
50
49
42
41
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Features of this doublet optics
Symmetric about IP from Q1 to Q3, anti-symmetric from
Q4 onwards
Q1, Q2 are identical quads, Q1T is a trim quad (125
T/m). L(Q1) = L(Q2) = 6.6 m
Q3 to Q6 are at positions different from baseline optics
All gradients under 205 T/m
Phase advance preserved from injection to collision
At collision, β*x= 0.462m, β*y = 0.135m, β*eff= 0.25m
Same separation in units of beam size with a smaller
crossing angle ΦE = √(β*R/ β*E) ΦR = 0.74 ΦR
Luminosity gain compared to round beam
Including the hourglass factor,
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Chromaticity comparison
β* = 0.25m
Quads first
Complete
Q’x
-48
Insertion
Q’y
-48
Inner
Q’x
-44
Magnets
Q’y
-44
Dipoles first –
triplets
-99
-96
-82
-82
Dipoles first
- doublets
-105
-121
-103
-112
Including IR1 and IR5
Chromaticity of dipoles first with triplets is 99 units larger per plane than
quads first
Chromaticity of dipoles first with doublets is 31 units larger per plane than
dipoles first with triplets
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Chromaticity contributions
 Inner triplet and inner doublet dominate the chromaticity
 Anti-symmetric optics: upstream and downstream quads have opposite
chromaticities
 Symmetric optics: upstream and downstream quads have the same sign of
chromaticities
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Energy Deposition
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Energy Deposition Issues
Quench stability: Peak power density
Dynamic heat loads: Power dissipation and
cryogenic implications
Residual dose rates: hands on maintenance
Components lifetime: peak radiation dose and
lifetime limits for various materials
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Energy Deposition in Quads First
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
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A. Zlobin et al, EPAC 2002
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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
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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.
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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
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Energy deposition in open mid-plane dipole
TAS
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TAS2
TAN
Optimized dipole with TAS2
IP end of D1 is well protected by TAS.
Non-IP end of D1 needs protection.
Magnetized TAS is not useful.
Estimated field 20 T-m
Instead split D1 into D1A and D1B.
Spray from D1A is absorbed by
additional absorber TAS2
Results (N. Mokhov)
 Peak power density in SC coils
~0.4mW/g, well below the quench limit
 Dynamic heat load to D1 is drastically
reduced.
 Estimated lifetime based on
displacements per atom is ~10 years
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Magnets
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Gradient vs Bore size
Nb3Sn at 1.8K
Nb3Sn at 4.35K
Current
LHC
NbTi at 1.8K
NbTi at 4.35K
mm
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Magnet Program Goals
Provide options for future upgrades of the LHC Interaction Regions
Demonstrate by 2009 that Nb3Sn magnets are a viable choice for an LHC
IR upgrade (Developed in consultation with CERN and LAPAC)
Focus on major issues: consistency, bore/gradient (field) and length
1. Capability to deliver predictable, reproducible performance:
TQ (Technology Quads):
D = 90 mm, L = 1 m, Gnom > 200 T/m
2.1.Capability to scale-up the magnet length:
LQ (Long Quads) :
D = 90 mm, L = 4 m, Gnom > 200 T/m
3. Capability to reach high gradients in large apertures:
HQ (High Gradient Quads):
D = 90 mm, L = 1 m, Gnom > 250 T/m
Supporting R&D
o Sub-scale dipoles & quads with L=0.3 m, Bcoil = 11-12 T
issues relevant to the whole program (end-preload, training, quench
protection, alignment of support structures)
o Long coil fabrication and tests with L=4 m, Bcoil = 11-12 T
o Radiation hard insulation
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Short Quad Models: FY08-FY09
Goal: increase Quad gradient using 3-layer and/or 4-layer coils
Engineering design starts in FY06 and fabrication in FY07
3-layer: G=260-290 T/m
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4-layer: G=280-310 T/m
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Magnet R&D challenges
All designs put a premium on achieving very high
field:
Maximizes quadrupole aperture for a given gradient.
Separates the beams quickly in the dipole first IR
=> bring quads as close as possible to the IP.
Push Bop from 8 T -> 13~15 T in dipoles or at pole of quad
=> Nb3Sn.
All designs put a premium on large apertures:
Decreasing * increases max => quad aperture up to 110
mm?
Large beam offset at non-IP end of first dipole.
=> Dipole horizontal aperture >130 mm.
Energy deposition:
quench stability, cooling, radiation hard materials.
Nb3Sn is favored for maximum field and temperature
margin, but considerable R&D is required to master this
technology.
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Beam-beam phenomena
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RHIC Beam-beam experiment
Question: Do parasitic interactions in
RHIC have an impact on the beam ?
Experiment – April 2005
Change the vertical separation between
the beams at 1 parasitic interaction
Observe beam losses, lifetimes, tunes vs
separation
Beam Conditions
 1 bunch of protons in each ring
 Injection Energy 24,3 GeV
 Bunch intensities ~ 2 x 1011
1 parasitic interaction per bunch
Bunches separated by ~10σ at
opposite parasitic
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RHIC beam-beam experiment
W. Fischer et al (BNL)
Observations
 !st set of studies: tunes of blue
and yellow beam were asymmetric
about diagonal
 Blue beam losses increased as
separation decreased. No influence
on yellow beam.
 Next set of studies: tunes
symmetric about diagonal
 Onset of significant losses in both
beams for separations below 7σ
Orbit data – time stamp corresponds to
time of measurement, Not to time of orbit
change
Shift orbit data to the right
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There is something to compensate
 Phenomena is tune dependent
 Remote participation at FNAL
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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
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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, …
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Strong-strong beam-beam simulations
J. Qiang, LBL
Strong-strong simulations done with
PIC style code Beambeam3D (LBNL)
Emphasis on emittance growth due to
head-on interactions under different
situations
Beam offset at IP
Mismatched emittances and
intensities
Numerical noise is an issue – growth
rate depends on number of macroparticles M. Continuing studies to
extract asymptotic (in M) growth
rates.
Continuing additions to code:
crossing angles, long-range
interactions
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US-LARP: IR Upgrades
Nominal case
Beams offset by 0.15 sigma
Emittance growth 50% larger
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IR and Beam-beam tasks – FY06-07
IR design
Quad first – lowest feasible * consistent with gradients and
apertures, field quality
Dipoles first – Triplet: *, apertures, gradients, field quality
Dipoles first – Doublet: explore feasibility
Beam-beam compensation
Phase 2: Build wire compensator, machine studies in RHIC
and weak-strong simulations with BBSIM
Strong-strong beam-beam simulations: emittance growth with swept
beams (luminosity monitor), wire compensation, and halo
formation (Beambeam3D)
Energy Deposition
IR designs (quadrupole and dipole first), tertiary collimators, and the
forward detector regions (CMS, TOTEM, FP420 and ZDC).
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Issues
IR design issues
- What are the space constraints from Q4 to Q7?
- By how much can L* be reduced, if at all?
- Solutions need to be updated for Lattice Version 6.5. MAD8 version
of the lattice would be helpful.
Beam-beam experiment at RHIC
- How can the RHIC experiments be more useful to the LHC? Is a
pulsed wire necessary in the LHC?
Crab cavities
- How much space will be needed?
- Cornell has expertise and interest in designing these cavities
Energy Deposition
- Progress on quadrupole design which can absorb heat load at 10
times higher luminosity
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IR Workshop at FNAL
October 3-4. 2005 at FNAL
Topics
- IR designs for the upgrades
- Energy deposition, quench levels, TAN/TAS
integration
- Magnet designs for the IR magnets
- Beam-beam compensation: wires, e-lens
- Feasibility of large x-angles and crab cavities in
hadron colliders
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Backup Slides
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Doublet optics - dispersion
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Design Studies
A. Zlobin
–
IR Magnets
Magnetic design and analysis
Mechanical design and analysis
Thermal analysis
Quench protection analysis
Test data analysis
Integrate with AP and LARP magnet tasks
–
Cryogenics
IR cryogenics and heat transfer studies
Radiation heat deposition
Cryostat quench protection
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Model Magnet R&D
G.L. Sabbi
Main program focus (Technology Quadrupoles)
– 2-Layer quads, 90 mm aperture, G > 200 T/m ASAP
Considerations
– Design approach – end loading options, preload
– Fabrication techniques
– Structure options – TQS, TQC
Opportunity to arrive at best-of-the-best and increase
confidence in modeling
Convergence through working groups and internal reviews
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Technology Quads: Features and Goals
Objective: develop the technology base for LQ and HQ:
• evaluate conductor and cable performance: stability, stress limits
• develop and select coil fabrication procedures
• select the mechanical design concept and support structure
• demonstrate predictable and reproducible performance
Implementation: two series, same coil design, different structures:
• TQS models: shell-based structure
• TQC models: collar-based structure
Magnet parameters:
• 1 m length, 90 mm aperture, 11-13 T coil peak field
• Nominal gradient 200 T/m; maximum gradient 215-265 T/m
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FY08-09: Long Quads (LQ)
R&D issues:
• long cable fabrication and insulation
• stress control during coil reaction, cable treatment, pole design
• coil impregnation procedure, handling of reacted coils
• support structures, assembly issues
• reliability of design and fabrication
Plan: scale-up the TQ design to 4 meter length (LQ)
FY06: fundamental scale-up issues addressed by Supporting R&D:
• general infrastructure and tooling
• long racetrack coil fabrication and test
• scale-up and alignment issues for shell-based structure
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Block-type IRQ coils and mechanical structure
(FNAL)
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Larger-aperture separation dipole (LBNL)
Shell-type coil design
Block-type coil design
~200 mm horizontal aperture
Current Status: Several IR quad designs were
thick internal absorber
generated and compared with 90 mm shell-type
Bmax=15-16 T, good field quality quads including magnetic and mechanical
1.5-2 m iron OD
parameters.
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