1. US-LARP Progress on IR Upgrades
Tanaji Sen
FNAL

2. 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

3. 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
Tanaji Sen
US-LARP: IR Upgrades

4. IR designs Quadrupoles first – extension of baseline
Dipoles first – triplet focusing
Dipoles first – doublet focusing
Tanaji Sen
US-LARP: IR Upgrades

5. Triplet first optics Lattice Vers. 6.2 Nominal β* = 0.5 J. Johnstone
β* = 0.25
J. Johnstone
Tanaji Sen
US-LARP: IR Upgrades

6. Gradients, beta max – quads first optics
B’[T/m]
Left
Right
βmax[m] Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9
Q10
QT11
QT12
QT13
-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
261
270
154
179
174
Tanaji Sen
US-LARP: IR Upgrades

7. Dipole first optics Earlier layout (PAC 03) Present layout D1 dipole
Additional TAS absorber in the present layout – per N. Mokhov IP
D1a
TAS2
D1b
TAN
Earlier layout
(PAC 03)
Present layout
D1 dipole
TAN absorber β*
βmax
10m long
After D1
0.26 m
23 km
D1a 1.5m long, D1b 8.5m long
TAS2, after D1a
TAN after D1b
0.25 m
27 km
Tanaji Sen
US-LARP: IR Upgrades

8. 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
Tanaji Sen
US-LARP: IR Upgrades

9. 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
Tanaji Sen
US-LARP: IR Upgrades

10. Gradients, beta max – dipoles first, triplets
Quad
B’[T/m]
Left
Right
βmax[m]
Coil aperture
2(1.1*9*σ ) mm Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9
Q10
QT11
QT12
QT13
-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
167
174 93
106 73 60 56 57 46 49
Tanaji Sen
US-LARP: IR Upgrades

11. Dipoles first and doublet focusing
Features
Requires beams to be in
separate focusing channels
Fewer magnets
Beams are not round at the IP
Polarity of Q1 determined by
crossing plane – larger beam
size in the crossing plane to
increase overlap
Opposite polarity focusing at other
IR to equalize beam-beam tune shifts
Significant changes to outer triplet
magnets in matching section. Q1 D2 Q2 IP D1 D2
Focusing symmetric about IP
Tanaji Sen
US-LARP: IR Upgrades

12. Doublet Optics – Beta functions
J. Johnstone
Tanaji Sen
US-LARP: IR Upgrades

13. Gradients, beta max – dipoles first, doublets
Quad
B’[T/m]
Left
Right
βmax[m]
Coil aperture
2(1.1*9*σ ) mm Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9
Q10
QT11
QT12
QT13
-200
200 46
-50
-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
4462
3908
1549
1354
443
388
267
199
185
168
176
3909
1547
1367
512
356
257
209
190
170
173
102 62 60 50 49 42 41
Tanaji Sen
US-LARP: IR Upgrades

14. 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,
Tanaji Sen
US-LARP: IR Upgrades

15. Chromaticity comparison
Complete
Q’x
Insertion
Q’y
Inner
Magnets
Quads first
Dipoles first – triplets
Dipoles first
- doublets
-48
-99
-105
-96
-121
-44
-82
-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
Tanaji Sen
US-LARP: IR Upgrades

16. 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
Tanaji Sen
US-LARP: IR Upgrades

17. Energy Deposition
Tanaji Sen
US-LARP: IR Upgrades

18. 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
Tanaji Sen
US-LARP: IR Upgrades

19. 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
A. Zlobin et al, EPAC 2002
Tanaji Sen
US-LARP: IR Upgrades

20. 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
Tanaji Sen
US-LARP: IR Upgrades

21. 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
Tanaji Sen
US-LARP: IR Upgrades

22. Energy deposition in open mid-plane dipole
TAS
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
Tanaji Sen
US-LARP: IR Upgrades

23. Magnets
Tanaji Sen
US-LARP: IR Upgrades

24. Gradient vs Bore size Nb3Sn at 1.8K Nb3Sn at 4.35K Current LHC
NbTi at 1.8K
NbTi at 4.35K mm
Tanaji Sen
US-LARP: IR Upgrades

25. 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. 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 1.
Supporting R&D
Sub-scale dipoles & quads with L=0.3 m, Bcoil = T
issues relevant to the whole program (end-preload, training, quench protection, alignment of support structures)
Long coil fabrication and tests with L=4 m, Bcoil = T
Radiation hard insulation
Tanaji Sen
US-LARP: IR Upgrades

26. 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= T/m
4-layer: G= T/m
Tanaji Sen
US-LARP: IR Upgrades

27. 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.
Tanaji Sen
US-LARP: IR Upgrades

28. Beam-beam phenomena
Tanaji Sen
US-LARP: IR Upgrades

29. 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
Tanaji Sen
US-LARP: IR Upgrades

30. 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
There is something to compensate
Phenomena is tune dependent
Remote participation at FNAL
Orbit data – time stamp corresponds to time of measurement, Not to time of orbit
change
Shift orbit data to the right
Tanaji Sen
US-LARP: IR Upgrades

31. RHIC – Wire compensator
New LARP Task for FY06
RHIC provides unique environment
to study experimentally long-range
beam-beam effects akin to LHC
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 location of wire
IP6
Parasitic interaction
Phase advance from parasitic to wire = 6o
Tanaji Sen
US-LARP: IR Upgrades

32. 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 macro-particles M. Continuing studies to extract asymptotic (in M) growth rates.
Continuing additions to code: crossing angles, long-range interactions
Nominal case
Beams offset by 0.15 sigma
Emittance growth 50% larger
Tanaji Sen
US-LARP: IR Upgrades

33. 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).
Tanaji Sen
US-LARP: IR Upgrades

34. 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
Tanaji Sen
US-LARP: IR Upgrades

35. 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
Tanaji Sen
US-LARP: IR Upgrades

36. Backup Slides
Tanaji Sen
US-LARP: IR Upgrades

37. Doublet optics - dispersion
Tanaji Sen
US-LARP: IR Upgrades

38. 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
Tanaji Sen
US-LARP: IR Upgrades

39. 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
Tanaji Sen
US-LARP: IR Upgrades

40. 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, T coil peak field
Nominal gradient 200 T/m; maximum gradient T/m
Tanaji Sen
US-LARP: IR Upgrades

41. 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
Tanaji Sen
US-LARP: IR Upgrades

42. Block-type IRQ coils and mechanical structure (FNAL)
Tanaji Sen
US-LARP: IR Upgrades

43. Larger-aperture separation dipole (LBNL)
Shell-type coil design
Block-type coil design
~200 mm horizontal aperture
thick internal absorber
Bmax=15-16 T, good field quality
1.5-2 m iron OD
Current Status: Several IR quad designs were
generated and compared with 90 mm shell-type
quads including magnetic and mechanical
parameters.
Tanaji Sen
US-LARP: IR Upgrades