Transcript Thursday Summary of Working Group I Initial questions I: 4) Optics design issues: Question / Topic goal of presentation Potential speaker Raimondi-Seryi final focus layout summarize concept.

Thursday Summary of Working Group I
Initial questions I:
4) Optics design issues:
Question / Topic
goal of presentation
Potential speaker
Raimondi-Seryi final focus layout
summarize concept and layout requirements
Pantaleo Rimondi
options and efficiency for correcting field errors via local magnets
options and efficiency for beta-beat corrections in both beams
what is the required orbit corrector strength
quadrupole first layout and optics
what is the maximum acceptance for D' from the experiments
Daniela Macina
present existing layout and optics solutions
Jean-Pierre Koutchouk
highlight optics limits / challenges and strong points
options and efficiency for correcting field errors via local magnets
options and efficiency for beta-beat corrections in both beams
present questions still to be addressed
what is the required orbit corrector strength
option for a low gradient & low field quadrupole first layout
LHC LUMI 2005; 3.9.2005; Arcidosso
Oliver Bruning
Oliver Brüning
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Thursday Summary of Working Group I
Initial questions II:
4) Optics design issues:
Question / Topic
goal of presentation
b-measurement
accuracy of b-function measurments
Potential speaker
Joachim Keil
correction options
Crab cavities
what are acceptible noise levels in a crab cavity?
what are the required crab-cavity apertures and R12 matrix elements
between the cavity and the IP for the different IR layout options?
Riccardo de Maria &
Jean-Pierre Koutchouk
Related questions given to the WG by the Work Shop Organizers
chromatic effects and sensitivity to field errors
beta* vs peak beta function in the triplet magnets
beam-beam compensation and Crab cavities
LHC LUMI 2005; 3.9.2005; Arcidosso
Oliver Brüning
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Thursday Summary of Working Group I
main points from Pantaleo Raimondi’s presentation I:
-local chromaticity correction via dispersion inside the triplet
magnets and two pairs of sextupoles (one inside at the
location of dispersion and one with phase advance of p) can
correct chromaticity and geometric aberrations
 works well for linear collider final focus (cancellation up
to forth order)
 Frank Zimmermann showed that the concept can be
applied to circular collider
LHC LUMI 2005; 3.9.2005; Arcidosso
Oliver Brüning
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From ILC to LHC (1)
Much smaller chromaticity:
Wmax=L*/by*=4/0.0001=40000 for ILC
Wmax=L*/b*=50/0.025=2000 for LHC
Much larger emittance and sizes
300nm/3nm for ILC
4mm/4mm for LHC
Much larger D allowed at the Final Quads:
D=0.2m for ILC
D>2m for LHC (increase in the size at the Quads
negligible)
Much smaller energy acceptance
De=+-2% for ILC
De=+-0.1% for LHC
Very weak and long bends needed for ILC to reduce
blow-up from SR.
From ILC to LHC (2)
Much easier task overall
Much weaker sexupoles
Much smaller second order geometric
aberrations and spurious higher order residual
aberrations.
A possible strategy for LHC:
Look for a solution that can be implemented
(and removed) anytime simply rematching
betas and Ds and chromaticity by varying
quads and sexupoles (Safest approach)
Thursday Summary of Working Group I
main points from Riccardo de Marias’s presentation I:
-matched optics solution for dipole first layout for Beam1
and Beam2 with squeeze and tunability study:
 18 km b-max requires additional Q’ correction
 dispersion of 15 cm from D1/D2 arrangement for free
 could be increased for D’ = 0 at the IP
 dispersion changes sign left and right from IP
 SF: kissing scheme could allow equal signs of D
but vertical D is quite small
LHC LUMI 2005; 3.9.2005; Arcidosso
Oliver Brüning
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Thursday Summary of Working Group I
main points from Riccardo de Marias’s presentation II:
-optics study relies on Nb3Sn technology:
 10 m long dipole magnets with B = 15 T
 quadrupole magnets with 260 T/m and 80 mm
aperture  11 T coil field
 IR layout provides magnetic TAS for “free”
LHC LUMI 2005; 3.9.2005; Arcidosso
Oliver Brüning
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Thursday Summary of Working Group I
main points from Oliver Brüning’s presentation I:
-proposal of a low gradient solution that could be realized
with NbTi technology
 18 km b-max requires additional Q’ correction
 maximum gradient of 70 T/m allows more than 200mm
diameter with a peak coil field of 5.5 T
 Dispersion inside the triplet could be increased for
D’ = 0 at the IP
 Layout still requires an improved TAS absorber
LHC LUMI 2005; 3.9.2005; Arcidosso
Oliver Brüning
8
Options for a Quadrupole First Layout
Layout and optics derived from Combined function solution:
D1/D1  3.7 T
Q1  47T/m  d = 212mm
Q2  70T/m  d = 143mm
Q3  47T/m  d = 212mm
Q3b  6T/m
 aperture estimate
assumes a peak coil field
of 5 T!
 dispersion matched to 1.5m in ‘triplet’ for Q’ correction!
LHC LUMI 2005; 3.9.2005; Arcidosso
Oliver Brüning
9
Options for a Quadrupole First Layout
Layout and optics derived from Combined function solution:
D1/D1  3.7 T
Q1  47T/m  d = 212mm
Q2  70T/m  d = 143mm
Q3  47T/m  d = 212mm
Q3b  6T/m
 aperture estimate
assumes a peak coil field
of 5 T!
 dispersion matched to 1.5m in ‘triplet’ for Q’ correction!
LHC LUMI 2005; 3.9.2005; Arcidosso
Oliver Brüning
10
Thursday Summary of Working Group I
main points from Jean-Pierre Koutchouks’s presentation I:
-NbTi technology only adequate for L = 1034 cm-2 sec-1
-true luminosity upgrade requires Nb3Sn or equivalent
technology (b10 tolerance and chromatic aberrations)
 discussion showed that NbTi with low gradient might still
be an option if the geometric reduction factor can be
maximized
 lower L* is clearly advantageous
LHC LUMI 2005; 3.9.2005; Arcidosso
Oliver Brüning
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Thursday Summary of Working Group I
main points from Joachim Keil’s presentation I:
-b-beat in HERA-e and HERA-p of the order of 40% (peak)
 measurement via the closed orbit response matric
 measurement in HERA-e takes 2 to 4 hours
 rewriting the equations of the coefficients provides linear
system of equations that can be solved via SVD
 alternate fitting for b and f values for BPM and corrector
parameters with fixed values
 converges within less than 100 iterations to self consistent
solution
 method is limited by BPM and corrector scaling errors
LHC LUMI 2005; 3.9.2005; Arcidosso
Oliver Brüning
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Thursday Summary of Working Group I
Main summary I:
-two options for dealing with the increased heat load inside
the triplet magnets:
1) construct more robust triplet magnets that can tolerate
the increased peak heat load  new magnet technology
(will it be ready by 2011?)
2) reduce the peak heat load with an upgrade of the TAS
absorber (dipole first layout offers this for “free”)
LHC LUMI 2005; 3.9.2005; Arcidosso
Oliver Brüning
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Thursday Summary of Working Group I
Main summary II:
-two options for dealing with the increased heat load inside
the triplet magnets:
1) beam beam wire compensation
2) bunch shortening (RF power and IBS?)
3) CRAB cavities
4) D0 installation inside the detector
All proposals are independent of IR layout and should be
studied with high priority as they offer efficient L increase!
LHC LUMI 2005; 3.9.2005; Arcidosso
Oliver Brüning
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Thursday Summary of Working Group I
Main summary III:
-how confident are we that Nb3Sn will be a mature technology
by the time we want to build the triplet upgrade?
-is a peak coil field of 11T really realistic?
 proposal to follow at least two design approaches:
one based on NbTi technology (> 4th generation!)
on base on new magnet technology (1st generation design!)
LHC LUMI 2005; 3.9.2005; Arcidosso
Oliver Brüning
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Thursday Summary of Working Group I
Main summary IV:
-repository with optics solutions is very desirable!
(linked to HHH CARE WWW page?)  we should all use
the same input format (MADX)
-identified three layout options that should be studied in more
detail:
1) dipole first based on Nb3Sn technology with L* = 19m
2) quad first layout based on Nb3Sn technology L* = 19m
3) low gradient quad first layout based on NbTi technology
LHC LUMI 2005; 3.9.2005; Arcidosso
Oliver Brüning
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Thursday Summary of Working Group I
Main summary V:
-we desperately need to fix L* and required length for TAS
upgrade (inflation of solutions)!
 this point was already raised at HHH workshop in 2004!
 Tanaji promised an answer for the TAS after October
US-LARP workshop in Fermilab!
 Emmanuel will clarify the L* options with the LHC
integration team (we agreed to assume L* = 19m for now
as a reasonable estimate)
 the goal is to have an update of the 3 proposals by end 2005
LHC LUMI 2005; 3.9.2005; Arcidosso
Oliver Brüning
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