Transcript HADRON COLLIDERS Outline  The Tevatron o What are the issues? o What is the plan for the immediate future?  The LHC and its.

HADRON COLLIDERS
Outline
 The Tevatron
o What are the issues?
o What is the plan for the immediate future?
 The LHC and its upgrades
o What upgrades are possible?
o When do we start, and what is happening now?
 What are the steps beyond that?
o What are the possibilities for hadron colliders at higher energy?
o How do they compare in utility and cost?
 Is there a sensible plan for HEP that includes hadron
colliders?
o How can we improve the planning process?
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HADRON COLLIDERS
Motivation
 Hadron colliders are the discovery machines of high-
energy physics.
o Tevatron
o LHC & LHC Upgrades
o VLHC
 These colliders have much in common, but the
ultimate performance of each is determined by
different phenomena.
o Tevatron: Ability to produce, cool and deliver anti-protons
o VLHC: Synchrotron radiation & IR debris power
o LHC: In between - synch. rad., beam-beam interaction, ?
 Careful analysis of these differences will help us
construct the right plan.
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HADRON COLLIDERS
Tevatron
Performance
 Run II has not yet reached its expected luminosity performance
o The luminosity is determined by proton & antiproton intensities at
collision
 there are indications of beam-beam limitations
– Lifetimes and emittance growth in presence of other beam
o The efficiency for delivering both proton and pbar beams to collision
is not yet reliable
 There is now a plan to fix some of those problems.
o Improved instrumentation to help understand the issues
o Improved “housekeeping” to make operation of the whole complex
more robust
o Improved antiproton production and cooling
o Improved transfer efficiencies and reduced emittance blowup
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HADRON COLLIDERS
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Tevatron
Run II Peak Luminosity
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HADRON COLLIDERS
Tevatron
Luminosity vs. Pbars at Low Beta
Runs 631-2375
50
30
Luminosity (x10 )
40
30
20
10
0
0
200
400
600
800
1000
1200
1400
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Pbars at Low Be ta (x10)
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HADRON COLLIDERS
Tevatron
Pbar Efficiency, Stack to Low Beta
50
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Luminosity (x10 )
40
30
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10
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400
600
800
1000
1200
1400
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Pbars at Low Be ta (x10)
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HADRON COLLIDERS
Tevatron
What’s the Plan to Do Better?
 The Run II Luminosity Upgrade plan concentrates first on things that
will improve efficiency
http://www.fnal.gov/pub/now/upgradeplan/
o Beam position monitor and other instrumentation upgrades
o Dampers in MI
o Re-alignment of Tevatron and Pbar source
o Reduce MI cycle time for Pbar production
 Completed in 2004
o Slip stacking of protons in MI and pbar target sweeping
o Initial pbar acceptance improvements and Debuncher cooling upgrade
 Completed in 2005
o Recycler Ring with electron cooling integrated into operation
o Rapid transfer of pbars from Accumulator to Recycler
o Accumulator stacktail cooling upgrade
 Completed in 2007
o Pbar production acceptance upgrade with higher-gradient lithium lens
o Increased helical beam separation
o Introduction of active beam-beam compensation
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HADRON COLLIDERS
Tevatron
Projected Integrated Luminosity
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HADRON COLLIDERS
LHC
Luminosity Upgrade - Why & When
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HADRON COLLIDERS
LHC Luminosity Upgrade
Work has started
 HEPAP put R&D for a luminosity upgrade in its highest priority
category:
o
“The science of extending exploration of the energy frontier with the
LHC accelerator and detector luminosity upgrades is absolutely central.
The R&D phase for these will need to start soon if the upgrades are to
be finished by the present target date of 2014.”
 From the High-Energy Physics Facilities of the DOE Office of Science Twenty-Year Road
Map, HEPAP report to the Director of the Office of Science, 17 March 2003.
 Technical work has begun in the U.S. within the LHC Accelerator
Research Program (LARP) collaboration of DOE national labs - BNL,
Fermilab & LBNL
o Received a favorable recommendation from a DOE review in June, 2003
o Working on projects to help bring on the LHC quickly and efficiently
 Participate strongly in commissioning and in some instrumentation
o Working on magnet R&D and accelerator design to provide fully
integrated interaction regions suitable for ultra-high-luminosity operation
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HADRON COLLIDERS
LHC Luminosity Upgrade
Some Possible Upgraded LHC IRs
Quads 1st
Quads between
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Dipoles 1st
Twin Dipole 1st
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HADRON COLLIDERS
LHC Energy Upgrade
 What about an LHC energy upgrade?
o Whereas a luminosity upgrade is relatively cheap, quick and nondisruptive, an energy upgrade is not an upgrade — it is an entirely new
collider — and, it will probably need a new injector, too
o The best performance from Nb3Sn magnets will result in only a 70%
increase in energy
o The R&D to develop robust and cost-effective magnets at the highest
field will take a long time and be very costly.
o It will be expensive and risky for little return
 A staged VLHC is a better path.
o Higher energy per $ or €, even in its initial stage
o Upgradeable to > 200 TeV (cm)
 The freedom to make tradeoffs between tunnels and technical
components is a powerful tool to reduce cost and improve
performance.
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HADRON COLLIDERS
Fermilab-TM-2149
June 11, 2001
www.vlhc.org
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HADRON COLLIDERS
VLHC
Conclusions (1)
 A staged VLHC starting with 40 TeV and upgrading to 200 TeV
in the same tunnel is, technically, completely feasible.
 There are no serious technical obstacles to the Stage-1 VLHC
at 40 TeV and 1034 luminosity.
o The existing Fermilab accelerator complex is an adequate
injector for the Stage-1 VLHC, but lower emittance would be
better. (We should take this into account if Fermilab builds a
high-power injector)
o VLHC operating cost is moderate, using only 20 MW of
refrigeration power, comparable to the Tevatron.
o Improvements and cost savings can be gained through a
vigorous R&D program in magnets and underground
construction.
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HADRON COLLIDERS
VLHC
Conclusions (2)
 The construction cost of the first stage of a VLHC is
comparable to that of a linear electron collider,
~ $4 billion using “European” accounting.
o From this and previous studies, we note that the cost of a collider
of energy near 40 TeV is almost independent of magnetic field.
o A total construction time of 10 years for Stage-1 is feasible, but the
logistics will be complex.
o Making a large-circumference tunnel is possible. A number of
different possibilities in the Fermilab area were studied.
 Managing such a large construction project will be a challenge.
 The political issues associated with a large tunnel must be
handled with care.
o Building the VLHC at an existing hadron accelerator lab saves
significant money and time.
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HADRON COLLIDERS
The Staged VLHC Concept
 The Vision
o Build a BIG-circumference tunnel.
o Fill it with a “cheap” 40 TeV collider.
o Later, upgrade to a 200 TeV collider in the same
tunnel.
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Spreads the cost
Produces exciting energy-frontier physics sooner & cheaper
Allows time to develop cost-reducing technologies for Stage 2
Creates a high-energy full-circumference injector for Stage 2
A large-circumference tunnel is necessary for a synchrotron
radiation-dominated collider.
 This is a time-tested formula for success
Main Ring  Tevatron
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HADRON COLLIDERS
VLHC Parameters
Stage 1
Stage 2
Total Circumference (km)
233
233
Center-of-Mass Energy (TeV)
40
200
Number of interaction regions
2
2
1 x 1034
2.0 x 1034
2
11.2
35.0
35.0
2.6 x 1010
5.4 x 109
Bunch Spacing (ns)
18.8
18.8
b* at collision (m)
0.3
0.5
Free space in the interaction region (m)
± 20
± 30
Interactions per bunch crossing at L peak
21
55
Debris power per IR (kW)
6
94
Synchrotron radiation power (W/m/beam)
0.03
5.7
Average power use (MW) for collider ring
25
100
Peak luminosity (cm-2s-1)
Dipole field at collision energy (T)
Average arc bend radius (km)
Initial Number of Protons per Bunch
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VLHC Tunnel Cross Section
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HADRON COLLIDERS
VLHC
Synchrotron radiation
 Synchrotron radiation masks look promising. They decrease
refrigerator power and permit higher energy and luminosity.
They are practical only in a large-circumference tunnel.
GAP
SLOT
Coolant
PHOTON-STOP
BEAM SCREEN
A “standard” beam screen will work up
to 200 TeV and 2x1034. Beyond that, the
coolant channels take too much space.
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A synchrotron radiation “mask” will allow
even higher energy and luminosity.
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HADRON COLLIDERS
VLHC
Optimum Field
PSR<10 W/m/beam peak
tL > 2 tsr
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VLHC
HADRON COLLIDERS
Total collider cost
based on SSC cost distribution
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HADRON COLLIDERS
Stage-2 VLHC Conclusions
 The Stage 2 VLHC can reach 200 TeV and 2x1034 or more in the 233 km
tunnel.
 A large-circumference ring is a great advantage for the high-energy
Stage-2 collider. A small-circumference high-energy VLHC may not be
realistic.
o The optimum magnetic field for a 100-200 TeV collider is less
than the highest field strength attainable because of synchrotron
radiation, total collider cost and technical risk.
10 T < B < 12 T appears optimum for 100 TeV < Ecm < 200 TeV
 The minimum aperture of the magnet is determined by beam stability
and synchrotron radiation, not by field quality.
 There is the need for magnet and vacuum R&D to demonstrate
feasibility and to reduce cost.
o This R&D will not be easy, will not be quick, and will not be cheap.
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HADRON COLLIDERS
VLHC Next Steps
There will be a VLHC Physics Workshop this
year.
o Date: October 16 - 18, 2003 at Fermilab
o Organizers:
 Uli Baur
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
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
SUNY-Buffalo
Contact: [email protected]
Chip Brock
Michigan State University
Chris Hill
Fermilab
Gian Giudice CERN
Paris Sphicas CERN
http://conferences.fnal.gov/hadroncollider/
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HADRON COLLIDERS
The HEP Plan
 We are on the verge of important discoveries
o There are many hints that great physics is just over the horizon —
understanding EWSB, neutrino mass, dark energy, dark matter and
more.
o An exciting time.
 The possibilities for new HEP tools are excellent
o Run II is progressing (with some difficulty)
o LHC is being built (with the usual problems)
o A renaissance in neutrino physics (New stuff)
o A linear collider is being considered (and might start in 5 to 10
years)
 Should we include a VLHC in this plan?
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HADRON COLLIDERS
VLHC in the HEP Plan
 Why do we need to include the VLHC in the HEP plan?
o If we believe that we may eventually want higher-energy collisions at
high luminosity, we will almost certainly need a VLHC.
 The timing and eventual existence of a VLHC will depend on
decisions about all other multi-billion-dollar facilities including
a linear collider.
o If a linear collider is built in the U.S. for billions of $, the U.S. is unlikely
to spend billions on a VLHC until many years later.
o The U.S. has the best combination of resources, infrastructure, space
and geology for a VLHC. It is difficult to builda VLHCt anywhere else.
o A significant energy upgrade of the LHC will be very costly and very
risky, for very little gain.
o Result: A long delay to higher energy
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HADRON COLLIDERS
The HEP Planning Process
 We need to reexamine our strategy for progress, planning and politics,
not only for the VLHC, but for all large facilities.
 Big HEP instruments require more than business as usual
o We need a global strategy derived from a large vision of scientific goals
— the “Science Roadmap.”
Sell the science, not the instruments.
o Think of the facilities as missions along the way to the science goals.
o We need a fair and open mechanism to modify the roadmap and the
plan as results dictate.
o We will be competing with other large science facilities, or even nonscientific projects for government support.
o We must include a range of scientific disciplines and high-level
government policy makers from the beginning of planning.
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HADRON COLLIDERS
A Global HEP Strategy
 Why do we need a global strategy?
o Big HEP instruments are too costly to be planned, built and
operated nationally or regionally.
o HEP instruments are complex and take a long time to design and
build. Everyone must be involved; everyone must help.
o International collaboration has many political, human and scientific
benefits beyond cost-sharing.
 While we’re planning, important instruments are missing from the
existing plans.
o What about underground labs, super neutrino beams, astrophysics
experiments or R&D for the future? All these should be in the plan,
and all should be part of a Global Strategy.
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HADRON COLLIDERS
A Word About R&D
 The machines and facilities we are talking about are
costly and complex.
o Mistakes and delays are potentially very damaging financially,
politically and scientifically.
o Political and financial recovery is difficult and time-consuming.
o It takes longer than you think to develop the components of a
cutting-edge collider.
 The R&D investment for future HEP instruments will
be much greater than we are accustomed to.
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HADRON COLLIDERS
Conclusions
 The most important requirement for the survival of HEP is
worldwide cooperation resulting in a global strategy based on a
visionary science roadmap.
o Sell the science, not the instruments
o The goals should be truly large and visionary, and the instruments
missions along the way.
 The parameters and schedule for a VLHC will depend on the
timing and location of all other large facilities. The global plan
should recognize these couplings.
 If we ever want to build a VLHC, or any other large facility, we
need to have a vigorous R&D program now.
o The technology is very challenging, and the penalty for failure
will be severe.
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HADRON COLLIDERS
Last Slide
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