Personal Perspectives on the ITRP Recommendation and on the Next Steps Toward the International...
-
date post
20-Dec-2015 -
Category
Documents
-
view
224 -
download
1
Transcript of Personal Perspectives on the ITRP Recommendation and on the Next Steps Toward the International...
Personal Perspectives on the ITRP Recommendation and on the Next
Steps Toward the International Linear Collider
Barry BarishPAC Annual MeetingKnoxville, Tennessee
16-May-05
16-May-05 PAC 05 - Barish 2
Why e+e- Collisions?
• elementary particles
• well-defined
– energy,
– angular momentum
• uses full COM energy
• produces particles democratically
• can mostly fully reconstruct events
16-May-05 PAC 05 - Barish 5
Why a TeV Scale?
• Two parallel developments over the past few years (the science & the technology)
– The precision information e+e- and data at present energies have pointed to a low mass Higgs; Understanding electroweak symmetry breaking, whether supersymmetry or an alternative, will require precision measurements.
– There are strong arguments for the complementarity between a ~0.5-1.0 TeV ILC and the LHC science.
16-May-05 PAC 05 - Barish 6
Electroweak Precision Measurements
e+e+ and neutrino scattering results at present energies strongly point to a low mass Higgs and an energy scale for new physics < 1TeV
0
2
4
6
10020 400
mH GeV
Excluded Preliminary
had =(5)
0.027610.00036
0.027470.00012
Without NuTeV
theory uncertainty
Winter 2003
16-May-05 PAC 05 - Barish 7
Why a TeV Scale e+e- Accelerator?
• Two parallel developments over the past few years (the science & the technology)
– The precision information from LEP and other data have pointed to a low mass Higgs; Understanding electroweak symmetry breaking, whether supersymmetry or an alternative, will require precision measurements.
– There are strong arguments for the complementarity between a ~0.5-1.0 TeV LC and the LHC science.
16-May-05 PAC 05 - Barish 8
Linear Collider Spin Measurement
LHC should discover the Higgs
The linear collider should measure its spin
LHC/ILC Complementarity
The process e+e– HZ can be used to measure the spin of a 120 GeV Higgs particle.
The Higgs must be spin zero
16-May-05 PAC 05 - Barish 9
Extra Dimensions
Linear collider
LHC/ILC Complementarity
Map extra dimensions: study the emission of gravitons into the extra dimensions, together with a photon or jets emitted into the normal dimensions.
16-May-05 PAC 05 - Barish 10
Why a TeV Scale e+e- Accelerator?
• Two parallel developments over the past few years (the science & the technology)
– Designs and technology demonstrations have matured on two technical approaches for an e+e- collider that are well matched to our present understanding of the physics.
16-May-05 PAC 05 - Barish 11
GLC GLC/NLC Concept
• The main linacs operate at an unloaded gradient of 65 MV/m, beam-loaded to 50 MV/m.
• The rf systems for 500 GeV c.m. consist of 4064 75 MW Periodic Permanent Magnet (PPM) klystrons arranged in groups of 8, followed by 2032 SLED-II rf pulse compression systems
16-May-05 PAC 05 - Barish 12
TESLA Concept
• The main linacs based on 1.3 GHz superconducting technology operating at 2 K.
• The cryoplant, is of a size comparable to that of the LHC, consisting of seven subsystems strung along the machines every 5 km.
16-May-05 PAC 05 - Barish 13
Which Technology to Chose?
– Two alternate designs -- “warm” and “cold” had come to the stage where the show stoppers had been eliminated and the concepts were well understood.
– A major step toward a new international machine required uniting behind one technology, and then working toward a unified global design based on the recommended technology.
16-May-05 PAC 05 - Barish 14
ICFA/ILCSC Evaluation of the Technologies
The Report Validates the Readiness of L-band and X-
band Concepts
BUT, IT DID NOT MAKE A CHOICE
16-May-05 PAC 05 - Barish 16
The Charge to the International Technology Recommendation Panel
General Considerations The International Technology Recommendation Panel (the Panel) should recommend a Linear Collider (LC) technology to the International Linear Collider Steering Committee (ILCSC).
On the assumption that a linear collider construction commences before 2010 and given the assessment by the ITRC that both TESLA and JLC-X/NLC have rather mature conceptual designs, the choice should be between these two designs. If necessary, a solution incorporating C-band technology should be evaluated.
Note -- We interpreted our charge as being to recommend a technology, rather than choose a design
16-May-05 PAC 05 - Barish 17
ITRP Schedule of Events • Six Meetings
– RAL (Jan 27,28 2004)
– DESY (April 5,6 2004)
– SLAC (April 26,27 2004)
– KEK (May 25,26 2004)
– Caltech (June 28,29,30 2004)
– Korea (August 11,12,13)
– ILCSC / ICFA (Aug 19)– ILCSC (Sept 20)
Tutorial & Planning
Site Visits
Deliberations
Exec. Summary Final Report
Recommendation
16-May-05 PAC 05 - Barish 18
Evaluate a Criteria Matrix
• The panel analyzed the technology choice through studying a matrix having six general categories with specific items under each:– the scope and parameters specified by the ILCSC; – technical issues; – cost issues; – schedule issues; – physics operation issues; – and more general considerations that reflect the
impact of the LC on science, technology and society
16-May-05 PAC 05 - Barish 19
The Recommendation
• We recommend that the linear collider be based on superconducting rf technology
– This recommendation is made with the understanding that we are recommending a technology, not a design. We expect the final design to be developed by a team drawn from the combined warm and cold linear collider communities, taking full advantage of the experience and expertise of both (from the Executive Summary).
– The superconducting technology has several very nice features for application to a linear collider. They follow in part from the low rf frequency.
16-May-05 PAC 05 - Barish 20
Some Features of SC Technology
• The large cavity aperture and long bunch interval reduce the complexity of operations, reduce the sensitivity to ground motion, permit inter-bunch feedback and may enable increased beam current.
• The main linac rf systems, the single largest technical cost elements, are of comparatively lower risk.
• The construction of the superconducting XFEL free electron laser will provide prototypes and test many aspects of the linac.
• The industrialization of most major components of the linac is underway.
• The use of superconducting cavities significantly reduces power consumption.
16-May-05 PAC 05 - Barish 21
The Technology Recommendation
• The recommendation was presented to ILCSC & ICFA on August 19 in a joint meeting in Beijing.
• ICFA unanimously endorsed the ITRP’s recommendation on August 20
The Global Design Effort
Formal organization begun at LCWS 05 at Stanfordin March 2005 when I became director of the GDE
16-May-05 PAC 05 - Barish 25
GDE – Near Term Plan
• Staff the GDE– Administrative, Communications, Web staff– Regional Directors (each region)– Engineering/Costing Engineer (each region)– Civil Engineer (each region)– Key Experts for the GDE design staff from the world
community (please give input)– Fill in missing skills (later)
Total staff size about 20 FTE (2005-2006)
16-May-05 PAC 05 - Barish 26
GDE – Near Term Plan
• Schedule• Begin to define Configuration (Aug 05) • Baseline Configuration Document by end of 2005-----------------------------------------------------------------------• Put Baseline under Configuration Control (Jan
06) • Develop Conceptual Design Report by end of
2006
• Three volumes -- 1) Conceptual Design Report; 2) Shorter glossy version for non-experts and policy makers ; 3) Detector Concept Report
16-May-05 PAC 05 - Barish 27
GDE – Near Term Plan
• Organize the ILC effort globally– First Step --- Appoint Regional Directors within the
GDE who will serve as single points of contact for each region to coordinate the program in that region.
– Make Website, coordinate meetings, collaborative R&D, etc
• R&D Program– Coordinate worldwide R & D efforts, in order to
demonstrate and improve the performance, reduce the costs, attain the required reliability, etc. (Proposal Driven to GDE)
16-May-05 PAC 05 - Barish 28
main linacbunchcompressor
dampingring
source
pre-accelerator
collimation
final focus
IP
extraction& dump
KeV
few GeV
few GeVfew GeV
250-500 GeV
Starting Point for the GDE
Superconducting RF Main Linac
16-May-05 PAC 05 - Barish 29
Parameters for the ILC
• Ecm adjustable from 200 – 500 GeV
• Luminosity ∫Ldt = 500 fb-1 in 4 years
• Ability to scan between 200 and 500 GeV
• Energy stability and precision below 0.1%
• Electron polarization of at least 80%
• The machine must be upgradeable to 1 TeV
16-May-05 PAC 05 - Barish 30
Experimental Test Facility - KEK
• Prototype Damping Ring for X-band Linear Collider
• Development of Beam Instrumentation and Control
16-May-05 PAC 05 - Barish 32
TESLA Test Facility Linac - DESY
laser driven electron gun
photon beam diagnostics
undulatorbunch
compressor
superconducting accelerator modules
pre-accelerator
e- beam diagnostics
e- beam diagnostics
240 MeV 120 MeV 16 MeV 4 MeV
16-May-05 PAC 05 - Barish 34
rf bands:
L-band (TESLA) 1.3 GHz = 3.7 cm
S-band (SLAC linac) 2.856 GHz 1.7 cm
C-band (JLC-C) 5.7 GHz 0.95 cm
X-band (NLC/GLC) 11.4 GHz 0.42 cm
(CLIC) 25-30 GHz 0.2 cm
Accelerating structure size is dictated by wavelength of the rf accelerating wave. Wakefields related to structure size; thus so is the difficulty in controlling emittance growth and final luminosity.
Bunch spacing, train length related to rf frequency
Damping ring design depends on bunch length, hence frequency
Specific Machine Realizations
Frequency dictates many of the design issues for LC
16-May-05 PAC 05 - Barish 35
Cost Breakdown by Subsystem
cf31%
structures18%rf
12%
systems_eng8%
installation&test7%
magnets6%
vacuum4%
controls4%
cryo4%
operations4%
instrumentation2%
Civil
SCRF Linac
16-May-05 PAC 05 - Barish 36
RF SC Linac ChallengesEnergy: 500 GeV, upgradeable to 1000 GeV
• RF Accelerating Structures– Accelerating structures must support the desired gradient in an
operational setting and there must be a cost effective means of fabrication.
– ~17,000 accelerating cavities/500 GeV
– Current performance goal is 35 MV/m, (operating at 30 MV/m)
• Trade-off cost and technical risk.
1 mRisk
Cos
t
~T
heor
etic
al M
ax
16-May-05 PAC 05 - Barish 37
(Improve surface quality -- pioneering work done at KEK)
BCP EP
• Several single cell cavities at g > 40 MV/m
• 4 nine-cell cavities at ~35 MV/m, one at 40 MV/m
• Theoretical Limit 50 MV/m
Electro-polishing
16-May-05 PAC 05 - Barish 38
Gradient
Results from KEK-DESY collaboration
must reduce spread (need more statistics)
single
-cell
measu
rem
ents
(in
nin
e-c
ell
cavit
ies)
16-May-05 PAC 05 - Barish 39
New Cavity Shape for Higher Gradient?
TESLA Cavity
• A new cavity shape with a small Hp/Eacc ratio around35Oe/(MV/m) must be designed. - Hp is a surface peak magnetic field and Eacc is the electric field gradient on the beam axis.
- For such a low field ratio, the volume occupied by magnetic field in the cell must be increased and the magnetic density must be reduced.
- This generally means a smaller bore radius. - There are trade-offs (eg. Electropolishing, weak cell-to-cell
coupling, etc)
Alternate Shapes
16-May-05 PAC 05 - Barish 40
Parameters of Positron Sources
rep rate# of bunches per pulse
# of positrons per bunch
# of positrons per pulse
TESLA TDR 5 Hz 2820 2 · 1010 5.6 · 1013
NLC 120 Hz 192 0.75 · 1010 1.4 · 1012
SLC 120 Hz 1 5 · 1010 5 · 1010
DESY positron source
50 Hz 1 1.5 · 109 1.5 · 109
16-May-05 PAC 05 - Barish 41
Positron Source
• Large amount of charge to produce
• Three concepts:– undulator-based (TESLA TDR baseline)
– ‘conventional’ – laser Compton based
16-May-05 PAC 05 - Barish 46
Remarkable progress in the past two years toward realizing an international linear collider:
important R&D on accelerator systems
definition of parameters for physics
choice of technology
start the global design effort
funding agencies are engaged
Many major hurdles remain before the ILC becomes a reality (funding, site, international organization, detailed design, …), but there is increasing momentum toward the ultimate goal --- An International Linear Collider.
Conclusions