11/18/2008 Global Design Effort 1 Summary for Gamma-Gamma Mayda M. Velasco Northwestern University...
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Transcript of 11/18/2008 Global Design Effort 1 Summary for Gamma-Gamma Mayda M. Velasco Northwestern University...
11/18/2008 Global Design Effort 1
Summary for Gamma-Gamma
Mayda M. VelascoNorthwestern University
November 20, 2008LCWS08 -- UIC, Chicago
11/18/2008 2Linear Collider Workshop – November 16-20, 2008
As pointed out in the past: Photon Linear Collider (PLC) is a simple &
elegant idea
• Laser Compton interaction produces beam of high energy photons– E <= 0.8 Ebeam
• Peak has high circular polarization– Linear polarization is also possible– CP studies
• The effective cross section for processes like gg-->h is high, compensating for the lower luminosity Lgg~0.2Le+e-
• Question: Is it cost effective to make low energy PLC, ff LHC find a “light” Higgs
11/18/2008 3Linear Collider Workshop – November 16-20, 2008
Basic Physics Case for a Low Energy & High Energy PLC already stablish
• Low Energy
• High Energy
11/18/2008 4Linear Collider Workshop – November 16-20, 2008
PLC: Issues & Facts discussed at joint session with XX group
• Polarization needed to obtain high luminosity @ E_gg ~0.8 E+_ee
– Damping rings needed due to high emittances of beam produced with DC photo-guns
– Hope... Future RF polarized sources
• Interactions of Laser with e-beam disruptive – Large crossing angle needed
• Detector the same as for e+e- for theta>7o
• At small angles masking is needed to protect the detector
• Beam dump: photon beam cannot be deflected therefore the energy density at the dump is large
– Request: proper simulation & design needed
11/18/2008 5Linear Collider Workshop – November 16-20, 2008
The photon collider needs a laser pulse for every electron bunch
• Average power ~15kW / beam
• Formatted in time to match the electron time structure
120 pulses separated by 2.8 ns
Col
d S
RF
War
m X
-ban
d,
S-b
and,
CLI
C
11/18/2008 6Linear Collider Workshop – November 16-20, 2008
• e-e- ???– significant price cut if positron sources not
needed?
– how different the IP issues will become?
11/18/2008 7Linear Collider Workshop – November 16-20, 2008
The MERCURY laser is an attempt to create high average power with good efficiency
Goal:• 100 J• 10 Hz • 10% Efficiency• 2-10 ns • < 5X Diffraction limit • > 108 shots
Output
Diode arrays• 8 diode arrays• 6624 diodes total• 730 kW peak power
Front-end• 300 mJ
Gas-cooledamplifier heads• Helium gas flow at 0.1 Mach
Cavity Laser:• 764 W average power• 119 kW peak power
11/18/2008 8Linear Collider Workshop – November 16-20, 2008
beam splitter optical delay line
polarizerwave plate
• 120 hz of 100 J macro-pulses from 12 MERCURY lasers
• 100 J laser macro-pulse converted to train of 1 J subpulses
Straw-man laser for NLC presented at Snowmass 2001
IR optics
Single pulse to pulse train “hall of mirrors”
MERCURY laser plant
11/18/2008 9Linear Collider Workshop – November 16-20, 2008
Diode arrays are mature and industrialized
Offline tile tests: 1.5 x 108 shots
Mercury diode arrays: 5 x 106 shots
11/18/2008 10Linear Collider Workshop – November 16-20, 2008
Helium flow cooling manages the heat load in the crystals
Corrector plates will remove the residual wavefront distortion once the final
configuration is in place
11/18/2008 11Linear Collider Workshop – November 16-20, 2008
Methodologies for growing the amplifier crystals are in place
The crystals can be economically grown and processed
11/18/2008 12Linear Collider Workshop – November 16-20, 2008
MERCURY technology has been under development since 2001
• Operation at 10 Hz with 55 Joule pulses for 8 hours
• 10 ns width pulses– Has the bandwidth to support
ps pulse but not demonstrated
• 5x diffraction limit wavefront quality– Final wavefront corrections not
done
• Large improvements in diode cost and crystal growth and processing
11/18/2008 13Linear Collider Workshop – November 16-20, 2008
Most laser power is unused - A recirculating cavity can reduce required laser power
• 5 Hz operation• 1000+2820
bunches / train• 40mJ / pulse
• 764 W average power
• 119 kW peak diode power
2004 Cold SRF technology chosen for ILCInter-bunch spacing allows possibility of recirculationStacking cavity design from MBI / DESY- Zeuthen
G. Klemz et al.
Laser requirements:
11/18/2008 14Linear Collider Workshop – November 16-20, 2008
A layout for integrating the laser cavity and detector and detector was proposed
MBI/DESY laser stacking cavity design: - 369 ns path length - factor 300 reduction in total laser power
Detector must be modified to
accommodate the laser and to remove the disrupted electron
beam
11/18/2008 15Linear Collider Workshop – November 16-20, 2008
Since then smaller recirculating cavities have been developed for Compton light sources
• Resonant cavities are being developed for:
– Polarized positron source
– Laser wire– Beam diagnostics– Medical and industrial
applications– Photon collider
e- beam tube
beamInteraction
pointe- beam
LAL - Orsay
KEK - Hiroshima
11/18/2008 16Linear Collider Workshop – November 16-20, 2008
It is time to develop a conceptual design for a photon collider laser
• Average power of ~500W
– Been done before
– But not with• ps pulse
• Good wavefront quality
• Time formatting
• In 2009 we will create a conceptual design for the laser system
– Identify any technology limitations
– Understand the R&D path to demonstrating a workable system