Transcript Working Assumptions for Low Energy Operations Jim Clarke ASTeC & Cockcroft Institute Daresbury Laboratory 29/10/09 Positron Workshop.

Working Assumptions for
Low Energy Operations
Jim Clarke
ASTeC & Cockcroft Institute
Daresbury Laboratory
29/10/09
Positron Workshop
1
Background
• For SB2009 the undulator is moved to the
end of the linac
• The ILC still needs to operate over a wide
energy range
• The yield of positrons is not constant with
electron energy
• We need a specification for the yield so that
we can design the source appropriately
• I asked for guidance on this at ALCPG09
• This talk will discuss the provisional guidance
I have received …
29/10/09
Positron Workshop
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Provisional Guidance (from PMs)
•
•
•
The nominal scheme is used for operation until the beam energy is reduced below
the point where the undulator source effective positron yield is below 0.5.
For operation below that point, the ILC will use an alternating pulse scheme
(2.5Hz).
PMs Suggest:
– Pulsed steering magnets are used to correct the launch into the undulator so that
there is no natural difference between the high energy (e+ production) and low
energy (collision) beam trajectory due to the upstream linac curvature. Of course,
the undulator itself is aligned along a laser straight line pointing at the target. The
pulsed magnets will have a 2.5 Hz periodic excitation waveform.
– Pulsed trajectory correction magnets may be needed within the undulator.
– Pulsed dipole magnets are used to extract the charged beams between the
downstream end of the undulator and the target. There are obvious MPS and
magnet/power supply design issues with this sub-system, but it should be
feasible. The high energy beam (e+ production beam) should be dumped in the
full power BDS tune-up dump.
29/10/09
Positron Workshop
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SB2009 Layout
• Electron beam layout
e- side starting from main Linac exit
Fast abort line
Photon target +
remote handling
Undulator
Dogleg
Sacrificial
collimators +
chicane to detect
off energy beams
Interaction Point
400m
29/10/09
Deepa Angal-Kalinin/James Jones
DC Tuning line
Positron Workshop
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SB2009 Changes
• Low energy electrons transported to IP via
undulator and full BDS
Fast abort line, for
which beam?
Both?
e- side starting from main Linac exit
Photon target +
remote handling
Dogleg
Interaction Point
Pulsed magnets
here to
compensate
trajectory errors
29/10/09
Undulator, also
with pulsed
steering
magnets?
High energy
electron beam
transported to
Tuning line dump
Positron Workshop
DC Tuning line
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Yield vs Energy
• Yield of 1.5 at 150 GeV
• Yield of 0.75 at ~125 GeV
• Yield of 0.5 at ~115 GeV
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Positron Workshop
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