re-configuration of the linac reference system at slaciwaa2016 - re-configuration of the linac...

Re-configuration of the Linac reference system at SLAC IWAA2016 – Grenoble, October 2016

Georg Gassner Michael Gaydosh

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A Changing SLAC Linac

IWAA2016 - Re-configuration of the Linac reference system at SLAC Grenoble, October 2016

Sector 0 Sector 10 Sector 20 Sector 30

0 500 1000 1500 2000 2500 3000 3500

Extension line Bypass line

LCLS-I

Bypass BSY LTU EBD

Undulators

SXU

HXUL1 L2 L3

SRF Cryomodules (L0, L1, L2, L3)

joined by warm beamline sections

Z (m)

crossover

Beam SpreaderDogleg

µ wall

Cryoplant & cryo distribution

Injector & L0

Dumps

Proposed FACET II

FEE

End Stations

- 1966 – 2008 (SLC, PEP, PEPII)

- 2009 – 2012

- 2012 – 2016

- 2016 –

LCLS-I LCLS-I

LCLS-I

FACET

LCLS-II (construction)

FACET II (proposed)

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Linac Laser Alignment System (LLAS)


270 girders of 12m and 3m length. Every girder has one Fresnel zone plate target.

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Linac Alignment System - Girder


All components on top are aligned to the girder. Upstream end has Fresnel zone plate target. Downstream end coupled with next girder.

Target

Quadrupole

Accelerator Structure

Waveguides

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Linac Alignment System - Girder


Height / Roll Adjustment jacks

Horizontal Adjustment Jack

Telescope mount

Fiducials

Fresnel Lens Target

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Removal of Light Pipe from Sector 0 – Sector 10


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Reconfigure Linac Laser Alignment System (1)


Every Lens has different focal length to focus dot in S0 • Option A) New Fresnel lens at every location (too expensive). • Option B) One glass lens 100m upstream of S10 (radiation

damage, glass would turn black). • Option C) Telescopic mirror system (Alan Fisher).

Spherical Lenses

Sector 10-9

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d1 d2

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Current Image at S0 Simulated Image at S10 after re-configuration (VirtualLab)

5mm

Distortions are caused by the hole in the large mirror and the supports for the small mirror.

(Alan Fisher)

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Alignment Network S0-S30 – Layout


S0-S10 no longer has a light pipe and the bypass lines are not connected to the girders -> Monument based network. Opposing wall monuments to mitigate effect of refraction.

3km

12m

3.3m

Cryomodule Wall Monument Floor Monument

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Alignment Network S0-S30 - Measurements


311 Laser Tracker (Leica AT401/402) setups with 5082 measurements 577 Height differences (Leica DNA03) 200 Linac Light Pipe readings Least Squares Adjustment with LEGO software which allows the Linac Light Pipe readings (jackpoint to target σ=±0.5mm ) to be included as deviations from a straight line.

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Alignment Network S0-S30 – Results (1)


13 µrad

Comparison of coordinate results between adjustment with LLAS and without LLAS. Location of

radiation chicane no direct line of sight

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Alignment Network S0-S30 – Results (2)


Comparison of nominal location of Linac quadrupoles with their actual location along the beamline: The length of the Linac is 75 mm longer than designed. The pitch is 3 µrad steeper than designed in 1964.

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Summary


The Linac Laser Alignment System has been re-configured for fast recovery after earthquake (S10-S30) (1-2days for 2km beamline) Installed a machine independent monument network throughout the 3km long Linac in preparation for LCLS - II

re-configuration of the linac reference system at slaciwaa2016 - re-configuration of the linac...

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