A Transverse Profile Imager for SwissFELRasmus Ischebeck
Rasmus Ischebeck
A Transverse Profile Imager for SwissFEL
> Profile measurement in FELs
> Imaging scintillating crystals
> Applications
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Rasmus Ischebeck
Transverse Profile Monitors
3University of Illinois
Rasmus Ischebeck
Profile Measurement in FELs
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Rasmus Ischebeck
Coherent OTR
5Joe Frisch
Rasmus Ischebeck
Coherent OTR
6Joe Frisch
Rasmus Ischebeck
1-Dimensional Profile Monitor
8Gian Luca Orlandi, Prajwal Mohanmurthy
Rasmus Ischebeck
x-y Correlations> Intrinsic correlation
> Explicit x-y dependency introduced by RF deflector
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Rasmus Ischebeck
A Transverse Profile Imager for SwissFEL
> Profile measurement in FELs
> Imaging scintillating crystals
> Applications
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Rasmus Ischebeck
2-Dimensional Profile Monitors> Optical transition radiation (OTR)
> Scintillation
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Rasmus Ischebeck
Imaging Scintillators
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Electron Beam Profile MonitorsScintillators, OTR Screens & Wire Scanners
13Rasmus Ischebeck – Scintillators for SwissFEL
Installed scintillators
•Ce:YAG•5 µm•20 µm•200 µm
•Ce:LuAG•200 µm
Electron Beam Profile MonitorsVisual Light Optics• OTR screen / scintillator is at an angle of 45º to the
optical axis• For overview camera (1:5.3 demagnification)
• Use Scheimpflug criterion to correct image plane orientation
• For 1:1 imaging• Perspective control lens is not available commercially• Only central part (~1…2 mm) of the screen can be
imaged within depth of field
14Rasmus Ischebeck – Scintillators for SwissFEL
Rasmus Ischebeck
Design Considerations> Scheimpflug imaging principle
> Snell’s law of refraction
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Observation of the Scheimpflug imaging principleallows to image the entire screen without depth-of-field issues.To avoid astigmatism, the lens is not tilted, butthe detector is tilted. For a 1:1 imaging, we tiltthe CMOS sensor by 15º.
The YAG / LuAG scintillators are observed at suchan angle that Snell’s law of refraction is observed.As a consequence, we can image beams that aresmaller than the thickness of the scintillator.
Rasmus Ischebeck
Imaging Scintillating Crystals
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Rasmus Ischebeck
Imaging Scintillating Crystals
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Rasmus Ischebeck
Imaging Scintillating Crystals
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Rasmus Ischebeck
Imaging Scintillating Crystals
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Rasmus Ischebeck
Trigonometry…
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Observed Beam Size
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Rasmus Ischebeck
Ideal Observation Angle
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Measurement Principle> Combination of two monitors:
> Scintillating crystal> Optical transition radiation
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Rasmus Ischebeck
Implementation
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to camera
(coherent)OTR
Rasmus Ischebeck
Screen Monitor
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Rasmus Ischebeck
A Transverse Profile Imager for SwissFEL
> Profile measurement in FELs
> Imaging scintillating crystals
> Applications
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Rasmus Ischebeck
Quadrupole Scan
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Beam Transmitted Through Slit
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Rasmus Ischebeck
Slice Emittance Measurements> Slice emittance measurement of a 1.3 pC beam
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Measurement performed by
Eduard Prat & Marta Divall
200 µm
Rasmus Ischebeck
Slice Emittance Measurement
32Eduard Prat
Rasmus Ischebeck
Slice Emittance Measurements> Core slice emittance as a function of charge
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Measurements performed by
Eduard Prat & Marta Divall
Rasmus Ischebeck
A Transverse Profile Imager for SwissFEL> A transverse profile imager that considers
> Snell’s law of refraction in the scintillating crystal> The Scheimpflug imaging condition
> Prototype installed at the SwissFEL Injector Test Facility> Resolution measured with this prototype: σ ≲ 10 µm, ε ≲ 30 nm> Sensitivity: Q ≲ 1 pC
Next Plans> Prove immunity to coherent OTR> Start series production
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Rasmus Ischebeck
Thank You to…> Hansueli for the technical design> The AMI team for manufacturing the components> Markus for the assembly> Markus, Albert & the vacuum group for installation> Eduard the emittance measurement software, and for using the new profile
monitor extensively for emittance measurements> Gian Luca, Marta, Simona, Carlo, Thomas & Eduard for the measurements
presented in this talk> Vincent for help with optical design> Andrea for support with patenting the design, and with connections to industry> Helge for camera server software, and Babak for synchronized data acquisition> The entire Commissioning and Operations crew
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Rasmus Ischebeck