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Rasmus IschebeckRasmus Ischebeck
A Transverse Profile Imager for SwissFEL
> Profile measurement in FELs
> Imaging scintillating crystals
> Applications
22
Rasmus IschebeckRasmus Ischebeck
1-Dimensional Profile Monitor
88Gian Luca Orlandi, Prajwal
Mohanmurthy
Rasmus IschebeckRasmus Ischebeck
x-y Correlations
> Intrinsic correlation
> Explicit x-y dependency introduced by RF deflector
99
Rasmus IschebeckRasmus Ischebeck
A Transverse Profile Imager for SwissFEL
> Profile measurement in FELs
> Imaging scintillating crystals
> Applications
1010
Rasmus IschebeckRasmus Ischebeck
2-Dimensional Profile Monitors
> Optical transition radiation (OTR)
> Scintillation
1111
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 IschebeckRasmus Ischebeck
Design Considerations
> Scheimpflug imaging principle
> Snell’s law of refraction
1515
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 IschebeckRasmus Ischebeck
Measurement Principle
> Combination of two monitors:
> Scintillating crystal
> Optical transition radiation
2323
Rasmus IschebeckRasmus Ischebeck
A Transverse Profile Imager for SwissFEL
> Profile measurement in FELs
> Imaging scintillating crystals
> Applications
2828
Rasmus IschebeckRasmus Ischebeck
Slice Emittance Measurements
> Slice emittance measurement of a 1.3 pC beam
3131
Measurement performed by
Eduard Prat & Marta Divall
200 µm
Rasmus IschebeckRasmus Ischebeck
Slice Emittance Measurements
> Core slice emittance as a function of charge
3333
Measurements performed by
Eduard Prat & Marta Divall
Rasmus IschebeckRasmus 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
3434
Rasmus IschebeckRasmus 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
3535