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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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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Trigonometry…

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Observed Beam Size

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Ideal Observation Angle

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Measurement Principle> Combination of two monitors:

> Scintillating crystal> Optical transition radiation

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Implementation

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to camera

(coherent)OTR

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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