A Transverse Profile Imager for SwissFEL Rasmus Ischebeck.

A Transverse Profile Imager for SwissFELRasmus Ischebeck

Rasmus IschebeckRasmus Ischebeck

A Transverse Profile Imager for SwissFEL

> Profile measurement in FELs

> Imaging scintillating crystals

> Applications

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Transverse Profile Monitors

33University of

Illinois


Profile Measurement in FELs

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Coherent OTR

55Joe

Frisch


Coherent OTR

66Joe

Frisch


1-Dimensional Profile Monitor

88Gian Luca Orlandi, Prajwal

Mohanmurthy


x-y Correlations

> Intrinsic correlation

> Explicit x-y dependency introduced by RF deflector

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> Applications

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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


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.


Imaging Scintillating Crystals

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Trigonometry…

2020


Observed Beam Size

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Ideal Observation Angle

2222


Measurement Principle

> Combination of two monitors:

> Scintillating crystal

> Optical transition radiation

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Implementation

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to camera

(coherent)OTR


Screen Monitor

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> Applications

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Quadrupole Scan

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Beam Transmitted Through Slit

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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


Slice Emittance Measurement

3232Eduard Prat


Slice Emittance Measurements

> Core slice emittance as a function of charge

3333

Measurements performed by

Eduard Prat & Marta Divall



> 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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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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A Transverse Profile Imager for SwissFEL Rasmus Ischebeck.

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