UF96 UEM beam stability study: - PowerPoint Presentation

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UF96 UEM beam stability study:A novel nondestructive diagnostic method for mega-electron-volt ultrafast electron diffractionXi Yang Representing UEM LDRD team

22

nd

ATF Users’ Meeting

December 3 - 5, 2019

NSLS-IID. Bergman, L. Doom, M Fulkerson, G. Ganetis, Y. Hidaka, B. Kosciuk, D. Padrazo, T. Shaftan, V. Smalyuk, C. Spataro, X. Yang, J. Rose, G. Wang, K. Wilson, L. H. Yu, etc. ATFM. Fedurin, M. Babzien, R. Malone, k. Kusche, C. Cullen, etc.CMPMSDJ. Li, L. Wu, Y. Zhu, etc.ShanghaiTech University W. WanUEM LDRD participants

Motivation: Feasibility study of LDRD for UEM (ID: 305506, UED)A novel method of beam diagnostics: Bragg-diffractionExperimental resultsConclusionOutline

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Schematic layout of the UED beamline

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Beam

The UEM resolution for the proof-of-principle experiment is <200nm, dominated by chromatic aberration.The energy jitter will limit the UEM performance in the low-charge accumulation mode.Single-shot resolution of the UEM system will be limited by the energy spread at the required charge.Motivation

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Develop a real-time nondestructive diagnostic method for UED (also applicable to UEM by changing the setting of the lenses to image the diffraction pattern) Idea of BDM: The information of the electron beam energy, energy fluctuation and spatial-pointing jitter is intrinsically encoded to the shot-to-shot diffraction image. Without perturbing the ongoing experiment, one can simultaneously measure the shot-to-shot energy fluctuation and spatial-pointing jitter of the electron beam via eigen-decomposing the variation of diffraction patterns to two decoupled modes:1st

mode: distance between Bragg peaks as well as its variation (radial mode): beam energy fluctuation.2nd mode: overall lateral shift of the whole pattern (drift mode): spatial-pointing jitter. Bragg-diffraction method

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Develop a real-time nondestructive diagnostic method for UED (also applicable to UEM by changing the setting of the lenses to image the diffraction pattern) Idea of BDM: The shot-to-shot diffraction images intrinsically contain the following information about electron beam:Mean energyEnergy spreadShot-to-shot energy fluctuation Shot-to-shot spatial-pointing jitter

Without perturbing the ongoing experiment, one can simultaneously measure these electron beam parameters via eigen-decomposing the variation of diffraction patterns to two decoupled modes:Radial mode: distance between Bragg peaks as well as its variation: beam energy fluctuation.Drift mode: overall lateral shift of the whole pattern: spatial-pointing jitter. Bragg-diffraction method

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ExperimentOptimize the measurement precision Single-shot image in data analysis.Advance algorithm for peak finding.The separation between the peak pair ij (Dij

) is determined by Interplane distance d Distance between the sample and the detector LS2D Electron beam energy EThe measured separation can be used to calibrate the shot-to-shot energy jitter based on

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The shot-to-shot energy variation measured at two different electron beam energies: 0.216% r.m.s. at the nominal energy E0 (green)0.239% r.m.s. at 1.06E0

(red)Experimental results9

(Vertical)

(Horizontal)

The measured shot-to-shot pointing jitter is about 10 µrad, both horizontal (a) and vertical (b), at two different electron beam energies:

E

0

and 1.06

E

0

Correlation of the pointing jitter and energy jitter.Beam energy spread measured by the BDM (red circles) and by direct beam size measurement (green triangles), compared to the Impact-T simulations (black squares). The horizontal error comes mainly from the laser power fluctuation. The vertical error is described in the text.Measurement of electron beam energy spread

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η

y

≈ 0.01 m

Energy jitter (blue) and pointing jitter in y (orange)

vs

shot number.

Charge (pC)

dE

/E

0.05

0.0001

5

0.0100

Beam energy calibration with RF modulation

11Calibrate beam energy at different RF settingIntroducing RF modulation we can measure dispersion at detector with better precision.

We demonstrated a novel beam diagnostic methodBeam parameters measuredShot-by-shot energy jitter with 2·10-3Shot-by-shot spatial-pointing jitter 10 µradDispersion at the detectorEnergy spread of the electron beam with different charges

Potential applications:Real-time energy measurement enables the filtering process to remove off-energy shotsApplicable to the entire UED user community, in addition to the traditional electron beam diagnostics.Publication:Yang, X., et al. A novel nondestructive diagnostic method for mega-electron-volt ultrafast electron diffraction. Scientific Reports 9, 17223 (2019). Conclusion

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Thank you