Tomographic transverse phase space measurements at PITZ.

Transcription

1 Tomographic transverse phase space measurements at PITZ. > Photo-Injector Test facility at DESY in Zeuthen - PITZ > Tomography in beam diagnostics > Hardware > Measurements & evaluation Georgios Kourkafas, for the PITZ team DPG Frühjahrstagung, Göttingen, > Features & obstacles > Summary and outlook

2 Photo Injector Test facility in Zeuthen (PITZ) > Test and optimize sources of high brightness electron beams: Minimized transverse projected emittance : < 1 mm mrad for 1 nc (requirement of the European XFEL photo-injector) Georgios Kourkafas Tomographic transverse phase space measurement at PITZ Page 2 of 9

3 Photo Injector Test facility in Zeuthen (PITZ) > Test and optimize sources of high brightness electron beams: Minimized transverse projected emittance : < 1 mm mrad for 1 nc (requirement of the European XFEL photo-injector) 28 MeV/c 7 MeV/c 14-cell CDS cavity (normal conducting) max gradient 14MV/m maximum momentum 40MeV/c (nominal > 25MeV/c) Cs 2 Te photocathode Bucking solenoid 1½ cell RF gun cavity 1.3 GHz laser beam Main solenoid Georgios Kourkafas Tomographic transverse phase space measurement at PITZ Page 2 of 9 e- beam

4 Photo Injector Test facility in Zeuthen (PITZ) > Test and optimize sources of high brightness electron beams: Minimized transverse projected emittance : < 1 mm mrad for 1 nc (requirement of the European XFEL photo-injector) 28 MeV/c 7 MeV/c 14-cell CDS cavity (normal conducting) max gradient 14MV/m maximum momentum 40MeV/c (nominal > 25MeV/c) transverse projected emittance Cs 2 Te photocathode 1½ cell RF gun cavity 1.3 GHz laser beam Bucking solenoid Main solenoid Georgios Kourkafas Tomographic transverse phase space measurement at PITZ Page 2 of 9 e- beam

5 Tomography Radon transform -> Reconstruction of an object from its projections at different angles Georgios Kourkafas Tomographic transverse phase space measurement at PITZ Page 3 of 9

6 Tomography Radon transform -> Reconstruction of an object from its projections at different angles Real space Phase space Georgios Kourkafas Tomographic transverse phase space measurement at PITZ Page 3 of 9

7 Tomography Radon transform -> Reconstruction of an object from its projections at different angles Real space common projection in each axis (X/Y) Phase space Georgios Kourkafas Tomographic transverse phase space measurement at PITZ Page 3 of 9

8 Tomographic reconstruction of the phase space FODO cell focusing drift defocusing drift Image courtesy: G. Asova b x e - b y > Quadrupoles, forming a FODO lattice, oppose a 180 rotation in the phase space Georgios Kourkafas Tomographic transverse phase space measurement at PITZ Page 4 of 9

9 Tomographic reconstruction of the phase space FODO cell focusing drift defocusing drift Image courtesy: G. Asova b x e - b y φ = 45 φ = 45 φ = 45 > Quadrupoles, forming a FODO lattice, oppose a 180 rotation in the phase space > Screens capture projections, where beta value (beam size) and phase advance (projection angle) are constant Georgios Kourkafas Tomographic transverse phase space measurement at PITZ Page 4 of 9

10 Tomographic reconstruction of the phase space FODO cell focusing drift defocusing drift Image courtesy: G. Asova b x e - b y φ = 45 φ = 45 φ = 45 > Quadrupoles, forming a FODO lattice, oppose a 180 rotation in the phase space > Screens capture projections, where beta value (beam size) and phase advance (projection angle) are constant > Reconstruction from the corresponding transform matrices, using the Maximum ENTropy algorithm (MENT) Georgios Kourkafas Tomographic transverse phase space measurement at PITZ Page 4 of 9

11 Hardware description > Matching section: Short quadrupoles, with strong focusing Georgios Kourkafas Tomographic transverse phase space measurement at PITZ Page 5 of 9

12 Hardware description > Matching section: Short quadrupoles, with strong focusing > FODO cells: Quadrupole magnets Screen stations Steering magnets BPMs Georgios Kourkafas Tomographic transverse phase space measurement at PITZ Page 5 of 9

13 Measurement procedure and results (1nC, 25MeV) 1. Screen projections Georgios Kourkafas Tomographic transverse phase space measurement at PITZ Page 6 of 9

14 Measurement procedure and results (1nC, 25MeV) 1. Screen projections 2. Axis projections (X + Y) Georgios Kourkafas Tomographic transverse phase space measurement at PITZ Page 6 of 9

15 Measurement procedure and results (1nC, 25MeV) 1. Screen projections 2. Axis projections (X + Y) 3. Algorithmic reconstruction of the phase space Georgios Kourkafas Tomographic transverse phase space measurement at PITZ Page 6 of 9

16 Measurement procedure and results (1nC, 25MeV) 1. Screen projections 2. Axis projections (X + Y) 3. Algorithmic reconstruction of the phase space (0.1% Intensity cut) Georgios Kourkafas Tomographic transverse phase space measurement at PITZ Page 6 of 9

17 Evaluation > Is the beam well matched in the 4 screens? Compare twiss parameters with the design values Evaluate mismatch: for Db < 20% a solution can always be found Design Parameter x-plane y-plane β α screens X-plane Y-plane Real Ideal Georgios Kourkafas Tomographic transverse phase space measurement at PITZ

18 Evaluation > Is the beam well matched in the 4 screens? Compare twiss parameters with the design values Evaluate mismatch: for Db < 20% a solution can always be found Design Parameter x-plane y-plane β α > Emittance value validation: Slit-scan measurements Simulations (ASTRA software) screens X-plane Y-plane Real Ideal Georgios Kourkafas Tomographic transverse phase space measurement at PITZ

19 Features & Obstacles + Advantages: Only one pulse needed -> reduced Signal-to-Noise ratio Two transverse planes can be resolved simultaneously Space-charge influence not included: Beam characteristics: low emittance, high charge density, moderate energy Matching section: strong impact -> not precise matching -> manual adjustment FODO lattice: emittance dominated region, but small discrepancies in phase calculations -> not precise reconstruction > Implementations needed: Incorporate space-charge impact for the matching procedure Refine transport matrix calculations for the phase space reconstruction Georgios Kourkafas Tomographic transverse phase space measurement at PITZ Page 8 of 9

20 Summary > The tomography module in PITZ is able to measure the phase space of an electron bunch with advanced features > Main obstacle: Space-charge impact > Next goals and improvements: Include space-charge effect -> - 5 available projections instead of 4, due to better matching - better reconstruction results Installation of pulse kickers -> measurements of a single pulse from a bunch train Georgios Kourkafas Tomographic transverse phase space measurement at PITZ Page 9 of 9

21 Thanks to G. Asova and the PITZ group. THE END.

22 Backup Slides Georgios Kourkafas Tomographic transverse phase space measurement at PITZ

23 Hallo influence on reconstruction Full charge 0.1% charge cut 1% charge cut Georgios Kourkafas Tomographic transverse phase space measurement at PITZ

24 Hallo influence on reconstruction Full charge 0.1% charge cut 1% charge cut Georgios Kourkafas Tomographic transverse phase space measurement at PITZ