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Tomography module for transverse phase-space measurements at PITZ . > Photo-Injector Test facility @ DESY in Zeuthen - PITZ > Tomography module > Measurement results > Conclusions and outlook G. Asova for the PITZ team DITANET 2011, Seville
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Tomography module for transverse phase-space measurements at PITZ .

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Tomography module for transverse phase-space measurements at PITZ. Photo-Injector Test facility @ DESY in Zeuthen - PITZ Tomography module Measurement results Conclusions and outlook. G. Asova for the PITZ team DITANET 2011, Seville. 1½ cell RF gun cavity 1.3 GHz. Cs 2 Te photocathode. - PowerPoint PPT Presentation
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Page 1: Tomography module for transverse phase-space measurements at PITZ  .

Tomography module for transverse phase-space measurements at PITZ .> Photo-Injector Test facility @ DESY in Zeuthen - PITZ

> Tomography module

> Measurement results

> Conclusions and outlook

G. Asova for the PITZ team

DITANET 2011, Seville

Page 2: Tomography module for transverse phase-space measurements at PITZ  .

Galina Asova | Tomography module for transverse phase-space measurements at PITZ | November 10th 2011 | Page 2

Photo-Injector Test facility

transverse projected emittance

25 MeV/c 6.7 MeV/c

Produce electron beams with minimized transverse emittanceas required for the European XFEL photo-injector:

< 1 mm mrad for 1 nC

laser beam

Bucking solenoid

Main solenoid

Cs2Te photocathode

e- beam

1½ cell RF gun cavity 1.3 GHz

Page 3: Tomography module for transverse phase-space measurements at PITZ  .

Galina Asova | Tomography module for transverse phase-space measurements at PITZ | November 10th 2011 | Page 3

Phase-space portraits

> Standard measurement method – slit scan

> Separately scan the two transverse planes

> Sensitive to signal-to-noise ratio → multi-shot measurements to collect as full as possible signal → smearing of the phase space due to possible machine fluctuations

0.1 nC, 14 laser pulses1 nC, 6 laser pulses

Page 4: Tomography module for transverse phase-space measurements at PITZ  .

Galina Asova | Tomography module for transverse phase-space measurements at PITZ | November 10th 2011 | Page 4

Tomography

Reconstruction of an object from a number of its projections at different angles -

Radon transform

Page 5: Tomography module for transverse phase-space measurements at PITZ  .

Galina Asova | Tomography module for transverse phase-space measurements at PITZ | November 10th 2011 | Page 5

Phase-space tomographic reconstruction

> equidistant angular steps between the screens for both planes (2D)

> the beam parameters at the entrance of the lattice are adjusted

FODO cell(focusing – drift – defocusing – drift)

e-

x

y

Page 6: Tomography module for transverse phase-space measurements at PITZ  .

Galina Asova | Tomography module for transverse phase-space measurements at PITZ | November 10th 2011 | Page 6

> Design for 15-30 MeV/c, 1 nC

> Challenging matching due to space-charge impact

> Slow and complicated analysis

Tomography module

e-

Page 7: Tomography module for transverse phase-space measurements at PITZ  .

Galina Asova | Tomography module for transverse phase-space measurements at PITZ | November 10th 2011 | Page 7

Major components

x 5 FODO cells

Components (details in poster):

> Quadrupole magnets in FODO cells

> Screen stations

> Steering magnets

> BPMs

Short cells:

> Short quadrupoles Leff = 43 mm

> Strong focusing

> Precise alignment along the full FODO lattice

20 mrad quadrupole angular misalignment

100 m longitudinal misplacement

Page 8: Tomography module for transverse phase-space measurements at PITZ  .

Galina Asova | Tomography module for transverse phase-space measurements at PITZ | November 10th 2011 | Page 8

Measurements with the setup

> Nominal charge of 1 nC

Emittance evolution along the beamline - cross-check the calculated emittance versus results from slit scans

Different charge densities at the photo-cathode

Reproducibility of the measurements

> Lower charges ≥ 100 pC

> Common machine setup:

Max power from gun and booster, phases for max mean momentum gain, ~ 25 MeV/c

Laser temporal profile – flat top with 2/22\2 ps

Page 9: Tomography module for transverse phase-space measurements at PITZ  .

Galina Asova | Tomography module for transverse phase-space measurements at PITZ | November 10th 2011 | Page 9

Measured phase spaces, 1 nCT

OM

O,

z =

13.

04 m

Strong tails Substructure

Orthogonal!

1 bunch in the train

Sli

t sc

ans,

z =

5.7

4 m

6 bunches in the train

Page 10: Tomography module for transverse phase-space measurements at PITZ  .

Galina Asova | Tomography module for transverse phase-space measurements at PITZ | November 10th 2011 | Page 10

Beam profile along the beamline

0

0.5

1

1.5

2

2.5

3

3.5

4

0 2 4 6 8 10 12 14 16

z [m]

be

am

siz

e [

mm

]

Xσ σY σXY σXY_ASTRA

EMSY1TOMOGRAPHY

EMSY3

1 nC

measured x measured ymeasured xy simulated xy

Page 11: Tomography module for transverse phase-space measurements at PITZ  .

Galina Asova | Tomography module for transverse phase-space measurements at PITZ | November 10th 2011 | Page 11

Emittance evolution along the beamline

x, y ~ 30%

EMSY1

TOMO

EMSY3

1 nC

Page 12: Tomography module for transverse phase-space measurements at PITZ  .

Galina Asova | Tomography module for transverse phase-space measurements at PITZ | November 10th 2011 | Page 12

Matching for 1 nC, 25 MeV/c

> Hard to keep both planes periodic along the FODO lattice

> y matched very good, but not x

consistent for different laser spot sizes, solenoid current, quadrupole settings, bunch charges

x

y

y < 20% - for such mismatches a solution can always be found

[%]β

ββΔβ

d

md

Page 13: Tomography module for transverse phase-space measurements at PITZ  .

Galina Asova | Tomography module for transverse phase-space measurements at PITZ | November 10th 2011 | Page 13

> As the area of the phase space decreases, the substructure comes closer to the main beam for higher solenoid currents

100 pC X-plane

> Emittance decreases with the solenoid focusing

> the orientation of the three distributions

is the same – matching worked in these cases

396 A392 A 398 A

x

y

Page 14: Tomography module for transverse phase-space measurements at PITZ  .

Galina Asova | Tomography module for transverse phase-space measurements at PITZ | November 10th 2011 | Page 14

Conclusions & outlook

> Tomography module successfully commissioned

> Results cross-checked with standard for PITZ slit scans

> Details on the phase spaces downstream the beamline reconstructed in great details for short bunch trains

> The two transverse planes resolved simultaneously

> Kicker magnets to be installed for measurements of selected bunch in the train

> Transverse deflecting cavity for longitudinal phase-space measurements

Page 15: Tomography module for transverse phase-space measurements at PITZ  .

Galina Asova | Tomography module for transverse phase-space measurements at PITZ | November 10th 2011 | Page 15

> DESY, Zeuthen site:J. Bähr, H.J. Grabosch, M. Gross, A, Donat, I. Isaev*, Y. Ivanisenko**, G. Kourkafas***, G. Klemz, D. Malyutin, M. Krasilnikov, M. Mahgoub, J. Meissner, A. Oppelt, M. Otevrel, B. Petrosyan, S. Rimjaem, A. Shapovalov*, F. Stephan, G. Vashchenko

> DESY, Hamburg site:A. Brinkmann, K. Flöttmann, S. Lederer, D. Reschke, S. Schreiber

> BESSY Berlin:R. Ovsyannikov, D. Richter, A. Vollmer

> ASTeC STFC Daresbury Lab:B. Militsyn

> INRNE Sofia:G. Asova, I. Bonev, I. Tsakov

> INR Troitsk:A.N. Naboka, V. Paramonov, A.K. Skassyrskaia, A. Zavadtsev

* on leave from NRNU, Moscow, Russia

** on leave from IERT, NAS, Kharkiv, Ukraine

*** on leave from Athens, Greece

> LAL Orsay:M. Jore, A. Variola

> LASA Milano:P. Michelato, L. Monaco, D. Sertore

> MBI Berlin:I. Will

> TU Darmstadt:S. Franke, W. Müller

> Uni Hamburg:J. Rönsch-Schulenburg

> YERPHI Yerevan:L. Hakobyan, M. Khojoyan

Colleagues participating in measurements / new design:

R. Brinkmann, U. Gensch, J. Knobloch, L. Kravchuk, V. Nikoghosyan, C. Pagani, L. Palumbo, J. Rossbach, W. Sandner, S. Smith, T. Weiland, G. Wormser

The PITZ collaboration

Page 16: Tomography module for transverse phase-space measurements at PITZ  .

Galina Asova | Tomography module for transverse phase-space measurements at PITZ | November 10th 2011 | Page 16

Tomographic reconstruction

> N rotations → N projections of the (x, y)

> Which algorithms are applicable to small N? → N = 4

Applicability of different algorithms to limited data sets

@ UMER, PITZ? @ FLASH, PITZ

Backprojection Filtered backprojection Algebraic reconstruction Maximum entropy

Page 17: Tomography module for transverse phase-space measurements at PITZ  .

Galina Asova | Tomography module for transverse phase-space measurements at PITZ | November 10th 2011 | Page 17

Reconstruction of 1 nC, intensity cut

Slit scan

0.5 % intensity cut

x, N = 1.3 mm mradx, N = 1.07 mm mrad

Tomography

The contribution of the low-intensity bins is negligible.

Page 18: Tomography module for transverse phase-space measurements at PITZ  .

Galina Asova | Tomography module for transverse phase-space measurements at PITZ | November 10th 2011 | Page 18

Reconstruction of 1 nC, intensity cut

Slit scan

5 % intensity cut

x, N = 1.06 mm mradx, N = 1.07 mm mrad

Tomography

> Common features in both distributions

> elongated non-symmetric tails

> non-symmetric density of the core

Page 19: Tomography module for transverse phase-space measurements at PITZ  .

Galina Asova | Tomography module for transverse phase-space measurements at PITZ | November 10th 2011 | Page 19

PITZ

Cs2Te cathode

transverse projected emittance

RF gun + solenoidsbooster

Produce electron beams with minimized transverse projected emittance as required for the European XFEL, < 1 mm mrad

Beam momentum ~ 6.7 MeV/c /25 MeV/c

Nominal bunch charge 1 nC

Page 20: Tomography module for transverse phase-space measurements at PITZ  .

Galina Asova | Tomography module for transverse phase-space measurements at PITZ | November 10th 2011 | Page 20

Page 21: Tomography module for transverse phase-space measurements at PITZ  .

Galina Asova | Tomography module for transverse phase-space measurements at PITZ | November 10th 2011 | Page 21

Emittance measurements at PITZ

Phase-space tomographic reconstruction

FODO cell(focusing – drift – defocusing – drift)

> equidistant angular steps between the screens for both planes (2D)

> rms spot size is uncharged

> the beam parameters at the entrance of the lattice are adjusted

> the data treatment assumes linear transport between the screens

e- beam

Page 22: Tomography module for transverse phase-space measurements at PITZ  .

Galina Asova | Tomography module for transverse phase-space measurements at PITZ | November 10th 2011 | Page 22

Screen stations

> Actuator holding Ce:YAG-doped and OTR screens

> Precisely movable actuator

> 2 different actuator designs

> Design momentum for high charge densities (30 MeV/c, 1 nC)

> Small beam dimensions (0.125 mm for 30 MeV/c)

> Minimize multiple scattering within the Si layer

100 m thickness

Test, 2 optical systemsNominal

Page 23: Tomography module for transverse phase-space measurements at PITZ  .

Galina Asova | Tomography module for transverse phase-space measurements at PITZ | November 10th 2011 | Page 23

Optical system

M = 0.13, to adjust the beam orbit

M = 0.21, resolution about 45 um

Movable mirror to compensate the different path length for YAG/OTR screen

Pipe to mitigate stray light

16-bit monochromatic CCD camera

Page 24: Tomography module for transverse phase-space measurements at PITZ  .

Galina Asova | Tomography module for transverse phase-space measurements at PITZ | November 10th 2011 | Page 24

Transverse phase-space measurements at PITZ

Single slit scan – standard measurement procedure

yxxy εεε Q [nc] xy [mm mrad] *

1 0.7 ± 0.03

0.25 0.33

0.1 0.21

> Improved RF gun stability

> Improved laser stability and beam transport

> Replaced magnetizable components → critical at low energies

* Values obtained from solenoid scans for various laser spot sizes.