Working Group C Report: Application to FELs Heinz-Dieter Nuhn, SLAC / SSRL

The Start-End Model

Drive laser

Physical Layout

RF Gun

Beam line

Bunch Compressor

FEL

FEL Beam Optics

Flow Model

Laser

Gun

Linac

FEL

FEL Optics

Compressor

Multi-stage FEL

Sven Reiche - ICFA Sardinia

Application to FELs. Working Group C Summary

CodesDrive Laser :?Gun :Astra, ParmelaLinac :ElegantBunch Compressor :Traffic4, (Elegant)FEL :Genesis 1.3, Ginger, FastFEL Optics :SRW, Phase, R. Bionta@LLNL, Shadow


+ HDF

File Format

Applications native file formatNeed conversion from/to other program format.Difficult to maintain.Often fixed format.Pre- & postprocessing must be part of the code distribution.Self-Describing Data Set (SDDS)Library function available for code developer.Existing toolset for processing and plotting data.Simplifies the start-end flow.Good for homogeneous data sets (particle distribution).XMLFiles are well-formatted, valid and platform-independent.Various libraries and editor available.Flexible transformation to other formats .Overhead for long similar data sets.



Improvement in the Future

Add FEL optics codes to start-end simulation.Improved support of standardized format.Fully self-describing file formats for all major data streams (SDDS almost perfect).Easier/automated set-up of the control input file for each code.Scripted execution.User-friendly GUI, built on top of the scripting shell.



Working Group ContributionWhat have we learned from SASE Experiments ?Alex MurokhDepartment of Astronomy and Physics, UCLA, Los Angeles, CA, USA


Analysis of VISA DataCheck 3D Scaling Laws Data Can only be analyzed fully through Simulation Codes

More Detailed Measurement of Beam Parameters is Important for a Better Comparison with Theory


3-D Scaling Laws


Start-To-End Simulation ResultsStart-to-end numerical model of VISA is strongly supported by fine features of FEL radiation reproduced in GENESIS


Working Group ContributionPERSEO - A Tool For FEL Simulations with MATHCAD ?Luca GiannessiENEA, Frascati, Rome, Italy





Working Group Contribution"Optics-Free" FEL Oscillators Vladimir LitvinenkoFEL Laboratory, Department of Physics, Duke University, Durham, NC, USA


Optics-Free FEL oscillators

Vladimir N. Litvinenko FEL laboratory, Department of Physics, Duke University, Durham NC, USA

SASE FELs demonstrated the capability of providing very high gain and short pulses of radiation. Meanwhile, the spectra of SASE FELs is rather wide (~0.3-0.5%) compared with typical short wavelengths FEL-oscillators (0.01% - 0.0003% in OK-4 FEL). Absence of good optics in VUV and X-ray ranges makes traditional oscillator schemes prohibitory complex or impossible. Need for Optics-free FEL oscillator

A high-gain (G ~ 103-106) FEL oscillator driven by a linac or ERL The optical feed-back is provided by high brightness e-beam. This scheme provides the advantages typical for FEL oscillators: continuously tunable; high spectral brightness; narrow linewidth for direct use for most of experiments; laser pulses 10-20 shorter than the e-bunches; full transverse and longitudinal coherence.


Optics Free FEL Oscillator

Use lower energy low current e-beam with VERY LOW emittance and low energy spread for the feed-back The fb-beam is modulated and carries-on the modulation to the entrance of the FEL

High Gain FEL

Fresh e-beam

Used e-beam

Photons

Photons

Radiator

Modulator

Source


Preserving the phase correlations

Compaction factors

Emittance effect is compensated by sextupoles in the achromatic arcs (flat beam is desirable)

Arcs comprising from N symmetric cells with tune advance =m/N; m-integer; will provide for the cancellation of thenonlinear kicks, but a non-zero value of ~ K2.

The fact that e-beam passes only once (in contrast with storage rings) allows to use very strong nonlinear elements in the system

Quantum fluctuations of synchrotron radiation is the main limiting factorStill it is doable !!!100 bending magnets per arc


Feed-back Radiation

Coherent radiation from the feed-back e-beamEe ~ 0.5 GeV; Nw ~ 100; lW ~ 0.6 mm*, Lw~ 6 cm; Ipeak ~1 A

Number of the coherently radiating electrons isdefined by the beam current, the slippage length andthe degree of the density modulation (M)

* 1.2 mm for 20 GW mm-wave wiggler


Summary

Low beam current and small emittance provide for a toy-size of the magnetic system for the arcs

Magnets will be 2 x 4 cm2 in cross-section

Scheme is feasible if e-beam with 1A peak current has low energy spread and 0.1-0.5 mm mrad normalized emittance Use of a flat beam with few psec duration is preferable Higher order terms must be taken into account (using simplectic high order integrators) to check the resultsThe main limiting factor seems to be quantum fluctuation of synchrotron radiation requiring rather low energy for fb-beam CSR effects, stability of power supplies, quality of the magnets require additional studies


Working Group ContributionA Recirculating Linac Facility for Ultra-Fast X-Ray Science ?Steve LidiaLawrence Berkeley National Laboratory, Berkeley, CA, USA


Steve LidiaICFA Workshop, Chia LagunaJuly, 2002

Strong scientific case for time resolved experiments at timescales of the order of atomic vibrational period 1 /vsound ~ 100 fs

Ultrafast structural dynamics in solidsOrder/disorder transitions (melting)Solid-solid phase transitionsSurfaces

Ultrafast molecular dynamicsStructural dynamics of the transition stateSolvent/solute interactions (solvent structure)

Ultrafast processes in biology

Atomic and molecular physics

Magnetization and spin dynamics

Dynamics in warm dense matter

diffraction angle

time delay

time delay

x-ray probe

visible pump

Ordered crystals - phase transitions, coherent phonons

detector

Time-resolved x-ray diffraction

Time-resolved EXAFS, NEXAFS, surface EXAFS

delay

x-ray probe

visible pump

r

energy

time

K

edge

absorption

f(r)

Complex/disordered materials - chemical reactions

bonding geometry

surface dynamics


Steve LidiaICFA Workshop, Chia LagunaJuly, 2002

An ultra-fast x-ray user facility driven by scientific needs in Physics, Chemistry and Biology

ID and bend magnet beamlines1 - 10 keV

Baseline parameters: Short X-ray pulse

Documents

Working Group C Report: Application to FELs Heinz-Dieter Nuhn, SLAC / SSRL