Change in Program Tuesday Morning Review of 2002 CSR Workshop (T. Limberg, 20 min) CSR calculation Models (M. Dohlus, 40 min) The 3D Codes TraFiC4 and CSRtrack (T. Limberg, 20 min) Coffee Break

From Zeuthen 2002 to Here Torsten Limberg DESY Zeuthen 2003

2002 Zeuthen Workshop Workshop web site:

The (Bench-Marking) Case: A simple unshielded Four-Bend Chicane

Beam Parameters

Simulation Codes Code Name AlgorithmComments J-Lab Code (R. Li) 2-D continous charge distribution slow, even slower when sharp peaks have to be resolved TraFiC 4 3-D continous charge distribution „ (parallel computing helps) TREDI (ENEA) 3-D Macroparticles CSR part still tested elegant (M. Borland) P. Emma MATLAB M. Dohlus 1-D1-D 1-D Green function tracking no transverse fields no transverse fields no transverse variation of fields (influences slice emittance) no transverse variation of fields (influences slice emittance) overestimates longitudinal field overestimates longitudinal field Q distribution frozen Q distribution frozen But: FAST

Benchmarking Results

Energy spread vs. Longitudinal Position along Chicane

Present Strategy to optimise bunch compression systems Optimise with 1-D code Check with 3-D The result will work, but will not necessarily be the optimal solution The quest for fast, self consistent 3-D algorithms continues...

CSR driven Amplification of Beam Intensity Modulations Theoretical Models: Schneidmiller et al (`Klystron Instability´) Stupakov et al Z.Huang and K.-J. Kim Numerical Gain Calculations in 1-D agree quite well with the 1-D theories

= 25  m = 25  m  = 2%  = 10% CSR benchmark chicane (Berlin CSR Workshop, Jan. 2002) P. Emma  x  1  m  E /E 0  2  10  6

CSR Micro-bunching: Theory* vs. Tracking * S. Heifets, S. Krinsky, G. Stupakov, SLAC-PUB-9165, March 2002 LCLS BC2  x  1  m  E /E 0  3  10  5  z  195  22  m tracking (P. Emma) theory (S. Heifets, et. al.)

CSR driven Instabilities, starting from shot noise? Need to complete gain calculations. We set up a benchmark example in Zeuthen and will be comparing the results in the Sardinia workshop in July. Discuss how to fold gains with a proper model for shot noise

i = 20  m i = 20  m  x0 =1  m   =2  10  5 Vary ‘slice’ emittance and energy spread  x0 =0  m   =2  10  6  x0 =1  m   =2  10  6

CSR Microbunching Gain vs. “theory”: S. Heifets et al., SLAC-PUB-9165, 2002 Initial modulation wavelength prior to compressor Microbunching Gain ‘cold’ beam  x =1  m  x =1  m,   =3  10  5 see also E. Saldin, Jan. 02, and Z. Huang, April 02

Estimated Gain of All LCLS Bends Wiggler off Wiggler on SC wiggler suppresses a short-wavelength, high-gain peak Z. Huang Multiply by 5 for wavelength at gun

Comments on Initial Bunching From shot noise with a gain less than 100, this should be a small effect From bunch structure If spike width less than wavelength  How big? Watch out for numerical noise in simulations!

Daresbury:WG3 Comments (P. Emma) CSR is a major limitation for bright e  beams 1D codes miss some physics (e.g., Elegant)1D codes miss some physics (e.g., Elegant) 3D codes take too long and user UN-friendly3D codes take too long and user UN-friendly Desperate need of fast, reliable, friendly codeDesperate need of fast, reliable, friendly code Need more measurementsNeed more measurements More clever BC designs very welcomeMore clever BC designs very welcome Machine jitter/drift needs more consideration Integrated machine design can reduce sensitivitiesIntegrated machine design can reduce sensitivities Stability simulations helpfulStability simulations helpful Feedback systems planned in advanceFeedback systems planned in advance Bunch charge Trajectory Energy at each stage Bunch length ? Beam diagnostics & tuning algorithms should be integral part of design, not an after-thought Thanks