Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY Dark Current Transport at FLASH Start-to-end tracking simulation analysis of beam and dark current transport full 3D aperture model Dark current losses identification of hot spots cleaning efficiency of gun and BC2 collimators influence of new gun layout

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY Simulation Steps Astra simulation of FLASH linac (gun—dump) space charge up to BC2 entrance no apertures 2500 phase space dumps (one each 10 cm, ~30 GB) runtime: ~2 h (44 processors, particles) Aperture check with ApertureLib toolkit full 3D model of the accelerator aperture in cartesian coordinates outputs: phase space at any position, discarded particles, Twiss parameters,... runtime: ~14 min

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY 1: Machine Model

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY Design Optics

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY “Dispersion”

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY Aperture Model (1) AutoCAD DXF file included pre-built aperture elements Astra aperture file

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY Aperture Model (1) AutoCAD DXF file included pre-built aperture elements Astra aperture file

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY Aperture Model (2)

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY Aperture Model (3)

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY 2: Dark Current

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY Dark Current Simulation Dark current emission: Simple field emission model Current: Gaussian around RF gun phase 0° with  =16° Homogeneous emission from cathode surface (Ø 5 mm) Current exiting the gun 200–300 µA no simulation of collective effects (space charge, CSR,... negligible)

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY Dark Current Losses (1) ACC1 exit BC2 entrance BC3 entrance BC3 exit transverse collimators energy collimators

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY Dark Current Losses (1) ACC1 exit BC2 entrance BC3 entrance BC3 exit transverse collimators energy collimators

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY Dark Current Losses (2)

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY Darkcurrent Losses (3)

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY Longitudinal Profile (GUN)

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY Longitudinal Profile (ACC1)

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY Transverse Beam Size

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY 3: Counter Measures

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY BC2+Gun Collimators BC2 collimator Gun collimator

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY Horizontal Profiles (in front of undulator entrance)

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY Vertical Profiles (in front of undulator entrance)

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY Longitudinal Phase Space (in front of undulator entrance)

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY Dark Current Transmission Relative dc amount 100% 30% 22% 6% 100% 18% 78% 15%

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY Beam Losses at 8DBC2 darkcurrent dumped on valve 100% 65% 64% 44% Simulation 100% 30% 22% 6% Measurement 100% 65% 64% 44%

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY New Gun Layout ?

Beam dynamics meeting, 2007/05/14Lars Fröhlich, MPY Conclusion More work needed on simulation (finer step size -> include ApertureLib into Astra?) Measurements needed A usable gun collimator will reduce the activation of BC2 components considerably