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Using Realistic Photon Spectra Mike Jenkins Lancaster University and The Cockcroft Institute

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Presentation Overview Realistic undulator spectra Results from PPS-SIM comparing realistic and ideal spectra Update on work on going at Lancaster University Physics Department 2September 2011LWCS 2011 Granada

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‘Realistic’ Undulator Spectra Current simulations for the undulator based positron source use an ideal photon spectra The magnetic field of the 4m ILC undulator prototype constructed at Rutherford Appleton Laboratory has been mapped Using this field map and the ILC RDR Parameters ‘realistic’ photon spectra have been generated David Newton (University of Liverpool and the Cockcroft Institute) and Duncan Scott (Cockcroft Institute now at Fermilab) have both produced spectra 3September 2011LCWS 2011 Granada Reference: D. Newton, The rapid calculation of synchrotron radiation from long undulator systems, IPAC10

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Spectra Parameters NewtonScott e - Energy (GeV)150 Length of Undulator (m)1084 K value0.92 Field MapAnalyticalMeasured e - energy spread (GeV)0.000110.005 γ per e - per m1.190Unknown Helicity InformationYesNot Yet Aperture SizeRadius 0.05mm5mm x 5mm Distance to Aperture (m)5501.767 September 2011LCWS 2011 Granada For Ideal Spectral γ per e - per m is 1.9039 from SLAC Pub LCC-0095 by J. Sheppard

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5September 2011IWLC 2011 Granada Tracking through Field Maps Taken from Synchrotron Radiation Output from the ILC undulator talk by D. Newton at ILC Positron Source Workshop 2010

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These plots are for one of the 2m undulator prototypes constructed at RAL One shows the power radiated at the end and the other shows the trajectory through the undulator in x and y for a beam that enters at an angle The angular deviations off axis are of the order 1 μrad which when compared with k/γ (3.13 μrad for a drive beam energy of 150 GeV) are significant 6September 2011IWLC 2011 Granada

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David Newton’s Spectra 7September 2011LCWS 2011 Granada Newton_L is the left handed photon spectrum, Newton_R is the right handed photon spectrum and Newton is the overall photon spectrum

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Spectra 8September 2011LCWS 2011 Granada

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Spectra 9September 2011LCWS 2011 Granada

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PPS-SIM PPS-SIM is a code developed at DESY that utilizes Geant4 to simulate the ILC positron source http://pps-sim.desy.de PPS-SIM has the ‘ideal’ (Kincaid 76) undulator spectrum implemented within it PPS-SIM currently simulates from the undulator to the first Capture RF cavity 10September 2011IWLC 2011 Granada Schematic of ILC RDR Positron Source

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Initial simulations have been carried out with the three realistic spectra The simulations have been carried out using a RDR like source design optimized for the ‘ideal’ spectrum The angular spectra has been replaced by a uniform distribution between 0 and 6.8 x 10 -6 radians IdealNewton Number of e + per e - at end of source0.0440.024 Number of e + per e - in DR acceptance0.0130.007 e + polarization35.9%52.6% (?) Preliminary PPS-SIM Results September 2011LCWS 2011 Granada11

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Preliminary PPS-SIM Results September 2011LCWS2011 Granada12 IdealNewton Scott5 Plots showing number of e + at the end of the simulation: hE is total number hElc is number within longitudinal DR acceptance hEltc is number within longitudinal and transverse DR acceptance

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Preliminary PPS-SIM Results 13September 2011IWLC 2011 Granada IdealNewton Scott5 Plots showing e + emittance at the end of the simulation, the red line is the transverse damping ring acceptance

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Preliminary PPS-SIM Results Areas to be investigated and optimized include: Polarization Collimation Angular dependence Capture RF 14September 2011LCWS2011 Granada

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Update on work at Lancaster University Physics Department Final analysis of DL target prototype data including conductivity measurements of target material. Aim to publish paper summarising results. Arrange for shipping of target wheel to LLNL. Assisting with development of PPS-Sim. Continuing related work on beam depolarisation simulations. 15September 2011IWLC 2011 Granada

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Summary Differences in shapes of the spectra to be investigated Still working on normalizing Duncan Scott’s spectra to per e - More work to be done to check polarization and to optimise the source Investigate deliberately misaligning the undulator modules to reduce PEDD on the collimator and target Intention is to expand simulations to cover latest ILC parameter sets and also CLiC 16September 2011LCWS 2011 Granada

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