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SLAC Computer Building (Bldg 50, Room 115), SLAC Thursday, January 24, 2008

BLM Calibration— LCLS Undulator Radiation Loss Simulations with MARS. Jeff Dooling Argonne National Laboratory. SLAC Computer Building (Bldg 50, Room 115), SLAC Thursday, January 24, 2008. Outline. Simulation Tasks Modeling with MARS Status. Tasks.

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SLAC Computer Building (Bldg 50, Room 115), SLAC Thursday, January 24, 2008

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  1. BLM Calibration— LCLS Undulator Radiation Loss Simulations with MARS Jeff Dooling Argonne National Laboratory SLAC Computer Building (Bldg 50, Room 115), SLAC Thursday, January 24, 2008

  2. Outline • Simulation Tasks • Modeling with MARS • Status

  3. Tasks • 1a) Complete first undulator geometry in MARS • 1b) Full undulator geometry with quad fields • 2) Use equivalent 1-mm Al foil to initiate shower for calibration. Begin with foil 30 m upstream. • 3)Beam offsets • xo=30 mm, yo=0 • xo=0, yo=30 mm • xo=30 mm, yo=30 mm • 4) Direct beam strike on chamber walls

  4. Tasks, con’t • 5) Calibration for tests at ANL—loss scenarios • a) Touschek—single electron (linear, but random), loss rate known • b) Injection—104 e/m (mainly linear, deterministic), losses known • c) Dump (1010 e/m highly saturated)

  5. Task—Calibration, APS SR Injection losses S4 Cerenkov detector[1] signal during Top-Up injection S3 beamline removed; S4, smallest aperture —40% of inj loss [2] zooming Losses occur for several ms Losses occur on each cycle around the SR

  6. Modeling with MARS—Simulation considerations • Keep STEPEM~0.1tmin, where t is the smallest linear size of the smallest region (for example, beam pipe wall thickness 0.05 mm; therefore STEPEM=0.005 cm) • KILLPTCL (sub)—keep or throw away primary electrons (for example, with primary energy Eo, discard all particles with energies above Eo-DE where DE>Dpc)

  7. Simulation considerations, con’t • MIXTUR (sub)—define special mixtures such as vanadium permendur and its combination with magnets (NdFeB). • SUFI and FIELD (sub)—used to read in magnetic field maps for the quadrupoles

  8. Magnet and Pole material • Undulator volume mixture of magnet and pole material • Magnet: NdFeB—mixture: 6% B, 82% Fe, and 12% Nd [MARS Manual] (~Nd3Fe53B20) • Poles: Vanadium Permendur (VP)—mixture: 2% V, 49% Fe, 49% Co [3] (~V2Fe45Co43)

  9. 2-D Quad Field profiles from OPERA Field maps courtesy of M. Jaski

  10. Zooming in on beam region Outside linear (beam) region, fields are complex and non-focusing

  11. Adding a pole “foam” region adjacent to the beamline Y-Z undulator cross section beam pipe OD: 0.300 cm magnet height: 0.338 cm pole height: 0.390 cm Mechanical drawings courtesy of S. Doran and R. Keithley

  12. Simulation stats on the APS weed cluster running MARS (MPI) for single undulator, no B fields • 10 proc., 106 primary particles, w/ enh., 13 min. • 8 proc., 107 primary particles, w/ enh., 118 min. • 24 proc., 107 pri. part., no enh., 44 min. (2*) • 24 proc., 107 pri. part., w/ enh., 44 min.* Ave. speed: 9.4x103 pp-und/proc./min Approx. 300 proc. available on weed of which 250 can be requested a by single user *varied seed

  13. Simulation geometries, single undulator x-y view at z=25 cm y-z view at x=0 cm

  14. MARS geometry x-y view at z=25 cm, zoom x-y view at z=13.5 cm, radiator

  15. Preliminary results 10E7Al foil 30 m upstream electron flux neutron flux

  16. Radiator e-spectra with and without enhancer with W enhancer without W enhancer

  17. Status and Goals • Task 1a) 1st undulator geometry in MARS—initially early Jan 08; accomplished now • Task 1b) Full geometry with fields—15Feb08 • Task 2—29Feb08 • Task 3—15Mar08 • Tasks 4 and on—must be negotiated

  18. Final thought Work quickly, but don’t hurry. —John Wooten

  19. References • A. Pietryla, W. Berg, R. Merl, Proc. PAC01, Chicago, IL, http://accelconf.web.cern.ch/AccelConf/p01/PAPERS/TPAH304.pdf 2. M. Borland and L. Emery, Proc. PAC05, Knoxville, TN, http://ieeexplore.ieee.org/iel5/10603/33511/01591640.pdf; updated by private communication with L. Emery 14Jan08 • R. E. Burket and D. M. Stewart, J. Appl. Phys. 33, 1224 (1962).

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