IPAC2012 - List of Authors (Dooling, J.C.)

Paper	Title	Page
MOEPPB013	Simulation and Measurement of Beam Loss in the Narrow-Gap Undulator Straight Section of the Advanced Photon Source Storage Ring	106
	J.C. Dooling, M. Borland ANL, Argonne, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract number DE-AC02-06CH11357. Simulations indicate the removal of a scraper/collimator in the Sector 37 straight section (SS) of the Advanced Photon Source storage ring (SR) results in increased beam loss in the remaining narrow-gap, insertion device SS, ID4. Modeling with elegant provides loss distributions in the 5-mm aperture vacuum chamber of ID4 and includes the effects of rf system muting and quantum excitation in the bunch. The loss distributions are then used as input to a MARS model of the SS that includes undulator geometry. ID4 has been instrumented with additional monitoring to capture beam loss events, particularly beam dumps. Cerenkov detectors and fiber-optic cable bundles are used to capture temporal profiles of beam loss events. Beam dumps deliver 2600 J to the vacuum chamber and surrounding hardware including undulators. Data indicate a variety of temporal profiles occur during the beam dumps, with the shortest lasting 6 microseconds, FWHM (<2 turns). Such high power and power densities can lead to physical damage of vacuum components if not handled correctly. Touschek scattering loss is also a concern for undulator demagnetization. Comparison of modeling and measurements will be presented.

WEPPP072	Beam Characterization and Coherent Optical Transition Radiation Studies at the Advanced Photon Source Linac	2876
	J.C. Dooling, R.R. Lindberg, N. Sereno, C.-X. Wang ANL, Argonne, USA A.H. Lumpkin Fermilab, Batavia, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract number DE-AC02-06CH11357. The Advanced Photon Source facility includes a 450-MeV S-band linac with the option for injection from a photocathode (PC) rf gun. A diode-pumped, twice-frequency doubled Nd:glass regen laser (263 nm) is used with the Cu PC to generate the electron beams. Characterization of these beams and studies of the microbunching instability following beam compression in the four-dipole magnetic chicane are described. A suite of diagnostics is employed including a three-screen emittance section, a FIR coherent transition radiation autocorrelator, electron spectrometers, and an optical diagnostics end station. An energy chirp impressed on the beam is used to compress the 1-2 ps, rms bunch as it passes through the chicane. With compression, bunch lengths of 170-200 fs, rms at 450 pC are measured, and coherent optical transition radiation (COTR) due to the microbunching instability is observed. Mitigation techniques of the COTR in the beam profile diagnostics are demonstrated both spectrally and temporally. At 100 pC without compression normalized transverse emittances of 1.8 and 2.7 microns are observed in the x and y planes, in reasonable agreement with initial ASTRA simulations.

Paper

Title

Page

Simulation and Measurement of Beam Loss in the Narrow-Gap Undulator Straight Section of the Advanced Photon Source Storage Ring

106

J.C. Dooling, M. Borland
ANL, Argonne, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract number DE-AC02-06CH11357.
Simulations indicate the removal of a scraper/collimator in the Sector 37 straight section (SS) of the Advanced Photon Source storage ring (SR) results in increased beam loss in the remaining narrow-gap, insertion device SS, ID4. Modeling with elegant provides loss distributions in the 5-mm aperture vacuum chamber of ID4 and includes the effects of rf system muting and quantum excitation in the bunch. The loss distributions are then used as input to a MARS model of the SS that includes undulator geometry. ID4 has been instrumented with additional monitoring to capture beam loss events, particularly beam dumps. Cerenkov detectors and fiber-optic cable bundles are used to capture temporal profiles of beam loss events. Beam dumps deliver 2600 J to the vacuum chamber and surrounding hardware including undulators. Data indicate a variety of temporal profiles occur during the beam dumps, with the shortest lasting 6 microseconds, FWHM (<2 turns). Such high power and power densities can lead to physical damage of vacuum components if not handled correctly. Touschek scattering loss is also a concern for undulator demagnetization. Comparison of modeling and measurements will be presented.

WEPPP072

Beam Characterization and Coherent Optical Transition Radiation Studies at the Advanced Photon Source Linac

2876

J.C. Dooling, R.R. Lindberg, N. Sereno, C.-X. Wang
ANL, Argonne, USA
A.H. Lumpkin
Fermilab, Batavia, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract number DE-AC02-06CH11357.
The Advanced Photon Source facility includes a 450-MeV S-band linac with the option for injection from a photocathode (PC) rf gun. A diode-pumped, twice-frequency doubled Nd:glass regen laser (263 nm) is used with the Cu PC to generate the electron beams. Characterization of these beams and studies of the microbunching instability following beam compression in the four-dipole magnetic chicane are described. A suite of diagnostics is employed including a three-screen emittance section, a FIR coherent transition radiation autocorrelator, electron spectrometers, and an optical diagnostics end station. An energy chirp impressed on the beam is used to compress the 1-2 ps, rms bunch as it passes through the chicane. With compression, bunch lengths of 170-200 fs, rms at 450 pC are measured, and coherent optical transition radiation (COTR) due to the microbunching instability is observed. Mitigation techniques of the COTR in the beam profile diagnostics are demonstrated both spectrally and temporally. At 100 pC without compression normalized transverse emittances of 1.8 and 2.7 microns are observed in the x and y planes, in reasonable agreement with initial ASTRA simulations.