1 / 17

Using Tune Shifts to Evaluate Electron Cloud Effects on Beam Dynamics at CesrTA

Using Tune Shifts to Evaluate Electron Cloud Effects on Beam Dynamics at CesrTA. Jennifer Chu Mentors: Dr. David Kreinick and Dr. Gerry Dugan. Outline. Review of Electron Clouds and Tune Shifts Simulations of New Data Varying the Simulation Parameters. Electron Clouds.

abiba
Télécharger la présentation

Using Tune Shifts to Evaluate Electron Cloud Effects on Beam Dynamics at CesrTA

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Using Tune Shifts to Evaluate Electron Cloud Effects on Beam Dynamics at CesrTA Jennifer Chu Mentors: Dr. David Kreinick and Dr. Gerry Dugan REU Final Presentation

  2. Outline • Review of Electron Clouds and Tune Shifts • Simulations of New Data • Varying the Simulation Parameters REU Final Presentation

  3. Electron Clouds • ILC will collide electrons and positrons • Accelerating charges radiate • Photons knock electrons off walls of beampipe • Photoelectrons are accelerated by beam and knock off more electrons, forming a cloud • Electrons in the cloud are attracted to positive beams REU Final Presentation

  4. Tune Shifts • Beams are displaced from nominal path • Tune (Q): number of oscillations of a particle about nominal path, per turn around the ring • Tune shift (ΔQ): difference in tune caused by electric field of electron cloud Qy = 9.52 REU Final Presentation

  5. Taking Data • CesrTA is used to measure tune shifts • Beams are set into oscillation • BPMs measure the position for 2048 turns • Fourier transform is used to calculate tune shifts REU Final Presentation

  6. POSINST • POSINST is a simulation code used to model the electron cloud effects • Simulations are run for different values for each of five parameters which describe the physics of electron cloud generation • Simulations are compared to data to test accuracy of the model REU Final Presentation

  7. Comparing Data to Simulations REU Final Presentation

  8. Goals • We want to find the optimal set of parameters that most accurately models electron clouds • The simulation can then be used to predict the behavior of electron clouds in damping rings of future linear colliders REU Final Presentation

  9. Submitting Jobs to the Queue • Simulations were run on Cornell’s batch nodes • Each job is only allowed 48 hours of CPU time • I wrote code to parallel process the simulations to get more statistics I monopolized the queues for the summer: 87 data sets x 5 simulation parameters x 2 for x, y tune shifts x 6 jobs per submission ----------------------------------- > 5000 total jobs REU Final Presentation

  10. Calculating Tune Shifts • I used Mathematica to post-process the results of POSINST to calculate the tune shifts • I superimposed the tune shifts from multiple simulations onto plots of the data for comparison REU Final Presentation

  11. June 2011 Coherent Tune Shift Data • 2.085 GeV e+: 20 x 0.5 mA • 2.085 GeV e+: 45 x 0.5, 1.0, 1.5, 2.0mA • 4.00 GeV e+: 20 x 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0 mA • 4.00 GeV e+: 45 x 0.2, 0.4, 0.6, 0.8, 1.0, 1.2 mA • 5.3 GeV e+: 20 x 0.5, 1.0, 2.0 mA • 5.3 GeV e-: 20 x 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0 mA • 5.3 GeV e+: 45 x 0.2, 0.4, 0.6, 0.8, 1.0, 1.2 mA • 5.3 GeV e-: 45 x 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6 mA Bunch spacing studies: • 2.085 GeV e-: 30 x 0.2, 0.4, 0.6, 0.8, 1.0, 1.2 mA for 12, 16, 20 ns spacing • 2.085 GeV e-: 45 x 0.2, 0.4, 0.6, 0.8, 1.0, 1.2 mA for 4, 8, 12 ns spacing REU Final Presentation

  12. 2.1 GeV 4.0 GeV 5.3 GeV 0.50 mA/bunch 0.40 mA/bunch 0.50 mA/bunch 1.00 mA/bunch 1.00 mA/bunch 1.00 mA/bunch REU Final Presentation

  13. Simulation Parameters • Parameters describe the physics of electron cloud generation • When a radiated photon from the beam knocks into the wall of the beampipe, photoelectrons are generated • (1) Quantum Efficiency: number of electrons generated for every photon REU Final Presentation

  14. Secondary Emission • Photoelectrons are accelerated by the electric field of the beam and continue to produce more electrons • (2) Secondary Emission Yield (SEY): number of secondary electrons generated for every primary electron • (3) Energy at the SEY Peak REU Final Presentation

  15. Types of Secondary Electrons • When a photoelectron hits a wall of the vacuum chamber, it can: • Bounce off (elastic) • Interact with material (rediffused) • Knock off electrons in material (true) • (4) Fraction of Secondaries that are Rediffused • (5) Fraction of Secondaries that are Elastic Sketch of the currents that are used to define the different components of secondary emission. Figure taken from M. Furman and G. Lambertson, “The electron-cloud instability in the arcs of the PEP-II positron ring” REU Final Presentation

  16. Varying the Simulation Parameters REU Final Presentation

  17. Summary • Tune shifts are used to study electron clouds • Simulations were run and compared to data for all five parameters and all 77 new data sets • Model seems to work reasonably well for a variety of beam energies and bunch currents • Finding the optimal parameters will allow the model to be used for future linear colliders REU Final Presentation

More Related