1 / 6

Understanding Longitudinal Motion and RF Manipulations in Particle Accelerators

This lecture explores the principles of longitudinal motion in particle accelerators, focusing on RF manipulations. It covers the significance of phase angles at cavity arrivals, synchrotron tunes, and energy gain from RF cavities. The discussion includes strategies for adjusting RF phases between cavity groups to optimize acceleration and enhance beam capture with minimal dispersion. Additionally, it highlights the importance of frequency transitions during bunch shortening, showcasing techniques for adiabatic voltage changes to maintain bunch coherence in phase space.

zora
Télécharger la présentation

Understanding Longitudinal Motion and RF Manipulations in Particle Accelerators

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. Longitudinal Motion 2 Eric Prebys, FNAL

  2. RF Manipulations RF1 RF2 RF3 RF3 fi is the phase angle at the arrival of the particle at cavity i Lecture 9 - Longitudinal Motion 2 As you’ll show in homework, the synchrotron tune (longitudinal oscillations/turn) is generally <<1. That means that if there are multiple RF cavities around the ring, the orbiting particle will see the vector sum of the cavities. We will clearly get the maximum energy gain if all phases are the same, so (assuming all voltages are the same)

  3. Do we always want the maximum acceleration? Like “turning RF off” Lecture 9 - Longitudinal Motion 2 As we’ll see, there are times when we want to change the amplitude of the RF quickly. Because cavities represent stored energy, changing their amplitude quickly can be difficult. Much quicker to change phase Standard technique is to divide RF cavities into two groups and adjust the relative phase. In the simplest case, we put half the RF cavities into group “A” and half into group “B”. We can adjust the phases of these cavities relative to our nominal synchronous phase as So

  4. RF capture Lecture 9 - Longitudinal Motion 2 We can capture beam by increasing the RF voltage with no accelerating phase As we accelerate beam, Dt decreases. Recall So as beam accelerates, bunches get narrower

  5. Bucket to Bucket Transfer 800 MHz Linac 200 MHz Linac Transfer beam to every 4th bucket Lecture 9 - Longitudinal Motion 2 In general, the accelerating gradient of an RF structure is So when bunches get short enough, it’s advantageous to transfer to a higher frequency. For example, in the Fermilab Linac

  6. Bunch Rotation Lecture 9 - Longitudinal Motion 2 If we slowly change the RF voltage (or effective voltage by phasing), we can adiabatically change the bunch shape If we suddenly change the voltage, then the bunch will be mismatched and will rotate in longitudinal phase space

More Related