1. Updates on the beam-beam effect in JLEIC
Edward Nissen
8/11/16

2. JLEIC Accelerator R&D Meeting
Contents
Changed parameter list
Linac v. Synchrotron model
Nonlinear analyses of the current model
8/11/2016
JLEIC Accelerator R&D Meeting

3. JLEIC Accelerator R&D Meeting
Parameter list
A revised set of parameters have been used, based on a COSY Infinity Deck of the JLEIC ion collider ring.
β* from 5cm/2.5cm to 10cm/2cm horiz/vert
εxy from 0.6μm/1.2 μm to 1 μm/.5 μm
Electron spots sized to match
8/11/2016
JLEIC Accelerator R&D Meeting

4. Parameter List (cont’d)
MEIC 2015 report settings
New Parameters
εx (m)
εx (m)
8/11/2016
Turns
JLEIC Accelerator R&D Meeting
Turns

5. Parameter List (cont’d)
εx (m)
8/11/2016
JLEIC Accelerator R&D Meeting
Turns

6. JLEIC Accelerator R&D Meeting
Models used
Two methods of measuring the beam-beam interaction
Guinea Pig- A strong-strong code which uses PIC to model the entire interaction, paired with a simple map for multiturn.
Cosy Infinity – A COSY infinity deck of the ion collider ring has been combined with a beam-beam kick calculated with the Basetti-Erskine formula.
Combination – A code which reads the COSY Infinity maps and uses them to advance the particles with Guinea pig providing the reaction
Current COSY map is non-symplectic.
8/11/2016
JLEIC Accelerator R&D Meeting

7. Linac v. Synchrotron type of motion
In a linac ring system the offsets can be modeled as random, with no correlations.
In a synchrotron, an offset will kick the opposite beam before being smeared out over a larger phase space. This can sometimes lead to an offset in one beam exciting an offset in another beam.
Gear changing complicates the picture greatly. An ion beam will go through O(6000) turns before seeing the same bunch again.
8/11/2016
JLEIC Accelerator R&D Meeting

8. Linac v. Synchrotron type of motion (cont’d)
A rough estimate of the Lyapunov time (not done to full dimensionality)
While gear changing will wipe out much of the information, we are still looking at a hybrid of the linac and synchrotron type of motion
radius (σx)
Lyapunov time (turns) 1 2 3 4 5 6 7 8
8/11/2016
JLEIC Accelerator R&D Meeting

9. JLEIC Accelerator R&D Meeting
Nonlinear Dynamics
4th order map
5th order map
8/11/2016
JLEIC Accelerator R&D Meeting

10. JLEIC Accelerator R&D Meeting
Nonlinear Dynamics
4th order map
Vertical
Horizontal
8/11/2016
JLEIC Accelerator R&D Meeting

11. JLEIC Accelerator R&D Meeting
Nonlinear Dynamics
5th order map
Vertical
Horizontal
8/11/2016
JLEIC Accelerator R&D Meeting

12. JLEIC Accelerator R&D Meeting
Conclusions
A retune is necessary to bring the machine off of the 5th order resonance it currently sits on
Retunes must take both beams into account( i.e. I need a deck for the electron collider)
8/11/2016
JLEIC Accelerator R&D Meeting