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

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

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

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

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

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

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

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 2673.78 2 4310.44 3 8921.18 4 64849.16 5 -14151.13 6 -7075.44 7 -5233.67 8 -4267.83 8/11/2016 JLEIC Accelerator R&D Meeting

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

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

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

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