Applying Wakes to Energy Compressor
Posted: 20 Aug 2020, 12:31
Hello,
This is my first time using elegant. I am attempting to model an energy compression system consisting of a magnetic chicane and a linear accelerator. I am using the TWLA element to model the accelerator followed by WAKE, TRWAKE elements to model the wakes of the TWLA. I have simulated my structure using shorter and shorter bunches and have found the structure's longitudinal and transverse wake functions are reasonably approximated by Bane's analytic equations:
where a, s_1, s_2 are based on the geometry of the structure.
1) For my accelerator geometry, the Bane's approximation equations are valid up to z=5mm (1.67e-11 sec) behind the charge that excites the wake. The bunch entering the accelerator is 17mm (5.67e-11 sec) long. Should I make my wake function input file zero for all times greater than t=1.67e-11 sec? If I don't set the wake function to zero after t=1.67e-11 sec, does Elegant apply an energy change to the tail of the beam that it should not (is not physical)? Does this upper limit of the approximation not matter if my simulated wakepotentials for short bunches follows the approximation further out than the upper limit of the analytic function?
2) The TRWAKE element include options to scale the transverse wake functions by the the beta functions of the accelerator. Will I need to compute the beta functions near my accelerating structure and use those values for xfactor, yfactor or is that only for special cases?
Thank you,
Evan
This is my first time using elegant. I am attempting to model an energy compression system consisting of a magnetic chicane and a linear accelerator. I am using the TWLA element to model the accelerator followed by WAKE, TRWAKE elements to model the wakes of the TWLA. I have simulated my structure using shorter and shorter bunches and have found the structure's longitudinal and transverse wake functions are reasonably approximated by Bane's analytic equations:
where a, s_1, s_2 are based on the geometry of the structure.
1) For my accelerator geometry, the Bane's approximation equations are valid up to z=5mm (1.67e-11 sec) behind the charge that excites the wake. The bunch entering the accelerator is 17mm (5.67e-11 sec) long. Should I make my wake function input file zero for all times greater than t=1.67e-11 sec? If I don't set the wake function to zero after t=1.67e-11 sec, does Elegant apply an energy change to the tail of the beam that it should not (is not physical)? Does this upper limit of the approximation not matter if my simulated wakepotentials for short bunches follows the approximation further out than the upper limit of the analytic function?
2) The TRWAKE element include options to scale the transverse wake functions by the the beta functions of the accelerator. Will I need to compute the beta functions near my accelerating structure and use those values for xfactor, yfactor or is that only for special cases?
Thank you,
Evan