PowerPoint Presentation

PTC-ORBIT issues for PSB simulations

V. Forte E. Benedetto M. Martini

S.c. meeting (18/07/2013)

PTC-ORBIT issues for PSB simulations - V. Forte E. Benedetto M. Martini - S.c. meeting (18/07/2013)OUTLINE

We observed different strange behaviours in PTC-ORBIT simulations that should be fixed or, at least, explained by the code developers:

Acceleration issues RF issuesAperture related spikesNo-coincidence (and coincidence) of solutions

PTC-ORBIT issues for PSB simulations - V. Forte E. Benedetto M. Martini - S.c. meeting (18/07/2013)Acceleration issues: Orbit seems to not recognize the acceleration imposed through PTC RF tables

showaccelerate(fio)PTC-ORBIT issues for PSB simulations - V. Forte E. Benedetto M. Martini - S.c. meeting (18/07/2013)

The energy path described in the table is the followingPTC-ORBIT issues for PSB simulations - V. Forte E. Benedetto M. Martini - S.c. meeting (18/07/2013)Acceleration issues:

ORBIT diagnosticsStatistical Twiss + dynamic energy (from RF table)Fixed Twiss (from Twiss PTC table) + dynamic energy (from RF table)Fixed Twiss (from Twiss PTC table) + static energy (160 MeV)Orbit seems to not recognize the acceleration imposed through PTC RF tables

The Orbit diagnostics confirm the hypothesis. In fact these are similar to post-processing calculations using fixed Twiss and a constant 160 MeV kinetic energy

Horizontal RMS emittanceVertical RMS emittancePTC-ORBIT issues for PSB simulations - V. Forte E. Benedetto M. Martini - S.c. meeting (18/07/2013)Acceleration issues: Orbit seems to not recognize the acceleration imposed through PTC RF tables

This can cause problems in:

Diagnostics (Dp/p calculation)Space charge computation

MUST BE FIXED!PTC-ORBIT issues for PSB simulations - V. Forte E. Benedetto M. Martini - S.c. meeting (18/07/2013)RF table definition:

In case of acceleration (Bdot 0), the longitudinal phase space is (artificially?!) shifted by PTC in order to use f=0 as a fixed point. While, without acceleration, this is a direct consequence of the equations (0 stable phase), it shouldnt be in case with acceleration.

8 kV (h=1) + 8 kV (h=2) in phase without acceleration

PTC-ORBIT issues for PSB simulations - V. Forte E. Benedetto M. Martini - S.c. meeting (18/07/2013)The +time command must be used for space charge simulations and causes a shift of p in phase.

8 kV (h=1) + 8 kV (h=2) in phase without acceleration (swapped sign in PTC-ORBIT)

PTC-ORBIT issues for PSB simulations - V. Forte E. Benedetto M. Martini - S.c. meeting (18/07/2013)For this reason the sign of the voltages must be swapped.8 (h=1) & 8 (h=2) in phase -> -8, -8

8 kV (h=1) + 8 kV (h=2) in phase with acceleration

PTC-ORBIT issues for PSB simulations - V. Forte E. Benedetto M. Martini - S.c. meeting (18/07/2013)For this reason the sign of the voltages must be swapped8 (h=1) & 8 (h=2) in antiphase -> -8, +88 (h=1) & 8 (h=2) in phase -> -8, -8

8 kV (h=1) + 6 kV (h=2) in phase with acceleration

PTC-ORBIT issues for PSB simulations - V. Forte E. Benedetto M. Martini - S.c. meeting (18/07/2013)

8 kV (h=1) + 8 kV (h=2) in antiphase without accelerationSFP @ 1.047 rad ~ 60 degSynch.period ~ 482 turnsSynch. period ~ 712 turns

PTC-ORBIT issues for PSB simulations - V. Forte E. Benedetto M. Martini - S.c. meeting (18/07/2013)

8 kV (h=1) + 8 kV (h=2) in antiphase with acceleration

SFP @ 1.365 rad ~ 78 degSynch. period ~ 482 turnsSynch. period ~ 780 turnsPTC-ORBIT issues for PSB simulations - V. Forte E. Benedetto M. Martini - S.c. meeting (18/07/2013)The sign of the voltages must be swapped8 (h=1) & 8 (h=2) in antiphase -> -8, +8

8 kV (h=1) + 6 kV (h=2) in antiphase without accelerationSFP @ 0.8568 rad ~ 49 degSynch. period ~ 655 turnsSynch. period ~ 745 turns

PTC-ORBIT issues for PSB simulations - V. Forte E. Benedetto M. Martini - S.c. meeting (18/07/2013)

8 kV (h=1) + 6 kV (h=2) in antiphase with acceleration

PTC-ORBIT issues for PSB simulations - V. Forte E. Benedetto M. Martini - S.c. meeting (18/07/2013)PTC-ORBIT issues for PSB simulations - V. Forte E. Benedetto M. Martini - S.c. meeting (18/07/2013)RF table definition:

In case of acceleration (Bdot 0), the longitudinal phase space is (artificially?!) shifted by PTC in order to use f=0 as a fixed point. While, without acceleration, this is a direct consequence of the equations (0 stable phase), it shouldnt be in case with acceleration -> (0,0) is not a solution of the equations anymore.This can cause problems in:

Defining complex energy paths (i.e. acceleration->static energy) without transition (i.e. from acceleration to static energy) mismatchLongitudinal matching is possible only after single particle tracking to be sure of the bucket position(trick)

The way this shift is performed must be analytically clear!PTC-ORBIT issues for PSB simulations - V. Forte E. Benedetto M. Martini - S.c. meeting (18/07/2013)

Aperture-dependent spikes

PTC-ORBIT issues for PSB simulations - V. Forte E. Benedetto M. Martini - S.c. meeting (18/07/2013)No-coincidence of solutions

PTC-ORBIT issues for PSB simulations - V. Forte E. Benedetto M. Martini - S.c. meeting (18/07/2013)No-coincidence of solutions

PTC-ORBIT issues for PSB simulations - V. Forte E. Benedetto M. Martini - S.c. meeting (18/07/2013)coincidence of solutions (without apertures)

PTC-ORBIT issues for PSB simulations - V. Forte E. Benedetto M. Martini - S.c. meeting (18/07/2013)CONCLUSIONS

We observed different strange behaviours in PTC-ORBIT that should be fixed or, at least, explained by the code developers.Solutions (or explanations) should be provided soon to avoid slacks in simulations.