Space charge set up

This operation sets up the parameters to compute the effect of space on particle tracking. Presently only a gaussian distribution is used, though the provision of other distribution is possible. The space charge remains in effect for all the operations that use tracking. (eg: rmat, movement analysis tracking etc.).

The program uses one reference particle that is situated at a user chosen sigma in the space charge distribution. At regular intervals the program checks the approximate linear motion traced by this particle.

This operation MUST ALWAYS be preceded by a MACHine operation providing the list of the twiss parameters at every point of the lattice, and by a REFErence orbit run, and a Constant definition changing the mass of the particle to that of the particle for which the space charge computation is done.

Input format 


SPACe charge set up.....(maximum 80 characters) 


Option chkturn sigma nturn energy epsilonx epsilony delta lambda

Parameter definitions

option $\parbox{10cm}{ option number presently not used }$

chkturn $\parbox{10cm}{ number of turns after which the space charge distrib... ...ed in evey tracking operation. It is placed last in the sequence of particles}$

sigma $\parbox{10cm}{ the number of sigmas within the gaussian space charg... ... distribution if the the motion of the reference particle is relatively smooth}$

nturn $\parbox{10cm}{ the number of turns the setup routine will track the... ...so that an equilibrium has been reached for the emittance of the distribution.}$

energy $\parbox{10cm}{ The reference energy in GeV for which the space charge distribution kicks are computed}$

epsilonx (y) $\parbox{10cm}{ the one sigma emittance of the gaussian beam distrib... ... distribution at every point in the ring and to locate the reference particle}$

delta $\parbox{10cm}{ the relative energy deviation for which the space computation are done}$

lambda $\parbox{10cm}{ The linear charge density in Coulombs per meter }$

Examples

The example is taken from demo9. It is given together with the operations that must precede it. This operation requires caution in the interpretation of the results.

CONSTANT DEF
12 1 3 0.938259,
output
0,
REFERENCE
12 0.002 0.002
0 0 0 0 0 0
0,
output
3,
set symplectic on
1 0.5,
space charge set up
* new input structure
1 80 2 80 0.45 15 15 0 2.981e-8,
* slightly reduced linear density to avoid error on movement analysis
*1 80 2 80 0.45 15 15 0 1.000e-8,
* old input structure
*1 80 0.45 60 60 0 2.981e-8,
*stop
*1 80 0.45 60 60 0 1.0e-8,
GEOM
1.661 0 14.792 0.0002
0 0 0 0 0
2 320 1
1 -1
1 1
60 60
;
stop