csrImpedance & ZLONGIT

[Najmeh]

Dear All

I  am trying to show the effects of the CSR on e-beam in an Arc. I used the "csrImpedance" and made the steady-state CSR impedance. And then by "ZLONGIT" I added this Impedance to the code. After each bending I use this Impedance.

for example, for each bending, I have :

"CSRSH_AR1":ZLONGIT,zreal="csr_AR1.sdds=f+ZReal", zimag="csr_AR1.sdds=f+ZImag",interpolate=1,bin_size=0

"AR1_B1S01B": CSRCSBEND,L=4.001828,ANGLE=-0.05235986879,E2=-0.05235987756, &
  TILT=1.570796327,HGAP=0.01905, n_kicks=15,nonlinear=1,derbenev_criterion_mode="evaluate", &
INTEGRATION_ORDER=4,BINS="nbins_csr",SG_HALFWIDTH=1,SGDERIV_HALFWIDTH=1, &
ISR=1,CSR=1,HIGH_FREQUENCY_CUTOFF0=0.25,HIGH_FREQUENCY_CUTOFF1=0.3

"AR1_B1S01": LINE=(AR1_B1S01B, CSRSH_AR1)
----------
In arc, I have 8 bending magnets, so I did same fore each one. I attached the lattice file.
The "csr_AR1.sdds" was made by  csrImpedance.
I hope, I am going in correct direction.

I want to ask about  csrImpedance.
1- filter
When I changed the cutoff1,cutoff2 in filter I had different results. I don't know how I select these values. When I removed the filter,  I found good result.
I was wondering, if I could ignore this filter in csrImpedance.
2- maximum frequency
The bunch length is 333 fs, as it was suggested in manual I considered maximum frequency much greater than 1∕(2πσt), but it made a problem. I had following errors:
"If using broad-band impedance, you should increase the number of bins (or use auto-scaling) and rerun" (Actually it is auto-scaling and increasing nbin did not remove the error )
"If using file-based impedance, you should increase the number of data points or decrease the frequency resolution." (I did it but no change)
and this error:
"error: impedance spectrum has non-zero imaginary DC term (ZLONGIT)"
and following warning:
" Using 1-D CSR formalism but Derbenev criterion not satisfied (1.120180e-01 > 0.1)."


I appreciate any help you can give me with these errors and  cutoff1,cutoff2 in filter .

Best regards,
Najmeh

[michael_borland]

Najmeh,

Sorry for the long delay in replying.

I think the advice in the csrImpedance manual to set the maximum frequency to much greater than 1/(2*pi*sigmat) is wrong. I would set it to much greater than 1/sigmat. I'll fix the manual.

I've attached an example that shows use of csrImpedance/ZLONGIT and CSRCSBEND to get close to the same results. Hope this helps.

--Michael

[Najmeh]

Many thanks Michael,
Indeed, I want elegant also calculates the ISR effect on e-beam. So I changed your lattice. I added "CSBEND" to show the effect of ISR and bending field on e-beam, then applied " zlongit" to calculate the effect of the shielding. Please look at following code :
--------------------------------------
q: charge,total=10e-9
csrz: zlongit,zreal="csrZ.sdds=f+ZReal",zimag="csrZ.sdds=f+ZImag",interpolate=1

b2: CSBEND,l=0.1,angle=0.01,e1=0,e2=0, n_kicks=100, ISR=1

b1: csrcsbend,steady_state=1,l=0.1,angle=0.01,e1=0,e2=0,bins=80,n_kicks=100,sg_halfwidth=4,&
high_frequency_cutoff0=0.2,high_frequency_cutoff1=0.25, ISR=1

blz: line=(q,b2,csrz)
blb: line=(q,b1)

----------------------------------------------
Is it correct ?

Many thanks for any advice,
Best regards,
Najmeh