Beam instabilties in electron storage ring

[Pradeep]

Can we use Elegant code for Simulation study of resistive wall wake due to narrow vertical gap in undulator? If possible, please help for *.lte, *.ele and relevant wake file etc. as an example of ultra-low emittance storage ring.
Pradeep Kumar

[michael_borland]

Pradeep,

Please see the attached files for an example.

--Michael

[Pradeep]

Dear Dr. Borland,
longRangeWxyz.sdds is the sdds file (file attached) of long range wake due to resistive wall used in the simulation study of collective effects in APS upgrade ring. The file consists of six columns i.e. time, WxDipole, WxQuadrupole, WyDipole, WyQuadrupole and Wz.
What is the dimensions of vacuum chamber and material used to obtain this data? Which computer code has been used to obtain these simulation results?
Pradeep Kumar

[michael_borland]

Pradeep,

The file longRangeWxyz.sdds is for the APS-U vacuum chamber and corresponds roughly to that described in http://accelconf.web.cern.ch/AccelConf/ ... pje078.pdf

It was computed "by hand" by Ryan Lindberg using well-known expressions (e.g., Handbook of Accelerator Physics and Engineering) for resistive wall wakes. We hope in the near future to make this easier with a program that interfaces to elegant, but that isn't available now.

--Michael

[Pradeep]

I want to do simulation study in ultra low emittance ring using transverse bunch by bunch feedback. To understand the simulation, I am using example file of collective effect in APSU ring. I tried to estimate the filter coefficient as shown in lattice.lte file for DRIVER1 and DRIVER2 (file attached) using twiss file but not getting the same data.
I am using the command TFBFirSetup as explained in manual and also in example file mulibunchCollective effect as

TFBFirSetup -twiss Basic.twi -pickup XPICKUP -driver XDRIVER -plane x -output xfb.param -terms 6

TFBFirSetup -twiss Basic.twi -pickup YPICKUP -driver YDRIVER -plane y -output yfb.param -terms 6

Please help me and explain how we get the filter coefficient xfb.param & yfb.param as in lattice.lte file as below

PICKUP1: TFBPICKUP,ID="X-PLANE",PLANE="X",A0=1
DRIVER1: TFBDRIVER,ID="X-PLANE",STRENGTH=-0.01,&
A0=0.1105667038036287,A1=-0.4880365288553962,A2=-0.6624823916498349,&
A3=-0.3182102815177881,A4=0.3581627168475968,A5=1
PICKUP2: TFBPICKUP,ID="Y-PLANE",PLANE="Y",A0=1
DRIVER2: TFBDRIVER,ID="Y-PLANE",STRENGTH=-0.01,&
A0=0.7152379433135255,A1=-0.9159840192804557,A2=-0.7992551126284315,A3=1
Pradeep Kumar

[michael_borland]

Pradeep,

Getting the same result depends on having the same twiss file. Can you post the Basic.twi file you are using?

--Michael

[Pradeep]

Dear Dr. Borland,
Please find attached Basic.twi file. Thanks.
Pradeep Kumar

[michael_borland]

Pradeep,

I'm not sure where the coefficients in the lattice file originated. I suggest using those generated by TFBFirSetup.

--Michael

[Pradeep]

Dear Dr. Borland,
I tried to estimate filter coefficients using Basic.twi file using command TFBFirSetup. I need help to know how we define the driver strength in lattice.lte file (example file multibunchCollectiveEffects)

xdriver: TFBDRIVER,ID=x-plane,output_file="%s.xfb",strength="-20 rec"
ydriver: TFBDRIVER,ID=y-plane,output_file="%s.yfb",strength="-2.4 rec 2 /"

from where the value of xdriver strength -20 rec (i.e. -5e-2) and ydriver strength -2.4 rec 2 / (i.e. -0.20833) is defined and how we define it for other lattices?

Pradeep Kumar