The OPAL Discussion Forum

[Daniel Winklehner <winklehn AT mit.edu>]

Dear Masao,

Yes, you can do it, but it requires some fiddling around at the moment. 

The most important question is: what beam current are you simulating? Is 
space charge an important factor or not so much? 

If space charge is very important for your application, you will have to 
compile OPAL with the SAAMG option ON. To my knowledge, there is no binary 
package that supports usage of the SAAMG solver that you can just download, 
but Achim can correct me on that.

If space-charge is unimportant, you can use the OPAL 2.2 binary.

In both cases, you will need to prepare the electric AND magnetic fields as 
3D fieldmaps in the center of the cyclotron as *.h5part format files. 
OPAL-cycl, by default, uses the midplane field only and gets the z =/= 0 
components from a series expansion. For the electrostatic inflector, you will 
need a more accurate field description along the spiral trajectory. There 
have been some email list discussions recently on how to transform 3D field 
data from ANSYS/TOSCA/COMSOL to h5part using a C script called 
ascii2h5part.cpp. I am using python with h5py, which works too. See attached 
for electrostatic case. Resulting fields can be checked with VisIt 3.1.1.

The fields can be loaded into OPAL-cycl by using the BANDRF type cyclotron 
and loading the fields as RF cavity fields with frequency = 1e-36 (i.e. 
static fields) and RFPHI = 0.0 and PI/2 for electric and magnetic fields, 
respectively. The units for these fields should be kV/mm (MV/m) and mm.

Finally, the geometry can be loaded as well. Firstly, as the boundary for 
particle termination, if you are interested in the losses. Secondly, as the 
boundary conditions for the SAAMG field solver (if you are using it). For 
geometry preparation, you will need the "negative" or "vacuum" space rather 
than the individual electrodes. This is described in the paper you mentioned. 
Just create a cylinder that encloses all your electrodes (maybe start with 
just the spirals) and subtract the electrodes from the cylinder as a Boolean 
operation in the program of your choice. Inventor works, so does FreeCAD 
(which is open source). Save as iges, stp, etc. and open in GMSH. In gmsh, 
you can mesh your geometry and save the mesh as vtk. Achim write a C++ 
program that translates vtk to h5block, which is the format OPAL needs for 
geometry.

If you do use SAAMG, you have to use the "SPIRAL" cyclotron type instead of 
BANDRF. 

I will write up better instructions for the whole process over the weekend 
and provide a simple example input deck to help along with getting started on 
this non-trivial process.

Best,
   Daniel



-----Original Message-----
From: opal-request AT lists.psi.ch <opal-request AT lists.psi.ch> On Behalf Of 
masao nakao
Sent: Friday, March 20, 2020 07:44
To: opal AT lists.psi.ch
Cc: nakaom AT rcnp.osaka-u.ac.jp
Subject: [Opal] Fwd: 3DElectroStatic

Dear OPAL developers,

I would like to simulate injection system of AVF cycltoron with electrostatic 
inflector.
Though OPAL manual shows 3DElectroStatic is "Not implemented yet."(p.173), a 
paper [1] shows results by OPAL. How can I calcurate like that? I have 3D 
electric field data culculated by TOSCA.
Thank you.

[1] "Realistic simulations of a cyclotron spiral inflector within a 
particle-in-cell framework"
Daniel Winklehner et al.
PHYSICAL REVIEW ACCELERATORS AND BEAMS 20, 124201 (2017)

Yours, sincerely,
Masao


--
Masao Nakao
Osaka University
Research Center for Nuclear Physics
Mail : nakaom AT rcnp.osaka-u.ac.jp
Phone: 06-6879-8914
FAX  : 06-6879-8899

Attachment: ascii2h5block_comsol.py
Description: ascii2h5block_comsol.py