Re: [ibsimu-forum] Too small step size exception

[Kalvas, T. <tan...@jy...>]

Dear Ornella,

This looks ok. Please note that you do not define a beam with 880 uA, but you define a plasma flux which corresponds to 880 uA for a r=3 mm aperture. This would be exactly a beam with 880 uA current if there was no focusing effects before the collimating plasma electrode. But as you are calculating a plasma extraction system the plasma meniscus is formed and there are electric fields in the plasma sheath which affect the current being extracted. If you have a convex shape in the plasma meniscus there will be a focusing force at the sheath region, which increases the extracted current. This is what is happening here.

Taneli

--
Taneli Kalvas
Ph.D., Senior researcher
Department of Physics, room FL114
P.O. Box 35 (YFL)
40014 University of Jyväskylä, Finland
Mobile: +358-44-314-1602
Fax:    +358-14-617-411
Email:  tan...@jy...

________________________________________
From: Ornella Leonardi <orn...@ln...>
Sent: Tuesday, April 16, 2019 7:21:05 PM
To: ibs...@li...
Subject: [ibsimu-forum] Too small step size exception

Dear all,
I’m working with IBSimu from some weeks.
I’m running a simulation on a positive Ion Source.
I have a Mode_CYL geometry where I add a pexp_plasma at -3mm from the plasma electrode.
The simulation converges and complete all iterations, but on the console I see bad value concerning total beam current.
I add a beam of 880 micro Amp and during the iterations I get a total current on boundary 2 greater than the initial one.
At  Major cycle 0 I can read "Total beam current 0.00679A"
I report the total current (@boundary 2) trend vs. # interaction:
0) 0.000946 A
1) 0.000974 A
2) 0.000969A
3) 0.000975 A
4) 0.001176 A
5) 0.000961A
6) 0.001096 A
7) 0.00103 A
8) 0.001031 A
9) 0.001027 A
10)0.001035A

What am I doing wrong?
I attached my source code to allow you to check if I made any mistakes.
Thanks in advance.
Regards.
Ornella

--

Ornella Leonardi, Ph.D

Istituto Nazionale di Fisica Nucleare
Laboratori Nazionali del Sud
Via S. Sofia 62
95123 Catania (Italy)
office:   +39 095 542642
e-mail:   orn...@ln...<mailto:orn...@ln...>