The OPAL Discussion Forum

[Christof Metzger-Kraus <christof.j.kraus AT gmail.com>]

Hi Simon,

the imported distribution is shifted in longitudinal direction by 3.5 m. However the position of a  particle is considered relative to the position of the reference particle. You should therefore shift the mean position of your distribution to z=0. Then you'll see the effect of the quadrupole.

Best regards,

christof

On Mon, Oct 5, 2020 at 5:25 PM Dr. Simon Friederich <s.friederich AT uni-mainz.de> wrote:

Good evening Christof,

I've subtracted the 'offset' in the mean values in the x- and y- direction and converted the monitor output again to an OPAL-readable format.
But unfortunately there is still another issue:

The imported (FROMFILE) distribution does not get (de)focused by a quadrupole. (*) An injected gaussian distribtion (with the same RMS-values as start values) does behave as expected (see the attached picture; 'prior' = injected (OPAL generated) distribution, solid lines = imported (FROMFILE) distribution).

I've checked: According to the reference particle and mean values the imported distribution should go through the quadrupole with the correct energy (so it's not too stiff or misses the quadrupole; maybe I've emitted neutrons ':))

The input and distribution file can be found in my seafile:
https://seafile.rlp.net/d/f9141dd1c8ad46829af8/

Best regards,
Simon

(*: This is the only element I've tested so far as it is the one I'm looking for.)

Am 03.10.2020 um 22:12 schrieb Christof Metzger-Kraus:

Hi Simon,

I can indeed confirm, that this is a bug (quite a stupid one I have to admit). If you use a temporal monitor then the bunch is always shifted In both transverse directions by half a centimeter (independent on where the monitor is in space or time).

Christof

On Fri, Oct 2, 2020 at 5:34 PM Dr. Simon Friederich <s.friederich AT uni-mainz.de> wrote:

Dear Christof,

Today I wanted to use your suggestion and put a MONITOR at 3.5m in the beamline. I found out later, that it somehow has an offset in transverse direction when comparing it with the main .h5-file storing the phase spaces.

I've put a screenshot of the 2D transverse beam profiles in the attachement (again: This is the same simulation, picture left = monitor file, picture right = main.h5 file @ SPOS = 3.5m).

Did I miss something?

I implement the monitor using:

    tmon_3500: MONITOR, Z=3.5, OUTFN="distr_3500", TYPE=TEMPORAL;

Best regards
Simon

Am 09.07.2020 um 10:29 schrieb Christof Metzger-Kraus:

Hi Simon,

if I remember correctly then the beam is always emitted at z = 0. I don't know what (if at all) effect OFFSETZ has when the beam is emitted. But I'm sure we will find another way to accomplish what you intended. E.g. you could use a monitor with TYPE = TEMPORAL. Then you use the recorded distribution (using FROMFILE) in the following optimization. The downside of this approach is that you have to export the data from the hdf5 file to ascii (using e.g. matlab/octave or python).

Best regards,

Christof

On Tue, Jul 7, 2020 at 6:47 PM Dr. Simon Friederich <s.friederich AT uni-mainz.de> wrote:

Dear OPAL-Team,

My goal: I want to inject an electron bunch with a gaussian distribution at Z=-0.2 and have it cross a solenoid which is located at 0.0.

I tried: To use the OFFSETZ parameter, but it has not the desired effect (I expect the stat-file to start from s=-0.2m, right?).

I have also tried: To change the CATHODE's position, but it has no(t the desired) effect either.

I wanted to use the OFFSETZ parameter once to import a particle distribution at a specific point within my beam line so that I don't have to change the elements position and get the same result as if I injected the start-distribution at (0,0,0). [The purpose was to save computational time, because I could optimize the beam line step by step without having to simulate everything from the beginning]

If you find the time, maybe you could have a look at my input files and tell me what I've missed here.

Best regards,

Simon

-- 
Dr. Simon Friederich
Helmholtz-Institut Mainz
Kollaboration B/ACID
Johannes Gutenberg-Universität Mainz
Staudingerweg 18
55128 Mainz, Deutschland

Tel.: +49 (0)6131 39-23160
E-Mail: s.friederich AT uni-mainz.de

-- 
Dr. Simon Friederich
Helmholtz-Institut Mainz
Kollaboration B/ACID
Johannes Gutenberg-Universität Mainz
Staudingerweg 18
55128 Mainz, Deutschland

Tel.: +49 (0)6131 39-23160
E-Mail: s.friederich AT uni-mainz.de

-- 
Dr. Simon Friederich
Helmholtz-Institut Mainz
Kollaboration B/ACID
Johannes Gutenberg-Universität Mainz
Staudingerweg 18
55128 Mainz, Deutschland

Tel.: +49 (0)6131 39-23160
E-Mail: s.friederich AT uni-mainz.de