The OPAL Discussion Forum

[Chris Hall <chall AT radiasoft.net>]

Hi Jarno,

Have you checked the momentum spread values in your distribution command? They seem like they could be too large.

The spreads in momenta: SIGMAPX and SIGMAPY are beta * gamma ~ 1.9e-2 while the ion you define with kinetic energy of 60 keV would have beta * gamma ~ 0.001135

Reducing SIGMAPX and SIGMAPY and rerunning your file does give the expected result.

OPAL> * ************** B U N C H *********************************************************
OPAL> * NP              = 10
OPAL> * Qtot            =          nan [fC]         Qi    =          nan [fC]
OPAL> * Ekin            =      60.000 [keV]         dEkin =      125.005 [eV]
OPAL> * rmax            = (      0.00577 ,      0.00934 ,      1.41280 ) [m]
OPAL> * rmin            = (     -0.00652 ,     -0.00590 ,     -1.83719 ) [m]
OPAL> * rms beam size   = (      3.92589 ,      5.05274 ,    876.44496 ) [mm]
OPAL> * rms momenta     = (  1.74034e-05 ,  2.00784e-05 ,  1.11049e-06 ) [beta gamma]
OPAL> * mean position   = (      0.00000 ,      0.00000 ,      0.00000 ) [um]
OPAL> * mean momenta    = ( -1.35525e-21 ,  6.77626e-22 ,  1.13470e-03 ) [beta gamma]
OPAL> * rms emittance   = (  3.69485e-05 ,  4.72728e-05 ,  8.13134e-04 ) (not normalized)
OPAL> * rms correlation = (  7.89465e-01 ,  8.48699e-01 ,  3.17525e-01 )
OPAL> * hr              = (      0.81947 ,      1.01585 ,    104.83819 ) [mm]
OPAL> * dh              =   1.00000e-10 [%]
OPAL> * t               =        0.000 [fs]         dT    =        1.000 [ns]
OPAL> * spos            =        0.000 [um]
OPAL> * ********************************************************************************** 

best,

Chris

On Wed, Apr 6, 2022 at 5:35 AM Van de Walle Jarno <jarno.van.de.walle AT sckcen.be> wrote:

Hello Andreas,

 

Thanks for your quick reply!

 

There seems indeed some misinterpretation of restmass and kinetic or total energy …

 

The restmass for an ion of mass 100 (say, for ease we consider Sn-100) is than 100*amu = 93149.41 MeV

The kinetic energy is only 0.06 MeV

Total energy follows naturally.

Gamma = 1.0000006441

B.rho = 0.352663 T.m

These values are correct in the input file.

 

So in the ‘BEAM’ statement I :

- omit the PARICLE definition (since it’s none of the predefined symbolic constants). When running OPAL notifies it’s assigning ‘UNNAMED’

- MASS = rest mass, correct ? Not total mass ?

- CHARGE = 1+

- BEAM ENERGY I specify as GAMMA (since it has highest priority, as read from paragraph 14.1 in the manual)

- BFREQ I assigned according to your suggestion (although we have a continuous beam here, but I suppose this doesn’t really affect the tracking ?)

- BCURRENT = 1e-6

 

When running like this, I get:

=> Momentum is zero ?

 

And weird Ekin and dEkin definitions in “BUNCH” output

 

Can the code really be used for none predefined particles, like I try to do here ?

 

Many thanks in advance for any further assistance!

With kind regards

Jarno

 

 

 

 

 

From: Adelmann Andreas (PSI) <andreas.adelmann AT psi.ch>
Sent: woensdag 6 april 2022 12:45
To: Van de Walle Jarno <jarno.van.de.walle AT sckcen.be>
Cc: opal AT lists.psi.ch
Subject: Re: [Opal] beamline simulation for low energy radioactive ion beams

 

Hi Jarno you need to define the charge for example 

 

 

REAL f1   = 50.65;  // MHz 

 

 

"RIB": BEAM, MASS=E0*1e-3, charge=1.0, ENERGY=E_TOT*1e-3, npart=10.0, BCURRENT=1.0E-6, BFREQ= f1;

 

Still, something seams to be off with the rest-mass. Consider to check by printing some values like:

 

value, {sr_gamma, E0};

STOP;

 

Otherwise I will look at this again.

 

 

 

Cheers Andy 

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On 5 Apr 2022, at 15:52, Van de Walle Jarno <jarno.van.de.walle AT sckcen.be> wrote:

 

Hello,

 

I’m new to OPAL and I’m trying to simulate a beamline for radioactive ions, which I did in MAD-X, now in OPAL.

The properties of the beam are:

Mass = 100 (amu)

Energy = 60 keV (!)

The beamline consists of 4 quad doublets and 1 dipole (112 degrees).

In MAD-X this runs smoothly and I wanted to check first of all if I can get similar results with OPAL. The next step would be to include a real 3D magnetic field map for the dipole in OPAL (which is not possible in MAD-X).

 

The first results are not encouraging L

I encounter multiple issues – which are probably related to a misinterpretation of the input file needs …

E.g.:

- when including the dipole, the tracking takes way too long to be realistic (so somewhere the tracking blocks)

- If I exclude the dipole (like in the attached inputfile), I see that The Kinetic energy of the beam is suddenly 4.528 GeV with dE = 19.686 MeV ?! No idea why …

 

I’m in any case convinced that OPAL could help us further in the simulation of our Radioactive Ion Beam beamlines and in the future our 100 MeV proton accelerator.

May I ask you to run the attached input file and/or hint towards my (obvious, maybe J) mistakes ?

 

Any help is highly appreciated !

Many thanks in advance and kind regards

Jarno

 

 

 

Jarno Van de Walle, PhD
Beam physicist

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+32 14 33 84 16 ǀ +32 470 20 98 31

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Belgian Nuclear Research Centre

Boeretang 200 - 2400 Mol – Belgium

www.sckcen.be

 

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