The OPAL Discussion Forum

[Jochem Snuverink <jochem.snuverink AT psi.ch>]

Hello Anastasiya,

Many thanks for your questions and comments.

> Is the output now in [m] instead of [mm]?

Yes, the trackOrbit file is now in [m]. The header still indicates [mm] but is a bug. I have corrected this for the next release.

> What is the relationship between units of SLPTC in CYCLOTRON (OPAL 1.6) and SLPTC in TRIMCOIL (OPAL 2.0)?

In OPAL 1.6 SLPTC was in [mm], in 2.0 it has become its inverse [1/mm] to better reflect the fact that it is a slope. See also below.

> Also, do you have a working example/tutorial/test for OPAL 2.0 (i.e. new input files)?

No, not yet for the Cyclotron example. If you are interested I can add this. Your cyclotron2.in is correct by the way.

> BFREQ in BEAM seems to be in MHz in both the old and the new OPAL (inconsistent with release notes for OPAL 2.0). Other frequencies are in MHz (both OPAL
> 1.6 and OPAL 2.0) and the same values are used in example input files for FREQ in RFCAVITY and BFREQ in BEAM. If the value for BFREQ in 1.6 input file is
> multiplied by 1e-6, OPAL 2.0 throws an error "The particle is out of the region of interest" in ParallelCyclotronTracker. Is BFREQ units an old bug that got fixed or
> a new bug?

BFREQ is in MHz in both 1.6 and 2.0. This was unfortunately worded in the release notes, where it said ("partially introduced in OPAL-1.6"). I have updated this section to make it more clear which changes were already introduced in 1.6.

> Output file for OPAL 2.0 seems to be in [m] while OPAL 1.6 is in [mm]. Is that a bug or a feature? Should it be documented somewhere?

It was tried to unify the units between OPAL-T and OPAL-Cycl. Therefore meter is used more (unfortunately not yet everywhere). I have added a line in the Release notes.

> Trim coils are now a separate element TRIMCOIL with slightly different units for inputs: MBTC in [kG] and SLPTC in [kG/mm] are replaced by BMAX in [T] and SLPTC in [1/mm]
> (should probably be mentioned in release notes). Should SLPTC in TRIMCOIL be in [T/mm]?

Yes indeed, thanks for mentioning. The old description "PSI-RING-OLD" was changed indeed. SLPTC is now in [1/mm] (it was [mm], the old manual was wrong in this respect).
The parameters for this description are intertwined and opaque (hence not [T/mm], let me know if you would like to know the details), it is recommended to use the new "PSI-RING" type instead, that uses a generic rational function for the B-field description. I have added a line in the release notes.

Best wishes,
Jochem

On 18/06/18 18:33, Anastasiya Bershanska wrote:

Hello,

I’m trying to use OPAL 2.0 for running simulations and have questions about the conversion of input files from 1.6 to 2.0 as well as output standard. Is the output now in [m] instead of [mm]? What is the relationship between units of SLPTC in CYCLOTRON (OPAL 1.6) and SLPTC in TRIMCOIL (OPAL 2.0)? Also, do you have a working example/tutorial/test for OPAL 2.0 (i.e. new input files)?

The unexpected changes that I’ve noticed are:

• BFREQ in BEAM seems to be in MHz in both the old and the new OPAL (inconsistent with release notes for OPAL 2.0). Other frequencies are in MHz (both OPAL 1.6 and OPAL 2.0) and the same values are used in example input files for FREQ in RFCAVITY and BFREQ in BEAM. If the value for BFREQ in 1.6 input file is multiplied by 1e-6, OPAL 2.0 throws an error "The particle is out of the region of interest" in ParallelCyclotronTracker. Is BFREQ units an old bug that got fixed or a new bug?
• Output file for OPAL 2.0 seems to be in [m] while OPAL 1.6 is in [mm]. Is that a bug or a feature? Should it be documented somewhere?
• Trim coils are now a separate element TRIMCOIL with slightly different units for inputs: MBTC in [kG] and SLPTC in [kG/mm] are replaced by BMAX in [T] and SLPTC in [1/mm] (should probably be mentioned in release notes). Should SLPTC in TRIMCOIL be in [T/mm]?

I’ve also attached new cyclotron2.in that I’ve changed to work with OPAL 2.0 (see Cyclotron example). The output is consistent with the example online (resulting plot where cyclotron2.gpl takes in m instead of mm), so I wonder if all changes are correct, SLPTC in [T/mm] and BFREQ (unchanged) in particular.

- Anastasiya