Please use this space to put important questions and answers that will help others with similar questions.

Do you have an up to date license or dongle for the version you're using?

TOPAS will sometimes crash with an “exception caught” error. This could be caused by something unusual in your INP file. If you've set up your own parameters and equations then check they are all sensible. Try putting limits on parameters to avoid them refining to values that could lead to, for example, square roots of negative numbers or division by zero.

You might also get an “exception caught” error if you don't have a correct license for TOPAS. With TOPAS academic, make sure you have the licence files saved in the same directory in which TOPAS was originally installed. If you move directory or computer you have to contact Alan for a new licence. To check if it is a licence problem try running one of the pre-written example INP files through TA. Or open a dos command or powershell window and go to your TOPAS directory. Type “tc.exe test_examples\zro2.inp” (or any other INP file) and see if that runs. If neither works it's probably a licence issue.

The ability to write complex INP files is one of the strengths of TOPAS. However this flexibility also means it is easy to make mistakes. If you get a crash look in the dialogue box of the run window or at the bottom of topas.log to see the error message. The text there should give you a clue as to where to look. There will often be a line number quoted for the error. Due to the way INP files are processed this may not exactly match your INP file. The line number is often closer to that in the topas.log file (which is a processed version of the INP file).

Sometimes the line number of the error can be misleading and the actual error is earlier. This could happen if there is an error (e.g. a missing semicolon in an equation) early in the file, but the formal syntax TOPAS is expecting doesn't get broken until later on.

If the line number doesn't help, try searching for any offending parameter reported in the dialogue box. After that try making your INP file progressively simpler until you isolate the error. When all else fails you can try asking the forum for help. The simpler your question and INP file is, the more likely you are to get a useful answer.

The instructions on the web at http://www.dur.ac.uk/john.evans/topas_academic/jedit_setup.htm have worked for 1000s of people. Problems normally only occur if you miss a step out, or don't have appropriate privileges on your computer. If you can't get jedit5.n working, you can try the older jedit4.3 or jedit4.2 instructions.

If your university has blocked use of jre (java run time environment) then openJDK 21 seems to work.

If all else fails, try watching the jEdit setup video on youtube (linked on the left or above).

You'll sometimes find that when you click on jEdit menus you get a load of “computer code” appearing, not the expected TOPAS commands.

There's a tick box called “Execute Scripts” in the bottom left of the XInsert menu window. Make sure it's ticked.

By default they were single click menus in jedit4.2 but are double clicks in jedit4.3