[Last Change: 15 Feb 2012 (rev 15)]

SAOTrace Chandra Source definitions

SAOTrace can simultaneously simulate multiple sources, so it is possible to simulate very complex source fields in a single raytrace run. There is a lot of flexibility in how sources are defined; to accomodate this, sources are defined using the Lua scripting language.

Note: For single point sources you don't need to know much Lua at all.

What's documented here is the simplified SAOTrace interface to its source generating capabilities. There's another, more complex one interface which is usually hidden, but sometimes is used (e.g. in the load_sources function )

What is a source?

As far as SAOTrace is concerned, a source is composed of

• A two dimensional physical extent
• A position
• A spectrum

For Chandra simulations, a source is defined by calling a function specific to the type of physical extent (e.g. point()) and passing it arguments which specify the position and spectrum. For example, here's a script creating a point source located 10' off-axis with an azimuth of 22° and a monochromatic energy of 1.49 keV:

point{ position = { theta = 10, phi = 22 },
       spectrum = 1.49
     }

Parameters which define physical quantities (such as theta and phi) typically require units, but some functions will assume default units. To express physical quantities with units, see here.

Here's documentation on the three components of sources:

1. The following source extents are available:
   • disk
   • image
   • point
   • rect
2. How to specify a source's position
3. How to specify a source's spectrum