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Simulating a Gaussian beam with 30mm 1/e^2 diameter in NSC

  • 14 February 2024
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Hello Everyone, 

I’d like to simulate a 48mm diameter beam (30mm 1/e^2) that is collimated using the source ellipse in non sequential mode, but I'm having trouble getting the distribution to appear gaussian. I’m attempting to calculate Gx and Gy using 2/sin^2(theta) where theta is the divergence angle but the distribution appears more flat top than gaussian. Am I approaching the problem wrong? I’d like to continue to use source ellipse if possible since I have other models with various beam sizes all using source ellipse currently. 

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Best answer by Elham 29 February 2024, 14:59

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Hi McGwire,

The Source Ellipse only sets a Gaussian distribution for the angular spread of the rays. This source has a spatial size, i.e., the launching surface. The position of the rays launched from this surface follows a uniform distribution. If you place a detector immediately after the source, the angular spread will be Gaussian but the positions will be like flat top. 

For modelling a Gaussian beam, if you need a point source that emits rotationally symmetric Gaussian distribution of rays, then Source Gaussian offers a simple model.

Another option is Source Diode. It gives you more freedom on how to define the Gaussian distribution. With Source Diode, you can assign Gaussian distribution to both the spatial and angular distribution of the rays. You can also have different emission areas on x and y, and different x and y far field divergence. 

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