Source definition for mono energy with angular divergance

Geometry, Fields and Transportation
1

Hello everyone,
i defined this source in my simulation:
/gps/particle proton
/gps/energy 15 MeV

/gps/pos/type Point
/gps/pos/centre 0 0 0 cm

/gps/direction 0 0 1

/gps/ang/type beam2d
/gps/ang/sigma_x 1 deg
/gps/ang/sigma_y 1 deg

But the direction of beam is -Z direction. i want to change the direction to +Z. so I changed 1 to -1, (/gps/direction 0 0 -1). but there is no change.
Is there a way to change the direction to +Z without using the rotation commands (/gps/ang/rot1 1 0 0, /gps/ang/rot2 0 -1 0)?

2

Hi @fateme262

For the direction other then what you mentioned. You can do one thing.
Please give a try if it works,

/gps/particle proton
/gps/energy 15 MeV
/gps/pos/centre 0 0 0 cm

#Direction 
/gps/pos/type iso     #isotropic and direction will be controlled by theta and phi
/gps/ang/mintheta 90 deg
/gps/ang/maxtheta 90 deg
/gps/ang/minphi 180 deg
/gps/ang/maxphi 180 deg

## I turn off the switch beam2D
/gps/ang/type beam2d
/gps/ang/sigma_x 1 deg
/gps/ang/sigma_y 1 deg

As you can see that Z is completely eliminated and direction is controlled by theta and phi.
Please run some simulations, based on theta phi combinations. The above is one of the example.

Regards
VRS

3

There is weird behavior when using Point in terms of orientation. I have avoided those headaches with just using a very small circle:

/gps/pos/type Plane
/gps/pos/shape Circle
/gps/pos/radius 1 mm
4

Dear Dr.Sharma,

Thank you for your solution.
the problem is here that i want to keep 1 deg angular divergence in X and Y direction. By defining the ```
/gps/ang/type beam2d
/gps/ang/sigma_x 1 deg
/gps/ang/sigma_y 1 deg
the direction of beam change to -Z?

5

Thank you for your suggestion.

the problem is here that i want to keep 1 deg angular divergence in X and Y direction. By defining the ```
/gps/ang/type beam2d
/gps/ang/sigma_x 1 deg
/gps/ang/sigma_y 1 deg

The direction change to -Z?

6

If you have difficulties with GPS, you can do this kind of things with simple ParticleGun.
see example extended/eventgenerator/particleGun/Readme : case 3

7

Thank you Michel for your response.

This example can be helpful. i will try it.

Best

8

@fateme262

Let’s first understand,
What is beam2d and when you say angular sigma_x and sigma_y 1deg, what does it mean ?
beam2d means particle has directions via theta and phi. which further you define 1deg deviation.
Remember: Theta is from 0 to 180 degree, whereas phi is from -180 to +180 , and is responsible for direction.

Right. Okay.

What is the bottom line we learn, choose wisely phi for direction add +/-0.5degree deviation, and do the same thing with theta.

Do not define again and again type. You need to eliminate

## Eliminate these lines or turn off
#/gps/ang/type beam2d
#/gps/ang/sigma_x 1 deg
#/gps/ang/sigma_y 1 deg

A better test case for your simulation is below,

TRY IT

#Your macro looks like this
/gps/particle proton
/gps/energy 15 MeV
/gps/pos/centre 0 0 0 cm

#Direction which is equal to beam2D
/gps/pos/type iso     #isotropic and direction will be controlled by theta and phi
/gps/ang/mintheta 89.5 deg
/gps/ang/maxtheta 90.5 deg
/gps/ang/minphi 179.5 deg   ###GIVES DIRECTION
/gps/ang/maxphi 180.5 deg  ###GIVES DIRECTION

Regards

9

Thank you for your explanation.
Just i have a question: sigma_x and sigma_y 1deg is half of cone. it means full cone is 2 deg. So by considering this, theta will define with +/-0.5 deg deviation or +/- 1 degree?

Regards