Exercise: Insert a sample

1. Now, insert a V_sample() component (Vanadium, scatters in all directions) after the last PSD_monitor and L_monitor. Insert a Beamstop component after the sample, e.g. AT (0,0,0.5) RELATIVE sample. At the same position as the sample, insert a PSD_monitor_4PI_log component of radius 1.0 m., located AT (0,0,0) RELATIVE to your sample. Also, insert a Beamstop component after the sample, e.g. AT (0,0,0.5) RELATIVE Read the documentation for details on input parameters. Run a simulation. Notice the number of hits.
2. Restrict the solid angle of scattering from the vanadium sample, focus on the PSD_monitor_4PI_log by using target_x=1 and e.g. focus_r=0.2 as input parameter to the sample. Run a simulation. Notice the number of hits. Improvement?
3. Next, let us insert something more interesting. Remove the V_sample and PSD_monitor_4PI_log. Insert a Powder2 component with the following parameters:

   COMPONENT sample = Powder2(radius=0.01,h=0.01, q_1=1, q_2=1.3,
      w_1=0, w_2=0, d_phi0=0.1, pack=0.5, DW=0.9, frac=0.5, 
      focus_r=0.03, j_1=8, j_2=4, F2_1=1000, F2_2=1000, 
      Vc=3.86*3.86*11.82, sigma_a=0, sigma_inc=2,
      target_x = 0, target_y = 0, target_z = 0)
     AT (0, 0, 0) RELATIVE a4
   

   (Adjust placement relative to your component naming etc.). Also insert a banana shaped detector,

   COMPONENT ND = Monitor_nD(xwidth=1, options="banana, theta limits=[-45 45],auto y")
     AT (0,0,0) RELATIVE a5
   

   and take away the previously inserted Beamstop. Run a long simulation (many neutrons) and have coffee.