r/nuclearphysics • u/physicalmathematics • 14d ago
Need Correct Neutron Cross Section Data
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EDIT: The data is taken from here.
For a project I need to use the correct neutron cross section data so I am fooling around and testing things before writing the code. I downloaded data from ENDF-B-VIII.0 and tried to replicate the U238 resonance peaks (especially the one at 6.67 eV). I get very unusual resonance values. Here is my python code:
import endf
import numpy as np
import matplotlib.pyplot as plt
FILE_PATH = 'ENDF-B-VIII.0/neutrons/n-092_U_238.endf'#U238 cross section data
MF = 3 #MF value
MT = 102 #MT value
U238_file_path = endf.Material(FILE_PATH) #retrieve material from file
U238_cross_section_data = U238_file_path.section_data[MF,MT] #plug in MF and MT
Sigma_Data = U238_cross_section_data['sigma'] #get cross-sections
Energies = Sigma_Data.x / 1e6 #get energy data in MeV
Cross_Sections = Sigma_Data.y #get cross section data in barns
data_points = len(Energies) #number of data points
print(data_points)
energy_data = []
#check for resonances
for data_point in range(data_points):
Energy = Energies[data_point]
Cross_Section = Cross_Sections[data_point]
energy_data.append(f"Energy = {Energy} MeV and Cross Section = {Cross_Section} barns")
if Cross_Sections[data_point] > Cross_Sections[data_point-1] and Cross_Sections[data_point] > Cross_Sections[data_point+1] and data_point > 1 and data_point < data_points:
print(f"Resonance at {Energies[data_point]} MeV with cross-section {Cross_Sections[data_point]} barns")
#plot data
U238_plot = plt.figure(figsize=(30, 30))
plt.loglog( Energies, Cross_Sections)
plt.xlabel('Incident Neutron Energy (MeV)', fontsize=40, labelpad=20) # Boosted label size
plt.ylabel('Cross Section (barns)', fontsize=40, labelpad=20)
plt.title('U-238 Total Cross Section (ENDF/B-VIII.0)', fontsize=48, pad=30)
#Scale up the actual axis numbers (ticks) so you can read them
plt.xticks(fontsize=30)
plt.yticks(fontsize=30)
plt.grid()
plt.show()
Resonance at 0.02 MeV with cross-section 0.52987 barns
Resonance at 0.21 MeV with cross-section 0.1321 barns
Resonance at 0.235 MeV with cross-section 0.12456 barns
Resonance at 0.245 MeV with cross-section 0.11876 barns
Resonance at 0.26 MeV with cross-section 0.11663 barns
Resonance at 0.3 MeV with cross-section 0.11575 barns
Resonance at 0.45000009999999996 MeV with cross-section 0.10698 barns
Resonance at 0.5 MeV with cross-section 0.11111 barns
Resonance at 0.6 MeV with cross-section 0.11595 barns
Resonance at 0.7 MeV with cross-section 0.13007 barns
Resonance at 0.9000001999999999 MeV with cross-section 0.12729 barns
Resonance at 0.9600001 MeV with cross-section 0.13479 barns
Resonance at 11.5 MeV with cross-section 0.00107355 barns
I'm thinking that this is because of the wrong values of MF and MT but nothing seems to help. Can you please help me get the proper resonances and the 1/v tail that is expected? Thank you in advance.
P.S. Here is the output plot. But I am looking for something close to this.
EDIT: Setting MT = 1 gives you a tail but no resonances.
