Support:

Hello, my name is Néstor Cornejo Díaz. I am calculating the Awall correction factor for a spherical graphite chamber (3 mm wall, ri = 1.1 cm, rout = 1.4 cm, 1.25 MeV photons in parallel beam) with the code CAVITY (for Windows 64 bit, downloaded on 08/2018). The results of Awall seem not correct, (Awall is resulting > 1). The cavity dose being > than Dideal. This should not happen for this spherical chamber. I have repeated the calculations with the code CAVSPHnrc and the results are different, with Awall resulting < 1 (about 0.982), as expected for this spherical graphite chamber. I am attaching here the input file created for the CAVITY code.

Could anybody help me to find the reasons of this inconsistent result?

Thank for your support.

Kind regards,

Néstor

#

# CHAMBER SP-01

#

# —————

# GEOMETRY

# —————

:start geometry definition:

# ———————-

# spherical chamber

#————————

:start geometry:

name = chamber

library = egs_spheres

midpoint = 0 0 4

radii = 1.1 1.4

:start media input:

media = air graphite

set medium = 1 1

:stop media input:

:stop geometry:

#————————–

# A Vacuum box surrounding the chamber

#————————–

:start geometry:

name = outer_vacuum_box

library = egs_box

box size = 4 4 12

:start media input:

media = vacuum

:stop media input:

:stop geometry:

# ————————-

:start geometry:

name = chamber_in_vacuum

library = egs_genvelope

base geometry = outer_vacuum_box

inscribed geometries = chamber

:stop geometry:

simulation geometry = chamber_in_vacuum

# —————————

:stop geometry definition:

# —————————

# MEDIA DEFINITION

# —————————

:start media definition:

# —————————

# Cutoff energies

ae = 0.521 # lowest energy for electrons ( kinetic + 0.511)

ap = 0.01 # lowest energy for photons (kinetic)

ue = 2.511 # maximum energy for electrons (kinetic + 0.511)

up = 2 # maximum energy for photons (kinetic)

media

:start air:

density correction file = air_dry_nearsealevel

:stop air:

:start graphite:

density correction file = carbon_graphite_icru90_1.8g_cm3

:stop graphite:

:stop media definition:

# —————————

# SOURCE DEFINITION

# —————————

:start source definition:

:start source:

library = egs_parallel_beam

name = Parallel_beam

charge = 0

:start shape:

library = egs_circle

radius = 2

:stop shape:

:start spectrum:

type = monoenergetic

energy = 1.25

:stop spectrum:

direction = 0 0 1

:stop source:

:stop source definition:

# —————————-

# RUN CONTROL

# —————————-

:start run control:

ncase = 1000000

:stop run control:

# —————————-

# SCORING OPTIONS

# —————————-

:start scoring options:

calculation type = Awall

:start calculation geometry:

geometry name = chamber_in_vacuum

cavity regions = 1

cavity mass = 0.006717041

:stop calculation geometry:

:stop scoring options:

# —————————-

:start ausgab object definition:

:start ausgab object:

name = tracks

library = egs_track_scoring

:stop ausgab object:

:stop ausgab object definition:

# —————————-

:start MC transport parameter:

ESTEPE = 0.10

:stop MC transport parameter: