From: Jeff Wilkinson (jeffrey.wilkinson@usa.net)
Date: Thu Jan 17 2008 - 03:38:08 CET
I am using Fluka to simulate shielding around a cabinet x-ray system to design some auxiliary shielding. The simulation is working as expected, but is fairly slow. The simulation starts with an electron beam directed at a W/Rh target in vacuum. The resulting bremsstrahlung photons are transported through the vacuum, a collimator and filter, and then into the cabinet.
Since the x-ray production from the e-beam is so inefficient I am transporting a lot of scattered electrons through the simulation that I don't care about. I am guessing that I can increase my simulation speed by cutting off electrons as they leave the W/Rh target. I have been trying to do this without much success using EMFCUT cards. The attached input file is what I am using. This input defines a spherical region around the target to provide a volume where the primary beam electrons can be transported. Outside that region I would like to terminate the transport of the electrons.
When I look at the electron fluence plot it's obvious that electrons are still being transported through both vacuums and interacting with other materials in the housing. Am I running into trouble because the 2 regions are both vacuum, so there aren't interactions where they can terminate? Should I be restricting electron transport everywhere except the target and inner vacuum sphere?
If I define the vacuum around the inner sphere as any material, such as air, the electrons stop at the boundary. Is there a cleaner way to describe this problem?
I would be even happier if I could skip the use of the inner sphere entirely and just have all electrons leaving the target terminated. Is that possible?
Thanks,
Jeff Wilkinson
Medtronic Technical Fellow, Sr Principal R&D Engineer
Medtronic, Inc -- 8200 Coral Sea St NE -- Mounds View, MN 55112 USA
763-526-0483
0 0 MC-CAD
* BX1
RPP BX1 -27.2 36.2 -20.0 5.72 -27.2 36.2
* BX2
RPP BX2 -27.2 36.2 5.72 93.62 -27.2 36.2
* BX3
RPP BX3 -26.8 35.8 5.72 93.22 -26.8 35.8
* BX4
RPP BX4 -26.0 35.0 5.72 90.72 -26.0 35.0
* BX5
RPP BX5 -27.2 36.2 -20.0 93.62 -27.2 36.2
* BX6
RPP BX6 -26.0 35.0 6.52 6.92 -26.0 35.0
* BX7
RPP BX7 -26.0 35.0 5.72 6.52 -26.0 35.0
* C1
RCC C1 0.0 4.55 0.0 0.0 3.0 -0.0 3.0
* C2
RCC C2 0.0 2.0 0.0 0.0 2.5 -0.0 20.0
* C3
RCC C3 0.0 2.0 0.0 0.0 2.5 -0.0 3.0
* C4
RCC C4 0.0 5.72 0.0 0.0 1.2 -0.0 3.0
* C5
RCC C5 0.0 3.23 0.0 0.0 3.69 -0.0 3.0
* C6
RCC C6 0.0 3.23 0.0 0.0 3.69 -0.0 2.9
* C7
RCC C7 0.0 -4.4 -0.5 0.0 0.0 1.0 3.4
* CN1
TRC CN1 0.0 -4.4 -0.19 0.0 0.0 0.48 5.08 3.4036
* CN2
TRC CN2 0.0 -4.4 -0.29 0.0 0.0 0.48 5.08 3.4036
* PC1
PLA PC1 0.0 -0.27564 0.96126 0.0 0.572 0.0
* PC2
PLA PC2 0.0 -0.27564 -0.96126 0.0 0.572 0.0
* PC3
PLA PC3 0.96126 -0.27564 -0.0 0.0 0.572 0.0
* PC4
PLA PC4 -0.96126 -0.27564 0.0 0.0 0.572 0.0
* PF1
XZP PF1 3.23
* PF2
XZP PF2 3.3
* PF3
XZP PF3 4.2
* PF4
XZP PF4 5.72
* PF5
XZP PF5 6.02
* PF6
XZP PF6 6.28
* PF7
XZP PF7 6.92
* S1
SPH S1 0.0 0.0 0.0 1000.0
* S2
SPH S2 0.0 0.0 0.0 900.0
SPH S3 0.0 0.0 0.0 2.0
RCC D1 0.0 22.5 0.0 0.0 1.0 0.0 4.37
RCC D2 20.0 15.0 -24.0 0.0 0.0 1.0 4.37
END
* Reg # 1
* blkhole; assigned material: Blackhole; mat # (1)
blkhole 5 +S1 -S2
* Reg # 2
* void; assigned material: Vacuum; mat # (2)
void 5 +S2 -BX5
* Reg # 3
* cbsteel; assigned material: Iron; mat # (11)
cbsteel 5 +BX2 -BX3 -C1
* Reg # 4
* cbpb; assigned material: Lead; mat # (17)
cbpb 5 +BX3 -BX4 -C1
* Reg # 5
* housing; assigned material: Lead; mat # (17)
housing 5 +C2 -C3
* Reg # 6
* vacuum; assigned material: Vacuum; mat # (2)
ovacuum 5 +BX1 -( +C2 -C3 ) -( +CN1 -CN2 -C7 ) -C5 -S3
* Reg # 6
* vacuum; assigned material: Vacuum; mat # (2), inner eletron interaction region
vacuum 5 +BX1 -( +C2 -C3 ) -( +CN1 -CN2 -C7 ) -C5 +S3
* Reg # 7
* anode; assigned material: Tungsten; mat # (23), without electron interaction region
oanode 5 +CN1 -CN2 -C7 -S3
* Reg # 7a
* anode; assigned material: Tungsten; mat # (23), electron interaction region
anode 5 +CN1 -CN2 -C7 +S3
* Reg # 8
* toppb; assigned material: Lead; mat # (17)
toppb 5 +BX7 -C4
* Reg # 9
* topsteel; assigned material: Iron; mat # (11)
topsteel 5 +BX6 -C4
* Reg # 10
* cabair; assigned material: Air; mat # (28)
cabair 5 +BX4 -BX7 -BX6 -D1 -D2
* Reg # 11
* fhousing; assigned material: Aluminium; mat # (10)
fhousing 5 +C5 -C6
* Reg # 12
* fwindow; assigned material: Aluminium; mat # (10)
fwindow 5 +PF2 -PF1 +C6
* Reg # 13
* fair1; assigned material: Air; mat # (28)
fair1 5 +PF3 -PF2 +C6
* Reg # 14
* fair2; assigned material: Air; mat # (28)
fair2 5 +PF5 -PF4 +C6
* Reg # 15
* ffilter; assigned material: Aluminium; mat # (10)
ffilter 5 +PF6 -PF5 +C6
* Reg # 16
* fair3; assigned material: Air; mat # (28)
fair3 5 +PF7 -PF6 +C6
* Reg # 17
* fcollimator; assigned material: Lead; mat # (17)
fcollima 5 +PF4 -PF3 +C6 -( +PC1 +PC2 +PC3 +PC4 )
* Reg # 18
* fcair; assigned material: Air; mat # (28)
fcair 5 +PF4 -PF3 +PC1 +PC2 +PC3 +PC4
detect1 5 +D1
detect2 5 +D2
END
This archive was generated by hypermail 2.1.6 : Thu Jan 17 2008 - 12:51:16 CET