12.07.2015 Views

Monte Carlo Particle Transport Methods: Neutron and Photon - gnssn

Monte Carlo Particle Transport Methods: Neutron and Photon - gnssn

Monte Carlo Particle Transport Methods: Neutron and Photon - gnssn

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

a ( X506 <strong>Monte</strong> <strong>Carlo</strong> <strong>Particle</strong> <strong>Transport</strong> <strong>Methods</strong>: <strong>Neutron</strong> <strong>and</strong> <strong>Photon</strong> Calculationsgame (number of simulation particles), then the final score isM 1=kWi.e.,k = 1/qThe variance of the score in the biased game isD 2 = W 2 k(l - k) = Mfq 2 k(l - k) = M 2 (q - 1)In contrast, the expected number of particles transmitted in the analog game is M 1. eachhaving a weight of unity, <strong>and</strong> therefore the variance of the analog game isD 2 = M 1(I - M 1)The ratio of the two variances isD 2 /D 2 = M,(q - 1)/(1 - M 1) =e-~ ^ ~ 1for certain values of x <strong>and</strong> E. Now, if b is positive, then the kernels are nonphysical aroundthe preferred direction (p. ~ 1). At the same time, a second problem is faced in the oppositedirection, namely, the weights of the particles will strongly fluctuate. This can be demonstratedin the case of a homogeneous slab. In this case, the second moment of the weight

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!