V-Particle passage through medium

Parameter Description Argument Order Argument Mnemonic Units Default Value
Length 1 L[cm] cm
Material Desnity 2 Ro g/cm**3
Nuclear charge 3 Z
Gradient 4 dL/dx
Tilt 5 Tilt deg
Edge Truncation coordinate 6 EdgeEnd cm

This element simulates the passage of a particle through a medium. It takes into account the energy loss in the medium and its fluctuations as well as transverse scattering. Finite thickness is taken into account in scattering. The element has an effect only during tracking; in all other calculations it is modeled as a drift of length L0. In tracking, every particle obtains independent random kicks and displacements in all 3 planes. The kicks are distributed according to a Gaussian probability density for the transverse planes and according to a Landau distribution in the longitudinal plane. The medium is considered to be a wedge of angle f in the horizontal plane. For positive f, the wedge thickness increases with an increase in the x-coordinate. The thickness of the wedge is equal to $L_0$ at $x = 0$. The front surface (the first one which beam encounters) of the wedge is located in x-y plane. The back surface of the wedge is tilted by angle f around y axis. Vertical dimensions of the wedge are unlimited. The wedge thickness becomes equal to zero if any of two conditions are satisfied. The first one is achieved when the value $D_s = L_0 + x \tan{f}$ becomes negative. The second condition sets the thickness to zero for all x coordinates smaller than x0. An example is shown in Figure below. If necessary the wedge can be rolled around s axis (beam direction). The properties of wedge material are determined by wedge density in g/cm2 and nuclear charge Z.

The line below presents an example of element description. The first parameter determines the wedge thickness at $x = 0$. The second sets the density of material. The third parameter determines nuclear charge Z. The fourth parameter is equal to $\tan{f} = dL/dx$. The fifth parameter determines the roll angle; and the sixth and last parameter sets the edge truncation coordinate.

vWedge1   L[cm]=1.3      Ro[g/cm^3]=1.3     Z=4	  dL/dx=0.1     Tilt[deg]=0     EdgeEnd[cm] = -5