Targets in nptool

nptool offers a full facility to simulate various types of targets. Having a target is mandatory for a simulation to run. The facility allows for solid targets (foil or bulk volume) as well as cryogenic targets with variable density values and entrance/exit windows.

There is no limitation of target thickness, although it is the user responsability to check that the target volume do not overlap with any other volume in the detector set-up.

When npanalysis is used the target position can be recovered and used as the reference point for every position measurement (e.g. with DSDSD detector).

Description of geometry file for solid target

The geometry file includes a GeneralTarget token indicating that a target is defined. The relevant part of the geometry input file corresponding to a standard solid target is given below:

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
GeneralTarget
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Target
THICKNESS= 10
RADIUS= 20
MATERIAL= CD2
ANGLE= 0
X= 0
Y= 0
Z= 0
NBLAYERS= 10

The thickness of the foil is given in micro-meter. The (X,Y,Z) coordinates of the target are given in millimeter and the angle of the target is given in degree and describes the rotation around the Y axis. The material of the foil is taken from the NPS::MaterialManager. If the material is not found in the library, npsimulation will issue a warning and use vacuum as the material.

The NBLAYERS token is optional and indicates the number of layers to be used to calculate the beam energy loss in the target in order to obtain the final inteaction energy. The default value is 5.

Description of geometry file for cryogenic target

In case of cryogenic targets the relevant part of the geometry input file is given below:

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
GeneralTarget
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
CryoTarget
THICKNESS= 3
RADIUS= 45
DENSITY= 1
MATERIAL= D2
WINDOWSTHICKNESS= 0
WINDOWSMATERIAL= Mylar
X= 0
Y= 0
Z= 0
NBLAYERS= 10

The thickness of the target indicates the thickness of cryogenic material and is given in micrometer. The windows thickness is also given in micrometer. Both cryogenic and windows materials are searched in the NPS::MaterialManager. If not found, vacuum is used as default material after a warning is issued. Other tokens have same meaning as in the solid target case.

Note that if the density given is 0 then the default density for the considered material will be used.

Important note the DENSITY token should be placed before the MATERIAL token.