A Monte-Carlo study of a precision magnetic spectrometer with planar geometry

The possibility of reconstructing the true mean initial energy at the origin employing a detector having a linear dependence of mean energy losses on path length in its components is demonstrated. A Monte-Carlo study of a magnetic spectrometer with planar drift chambers orthogonal to the magnetic field direction has been done. Simulations were carried out for positrons in the range 20–50 MeV in a magnetic field B = 2 T and DME as the drift gas. It is shown that 2 keV reconstruction accuracy of a mean energy at the origin can be achieved without using any specific information about the value of energy loss of positrons in the detector. A suggested “sliding” technique provides track reconstruction with a reliable confidence level by eliminating most large kinks. Application of 1cos θ energy loss dependence to continuous spectrum reconstruction is studied. The influence of the Lorentz drift angle and positive ion effects on reconstruction accuracy has been analyzed. It is shown that though under certain circumstances the Lorentz drift effect can cause significant shifts of a mean reconstructed energy and distortions of the continuous spectrum, these distortions become negligible for a distributed source or one averaged over 2π azimuthal angle range and a continuous flat spectrum can be reconstructed with total statistics up to 1012 in 4π solid angle without systematic error.