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αSPECT Neutron Decay Spectrometer



  A Silicon Drift Diode as Proton Detector in the
αSPECT Neutron Decay Spectrometer
  The neutron is a neutral particle slightly heavier than the proton and contained in the nucleus of any atom apart from hydrogen. As a free particle it is unstable and decays with an average lifetime of about 15 minutes into a proton, an electron and a neutrino. Free neutrons can be obtained from a suitable nuclear reaction.
The research reactor Forschungs-Neutronen-
quelle Heinz Maier-Leibnitz (FRM II) at Technische Universität München employs nuclear fission with moderation to provide intense beams of free neutrons for neutron scattering and particle physics experiments.
  Schematic of aSPECT, a spectrometer
Schematic of αSPECT, a spectrometer measuring the angular correlation coefficient ”α” in neutron decay from the proton recoil spectrum.
  Studies of decay properties of this nuclear particle offer unique opportunities to investigate strength and details of the weak force responsible for radioactivity.  
  The neutron decay spectrometer αSPECT (Figure at the top on the right) has been developed by research groups from Munich and Mainz to measure the integral energy spectrum of the protons. The goal is to determine the ratio of the axialvector-to-vector weak coupling constants of the nucleon with highest possible accuracy. This in turn is fundamental input to calculate weak cross sections important for Big Bang nucleosynthesis and stellar fusion, as well as for tests of particle physics standard model.
[more... PDF document PDF 215 kB]
  Scientific Publication:  
PDF document Detection of low-energy protons using a silicon drift detector
Nuclear Instruments and Methods in Physics Research, NIM A 581, 772-775 (2007  [PDF 252 kB]
Link to external website The αSPECT experiment at the TU München Physics Department E18  
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Graph of proton pulse height spectra for different proton impact energies. The peak at low energies is the noise of the detector and the electronics.