Assuming your browser has a java plugin this application will display scaled real-time trajectories from a simulation of 1 GeV Neutrons entering a Space Ship Earth NM64 detector and interacting producing secondary particles. This version displays only neutron tracks, although the transport physics used in the calculation includes all known particle types (i.e. protons, electrons, pions, gammas,..) and nuclear fragments produced in the interactions, these are not drawn to reduce ambiguity.
The color of tracks distinguishes different energy ranges.
FLUKA transport code was utilized in this work.
Report any problems to John Clem at
clem@bartol.udel.edu .
Shades of Blue: E > 2MeV
Shades of Green: 1KeV < E < 2MeV
Shades of Red: E < 1KeV
Open Circle/Audio: Neutron Absorption in a tube producing a count
What is a Neutron Monitor ??
In a neutron monitor, neutron sensitive proportional tubes,
surrounded by moderator material and a lead target, detect
thermal neutrons produced locally from interacting incident
particles typically in the lead. Each proportional tube is
inside a 2cm thick low density polyethylene tube which is
surrounded by nearly 2 tons of 99.99% pure lead. The lead is
enclosed by another layer of 7cm thick polyethylene which serves as
low energy neutron reflector.
Even though neutrons do not leave an ion trail in the proportional
tube, the absorption of a neutron by a nucleus is
usually followed by the emission of charge particles which can
be detected. A SSE neutron monitor proportional tube is filled with
3He gas which responds to neutrons by the exothermic
reaction 3He(n,p)3H
with a Q = 770KeV (1GeV muon typically deposits 3KeV in the gas).
The reaction cross-section is inversely proportional to the neutron velocity,
having a 20oC thermal endpoint of roughly 5330 barns.
To run a java applet, your browser must have a java plugin (Java Virtual Machine) version 1.3 or higher.
This JVM plugin can be downloaded and installed at
java_installation . The Sun JRE package,
English only version, is roughly 10Mbytes in size.