1. An Innovative Approach to Compact Calorimetry in Space, NEUCAL
FRONTIER DETECTORS FOR FRONTIER PHYSICS May 2009
An Innovative Approach to Compact Calorimetry in Space, NEUCAL
S. Bottai, O. Adriani, L. Bonechi, M. Bongi, G. Castellini, R. D’Alessandro, P. Papini, S. Ricciarini, G. Sguazzoni, G. Sorichetti, P. Sona, P. Spillantini, E. Vannuccini.
INFN (Florence) and University of Florence, Via Sansone 1, Sesto Fiorentino, Italy
Expected neutron yield
Basic idea
Electromagnetic/hadronic showers identification is a common requirement in High Energy Physics and in particular for space detectors devoted to Astroparticle Physics.
Space detectors make use of heavy and complex imaging calorimeters in order to achieve the necessary shower identification-rejection (ATIC,PAMELA,CALET….)
Different neutron yields are also expected from hadronic and electromagnetic showers. The use of an appropriate neutron detector can be used to rescale the calorimeter without loosing in identification power.
400 GeV electrons
1 TeV protons
Neutron detector
calorimeter
Electromagnetic
shower
e-, g P
hadronic
neutrons
CALET BGO CALORIMETER SIMULATED WITH FLUKA
Neutrons are produced in both hadronic and electromagnetic showers (GiantResonance is responsible for neutron production in electromagnetic showers). The figures show the outgoing neutrons/event from showers produced by electrons and interacting protons ( with similar energy release in the calorimeter). A rejection factor for hadronic showers as high as 103 can be achieved considering the neutron counting alone.
Neutron energy and timing
1 TeV protons
Peak of
excited nucleus
emission
Direct neutrons
emission in hadronic
interactions plus
moderation
E<1 MeV
60%
Outgoing neutron energy Log (E(GeV)/1GeV)
Outgoing neutron energy Log (E(GeV)/1GeV)
The bulk of neutrons comes from excitation and de-excitation of nucleus and exhibit a maximum in the MeV energy region. Many neutrons undergo moderation before escaping and their energy is consequently degraded down to the eV energy region. Some neutrons can also be produced promptly in the hadronic interactions along the shower core, with an energy that can reach that of the primary proton. The highest energy neutrons ( E>10 MeV ) arrive close in time with respect to the charged component of the shower, while the low energy and more abundant component arrives in the neutron detector with a delay of ns and can be easily identified. The figure for electromagnetic showers is similar but with a reduced contribution in the prompt neutrons emission
Arrival time of the charged
particles
NEUCAL : detection principle
NEUCAL : expected performance
The energy released during the moderation process is detected by means of an active moderator composed of several plastic scintillator layers. Neutrons with energy in the KeV-MeV region are detected with high efficiency.
Neutron-proton elastic scattering in the plastic scintillators provide the active neutrons moderation. Scattered protons release their energy inside the scintillators and are detected.
Scintillators layers (1cm each) :
an active moderator
3He Tubes (1 cm diameter) :
a neutrons counter
Few ns resolution
electronics to preserve
the timing information
The moderated neutrons can be detected by means of nuclear capture followed by 0,765MeV proton emission in the 3He proportional counters.
Thin layers of lead could enhance signals for very high energy neutrons
Simulated response for a 12 scintillator layers detector. Neutrons with energy up to few MeV are fully moderated and detected with high efficiency. At 10 MeV 70% of neutrons gives detectable signals, while only 10% are fully moderated and detectable by the 3He Tubes