Russian Aviation and Space Agency

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Present knowledge of HEND efficiency for neutrons
and gamma-rays  Workshop The First year of
HEND operations on the NASA Odyssey Mars
Orbiter Moscow, Russia May 20-22, 2002
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• Schematic design of HEND

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Schematic design of sensor LD (Left) and SD
(Right) for epithermal neutrons
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Components of SD and LD sensors
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He3n?H3p Etotal Etotal 0.764 MeV E(H3) 1/4
Etotal 0.191 MeV E(p) 3/4 Etotal 0.573 MeV
1/4Q TRITON
3/4Q PROTON
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Measured spectrum of counts of MD sensor is
represented in 16 channels
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Schematic design of stilbene and CsI
scintillation detectors
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Registration of neutrons on recoil protons 
Neutron
Recoil proton
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Separation between background and recoil protons
is done by help of anticoincidence circuit based
on CsI crystal which surrounds stilbene detector
in direction of open space
Proton
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Distinguishing between neutron and gamma signal
in stilbene crystal is done by help of electronic
pulse shape in the stilbene crystal
Photon
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PERFORMANCE LD 10.0 eV
- 1.0 MeV MD 0.4 eV -100.0
keV SD 0.4 eV - 1.0 keV
IN/SC/N 850 keV 15.0 MeV
IN/SC/G 60 keV 2.0 MeV OUT/SC 30 keV 1.0
MeV
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HEND energy range
Response functions of LD, MD and SC/neutron
sensors allow to fit data of 2, 3 and 4
periapses with function of type ?E-?
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Calibration facilities of Joint Institute of
Nuclear Research in Dubna (Russia) were used for
physical calibrations of 1st and 2nd Flight
Units of HEND
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PHYSICAL CALIBRATIONS The measured sensitivity
has met agreement with the numerical simulation
results
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PHYSICAL CALIBRATIONS The difference between
numerical calculation and measured value for SD
sensor takes place due to not taking account of
HEND model as an assembly
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PHYSICAL CALIBRATIONS The difference between
effective cross section of SC detectors of 1st
and 2nd Flight Units is resulted from different
electrical thresholds and it could be easily
taken into account
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• Future tasks
• Mathematical simulation
• building of HEND numerical model as an assembly
• building of HEND numerical model with taking
  into account the spacecraft model
• Physical calibration of HEND instrument with
  respect to gamma-rays and charge particles
• Establishing of correspondence between Flight
  end Qualification Units