DOUBLE SCATTERING NEUTRON DETECTOR

This experiment was developed to measure the solar and atmospheric neutrons in energy and direction above 50 MeV. The working principle is the double elastic scattering process of the incoming neutrons with hydrogen atoms.

In the figure at left can be seen a schematic drawing of the apparatus. The hydrogen is contained in thin plastic scintillator and polyethylene plates. Between these plates, spark chambers have been inserted in order to detect the trajectories of the recoil protons. The sparks are recorded photographically through a Fresnel prism and two mirrors for each of two coordinates. Charged particles which could trigger the apparatus are rejected by an anticoincidence counter. The whole stack of spark chambers and scattering material consists of six independent groups of equal thickness. Each group is viewed by a set of photo-multipliers which produce an electrical pulse upon the occurrence of a recoil proton. A coincidence of pulses from at least two of the six groups is required to indicate a double scattering event and to subsequently fire the spark chambers. The figure also shows three scintillator plates in the stack which can be used as additional anticoincidence counters against single scatterings with long proton tracks or Compton electrons or electron pairs of large range. A third camera records for each event the direction of the sun as seen from the apparatus. The apparatus is contained in a pressurized gondola which has a diameter of 170 cm and a height of 250 cm. The total weight of the experiment is about 1200 kg.

Balloon launched on: 5/25/1971 at 6:36 CDT
Launch site: Columbia Scientific Balloon Facility, Palestine, Texas, US  
Balloon launched by: National Center for Atmospheric Research (NCAR)
Balloon manufacturer/size/composition: Zero Pressure Balloon Winzen - 20.800.000 cuft (0.8 Mil - 2 Caps. 0.9 Mil. Stratofilm)
Balloon serial number: SF 375.08-080-NSC-06 Serial Nº 8
Flight identification number: 614P
End of flight (L for landing time, W for last contact, otherwise termination time): 5/25/1971
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): F 7 h 20 m
Landing site: In Big Springs, Texas, US
Payload weight: 3909 lbs

Balloon was launched at 6:36 CDT on May 25 1971 from the National Scientific Balloon Facility in Palestine, Texas. The balloon ascended nominally to 4.53 millibars and remained in flight for more than 7 hours. Payload landed near Big Springs, Texas.

• A balloon borne detector to determine high energy neutrons in energy and direction Nuclear Instruments and Methods, Vol. 88, p. 137
• Balloon experiment for the measurement of high-energy neutrons in cosmic radiation Picture at the media repository of the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, Germany
• Energy Spectrum and Angular Distribution of Atmospheric Albedo Neutrons 12th International Conference on Cosmic Rays, Tasmania, Australia, 1971. Volume 2., p.834
• Measurement of Earth Albedo Neutrons From 70 to 300 MeV 13th International Conference on Cosmic Rays, Denver, Colorado, Volume 2, p.903
• NCAR Scientific Balloon Facility Annual Report, 1971 National Center for Atmospheric Research, February 1972
• Review of Recent Performance of Large Balloons and Balloons with Payloads in Excess of 3000 Pounds Proceedings, Seventh AFCRL Scientific Balloon Symposium, 1973