NUCLEAR AND RELATED TECHNIQUES FOR PLANETOLOGY

Transcription

1 NUCLEAR AND RELATED TECHNIQUES FOR PLANETOLOGY V.Shvetsov, FLNP, JINR Round Table Dubna on

2 PLANETARY SCIENCE The scientific study of planets (including Earth), moons, and planetary systems, in particular those of the Solar System and the processes that form them; Incorporates many disciplines, including planetary astronomy; planetary geology (together with geochemistry and geophysics); atmospheric science, oceanography, hydrology, theoretical planetary science, glaciology, and the study of extrasolar planets. Round Table Dubna on

3 NUCLEAR RADIATION AT SPACE Solar Particles Round Table Dubna on Galactic Cosmic Rays

4 NUCLEAR RADIATION AT SPACE Round Table Dubna on Solar particles (protons & alphas); GCR (protons, alphas, light nuclei); Gamma and X-rays; Secondary neutron radiation;

5 SECONDARY RADIATION TOOL FOR SOIL/ATMOSPHERE ANALYSIS GCR are easily penetrate through thin Martian atmosphere and produce secondary protons/neutrons in upper soil layer. Secondary radiation carries information about soil elemental /isotopic composition. Masarik, J. and Reedy, R.C., Gamma Ray Production and Transport in Mars, J. Geophys. Res., 1996, vol. 101, pp Round Table Dubna on Gamma Spectra at Martian Orbit

6 MARS ODYSSEY 2001 Gamma sensor head (HPG) Thermal neutron detector (NS ) Solar array High energy neutron detector (HEND) High gain antenna Star cameras THEMIS Round Table Dubna on

7 HEND December 1999 September 2000 Работа по созданию HEND велась в : Росавиакосмос ИКИ ОКБ ИКИ СНИИП ОИЯИ ВИМС и др. April 7, 2001 February 19, 2001 University of Arizona NASA JPL LMA NASA KSC

8 Space port Cape Canaveral (Florida, USA), Mars Odyssey mission Purpose of expedition: exploration of Martian surface (research of chemical composition of the surface and search for water); Scientific equipment: HPG gamma-ray spectrometer (GRS), low energy neutron spectrometer (NS); high- energy neutrons detector (HEND); thermal emission imaging system (THEMIS); radiation environment measuring system (MARIE); Total mass of a scientific equipment: 44.5 kg Arrival to Mars:

9 Building the Map On the surface of planet making a mesh with selected size of pixels. In each pixel independently accumulating counts and exposure time. Selecting a time interval, detector and set of channels to create map. H 400 km Ø 400 km Main parameters of orbit: Altitude 400 km; Orbital period 2 hours; Orbit inclination Round Table Dubna on

10 Counts GAMMA SPECTRA ON MARTIAN ORBIT Odyssey Mapping Spectrum 335-hour accumulation Odyssey Cruise Spectrum 948-hour accumulation Round Table Dubna on Energy (kev) keV

11 Counts / min / kev H (2223) Al (2210) North (raw, >+75º) South (bkg corrected, < -60º) Middle (bkg corrected, > -60º, < +75º) Round Table Dubna on Energy (kev)

12 NEUTRON DETECTORS HYDROGEN SENSITIVITY Number of neutron collisions to slow down Element Atomic weight Number of collisions to slow down from 1 MeV to 0.1 ev Hydrogen 1,008 16,1 Carbon 12,01 102,2 Silicium 28,1 231,9 Lead 207, Round Table Dubna on

13 60 o 30 o 0 o -30 o -60 o North pole South pole Международная научная школа. "Современная нейтронография: от перспективных материалов к нанотехнологиям". 31 октября - 4 ноября 2011г. Дубна. Martian topografy

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15 Международная научная школа. "Современная нейтронография: от перспективных материалов к нанотехнологиям". 31 октября - 4 ноября 2011г. Дубна.

16 W/O H 2 O 1% H 2 O 10% H 2 O 20% H 2 O N(E), neutrons/(cm 2 MeV) ground without water ground + 50 % uniformly dispersed water top water layer 20 cm water layer 20 cm lies 1 m beneath the surface x Neutron energy, MeV Round Table Dubna on Albedo neutron spectra at a height of 400 km normalized to 1 n/cm 2 neutron flux from Mars surface covered with CO 2 layer 15 g/cm 2 (calculated by MCNP4C) Energy, MeV Number of neutrons, n/cm

17 High Energy Neutron Detector Total weight: kg Power supply: 5.7 watt SD, MD, LD 3 He proportional counters enveloped with PE of different thickness SC stilbene scintillator with CsI anticoincidence counter Pulse height analysis 5 sensors = 6 signals: 1-4 neutrons MeV kev GCR and solar protons

18 Neutron flux density, n/cm Sensitivity, cm 2 1E-3 MD Sens. SC Sens E-4 CO2 + 1% H2O, N/cm^2 = 7,09E-01 1% H2O, N/cm^2 = 7,79E-01 CO2 + 10% H2O, N/cm^2 = 5,58E-01 10% H2O, N/cm^2 = 6,05E-01 NO CO2 + NO H2O, N/cm^2 = 8,24E-01 CO2 + NO H2O, N/cm^2 = 7,49E-01 CO2 + 30% H2O, N/cm^2 = 4.44E-01 30% H2O, N/cm^2 = 4.96E-04 1E-9 1E-7 1E-5 1E E-3 1E-4 Neutron energy, MeV

19 Counts / min / kev Neutron Spectrometer First results of Mars surface scanning. Comparison of NS, GRS and HEND readings. 0.8 Al (2210) H (2223) 0.6 North (raw, >+75º) 0.4 South (bkg corrected, < -60º) 0.2 Middle (bkg corrected, > -60º, < +75º) Gamma Spectrometer Energy (kev) HEND

20 SEASONAL VARIATIONS

21 LUNAR EXPLORATION NEUTRON DETECTOR Round Table Dubna on

22 Counts, s Counts, s -1 Counts, s LEND Calibrations at Dubna LEND FU1 3 He counter #5 9 LEND FU1 3 He counter # Det5 counts w/o bgnd Data: det5high_e Model: GaussAmp Equation: y=y0+a*exp(-0.5*((x-xc)/w)^2) Weighting: y w = 1/(det5high_f)^2 Chi^2/DoF = R^2 = y ± xc ± w ± A ± Counts, s Det 8 counts w/o bgnd GaussAmp fit of det8high_e Data: det8high_e Model: GaussAmp Equation: y=y0+a*exp(-0.5*((x-xc)/w)^2) Weighting: y w = 1/(det8high_f)^2 Chi^2/DoF = R^2 = y ± xc ± w ± A ± Det6 counts w/o bgnd GaussAmp fit of det6low_e Angle, degrees LEND FU1 3 He counter #6 Data: det6low_e Model: GaussAmp Equation: y=y0+a*exp(-0.5*((x-xc)/w)^2) Weighting: y w = 1/(det6low_f)^2 Chi^2/DoF = R^2 = y ± xc ± w ± A ± LEND FU1 stylbene sensor (neutron channel) 1,3 Stylbene neutron counts 1,2 1,1 1,0 0,9 0,8 0,7 Data: stylbenenew_b Model: GaussAmp Equation: y=y0+a*exp(-0.5*((x-xc)/w)^2) Weighting: y w = 1/(stylbenenew_c)^2 Chi^2/DoF = R^2 = y ± xc ± w ± A ± Counts, s Det 7 counts w/o bgnd GaussAmp fit of det7low_e Angle, degrees LEND FU1 3 He counter #7 Data: det7low_e Model: GaussAmp Equation: y=y0+a*exp(-0.5*((x-xc)/w)^2) Weighting: y w = 1/(det7low_f)^2 Chi^2/DoF = R^2 = y ± xc ± w ± A ± , ,5 0, Angle, degrees 0, Angle, deg Angle, degrees

23 LEND RESULTS Round Table Dubna on Suppressed Neutron Regions Coinciding with Polar Shadowed Regions (Cabeus Crater)

24 BACK TO MARS MARS SCIENCE LAOBRATORY Round Table Dubna on

25 Instrument DAN onboard Mars Science Laboratory will allow to study content of Hydrogen in the shallow subsurface below the wheels

26 Instrument DAN onboard Mars Science Laboratory will allow to study content of Hydrogen in the shallow subsurface below the wheels

27 DAN PASSIVE MODE Thermal neutrons counter; Fast neutron counter (similar, but covered with Cd); Neutrons: Thermal and epithermal Epithermal Thermal Water amount in soil, %

28 Counting rate, counts/sec Counting rate, counts/sec DAN ACTIVE MODE Pulsed neutron generator; Thermal neutrons counter; Fast neutrons counter; Water, wgt% 0% 0.1% 0.3% 0.5% 1.0% 3.0% 5.0% 10.0% 15.0% 20.0% 25.0% 99.0% Time after PNG pulse, sec Water, wgt% 0% 0.1% 0.3% 0.5% 1.0% 3.0% 5.0% 10.0% 15.0% 20.0% 25.0% 99.0% Time after PNG pulse, sec

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