Project Structure Advanced Neutron Spectrometer on the International Space Station (ANS-ISS) Mark Christl NASA/MSFC Oct 23, 2015 Honolulu, HI 1 1

RadWorks (aka Radiation Sensors) Advance Exploration System (AES) Sponsoring office RadWorks: JSC Lead JSC: HERA, BIRD charged particle sensors (ionizing radiation) LaRC: Storm shelter and modeling MSFC: ANS (neutron spectrum) Phase I: Develop neutron spectrometer for exploration missions Design, test and demonstrate instrument Fabricate prototype unit Compare with other techniques Key performance parameters: 0.5 to 50 MeV, 2.3 kg, 4W Phase II: ISS test flight demonstration design, fabricate and qualify ANS-ISS version deploy to ISS operate and acquire data for analysis Phase III: Operational Instrument for Manned Exploration

Space Radiation Environment Radiation risk to crew includes charged and neutral particle Estimate 25% of dose on ISS is due to neutrons Sources of charged particles in LEO include: GCR, Trapped protons and SEP Neutrons are generated through the interaction of these charged particles with matter : spacecraft/habitat, planetary surface or atmosphere Mixed radiation field includes all of the above

Space Radiation Environment (cont’d) Penetrating: no energy loss through direct ionization (tissue, shielding) High radiation weighting factor

ANS Gate and Capture Technique Thermal neutron

Gate and Capture Technique Boron-10 loaded plastic scintillator Lithium-6 doped glass scintillator

ANS Prototype (2014) Fiber array: 72×73 fibers 120 um dia. 1 mm spacing 15 cm length

ANS Prototype (2014)

ANS-ISS Engineering Model nPMT+nFEE

EM nPMT+nFEE signal separation Noise peak Neutron capture signal Beta continuum Alpha peak

Signal Response TRIUMF

AmBe Source Exposure Neutron Capture Signal Proton Recoil Signal n-capture p-channel Late signal p-channel

Comparison of 3 neutron source spectra

Gamma-ray Sensitivity (preliminary) n & p rates over 2 days

p-recent dist for B10 and Li6May 15, 2013

Neutron Angular Production

Neutron Spectra @ 45o – p + Al reaction

ANS GEN-II Geant4 Simulations Figure 1 ANS GEN-II diagram

Figure B2 Fraction events versus energy deposited in the ANS GEN-II detector volume for an incident neutron energy of 0.5 MeV before neutron capture.

Figure B3 Fraction events versus energy deposited in the ANS GEN-II detector volume for an incident neutron energy of 10 MeV before neutron capture.

Figure B4 Fraction events versus energy deposited in the ANS GEN-II detector volume for an incident neutron energy of 20 MeV before neutron capture.

Figure B7 ANS GEN-II optical photon response distribution for 0 Figure B7 ANS GEN-II optical photon response distribution for 0.5 MeV neutrons before neutron capture.

Figure B8 ANS GEN-II optical photon response distribution for 10 MeV neutrons before neutron capture.

Figure B9 ANS GEN-II optical photon response distribution for 20 MeV neutrons before neutron capture.

Figure 11 Geant4 simulation of ANS GEN-II neutron response versus energy and PMT optical photon current.

ANS GEN-II response for high-rate 98 MeV protons at 950 V. The fit is 1.09x106E-1.16.

ANS GEN-II response for AmBe source 30 mV at 950 V. The normalization is 7.11x107.

ANS-ISS Overview Deployment location: Internal Attachment method: Velcro Mission duration Primary: 6 months Secondary: ISS duration Launch configuration: Soft-stow Payload delivery : June/July2016 Mass: 11 lbs Volume: 5”x9”x10” Power: 7 W Voltage: 28 VDC Data Link: USB to ISS laptop Data Rate: 100 kbits/sec Memory: 4GBytes

Next Steps Evaluate and test the response matrix with mono-energetic beams of neutrons ( PTB Dec 2015 ): E = 0.024, 0.14, 0.25, 0.57, 1.2, 2.5, 5, 8 , 14, 19 MeV Conduct flight test on ISS to evaluate trigger efficiency and background in a space environment ( Aug 2016+ ) Compare measured spectrum with previous results (2016+ ) Next phase: Finalize design and qualify Tech-demo → operational instrument 5 year mission duration Validate data analysis approach Further Instrument Developments : Glass spheres replacing fibers Single set of four 1” PMTs

Backup Material

Response to edge trig; 1”x1”x2”

Comparison with He-3 Monitor

SPE Peak and Average values

Relevance of the accelerator exposures

Rate comparison SPE intensity IUCF intensity Threshold > 10 MeV Rate in protons/sec 1.4X1011 2.3X1010 2.6X109 6.0X108 IUCF intensity