Canadian High-Energy Neutron Spectrometry and Mixed-Radiation Field Studies B.J. Lewis and L.G.I. Bennett B.J. Lewis and L.G.I. Bennett Royal Military College of CanadaRoyal Military College of CanadaM. Smith, M. Zhang and H. M. Smith, M. Zhang and H. IngIngBubble Technology IndustriesBubble Technology IndustriesJSC Radiation Detection WorkshopJSC Radiation Detection WorkshopHouston, Texas Houston, Texas April 6April 6-- 7, 20067, 2006 Outline Canadian High-Energy Neutron Spectrometry and Mixed-Radiation Field Studies B.J. Lewis and L.G.I. Bennett Royal Military College of Canada M. Smith, M.Zhang and H. Ing Bubble Technology Industries JSC Radiation Detection Workshop Houston, Texas April 6-7, 2006 Slide 2 Outline - Canadian High-Energy Neutron Spectrometry System (CHENSS) - Mixed-Field Measurement • NFSE (bubble technology) • Tissue Equivalent Proportional Counter (TEPC) • Ionization chamber and SWENDI neutron remmeter • LIULIN (Si-based LET Spectrometer) • New technology: “DNA” dosimeter Slide 3 Neutron Dosimetryin Space Complex mixed charged particle and neutron environment exists in low Earth orbit (difficult to apply ground approaches) . Secondary neutrons (albedo neutrons from Earth’s atmosphere and production from spacecraft shielding) contributes to 10-30% of total dose equivalent • TEPC gives reliable doses <20 MeV (response to higher energies?) . Improve radiation dosimetry in space by accurately measuring the neutron fluence and neutron energy distribution • Measure/predict radiation dose to astronauts and optimize shielding scenarios Slide 4 Neutron Energy Distributions graph of Neutron Energy distribution with labels: Fluence in a bin (delta phi sub i) per logarithmic bin width (lnE sub i+1 - InE sub i) Normalized to unity for total fluence; Energy, eV; CERF Calibration Field; Aircraft at 35,000 ft; Wilson STS36 graph of Neutron Energy distribution with labels: Neutron Energy (MeV), E phi sub E (cm-2 s-1); Airline (Goldhagen); Accelerator (*0.0547); MIR Station (Lyagushin) Slide 5 CHENSS: Canadian High-Energy Neutron Spectrometry System image of CHENSS • Three gain settings provide desired dynamic range (1 – 100 MeV scale) • Internal 22Na (200 Bq) gamma-ray source and two green LED’s provide energy calibration and gain stability checks • Amplitude and shape signals, hit patterns, scalers and diagnostics recorded on two hard drives • 50 W power from alkaline batteries • Designed for autonomous operation in NASA GAS can on space shuttle G. Jonkmans et. al., Acta Astronautica 56, 975 (2005) Slide 6 CHENSS: Principle of Operation - Distinguishing Space Radiation Types of Space Radiation • cosmic rays (vetoed by outer plastic scintillator) • neutrons (detected by primary scintillator) • electrons and gamma rays (short pulses) diagram of CHENSS with labels: hydrogenous scintillating material (xylene + naphthalene) good n-gamma discrimination isotropic response reliable cross-sections; scattered neutron; neutron, cosmic ray, recoil proton Slide 7 Constraints Imposed by Space • Self-contained experiment with minimal human involvement • Scintillator is considered a hazardous payload by NASA • Significant temperature variations • Weight and power limitations • Physical size limitation • Data to be retrieved and examined after mission is completed Demands a conservative, reliable and rugged design Slide 8 Performance of Gelled Xylene Scintillator Neutron – Gamma Discrimination graph of performance with labels: Counts per Channel, Time (ns), gamma, neutron, gelled, liquid, contaminated Slide 9 CHENSS Design image of CHENSS image of Shuttle cargo bay design of CHENSS with labels: Total weight = 84.5 kg = 185 lbs; Batteries 20 kg; Top 18 kg Cylindrical support 4 kg; Pressure vessel 10kg; Electronics + wiring 10 kg; Experimental mounting plate; Visco-elastic scintillator Base 20 kg; Phototubes; Scintillating side panels 2.5 kg Slide 10 CHENSS Calibration at PTB image of CHENSS Calibration at PTB Slide 11 CHENSS Calibration at PTB . CHENSS irradiated by 2.5-, 5-, 14.8- and 19-MeV neutrons . Shadow-cone and blank-target backgrounds subtracted . gamma-ray events removed using pulse-shape analysis . Spectra unfolded using (5-inch cylindrical) BC-501A response matrix* . Fluence compared to independent PTB measurements *N. Nakao et. al., Nucl. Instrum. Meth. Phys. Res. Sect. A 362, 454 (1995) Slide 12 PTB Irradiation Spectra graph of PTB Irradiation Spectra with labels: Shape (channels); Energy (channels); 2.5 MeV; 3H(p,n)^3 He graph of PTB Irradiation Spectra with labels: Shape (channels); Energy (channels); 5 MeV; 2H(d,n)^3 He graph of PTB Irradiation Spectra with labels: Shape (channels); Energy (channels); 14.8 MeV; 3H(d,n)^4 He graph of PTB Irradiation Spectra with labels: Shape (channels); Energy (channels); 19 MeV; 3H(d,n)^4 He Slide 13 PTB and CHENSS peak) fluences normalized to CHENSS live- time Spectral Unfolding and Fluence Analysis graph with labels: x 10^ 6; Energy (MeV); Counts/MeV; 14.8 MeV; graph with labels: x 10^ 6; Energy (MeV); Counts/MeV; 19 MeV table: Neutron energy (MeV) phi sub PTB (10^5 neutrons/cm^2) phi sub CHENSS (10^5 neutrons/cm^2) 2.5 3.3(3) 2.0(4) 5.0 2.2(2) 1.9(4) 14.8 2.2(3) 2.2(2) 19.0 1.4(2) 1.3(2) PTB and CHENSS (peak) fluences normalized to CHENSS live-time Slide 14 Accelerator Facilities for High-Energy Neutron Calibration Radiation Protection Dosimetry (2004), Vol. 110, Nos 1-4, pp. 97-102 doi: 10.1093/rpd/nch195 QUASI-MONOENERGETIC NEUTRON REFERENCE FIELDS IN THE ENERGY RANGE FROM THERMAL TO 200 MeV R. Nolte1,*, M. S. Allie2, R. Bottger1, F. D. Brooks2, A. Buffler2, V. Dangendorf1, H. Friedrich1, S. Guldbakke1, H. Klein1, J.P Meulders3, D. Schlegel1, H. Schuhmacher1 and F. D. Smit4 1Physikalisch-Technische Bundesanstalt, P.O. Box 3345 D-38116 38023 Braunschweig, Germany 2Physics Department, University of Cape Town, Rondebosch, 7700, South Africa 3Institut de Physique Nucleaire, Universite Catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium 4iThemba Laboratory for Accelerator-Based Sciences, Somerset West, 7129, South Africa • PTB neutron beams up to 19 MeV • Higher energy beams at Louvain-la-Neuve, Belgium and iThemba, South Africa graph with labels: E sub n/MeV; (phi sub E/phi)/MeV^-1; 7Li(p,n); Louvain; iThemba Slide 15 Further Measurements for CHENSS •If possible, higher-energy (30 – 100 MeV) tests at Louvain-la-Neuve and iThemba(2006 +) • Airborne measurements at RMC, Kingston • Space mission(s) in the future Slide 16 Neutron Bubble Technology: Ground-Based Calibration at CERF image with labels: TEPC NFSE; SWENDI; Ionizatio Chamber; Bubble Detectors Slide 17 Nuclear Fragmentation Separation Experiment • Charged particle signature accompanies ~ 10% of events registered in BD - Agreement with FLUKA: charged hadron (p, pie) fluence rate one order of magnitude less than neutrons • BD-PND (260±50 pSv/PIC) vs CERF reference values (265±5 pSv/PIC) Slide 18 Mixed-Field Measurement: Aircrew Radiation Studies . ~>200 Flights (Portable Instruments) • Ionization Counter/Al sub 2 O sub 3 TLDs (low-LET) • SWENDI Remmeter/Bubble Detectors (high-LET) • Liulin-4N & 4SN (Si-based) LET Spectrometers • 2 Tissue Equivalent Proportional Counters (TEPC) Slide 19 Ionization Chamber (IC) image of Ionization Chamber graph of Energy dependence FHT 191 N with labels: Energy dependence; Energy in keV Slide 20 Extended Range Neutron Detector (SWENDI) diagram of detector wiht labels: He-3 Detector; Tungsten Shell; Polyethylene Moderator; Handle; Meter Connection graph with labels: Neutron Energy (MeV); Relative Respons; WENDI-II (Side); Eberline Hankins-NRD; Andersson-Braun (Side) Slide 21 LIULIN-4N and 4SN (GPS) LET Spectrometer image of Spectrometers Slide 22 Tissue Equivalent Proportional Counter image of BDs & TLD’s(under foam) graph for TEPC with labels: Neutron Energy (MeV); Dose Equivalent-to-Fluence [pSv cm2]; ICRP74; PTB 2000; NPL 2002; PTB 2002; PTB 2005 Slide 23 TEPC & IC + SWENDI: Pacific Routes graph with labels: YYZ - HNL; HNL - SYD; Antarctic (1); Antarctic (2); Antarctic (3); SYD - LAX; YVR - PEK; PEK - YVR; YYZ - HKG; HKG - YYZ; H*(10) (µSv); TEPC; SWENDI + IC Slide 24 0246810121416180246810 1999 RMC data; 2001-02 RMC data; Best fit f1 (Climax = 4004 counts/h/100, phi = 616MV); Best fit f2 (Climax = 3745 counts/h/100, phi = 1007 MV); Ambient Dose Equivalent Rate (µSvh-1) Normalized at 10.67 km; Vertical Cutoff Rigidity Rc (GV); f1; f2; SOLAR MAXIMUM REGION; SOLAR MINIMUM REGION; TEPC Vertical cutoff rigidity Rc (MV); Ambient dose equivalent rate (µSv/h) normalized to 10.6 km; RMC IC+SWENDI (Climax = 3744 counts/h/100, phi = 984 MV); ACREM IC+NMX (Climax = 4277 counts/h/100, phi = 498 MV); Best Fit ACREM IC+NMX; Best Fit RMC IC+SWENDI; Ionization Chamber + Neutron Remmeter; Poles; Equator; Upgraded to HAWK Slide 25 TEPC Limitations for Low-LET Analysis (in Mixed-Field) graph with labels: Missing dose; 60Co: Low-LET (y < 10µm); graph with labels: Neutrons (0.5 MeV) : High-LET (y > 10µm) TEPC unable to provide measurement below ~0.6 keV/µm due to electronic noise (S. Rollet et al., Rad. Prot. Dos 110 (2004) 833). •Fluka simulation to determine missing low-LET dose •Correction applied by manufacturer (60Co calibration) slide 26 LIULIN-4N Detector • Portable instrument needed (periodic checking of PCAIRE code) • Absorbed route dose (46 flights) • LIULIN vs TEPC (Reference Instrument) graph with labels: Elapsed Flight Time (min); Absorbed Dose per Interval (µGy/20 min); LIULIN; TEPC; Altitude graph with labels: D sub LIULIN (µGy); D sub TEPC (µGy) Slide 27 H*(10) Analysis for Liulin • Methodology (H=QD): (i) Q as a function of cutoff rigidity (ii) LIULIN LET spectral analysis (ICRP-60 Q(L)) Slide 28 Quality Factor vs Cutoff Rigidity graph with labels: Cutoff Rigidity, RC (GV); Quality Factor, Q sub HAWK; 03 Nov 03; 11 Nov 03; 21 Nov 03; 02 Dec 03; 09 Jan 03; 31 Oct 03; 01 Dec 03; 08 Dec 03; 01 Oct 03; 22 Sep 03; 29 Sep 03; 04 Oct 03; Linear Reg'n; Q sub HAWK(R sub C) = 2.36 - 0.06R sub C) graph with labels: Geographic Longitude (degrees); Geographic Latitude (degrees); Slide 29 LIULIN Spectral Analysis (ICRP-60 Q(LET)) table Channel LET Counts Quality Factor (ICRP60) H*(10) I (keV/um) n(i) in(i) Q(L) (uSv) 0 0.25 0 0 1.000 0.00 1 0.75 5643 5643 1.000 1.58 2 1.25 7642 15284 1.000 4.28 3 1.75 4190 12570 1.000 3.52 4 2.25 2816 11264 1.000 3.15 5 2.75 1657 8285 1.000 2.32 6 3.25 1200 7200 1.000 2.01 7 3.75 842 5894 1.000 1.65 18 9.25 68 1224 1.000 0.34 19 9.75 43 817 1.000 0.23 20 10.25 44 880 1.000 0.25 21 10.75 48 1008 1.080 0.30 22 11.25 30 660 1.240 0.23 23 11.75 30 690 1.400 0.27 196 98.25 0 0 29.080 0.00 197 98.75 0 0 29.240 0.00 198 99.25 0 0 29.400 0.00 199 99.75 0 0 29.560 0.00 200 100.25 0 0 29.963 0.00 201 100.75 0 0 29.888 0.00 202 101.25 0 0 29.814 0.00 203 101.75 0 0 29.741 0.00 253 126.75 0 0 26.647 0.00 254 127.25 0 0 26.595 0.00 255 127.50 0 0 26.542 0.00 Count Sum 27061 116243 24.50 Di(µGy)=9.33x10^-5·i·n(i) deltaL sub I= 0.5keV/µm H*(10)(µSv)=255sigmai=0 Q(L sub i) D sub i Slide 30 H*(10) with LIULIN vs TEPC graph with labels: Flight Date; 28-May-03 am; 28-May-03 pm; 29-May-03; 16-Jun-03; 18-Jun-03 am; 18-Jun-03 pm; 19-Jun-03; 15-Jul-03; 22-Jul-03; 31-Jul-03; 2-Aug-03 am; 2-Aug-03 pm; 5-Aug-03; 6-Aug-03 am; 6-Aug-03 pm; 8-Aug-03 am; 8-Aug-03 pm; 9-Aug-03; 10-Aug-03 am; 10-Aug-03 pm; 12-Aug-03 am; 12-Aug-03 pm; 13-Aug-03; 14-Aug-03; 22-Sep-03; 27-Sep-03; 29-Sep-03; 1-Oct-03; 4-Oct-03; 26-Oct-03; 27-Oct-03 (1); 27-Oct-03 (2); 27-Oct-03 (3); 1-Nov-03; 3-Nov-03; 10-Nov-03; 21-Nov-03; 23-Nov-03; 1-Dec-03; 2-Dec-03; 5-Dec-03; 8-Dec-03; 3-Jan-04; 5-Jan-03; 9-Jan-03; H*(10) (µSv); H*(10) TEPC H*(10) Liulin graph with labels: % Diff (TEPC) (%); YYZ - YVR; YVR - ICN; ICN - YVR; YVR - YYZ; YYZ - LAX; LAX - SYD; SYD - LAX; LAX - AKL; SYD - JBG; JBG - SYD; JBG - SYD; YKG - YYZ; YYZ - YVR; YVR - PEK; YYZ - HKG (P); HKG - YYZ; YYZ - YGK; YYZ - YVR; YVR - ICN; ICN - SIN; SIN - ICN; YYZ- LHR; LHR - YYZ; YYZ - YGK; YGK - YYZ; YYZ - MUC; MUC - HAJ; HAJ - MUC; MUC - YYZ; YYZ - YGK; Flights; Total Ambient Dose Equivalent (µSv); H*(10)TEPC (µSv); H*(10) Liulin 4N (µSv); H*(10) Liulin 4SN (µSv) Slide 31 Novel New Technology: DNA Dosimeter . Polymeric biosensor to detect double strand DNA (dsDNA) breaks induced by radiation (biologically-relevant dosimeter for mixed-field measurement) • Captor (nanotechnology) of known amounts of target dsDNS (predefined length with specific terminal sequence tag) • Detector (optically-clear hybridization chamber) to read fluorescent signal of cleaved-target dsDNA • Correlated against biological dosimetry and compared to physical dosimetry for mixed fields data flow with labels: 420 nm; 572 nm; 420 nm; Tag sequence; Tag complementary probe; Wash; Captor; Captor exposed to radioactivity; Detector Slide 32 Conclusions . CHENSS can be used for high-energy neutron spectral measurement • Currently being calibrated at accelerator facilities . NFSE shows promise for n measurement with bubble technology in mixed-field . Mixed-field measurements made at jet altitudes • Good comparison of H*(10) by summing low (IC) and hight (SWENDI) LET components with TEPC measurement • Good comparison of H*(10) between TEPC and LIULIN . Novel technology: biologically-relevant “DNA” dosimeter Slide 33 Acknowledgements . Funding support from the Life and Physical Sciences Directorate of the Canadian Space Agency (CSA) and Transport Canada . R. Nolte and S. Rottger of the Physikalisch Technische Bundesanstalt (PTB) . Thanks are also due to: H.R. Andrews, E.T.H. Clifford, V.T. Koslowsky and R. Noulty (BTI), M. Boudreau (RMC), C. Vachon (NRC) and L. Tomi (CSA) Slide 34 Cosmic-Ray Detector (anti-coincident shield, 100% efficient) diagram of detector with information: Plastic scintillating panel • 1cm thick, creates strong signal • 8 panels provide full coverage • openings for cables and mechanical fasteners • cushioned with VITON gaskets and caulking from metal surfaces • no fasteners or tapped holes(no dead areas) Phototubes • one per panel • cement to plastic • withstand 20g Cross-sectional A-A