In-Situ Estimation of Cosmic Radiation Exposure During High-Altitude, Long-Distance Commercial Flights

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1 In-Situ Estimation of Cosmic Radiation Exposure During High-Altitude, Long-Distance Commercial Flights Bhaskar Mukherjee Deutsches Elektronen-Synchrotron, Hamburg, Germany and Department of Plasma Physics The University of Sydney, Australia Invited Lecture, WUT, Poland, 15 December 2005

2 JUSTIFICATION OF OUR RESEARCH

3 INTRODUCTION Earth s atmosphere is continuously bombarded with ionising radiation of galactic and solar origin, known as COSMIC RAYS. The cosmic ray field is primarily made of high energy protons, electrons, gamma rays and heavy charged particles. Cosmic ray particles are trapped by the geomagnetic field, resulting in the production of Van Allen Belt. The air crew and passengers of jet liners flying at high altitudes as well as astronauts are exposed to cosmic radiation field. A large number of measured and theoretically predicted values of the in-flight radiation doses for Northern Hemisphere flight routes are now available.

4 INTRODUCTION (contd.) On the other hand, for the Southern Hemisphere, very little data has been published. Since 1997 we have been systematically assessing the cosmic radiation doses from international return flights originating from Sydney using various active and passive dosimeters. This paper will present some important results of on-board radiation dosimetry measured during a Round-the-Globe flight originating from Sydney (33( o 52 S, 151 o 13 E).

5 RESULTS OF OUR INVESTIGATION HAVE BEEN PUBLISHED IN PEER REVIEWED JOURNALS

THE ORIGIN OF COSMIC RAYS Sun Van Allen Belt Geomagnetic Field Earth Solar Wind SOLAR WIND => Protons with a broad energy spectrum (10 kev-1000 MeV) produced in solar interior and ejected into space

6 THE ORIGIN OF COSMIC RAYS Sun Van Allen Belt Geomagnetic Field Earth Solar Wind SOLAR WIND => Protons with a broad energy spectrum (10 kev-1000 MeV) produced in solar interior and ejected into space The low energy protons are trapped by the geomagnetic field, known as the VAN ALLEN BELT The reminiscent higher energy protons interact with the air molecules in the upper atmosphere producing secondary particles, known as the (solar) Cosmic Rays.

7 PROPERTIES OF COSMIC RAYS Abundance of Elements in Solar System and Galactic Cosmic Ray (GCR) Effects of Solar Cycle on the Galactic Cosmic Ray (GCR) Spectrum

8 COSMIC RAYS AND SOLAR CYCLE

9 THE VAN ALLEN BELT Earth s Own Radiation Shield Earth Mirror point Particles oscillate Geomagnetic Field Trapped Charged Particles Mirror point The geomagnetic field traps the impinging cosmic ray (charged) particles. The trapped charged particles oscillate between the mirror points located near the geomagnetic poles. The donut shaped trapped charged particle field around the earth due to geomagnetic field is called the Van Allen Belt.

This results in the production of the Auroras.

10 THE AURORAS N Van Allen Belt Van Allen Belt S The geomagnetic field is weaker in the polar regions. Hence, the intensity of Cosmic Rays is higher near the poles. This results in the production of the Auroras. Causing a higher radiation exposure to air traffic operating near the polar regions. Aurora Borealis Aurora Australis

11 HUMAN ACTIVITES IN SPACE Space Shuttle ~ km Commercial jetliners: 9-14 km

12 VARIATION OF ATMOSPHEREIC NEUTRON FLUENCE WITH ALTITUDE AND LATITUDE (Data taken from XILINX website) (1000 feet = km)

13 ACCELERATOR RADIATION SHIELDING (A COSMIC RAY PARADIGM) Atmospheric Depth = Shield Thickness

National Laboratory (BNL) was named as Cosmotron The Lateral

14 COSMIC RAY PHYSICS WERE USED IN EARLY PARTICLE ACCELERATOR SHIELDING DESIGN The 6 GeV Proton Synchrotron (1961) of Brookhaven National Laboratory (BNL) was named as Cosmotron The Lateral Concrete Shielding of the BNL Cosmotron was designed using the Cosmic Ray Model

Solar activity (inversely) In Aircraft Fast Neutrons (generated in upper atmosphere) Gamma rays

15 CHARACTERISTICS OF THE RADIATION FIELD In Space/LEO (Low Earth Orbit) Fast Protons Secondary Neutrons (generated in spacecraft s shell) Gamma rays Exposure Depends on Flight duration, Position in space, Solar activity (inversely) In Aircraft Fast Neutrons (generated in upper atmosphere) Gamma rays Electrons Exposure Depends on Flight altitude, Duration, Geographical latitude, Solar activity (inversely)

16 IN-FLIGHT RADIATION DOSIMTERY The neutron and gamma doses were recorded in large haul passenger aircraft: Boeing or similar type The dosimeters were carried in hand luggage and placed above the passenger seat located at the centre of the fuselage.

17 RADIATION DOSIMETERS USED IN OUR INVESTIGATON TLD (Los Alamos) DIS-1(Direct Ion Storage) TLD (β,( γ,, N) Bubble (Neutron) Dosimeter TLD (N-Albedo) TLD (Aviation Dosimeter, Electronic (Gamma) Developed by us at Sydney Dosimeter University

18 SUPERHEATED BUBBLE DOSIMETER Model: BD 100R, Manufacturer: BTI, Canada Neutron sensitivity: 1 bubble per 450 nsv at 20 o C Gamma sensitivity: negligible Neutron energy response: 100 ev - 20 MeV Calibration: 241 Am/Be neutrons (5.5 MeV)

19 ELECTRONIC PERSONAL DOSIMETER Model: RAD-50S, Manufacturer: Rados Technology, Finland Gamma energy response: 60 kev-7.5 MeV (extrapolated) ± 20% Neutron sensitivity: negligible Dose rate linearity: better than ± 15% Operational temperature range: - 20 to + 50 o C

DOSIMETER CALIBRATION WITH FAST NEUTRONS AT BRITISH

facility is also used for space radiation experiments

for dosimeter calibration has been developed A Bonner

20 DOSIMETER CALIBRATION WITH FAST NEUTRONS AT BRITISH COLUMBIA PROTON THERAPY FACILITY The proton therapy facility is also used for space radiation experiments (SEU study) A high energy neutron irradiation set up for dosimeter calibration has been developed A Bonner sphere spectrometer was used to evaluate neutron energy distribution

RESPONSE OF BD-100R DOSIMETERS TO HIGH ENERGY NEUTRONS WAS EVALUATED 1) With Neutrons from CERN EU High-Energy Reference Field (CERF)* 2) With Neutrons produced

21 RESPONSE OF BD-100R DOSIMETERS TO HIGH ENERGY NEUTRONS WAS EVALUATED 1) With Neutrons from CERN EU High-Energy Reference Field (CERF)* 2) With Neutrons produced by 500 MeV protons bombarding an Iron-Target (simulated Beam-Spill ) at the TRIUMF Cyclotron Facility Vancouver, Canada * M. Hajek and T Berger, ATI/08/2001/FLY-1

22 DOSIMETER CALIBRATION AT A K1200 SUPER- CONDUCTING HEAVY ION CYCLOTRON Foot print of the K1200 Superconducting cyclotron of Michigan State University, USA Dosimeter Irradiation Port with Heavy Ions

23 COSMIC RAY NEUTRON SPECTRUM 1.2E+01 Fluence/Lethergy: [arb. unit] 1.0E E E E E+00 Typical cosmic ray neutron spectrum at upper atmosphere 0.0E E E E E E E E E E E E E E+04 Neutron Energy: [MeV] Neutron spectra near a thick lead target bombarded with 500 MeV protons at TRIUMF The spectrum was measured with a set of 9 Bonner Spheres Φ : [cm -2 s -1 na -1 /Bin/MeV] 1E+07 1E+06 1E+05 1E+04 1E+03 1E+02 1E+01 1E+00 1E-01 1E-02 1E-03 1E-04 1E-05 1E-08 1E-07 1E-06 1E-05 1E-04 1E-03 1E-02 1E-01 1E+00 1E+01 1E+02 1E+03 Bin energy: [MeV]

24 THE ITINERARY

25 THE FLIGHT ROUTES

26 AIRPORT AND FLIGHT DETAILS

27 RESULTS AND DATA ANALYSIS (1) H = H G + k -1 H N + H E (1) H E ~ H N (2) Where: H G = Gamma DE recorded with Electronic Dosimeter H N = Neutron DE recorded with Bubble Dosimeter k = Neutron DE Correction factor (High Energy Neutrons) for BD-100R Bubble Dosimeters evaluated at CERF and TRIUMF H E = Electron Dose

28 RESULTS AND DATA ANALYSIS (2) The total Dose Equivalent for each flight route calculated with the CARI-6 Code developed by the FAA is shown in Column 6

29 RESULTS: INTERCOMPARISON DE: [micro Sv] H (This Work) H (CARI6) 0.0 SYD-SFO- ORD-LAN LAN-ORD- YVR YVR-ORD- VIE VIE-ATH ATH-VIE- BKK-SYD Results show good agreement within an error margin of ± 5%

30 SOME MOST RECENT RESULTS Date of Flight: 11 December 2005 Route: Hamburg (Germany) Warsaw (Poland) Distance: 900 km Flight Duration: 1h 50min Total Dose Measured: 9.6 micro Sv Total Dose Calculated: 9.0 micro Sv

31 SUMMARY: On-board Radiation Dosimetry originated from Sydney, Australia Dosimeters used Neutron Bubble Dosimeter (BD100R) Electronic Pocket (gamma) Dosimeter (RAD50) Home made Aviation Dosimeter (TLD-600, TLD-700) Procedures Flight altitude and duration were recorded Electronic Pocket Dosimeter was read immediately after arrival Bubble dosimeters were assayed ca 12 hours after arrival TLDs were evaluated with a hot finger type Readout Instrument

32 SUMMARY AND CONCLUSION This work highlights a comprehensive study of the round-the- world, in-flight, cosmic radiation dosimetry in the southern hemisphere. During flights the gamma ray and neutron dose equivalents were recorded with an Electronic (PIN diode) dosimeter and superheated bubble dosimeters respectively. High-Energy ( > 20 MeV) response of the neutron Bubble dosimeters were evaluated with neutrons from high energy accelerators at CERN and TRIUMF (Tri University Meson Factory, Vancouver, Canada). The total in-flight dose equivalent was also calculated from flight parameters and current heliocentric potential using the CARI-6 Code obtained from the US Federal Aviation Administration (FAA).

33 SUMMARY AND CONCLUSION (contd.) The results of this work agrees with the dose equivalent calculated using the CARI-6 Code (within an uncertainty of +/ 5%). The major prospective applications of this experimental investigation are as follows: Assessment radiation exposure to frequent flying passengers. Evaluation of the optimum flight plan in order to minimize the radiation exposure to female flight attendants. Development of the radiation exposure reduction technique for the future long haul, high-altitude passenger airliners.

34 THANK YOU For your Attention For further queries please contact Bhaskar Mukherjee:

Measuring dose equivalent in an aviation environment using PIN diodes

Measuring dose equivalent in an aviation environment using PIN diodes Alex Hands Neutron Users Club meeting, NPL Wednesday 4 th November 29 1 Background Cosmic Rays consist primarily of protons and alpha