Neutron Applications/ 1 Introduction/ Neutron Sources/Neutron Detectors

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1 Neutron Applications/ 1 Introduction/ Neutron Sources/Neutron Detectors G. Viesti Dipartimento di Fisica ed Astronomia, Università di Padova II Andean School on Nuclear Physics, Bogotà, Colombia October 2014

2 Introduction: the use of neutrons in science and technology 2

3 Most popular applications of neutrons Neutron Activation Analysis Boron Neutron Capture Therapy 3

4 What are neutrons used for? Condensed-matter physics, materials science and chemistry Examination of the structure of new materials, Storing of hydrogen in metals (renewable energy sources). Analysis of parameters in polymers. Colloid research in pharmaceuticals, food industry and medicine. Biosciences Biological materials, naturally rich in hydrogen and other light elements, are ideal samples for analysis with neutrons. Cell Membranes Proteins Virus Investigations Photosynthesis in Plants Engineering sciences Since neutron diffraction is non-destructive, it is ideal for the analysis of different technical phenomena in materials. Visualization of residual stress in materials (example: railway rails). Hardening and corrosion phenomena in concrete. Inhomogeneity and trace elements in materials. 4

5 Neutron Sources 5

6 252 Californium Total Half-live: 2.7 years Half-live for alpha decay: 2.7 years (E α =6.117 MeV) Half-live for spontaneous fission: 85.5 years Specific activity: 500 µci / µg (6.2 x 10 5 fission / µg) Neutron multiplicity: 3.7 (<E n >=2.35 MeV) Gamma multiplicity: about 10 (80% with energy E<1. MeV) Sealed sources, double stainless steel container. Typical geometry (Savannah River type) : right cylinder, 3.7 cm long, 0.92 cm dia. The 252 Cf is contained in a ceramic pellet (1 mm 3 volume) placed inside the stainless steel container. 6

7 252 Cf fission fragments mass distribution 7

8 X-rays from fission fragments 8

9 GAMMA RAYS FROM 252 Cf 9

10 Neutron emission from 252 Cf 10

11 Neutron (α,n) sources Be(α,n) 11

12 (α,n) sources 12

13 Neutron Spectrum from the AmBe source 13

14 Gamma rays from (α,n) sources 14

15 Sealed Portable Neutron Generators Courtesy of D. Chichester 15

16 NEUTRON SOURCE REACTIONS DROSG drosg2000.html See also manfred.drosg/drosgv10.htm 16

17 What is an Electronic Neutron Generator? A device containing a small linear accelerator (1-5 cm beam length) that produces neutrons as a result of DD or DT fusion by accelerating D and/or T ions into a metal hydride target that is loaded with D and/or T atoms Other types of instruments have also been designed to generate neutrons including inertial electrostatic confinement (IEC) devices and plasma focus devices however, these have yet to reach commercial maturity due to issues related to complexity, size, cost, operating lifetime, and reliability Neutron generators have several distinct components, in some designs these are separate in others some are integrated together Neutron Tube - Ion Source - Gas Reservoir - Accelera7ng Gap - Ion lens - Target - HV insulator - Vacuum envelope HV Housing - Tube moun7ng - HV insula7on - Electrical connec7ons to neutron tube HV Power Supply - HV for accelera7on IS Power Supply - Provides current for ion source R Power Supply - Provides current for reservoir Control System - Operates device & adjusts performance

18 Neutron Tube - Ion Source - Gas Reservoir - Accelera7ng Gap - Electrosta7c lenses - Target - HV insulator - Vacuum envelope Copper Tube A Neutron Tube Ion Source Accelera7ng Gap HV Insulator Target Materials Ceramics & Glass Steel, kovar OFHC Copper Hydride metals Joining Glass-to-metal seals Ceramic-to-metal brazes Metal-to-metal brazes Ultrahigh vacuum Impurities Cleaning parts, bake out off-gassing Gas Reservoir Electrosta7c Lenses

Depiction of an ENG the Zetatron Ion Source Power Supply (2 to 5 kv) (1 to 20k Hz) Magnet (~ 500 G)

Operation: 1) Apply high voltage to target/lens assembly, electric field gradient is established in

Apply voltage to ion source anode, glow discharge evolves into plasma, molecular ions formed (~5 µs) 4)

19 Depiction of an ENG the Zetatron Ion Source Power Supply (2 to 5 kv) (1 to 20k Hz) Magnet (~ 500 G) Tube is filled with deuterium & tritium gas (~1-10 mtorr) Reservoir Power Supply (1-3 A) Plasma GND Operation: 1) Apply high voltage to target/lens assembly, electric field gradient is established in accelerator 2) Apply reservoir current, hydride getter heats up, tube fills with gas (~15 seconds) 3) Apply voltage to ion source anode, glow discharge evolves into plasma, molecular ions formed (~5 µs) 4) Ions escaping ion source are accelerated to target Ions Secondary Electrons High Voltage Power Supply (-50 to 150 kv)

20 Neutron generator patent for medicine Patent for a semi- sealed neutron generator 1 st Patent for a sealed- tube neutron generator (Well Surveys, Inc.) History ENGs are 1 st used for pulsed- reactor physics Kaman Corp. patents the 3045 neutron tube for the A- 711 ENG Dresser patents a down- hole miniature Van de Graff accelerator First sealed tube ENG for associated par7cle imaging LBNL: interest rekindled in RF ion sources Chadwick discovers the neutron Oliphant discovers 2 H(d,n) 3 He fusion Penning patents an open-tube neutron generator First experiment s of DT fusion Beginning of oilfield well logging with ENGs Reifenschweiler describes RF ion source for neutron generator Innova7on Engineering Refinement (life7me, reliability, yield, cost) Controlatron neutron generator developed for Apollo program and lunar explora7on France teams with Philips, forms SODERN to support nuclear weapons program (first detona7on in 1960) Commercial sealed- tube neutron generators emerge: Philips/Norelco SERL General Electric Kaman SAMES Texas Nuclear Commercial use of ENG in raw- material analyzer All- digital control system for mul7- purpose ENG Discussion of using field desorp7on as an ion source Mars Science Laboratory with an ENG arrives on Mars? Experiments using pyroelectricity as a high- voltage source are popularized

21 Categories of Neutron Generators ENG Category Logging-While-Drilling (LWD) Primary Applications Oilfield drilling measurements Key Performance Criteria Extreme ruggedness and small diameter Wireline (W) Portable (P) General Purpose (GP) Active Cooling (AC) Associated Particle (AP) Oilfield well surveys Security, science Bulk material analysis, security, medicine, general science Bulk and trace material analysis, security, radiation effects testing, general science Security Extreme ruggedness and small diameter Light weight (~ l0-15 kg), small overall size, and operational flexibility Operational flexibility, no active cooling Neutron yield Associated particle detector performance, beam spot size (imaging)

22 Today s Commercial ENGs GENIE 35: 2 x 10 9 n/s DT Mul7ple systems, typical opera7ng life7mes of 100 hours ING-03: 3 x n/s ING-07: 1 x 10 9 n/s GENIE 16C: 1 x 10 8 n/s DT DD- 108: 1 x 10 8 n/s DD (no representa7ve photo available) P 385: 3 x 10 8 n/s DT (no representa7ve photo available) MP320: 1 x 10 8 n/s DT D- 711: 2 x n/s DT API 120: 2 x 10 7 n/s DT

23 Applications - Bulk Material Analysis Likely to be the largest industrial market for ENGs (outside the oilfield) over the next 5 years Spurred by pressures to avoid and eliminate the use of 252 Cf Examples Coal, the use of 14.1 MeV neutrons allows direct measurement of oxygen (energy & BTU) Cement Mineral ores see ref/neutron-elementalanalysis_33.html SODERN Coal Analyzer SODERN Cement Analyzer

water ENG is a Russian contribution, Schlumberger has also published interest in

24 Applications Exotic: Extraterrestrial Soil Analysis NASA has incorporated ENG into the Mars Science Laboratory Scientific objectives are primarily centered on detection of water ENG is a Russian contribution, Schlumberger has also published interest in supporting these missions (Mars, Moon, Venus) NASA Mars Science Laboratory Space Research Ins7tute, Russia

Dynamic Albedo of Neutrons The Dynamic Albedo of Neutrons (DAN) is an

, adsorbed water, hydrated minerals) in a shallow layer (~1 m) of Mars' subsurface

25 Dynamic Albedo of Neutrons The Dynamic Albedo of Neutrons (DAN) is an active/passive neutron spectrometer that measures the abundance and depth distribution of H- and OH-bearing materials (e.g., adsorbed water, hydrated minerals) in a shallow layer (~1 m) of Mars' subsurface along the path of the MSL rover. In active mode, DAN measures the time decay curve (the "dynamic albedo") of the neutron flux from the subsurface induced by its pulsing 14 MeV neutron source. (Astrobiology 8, p.605, 2008). 25

26 Neutron Detectors 26

27 3 He proportional counters 27

28 3 He proportional counter 28

29 3 He proportional counter 29

30 Neutron Background! 30

31 Liquid scintillators with pulse shape discrimination 31

32 Discovery of pulse shape discrimination 32

33 Figure of Merit 33

34 PSD WITH FAST DIGITIZERS PSD=(Qlong-Qshort)/QLong 34

35 New Scintillators EJ-301 liquid scintillator (NE213 type) toxic, low flash point (26 C) EJ-309 liquid scintillator non toxic, higher flash point (144 C) EJ Plastic with PSD PSD with EJ

36 Comparison of scintillators 36

37 ROLE OF THE FAST DIGITIZERS 37

Neutron Sources Fall, 2017 Kyoung-Jae Chung Department of Nuclear Engineering Seoul National University

Neutron Sources Fall, 2017 Kyoung-Jae Chung Department of Nuclear Engineering Seoul National University Neutrons: discovery In 1920, Rutherford postulated that there were neutral, massive particles in