LOW ENERGY ELECTRON ACCELERATORS APPLICATION

LOW ENERGY ELECTRON ACCELERATORS APPLICATION V. Shvedunov Skobeltsyn Institute of Nuclear Physics Lomonosov Moscow State University 10 November 2011

Electron accelerators in the range 0.5 100 MeV Some applications use bremsstrahlung (X-rays) radiation, some electron beam. For X-rays ( x) I = I exp µ 0 For electrons Different mechanisms of radiation interaction with matter are used for different applications - at level of molecules, atoms, nuclei

ACCELERATORS

Electron accelerators in the range 0.5 5 MeV in most cases are built as direct current accelerator with max beam power up to several hundred kw and efficiency 80-90%. Basic suppliers: Nissin High Voltage Ion Beam applications Budker Institute Efremov Institute

Examples of electron accelerators in the range 0.5 5 MeV ELV (Budker Institute) 0.2 2.5 MeV, up to 500 kw Nissin HV 5 MeV,150 kw

Examples of electron accelerators in the range 0.5 5 MeV DYNAMITRON (IBA)

Electron accelerators in the range 5 10 MeV in most cases are built as RF standing wave or traveling wave linear accelerator (linac) with max beam power up to hundred kw and efficiency 20-30%. Traveling Wave (TW) RF waveguide Standing Wave (SW)

CUT VIEW OF STANDING WAVE ACCELERATING STRUCTURES Side coupled On-axis coupled

Examples of electron linacs in the range 5 10 MeV TitanBeta SW linac 10 MeV, 25 kw Mitsubishi Heavy Industries TW linac 10 MeV, 25 kw IMPELA SW linac 10 MeV, 50 kw SureBeam SW linac 5 MeV,100 kw

Example of electron accelerator in the range 5 10 MeV - recirculating RF cavity accelerator Rhodotron, IBA 5-10 MeV up to 700 kw

In some applications cheap betatrons are used in the range 3 25 MeV Betatron principle 10 MeV betatron for IORT (Tomsk) 3-7.5 MeV betatrons (Tomsk)

Electron accelerators in the range 10 25 MeV in most cases are also built as RF linear accelerator with max beam power up to tens kw and efficiency 20-30%. In some cases microtrons and betatrons are used. Microtron

Examples of electron accelerators in the range 10 25 MeV MEVEX, Canada, 35 MeV linac for isotopes production Varian 25 MeV Clinac 20 MeV circular microtron, Indore, India

Electron accelerators in the range 25 100 MeV in most cases are built as multisections RF linear accelerator or as race-track microtron (RTM).

Examples of electron accelerators in the range 25-100 MeV Scanditronix medical RTM MM-50 Danfysik 53 MeV RTM Research Instruments 100 MeV linac

APPLICATIONS

Electron accelerators application for material processing, sterilization, desinsection Chemical and biological effects at molecules level are produces by ~ev energy electrons. Initial high electrons energy is required to penetrate inside the material. Productivity: m t P = η D beam To increase penetration electron energy can be converted to X-rays energy at bremsstrahlung target, but efficiency of conversion in energy range below 10 MeV is below 10%, so high power electron beams are required.

Dose requirements for various radiation effects and productivity for 10 kw electron beam power 1 Gy = 1 J/kg Radiation effect Dose requirements Productivity Sprout inhibition (potatoes, onions) 100-200 Gy ~200-100 tons/hour Insect control (grains, fruits) 250-500 Gy ~80-40 tons/hour Fungi and mould control 1-3 kgy ~10-3 tons/hour Bacterial spore sterilization 10-30 kgy ~2-0.7 tons/hour Polymerization of monomers 10-50 kgy ~2-0.4 tons/hour Anthrax killing 50-100 kgy ~400-200 kg/hour Modification of polymers 50-250 kgy ~400-80 kg/hour Degradation of cellulose materials 100-500 kgy ~200-40 kg/hour Topaz coloring 10-200 MGy ~1-0.05 kg/hour

Irradiation facility based on Dynamitron (IBA) Rated Voltage Rated beam current 550 kev 70/100/160 ma 800 kev 70/100/160 ma 1 MeV 60/100 ma 1.5 MeV 40/65 ma 2.5 MeV 40 ma 3 MeV 34/50 ma 4.5 MeV 20/34 ma 5 MeV 10/20/34 ma

Structure of 10 MeV/25 kw irradiation facility http://www.mhi.co.jp/hmw/melbis/structure-e.html

SINP MSU experience in design, construction and application of electron accelerators for radiation technologies

SINP MSU 60 KW, 1.2 MEV COMPACT CW LINAC FOR RADIATION TECHNOLOGIES One- Section Two- Sections Beam energy 0.6 MeV 1.2 MeV Beam current 0 to 50 ma 0 to 50 ma Maximum beam power 30 kw 60 kw Length 0.8 m 1.3 m Gun/klystron high voltage 15 kv 15 kv Plug power consumption ~75 kw ~150 kw Electrical efficiency ~40% ~40%

SOME CURRENT APPLICATIONS OF 1.2 MEV COMPACT CW LINAC 1. Test of spacecraft elements (solar batteries etc) for radiation effects 2. Source of high dose rate X-rays radiation 3. R&D for radiation technologies Thermo shrinkable polyethylene film dimensions decrease after different doses. Optimal dose 120 kgy. Intensive bremsstrahlung X-rays source (30 Gy/s at average energy 300 kev)

SINP MSU COMPACT CW LINEAR ACCELERATOR FOR RADIATION TECHNOLOGIES WITH LOCAL RADIATION SHIELDING CWL-1-25 Under construction. Beam energy 1 MeV Average beam current 25 ma Average beam power 25 kw Operating frequency 2450 MHz Klystron average power 50 kw Wall plug efficiency 30% Beam scanning width 80 cm Accelerator dimensions 470 x 784 x 1375 mm 1) 1)Without output horn and power supply Accelerator is able to provide operation of thermo shrinkable polyethylene film facility with productivity up to 10000 tons/year

SINP MSU 10 MeV TECHNOLOGICAL LINAC Beam energy 10 MeV Pulsed beam current 430 ma Average beam power 15 kw Operating frequency 2856 MHz Klystron pulsed power 6 MW Klystron average power 25 kw Wall plug efficiency 20% Beam scanning width 80 cm

I Energy spectrum, beam image and beam profile 0.08 0.07 0.06 0.05 I(45)/I(0) 0.04 0.03 0.02 0.01 0-0.01 0 2 4 6 8 10 12 E (МэВ) 180 160 140 120 100 80 60 40 20 0-3 -2-1 0 1 2 3 y (mm)

SOME CURRENT APPLICATIONS OF 10 MEV LINAC 1. Test of spacecraft elements (solar batteries etc) for radiation effects 2. R&D for radiation technologies Example of possible application gemstones colorization

SINP MSU 10 MeV TECHNOLOGICAL LINAC Proposal Pulsed Linear Accelerator PLA-10-15H Pulsed Linear Accelerator PLA-10-15V Beam energy 10 MeV Pulsed beam current 430 ma Average beam power 15 kw Operating frequency 2856 MHz Klystron pulsed power 6 MW Klystron average power 25 kw Wall plug efficiency 20% Beam scanning width 80 cm Accelerator dimensions 470 x 784 x 1375 mm 1) 1) Without output horn and power supply

CARGO INSPECTION AND RADIOGRAPHY X-rays produced by electrons at bremsstrahlung target are used in both applications. X-rays are attenuated by inspected object and registered by X-rays detectors or by film. Basic processes responsible for X-rays attenuation

Cargo inspection. 40 mln. sea containers per year move in the word.

Cargo inspection - goals. 1. Detection of contraband. 2. Detection of fissile and radioactive materials. 3. Detection of explosive and drugs. Different approaches are necessary for each problem, but in all cases electron accelerators are used or can be used.

Typical dimensions. Required speed of development: 0.5 m/s

Main components of cargo inspection complex

Basic companies providing equipment and complexes for cargo inspection are: Varian Medical Systems (USA) Smiths Detection (UK) Nuctech (China) L-3 (USA) Rapiscan (USA) SAIC (USA) AS&E (USA).. Several other companies are working in this direction

Single energy bremsstrahlung X-rays do not permit to evaluate atomic number and can produce only gray picture 10.00 Uranium µ/ρ (cm 2 /g) 1.00 0.10 Iron Nitrogen Co 60 Bremsstrahlung spectrum 0.01 0.1 1.0 10.0 E (MeV)

Dual energy bremsstrahlung X-rays do permit to evaluate atomic number and can produce color picture 10.00 Uranium µ/ρ (cm 2 /g) 1.00 0.10 Iron Nitrogen Bremsstrahlung spectra 0.01 0.1 1.0 10.0 E (MeV)

The most widely used are X-ray sources from Varian Medical Systems. Linatron-Mi is dual energy X-Ray source fed by magnetron

Nuctech (China) also produces 6/9 MeV dual energy X-Ray source fed by magnetron

Design by SINP MSU team of 3/6 MeV linac with interlaced energies for cargo inspection X-rays head Beam energy 3.5/6 MeV Dose rate at 1 m 0.2 2 Gy/min Operating frequency 2856 MHz Pulse repetition frequency 50 400 Hz Accelerator dimensions 1000x600x900 mm Accelerator weignt 900 kg 1) 1) Including local radiation shielding Control console

Energy spectrum in interlaced energies mode 600 500 400 Iav (na) 300 200 100 0 0 1 2 3 4 5 6 7 8 E (MeV) Low High Beam spots diameters are well below 2 mm Scale: 1 square= 1 1 mm

ACCELERATOR WITH FAST MAGNETIC ENERGY SWITCHING FOR CARGO INSPECTION (PROPOSAL) RTM Parameters Beam energies Operating frequency End magnets field Injection energy Pulsed RF power Repetition rate, max RTM dimensions 1) RTM weight 1) 3.5, 6, 9 MeV 2998 MHz 0.63 T 25 kev <2 MW 1000 Hz 650x200x150 mm <60 kg (1) electron gun, (2) linac, (3), (4) end magnets, (5) fast extraction magnets, (6) extracted beam, (7) RTM focusing lens, (8) beam current monitor, (9) extracted beam quadrupoles, (10) bremsstrahlung target, (11) radiation shielding with collimator.

Radiography http://niiefa.spb.ru/ Film Digital Introscopic system resolution (detector size 2x2 mm) Accelerator energy, MeV 6 8 10 15 Density resolution, % 1 1 1 1 Spatial resolution, mm 2 2 2 3 Penetrability for steel, mm 200 250 290 350

Varian linac for radiography

Nuclear reaction based applications Elemental analysis Isotopes production Explosive detection

Photonuclear reaction thresholds Eth (MeV) 25 20 15 10 (γ,p) (γ,n) 5 0 0 20 40 60 80 100 Z Electron beams with energy higher than 10 MeV are necessary to knock out nucleons from nucleus

Photoneutron reaction at different nuclei 12 C + γ --> 11 C + n 40 Ca + γ --> 39 Ca + n 208 Pb + γ --> 207 Pb + n

Photo activation technique method of elemental analysis using photonuclear reactions.

Nuclei level structure is unique fingerprints permitting to detect specific elements in very low quantities Level structure of gold isotope 196 Au. Level with energy 595.66 kev has half life period 9.6 h. 196 Au can be produced in this isomeric state via photoneutron reaction at stable isotope 197 Au. In this way gold content in ore can be defined with high sensitivity - better than 1 g/ton

Photo activation technique

Photo activation technique Gamma ray spectrum obtained with Ge detector

Accelerators for photo activation technique Electron beam parameters: Beam energy from ~ 10 MeV to ~30 MeV Beam average current from ~100 µa-1 ma Conversion to bremsstrahlung X-rays

Isotopes production Most isotopes for medicine are produced now with cyclotrons, proton linacs and with reactors. List of radioactive isotopes used in medicine for treatment and for producing images includes more than 100 nuclei with life time from several years, e.g. 60 Co, to several seconds, e.g. 191m Ir. Photonuclear reactions offer another way for isotope production. Electron accelerator is several times cheaper than cyclotron

PET isotopes short living isotopes for positron emission tomography 11 C (20.4 min), 13 N (10.0 min), 15 O (2.0 min), 18 F (109.8 min) can be produced via (γ,n) reaction on target nuclei 12 C, 14 N, 16 O, 19 F Cross section of (γ,n) reaction is 10-100 lower than cross section of reactions with heavy charged particles obtained with cyclotron. However for photonuclear reactions much more thick target can be used, so total isotope yield can be sufficiently high.

Estimations for PET isotopes yields with cyclotron and RTM Isotope Accelerator Reaction Target Saturation Yields 11 C 70/35 MeV RTM 12 C(γ,n) 11 C Graphite -- Diamond 2.6/3.9 Ci -- 4.8/7.1 Ci 11 MeV Cyclotron 14 N(p,α) 11 C N 2 / 0.5-1% O 2 3.0 Ci 13 N 70/35 MeV RTM 14 N(γ,n) 13 N Melamine (C 3 H 3 N 3 ) 1.2/1.6 Ci 11 MeV Cyclotron 16 O(p,α) 13 N 5mM Water&Ethanol 100 mci 15 O 70/35 MeV RTM 16 O(γ,n) 15 O Water 3.2/2.5 Ci 11 MeV Cyclotron 15 N(p,n) 15 O N 2 / 2.5% O 2 760 mci 18 F 70/35 MeV RTM 19 F(γ,n) 18 F Perfluorocarbon or SF 6 gas 2.2/3.0 Ci 11 MeV Cyclotron 18 O(p,n) 18 F H 2 18 O or 18 O 2 1-3 Ci Radiochemistry can not be applied for (γ,n) reaction products isotope with the same as target chemical properties is produced. How to extract? For example, use of thin powder and pick-up recoil nuclei with gas stream.

99m Tc (the daughter nucleus of 99 Mo) is most used isotope in medical imagine. It is now obtained with nuclear reactor. Can be obtained in 100 Mo(γ,n) 99 Mo reaction. Method was experimentally verified. Production of very pure 123 I was demonstrated with electron accelerators at several centers. Reaction 124 Xe (γ,n) 123 Xe 123 I was used. Electron accelerator for medical isotopes production: Beam energy from ~ 25 MeV to ~40 MeV Beam average current from ~100 µa to ~200 µa Conversion to bremsstrahlung X-rays

Explosive detection with photonuclear reactions Original idea of L. Alvarez Tested by Trower W.P., NIM B79 (1993) 589 The most effective method of concealed explosive search till now is odorant method - dogs. However explosive can be detected by detecting its main constituents - nitrogen and oxygen. Anomaly concentration of nitrogen and oxygen in certain proportion means high probability of explosive presence.

β decaying radionuclei photoproduced on stable isotopes with abundance >1 % resulting in three or fewer nucleons. Only photonuclear reactions on carbon, nitrogen and oxygen for beam energy below 70 MeV can produce residual nuclei with half life between 10 and 100 ms.

Explosive detection with photonuclear reactions Lebedev Institute Max 70 MeV electron accelerator Detector Scanned electron beam Moving object

Explosive detection steps 1. Irradiate during 5-10 µs specific portion of object by X-ray radiation generated by electron beam at large (~object dimensions) bremsstrahlung target. 2. Get decay curve within ~ 10-20 ms by mean of registration of secondary X-rays, produced by positrons, emitted by residual nuclei. 3. Go to the next part of object Irradiation of the same object part with different electron energy can be used to distinguish between C, N and O. For the same goal different secondary X-rays registration threshold energy can be used.

Decay curves measured for different substances Melamine Room air

Example of explosive detection No explosive Semtex, 125 g

Electron accelerator for explosive detection technique: Beam energy from ~25 to ~70 MeV Pulsed current ~20-50 ma Pulse duration ~5-10 µs Pulse repetition rate 10-50 Hz Conversion to bremsstrahlung X-rays

SINP MSU experience in design, construction and application of electron accelerators for activation analysis, isotopes production and explosive detection

SINP MSU 70 MeV PULSED RACE TRACK MICROTRON WITH RARE-EARTH PERMANENT MAGNETS Injection energy 48 kev Energy gain 4.8 MeV / orbit Orbits 14 Output energy 14.8-68.3 MeV Output current at 68.3 MeV 10 ma Orbit circumference increase 1λ/orbit Operating frequency 2,856 MHz Klystron power pulsed 6 MW End magnet field induction 0.963 T RTM dimensions 2.2x1.8x0.9 m 3 Innovations: -large ~1 T rare-earth permanent end magnets - rectangular accelerating structure with RF quadrupole focusing - electron beam phase shifter - rare-earth permanent magnet compact quadrupole triplets - self excitation RF system A 70 Mev racetrack microtron, V.I. Shvedunov, A.N. Ermakov, I.V. Gribov, E.A. Knapp, G.A. Novikov, N.I. Pakhomov, I.V. Shvedunov, V.S. Skachkov, N.P. Sobenin, W.P. Trower and V.R. Yajlijan, Nucl. Instrum. Meth. A550 (2005)39-53

Photoactivation technique Gamma rays spectrum from Ge detector after irradiation of 197 Au with bremsstrahlung from 70 MeV RTM

55 MeV PULSED RACE TRACK MICROTRON AT SINP MSU WITH EXPLOSIVE DETECTION SYSTEM COLLABORATION WITH LEBEDEV PHYSICAL INSTITUTE Synchrotron radiation from orbits

Radiation therapy Use of ionizing radiation to kill tumor cells by destroying DNA via complicated physical, chemical and biological processes. Together with tumor cells normal cells on the way of radiation are also killed. Special tactic of irradiation: irradiation from several sides, using special collimators, intraoperative radiation therapy etc.

Cell survival curves Typical cell survival curves for high LET (densely ionizing) radiation and low LET (sparsely ionizing) radiation. LET linear energy transfer

Comparison of electrons and X-rays dose-depth dependencies PPD percentage depth dose

External X-ray radiation therapy Irradiation by bremsstrahlung radiation produced by 1-25 MeV electron beam at special target.

External electron radiation therapy Irradiation by 25-50 MeV electron beam scattered by foil via special applicator. Scanditronix medical RTM MM-50

Stereotactic radiation surgery (SRS) Providing of high dose of X-rays radiation to well localized volume using several radiation sources or single easy movable source. SRS uses dedicated miniature electron accelerator with energy 4-6 MeV, fixed at robotic arm. CyberKnife - based on 6 MeV X-band linac

Intraoperative radiation therapy (IORT) Providing of high dose to well localized volume using several radiation sources or single easy movable source. Similar to IORT modern SRS uses dedicated miniature electron accelerator with energy 4-6 MeV, fixed at robotic arm. Betatron Mobetron Novac7 Liac Russia USA Italy Italy

UPC-SINP MSU-CIEMAT collaboration for IORT dedicated 12 MeV race-track microtron

Conclusion Electron beams in the energy range 0.5 100 MeV have wide and growing spectrum of applications. There are three distinctly different kind of commercial activity in this field : -accelerator design and construction; -technology development; -facility construction and technology application. Many labs conduct R&D in accelerator physics and only a few private companies manufacture commercial electron accelerators. New accelerator busyness can be successful only with new ideas in accelerator design and application.