LOW ENERGY ELECTRON ACCELERATORS APPLICATION

V. Shvedunov

Skobeltsyn Institute of Nuclear PhysicsLomonosov Moscow State University

10 November 2011

Electron accelerators in the range 0.5 – 100 MeVSome applications use bremsstrahlung (X-rays) radiation, some – electron beam.

For X-rays

( )xII µ−= exp0

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 VoltageIon Beam applicationsBudker InstituteEfremov Institute

Examples of electron accelerators in the range 0.5 – 5 MeV

Nissin HV5 MeV,150 kW

ELV (Budker Institute) 0.2 – 2.5 MeV, up to 500 kW

DYNAMITRON (IBA)

Examples of electron accelerators in the range 0.5 – 5 MeV

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%.

RF waveguide

TravelingWave (TW)

StandingWave (SW)

CUT VIEW OF STANDING WAVE ACCELERATINGSTRUCTURES

Side coupled

On-axis coupled

Examples of electron linacs in the range 5 – 10 MeV

Mitsubishi Heavy IndustriesTW linac 10 MeV, 25 kW

SureBeamSW linac 5 MeV,100 kW

TitanBeta SW linac 10 MeV, 25 kW

IMPELA SW linac 10 MeV, 50 kW

Example of electron accelerator in the range 5 – 10 MeV- recirculating RF cavity accelerator

Rhodotron, IBA5 -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

Varian 25 MeV Clinac

20 MeV circular microtron, Indore, India

MEVEX, Canada, 35 MeV linacfor isotopes production

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 Instruments100 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:D

Ptm beamη=

∆∆

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 effectsand productivity for 10 kW electron beam power

• 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

1 Gy = 1 J/kg

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

Irradiation facility based on “Dynamitron”(IBA)

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

Thermo shrinkable polyethylene filmdimensions decrease after different

doses. Optimal dose 120 kGy.

1. Test of spacecraft elements (solar batteries etc) for radiation effects2. Source of high dose rate X-rays radiation3. R&D for radiation technologies

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-1-25Under construction.

Beam energy 1 MeVAverage beam current 25 mAAverage beam power 25 kWOperating frequency 2450 MHzKlystron average power 50 kWWall plug efficiency 30%Beam scanning width 80 cmAccelerator dimensions 470 x 784 x 1375 mm1)

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 MeVPulsed beam current 430 mAAverage beam power 15 kWOperating frequency 2856 MHzKlystron pulsed power 6 MWKlystron average power 25 kWWall plug efficiency 20%Beam scanning width 80 cm

-0.01

0

0.01

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0 2 4 6 8 10 12

E (МэВ)

I(45)

/I(0)

0

20

40

60

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-3 -2 -1 0 1 2 3

y (mm)I

Energy spectrum, beam image and beam profile

Example of possible application – gemstones colorization

1. Test of spacecraft elements (solar batteries etc) for radiation effects2. R&D for radiation technologies

SOME CURRENT APPLICATIONS OF 10 MEV LINAC

SINP MSU 10 MeV TECHNOLOGICAL LINACProposal

Pulsed Linear Accelerator PLA-10-15H

Beam energy 10 MeVPulsed beam current 430 mAAverage beam power 15 kWOperating frequency 2856 MHzKlystron pulsed power 6 MWKlystron average power 25 kWWall plug efficiency 20%Beam scanning width 80 cmAccelerator dimensions 470 x 784 x 1375 mm1)1)Without output horn and power supply

Pulsed Linear Accelerator PLA-10-15V

CARGO INSPECTION AND RADIOGRAPHYX-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

0.01

0.10

1.00

10.00

0.1 1.0 10.0

E (MeV)

µ/ρ

(cm

2 /g)

Nitrogen

Iron

UraniumBremsstrahlung

spectrum

Co60

Dual energy bremsstrahlung X-rays do permit to evaluate atomic number and can produce

color picture

0.01

0.10

1.00

10.00

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E (MeV)

µ/ρ

(cm

2 /g)

Nitrogen

Iron

Uranium

Bremsstrahlung spectra

The most widely used are X-ray sources fromVarian 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

X-rays head

Control console

Design by SINP MSU team of 3/6 MeV linac with interlaced energies

for cargo inspection

Beam energy 3.5/6 MeVDose rate at 1 m 0.2 – 2 Gy/minOperating frequency 2856 MHzPulse repetition frequency 50 – 400 HzAccelerator dimensions 1000x600x900 mmAccelerator weignt 900 kg1)1)Including local radiation shielding

Beam spots diametersare well below 2 mm

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E (MeV)

Iav (n

A)

Energy spectrum in interlaced energies mode

Low HighScale:1 square=1 1 mm

ACCELERATOR WITH FAST MAGNETIC ENERGY SWITCHING FOR CARGO INSPECTION (PROPOSAL)

RTM Parameters

(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.

Beam energies 3.5, 6, 9 MeV

Operating frequency 2998 MHz

End magnets field 0.63 T

Injection energy 25 keV

Pulsed RF power <2 MW

Repetition rate, max 1000 Hz

RTM dimensions1) 650x200x150 mm

RTM weight1) <60 kg

Radiographyhttp://niiefa.spb.ru/

Introscopic system resolution (detector size 2x2 mm)

Accelerator energy, MeV 6 8 10 15Density resolution, % 1 1 1 1Spatial resolution, mm 2 2 2 3Penetrability for steel, mm 200 250 290 350

Film Digital

Varian linac for radiography

Nuclear reaction based applications

Elemental analysisIsotopes productionExplosive detection

Photonuclear reaction thresholds

0

5

10

15

20

25

0 20 40 60 80 100

Z

E th

(MeV

) (γ,n)

(γ,p)

Electron beams with energy higher than 10 MeV are necessary to knock out nucleons from nucleus

12C + γ --> 11C + n 40Ca + γ --> 39Ca + n

208Pb + γ --> 207Pb + n

Photoneutron reaction at different nuclei

Photo activation technique

–method of elemental analysis –using photonuclear reactions.

Level structure of gold isotope 196Au.

Level with energy 595.66 keV has half life period 9.6 h.

196Au can be produced in this isomeric state via photoneutron reaction at stable isotope 197Au.

In this way gold content in ore can be defined with high sensitivity - better than 1 g/ton

Nuclei level structure is unique fingerprints permitting to detect specific elements in very low quantities

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

Most isotopes for medicine are producednow with cyclotrons, proton linacs and withreactors. List of radioactive isotopes usedin medicine for treatment and for producingimages includes more than 100 nuclei withlife time from several years, e.g. 60Co, toseveral seconds, e.g. 191mIr.

Photonuclear reactions offer another wayfor isotope production. Electronaccelerator is several times cheaper thancyclotron

Isotopes production

PET isotopes – short living isotopes for positron emission tomography

11C (20.4 min), 13N (10.0 min), 15O (2.0 min), 18F (109.8 min)

can be produced via (γ,n) reaction on target nuclei

12C, 14N, 16O, 19F

Cross section of (γ,n) reaction is 10-100 lower thancross section of reactions with heavy chargedparticles obtained with cyclotron. However forphotonuclear reactions much more thick targetcan be used, so total isotope yield can besufficiently high.

Isotope Accelerator Reaction Target Saturation Yields11C 70/35 MeV RTM 12C(γ,n)11C Graphite -- Diamond 2.6/3.9 Ci -- 4.8/7.1 Ci

11 MeV Cyclotron 14N(p,α)11C N2 / 0.5-1% O2 3.0 Ci13N 70/35 MeV RTM 14N(γ,n)13N Melamine (C3H3N3) 1.2/1.6 Ci

11 MeV Cyclotron 16O(p,α)13N 5mM Water&Ethanol 100 mCi15O 70/35 MeV RTM 16O(γ,n)15O Water 3.2/2.5 Ci

11 MeV Cyclotron 15N(p,n)15O N2 / 2.5% O2 760 mCi18F 70/35 MeV RTM 19F(γ,n)18F Perfluorocarbon or SF6

gas2.2/3.0 Ci

11 MeV Cyclotron 18O(p,n)18F H218O or18O2 1-3 Ci

Estimations for PET isotopes yields with cyclotron and RTM

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.

99mTc (the daughter nucleus of 99Mo) is most usedisotope in medical imagine. It is now obtained withnuclear reactor. Can be obtained in 100Mo(γ,n)99Moreaction. Method was experimentally verified.

Production of very pure 123I was demonstrated withelectron accelerators at several centers. Reaction124Xe (γ,n)123Xe123I was used.

Electron accelerator for medical isotopes production:Beam energy from ~ 25 MeV to ~40 MeVBeam average current from ~100 µA to ~200 µAConversion 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 explosivesearch till now is odorant method - dogs.

However explosive can be detected by detecting its mainconstituents - nitrogen and oxygen. Anomalyconcentration of nitrogen and oxygen in certainproportion means high probability of explosivepresence.

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 reactionsLebedev InstituteMax 70 MeV electron accelerator

Scanned electron beam

Moving object

Detector

1. Irradiate during 5-10 µs specific portion ofobject by X-ray radiation generated by electronbeam at large (~object dimensions)bremsstrahlung target.

2. Get decay curve within ~ 10-20 ms by mean ofregistration of secondary X-rays, produced bypositrons, emitted by residual nuclei.

3. Go to the next part of object

Irradiation of the same object part with differentelectron energy can be used to distinguishbetween C, N and O. For the same goal differentsecondary X-rays registration threshold energycan be used.

Explosive detection steps

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 MICROTRONWITH 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 m3

Innovations:-large ~1 T rare-earth permanent endmagnets

- 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 techniqueGamma rays spectrum from Ge detector after irradiation of 197Auwith 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 bydestroying DNA via complicated physical,chemical and biological processes.

Together with tumor cells normal cells on the wayof radiation are also killed.

Special tactic of irradiation: irradiation fromseveral sides, using special collimators,intraoperative radiation therapy etc.

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

Cell survival curves

LET – linear energy transfer

Comparison of electrons and X-rays dose-depth dependencies

PPD – percentage depth dose

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

Irradiation by 25 - 50 MeV electron beam scattered by foil via special applicator.

External electron radiation therapy

Scanditronix medical RTM MM-50

Stereotactic radiation surgery (SRS)

CyberKnife - based on 6 MeV X-band linac

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.

Betatron Mobetron Novac7 LiacRussia USA Italy Italy

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.

Intraoperative radiation therapy (IORT)

UPC-SINP MSU-CIEMAT collaboration for IORT dedicated 12 MeV

race-track microtron

Conclusion

Electron beams in the energy range 0.5 – 100 MeVhave wide and growing spectrum of applications.

There are three distinctly different kind ofcommercial activity in this field :-accelerator design and construction;-technology development;-facility construction and technology application.

Many labs conduct R&D in accelerator physics andonly a few private companies manufacturecommercial electron accelerators. New acceleratorbusyness can be successful only with new ideas inaccelerator design and application.