LOW ENERGY ELECTRON ACCELERATORS APPLICATION

LOW ENERGY ELECTRON ACCELERATORS APPLICATION

V. Shvedunov

Skobeltsyn Institute of Nuclear Physics Lomonosov Moscow State University

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 = ₀exp − µ For electrons

Different mechanisms of radiation interaction with matter are used for different applications - at level of molecules, atoms, nuclei

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

Examples of electron accelerators in the range 0.5 – 5 MeV

Nissin HV 5 MeV,150 kW

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

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%.

RF waveguide Traveling

Wave (TW)

Standing Wave (SW)

CUT VIEW OF STANDING WAVE ACCELERATING STRUCTURES

Side coupled

Examples of electron linacs in the range 5 – 10 MeV

Mitsubishi Heavy Industries TW linac 10 MeV, 25 kW

SureBeam

SW linac 5 MeV,100 kW TitanBeta SW linac 10 MeV, 25 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)

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.

Examples of electron accelerators in the range 10 – 25 MeV

Varian 25 MeV Clinac

20 MeV circular microtron, Indore, India MEVEX, Canada, 35 MeV linac

Electron accelerators in the range 25 – 100 MeV in most cases are built as multisections RF linear

Examples of electron accelerators in the range 25 - 100 MeV

Scanditronix medical RTM MM-50 Danfysik 53 MeV RTM

Research Instruments 100 MeV linac

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

P

t

m

=

η

∆

∆

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

• 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

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

SINP MSU experience in design,

construction and application of

electron accelerators for radiation

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 film dimensions decrease after different

doses. Optimal dose 120 kGy.

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

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 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 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

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

Example of possible application – gemstones colorization

1. Test of spacecraft elements (solar batteries etc) for radiation effects 2. R&D for radiation technologies

SINP MSU 10 MeV TECHNOLOGICAL LINAC Proposal

Pulsed Linear Accelerator PLA-10-15H

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 mm1)

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.

Cargo inspection.

40 mln. sea

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.

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 (c m 2 /g ) Nitrogen Iron Uranium Bremsstrahlung spectrum Co60

Dual energy bremsstrahlung X-rays do permit

to evaluate atomic number and can produce

color picture

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

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 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 kg1)

Beam spots diameters are well below 2 mm

0 100 200 300 400 500 600 0 1 2 3 4 5 6 7 8 E (MeV) I av ( nA )

Energy spectrum in interlaced energies mode

Low High

Scale: 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}

Radiography

http://niiefa.spb.ru/

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

Nuclear reaction based

applications

Elemental analysis

Isotopes production

Explosive detection

Photonuclear reaction thresholds

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

12_{C +} γ _--> 11_{C + n 40Ca +} γ _{--> 39Ca + n}

208_{Pb +} γ _--> 207_{Pb + n}

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.

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

Photo activation technique

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 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. 191mIr.

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.

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% O2 3.0 Ci

13_{N 70/35 MeV RTM} 14_N(γ_,n)13_{N Melamine (C}

3H3N3) 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% O2 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}

218O 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.

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 123I 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

Scanned electron beam

Moving object Detector

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

Example of explosive detection

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

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 m3

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

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.

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

Cell survival curves

Comparison of electrons and X-rays dose-depth dependencies

External

X-ray

radiation therapy

Irradiation 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

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 Liac Russia 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.

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.