Accelerator Science and Technology: Current Status and Future Prospects in

Bangladesh

Dr. A K M Fazlul HoqueChief Engineer

Head, Accelerator Facilities DivisionAtomic Energy Centre, Dhaka

Bangladesh Atomic Energy Commission

IntroductionOriginal development of Accelerators in 1930s forresearch in nuclear physics and have become a majortool for research in many areas of science andtechnology.

Developed as a unique tools for exploration of subatomic worldand extensively used for• material analysis and modification• environmental monitoring/studies• diagnostic and therapeutic purposes

More than 15,000 accelerators are in use world wide

Table 1: World wide inventory of acceleratorsCategory Number

Ion implanters and surface modifications 7,000

Accelerators in industry 1,500

Accelerators in non-nuclear research 1,000

Radiotherapy 5,000

Medical isotopes production 200

Hadron therapy 20

Synchrotron radiation sources 70

Nuclear and particle physics research 110

• Low Energy accelerators: From few KeV to MeVSuch accelerators include electrostatic accelerators (single ended, tandem, ion implantors), cyclotrons and electron accelerators (LINAC, Microtrons, Betatrons, High power DC and RF accelerators, etc).

• High Energy Accelerators: From MeV to GeVHigh energy accelerators are used mainly for doing R&D works on

high energy physics, synchrontron radiation and nuclear physics.

Types of Accelerator

Types of AcceleratorsAccelerator facilities make use of several types of devices to build up the energy of the particles. Some of the types of apparatus used are:

•Cockroft-Walton accelerators: high DC voltage device which accelerates ions through steps of voltage created by a voltage divider.

•Van de Graaf accelerators: charge is transported by an insulating belt to a conductor which builds in voltage as a result of charge collection.

•Cyclotrons: An oscillating electric field repetitively accelerates charged particles across the gap between semicircular magnetic field regions.

•Synchrocyclotrons: cyclotrons with variable-frequency accelerating voltages to track relativistic effects.

•Betatrons: electron accelerators in a circular geometry with acceleration achieved by magnetic flux increase.

•Synchrotrons: large ring accelerators where the particles move in an evacuated tube at constant radius, accelerated by radio frequency applications with synchronous magnetic field increases to maintain the constant radius.

•Linear Accelerators: linear arrays of radio frequency acceleration cells.

High Energy AcceleratorsEuropean Synchrotron at Grenoble

Layout of Synchrotron sources

High Energy Accelerators3 km long Stanford Linear Accelerator

High Energy Accelerators in our neighborhood

KEK, Japan

• 50 GeV Synchrotron, 3 GeV Synchrotron, 400 MeV Linac

Institute of high energy physics (IHEP), • China Beijing Electron-Positron Collider: 2.2 GeV

• HIRFL: 900 MeV; HESYRL: 800 MeV Synchrotron

CAT, India• Indus-I: 450 MeV Synchrotron, Indus-II: 2 GeV Synchrotron

High energy accelerators are used mainly for doing R&D works on high energy physics, synchrotron radiation and nuclear physics.

Asian Committee for Future Accelerators (ACFA)

International Linear Collider (ILC)• 500 GeV e+ e- linear collider• Upgrading possible upto 1000 GeV• Construction will complete in 2010• Length ~ 30 – 40 km

• Accelerator as Analytical tool• Accelerators in Life Sciences and Medicine• Accelerators in Material Science• Accelerators in Environmental protection• Accelerators in Industry

Applications of Accelerators

Industrially developed countries are aware of the potential of accelerator based technologies. Below is some examples:

• Germany has 23 electrostatic accelerators : 9 tandem for hydrogen profile determination, RBS, ion implantation, channeling, microprobe and AMS. And devote more than 50% of their operating time to applied research. 16 cyclotrons, some designed exclusively for isotope production, at least 3 with PET capabilities. 11 synchrotron and linear accelerators mainly used for heavy ion accelerator.

• Japan has more than 500 linear accelerators used for therapeutic applications, many heavy ion accelerators and 13 cyclotrons with PET capabilities.

• China has more than 450 low energy accelerators, 14 tandem accelerators, 195 ion implantation accelerators of which 170 of them are used in the device fabrication industries, and 136 cyclotrons.

• India has several tandem accelerators and synchrotron facilities. A new centre for advanced technology (CAT) has been established at Indore for R&D in this field and lasers.

Use of Low Energy Accelerators

• One 3 MV Van de Graaff accelerator at the Atomic Energy Centre, Dhaka.

• 150 kV accelerator (Neutron Generator) at INST, AERE, Savar.

• One linear accelerator has been installed at Delta Diagnostic Centre and

• An accelerator at CMH, Dhaka for therapeutic purposes.

Present status in Bangladesh

Introduction

Basic principle of Accelerator

- V

+Ve-

Basic principle of electrostaic accelerators

Basic parts of an accelerator

Main components of accelerator facilities are:

• Ion Sources

• Injection magnet

• Accelerator

• Switching/Analyzing Magnet

• Control console

• Focusing equipment: Quadrupole lens, Einzel lens,

• Beam tubes and beam line components: Steerer, slit, Faraday

Cup, beam viewer, beam stopper, etc.

• Experimental Chamber, Detectors, Data acquisition system, etc.

400 kV Ion Implanter

400 kV Ion Implanter

Schematic of 150 kV accelerator:Neutron Generator

Tandem Accelerator:Graphical representation

Basic principle of Van de Graaff Accelerator

Basic principle of Pelletron Accelerator

Cockcroft Walton type Accelerators

Cockcroft Walton type Accelerators:Schenkel circuit

Linear Accelerators

Basic principle of Cyclotron

Tandem Accelerator

RF Ion Source

Alphatross ion source:Negative ions

SNICS:Source of negative ions by cesium sputtering

ECR ion source

Oxygen ion spectrum produced by ECR ion source

Iron ion spectrum produced by ECR ion source

Fulerene (C60) ion spectrum produced by Freeman ion source

Cluster ions of Fulerene

Argon ion spectrum produced by Freeman ion source

Cocktail ion spectrum Cocktail ions of m/q=4-5

Cocktail of 12C, 16O, 20Ne,

• horizontal electrostatic accelerator• BAEC started its R&D program only with this facility• Proton, deuteron and alpha particle beam energy upto 3

MeV• capable of producing neutron and X-ray beams using

suitable targets• beam delivered at two ports at 25° using an analyzing

magnet• terminal voltage stabilization is corona type comprises

beam defining slits in the ports• energy stability of 2 keV at 3 MeV• 4 nano-second pulsing system

3 MV Van de Graaff Accelerator

3 MV Van de Graaff Accelerator

Present Lay-out of the BAEC Accelerator FacilityA

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erat

or

Modernization of Experimental Facilities under IAEA TC project

Installation of a new experimental chamber

The Van de Graaff accelerator has been extensivelyused by using the following Ion beam Analysis (IBA)techniques:

1. PIXE (proton induced X-ray emission) is based on atomicfluorescence and the analysis is performed with characteristic X-rays.

2. PIGE (proton induced gamma-ray emission) is based on nuclearreaction and the analysis is performed with characteristic γ-rays.

3. RBS (Rutherford backscattering spectrometry) is based on nuclearscattering and the analysis is performed with charged particles.

4. NRA (nuclear reaction analysis) is based on nuclear reaction andthe analysis is performed with charged particles.

Utilization of the Accelerator

1. Many important base line works on trace element in humantissues, blood, hair, nail, etc. and in environmental ingredients soil,air, water, etc. were done utilizing the PIXE-PIGE set up of theaccelerator laboratory of AECD .

2. Through these works it has been possible for this laboratory toprovide clinical differential diagnosis of arsenic induced diseasesin Bangladesh .

3. One of the striking examples is the detection of high concentrationof lead in the air of Dhaka city and subsequent ban on 2-strokeengines by the Government of Bangladesh .

4. Current research and development activities using RBS techniqueinclude the study of thin film samples of solar cell materialsCuInSe2, CuGaSe2, superconductor materials CuGa1-xInxSe2,, etc.

5. Development of NRA technique has been undertaken to determinealuminum, boron, carbon, etc in thin film structures, which can notbe measured using other techniques.

Utilization of the Accelerator, Elemental analysis

• The accelerator is being utilized extensively to train and retrainquality manpower.

• In collaboration with the universities research works utilizing theion beam facilities of the 3 MV van de Graaff Accelerator arebeing carried out for academic degrees leading to PhD, M.Phil,and M.Sc in the fields of nuclear physics, environmental scienceand engineering, etc.

• More than 50 people obtained their PhD degrees using the Van deGraaff accelerator facilities. At present 6 students have beenworking for their PhD and M.Phil degrees.

Utilization of the Accelerator, Academic activities

PIXE is based on atomic fluorescence created by energeticprotons and the analysis is performed by measuring thecharacteristic X-rays emitted from the sample.

Well adapted to measure major, minor and trace elements indifferent sample matrices such as, biomedical,environmental, agricultural and industrial samples.

Capability: From Aluminum (Al) up to Uranium (U) in asingle experiment.Concentration range: as low as 1 ppmAccuracy: Within 5 – 15%Precision: With in 5%

Present Ion Beam Analysis capabilities:

PIGE: Proton induced gamma emission is based onnuclear reaction and the analysis is performed bymeasuring the characteristic Gamma-rays emitted fromthe elements present in the sample.Useful for measuring light elements such as F, B, Mg,Na, etc.PIGE is capable for isotopic speciation of the sample.Concentration range: As low as 1 ppmAccuracy: Within 5 – 15%Precision: With in 5%

Present Ion Beam Analysis capabilities:

Analytical capability of AFD

RBS: Rutherford backscattering spectrometry is basedon nuclear scattering of particles upon bombardment onthe sample and the analysis is performed by measuringthe scattered particles.

Efficacient in identifying and localizing thin layers.Capability: to measure thickness, depth profiling andcomposition of thin films.Accuracy: Within 5 – 10%Precision: With in 5%

Present Ion Beam Analysis capabilities:

NRA: Nuclear reaction analysis is basedon detection of reaction products (bothparticle and radiation).

• Nuclear reaction studies• To develop methodologies to measure

some specified elements such as Al, B,etc.

Present Ion Beam Analysis capabilities:

• An Annual Development Project (ADP) project to setup a new 3 MV Tandem accelerator facility has beenprepared by the AFD personnel and approved by theGovt. The planned experimental facilities includePIXE, PIGE, RBS, NRA, and AMS set-ups.

• Van de Graaff accelerator personnel are working toimplement the project.

• The tandem accelerator facility will serve as a nationaland international Centre for ion beam analysis.

Future Plan: setting up a new state-of-the-art Tandem accelerator facility

IntroductionThe 3 MV Tandem accelerator, a horizontal electrostatic accelerator, will becapable of accelerate a range of ions of energy ranging from 6 to 20 MeV forresearch in nuclear physics, especially in the area of analytical nuclearphysics.

And the main components of the new 3 MV Tandem accelerator are:• Two external Ion Sources• One injection magnet• The main Accelerator• One Analyzing Magnet• Beam lines• Experimental Chamber• Detectors, Signal processing electronics, etc• Data acquisition system, software, etc.

Future Provisions:• Provisions for future Isotope production: (COST: unknown)

– Generally this type of accelerators are not used for medical isotope production because of slow output but are used for research purpose.

– Requires high-tech chemistry laboratory for isotope processing thus expensive.

• Provisions for future microprobe: (COST: 8-10 Crore Approx.)– Requires high-tech equipments, which were not included in the DPP. Generally the

equipments are produced by other companies than the accelerator manufacturers and quite expensive.

• Provisions for future AMS system:(COST: 12-13 Crore Approx.)– We kept necessary space and accessories for future insertion of AMS equipment in

both low energy and high energy side of the accelerator.– Requires high-tech equipments, which are very expensive and thus were not possible

to buy within the DPP price. Generally the equipments are produced by the same companies which manufacturers the accelerator.

– Also requires high-tech chemistry laboratory for sample processing, which is expensive.

Proposed Lay out of Tandem Accelerator for BAEC, Savar

Injection Magnet

90 Bending Magnet

3 MV Tandem Accelerator

IBA (PIXE/PIGE) Chamber

+15 0+30 -30-15

Negative Ion source

Alpha

Ion source

Analyzing Magnet

IBA Beam line Heavy Ion Beam line

Microprobe Beam line

AMS Beam line

Optional Beam line

ESA/ Bouncer Magnet

ESA

Proposed New Tandem Accelerator Lay-out

90 AMS Bending Magnet

3 MV Tandem Accelerator

IBA (PIXE/PIGE) Chamber

+15

0

+30

-30

-15

Negative Ion source

Positive Ion source Optional

Analyzing Magnet

IBA Beam line

Heavy ion/Isotope production Beam Room

Microprobe Beam line

AMS Beam line

Optional Beam line

Magnet

+ 45

- 45

12 meter

30 meter

The New Tandem accelerator will be used in thefollowing applications:

• Medium energy nuclear experiments• State-of-the-art IBA (PIXE, PIGE, RBS, ERDA, etc.)

experiments• Heavy Ion experiments• Accelerator mass spectrometry• Highly focused Nuclear Microprobe experiments

Utilization of the Tandem Accelerator

The New Tandem accelerator will be used in thefollowing applications:

• Medium energy nuclear experiments• State-of-the-art IBA (PIXE, PIGE, RBS, ERDA, etc.)

experiments• Heavy Ion experiments• Accelerator mass spectrometry• Highly focused Nuclear Microprobe experiments

Utilization of the Tandem Accelerator

The New Tandem accelerator will be used in the following applications:

Bio medical applications:• Trace elements in blood, serum, teeth, human milk, ,

urine, etc. for diagnostic of unusual diseases.• Trace elements in nail and hair for diagnosis of

arsenic toxicity• Diagnostics of Alzheimer's disease, as Fe, Cu and

Zn is related to the disease. • Essential and toxic elements for nutritional

assessment.• Elemental analysis of biopsy samples.

Utilization of the Tandem Accelerator

The New Tandem accelerator will be used inthe following applications:

Industrial applications:• Quality Control (QC) & Quality Assurance (QA) of

industrial and exportable products.• Determination of trace elements in metals and the

composition of alloys, such as boron (B) in Steel.• Impurities, dislocations in semiconductors.• Characterization of materials, such as solar cell,

superconducting materials, etc.

Utilization of the Tandem Accelerator

The New Tandem accelerator will be used inthe following applications:

Agricultural applications:• Soil analysis and fixation of trace elements such as

Zn, B, N etc.• Essential and toxic element monitoring in fertilizers.• Elemental analysis of fruits, vegetables and crops

and other foodstuff.

Utilization of the Tandem Accelerator

The New Tandem accelerator will be used inthe following applications:

Environment protection :• Study of toxic elements in different environmental

ingredients such as water, air, soil, fish, fruits,vegetables and other foodstuff.

• Monitoring of air quality, including transboundaryair pollution.

• Study of aquatic environment: water, sediment, fish,algae, etc.

Utilization of the Tandem Accelerator

The Accelerator facilities Division (AFD) is working hard to meet the increasing national analytical service demand with improved user satisfaction as well as analytical service demand arises from in-house R&D activities. The new Tandem accelerator project will help promotion of nuclear analytical techniques in addressing many priority areas of national development.

Conclusions

Basics of ion beam analysis

Proton induced X-ray emmission (PIXE)

PIXE: As a charged particle moves through a material, it loses energy primarily by exciting electrons in the atoms that it passes by. Electrons in the inner shells of the atom (predominantly the K and L shells) are given enough energy to cause them to be ejected, resulting in an unstable electron atomic configuration. Electrons from higher shells in the atom then 'drop down' to fill these vacancies, and in so doing, give off excess energy in the form of X-rays. The energies of these X-rays are characteristic of the element and therefore can be used to identify elemental composition. On the other hand, by measuring intensities of characteristic X-ray lines one can determine concentrations of almost all elements in the sample down to approximately 1 ppm (part-per-million).

PIXE technique: PIXE is a powerful and relatively simple analytical technique that can be used to identify and quantify trace elements typically ranging from Al to U. Sample irradiation is usually performed by means of 2-3 MeV protons produced by an accelerator. X-ray detection is usually done by energy dispersive semiconductor detectors such as Si(Li). An example of a PIXE spectrum obtained from an aerosol sample is shown below. This spectrum was accumulated in less than 5 minutes, using 2.6 MeV protons with a 10 nA beam current.

PIXE

PIXE (proton induced X-ray emission) is based on atomic fluorescence created by energetic protons and the analysis is performed by measuring the characteristic X-rays emitted from the sample. ure major, minor and trace elements in different sample matrices such as, biomedical, environmental, agricultural and industrial samples.

PIXE is a multi-elemental analytical technique and is capable of measuring elements from Aluminum (Al) up to Uranium (U) in a single experiment

PIXE setup

PIXE spectrum

Proton induced gamma emission (PIGE)Principles: When a charged particle (typically protons) approaches the nucleus of a target atom, the coulomb force usually repels it. However when the incident particle has enough energy to overcome the repulsive coulomb force a charged particle then penetrates through the electrostatic barrier into the nucleus, resulting in interactions with the nuclear forces. During that process, a number of interactions occur, depending on the energy of the incident particle and the type of target nucleus. Typically, a nuclear reaction will occur, resulting in the emission of high energy gamma rays and other nuclear particles. In PIGE, emitted gamma rays are of particular interest as their energies are characteristic of the element and is therefore used to fingerprint elemental composition while yields are used to quantify elemental concentrations.

Detection of emitted gamma rays is done by large volume Ge detectors. PIGE is typically run in conjunction with PIXE and RBS and is used to quantify concentrations of low Z elements such as: Li, F, Na, Mg and Al. Detection limits vary from element to element but it is typically ppm level.

PIGE

PIGE: Proton induced gamma emission is based on nuclear reaction and the analysis is performed by measuring the characteristic Gamma-rays emitted from the elements present in the sample.

PIGE is particularly useful for measurements of light elements such as F, B, Mg, Na, etc. in different matrices such as, biomedical, environmental, agricultural and industrial samples, which are inaccessible by PIXE. PIGE is capable for isotopic speciation of the sample.

PIGE setup

Data acquisition system

PIGE spectrum

PIGE spectrum

PIGE spectrum

PIGE spectrum

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Rutherford backscattering spectrometry (RBS)

Basic Physical Principles: RBS primarily provides information on the profile of concentration versus depth for heavy elements in a light material, e.g. titanium in alumina. Typically, a beam of 2-3 MeV He+ ions is directed perpendicularly on the sample’s surface. As energetic ion penetrates the material, it loses energy mainly in collisions with electrons and only occasionally with nuclei. When the positively charged He+ ion comes close to the nucleus of an atom, it will be repelled by positively charged nucleus. The repulsion force is increasing with the mass of the target atom. For very heavy atoms such as lead or gold, the He+ ion can be repelled backwards with nearly the same energy as it had before the collision. By measuring the energy spectrum of the recoiled ions, information on the composition of the elements, and their depth within the sample can be obtained.

Detection: In RBS, only backscattered ions are detected, and backscattering can only occur if the target atom’s mass is heavier than that of the incident ion. Conventional RBS is done with 4He ions.

In addition to a typical RBS applications such as thin film analysis, RBS is often used in conjunction with PIXE and PIGE to determine concentrations of low Z elements such as C, O, N.

RBS spectrum

RBS spectrum

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SnSi Al

Coun

tsChannel

Al Si SnO2

SiO2