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ACCELERATOR BASED APPLICATIONS AT BARC-TIFR PELLETRON
ACCELERATOR FACILITY
P.V.Bhagwat, P.Surendran, A.K.Gupta, J.P.Nair, S.C.Sharma, A.Shrivastava, N.G. Ninawe,
M.L.Yadav, A. Shanbhag†, R.M.Kale*, S.K.Sarkar*, J.A. Gore, S. G. Kulkarni, N. Mehrotra,
Ramlal, Q.N. Ansari, U.V. Matkar, Ramjilal, , R.N Lokare, M. Ekambaram, Hillary Sparrow,
N.T.Jadhav, S.B.Salvi, M.B.Kurup*, R.K.Choudhury, S.Kailas and V.C.Sahni
Nuclear Physics Division,
†Radiation Safety Systems Division
Bhabha Atomic Research Centre, Mumbai-400 085.
*Tata Institue of Fundamental Research, Mumbai-400 005.
Abstract
The 14 UD Pelletron Accelerator, set up as a
collaborative effort between Bhabha Atomic Research
Centre and Tata Institute of Fundamental Research, has
been operational since it’s inception in 1989. Apart from
basic research, various accelerator based programmes
including accelerator mass spectrometry, production of
track-etch membranes, production of radio isotopes,
irradiation damage studies are being pursued. This
contribution will describe the details of currently ongoing
programmes.
ACCELERATOR MASS SPECTROMETRY
Accelerator mass spectrometry (AMS) is an ultra
sensitive method of counting individual atoms having
sufficiently long half life and available in low abundance.
The medium energy tandem accelerator of this kind is an
ideal machine to carry out AMS studies with heavy
species like 36Cl, 129I etc. Cosmogenic radio isotope 36Cl
is widely being detected using AMS as it has got
applications in ground water research, radioactive waste
management, atmospheric 36Cl transport mechanism
studies of Arctic Alpine ice core etc [1]. As the interfering
isobar in the 36Cl detection is 36S, a split anode ionization
chamber, being the most suited one, was developed
indigenously [2]. The detector was calibrated using very
low yields of 35Cl and 37Cl (keeping source parameters
low) from the natural sample. The source parameters were
optimised and Mass 36 was injected and transported
through the machine up to the detector. Background 36S
(coming from the ion source as an impurity or memory
effect) is identified in the detector. Recently, a beam
chopper required for this measurement has also been
developed.
36Cl was produced by irradiating sodium chloride
(NaCl) with thermal neutrons at Apsara reactor, BARC
by the nuclear reaction 35Cl(n, γ)36 Cl. The irradiated
sample was used to prepare the ion source sample.
The distinct peaks of 36Cl and 36S can be seen in the
signals from anode 2 and Silicon detector (Fig.1). The
yield of 36Cl in the detector and the 35Cl beam intensity in
the Faraday cup located in close to the detector was
measured. The ratio 36Cl / 35Cl in the sample is found to
be ~ 1.5*10-10 .
Figure 1: Spectra from Anode 2 and Silicon Detector.
PRODUCTION OF TRACK-ETCH
MEMBRANES
Microporous membranes with features such as well
defined and uniform pore size and pore density, uniform
thickness, high tensile strength, inertness to toxic
environments are in good demand for growing number of
scientific and technological applications. Track Etch
Membranes (TEMs) made by irradiating polymer films
with heavy ions using accelerators are well known.
Heavy ion accelerators provide greater flexibility to
produce TEMs of a wide range as they can provide heavy
ions of different atomic number (Z), kinetic energy (E)
and particle flux. The damage size created by the heavy
ions is of the order of 50 – 80 Ao. Chemical etching is
essential to enlarge the pore size to micron range. Pore
densities of the order of 106 to 108 pores/cm2 and pore size
of the order of 0.2 to 1.0 micron are required for many
applications. Large scale industrial application needs
membranes of large area and in bulk quantity.
The polymer films of 25 micron thickness were used. A
magnet [3] was used to scan the heavy ions from the
accelerator in horizontal direction and the polymer film
was moved in vertical direction using a roller mechanism.
The scanner magnet gives a peak magnetic field of 1.35
KGuass. To get larger deflection, higher charge states of
THPMA121 APAC 2007, Raja Ramanna Centre for Advanced Technology(RRCAT), Indore, India
812 08 Applications of Accelerators, Technology Transfer and Industrial Relations
U04 - Other applications
the desired ions are produced using post-stripper. The
deflection, at the exit of the scanner is few centimeters
which is then widened using a horn chamber of one metre
length. At the end of the scanner, deflection up to 25 cms
is achieved. The film is wound on a perspex shaft of 19
mm diameter and is continuously unwound on to another
roller which is driven by a D.C motor from outside the
chamber. Coupling is done using a vacuum rotary
feedthrough. The linear speed of the film is kept at 60
cms/min. The beam is defocused in vertical direction to
get almost uniform particle distribution. Fig. 2 shows
scanning electron microscope (SEM) photograph of
membrane.
Figure 2: SEM Patograph of Membrane.
These membranes are being used to immobilize
antibodies against specific analyte at Radiation Medicine
Centre, Mumbai and for purification of gases at
University of Rajasthan, Jaipur. Also, trial experiments
are in progress at Desalination Division, BARC for water
filtration. Besides these, the membranes were already
used as Supported Liquid Membranes (SLM) in
separating various Actinides and metals [4].
IRRADIATION SET UP
Drift space above analyzing magnet is modified to
accommodate a Proton Beam Irradiation Setup at 6 meter
level at this facility. This setup is capable of delivering
proton beam in the energy range of 2 MeV to 26MeV and
current in µA range. The shielding at this level is such
that radiation is within permissible limit when proton
beam with high energy and µA current is accelerated. In
order to study radiation effects on metals at a higher
temperature a hot target assembly is developed which can
go upto 500 0 C.
Radionuclides such as 52Mn, 67Ga, 96Tc, and 236Pu
are produced for radiopharmaceutical applications. This
setup is also being used for production of monoenergetic
neutrons by Proton beam on Lithium Target. Same setup
is being used to irradiate the target by a heavy ion beam
having different charge states (which means essentially
different energies corresponding to the terminal voltage)
at the same time.
Figure 3: Proton Irradiation Set up.
This setup (Fig.3) is being used by various groups of
BARC, TIFR, SINP and various universities to carry out
experiments. The target assembly features can be
modified/designed as per user’s requirement.
LARGE AREA PROTON IRRADIATION
SET UP
Large area Proton beam of diameter one inch and more
is needed for irradiation of many devices e.g. electronic
chips for space applications, which are of size more than
1 cm, need to be tested for their life time in radiation
environment.
A large area proton beam of size 25 mm to 40 mm
diameter in air was made available to ISRO for testing
their on-line electronic devices. Proton beam flux of 106
to 1010 particles/cm2 was achieved. The proton beam from
the accelerator is focussed on to a gold foil of 1mg/cm2
thickness which scatters the proton beam. The scattered
beam passes through a drift tube of length 1 metre at the
end of which the size of the beam will be more than 50
the entrance of the drift tube isolates the high vacuum on
the accelerator side from the rough vacuum in the drift
tube. And, Titanium window of 50 mm diameter at the
exit of the drift tube isolates the atmosphere from rough
vacuum in the tube. This way even if the large titanium
foil breaks accidentally the second titanium window will
protect the accelerator vacuum. The thickness of the
titanium film was 22 microns. The drift tube is
maintained at a vacuum of 10–3 Torr. The size and energy
mm diameter. A Titanium window of 12 mm diameter at
APAC 2007, Raja Ramanna Centre for Advanced Technology(RRCAT), Indore, India THPMA121
08 Applications of Accelerators, Technology Transfer and Industrial Relations
U04 - Other applications
813
of the scattered beam was evaluated using SRIM 2003
program. The size of the beam was observed using a
plastic scintillator (Fig. 4). The focussing of the beam was
altered to get uniform distribution as far as possible. A
current measuring device to monitor current as a function
of distance from the centre of the scattered beam was
made.
Figure 4: Scattered Proton Beam on Plastic Scintillator.
The experiment was conducted with 100 picoamps on
1cm2 area in the centre as one cm2 was the size of the
chips to be irradiated (Fig. 4). More than 80 chips,
mostly opto-couplers, were tested and found to be in
agreement with the manufacturer’s data.
RADIATION BIOLOGY
A thin window (20μ) of Titanium is placed at 300 N
beam line to bring out ion beam in air. This facility has
been used by users from BARC and TIFR.
REFERENCES
[1] L.K.Fifield, Rep. Prog. Phys. 62, 1223 (1999)
[2] A.Shrivastava et al. Xth ISMAS Symposium-2006,
p.158.
[3] J.P.Nair et al, “Pilot Production of Track-Etch
Membranes(TEMs) using Heavy Ion Beam Scanner”,
INPAC 2005, VECC, Kolkata.
[4] A. K. Pandey et al. Journal of Membrane Science,
Volume 190, Issue 1, 31 August 2001, Pages 9-20.
THPMA121 APAC 2007, Raja Ramanna Centre for Advanced Technology(RRCAT), Indore, India
814 08 Applications of Accelerators, Technology Transfer and Industrial Relations
U04 - Other applications