> home > Institutes in Asia Pacific
 
Accelerating Charged Particles at VECC
Tapas Samanta
File 1 : Vol30_No2_Institutes in Asia Pacific-4.pdf (0 byte)

Accelerating Charged Particles at VECC

TAPAS SAMANTA
VARIABLE ENERGY CYCLOTRON CENTRE, KOLKATA, INDIA

ABSTRACT

Variable Energy Cyclotron Centre, a research organization under the department of Atomic Energy, Government of India, is a premiere accelerator center located in Kolkata (Fig. 1), India. This article describes the evolution this Centre since its inception to the present state of three different cyclotrons all operating successfully with three distinct purposes. The most interesting one is the oldest Variable Energy Cyclotron running successfully since June 16, 1977. It also describes other related facilities for continuing the associated research programme and briefs about various ongoing accelerator programmes.

 



Fig. 1: VECC Campus.

INTRODUCTION

In the late 1960s, Dr. Raja Ramanna, the then Head of the Physics Group of Bhabha Atomic Research Centre, Trombay, felt the need for a large-scale cyclotron, to be built essentially by Indian scientists to setup a Nuclear Physics Facility. He managed to persuade the Atomic Energy Commission of India, headed by Dr. Homi J. Bhabha, to approve the project. While delivering a lecture before an august gathering at the Nehru Memorial Museum, New Delhi on July 29, 1974, Dr. Raja Ramanna recalled [1]:

"As a measure of our self-sufficiency in very sophisticated technology, I would like to mention the completely indigenously fabricated atom-smashing machine called the 60 MeV Variable Energy Cyclotron being set up at Calcutta. This has a curious history. For several years, the nuclear scientists had been asking Dr Bhabha for his encouragement and support in building a big cyclotron to provide the necessary facilities for the large number of nuclear physicists available in the country….

A report was prepared and the same time a conference of all nuclear scientists was called at Bombay in August 1964 to take a decision on the programme. After hearing the case presented by the scientists, Dr. Bhabha completely turned in favour of providing such a facility. As a result of this, a very sophisticated variable energy cyclotron with practically all the components made in India either at Trombay or in the Public Sector like UHEL, Bhopal and Heavy Electricals, Ranchi is reaching a state of completion at the SALT Lake Site at Calcutta. The machine is expected to come into operation sometime early next year. Though this cyclotron was originally planned to be a nuclear physics facility, it has now become clear to all of us that it will be one of the most important tools for the study of radiation damage in solids of special value in a fast reactor programme."

The journey of Variable Energy Cyclotron Project, Saltlake, Kolkata continued and Dr Ramanna's dream turned to a reality. The entire effort was indigenous and the in-house expertize blossomed into this beautiful machine, a most reliable and rugged one. The power crisis during the daytime in Saltlake/Kolkata at that time was so severe that the young dedicated band of engineers leaded by Dr. Ramanna decided to work mostly at night when the power situation improved as the city had gone to sleep. On 16th of June, 1977, the first alpha beam was delivered by the K130 Room Temperature Cyclotron- aka - the Variable Energy Cyclotron. Dr. Ramanna with a sense of humour termed it as the world's "first nocturnal cyclotron". It was in the late seventies that a revolution from the pages of theoretical physics to the frontiers of experimental nuclear physics was introduced quietly. Since then, it has been providing proton, deuteron, alpha particle and heavy ion beams of various energies to various researchers both from India and abroad. On 15th February 1990, it had been recognized as an independent Research & Development Centre under the Department of Atomic Energy, Government of India. In order to extend the scope of research with heavy ion beams at VECC, the superconducting cyclotron project was conceived in the early 90s. The foundation stone was laid on 18th June 1997 and the first internal beam of the superconducting cyclotron was observed on 25th August 2009. In parallel, a medical cyclotron project was also initiated and finally installed, commissioned and got ready for commercial operation in 2018. It is a moment of pride for VECC that all the three cyclotrons are operational now.

PRESENT STATUS

At present, the Centre consists of major facilities such as the K130 Room Temperature Cyclotron, the K500 Superconducting Cyclotron, the Cyclone-30 Medical Cyclotron (at its second campus near Chak-Garia, Kolkata), the Radioactive Ion Beam (RIB) Facility, the High Performance Computing Facility, the Regional Radiation Medicine Centre and a new Campus for the proposed ANURIB project at New Town, Rajarhat. The proposed new facility of an Advanced National facility for Unstable & Rare-Isotope Beams (ANURIB) is being constructed in collaboration with the Canada-based research institute TRIUMF. The ANURIB project is going to conduct experiments using unstable and rare isotope beams. The existing facilities are as follows.

Room Temperature Cyclotron

The Room Temperature Cyclotron has been upgraded in the recent past to provide both light ion and heavy ion beams as and when required. A PIG source as well as an ECR ion source has been integrated to inject both light ion and heavy ion beams to the RTC. The main components of the RTC (Fig. 2) are: the Electromagnet weighing approximately 262 tonne and having an 88 inch (224 cm) pole diameter with an average magnetic field 1.71 tesla (17.1 kilogauss). The volume of the high vacuum enclosure is approximately 23 m3 and the vacuum in the accelerating chamber is ~ 4횞10-6 mbar.

 



Fig. 2: K-130 Room Temperature Cyclotron with beam lines.

The following beams are accelerated and presently available to the users.

 

Table 1.

Ion Species

Charge State

Energy (MeV)

Alpha

2+

86

Proton

1+

22

Deuteron

1+

25

He+

1+

7.77

Nitrogen

5+

140

Oxygen

6+

180

Neon

7+

240

Argon

12+

340

Superconducting Cyclotron

Recently both the two new cyclotron facilities of VECC i.e., the K500 Superconducting Cyclotron (SCC) (Fig. 3) and the Medical Cyclotron (CYCLONE30), became fully operational for their respective applications. The Superconducting Cyclotron at VECC is the most advanced and high tech accelerator ever constructed in the country. There are only six such accelerators in the world. The 100 tonne iron-core superconducting magnet, largest in the country, produces a magnetic field of about 5 tesla, about 100, 000 times the earth's magnetic field over an area of about 1.5 mm2. This 100 tonne machine, a cylindrical structure of 3 meter diameter and 2.2 meter height, can produce a maximum energy of 80 MeV/A for lighter ions and 5-10 MeV/A for heavier ions covering the whole range of the periodic table. The extraction system consists of two active electrostatic deflectors and eight passive magnetic channels. At the extraction radius the high energy beam is pulled out of its circulating trajectory by the electrostatic deflectors and then it is guided by the magnetic channels almost 330 degrees till it comes out of the machine. Then the extracted beam is transported to the experimental hall by a 13 m long beam line. Two ECR ion sources of frequency 14.4 GHz provide low energy beam for the cyclotron. An electrostatic spiral inflector is used to feed the beam into the acceleration plane at the cyclotron central region.

 



Fig. 3: The K500 Superconducting Cyclotron and high energy beam line.

First beam extraction and nuclear physics experiment took place in K500 SCC. N+2 Beam with ~4.5 MeV/A, accelerated at 14 MHz RF frequency in 2nd harmonic mode of operation, has been extracted (Fig. 4) from the K500 SCC and has been transported to the scattering chamber at the experimental cave. Beam current on the Faraday cup of the beam transport line is about 5nA and on the beam dump at the end of scattering chamber it is a few hundreds of pico-amperes at present.

 



Fig. 4 : Profile of internal and extracted beam current vs radii at K500 SCC.

Also, N+4 beam with ~18 MeV/A has been accelerated at 14 MHz RF frequency in 1st harmonic mode of operation. At present beam transport trial is going on to maximize the beam current in the scattering chamber.

Medical Cyclotron - Cyclone 30

The medical cyclotron facility (Fig. 5) with five beam lines (Fig. 6, 8, 9) has been established by the Variable Energy Cyclotron Centre at Chakgaria, Kolkata. This facility has already produced (Fig. 7) various radioisotopes (18F FDG, Ga-67) and subsequently to process radiopharmaceuticals (Tl-201, I-123 and others), which will be used in nuclear imaging for medical diagnostic purposes. The facility will also be used for various research and development purposes related to material science. There are five beam-lines in total - three beam-lines for the production of radioisotopes and two for R&D purpose. The following radioisotopes are expected to be commercially produced by the Cyclone-30 machine.

 

Table 2.

SPECT/PET Radio-Isotope

Applications

201TI

Myocardial perfusion
(evaluates heart's function and blood flow).

123I

Myocardial metabolism,
Neuroendocrine tumor imaging.

67Ga

Soft tissue tumor imaging,
Bronchogenic carcinoma.

111In

Cisternography, Abscess imaging,
Tumor imaging.

18F

Use in oncology,
brain function studies and cardiology.

 



Fig. 5: The medical cyclotron (CYCLONE-30 by M/s IBA, Belgium).



Fig. 6: Carbon Stripper mechanism For Beam Extraction.

 



Fig. 7: Beam spot on Beam viewer before Target.



Fig. 8: Beam line for PET and SPECT isotopes.

 



Fig. 9: 18F FDG production Module.

High Performance Computing Facility

VECC has had an excellent computing facility starting with a NOVA-1210 machine in 1974. The first computer for acquisition of data from nuclear experiments using the cyclotron was a concoction of two machines viz. PDP-15/76 and PDP-11/05. A third generation mainframe system was installed in June, 1979, to assist in the analysis of data produced from the experiments at the cyclotron. It was also for meeting the general off-line computational needs. Subsequently, a NORSK DATA Computer (1985-1995), a Dual Super-32/70 Systems (1990), a Turbo laser 8200-5/440 (1998), a Dual COMPAQ ES-40 servers (2000 to 2013), the Indigenous VISHMA (2005-2013), Itanium Servers (~2007-2017), the Drona (2010) and the Prafulla-I & II (2012) systems were installed and setup as computing facilities.

Two computing facilities are presently fully operational: one is the Kanad - a general purpose 64 core Intel SMP 2 TFlops machine and the other is the Himalaya - a 92 TFlops high performance computing cluster of 92 12 core dual socket nodes.

 



Fig. 10: Himalaya High Performance Computing Facility.

PHYSICS RESEARCH WITH THE CYCLOTRONS

Nuclear Physics Experiments with K-130 Cyclotron:

The experimental nuclear physics activities at VECC aim to probe the properties of the atomic nucleus, under various conditions of excitation energy, temperature and angular momentum and obtain information about the shape and behavior of the rapidly rotating nucleus when it is formed at a very high temperature. The various aspects of the atomic nucleus under these extreme conditions are being investigated at VECC utilizing beams from the K-130 cyclotron.

The low energy nuclear physics experiments at VECC are mainly motivated by the wide range of accelerated light and heavy ion beams available from the K-130 cyclotron, operating at room temperature at VECC. This cyclotron can provide proton and alpha beams in the energy range of 7-15 MeV and 28-60 MeV respectively. The heavy ion beams from this cyclotron can access the energy range of 7-8 MeV/u, including beams of inert species 20Ne and 40Ar, which is unique in the country. With the light and heavy ion beams from the Room Temperature Cyclotron, a large number of experiments, e.g. study of elastic and inelastic scattering, transfer reactions, fragment emission, fission, giant resonances, nuclear structure using gamma ray spectroscopy etc., are being carried out at VECC.

The mechanisms of damping and dissipation inside the resonantly vibrating nuclear medium are interesting research topics and are being directly probed at VECC by detecting the decaying photons. In highly energetic nucleus-nucleus collisions, information about the initial stages, e.g. size and the time evolution of the resultant hot zone in the reaction, can be characterized using the high energy bremsstrahlung photons coming out from the hot system. These aspects are probed at VECC using the Large Area Modular BaF2 Array (LAMBDA [2]), and the BaF2 multiplicity filter array [3], developed in-house. The LAMBDA array along with the Gamma Multiplicity Filter has been used in experiments for the measurement of high energy gamma photons from hot atomic nuclei. The total detector system is displayed in Fig. 11. The first experimental giant dipole resonance (GDR) width systematics, in the temperature region 0.8-1.2 MeV, have been carried out to investigate the evolution of the GDR width in the shell effect and pairing dominated region, as well as the ratio of viscosity to entropy density of finite nuclear matter, for the first time at this low excitation energy [4-6].

 



Fig. 11: LAMBDA Array arranged in three 7횞7 matrices (left) and the multiplicity filter arranged in two 5횞5 arrays (right).

The nuclear shape and shell structure are being studied using gamma ray spectroscopy with high resolution state of the art Clover HPGe detectors and a Low Energy Photon Spectrometer (LEPS). The VECC array for Nuclear Spectroscopy (VENUS) and the Indian National Gamma Array (INGA), consisting of Compton suppressed Clover HPGe detectors, are used to probe the single particle and collective structures of an excited atomic nucleus [7-9]. The lifetime of nuclear excited states in the range of a few nanoseconds to picoseconds are also measured using the VECC array for nuclear fast timing and angular correlation studies (VENTURE [10]). The energy of the photons emitted from a nucleus, moving with high velocity needs to be corrected as it is Doppler shifted in the laboratory frame with respect to the reference frame of the nucleus. For this purpose a highly segmented Clover HPGe detector is used. All the three detector system are shown in Fig. 12.

 

Fig. 12: VENUS setup of Compton suppressed Clover HPGe (left), INGA setup of Compton suppressed Clover HPGe (middle) and VENTURE setup of 1"횞1" CeBr3 (right).

The Charged Particle Detector Array (CPDA [11]), developed at VECC consists of plastic scintillators, silicon strip detectors and CsI(Tl) crystals. It has excellent angular, energy and isotopic resolutions, large solid angle coverage, and high granularity. One of the important studies using part of this array was an investigation of 3慣 decay of the Hoyle state of 12C in complete kinematics using the CPDA and the alpha beam from the K-130 cyclotron [12-13]. A large area position sensitive gas detector has also been developed which has been successfully utilized to study fission dynamics [14]. The detectors are shown in Fig. 13.

 

Fig. 13: The schematic view of CPDA (top left) and the experimental setup using a CsI(Tl) detector in the scattering chamber (top right). Large area position sensitive gas detector (bottom).



Fig. 14: Neutron detectors for time of flight measurement having dimension of 5" x 5".

Angular momentum dependence of nuclear level density has also been studied with alpha beams from the K-130 cyclotron using time of flight of evaporated neutrons, detected with BC501A liquid scintillators (Fig. 14) [15]. Neutron-gamma discriminator techniques have been applied to obtain the evaporated neutron spectra from nuclear reactions producing various compound systems at different angular momenta. From the evaporated neutron spectra several important studies have been carried out, such as temperature and angular momentum on the nuclear level density and collective enhancement in nuclear level density and its fadeout with excitation energy [16].

Nuclear physics with superconducting cyclotron at Kolkata: Scopes and possibilities

The K500 superconducting cyclotron (SCC) at the Variable Energy Cyclotron Centre (VECC), Kolkata, India can deliver a large variety of particle ion beams over a wide range of energies (up to ~ 80 MeV protons, ~10-80 MeV/nucleon medium heavy ions with mass A < 60, and ~ 5-20 MeV/nucleon for the heaviest ions) and has opened up a new frontier in intermediate energy nuclear physics research in India. On the experimental side, a comprehensive programme for developing several large-scale detector systems and other experimental facilities under the superconducting cyclotron utilization project (SUCCUP) is being implemented [17, 18].

Energetic ion beams from SCC may be used as a powerful tool for the production and study of hot nuclear matter. Several interesting details about the hot nuclear matter are yet to be understood, such as the thermalization process on a small timescale (10-21-10-22 s), the mechanism of the nuclear disintegration process (thermal multifragmentation and vis-a-vis liquid-gas phase transition, dynamical multifragmentation, etc.), and the stability limit of the hot nucleus, to mention a few. Similarly, the study of binary dissipative collisions provides information of nuclear relaxation processes (energy, N/Z, shape equilibration) in greater details. Observed features near the Fermi energy, such as the emission of a significant fraction of intermediate mass fragments (IMF; 3 ≤ Z ≤ 20) from the mid-rapidity region, the presence of neutron-rich matter in the neck region, etc., point to the onset of a transition in the reaction mechanism (from statistical to dynamical regime).

Nucleus-nucleus collisions in and around the Fermi energy domain are also used to study the collective dynamics of hot nuclear systems, i.e., the evolution of fusion-fission and nuclear viscosity, as well as giant resonances built on excited states. The study of hard and soft photon emission in n-n bremsstrahlung processes provides important clues about the dynamics of the system at the beginning and at the later thermalization stages of the reaction, respectively. The study of fragment isotopic distributions and isoscaling in heavy-ion collisions provides information on the equation of state of nuclear matter (symmetry energy). The medium heavy-ion beams from SCC can be utilized to produce and study the properties of many exotic nuclei close to the drip lines using projectile fragmentation as well as deep inelastic reactions [17, 18]. The various experimental facilities developed under the SUCCUP program are highlighted below.

The segmented reaction chamber:

This is a horizontal, three-segment cylindrical chamber (Fig. 15) with its axis coinciding with the beam axis, which has been designed for general purpose nuclear reaction studies using a variety of detector systems in various experimental configurations. A large diameter (1 m) spherical thin wall reaction chamber has also been designed and developed (Fig. 16)

 



Fig. 15: The scattering chamber.



Fig. 16: The spherical chamber.

The Charged Particle Detector Array (CPDA):

A Charged particle detector Array (Fig.17) for Kinematic Reconstruction and Analysis () has been developed at VECC [19], and is capable of detecting a wide range of emitted charged particles (1 ⩽ Z ≤ 20) over the ~4𝜋 solid angle.



Fig. 17: Different sections of the charged particle detector array (ChAKRA).

The neutron multiplicity detector and neutron time-of-flight array:

A 4𝜋 neutron multiplicity detector as shown in Fig.18 has been developed at VECC to measure the number of neutrons emitted in nuclear reactions on an event by event basis with high efficiency. A 50-element time-of-flight (TOF) type neutron detector array (Fig. 19) has also been developed at VECC.

 



Fig. 18: The neutron multiplicity detector.



Fig. 19: The neutron TOF array.

Low energy gamma detector arrays:

VECC houses a number of high resolution gamma detector arrays consisting of HPGe, CeBr3, and LEPS detectors (Fig.20). These detectors are useful for understanding the nuclear structure and shape evolution at high spin and excitation energy and the onset of collectivity, as well as for the measurement of the lifetime of nuclear excited states etc. A cryogenic Penning ion trap is under development at VECC.

 

Fig. 20: Various low energy gamma detector arrays at VECC (a) the VENUS array (b) the VENTURE array (c) part of the INGA array.

In summary, the VECC Superconducting cyclotron is going to open up new opportunities for experimental nuclear physics research in the Fermi energy domain.

INTERNATIONAL RESEARCH COLLABORATIONS

VECC is associated with many International research collaborations, e.g., WA98, STAR (RHIC), ALICE (LHC), FAIR, NSCL with International Laboratories like BNL, CERN, GSI, MSU, RIKEN and TRIUMF etc. It hosts the ALICE Tier2-Centre Kolkata as a part of the LHC Computing Grid (LCG) for ALICE.

Acknowledgement: The respective write-ups provided by Dr.(Smt.) Chandana Bhattacharya, Head, Experimental Nuclear Physics Division, Dr. Malay Kanti Dey, Head, Superconducting Cyclotron Beam Development Section and Shri P. S. Chakraborty, Head, Cyclotron Operation Section are thankfully acknowledged. Special thanks and due Acknowledgments go to Dr. Sumit Som, Director, VECC for his continuous encouragement and support and Dr. Jane Alam, Head, Physics Group, for constant encouragement to prepare this article.

References

[1] Ramanna, R. (1974). Development of nuclear energy in India: 1947-73 (INIS-mf--1680). India.
[2] S. Mukhopadhyay, Srijit Bhattacharya, Deepak Pandit et al., Nuclear Inst. and Methods in Physics Research A 582 (2007) 603-610.
[3] Deepak Pandit, S. Mukhopadhyay, Srijit Bhattacharya et al., Nuclear Inst. and Methods in Physics Research A 624 (2010) 148-152.
[4] Debasish Mondal, Deepak Pandit, S. Mukhopadhyay et al., Phys. Rev Lett 118, (2017) 192501.
[5] Signature of clustering in quantum many body system probed by giant dipole resonance Deepak Pandit, Debasish Mondal, Balaram Dey, Srijit Bhattacharya et al., Phys. Rev C 95, (2017) 034301.
[6] Debasish Mondal, Deepak Pandit, S. Mukhopadhyay et al., Physics Letters B 763 (2016) 422-426, and references therein.
[7] Md. A. Asgar, T. Roy, G. Mukherjee et al., Phys. Rev. C 95, 031304 (2017).
[8] T. Roy, G. Mukherjee, Md. A. Asgar et al., Physics Letters B 782 (2018) 768-772.
[9] S. Rajbanshi, Sajad Ali, Abhijit Bisoi et al., Phys. Rev. C 94, 044318 (2016).
[10] S. S. Alam, T. Bhattacharjee, D. Banerjee et al., Nuclear Inst. and Methods in Physics Research A 874 (2017) 103.
[11] Samir Kundu, T.K. Rana, C. Bhattacharya et al., Nuclear Inst. and Methods in Physics Research, A 943 (2019) 162411.
[12] T. K. Rana, S. Bhattacharya, C. Bhattacharya et al., Physics Letters B 793 (2019) 130-133
[13] T. K. Rana, S. Bhattacharya, C. Bhattacharya et al., Phys. Rev. C 88, 021601(R) (2013).
[14] A. Sen, T. K. Ghosh, S. Bhattacharya et al., Phys. Rev. C 96, 064609 (2017).
[15] K. Banerjee, T. K. Ghosh, S. Kundu et al., Nuclear Instruments and Methods in Physics Research A 608 (2009) 440-446.
[16] Pratap Roy, K. Banerjee, C. Bhattacharya et al., Phys. Rev. C 94, 064607 (2016).
[17] Sailajananda Bhattacharya, PRAMANA -journal of Physics 75, (2010) 305-316.
[18] Chandana Bhattacharya, proceedings of the DAE Symposium in Nuclear Physics, 53 (2008) 121.
[19] Samir Kundu, T.K. Rana, C. Bhattacharya et al., Nuclear Inst. and Methods in Physics Research, A 943 (2019) 162411.

 

Tapas Samanta, a Senior Scientific Officer of VECC/DAE, is the Chairman of the Public Awareness Cell of the Variable Energy Cyclotron Centre (VECC) and Head of the Computer Division, VECC. After receiving the degree of B.E. (Electronics & Telecommunication) from the Bengal Engineering College (presently IIEST), Shibpur, he joined the 35th Batch of the Training School of Bhabha Atomic Research Centre, Trombay. Subsequently, he has worked in the Nuclear Fuel Complex, Hyderabad and then joined VECC. He has received M.Tech (Computer & Information Technology) and PhD in Computer Science from the Indian Institute of Technology. He has expertise in automation & control, computer networking, high performance computing and precision hardware electronics.

 
AAPPS Bulletin        ISSN: 0218-2203
Copyright 짤 2018 Association of Asia Pacific Physical Societies. All Rights Reserved.
Hogil Kim Memorial Building #501 POSTECH, 67 Cheongam-ro, Nam-gu, Pohang-si, Gyeongsangbuk-do, 37673, Korea
Tel: +82-54-279-8663Fax: +82-54-279-8679e-mail: aapps@apctp.org