X-rays and Synchrotron

A national need

Print edition : October 17, 2014

In Indus-2, India has its own operational synchrotron source. It has been a great technology demonstrator but is only a second-generation synchrotron. The experience gained from constructing it will help in the building of a state-of-the-art synchrotron. Here, Indus-1, a low-energy synchrotron radiation source, which was commissioned in 1999. Photo: THE HINDU ARCHIVES

The Elettra synchrotron at Trieste, Italy.The Department of Science and Technology has made contributions to facilities such as these for assured access to conduct experiments.

The European Synchrotron Radiation Facility (ESRF) in Grenoble France, another facility the Department of Science has contributed to.

Inside BM14, the beamline India uses at ESRF.

A beamline in Petra, Hamburg.

Beamline at Photon Factory in Japan.

Much of the global efforts using X-rays are based on synchrotron radiation, and India has to depend on state-of-the-art facilities abroad. Therefore, setting up a new synchrotron must be seen as part of the larger national scientific endeavour.

THE United Nations has declared 2014 the Year of Crystallography. Diffraction of X-rays by crystals was discovered by Max von Laue and his colleagues at the University of Munich, Germany, in 1912, and 2012 marked the centenary of this discovery. The first structure that Lawrence Bragg determined using X-ray diffraction in 1913, marking the birth of X-ray crystallography, was that of sodium chloride. The year 2013 was celebrated as the centenary of this important event. These two centenary years are now followed by the U.N. Year of Crystallography.

The progress registered using X-ray diffraction during the past century has been truly spectacular. Much of what we know about the structure of matter has been revealed using X-ray crystallography. A large number of Nobel Prizes have been awarded for these efforts. The first structure to be determined using X-ray crystallography contained just two independent atoms. The biggest one, that of ribosome determined recently, an effort for which Venkatraman Ramakrishnan, Tom A. Steitz and Ada Yonath were awarded the Nobel Prize, contains a couple of hundred thousand atoms. That is a measure of the progress of X-ray crystallography in the past one hundred years.

India has a long and distinguished tradition in crystallography, starting with the pioneering efforts of K. Banerjee, a student of C.V. Raman, in Calcutta (now Kolkata) in the 1930s. The pioneers in the area in the country included G.N. Ramachandran and S. Ramaseshan, both students of Raman at the Indian Institute of Science (IISc) in Bangalore, and Ajit Ram Verma. Crystallographic research now constitutes an important component of the scientific efforts in India. It encompasses inorganic and organic chemistry, materials science and biology. X-ray spectroscopy also has grown hand in hand with crystallography. X-rays have other widespread industrial and medical applications, too. The most spectacular applications of X-ray crystallography in recent decades have been in the field of structural biology, which is concerned with the structure and structure-function relationships of biological macromolecules like proteins. These applications are often collectively referred to as macromolecular crystallography.

Technological advances have had a great effect on the progress of crystallography. For example, crystallographers were among the first scientists to take to computation. As far as macromolecular crystallography is concerned, it is often said that two “rings” contributed substantially to the progress of the field in recent years. One is the plasmid ring used in genetic engineering, which has enabled crystallographers to produce macromolecular samples in quantities sufficient for crystallisation through cloning. Cloning techniques also allow scientists to elucidate the roles of individual links in the protein chain through mutations of different kinds. These techniques, often collectively referred to as molecular biology techniques, are widely used in India. The second ring is the “synchrotron ring”. India is not in an enviable position in relation to this ring.

Pushing X-ray limits

Conventionally, X-rays are produced by bombarding an appropriate metallic target with fast electrons under high vacuum. However, only about 2 per cent of the energy of the electrons is converted into X-rays. The rest is converted into heat. Therefore, the target has to be continuously cooled. But cooling efficiency is limited. Consequently, the energy of the electrons and hence the flux of the X-rays produced cannot be arbitrarily increased. Rotating anode X-ray generators were developed to improve the intensity of X-rays. As the anode is constantly rotating, no region of it is continuously bombarded by electrons. The energy of the bombarding electrons can then be substantially increased, resulting in a higher-intensity X-ray beam. For logistical reasons, the size of the rotating anode cannot be arbitrarily increased. Therefore, there are limits to the intensities of X-rays produced by rotating anode generators. This is where things stood nearly half a century ago.

High energy physics involves the use of particle accelerators in which charged particles are accelerated to relativistic velocities, often in a circular path. Acceleration of charged particles results in the emission of electromagnetic radiation. It was the realisation that the intensity of this radiation from particle accelerators in the X-ray range could be very high that led to the development of synchrotron X-ray sources. A synchrotron source consists essentially of a circular “storage” ring, typically of a couple of hundred metres diameter, in which electrons are accelerated to relativistic velocities using magnets. High-speed electrons are initially injected into the storage ring using a “booster”. A synchrotron source produces a continuous spectrum of electromagnetic radiation. The peak of the intensity distribution is in the X-ray range when the energy of the electrons is in the gigaelectronvolt (GeV) range. The peak occurs in the soft X-ray/ultraviolet region when the energy is a few hundred mega-electronvolts (MeV). Unless stated otherwise, the word synchrotron often refers to storage rings with energies in the GeV range.

The intensity of X-rays produced by a synchrotron source is often several orders of magnitude higher than that of the radiation produced by the best rotating anode home sources. Conventional X-ray generators produce high intensities only at certain specified wavelengths determined by the electronic structure of the target material. A synchrotron source, on the other hand, produces radiation of a much higher intensity over a range of wavelengths. One can pick and choose any wavelength from this range. This “tunability” confers great advantage on synchrotron radiation. In what are called third-generation synchrotrons, “insertion devices” are also used to enhance the intensity of the radiation produced.

Yet another important beneficial property of synchrotron radiation is its small angular divergence. In a typical synchrotron ring, X-rays are tapped tangentially at dozens of locations around the periphery of the ring. “Beamlines” are set up at each of these locations to bring radiation to experimental stations. Thus, dozens of experiments are simultaneously performed on a synchrotron facility.

A synchrotron source is a truly multipurpose facility. The beneficial properties of synchrotron radiation make it an ideal tool for a variety of applications in widely different fields. Much of the spectacular applications in macromolecular crystallography have been made possible through the use of synchrotron facilities. This is substantially true of other areas of crystallography as well. Materials science is another area in which the facilities are extensively used. Spectroscopic experiments of different kinds are successfully conducted using synchrotron radiation. Synchrotron facilities have added a new dimension to the medical and industrial uses of X-rays.

Globally, synchrotrons began to be operative in the 1970s. There are now close to 50 synchrotron facilities operating in different parts of the world, including in countries like China, Brazil and South Korea. Even Thailand has a small one. Many countries have more than one synchrotron facility. Much of the global efforts using X-rays are now based on synchrotron radiation.

Efforts in India

Discussions on synchrotron facilities in India started in the late 1970s. The most definitive meeting on the subject took place in 1984 at the Bhabha Atomic Research Centre (BARC), Mumbai. At the meeting, P.K. Iyengar represented the Department of Atomic Energy (DAE), S. Varadarajan the Department of Science and Technology (DST), and Rais Ahmed the University Grants Commission (UGC). Many of us potential users also participated in the meeting. It was decided in that meeting that the DAE would undertake to construct simultaneously a low-energy Indus-1, which is of limited use, and a high-energy Indus-2, which is what most of us were concerned with. The hope then was that the facilities would become available within a reasonable time frame. Work on the facilities began at the Centre for Advanced Technology (CAT), Indore, which was subsequently rechristened Raja Ramanna Centre for Advanced Technology (RRCAT), in 1986. The 450 MeV Indus-1 was commissioned in 1999.

The main machine, Indus-2, did not appear to be anywhere near the horizon at that time. In the meantime, efforts that depended on synchrotron facilities gathered momentum in the country. Macromolecular crystallography came of age by the turn of the century. Organised efforts in materials science spread to different parts of the country. There were also other areas that could benefit through the use of synchrotron facilities. In response to the increasing need for synchrotron radiation, the DST made some arrangements for Indian scientists to access facilities abroad such as Elettra in Italy. These arrangements, though welcome, were inadequate to meet the growing requirements in India. They were in no way a substitute to having such facilities in India. Therefore, the user community began to grow restive. That resulted in a meeting of representative synchrotron users in Hyderabad in 2004, convened by Seyed E. Hasnain, the then Director of the Centre for DNA Fingerprinting and Diagnostics (CDFD), and Kota Harinarayana, the then Vice-Chancellor of the University of Hyderabad, with Shekhar Mande, then at CDFD, as the main organiser. This writer was asked to chair the meeting.

The Hyderabad meeting recommended the setting up of a new synchrotron facility in addition to expediting the work at the RRCAT. R. Chidambaram, Principal Scientific Adviser (PSA) to the Government of India, and Vinod Sahni, the then Director of the RRCAT, were kept informed about the deliberations of the Hyderabad meeting. Subsequently, some of us visited the RRCAT and had detailed discussions with Sahni and his colleagues. That was the beginning of extensive interactions between the user community and colleagues at the RRCAT. That also gave an additional fillip to the work on Indus-2.

By now, synchrotron facilities had become a topic of active discussion in the scientific community. The issue figured in the 2006 report of the Steering Committee on Science and Technology for the Eleventh Five-Year Plan. A major recommendation of the committee, which was implemented, was to lease/set up beamlines in synchrotron facilities abroad. In pursuance of this recommendation, a materials science beamline was set up at Photon Factory, Tsukuba, Japan, with funds from the DST. The Department of Biotechnology (DBT) funded part-leasing of the macromolecular beamline BM14 at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. The DST made a contribution to the setting up of Petra at Hamburg, Germany, for assured Indian access to the facility. It also funded the setting up of a macromolecular crystallography/high-pressure beamline with partial Indian ownership at Elettra. These beamlines have certainly raised the synchrotron-based efforts in India to a higher level.

Indus-2

In 2009, P. Balaram, the then Director of the IISc, proposed the setting up of a synchrotron facility at its newly acquired land in Chitradurga. The proposal was discussed at a meeting of the Scientific Advisory Committee to the Cabinet (SAC-C) in August 2009. Soon afterwards, the PSA constituted a Committee of Experts, with S.K. Sikka, formerly of the BARC, and this writer as co-chairmen, with a broad mandate on synchrotron facilities. It considered a proposal submitted by D.D. Sarma, on behalf of the IISc, to set up a 3 GeV synchrotron. Another proposal, for a 6 GeV machine, was submitted by Milan Sanyal, the then Director of the Saha Institute of Nuclear Physics (SINP), Kolkata. The SAC-C commended both the proposals to the Planning Commission.

In the meantime, work on Indus-2 at the RRCAT, now headed by P.D. Gupta, was progressing well with the full support and encouragement of the Committee of Experts referred to above. It is difficult to pinpoint the exact period during which it became operational, as the work went through several stages. In any case, it was ready for reasonably trouble-free data collection by 2012-13. That was an achievement to rejoice in. India had at last its own operational synchrotron source.

Indus-2 can be described as a second-generation synchrotron. Most of the well-known sources around the world are third-generation machines. Therefore, it is not a state-of-the-art facility. However, it has been a great technology demonstrator. The experience gained from constructing it will stand us in good stead. Many scientists have already profitably used Indus-2 for their research. However, that does not obviate the need for a state-of-the-art Indian synchrotron source. The DAE itself recognised this need in 2013. Later that year, the Scientific Advisory Committee to the Prime Minister (SAC-PM) also recommended the setting up of a new facility. Subsequently, in March this year, a meeting at the Planning Commission chaired by K. Kasturirangan endorsed the proposal for a new facility.

The national dimension

Thus, a broad consensus on the need for a state-of-the-art Indian synchrotron facility exists. The question is how to translate this consensus into reality. In my view, a synchrotron facility has a national dimension that transcends the requirement of the users for powerful X-ray beams with appropriate properties. A major problem with the Indian economy is the weakness of the manufacturing sector. This weakness is partly due to the inadequacy of instrumentation capability in the civilian sector. Competence of a high order in instrumentation exists in the strategic sector involving the DAE, the Department of Space (DoS) and the Defence Research and Development Organisation (DRDO). By the very nature of the strategic sector, this competence cannot easily percolate into the public domain.

On the other hand, the non-strategic sector is relatively open. However, most research and educational institutions in the country in the non-strategic sector are bereft of any significant instrumentation capability. One way of building up this capability across the board is for institutions in the strategic and the non-strategic sectors to undertake mega projects jointly. Synchrotron facilities lend themselves to such joint efforts. One is certainly likely to encounter turf problems as well as institutional and individual egos. With sustained efforts these problems can be overcome.

Synchrotron technology and the science based on it are developing continuously. Setting up a synchrotron facility is not a one-off process. Development in the area needs to be pursued continuously. Therefore, the setting up of a new synchrotron facility should be looked upon as one step in a continuous process. A given synchrotron facility is used simultaneously by workers belonging to widely different disciplines and it is an ideal medium for promoting multidisciplinary interactions. Thus, the move to set up a new Indian synchrotron facility should be looked upon not only as an effort to provide beamlines for individual groups of users but also as part of a larger national endeavour.

A consensus has been reached only on the need for a new synchrotron source in the country. Still, there is no clarity as to who will take up the responsibility. The location is yet to be decided. The specifications are yet to be worked out. Then, of course, there is the major issue of funding. As was suggested at the meeting at the Planning Commission referred to earlier, deliberations on these issues should be initiated jointly by the DAE and the DST or, more generally, the Ministry of Science and Technology. Currently, the DAE is the only agency that has hands-on experience in setting up a synchrotron facility. However, the stakeholders are mostly those who do research using grants from the departments under the Ministry of Science and Technology.

The DAE and the DST have a long tradition of working together and they should have no difficulty in spearheading the synchrotron effort together. That would also enable the strategic and the non-strategic sectors. In due course, other strategic and non-strategic agencies should also be brought into the deliberations. Irrespective of which agency/agencies or institution(s) incubate it, eventually the new synchrotron facility should be an autonomous entity. In the context of India’s overall scientific performance and in relation to the global situation, India has lagged behind in its synchrotron efforts. The earlier it move towards a state-of-the-art Indian synchrotron, the better it will be.

M. Vijayan is INSA Albert Einstein Research Professor, Molecular Biophysics Unit, Indian Institute of Science, Bangalore.

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