Dhaka, Bangladesh
A City of Cyclotrons~I

Comments & Analyses-I

A City of Cyclotrons~I

By Bikash Sinha

Meghnad Saha, the iconic astrophysicist, known for discovering the thermal ionisation equation, was the very first person in India to opt for cyclotron, the accelerator for studying the nucleus. The nucleus was discovered by Lord Rutherford in Manchestor, England, in the beginning of the 20th century, He bombarded helium against a gold foil. The very strong repulsion exerted by the “core” of the atom in that gold foil made the incoming helium recoil and almost turn back. Rutherford ,with a touch of humour, described this extraordinary phenomena thus: “If you fire a bullet at a blotting paper and the bullet comes right back to you”. The nucleus was discovered. The core was the nucleus. On 11 January 1950, Nobel Laureate Professor Madame Curie Joliot inaugurated the Institute of Nuclear Physics in Calcutta, established by Meghnad Saha. An astrophysicist of world renown by then, Meghnad Saha oddly enough veered towards Nuclear Physics around that time. Saha’s student, B. D. Nagchaudhuri was already working in the laboratory of Professor E. O. Lawrence, the inventor of the cyclotron at Berkeley, California. With the help of Lawrence, the work on installing the cyclotron started in right earnest. Unfortunately a large part of the components, including vacuum pumps, shipped from the USA were lost in transit, probably sunk in the Atlantic at the height of the Second World War. Nagchowdhuri went back to the U.S. in 1947, after the war was over. By 1948 the equipment started arriving in Calcutta and the installation of the cyclotron started. The accelerator started working soon and it worked for a while. This was the first cyclotron of the city of Calcutta, a child of the horrible trauma of the War. Come the 1960s, Dr. Raja Ramanna, a member of the Saha Institute council and Head of the Physics Group of Bhabha Atomic Research Centre, felt the need for a large-scale cyclotron, built essentially by Indian scientists in India using Indian technology and to be used for experiments by faculty and students of Saha Institute of Nuclear Physics. Acute shortage of foreign exchange forced total self-reliance, and a large technology innovation efforts. The raging Naxalite movement and acute power shortage made life extreamy difficult. Anyhow, Dr. Ramanna managed to persuade the Atomic Energy Commission of India, headed by Dr. Homi J. Bhabha, to approve the cyclotron project with a grant adequate enough for building the cyclotron. It was almost a replica of the Lawrence Barkeley cyclotron. The ground work for such a collaboration was already done by Nagchaudhuri and Saha. The power crisis was so severe that Dr. Ramanna decided that the young dedicated band of engineers should work mostly at night when the power situation improved as the city had gone to sleep. Ramanna with his mercurial sense of humour termed it as the world’s “first nocturnal cyclotron”. Fortunately, the Naxalites did not bother quite simply, because the scientists had no political affiliation or agenda. Funds started pouring in by 1969, as per plan. Those days were certainly adventurous; the young engineers and scientists were very dedicated and commited, sometimes facing unusual ridicule by steady mortals of the society who go to office in the morning and come back early in the afternoon. The hard work paid off. It was truly a heroic endeavour working through the night with great precession. Ninety per cent of the cyclotron had been made in India, long before the slogan of ‘had’ became fashionable. It is worthwhile to recall that in the Sixties there was virtually no readymade technology infrastructure that could meet the demand of a cyclotron. The 200-ton magnet was built by Heavy Engineering Corporation, Ranchi. The resonator tank, which is the driver of the huge power that runs the cyclotron with the beam of protons or helium going around in a circular path, gaining energy as the beam is pushed from one circular path to the next outer path, was built by Garden Reach Shipbuilders and Engineers (GRSE). They usually build watertight ships, but this time they had to build an air tight chamber, technologically a much more difficult job. It is a perfect example of “necessity is the mother of invention”. Within only eight years after the approval of the project on 16 June 1977 ~ at 3.30 in the morning ~ the internal beam of helium was obtained. “The first nocturnal cyclotron of the world” was commissioned against the backdrop of Naxalite violence, acute power shortage and devastating political unrest. The energy range of this cyclotron is the same as in Berkeley although the technological infrastructure prevalent at that time was rather poor and low grade. It was a fantastic achievement. Initially there were some hiccups, which meant long “shutdowns”. Once the cyclotron started running for 24 hours a day, it started running smoothly without a hitch. A large number of experiments were performed with this machine; scientists from all over the country came to Kolkata with much enthusiasm. Dr Ramanna’s dream turned to reality ~ a great accomplishment by the then Project Director, AS Divatic, and his team. The land of Bose, Saha and Raman now had a cyclotron to boast. It was a revolution that quietly changed the rules of the game, from pages of theoretical physics, the “city of joy” arrived at the frontiers of experimental nuclear physics. That was a little over 40 years ago. Even now, the machine is running so smoothly and almost like a fine tuned jet engine that the “night shift” scientist and engineers can go home, if they wish with just one or two operators at work. A new era started large-scale experiments at your door step with a mature group of world class scientists and engineers. But this room temperature cyclotron consumed an enormous amount of electric power and with time the energy regime was already quite exploited for good and interesting experiments. However, some of my young colleagues with incredible ingenuity found rare gaps of high quality experiments and the results are published in world class reputed journals, even today. So, the next cyclotron project was to be of a higher energy range and it had to be superconducting. This would entail wires made of Niobium Titanium compound, immersed in liquid helium (helium gas turning liquid at a temperature of (-269°c), or four degree kelvin above has the absolute zero (-273°c)) has the most extraordinary property that an electric current passing through this wire faces virtually no electrical resistance, thus becoming “superconducting”. Without any electric resistance, the power consumption becomes almost zero; consequently the cost of running the cyclotron gets vastly reduced. The energy range of this cyclotron is roughly three times the already operating room temperature cyclotron. Clearly, the technology of superconducting cyclotron is of a magnitude more complicated than the room temperature cyclotron. In the US, there are three such cyclotrons, two at Michigan State University and one at Texas, Austin. One of the Michigan cyclotrons is of even higher energy. Japan can boast having the most sophisticated superconducting coupled cyclotrons. The father of superconducting cyclotron is Henry Blossar, an American physicist. He had once warned me that superconducting cyclotron “is a real bitch, she will tease you like mad”. (To be concluded)

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