History-accelerating the particle!
IIT Kanpur first got a particle accelerator in 1968. At that time, it was among one of the first big pieces of equipment, after the IBM computer at IITK campus. The first particle accelerator was a 2 MV Van-de-graff accelerator donated by the US through the Kanpur Indo-American Program (KIAP). In 2006, the original accelerator was dismantled and disposed of since it was no longer suitable for newer projects. The currently installed Tandetron Accelerator was purchased in 2006 from High Voltage Engineering Europa, Netherlands and established in 2008. Professor Vishwas Kulkarni was responsible for setting up the accelerator. Professor Aditya Kelkar has been looking after the facility since 2014. Presently, IIT Kanpur is the only IIT to host a particle accelerator, but some other research institutions like BARC, TIFR, Punjab University and BHU do host accelerators.
Functioning - A journey through the accelerator
Ion Generator
An accelerator produces a high-energy ion beam. The accelerator on campus is a Tandem accelerator, which means that it uses the same voltage to accelerate an ion twice. In a tandem accelerator, the main accelerator tube has both its ends grounded, and it is segmented. There are pellets which are separated by insulators. Successive pallets are at higher potentials, with the central pallet at 1.7 MV. As soon as the beam crosses the central pallet, it collides with high-energy gas, which changes its polarity to positive. The central pallet then repels it, accelerating it further. Therefore, using this tandem accelerator, one can obtain beams of energies up to 3.4 MeV. An environment of Sulphur Hexafluoride is maintained to maintain such high voltages because air breaks down at high voltages (di-electric breakdown?). There is a unit to compress SF6 gas that compresses it to 7 bar.
Accelerator Tube
At this point, the beam is no longer focused. An ensemble of magnetic lenses – concave-convex-concave is used to focus the beam. (Why are three lenses used? – there’s always some variation in the energy, and a single lens would focus beams with varying energy at different points – analogous to chromatic operation in optics). The lenses themselves are electrostatic, and their power supplies can supply up to 20 kV. The focal length of this ensemble of lenses is around 2-3 metres.
Lens Setup
The accelerator is very expensive, and to use it efficiently; multiple beamlines are used. A switching magnet is used to direct the beam towards the desired beamline. The magnetic field bends the beam through a certain angle to direct it. This allows an experiment to take place while preparations for others are underway. The laboratory has two dedicated beamlines, one for microbeam experiments and the other for Rutherford backscattering. Every beamline also has parallel plates that allow for fine-tuning the direction of the beam.
3 millimetre thick tubes are used to ensure that X-ray or other radiation does not leak out. An online Geiger counter keeps track of ambient radiation to provide added safety, and the system shuts down as soon as it exceeds the permissible value. There are similar safeguards when water pressure drops or the vacuum partially fails.
The laboratory gets electricity from the institute, but it has its own 100 kV transformer to isolate the grounding. The laboratory also has a 62 kW UPS that is used to shut down the accelerator safely.
Ions beams require a vacuum to move. In the accelerator, turbomolecular pumps are used to create a vacuum. Fun fact, they work on the same principle as a jet engine! The laboratory has multiple turbomolecular pumps. The life of a pump is ten years, so there is a fair chance that one pump fails every year. This constitutes the bulk of maintenance costs.
Microbeam Setup
The annex was built after the building just to house the microbeam setup. Beam coming from the accelerator is a centimeter in diameter, and the lenses in the microbeam tube are used to focus it down to micrometer size. It is used to create small channels in materials and for scanning.
Funding
Funding the atomic particle accelerator is essential for its maintenance and existence altogether. In its embryonic phase, the accelerator got seed money for its first three years from the Department of Science and Technology (DST), Government of India. Now it is funded by IIT Kanpur itself. Due to the financial scenario in the status quo, the instrument lacks a root for steady funding. The institute has granted funds even in situations where the accelerator faced unanticipated failures in the technical domain highlighting its support for the instrument. A certain sum of the maintenance cost is financed from the institute’s research funds. The accelerator was manufactured by a Dutch company called High Voltage Engineering Europa, and many of its components are not manufactured in India. In the past, when one of the components failed, the only option was to ship it back to the Netherlands. It used to be an expensive process. The team administering the accelerator is incorporating indigenous mechanisms for maintenance intending to truncate the dependence on the parent company, and they have been satisfactorily successful in this regard. Professor Kelkar claims that with respect to high-voltage electronics, they are in a position to maintain everything on their own, and hence not a lot of funding is required.
Difficult times-the upsets
In contrast to its predecessor, which played a crucial role in p-wave scattering, the accelerator has been unable to make significant progress due to several setbacks. Its chief investigator, Professor Kulkarni, passed away in 2010, and the machine malfunctioned shortly after that. It was re-established in 2014 and resumed functioning in 2016. Despite this, the accelerator appears to be rather promising, as several studies yielding significant results are now being conducted on it. In addition, there have been no catastrophic mishaps that have harmed humans or machines. Since its inception, security and safety standards have been in place.
Collaborations
The accelerator’s accessibility is not limited to the physics department alone. There has been collaboration with the mechanical department, a faculty member from the chemical engineering department, and BSBE.
In addition, external collaboration with Flexible Electronics to determine the composition of conducting ink has occurred. Current collaborations include one with NIT Patna and one with Saha Institute (Calcutta). The lab welcomes additional cooperation.
Written by: Rahul Jha, Zainab Fatima, Aviral Upadhyay
Edited by: Mohika Agarwal
Photo credits: Praneat Data
Design by: Manasvi Jain
