Tuesday 16 December 2014
Excitement in the ISIS control room as first neutrons are detected
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On the evening of 16th December 1984 a small group of scientists and engineers waited nervously in the control room. Back in 1984 spallation neutron sources were not common things, so there was a certain amount of trepidation! However at 19:16 that evening first neutrons were detected in what was then the only target station at what was then known as the SNS (Spallation Neutron Source) rather than ISIS!
Following detection of the first neutrons, the machine was run for a further three hours with 2 – 5 x 1011 protons fired into the target. An annual report from the time dryly quotes, “The basic design and performance of the system were as predicted”!
By June 1985 the machine was in full operation, albeit with only 6 neutron instruments: the High Resolution Powder Diffractometer (HRPD), the High Energy Transfer spectrometer (HET), LoQ, LAD, IRIS and TXFA. HRPD, LOQ, IRIS and TXFA are still operational today (though having had significant upgrades since the first version of the instruments and with TFXA now called Tosca).
Since those early days ISIS has gone from strength to strength. Statistics from back then are impressive. In June 1985 the proton current was 0.1µA; by Spring 1986 it was up to 25µA. By 1986 another three instruments, SXD, Polaris and eVS were complete and four more were under construction. In 1987 the European-funded muon facility became operational, expanding the portfolio of techniques available to ISIS users.
By 1986 ISIS was already seeing cutting edge science, with HRPD achieving the first ab initio structure determination (of FeAsO4) using neutron diffraction, and HET seeing the first magnetic inelastic scattering on ISIS. That same year the detailed crystal structure of the first ‘high-temperature superconductor’, YBa2Cu3O7-x, was successfully determined at ISIS using neutron diffraction. This work was followed by the structural determination of C60 (“Buckyballs”), and studies of superconductivity in C60 materials.
As ISIS became well established, the development of pioneering instruments opened new avenues of research. ISIS led the way in developing the technique of neutron reflectometry, which has been widely used to study surface active molecules. These are industrially relevant molecules found regularly in daily life; examples include a whole range of home and personal care products (detergents, conditioners, shampoos, cosmetics, skin care) adhesives, coatings, drug delivery systems and pesticides. In 1990 SANDALS was built, enabling the study of aqueous systems and providing the most complete data on the structure of water that we know of today.
In 2009 the second target station opened, increasing the capacity of ISIS. TS-2 was designed to produce colder neutrons, enabling science in emerging areas including soft condensed matter, biomolecular science and advanced materials. Seven instruments made up the first phase and another four are currently under construction.
30 years after first neutrons were detected, ISIS has 27 neutron instruments and 7 muon instruments. Over 10,000 papers have been published on both the machine and the science it has enabled. We have received over 24,000 proposals, leading to 13,000 separate experiments. In total over 114,000 instrument days have been requested. And the machine has generated around 7x 1024 neutrons, which equates to about 12g!
ISIS is now looking to the future. Our scientists and engineers are closely involved in the development of the European Spallation Source (ESS), a new facility under construction in Lund, Sweden. A design study is underway to replace the target/moderator system in TS1, which will enable us to double the neutron flux to our TS1 instruments. And towards the end of 2015 ISIS will start the process of gathering ideas for ISIS-II, a new accelerator which could start construction in 2025 – 2030, as the ESS goes into steady state operation. So while we celebrate the last 30 years we also look forward to the next 30, and what scientific and technological advances that will bring!
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