Investigations into the basic structure of matter have occupied many physicists, both experimental and theoretical, for. most of the present century. The rapid progress which has taken place in this field has been made possible not only by conceptual innovations, but also by major advances in particle accelerators and allied technologies.
After the structure of the electron cloud forming the outer part of the atom had been elucidated some forty years ago, the charged nucleus became the focus of attention. It gradually became clear that in order to understand the forces holding the nucleus together, the structure and interactions of the neutrons and protons themselves must be further explored. Such exploration is in the forefront of physics today, and has revealed phenomena quite unsuspected when the theory of the nucleus as a whole began to take shape.
In particular, many new elementary particles with short lifetimes have been discovered. Certain regularities in their properties are observed, and in many ways the situation is reminiscent of that existing fifty years ago with regard to the periodic table of the natural elements. These particles decay very rapidly, and can only be produced in nuclear collisions in which the energy available in the centre of a mass system is of the same order as the particle mass; in practice this requires proton beams with energies of several thousand million volts. It seems clear that a careful study of their formation, interactions and decay will be necessary before a satisfactory description of the nature of the nucleon can be obtained.
In microscopy, closer and closer examination of small 'objects' requires shorter and shorter wavelengths, and good illumination. In a somewhat similar way to bring out the finer details of nucleon behaviour has required the provision of intense beams of particles with ever increasing energy.
This trend to more energetic beams has made the provision of increasingly large accelerators necessary. Thus, to relieve universities of the increasing burden of having to build and operate such machines, the Government, in March 1957, set up the National Institute for Research in Nuclear Science to provide facilities for nuclear physics research which would be available for common use by universities and similar institutions.
The Institute was responsible for the setting up and development of the Rutherford Laboratory which was officially opened in 1964. About 200 physicists from universities and research institutions (both UK and overseas) and from the Rutherford Laboratory itself are now working on experimental programmes using the 7 GeV Proton Synchrotron NIMROD, and the accelerators of the CERN Laboratory in Geneva. Experimental equipment includes a large bubble chamber, and an IBM 370/195 computer. Research and development work is carried out on instrumentation important in high energy physics, for example accelerators, particle beam systems, automatic data handling systems, and superconducting magnets. A Neutron Beam Research Unit was set up in 1971 to support scientists using neutron scattering in a wide range of research fields. The total number of staff employed is about 1200.
During 1965, the Science Research Council was formed as part of the re-organisation of the arrangements for Government support of civil scientific research. The aim of the Council is the support of research and post graduate education in science and technology in universities and under these terms of reference, the Rutherford Laboratory became part of the Science Research Council in April 1965. The council is one of five research councils responsible to the Secretary of State for Education and Science.
The Council carries out its own research and also provides facilities for research by university scientists in its six establishments:-
The London Office of the Council is located at State House, High Holborn WC1.
The internal organisation of the Laboratory is on a divisional basis. There are seven divisions plus the Neutron Beam Research Unit and although their functions are shown separately, there is a large amount of liaison and shared work on common projects.
NIMROD is used as a source for fundamental research into the physics of elementary particles. Its main physical feature is a large ring-shaped electromagnet, 160 ft in diameter, which weighs 7,000 tons. A toroidal shaped evacuated chamber made from glass-fibre reinforced epoxy resin is situated between the poles of this magnet. A pulse of protons, given an initial acceleration to 15 MeV in a linear accelerator, is injected into this chamber and the protons are forced by the magnetic field into a circular orbit in which they receive an acceleration from a radio-frequency electric field once in each revolution. After approximately a million revolutions the protons reach their maximum energy; they are then either extracted from the vacuum chamber or allowed to bombard internal targets, the resulting secondary particles being channelled into an adjoining area where they are used for experiments. During the acceleration period, lasting about three-quarters of a second, the magnetic field strength and the frequency of the electric accelerating field have both to be increased steadily to confine the proton orbits to the magnet ring, and in such a manner as to maintain the delicately balanced stability in the motion of the protons. The whole machine is housed in a semi-underground circular building of reinforced concrete 200 ft in diameter with a 6 ft concrete roof on which a 20 ft layer of earth is placed as additional radiation shielding.
A new injector (a 4-section, 70 MeV linear accelerator) is under construction. The higher energy will enable more protons to be injected into the ring before the onset of transverse incoherent space charge instability. The intensity of the extracted proton beam will increase five-fold to 1013 protons per pulse.
An indication of the complexity of the beam lines into the experimental halls is shown on the following plan. In a full year Nimrod operates for over 5000 hours. In 1972 the number of protons accelerated was twice that in 1970, and nine times that in 1965, the first full year of operation.
There are two types of interaction which are of prime concern in high energy physics, the so-called STRONG force which operates between nuclear particles and is responsible for the binding together of protons and neutrons to form atomic nuclei, and the so-called WEAK force which governs the decay processes. Aspects of both of these interactions are being studied with Nimrod at the present time.
Most of the nuclear particles have very short life-times (typically about 10-8 to 10-10 seconds), and can only be created by bombarding atomic nuclei with protons which have been accelerated to very high energies. The secondary particles produced such as the π and κ mesons can be selected, formed into beams and transported to the Experimental Areas by complex systems of bending and quadrupole focusing magnets, known as 'beam lines'. These radiate out from Nimrod as shown and wherever possible are individually shielded with iron and concrete blocks to reduce the hazard from radiation.
Many of the experiments on the present programme use protons in the form of liquid hydrogen targets on to which the beams of pions or kaons are focused. The momentum and direction of the incoming beam particles and the numbers, momenta and directions of the resultant particles must all be measured. Many techniques are used to detect the particles. These fall broadly into three categories, Scintillation Counters, Visual and Sonic Spark Chambers, and Bubble Chambers, although, in practice, they are often combined.
In each experiment the results of many hundreds of thousands of interactions are recorded on paper tape, magnetic tape or film, and later analysed.
Experiments on Nimrod are carried out by collaborations of physicists from more than 20 universities and research establishments with assistance from large numbers of support staff who, although not members of experimental teams, contribute in many ways to the success of the experiments. In addition, Rutherford Laboratory and University physicists participate in the experimental programme at the Centre for European Nuclear Research (CERN), Geneva, Switzerland. Use is made of the 28 GeV Proton Synchrotron, and of the Intersecting Storage Rings. A full part is being played in the design of the experimental facilities for the multi-hundred GeV SPS (the "300 GeV" machine).
Computing facilities at the Laboratory are centred around the large IBM system 370/195 with 2 Megabytes (quarter words) of main memory. This is backed up by a block multiplexer, a fast access fixed head file, an 800 Megabyte disk store and 12 tape drives. Input is by card readers with output by 4 line printers for over-the-counter jobs; several typewriter terminals are also available for direct submission of jobs - currently about one-third of the quarter-million jobs per year are fed in this way. There are also Remote Job Entry stations in 10 University locations, at CERN, at ACL and at RSRS.
On-line devices are linked to the 370/195 via various smaller satellite computers; these include two IBM 1130's and Honeywell DDP 224 and DDP 516 machines. Connection to the central machine is made via fast data channels and a multiplexed interrupt line. Automatic film measuring machines and rough digitisers, both used for the analysis of bubble chamber and spark chamber film are connected to the satellite computers together with a visual display system and other graphic output devices. Increasing use is being made of visual display units for graphics use - ie for computing in which the output is by graphs or diagrams drawn on a CRT screen, the parameters of the calculations being typed in for each case. This technique is used for reconstruction of scattering events from recorded data, and for the interactive design of magnets. Software has been written in the Rutherford Laboratory for synchronising the functions of the central and satellite machines and forming dynamic logical connections between the users program in the central computer and on-line devices attached to the satellites. In this way, users can benefit from both the processing power of the 370/195 and the data gathering and disseminating power of the satellites.
IBM multiprogramming software is used to enable the central machine to handle several concurrent streams of conventional off-line jobs simultaneously with several on-line jobs. The use of a satellite computer allows for the attachment of new devices, or modifications to existing ones, to be carried out on the satellite without disrupting the flow of work on the central computer and without adding to the IBM supervisory software.
Staff in the Computer and Automation Division are responsible for the whole range of activities connected with the central computer, the satellites and all on-line devices. This work ranges from operating any part of the equipment to writing and implementing the software necessary for controlling the on-line devices and special control programs in the central computer.
Applied physics work at the Rutherford Laboratory is concerned with the exploitation of those new branches of science and technology which can be seen to be of future importance in the implementation of high energy physics experiments. The provision of entirely new types of apparatus or improved forms of existing apparatus then makes it possible to perform new sorts of high energy physics experiments or to repeat, with greater accuracy, experiments already completed.
One subject which has been extensively studied in the Applied Physics Division in the last few years is the generation of high magnetic fields by superconducting magnets. (Superconducting materials can carry substantial DC electric currents with no ohmic loss whatsoever). Collaboration between the Rutherford Laboratory and British industrial concerns has made available a range of superconducting wires and cables tailored to the requirements of the high energy physics apparatus presently under design or construction. Using an alloy of niobium and titanium as superconductor, steady magnetic fields of up to 70 kilogauss with current densities in the coil windings up to 20,000 amperes/cm2 can now be produced by magnets of about 20 cm bore. Magnets of 200 cm bore or more can also be designed to give the same field strength but much lower current densities. These magnets have to operate immersed in liquid helium at about 4°K since the phenomenon of superconductivity only appears at temperatures near Absolute Zero (-273°C). There are therefore many associated cryogenic problems to be solved such as designing vacuum insulated containing vessels which can operate near 4°K with acceptably small heat inleak from room temperature surroundings.
Further work is in progress to develop materials suitable for pulsed magnets. A magnet known as AC4 has recently produced a 45 kilogauss field in its 9 cm bore; the rise time to the peak exciting current of 5,200 A was 1 - 2 seconds. Construction techniques suitable for the production, in industry, of large numbers of identical units are being evolved. When this work is completed the way will be clear to build higher energy particle accelerators than is at present economically possible or to convert existing machines to higher energies. Preliminary plans have already been laid to uprate the new "300 GeV" European accelerator (the SPS) now being built at CERN to 1000 GeV by using superconducting magnets.
Development work is also proceeding on polarised proton targets in which the free proton constituents of materials are acted upon by microwaves in a magnetic field so that the spin axes of the protons are aligned with one another. If the target material is cooled to about 0.3°K the polarisation so produced is "frozen in" and the protons do not then relax to the disordered state for some hours. Such polarised targets allow an important type of high energy experiment to be performed. An incident particle beam is scattered off the polarised target and from measurements on the scattered beam, information on the spin dependence of nuclear forces can be deduced.
Attention is being given to a fast cycling bubble chamber to be used as a vertex detector in conjunction with a counter array, thereby combining the best features of the bubble chamber and electronic techniques of particle detection.
The NBRU was set up in 1971 to provide additional support for research by university scientists using UK reactors for neutron scattering studies in the fields of physics, chemistry, biology and materials science. In 1973 the UK (via the SRC) became a full partner in the Institut Laue-Langevin (ILL) at Grenoble, where there is a powerful new high flux beam reactor. The Unit's programme includes supporting the UK use of these facilities.
A wide range of activities is covered, including the development of new instruments and techniques, scientific collaboration with university scientists and provision of technical support for their research, liaison with relevant research establishments especially ILL, and the study of new neutron sources.
The Laboratory research programme is backed up by a comprehensive support service, principally from members of the Engineering and Administration Divisions.
Safety, including radiation protection, is of prime importance in the Laboratory since the operation of NIMROD produces several hazards, as does the use of high voltage equipment and liquefied gases.
Building, electrical and mechanical services form a considerable part of the Laboratory's activities. Apart from the provision and maintenance of normal services such as steam, water, electricity, etc., the sometimes unusual style of buildings and complex nature of equipment and apparatus have resulted in the formation of skilled maintenance and development sections which provide interesting opportunities in this field. The Council Works Unit is located at the Rutherford Laboratory; it provides engineering effort for the construction and maintenance of buildings and services at all SRC establishments.
A comprehensive photographic service is available to users of the Laboratory. In addition, the photographic unit processes the many thousands of feet of film a year taken in bubble chamber and spark chamber experiments on NIMROD.
Administration Division maintains transport, stores, housing, and similar services and also provides accounting and personnel functions. Several of these activities are making use of the Laboratory's Computer system. There is a comprehensive library available to all Laboratory users, and a reprographic unit which prints many of the Laboratory's publications.
The fundamental nature of the research work carried out in the Laboratory calls for a wide variety of skills covering many disciplines in the scientific and engineering fields. Appointments are made into Civil Service type classes and rates of pay are based upon Civil Service or Atomic Energy Authority scales. Conditions of Service are closely allied to those of the Civil Service.
The Scientific Group encompasses those members of staff that formerly belonged to the Scientific Officer, Experimental Officer and Scientific Assistant classes. Some members of the Group initiate, direct and execute parts of the Laboratory's research programme, while others do development work in fields such as electronics or computing, or are responsible for commissioning or operating pieces of experimental equipment. New recruits enter the Group at a level dependent upon qualifications, which may range from honours degrees downwards. The work undertaken and the career prospects depend more on the aptitudes and abilities of the individual than on his qualifications at entry. Short-term appointments as Research Associates for periods of up to three years are also available, mainly for experimental or theoretical high energy physicists.
The Professional and Technology Group similarly includes those members of staff who formerly belonged to the Engineer, Technical and Drawing Office classes. Members of the Group work in close liaison with the scientific staff in development, maintenance and operational programmes associated with NIMROD and its associated experimental apparatus. The work often involves the use of novel techniques in electronics, computing, cryogenics, superconductivity, magnet technology and high vacuum. In addition to this, more orthodox support is required for the operation, maintenance and development of electrical and mechanical systems plus site and building services.
Qualifications required for professional level posts within the Group are a degree or membership of a Professional Institution. However there are other posts which involve a wide field of responsibility ranging from the supervision of skilled industrial staff in workshops and laboratories to individual work requiring a high standard of technical ability in a particular field including Drawing Office work. Qualifications required are either an Ordinary National Certificate or a Final City and Guilds Certificate in an approved subject plus a recognised apprenticeship.
