Future access to neutron sources

Towards a next generation neutron facility in Europe

37. In a 20 year forward look at neutron scattering facilities in OECD (Organisation for Economic Co-operation and Development) countries and Russia, the OECD MegaScience Forum in 1998 predicted that many of the existing national neutron sources will have closed or be reaching the limits of their projected lifespan. The European Neutron Scattering Association equates this to a 30% reduction in European neutron scattering capacity over the same period. The 1998 OECD Ministerial Conference endorsed the recommendation of the MegaScience Forum that an entirely new megawatt spallation neutron source should be constructed in each of the Asian, North American and European regions. The US and Japan have been persuaded by the scientific case underlying the opportunities afforded by a megawatt class spallation source and our own views are consistent with this.
38. At Oak Ridge, Tennessee, USA, the SNS project under construction is a single purpose facility for a full-energy linac (1GeV) plus storage ring with a flowing liquid mercury target for neutron scattering applications, operating at 60Hz pulsing frequency and 1.4MW proton power on target. The layout provides for a second target station optimised for long wavelength neutrons. The design allows for substantial accelerator power upgrades to ~ 4MW total power, with target upgrades. Current plans are that the SNS will have first neutrons in 2006 and 14 instruments by 2012.  The plans for the project anticipate that full power should be reached by the end of 2009.

The recommendation of the MegaScience Forum that an entirely new megawatt spallation neutron source should be constructed in each of the Asian, North American and European regions.

39. JSNS is the neutron facility currently under construction at Tokai-mura in Japan, which is embedded within the multipurpose proton accelerator complex, J-PARC. A 180MeV linac feeds a 3GeV rapid cycling synchrotron, which drives the neutron source at a pulsing frequency of 25Hz with 1MW proton power on target. J-PARC also includes a 50GeV synchrotron fed from the 3GeV ring, used for particle physics and as a neutrino source. The linac has the provision to drive a sub-critical reactor assembly. Current plans are that the JSNS will have first neutrons in 2007 and will have a full range of instruments around 2012.
40. There is currently no commitment within Europe to the construction of a megawatt class next generation neutron facility. In 2001 the design parameters for a European Spallation Source project were concluded by a team drawn from a group of laboratories from across Europe and beyond. The design incorporates a 1.3GeV, 10MW proton accelerator feeding a long pulse target station at 16.67Hz and a short pulse target station, via a proton accumulator ring, operating at 50Hz. The design plans are for both the long and short pulse target stations to operate at a power level of 5MW. The cost of the ESS design is estimated to be £1Bn at 2002 prices.
41. There are, effectively, only two ‘nucleations’ of activity within Europe at present in terms of planning for a Next Generation Neutron Facility (NGNF) within Europe: (i) the Scandinavian European Spallation Source (ESS-S) plans for a long pulse spallation source at Lund in Sweden and (ii) the ESS-I project for a step-wise implementation of the European Spallation Source project – beginning with a LPSS – that is being promoted by a number of potential site hosts in Sweden (Lund), Germany (site reference) and the UK (at Burn in Yorkshire advocated by the regional development agency ‘Yorkshire Forward’ , together with the White Rose University Consortium). It remains to be seen what other potential bids might emerge should planning for the future start within Europe at government levels.

The nature and scope of the planning required

42. The Technology Panel has made a set of recommendations on the need for access by UK researchers to a next generation neutron facility. Such a new facility would extend the scientific capability of the neutron facilities that the community has access to – creating a new high level tier of capability.
43. While there are some current declared interests in Europe in hosting a next generation neutron facility there is as yet no arrangement in place for developing a structured approach to this issue – including within the context of the emerging ‘European Research Area’ considerations of large scale research infrastructures.
44. It is the conclusion of the Council that planning for future neutron scattering facilities needs to be conducted at appropriate European levels. This view is supported by ISAC. There are a complex set of issues to be addressed. These involve scientific and technical issues, policy issues, financial issues and issues concerned with timing, prioritisation and hosting. There is currently no suitable forum in existence within Europe where the full range of these issues can be discussed and through which the essential work plans might be coordinated.
45. The Council considers that the initial step should be for the UK to take the initiative in organising discussion on what the scope of the necessary European planning should be, as a prerequisite for establishing study groups with defined technical and scientific remits. The UK’s scientific and technical expertise in spallation neutron sources makes it credible that it should take such a lead.

It is the conclusion of the Council that planning for the future for neutron scattering facilities needs to be conducted at appropriate European levels.

46. From discussions with ISAC and elsewhere in Europe, the Council concludes that a first step would be to convene a group of nominated representatives from a small number of countries within Europe with significant interest in neutron scattering facilities. The process should be started as soon as possible in 2006. The group should be invited to draw up a ‘prospectus for action’ for wider consideration in Europe – including a timeline for decision making. The aim should be to complete the prospectus within one year and subsequently to reach agreement on a ‘policy and plan for  Europe’ , with a wider set of interested countries, within the following two years.
47. The Council would propose that the UK invite Germany, France, Spain, Sweden and Hungary to form an initial group to begin these discussions.

The preferred technical options

48. Of the various technology options available at this time – and having particular regard to the requirements of the UK science case – the Technology Panel considered: “... an LPSS with a beam power of 5MW and possibly higher, and a 5MW SPSS appear the most promising”.
49. The Technology Panel concluded that, in terms of technology development needs, the UK should also take a lead in establishing appropriate technology study groups. The Panel estimate that such studies would take five years, should be undertaken with European collaboration and would cost the UK £750k (to organise the study groups, excluding technical studies and associated research and development costs).
50. ISAC considered that it was not immediately obvious why the UK or Europe might want to plan from the outset to ‘leap ahead’ of the existing USA SNS and JSNS technical goals. There remain considerable uncertainties associated with being able to achieve the Technology Panel’s goals for both the LPSS and, even more so, for the SPSS. It was the view of ISAC that the build of an SNS-class facility in Europe could also represent an effective response to the competition – and even with this option there are significant technical challenges outstanding (such as the need for substantial target technology development) that remain to be addressed. ISAC concluded, therefore, that a European technology study should examine the ‘best achievable’ power, which could include the possibility of a sub-5MW (SNS-class) source.
51. Having an SPSS on one site (possibly with two target stations) and an LPSS on another (with the possibility to upgrade the power and to add an extra target station) would seem to be a scenario that would enable Europe to maintain the necessary capacity, with significantly increased capability, the broadest range of instrumentation and the better prospects for upgrade. A step-wise approach to building this scenario could assist Europe in more readily defining a starting point for planning the next generation of neutron sources.
52. The cost of a next generation neutron facility – currently estimated at £1Bn – would be difficult for the UK to contemplate funding on its own. The construction costs alone would equate to ten years exclusive commitment of the current Office of Science and Innovation (OSI) Large Facility Capital Fund. The annual operating costs – estimated at up to £100M a year would represent almost three times the present level of spend by the Council on neutron facility operations. This would almost certainly necessitate UK withdrawal from the ILL and the closure of ISIS. The Council does not advocate this approach.
53. The Council concludes that the UK should take a lead in Europe in establishing technical study groups to review the options for more powerful next generation neutron facilities – that take account of the progress achieved at the facilities under construction in the USA and Japan.