1. Description of the infrastructure, relevance and s&t excellence
QULEIF - Queen’s university low energy ion facility
(contact person I D Williams)
1.1 General description of the Infrastructure
Queen’s University of Belfast has been well known for its accelerator and ion source facilities from the founding of the Atomic and Molecular Physics (AMP) Research Group by Brian Gilbody in 1967 up to the present day. A new building, recently erected on the main university site, houses the present accelerator facility as part of a new university development, an International Research Centre for Experimental Physics (IRCEP). It is proposed that the present facility will form an international infrastructure facility from the start of 2006. The research carried out at this infrastructure in collaboration with international groups will form a significant component of the research activities of the IRCEP. The close proximity of other facilities, such as high power short-pulsed lasers (Laser and Plasma Group) and a microscopy suite (Nanotechnology Group), within the IRCEP building is ideal for cross-disciplinary research.
The current AMP accelerator suite consists of two low energy accelerators equipped with permanent magnet 10 GHz ECR sources for use of beams of multiply charged ions as a probe (ECR1, ECR2 - with floating beam line), a low energy accelerator with capability for using an ion beam as a target (LET), a matrix assisted laser desorption and ionisation source of biomolecular ions (MALDI) and a recently developed negative ion accelerator (NIS). An electron beam ion trap (TRISST) using permanent magnets is currently under development. It is expected to be commissioned by late 2005, and would form a part of the proposed infrastructure.
Existing accelerators have been successfully used by national and international collaborators in the past. In the last five years these include experimental groups from University College London, Open University, University of Reading, NUI Maynooth ( Ireland), Dublin City University ( Ireland), University of Giessen ( Germany), HMI Berlin ( Germany), University of Windsor ( Canada) and Pontifica University ( Brazil). Expressions of interest in using the proposed infrastructure during the period 2006-8 have already come from groups at University College London, NUI Maynooth ( Ireland), Dublin City University ( Ireland), University College Dublin ( Ireland), KVI Groningen ( Netherlands), University of Crete ( Greece) and Lund University ( Sweden).
Compact permanent magnet 10GHz ECR ion source of which two are installed at QUB
Interior view of Queen’s University International Research Centre for Experimental Physics (IRCEP) opened July 2004
Below we cite some examples of recent work:
Nanotechnology - Channeling of highly charged ions through capillaries (ECR1)
(Collaboration with HMI Berlin, Germany)
The phenomenon of ion guiding in PET capillaries is currently being investigated in a collaborative programme with HMI using a dedicated ion surface UHV experimental system in which energy and angular distributions of multiply charged ions can be investigated as a function of beam energy and incidence angle with respect to the capillary axis. This will be extended in JRA2 to investigate mesoscopic and microscopic focusing effects in macroscopic and mesoscopic dimensions. [N Stolterfoht et al Phys Rev Lett 88 (2002) 133201]
Astrobiology – Synthesis of organic molecules on ices (ECR2)
(Collaboration with Open University, UK)
One proposed mechanism for the origin of complex molecules is that they are formed on water and carbon dioxide ices due to bombardment with ionic stellar winds. At QUB we have recently started an investigation into the formation of small organic molecules when such ices are bombarded with ions from ECR2. The flexibility of the floating beam line means that the investigation can cover a range of ion beams from low charge at high energy to high charge at low energy, thus moving between regimes of kinetic and potential energy transfer. The synthesis of carbonic acid has been detected using an infra red fourier transform spectrometer. [Formation of carbonic acid on ices from low energy multiply charged ions, Dawes A, Holtom P, Mason NJ, McCullough RW and Williams ID, Icarus (2004) submitted]
Astrophysics – X-ray emissions from interaction of comets with solar wind (ECR2)
(Collaboration with KVI, Netherlands and Autonoma University, Madrid, Spain)
There are many astrophysical situations where positively ionised species interact with atomic and molecular gases. One possible reaction is charge exchange i.e. capture of one or more electrons by the ion from the atom or molecule where the product ions are often left in excited states. At energies less than 25keV u -1 cross sections are much larger than other atomic processes such as excitation and ionisation. These collisions occur in many astrophysical plasmas, often being the dominant process determining the charge state balance, thermal balance and photon emission. We have developed a unique double translational energy spectrometer (DTES) system to identify and determine the relative importance of the various electron capture channels involved. In particular we have the capability of producing state prepared ion beams in metastable or ground states. [Charge exchange and dissociative processes in collisions of slow He 2+ ions with H 2O molecules. B. Seredyuk, R. W. McCullough, H. Tawara, H B Gilbody, D. Bodewits, R. Hoekstra, P. Sobocinski, D. Pesic, R. Hellhammer, B. Sulik *, N. Stolterfoht, O. Abu-Haija and E.Y. Kamber, Phys Rev A (2005) in course of publication]
Strong Fields – Positive ions in intense femtosecond laser pulses (LET)
(Collaboration with University College London, UK)
The interaction of intense laser fields with matter is an area of great current interest and potential application. Internationally much work is carried out with atomic, molecular, cluster and solid targets. We are one of only two laboratories worldwide to use ion beams as targets for such studies. Having carried out the first study of dissociation of the simplest molecular ion H 2 +, we have recently studied non-sequential ionisation processes in the atomic ion Ar +. [Supression of multiple ionisation of atomic ions in intense ultrafast laser pulses, Greenwood JB, Johnston IMG, McKenna P, Williams ID, Goodworth TRJ, Sanderson J, Bryan WA, El-Zein AAA, Newell WR, Langley AJ and Divall EJ, Phys Rev Lett 88 (2002) 233001]
Fundamental Scattering – Low energy electron-ion scattering (LET)
We are one of only very few laboratories worldwide capable of studying low energy electron scattering from ion beam targets. These are the most sensitive tests of the theoretical calculations used to provide the large amount of collisional data necessary for the understanding of plasmas as found in low temperature technological plasmas for the creation and processing of new material, and high temperature plasmas, eg X-ray lasers, stellar plasmas etc. Having carried out the first ever backscattering measurements with ion targets we have recently been studying scattering near inelastic thresholds. [Angular distribution for the elastic scattering of electrons from Ar +(3s 23p 5 2P) above the first inelastic threshold, Brotton S, McKenna P, Gribakin G and Williams ID, Phys Rev A 66 (2002) 062706]
Biophysics – Fragmentation of Biomolecular ions (MALDI)
A novel voltage labelling target technique has been developed in conjunction with a commercial MALDI instrument to study the fragmentation of both positive and negative biomolecular ions. Proteins and enzymes consisting of single, double and triple polypeptide chains in the mass range of 1000 to 10000 mass units have been studied. [Fragmentation of macromolecular ions, Williams ID, Merron B, Davies RJH, Hughes IG and Morozov VA, AIP Conf Proc 475 (1999) 561]
Electron Correlation – Negative ions in femtosecond laser pulses ( NIS)
(Collaboration with Dublin City University, Ireland, Max Planck Institut fur Kernphysik, Heidelberg, Germany)
In recent years there have been many studies of multiple ionization of closed shell rare gas atoms by intense laser fields. Until now no similar work has been done in the study of more diverse targets such as negative ions where low binding energies and strong electron correlations could yield distinctive behaviour. [ Evidence for rescattering in intense femtosecond laser interactions with a negative ion, J. Pedregosa-Guterriez, P.A. Orr, J.B. Greenwood, A. Murphy, J.T. Costello, K. Zrost, T. Ergler, R. Moshammer and J. Ullrich, Phys Rev Lett 93 (2004) 223001]
New developments in QULEIF as proposed in JRAs 1,3 and 4 focus on sources of biological important molecules.This will extend the capability of the facility from the present source of macromolecules via MALDI to sources of gas phase neutreal DNA and to trapped biomolecular ions. Such a capability is sought after in Europe particularly for molecular level studies of biological species (see JRA5).
2. Quality of the Management
2.1 The current proposal is to integrate the accelerator facilities at QUB into an infrastructure available to external users via application to the ITSLEIF Proposal Selection Panel from 1 January 2006. The facilities are now located in close proximity in a common hall of the new IRCEP building. A management structure will be in place by this time, following the well established patterns of the management structures described for infrastructures I1 – I4.
2.2 A typical experiment is expected to involve at least one international user group of 3 to 5 researchers, with a duration of the order of 2 to 3 weeks. In order to assist the users the infrastructure will nominates a scientist with whom the user group can liaise prior to arrival, and who will be available to give guidance and support during both the installation and the running of the experiment. Technical and computational support will be made available throughout the period. The scientific environment will be highly conducive to the production of the highest quality research work. The new IRCEP at QUB has the aim of promoting interdisciplinary research at the forefront of the international effort. The close proximity of leading experimental groups and international visitors in the areas of Laser and Plasma Physics and Condensed Matter Physics, along with leading research facilities in these areas will be highly stimulating.