The DESIREE facility will be open for external users from within Sweden, from Europe or from anywhere in the world. Research at the DESIREE-facility may for example include:

  • Studies of mutual neutralisation reactions in collisions between positive and negative ions at tunable center-of-mass energies ranging from a few meV and up to the keV region. Experiments with light (atomic) and heavy (molecular/cluster) ions are possible. Complex ions may be internally cooled.
  • Action spectroscopy – photoabsorption spectroscopy with internally cooled, stored, ions.
  • Studies of unimolecular decay, stabilities and lifetimes of multiply charged negative and positive ions. As the rings may be operated at low temperatures it is possible to study stabilities of, and reactions with, negative ions, anions, which are dissociated by blackbody radiation at normal room temperatures.
  • Studies of biomolecular ions, their stabilities and sensitivities to various heating and ionization processes and their bond-forming processes.

Immediate applications of the research may include:

  • Fundamental atomic, molecular, and cluster physics – the option to study ion-ion collision is so far world unique
  • Astrophysics. DESIREE offers unique possibilities to study reactions and photospectroscopy in conditions like those in many regions in space.
  • Radiation damage on the molecular level
  • Atmospheric physics and chemistry. Ion reactions like those in the atmospheres of Earth and other planets or moons (e.g. Titan) may be studied. The temperature of DESIREE may be regulated from 10 K and up to room temperature and above.

The local research environment around DESIREE and at Stockholm University is formed around experimental and theoretical work on for examples atomic, molecular, and cluster physics, chemical physics, astrophysics and –chemistry, accelerator physics, and advanced detector technologies and developments.

The DESIREE storage rings are two electrostatic ion storage rings with one common ion-beams merging section where positive/negative ion interactions can take place and be investigated.

 

DESIREE is an acronym for 'Double ElectroStatic Ion Ring ExpEriment' and this double ion storage ring is the main instrument of the facility. It has been built for studies of interaction processes involving atomic, molecular, and/or cluster ions. The two storage rings have circumferences of 8.6 m and they have a common section where two stored ion beams of opposite charges are merged. This makes it possible to study reactions between positive and negative ions at center-of-mass energies ranging from the keV the meV range. The two beams are stored separately, one in each ring, and at energies of tens of keV in the laboratory frame. As the rings are purely electrostatic, ions of any mass may be stored and when the rings are operated at the lowest temperature of about 10 Kelvins most molecular and cluster ions will have time to relax to low internal energies during long time storage. The residual gas pressure is of the order of 10-14 mbar which is achieved by means of condensation on the cold inner chamber walls and Ti-sublimation pumps. In addition to cold ion-ion collisions it will also be possible to study interactions between internally cold, stored, ions and laser light in parallel or perpendicular beams geometries. Four position sensitive microchannel-plate particle detection systems are currently mounted around the rings and inside the cryogenically cooled vacuum chamber – one of the detectors consist of three 75 mm diameter channel-plates with a phosphor screen anode and is mounted after the merging section to catch and register one or several neutral fragments from each individual reaction event. A second position sensitive system will catch charged fragments after the merging systems and two additional detector systems will be used for neutral reaction products due, for example, to laser interactions with ions in the outer straight sections of the two rings. In order to achieve these experimental conditions very demanding design conditions for the cryogenic and the vacuum systems have been realized. The DESIREE storage rings are described in detail in this publication.

The electrostatic elements and detectors used for the two storage rings of DESIREE: CD- Cylindrical 160o Deflectors. DE- 10o Deflectors. QD- Quadrupole Doublets. MR- Merging Region enclosed in seven drift tube electrodes. SS- Straight Sections for collinear laser interaction. ID- Imaging Detector for neutral products from the merging region. SD- Optically transparent secondary electron emission detector. MD-, MC- Movable position-sensitive detectors. D1-, D2-, D3- Beam-merging deflectors (note that the deflector plates denoted both D3 and DE bend the beam in the symmetric ring by 10o and the beam in the asymmetric ring by an angle determined by the two beam storage energies). CC-, CV- Correction elements. PU- Electrostatic pick-up electrodes. RF- Radiofrequency beam bunching electrodes. The parts of the injection lines included in this picture are situated inside the main DESIREE vacuum enclosure. Four position-sensitive detectors are mounted in DESIREE.  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

This facility consists of a main instrument with a cryogenic double electrostatic ion storage ring with one common ion-beams merging section and a stand alone beam line for single pass experiments. Positive and negative ions of atoms, molecules and clusters may be internally cooled through trapping and storing.

Research at the DESIREE storage rings may include:

  • Studies of mutual neutralisation reactions in collisions between positive and negative ions at tunable center-of-mass energies ranging from a few meV and up to the keV region. Experiments with light (atomic) and heavy (molecular/cluster) ions are possible. Complex ions may be internally cooled.
  • Action spectroscopy – pulsed laser photoabsorption spectroscopy with internally cooled, stored, complex molecular ions.
  • Spectroscopy and metastable state lifetime measurements for atomic cations applying cw optical pumping techniques.
  • Studies of unimolecular decay, stabilities and lifetimes of multiply charged negative and positive ions. As the rings may be operated at low temperatures it is possible to study stabilities of, and reactions with, negative ions, anions, which would be photodetached by blackbody radiation at normal room temperatures.
  • Studies of biomolecular ions, their stabilities and sensitivities to various heating and ionization processes and their bond-forming processes.

Research at the DESIREE facility's Ion Source Laboratory may include:

  • Fragmentation studies of complex molecular ions in collision with noble gas targets.
  • Fragmentation studies of cold complex molecular ions after optical excitation.

It is our ambition to offer beam time to external users when the facility is fully operational. Until this is organized please contact us via one of the links below if you are a professional researcher and want to propose a joint experiment at the DESIREE facility.

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