..::: .. ARIBE ..::: .. H-EBIT ..::: .. ZERNIKE-LEIF ..::: .. ELISA ..::: .. QU-LEIF ..::: ..

 

1. Description of the infrastructure, Relevance and S&T Excellence

H-EBIT: Heidelberg Electron Beam Ion Trap (in charge: J. R. Crespo López-Urrutia)

 

1.1 General description of the Infrastructure

The Heidelberg Electron Beam Ion Trap (EBIT) Facility is the newest one of the three high energy EBITs in the world. It is dedicated to the study of highly charged ions, greatly expanding the range of ionisation stages and ion velocities available on site. Designed to produce up to bare uranium ions (U 92+) and keep them trapped at velocities as low as 10 -4 ´ c
(c: speed of light), it thus allows precision spectroscopic measurements at negligibly small Doppler broadening. The laboratory (Fig. 1) occupies roughly 400 m 2 in the MPI-K Accelerator Building. It is comprised of a large Faraday room where the EBIT is installed on a high voltage terminal, a control room, a laser room, and an experimental hall with beam lines for research with extracted ions. Two more preparation laboratories, a data acquisition and computing room, a clean room, as well as a high‑energy beam line in a radiation protection cave are also part of the facility. The Max-Planck-Institut für Kernphysik (MPI-K, see www.mpi-hd.mpg.de ) is located on the slope of the Königstuhl, in Heidelberg, and can be accessed by car or public transportation in a few minutes from downtown. The infrastructure is operated and owned by the MPI-K, Saupfercheckweg 1, D-69117 Heidelberg, Germany.

The design specifications (350 keV, 750 mA) make this one of the (worldwide) three EBITs able to work with ions in the most extreme charge states. The device (Fig. 2) has been in operation since the end of the year 2001 and has produced electron beams of 100 keV, and maximum electron beam currents of 535 mA. Presently, high voltage conditioning has proceeded only up to 125 kV, since due to several experiments at low beam energies its operation at high energy has not been a central priority. Several key features of the EBIT help to increase the electron beam current and so reduce measurement times. A magnetic field of up to 9 T is used for electron beam compression. Two thermal shields at 50K and 18K insulate the 4K magnet surfaces and also provide efficient cryogenic pumping. The liquid helium consumption is about 20 times lower than that of the standard EBITs. Nine independent drift tubes allow for variability in the trap length and ion extraction schemes. Two large radial bores (40 mm diameter) in the magnet allow good access for diagnostic purposes with the optical, UV, VUV and x‑ray spectrometers already in operation. The ion yields (Hg 78+, Ba 56+, Kr 36+) have allowed to carry out a variety of spectroscopy experiments at high precision (even sub-ppm) levels. The temperature stabilized Faraday room is very advantageous for these purposes. Ions can be extracted from the trap in pulsed and continuous modes at energies of typically 10 keV/q. Ions such as Ne 10+, Ar 18+, Kr 32+ or U 64+ have already been used for experiments. They can be further accelerated by floating the entire EBIT platform to potentials up to 300 kV. The beamline vacuum in the 10 ‑10 mbar range minimizes ion losses. A reaction microscope for COLTRIMS is used for charge exchange measurements, which have been carried out also by external groups. More beamlines will become available soon for external users from fields such as surface physics, molecular fragmentation, precision mass spectroscopy with Penning traps, etc. The ion beam is switched by a magnet to any of the beam lines in the experimental hall. Part of the beam lines are available for external users from fields such as surface physics, molecular fragmentation, precision mass spectroscopy with Penning traps, and others. A laser ion source is used for the injection of heavy elements into the EBIT. Gaseous elements are injected through a differentially pumped atomic beam system. For the diagnostics of the ions beam produced in the trap and extracted into the beam lines, different instruments are installed, comprising X-ray and visible spectrometers, position sensitive detectors, beam monitors, and all necessary ancillary equipment.

The Heidelberg EBIT operates around 260 days per year. During long runs, the facility runs 24 hours per day 7 days a week. A scientist is in charge of the daily operation of the trap and assists the user groups in case of practical problems.

 

2. Management of the access provided

2.1 The Heidelberg Max-Planck-Institut für Kernphysik (MPI-K) is an internationally renowned research centre with around 400 employees, and a long standing tradition on international collaborations. The MPI-K develops research activities in places as geographically diverse as the Arctic regions, the subtropical islands in the Atlantic, the Appenin mountain range and the plains of Namibia, not to mention the space research instrumentation flown in several spacecraft, like the Cassini mission. It maintains scientific collaborations with groups from many different countries. The administration of the MPI-K has the expertise needed to support such a wide range of scientific contacts and activities and will therefore assume the relatively small additional work load and paperwork caused by the external users of the EBIT Facility without any difficulties.

2.2 The users gain access to one of the world’s top research institutions in atomic physics. State-of-the-art facilities, data acquisition systems and an environment where several scientific groups work on fields from atomic, molecular, ion physics to neutrino, high-energy particle and atmospheric chemistry research, providing ideal conditions for scientific discussion. The scientific, technical and logistic support that would be offered to users under the proposal is indeed excellent, because not only the scientific community at this research centre, but also the technical support of the high-precision mechanical workshops on site – which produce instrumentation for space-flight, high energy research and develop and build many other high-technology apparatuses – but also the similarly highly qualified construction and electronic shops, where several dozen engineers and technicians assemble one of the most flexible technical teams around the world. The quality of this scientific environment in which the users will be working will indeed stimulate their research and help users from countries without such facilities overcome their current limitations. Such support is already normally provided to external users, but their numbers are limited by the internal costs caused. The system of user fees is designed to resolve these financial limitations and expand the number of external users without limiting our ability to continue the development of the facility and our own research work.

 

Typically, one or two weeks of beam time are allocated, and this repeated when needed. During the allocated time at a given installation and beam line, the user is naturally in charge of the experiment performed, completely independent of any other activity going on. Local staff will assist the user, and new users will be trained and instructed. Furthermore, any upcoming problems will have a high priority, with the assistance of the technical staff and laboratories on site. The data obtained in a given experiment are usually brought back by the users to their home institution for further analysis. Often some analysis takes place during the actual running of the experiment, and help is provided in this analysis and interpretation of the data, both during and after the experiment. Computing facilities are of course provided. In connection to the infrastructure, there is a user room/office with access to computers, kitchen facilities, etc. A Guest house on the MPI-K site can be used for accommodation when needed.