Low-energy Radioactive Ion Beam Spectroscopy Station (LeRIBSS)

Low-energy Radioactive Ion Beam Spectroscopy Station (LeRIBSS)
LeRIBSS is located behind the RIB injector magnet at the bottom of the HRIBF Tandem accelerator, see Fig. 1. It consists of beam transport elements, a universal detector support called CARDS (from LSU), and a new fast-moving tape collector (LSU). The space left behind the CARDS array in the initial configuration will allow us to accommodate the Multi-Turn Time-of-Flight (MTOF) mass spectrometer when ready. CARDS can support several detectors, including Ge counters, a fast timing BaF2 array, high resolution electron detectors, β-counters and a high-efficiency β-delayed neutron detector. LeRIBSS is located where the highest quality and intensity HRIBF RIBs are available. In particular, it profits from the high-resolution injector magnet, which has a mass resolution ΔM/M better than 10-4.

Experiments at LeRIBSS can be performed with negative as well as positively charged ions since transport through the Tandem is not required. It means that the rates of exotic nuclei like, e.g., 79Cu and 85Ga at the level of 10 pps can be expected. LeRIBSS will also accept RIBs from the planned HRIBF upgrades (IRIS2 and proposed electron driver). IRIS-2 beams, an upgrade of the present High Power Target Laboratory, will be merged with the existing RIB delivery system in front of the high resolution injector magnet. Ion energies of about 200 keV should be large enough to provide an implantation timing signal from a Microchannel Plate detector equipped with a 10 μg/cm2 carbon foil and improve the signal/background ratio using the implantation-decay time correlations.

Construction of a Low-energy Radioactive Ion Beam Spectroscopy Station (LeRIBSS) dedicated to decay spectroscopy studies at the HRIBF is a joint effort between ORNL and HRIBF users.

Fig 1 - A schematic sketch of the LeRIBSS beamline suspended from the ceiling to provide clearance for the rotating energy-analyzing magnet of the tandem. The bending magnet to the right normally directs the beam into the tandem accelerator.
The equipment which is planned to be used at LeRIBSS is: The expected γ-ray efficiency of CARDS is shown in fig. 2.

Fig 2 - The efficiency of the CARDS Clover Ge array as measured in a "ranging out" experiment in June 2006. The setup consisted of 4 Clover Ge detectors with two pushed forward as close as possible to the β detectors.

Some photographs

Fig 3 - The LeRIBSS beamline with the empty detector support structure.
Fig 4 - The LeRIBSS detector support structure filled with high-density polyethelene for the neutron detector 3Hen. Ed Zganjar from LSU (shown) constructed the pieces of 3Hen and the detector support structure.
Fig 5 - The LeRIBSS detector support structure filled with high-density polyethelene for the neutron detector 3Hen. One tube has been inserted in to the detector.

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