No abstract available

[en] A prototype of a new beam profile monitor with tracking and TOF capabilities for degraded beams at HISPEC/DESPEC at FAIR has been built at the Institute of Nuclear Physics at the University of Cologne. The device consists of two detectors in series, each with an active area of 80 x 100mm². The working principle is based on secondary electrons being created by the ions passing through a thin sheet of material. Afterwards they are accelerated and deflected out of the projected ion beam path by an electrostatic top-assembly. The final sub-assembled electron-detector consists of a chevron MCP-stack giving a fast timing signal and a position-sensitive dual delay line. The parameters we investigated using a highly modular test-bed are: the spatial resolution, the timing resolution and the tracking capabilities. The absolute position resolution and the ratio between position dependent resolutions on vertical and horizontal axis have been investigated vs. mesh characteristics, accelerating and deflection potentials, the beam position and its trajectory. Further analysis of the position dependency of the spatial resolution due to the spread of secondary electrons are under investigation. Concerning the TOF resolution we achieved ∼210 ps with a highly divergent alpha beam from a coated ²⁴¹Am source. Simulations showed the intrinsic resolution to be better. First results and conclusions are presented.

No abstract available

No abstract available

No abstract available

No abstract available

No abstract available

[en] In the context of the HISPEC/DESPEC part of NUSTAR at FAIR-GSI we are investigating the development of new tracking detectors to reconstruct the kinematics of the ions after they are decelerated to energies of about 5 MeV/u. The main issue encountered with slowing down relativistic beams is the energy straggling and the spread in space and direction of these beams. Thereby, new generations of beam-characterization detectors are requested to allow not only the precise determination of the position of an incoming ion and its energy loss but also the arrival time (for time of flight purposes-TOF) and if possible to reconstruct the ion track (Beam Tracking Detector), as well. Our solution uses the secondary electrons generated by ions passing through a thin sheet of material (80-120 μg/cm²). Two basic units of large sensitive area (∝80 x 100 mm²) are placed downstream of the beam axis and electrostatic mirrors project the secondary electrons on the position sensitive detectors. The transparency of each component is ∝90%, making the overall transparency of one unit ∝70%. We aim to get an angular resolution of about 1.5-2.5.10^-2 steradian with a sub-ns resolution for the TOF. Even though the S/N ratio per current pulse is very promising, we are facing a very high pulse shot noise at the MCP outputs. The source of these additional electrons is under investigation.

No abstract available

[en] Within the scope of the PreSPEC campaign we performed a Coulomb-excitation experiment to determine absolute E2 transition strengths to 2"+ states in the radioactive nucleus "8"8Kr. The aim of our studies was to identify the one quadruple-phonon mixed-symmetry 2_M_S"+ state in order to extend our knowledge on these states to lighter N = 52 isotones and to track their evolution over different proton shells. The investigated ions were provided through projectile fission of a 650 MeV "2"3"8U beam on a primary target consisting of 0.6 g/cm"2 "9Be and subsequent separation and identification of the reaction products via the FRS at GSI. The secondary target consisted of 0.4 g/cm"2 "1"9"7Au. De-exciting γ radiation was detected by the PreSPEC array, consisting of 15 EUROBALL Cluster detectors. The Lund-York-Cologne-CAlorimeter LYCCA was used for particle identification after the secondary target. Absolute transition strengths of the transitions depopulating the 2"+_3 state in "8"8Kr which suggest the mixed symmetric character of this state are presented and discussed within the systematics of the N = 52 isotones.