GABRIELA (Gamma Alpha Beta Recoil Investigations with the ELectromagnetic Analyser) is a multi-detector array placed at the focal plane of the SHELS separator. Originally it consisted of four multichannel plates to detect the secondary electrons emitted due to the passage of separated evaporation residues (ER) through C foils thus providing an identification flag and a time-of-flight measurement.
The ERs were then implanted in a position–sensitive 16–strip silicon detector (60 x 60 mm2) providing an energy and time measurement of these residues and their subsequent decay (α or fission). A tunnel of four silicon strip detectors 50x50 mm2, 500 μm thick with preamplifier gains tuned for the detection of internal conversion electrons and escape alphas was placed on the upstream side of the implantation detector.
Around the focal plane is a ring of six EUROGAM Phase-I Germanium detectors from the French-UK loan-pool, encased in BGO shields for Compton suppression. A seventh unsuppressed Germanium detector, placed in a collinear geometry with respect to the beam line, completes the array.
In 2009 the position sensitive detector was replaced by a Double Sided Strip Detector with 48 front and back strips.
In 2011 a larger, more pixelated DSSD was purchased from MICRON.
In 2012 an opportunity was afforded to upgrade the gamma-detection part of GABRIELA to the array of 4 coaxial detectors in a cross around the implantation detector and a large clover detector placed right behind the implantation detector.
In May - July 2013 the first test experiments were performed. GABRIELA set up ( α, β, γ - detectors array) was installed at the focal plane of the VASSILISSA separator. Beam of 22Ne from U400 cyclotron and Au, 198Pt, 206-208Pb and 238U targets were used in test experiments. For evaporation residues from reactions with Au and 198Pt targets transmission e±ciency about 5 % was obtained.
In November 2013 test experiments with accelerated 50Ti were performed. With 164Dy and 208Pb targets transmission e±ciency for evaporation residues and suppression factors for scattered Ti beam were studied.
The new GABRIELA array was put into operation in Jan/Feb 2016 with the new CLODETTE clover detector and 4 Loan Pool Phase I detectors.The BGO shields were upgraded as well. In May/June 2016 on arrival of the new phase I detectors the final configuration was completed.
The Si detectors have also been upgraded. The implantation detector is now a 100x100 mm2 DSSD detector with 128 vertical and horizontal strips. The tunnel detector is composed of 8 DSSDs with 16 strips on both sides, 2 DSSDs on each face of the tunnel.
CLODETTE clover detector Final configuration
The vacuum chamber was also modified to ensure maximal transparency to photons and minimal distance from the Ge detectors to the DSSD.
The upgraded Si detectors Modified vacuum chamber
- A. Yeremin, et al. First experimental tests of the modernized kinematic separator VASSILISSA. Phys.Part.Nucl.Lett. 12 (2015) no.1, 35-42
- K. Hauschild, et al. K. et al.Spectroscopy of transfermium nuclei using the GABRIELA set up at the focal plane of the VASSILISSA recoil separator. AIP Conference Proceedings 1238, 337 (2010); doi: http://dx.doi.org/10.1063/1.3455962
- A. Yeremin et al., Nucl. Instr. and Meth. B 266, 4137 (2008). 10.1016/j.nimb.2008.05.131
- K. Hauschild, et al. GABRIELA: A New detector array for gamma-ray and conversion electron spectroscopy of transfermium elements. Nucl.Instrum.Meth. A560 (2006) 388-394 nucl-ex/0602010
- A. Yeremin et. al., Phys. At. Nucl., 66, 1042 (2003).