The PPAC array PYRAMIDE

The PYRAMIDE is an array composed of 3 parallel plate avalanche counters (PPACs) which are position sensitive in two dimensions. It was developed by a collaboration of the University of Frankfurt am Main and GSI, Darmstadt [1].
The PYRAMIDE detects scattered projectile-like ions in Coulomb excitation and multi-nucleon transfer studies in coincidence with the gamma-rays. It was designed to cover a wide range of scattering angles (74^o to 162^o in the laboratory system) and a large solid angle of 1.8pi. Furthermore, the signal from the PPAC serves as time reference in the trigger, because its time resolution is much better than that of Ge detectors.
The measurement of the scattering angle and, hence, the impact parameter enables the investigation of the dependence of cross sections on the distance between the two colliding nuclei as well as a Doppler correction of the emitted gamma-rays.
The position sensitivity is achieved by analysing the charge division on a resistive layer which is evaporated on a printed circuit board. The charges are collected on every edge of the trapezoidal-shaped board. A more recent development is a multilayer board with delay lines in two dimensions.
The PYRAMIDE was used together with GASP since the beginning of the GASP activity (1992) [2] as well as in pre-EUROBALL experiments at GSI (1996) [3].

[1]

K. Vetter, Th. W. Elze, M. Kaspar, T. Kröll, J. Gerl,
Nucl. Instr. and Meth. A 344, 607-610 (1994)

[2]

J. Gerl, D. Bazzacco, Th. W. Elze, T. Happ, T. Härtlein, W. Korten, T. Kröll, D. Napoli, C. Rossi Alvarez, R. Schubert, K. Vetter, H. J. Wollersheim,
Prog. Part. Nucl. Phys, Vol. 38, 79-85 (1997)

[3]

I. Peter, W. von Oertzen, H. G. Bohlen, A. Gadea, B. Gebauer, J. Gerl, M. Kaspar, I. Kozhoukharov, T. Kröll, M. Rejmund, C. Schlegel, S. Thummerer, H. J. Wollersheim,
Eur. Phys. J. A4, 313-316 (1999)

---