* Corresponding author. Tel.: #39-40-3756224; fax: #39- 40-3756258. E-mail address: bonvicini@trieste.infn.it (V. Bonvicini) Nuclear Instruments and Methods in Physics Research A 439 (2000) 471}475 Spectroscopic measurements with a silicon drift detector having a continuous implanted drift cathode-voltage divider V. Bonvicini *, P. Burger, L. D'Acunto, D. Franck, A. Gregorio, P. Pihet, A. Rashevsky , A. Vacchi, L. Vinogradov , N. Zampa INFN-Sezione di Trieste, Via A. Valerio 2, 34127 Trieste, Italy Canberra Semiconductors N.V., Olen, Belgium IPSN, Fontaney-aux-roses, France Cyclotron Laboratory, St. Petersburg University, Russia Abstract A silicon drift detector (SDD) prototype where the drift electrode also plays the role of a high-voltage divider has been realised and characterised for spectroscopic applications at near-room temperatures. Among the advantages of this design, is the absence of metal on the sensitive surface which makes this detector interesting for soft X-rays. The detector prototype has a large sensitive area (2130 mm) and the charge is collected by two anodes (butter#y-like detector). The energy resolution of a such a detector has been investigated at near-room temperatures using a commercial, hybrid, low-noise charge-sensitive preampli"er. The results obtained for the X-ray lines from Fe and Am are presented.  2000 Elsevier Science B.V. All rights reserved. Keywords: Silicon drift detectors; X-ray spectroscopy 1. Detector description Recently, drift detector prototypes where a con- tinuous drift electrode also plays the role of a high-voltage divider have been realised and charac- terised at room temperature. It has been shown that the drift uniformity for what concerns the position resolution is quite satisfactory [1,2]. Fol- lowing this approach, a large sensitive area (260 mm) detector for energy measurements was designed and realised on neutron transmutation doped (NTD) silicon with a resistivity of 3000  ) cm (Fig. 1). The detector (fabricated by Can- berra Semiconductors N.V.) is a `butter#ya bi- directional structure with a drift length of 13 mm for each half. The high-voltage divider has the ge- ometry of a &zigzag line' with a pitch of 150 m. The dividers on two faces of the detector are symmetric to each other with respect to the median axis of the collection anode (Fig. 2). This was done in order to better cancel the transversal component of the drift "eld at the bottom of the potential gutter along which electrons drift towards anodes. The drifting charge is collected on two anodes (one for each half of the butter#y), having an area of 0.1910 mm. To ensure an optimal charge collection, a few cath- odes next to the anodes are externally biased. The 0168-9002/00/$ - see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 9 0 0 2 ( 9 9 ) 0 0 9 2 4 - 9 V. DRIFT DETECTORS