Planar edgeless silicon detectors for the TOTEM experiment

Abstract

Abstract-Silicon detectors for the Roman Pots of the the large hadron collider TOTEM experiment aim for full sensitivity at the edge where a terminating structure is required for electrical stability. This work provides an innovative approach reducing the conventional width of the terminating structure to less than 100 m, still using standard planar fabrication technology. The objective of this new development is to decouple the electric behavior of the surface from the sensitive volume within a few tens of micrometers. The explanation of the basic principle of this new approach together with the experimental confirmation via electric measurements and beam test are presented in this paper, demonstrating that silicon detectors with this new terminating structure are fully operational and efficient to under 60 m from the die cut.

Advanced model of silicon edgeless detector operation

“…The current terminating structure, consisting of two p+ rings, was located in the area adjacent to the sensitive cut. The proper operation of the CTS was confirmed using measurements of I-V characteristics of full size detectors (with an area of 8 cm 2 ), which showed that the current in the sensitive bulk is actually a bulk generation current that is about four orders of magnitude smaller than the CTR current [5]. Statistics of the bulk current from over 200 detectors (Fig.…”

“…These two assumptions are actually equivalent since both postulate that the hole current at the cut edge is dominant. Combination of (5) and (6) gives a linear rise of the total currentjs and the electric field E s along the cut is: div(jJ= ge-'Ie div(hJ = gh, (4) ge=gh jh = gh(d -x) (5) je = (ge -'IJx (6) where W: is the specific distance for E z dissipation. W z can be estimated as the detector thickness, d, within which the detector edge effects are dissipated.…”

“…T HE development of silicon edgeless strip detectors was stimulated by the TOTEM experiment at CERN for detection of protons scattered at very small angles (close-tobeam applications) [1,2]. To do this, the detector must be placed in close proximity to the beam, and the sensitive region of the detector must be negligibly close to its physical edge.…”

“…The key "element" affecting the operation of this structure is the damaged surface of the sensitive cut which governs the potential and electric field distribution in the adjacent bulk. The first simulations of the main characteristics of p-on-n edgeless detectors are described in [2], [4], in which the software ISE-TCAD was used. However, the model with multiple parameters which was applied in these simulations fails to define the major factors responsible for the certain detector characteristics.…”

An Advanced Double SOI CMOS Pixel Detector Termination With Trench Interspace

“…For reducing the termination area and being compatible with the standard planar detector, a current terminating structure (CTS) is proposed [8], [9]. The Current Terminating Ring (CTR) collects the current generated at the highly damaged region close to the edge, where it is cut, thereby avoiding its diffusion into the sensitive volume.…”