Development and construction of the Belle II DEPFET pixel detector

Abstract

The construction of the new accelerator at the Japanese Flavour Factory (KEKB) has been finalized and the commissioning of its detector (Belle II) is planned by early 2017. This new e + e − machine ("SuperKEKB") will deliver an instantaneous luminosity of 8 × 10 35 cm −2 s −1 , which is 40 times higher than the world record set by KEKB. In order to be able to fully exploit the increased number of events and provide high precision measurements of the decay vertex of the B meson systems in such a harsh environment, the Belle II detector will include a new silicon vertex detector, based on the DEPFET technology. The new pixel detector, located close to the interaction point, consists of two layers of active pixel sensors. The DEPFET technology combines the detection and the in-pixel amplification by the integration, on every pixel, of a field effect transistor into a fully depleted silicon bulk. In Belle II, DEPFET sensors thinned down to 75 µm with low power consumption and low intrinsic noise will be used. In this paper, an overview of the latest results and the construction status are presented. Properties of small prototype matrices operated with close to final readout ASIC electronics have been characterized. In particular results from a combined test beam with full-size matrices are described.

The Monitoring System of the Belle II Vertex Detector

“…More details on the DEPFET and the SVD can be found elsewhere [1] and an update on their construction status have been presented in two separate talks [4,5] of this workshop. In the following we underline the aspects relative to the VXD environmental and radiation conditions and their monitoring, already introduced in [6,7].…”

“…In April 2016, during a combined PXD+SVD Beam Test at DESY, a reduced monitoring system was installed in the VXD cartridge [4,5] containing prototypes of the PXD and SVD silicon sensors. The monitoring system included 32 NTC sensors with the final read-out system, one prototype fiber with 5 FOS sensors, a dew point transmitter connected with a 30 m sniffing pipe and a pump.…”

Micro-channel cooling in high energy physics

“…An SOI process to produce a thin all-silicon ladder with integrated micro-channels was recently demonstrated [12]. The process steps, outlined in Figure 4, represent an extension of the process [16] used to produce the DEPFET active pixel detectors for the Belle II vertex detector [17,18] and linear collider prototypes [19]. The process is fully compatible with the production of depleted silicon sensors.…”

The ILC Vertex Detector requirements

“…Already several mature technologies are approaching the specifications and some of them are already used in real experiments ( [10], [11], [12]). Those experiments offer less demanding requirements but are in the same order of magnitude as the one of the ILC.…”