The KEKB machine and the Belle experiment in Tsukuba (Japan) are now undergoing an upgrade, leading to an ultimate luminosity of 8 × 10 35 cm −2 s −1 in order to measure rare decays in the B system with high statistics. The previous vertex detector cannot cope with this 40-fold increase of luminosity and thus needs to be replaced. Belle II will be equipped with a two-layer Pixel Detector surrounding the beam pipe, and four layers of double-sided silicon strip sensors at higher radii than the old detector. The Silicon Vertex Detector (SVD) will have a total sensitive area of 1.13 m 2 and 223,744 channelstwice as many as its predecessor.All silicon sensors will be made from 150 mm wafers in order to maximize their size and thus to reduce the relative contribution of the support structure. The forward part has slanted sensors of trapezoidal shape to improve the measurement precision and to minimize the amount of material as seen by particles from the vertex. Fast-shaping front-end amplifiers will be used in conjunction with an online hit time reconstruction algorithm in order to reduce the occupancy to the level of a few percent at most. A novel "Origami" chip-on-sensor scheme is used to minimize both the distance between strips and amplifier (thus reducing the electronic noise) as well as the overall material budget.This report gives an overview on the status of the Belle II SVD and its components, including sensors, front-end detector ladders, mechanics, cooling and the readout electronics.
The Belle II silicon vertex detector will consist of four layers of double-sided silicon strip detectors, arranged in ladders. Each sensor will be read out individually by utilizing the Origami chip-on-sensor concept, where the APV25 chips are placed on flexible circuits, glued on top of the sensors. Beside a best compromise between low material budget and sufficient SNR, this concept allows efficient CO 2 cooling of the readout chips by a single, thin cooling pipe per ladder. Recently, we assembled a module consisting of two consecutive 6" double-sided silicon strip detectors, both read out by Origami flexes. Such a compound of Origami modules is required for the ladders of the outer Belle II SVD layers. Consequently, it is intended to verify the scalability of the assembly procedure, the performance of combined Origami flexes as well as the efficiency of the CO 2 cooling system for a higher number of APV25 chips.
The KEKB machine and the Belle experiment in Tsukuba (Japan) are now undergoing an upgrade, leading to an ultimate luminosity of 8 × 10 35 cm −2 s −1 in order to measure rare decays in the B system with high statistics. The previous vertex detector cannot cope with this 40-fold increase of luminosity and thus needs to be replaced. Belle II will be equipped with a two-layer Pixel Detector surrounding the beam pipe, and four layers of double-sided silicon strip sensors at higher radii than the old detector. The Silicon Vertex Detector (SVD) will have a total sensitive area of 1.13 m 2 and 223,744 channelstwice as many as its predecessor.All silicon sensors will be made from 150 mm wafers in order to maximize their size and thus to reduce the relative contribution of the support structure. The forward part has slanted sensors of trapezoidal shape to improve the measurement precision and to minimize the amount of material as seen by particles from the vertex. Fast-shaping front-end amplifiers will be used in conjunction with an online hit time reconstruction algorithm in order to reduce the occupancy to the level of a few percent at most. A novel "Origami" chip-on-sensor scheme is used to minimize both the distance between strips and amplifier (thus reducing the electronic noise) as well as the overall material budget.This report gives an overview on the status of the Belle II SVD and its components, including sensors, front-end detector ladders, mechanics, cooling and the readout electronics.
The Silicon Vertex Detector of the future Belle II experiment at KEK (Japan) will consist of 6" double-sided strip sensors. Those are read out by APV25 chips (originally developed for CMS) which are powered by DC/DC converters with low voltages tied to the sensor bias potentials. The signals are transmitted by cable links of about 12 meters. In the back-end, the data are digitized and processed by FADC modules with powerful FPGAs, which are also capable of precisely measuring the hit time of each particle in order to discard off-time background.
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