Ponente
Descripción
The SuperKEKB collider will undergo a major upgrade at the end of the
decade to reach the target luminosity of 6 10^35 cm-2 s-1, offering the
opportunity to install a new pixelated vertex detector (VTX) for the Belle
II experiment. The VTX will be more robust against the expected higher
level of machine background and more performant in terms of standalone
track finding efficiency.
The VTX design matches the modified interaction region and includes five
layers, spanning radii from 14 mm to 135 mm.
All layers are equipped with the same depleted-MAPS, OBELIX, designed in
the Tower 180 nm technology, which pixel matrix is derived from the TJ-
Monopix2 sensor originally developed for the ATLAS experiment. Featuring a
33 μm pitch, OBELIX integrates hits over 100 ns while dissipating less
than 200 mW/cm2 at an average hit rate of 60 MHz/cm2. The digital trigger
logic matches the 30 kHz average Belle II trigger rate with 10 μs trigger
delay and a maximum hit rate of 120 MHz/cm2.
The two innermost layers (iVTX) have a sensitive length of about 12 cm and
aim for a material budget below 0.2 % X0/layer, benefitting from air
cooling. One ladder is made of a 4-sensor wide module cut out from
processed wafers and submitted to post-processing operations in order to
connect them at one end.
The three outer layers (oVTX) target material budget ranging from 0.3 % X0
for the shortest length up to 0.8 % X0 for the 70 cm-long and outermost
layer. The ladder concept uses a light mechanical structure supporting a
liquid-cooled plate in contact with the sensors connected to a flex
printed cable.
We will review all project aspects: tests of the TJ-Monopix2 sensor,
OBELIX-1 design status, prototype fabrication and tests for the iVTX and
oVTX concepts, including their cooling.
