1. Pixel detector development: sensor
Epitaxial wafer with sensor: first design
5 readout chip sensor
Production of pixel sensor prototypes using epitaxial silicon layers on a thinned Cz substrate. Different epitaxial layers under test (50 m / 75 m / 100 m). Corresponding target thickness: 100 … 150 m.
Photo left: Produced test wafer with different sensors and diagnostic structures.
pixel
Pad for
bump bonding
4 readout chip sensor

2. Pixel detector development: readout electronics
ToPix specifications:
Custom made pixel readout chip developed using 130 nm CMOS technology
Pixel readout size
100mm x 100mm
Chip active area
11.4 mm x 11.6 mm
dE/dx measurement
ToT, 12 bits dynamic range
Noise
<0.032 fC (200 e-)
Clock frequency
MHz
Time resolution
6.4 ns (1.85 ns rms)
Power consumption
<<500 mW/cm2
Max. event rate
@2·107pbar-p ann/s:
~ 12·106 hits/(cm2·s)
Custom made front-end (ToPix) for the pixel detectors. ToPix-specification.

3. Pixel detector development: Front-end electronics
ToPix_v2: Custom made pixel readout chip
Electrical scheme of the readout cell 5
Ifb
Cint
preamp
comp
baseline
restorer
DAC 12 7
mask
le_reg
te_reg
cfg_reg
control
logic
ToT
bus
CLK:
INPUT
Prototype with 320 readout cells
ANALOG
DIGITAL
Custom made front-end (ToPix) for the pixel detectors. ToPix-specification: …….PLEASE FILL IN Top: Photograph of a reduced prototype (ToPi_v2) connected to ist test board (left) and floor plan (right). Bottom: Pixel cell schematics. Floor plan (left) and Schematics of a pixel cell readout (right).
latch
enable
mask
Pixel readout cell,
100 mm x 100 mm size 3

4. Channel to channel ToT dispersion:
Characterization of front-end and sensor prototypes
ToPix: Custom made pixel readout chip
Channel to channel ToT dispersion:
 10 %
Epi-Sensors
Tests with a 90Sr source
Overall characterization measurements indicate full functionality and a good perfomance. Moreover, dedicated test with neutrons and gamma rays prove sufficient radiation hardness TOP: Characterization of the ToPix chip: Gain versus measured time-over treshold indicating good linearity over a high dynamic input range (left).
The Time over Threshold technique works also when the preamplifier signal is saturated.
Channel to channel variations are independent from the induced charge signal and stay in the order of 10%. (Right)
BOTTOM: Characterization of pixel sensors with different epi layer thickness. Leackage current (left),
Middle: Distribution of the depletion voltage for different epitaxial diodes.
Right: Treshold values for minimizing ionizing particles (MIP) obtained in a measurement with Sr-90 of some assemblies
with Alice pixel readout (ToPix is under development!).
Values agree well with theoretical expectations.

5. Measurements with epitaxial pixel prototypes connected to ToPix front-end chip with wire bonding
Left: Photograph of the ToPix_v2 prototype wire bonded to his testing board. Some pads are wire connected to pixel devices.
Right: 60 keV gamma spectrum as obtained using the Time over Threshold information.
Epitaxial silicon pixel size: 125mm x 325mm, 50 mm thick