Front‐end Electronics of
FoCal‐E PAD detectors
1 June, 2016.

Motoi INABA
Tsukuba University of Technology, Faculty of Industrial Technology.
National University Corporation for the hearing impaired and visually impaired in Japan.

P.2 of 15BackgroundAs one of the ALICE detector upgrade plans, we are going on testing
the FoCal‐E PAD detector prototype and developing some peripheral
electronics in 2014 and 2015.
For example,• The SRS crate with a power unit,(Automatic shutdown)• Temperature monitors,• Isolated regulated LV power circuits,• Isolated HV generators,• Trigger circuits, etc.

The SRS crate with a power unit

Temperature monitors

A trigger circuit

FoCal‐E PAD module (prototype)P.3 of 15

A FoCal‐E PAD detector is the Si‐W calorimeter. One module has
4 pairs of tungsten tiles (t = 3.5 mm) and Si‐PD sensors (t = 0.5 mm).
Size: 11.25 x 11.25 mm2 ( = 1.266 cm2 )

Si

Si

Si

Si‐PD sensor (11.30 mm pitch)

Si

12364 channels

Beam
94 mm

93 mm

93 mm
62 63 64W

W W W
< Side view >93 mm< Back view >P.4 of 15

FoCal‐E PAD module (prototype)

Signals of 4 Si‐PDs are summed and amplified. And, it is given as
two single‐end signals with attenuation factors of 1/1 and 1/16.

PD PD PD PD‐HVRRCARCRCC

Positive output
Negative output

P.5 of 15

Readout system

In order to readout waveforms of 64 analog signals per module,
we used ORNL summing boards and SRS DAQ system with APV25hybrid boards so far.
4 layers x 64 channels

Si‐PD Si‐PD Si‐PD Si‐PDx 64

A summing board
64 channels

APV25 hybridLow voltage

HDMIcableHigh voltageFoCal‐E PAD modules (x 4)Signals of 4 Si‐PD withthe same channel ID on
different layers are
summed at the first stageof the ORNL summing board.

12

38 HDMI ports (x2)

ADC card

FEC card

16 ADCs

Vertex‐6FPGA

12‐bit40MS/s

A trigger signal

DAQ
LANcablePowerSRS crate(mmDAQ)PC

FoCal‐E PAD module prototype
APV25hybrid

APV25 hybrid
ORNL
summingboard

ORNL
summingboard

A copper shield
Isolatedframes

P.6 of 15

4 FoCal‐E PAD modules

P.7 of 15

FoCal‐E prototype at CERN PS complex

P.8 of 15

Signals (One trigger event data)
2nd and 3rd FoCal‐E
PAD modules hadlarge signals according
to the EM shower.

P.9 of 15

The mmDAQ monitor (All channels)

However, we need to
1st

2nd
3rd
Channel by channel

4th
The APV25 hybrid has
128 input channels.
Ch.1 ‐ Ch.64 :Positive signals (1/1)
Ch.65 – Ch.128
Negative signals (1/16)

Signals (Multiple trigger events data)(x1)
Width ofpedestal

P.10 of 15(x 1/16)

The available
dynamic range

The available
dynamic range

Positive signals (0.5 GeV/c)

Negative signals (0.5 GeV/c)(x1)(x 1/16)

It has reached the limit.
It would reach the limit
at about 30 GeV/c.

Positive signals (5.0 GeV/c)

Negative signals (5.0 GeV/c)

Wider dynamic range and better S/N

P.11 of 15

In order to measure larger signals under the higher energy, wider
dynamic range is required.
It would need triple attenuation factors such as 1/1, 1/10 and 1/100
if APV25 hybrid boards are used for taking 500 Gev/c data.
In order to measure smaller signals, it is necessary to reduce thenoise level on signal lines. It would be strongly related with theenergy resolution of the FoCal‐E PADs.
S/N was already improved to a certain extent using new isolated
LV / HV circuits, new frames with the isolation coating (byUniversiteit Utrecht) and better ground lines. However, weshould make another attempt.
Through the advanced circuit simulation, some weak points were
found in a current FEE design.

New frames for FoCal‐E PADs

P.12 of 15

Much noise came fromthe ground frame toTungsten tiles of theFoCal‐E PAD modules
that was connectedwith Cathode of Si‐PD.

New frames with theIsolation coating fabricatedby Universiteit Utrecht
worked very well.

P.13 of 15

Other solutions

A summing board has a key to get the enough wide dynamic range.
I started making a new summing board for the coming beam testat CERN SPS complex in September.
A new summing board includes• voltage followers to improve the linearity of the summed signal• triple amplification / attenuation factors (1, 10 and 100 times)• the fully differential signal processing to improve S/N, and• transformers to isolate the signal ground from the APV25 ground.
Si‐PD
Si‐PD

ESD
ESD

Si‐PD

ESD

Si‐PDESD

Buffers

AmplifierSummingtrans.

Amplifier(A=10)(A=1/10)(A=10)
Differential(A=1) signals

1:1

trans.
trans.

Passive
attenuator

A=100
A=10
A=1

APV25 hybrid
APV25 hybrid

x 64 channels

P.14 of 15

New readout system

As one of possibilities, we are thinking to use VMM3 hybrid boards
instead of APV25 hybrid boards under CERN RD51 collaboration.
It is expected to obtain better S/N since the VMMx family ASIC has
analog‐to‐digital converters.
FoCal‐E PAD

Si‐PD Si‐PD Si‐PD Si‐PDx 64

This hardware can be replaced toa simple digital interface card.

A new summing board
64 channels

VMM3 hybrid
Low voltage

A trigger signal

D cardFEC card

HDMIcable

High voltage
FoCal‐E PAD modules (x 4)LANcablePower
SRS crate

DAQPC

P.15 of 15

VMM3 (after VMM2)

We can use the same FEC card continuously. The D cards (prototype)were reproduced in Japan in 2015. The new D cards will be available
shortly.
The VMM2 hybrid prototype wastested in 2015 and the new VMM3hybrid prototype for testing isunder the fabrication.
D cardVMMx

FEC cardThank you for your attention.