Present and past activities

A "physics prototype" of a SiW ECAL has been produced, and tested in particle beams from 2006. The scope of this project is the prove that a SiW ECAL can be successfully operated, calibrated, simulated and understood.

At present (2011), a second generation "technical prototype" is under construction to better understand the technical realisation of a large scale ECAL in a full detector.

Physics prototype

A small prototype Si-W ECAL was constructed to test the feasibility of this technique. It has a transverse size of 18x18 cm2, and 30 layers of silicon detectors. The silicon detectors were segmented with a granularity of 1x1 cm2, giving a total of around readout 10,000 channels.

This prototype was exposed to test beams during the years 2006-2008, at the physics laboratories at DESY, CERN and FNAL. Beams of electrons, positrons, pions and muons were used.

The response to electrons has been measured, and showed that the detector had a good linearity, and a sufficiently good energy resolution. It behaved as expected from GEANT4-based computer simulations developed within the group. It has therefore validated the general principles of such a detector.

Studies of pion interactions have concentrated on the comparison of different simulation models of hadronic interactions with the collected data.

3DProtoH_small.png physProtoPhoto_small.jpg
physics prototype design mechanical structure of physics prototype gluing of Si sensor
ProtoAnglePict.png slabPhoto_small.png
physics prototype in beamline detector slab

Technological prototype

At present (2010) a second prototype is being constructed, which aims to address the issues connected with the production of a full-scale ECAL, and its integration into a full detector. This includes:

mechanical structure
The structure must be strong and rigid to support the large mass of the tungsten absorber, as well as the fragile silicon sensors. The space taken up by non-active parts of the structure must be minimised to prevent large non-instrumented areas of the detector. The design must also be relatively easy to manufacture. A carbon-fibre based composite material is used, with a modular design allowing each piece to be checked at various points during assembly.

silicon sensors
The design of the silicon sensors is being advanced. Particular challenges are the reduction of the small dead zone at the edge of each sensor (in which the "guard ring" - used to prevent high voltage breakdown - is situated), and the capacitative cross-talk between the guard ring and the pixels at the sensor edge. Contacts with industrial partners are being pursued, in order to understand ways in which the price of the sensors can be reduced.

front-end electronics
The next prototype will have the front-end ASICs embedded within the detector volume. This places strong constraints on the power they can dissipate, since active cooling must be avoided to prevent the use of bulky cooling systems within the detector. The drive to low power includes the use of "power pulsing", the turning off of the chips when no collisions take place (the expected beam structure of the ILC is 5 bunches of 0.5 ms per second, implying a turn on/off at 5 Hz).

Active Sensor Units
The sensitive parts of the detector will be made up of Active Sensor Units (ASU), each with a size of 18x18cm2. This is based on a thin printed circuit board (PCB) (<1mm thick), on one side of which are glued the silicon sensors, with the ASICs bonded within the PCB on the other side. All power, slow control and data are routed through the PCB.

The connection of several ASUs into a long detector slab requires robust and reliable mechanical and electrical inter-connections. These must then be integrated into the detector slabs, consisting of a carbon-fibre structure with a tungsten layer at its centre, and two strings of ASUs on either side, together with a copper layer to extract heat to wards the end of the slab.

The heat produced by the front end electronics and the part of the data acquisition system inside the detector must be extracted. A leakless water cooling system is being developed for this purpose. Also important is the integration of such a system into a final detector.

data acquisition system
A CALICE-wide data acquisition system is being developed. This has a modular design, and is largely based on off-the-shelf components. A first stage (the Detector Interface card - DIF) is connected to the end of each detector slab. The data are then concentrated in a Local Data Aggregator (LDA) before being passed via an optical link to the outside world.

This prototype will be tested in particle beams in the coming years (2011-)

demonstrator_small.jpg EUDET_module_small.jpg themaltest_small.jpg
mechanical demonstrator module full mechanical structure cooling system tests
WaferHamamastu1b_small.png fev7.png SKIROC2_1_small.JPG
Hamamatsu Si sensor (18x18 cm2, 5x5mm2 pixels) prototype front end board with ASICs ASIC bonded onto PCB

-- DanielJeans - 17-Jun-2010

Topic attachments
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JPEGjpg EUDET_module_small.jpg r1 manage 25.1 K 2011-01-07 - 16:34 UnknownUser mechanical_struc
JPEGjpg SKIROC2_1_small.JPG r1 manage 40.5 K 2011-01-07 - 16:33 UnknownUser skiroc2_in_fev
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