Arachnid is a collaboration of scientists from Birmingham, Bristol, Daresbury Laboratory, DESY, QMUL and the Rutherford Appleton Laboratory focused on design and testing complementary metal oxide semiconductor (CMOS) devices for scientific applications.  In particular we are working on Monolithic Active Pixel Sensors (MAPS).  This R&D programme is a successor to the SPiDeR programme that developed a particular variant of MAPS devices that are referred to as INMAPS.  There are four aspects to our research activities

  • Sensor characterisation: The Collaboration is working on characterising novel technology present in the Cherwell chip that was designed by the RAL microelectronics division.  This caracterisation includes benchmarking noise pedestals, and response to radiation sources in a controlled laboratory environment.
  • Radiation hardness tests: In order to understand the practical limits of this technology the Cherwell chip will be tested in a number of different environments, including proton and photon irradiation.  This will enable us to determine the lifetime of INMAPS devices in particle and nuclear physics applications, and any potentially related commercial derivatives.
  • Advanced usage: As the technology relies on a variant of the commercial CMOS process we also plan to investigate device response as a function of temperature, mechanical deformation, and in strong magnetic fields to verify the limits of the technology.
  • Design for a real world application: The predecessor devices tested under CALICE and SPiDeR were inspired by the potential use as a large area sensor array  for use in calorimetry.  The performance characteristics and potential cost savings that could be involved in adapting this technology into a fast imaging device make INMAPS a potentially attractive solution for pixel vertex detectors.  We aim to design such a device as a part of the Arachnid programme.


The sensor we are testing during this R&D programme is the Cherwell chip, a novel CMOS sensor that has been designed with low noise imaging in mind, that has a number of intrinsic features of possible interest for both scientific and commercial applications.  The chip itself if 5mm x 5mm, and we require a limited ammount of infrastructure in order to read this out.  This infrastructure includes a DAQ board, with sattelite COB card (Chip-On-Board), and a USB readout card in order to make the device portable and easy to set up at remote locations for testing.  The following image shows the DAQ board with an un-populated CPB card mounted on it.




The people involved in the Arachnid project at QMUL can be found here.


We use EVO for general Arachnid meetings and log the talks in the Arachnid INDICO area.  In order to participate in the bi-weekly meeting (Wednesday's at 14:00 UK time), follow this link.  The evo phone bridge id is 120241, and instructions on how to participate via skype can be found on the EVO web site.


The Arachnid collaboration was mentioned briefly in a recent Physics World "Big Science" supplement in the context of this technology being a potential solution that was a potential technology for the cancelled SuperB experiment.  The technology is also of interest to the ALICE experiment at CERN in the context of a planned detector upgrade, and for future Higgs Factory/ILC or CLIC detectors.

Useful links