Development of the Quad Focus GridPix Gaseous Tracking Detector
Development of the Quad Focus GridPix Gaseous Tracking Detector
Samenvatting
A Quad Focus GridPix Gaseous Tracking Detector is under construction, to allow calibration and test beam measurements to validate the working principles of the (quad) GridPix detectors while using a focused electric field. The development is well on its way: both measurements should be able to be conducted in the near future.
The detector is based on the GridPix sensor which is a Micromegas detector using the Medipix family of chips. The Medipix family of chips are charge sensitive pixel based CMOS chips. Specifically the TimePix1 chips are used. They allow for clocked measurements adding a third dimension to the measurements, i.e. time. The Micromegas detector is a modern version of the Geiger counter. A cathode foil is placed above a micro mesh structure which rests with insulating pillars on the readout anode. The cathode and the mesh have a high voltage potential applied creating an electric field. The electric field between the micro mesh and the readout anode is much greater than the field above the mesh. The whole is filled with a gas. An energetic charged particle is able to traverse this gas volume and ionize it, leaving behind a track of electron-ion pairs or clusters. The electrons will drift down to the readout anode due to the electric field. When passing through the micro mesh structure they will accelerate allowing them to release additional electrons which can in their turn release electrons. An electron avalanche is created, sufficient enough to be detected. Single electrons can be detected. The GridPix detectors are Micromegas detectors. The micro mesh structure is integrated on top of the Medipix chips. Each hole of the mesh (now a grid) has one aligned pixel. The insulating pillars do not cover the pixel input pads. This is achieved by wafer post processing.
Previously the GridPix gaseous detectors were tested using homogenous electric fields. The Quad Focus detector will use a focused electric field. This can reduce the production costs because a smaller readout surface is required to read the same or larger gas volumes. This requires calibration measurement to correct for the non-homogenous electric field and test beam measurement where there also is a magnetic field present which will alter the perceived tracks because the electric and magnetic field are not fully parallel to each other. Overall the feasibility of the corrections required when the detector is deployed (a magnetic field present) need to be assessed.
The gaseous tracking detector are promising to use as a tracking detector in for example the ATLAS project. Those detectors are able to record partial tracks from which the whole track can be reconstructed. Currently semiconductor based tracking detectors are used, which only result in a two dimensional measurement point from which the overall track has to be reconstructed.
One component of the GridPix detectors is the protection layer on top of the pixel input pads. Research and development of this layer resulted in a new method that allows for the measurement of high specific resistivity thin films which is based on the Micromegas detector.
Organisatie | De Haagse Hogeschool |
Opleiding | TIS Technische Natuurkunde |
Afdeling | Faculteit Technologie, Innovatie & Samenleving |
Partner | Nikhef, National Institute for Subatomic Physics |
Jaar | 2015 |
Type | Bachelor |
Taal | Engels |