TimePix ASIC

TimePix chip is designed as universal read-out chip for various types of radiation. It can be used in combination with pixelated semiconductor detector, with gaseous TPC (Time Projection Chamber) or without any sensor (electrostatically collecting electrons). In our team it is used preferably in combination with pixelated semiconductor sensor.

TimePix device with silicon sensor

The hybrid silicon pixel device TimePix was developed at CERN by Medipix collaboration with support of EUDET project. It is based on its successful predecessor Medipix2. The device consists of a semiconductor detector chip (ussually 300 um thick silicon) bump-bonded to a readout chip. The detector chip is equipped with a single common backside electrode and a front side matrix of electrodes (256 x 256 square pixels with pitch of 55 um). Each element of the matrix (pixel) is connected to its respective preamplifier, discriminator and digital counter integrated on the readout chip. The noise of analog circuitry is about 650 electrons. Each TimePix pixel can work in one of three modes:

  1. Medipix mode - Counter counts incoming particles.
  2. TimePix mode - Counter works as a timer and measures time of the particle detection.
  3. Time over threshold (TOT) mode - Counter is used as Wilkinson type ADC allowing direct energy measurement in each pixel.

Each individual pixel of the TimePix device in TOT mode is connected to its own analog circuitry and AD converter. Thus the device contains 65 536 independent ADCs. All of them have to be individually calibrated.

Timepix device
Pixel detector Timepix. Device consists of two chips connected by bomp-bonding technique. The upper chip is pixelated semiconductor detector (ussualy Silicon). The bottom chip is ASIC read-out containing matrix of 256 x 256 of preamplifiers comparators and counters.