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The smart diode array - 350nm chips


HVPixel1 is the first SDA sensor, it is implemented in 350nm AMS HV-technology. The chip contains a small array of pixels with CMOS electronics. The pixel circuits include a charge sensitive amplifier, a comparator and a digital part. Every pixel is able to detect a particle hit and to store the hit information.


The first high-energy particle spectra have been measured with individual pixels. First images of small objects have been taken with the matrix.

Schematics of the pixel in HVPixel1 chip.
Fe55 specturum recorded with HVPixel1 detector.


HVPixel2 is the multi-purpose test-chip with monolithic- and CCPD-structures. (CCPD - capacitively coupled hybrid-pixel detector.) HVPixel2 is implemented in 350nm AMS HV-technology. The chip contains one monolithic pixel matrix and one sensor-matrix for a CCPD, both implemented as the smart diode arrays. Additionally, the chip contains a matrix of the readout-cells that are used for the CCPD-sensor readout. The monolithic pixels (size 55x55 micrometers) contain CMOS circuits for particle hit detection. The CCPD pixels contain charge sensitive amplifiers.


The first test-beam measurement has been performed with the monolithic pixel matrix. The minimum ionizing particle (MIP) signal-spectrum has been measured. The single pixel signal is 1800e (most probable value - MPV).

The detection parameters such as the signal-to-noise ratio (SNR), the threshold dispersion, the detection efficiency have been measured on the matrix level. The measured SNR for MIPs is 30.

The first functional CCPD detector has been built. The CCPD detector consists of two HVPixel2 chips glued onto each other. The detection parameters have been measured. Radiation tolerance of at least 50MRad has been demonstrated by irradiating the chip with x-rays.

Photograph of the HVPixel2 chip.
3D layout of the monolithic pixel in HVPixel2 generated with the Gds2Pov software.
HVPixel2 in the in the test beam.
Signal spectrum measured in the test beam.
Efficiency of the monolithic matrix - detection of the signals above 660e is possible.
Efficiency of the CCPD matrix - detection of the signals above 948e is possible.


HVPixelM1 and HVPixelM2 are two variants of a larger monolithic SDA-detector with small pixels (21x21 micrometers). The chips are implemented in 350nm AMS HV technology. The readout is of the rolling shutter type. The pixel output signals are digitized on the chip by 128 ADCs.


The chips were extensively tested in the lab and in three test beam measurements. A detection efficiency of at least 98%, a spatial resolution of about 3.8 micrometers and a seed pixel SNR of nearly 30 have been measured in the beam-tests. After correction for the telescope resolution the spatial resolution is 3.1 micrometers.

Ptotograph of the HPixelM2 chip.
Schematics of the pixel in HVPixelM chips.
Na22 beta-spectrum measured with the HVPixelM matrix.
Test-beam results: MIP spectrum - single pixel SNR of 27 has been measured.
Test-beam results: Spatial resolution. After correction for the telescope resolution we measure a spatial resolution of 3.1 micrometers.
Test-beam results: Average efficiency of 98% has been measured. The inperfect efficiency is most probably caused by the effects of rolling shutter readout - one row is always inactive.

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