The right Sensor at the right time

Very high speed pixilated particle detector for a high energy physics collider beam.  The purpose of the overall detector is to track and reconstruct the trajectories of charged particles after sub-atomic high energy collisions.

The desired spatial resolution of the detector was <10mm.  To maintain such a resolution, the total RMS readout noise of the array had to be below 100 e-.  In addition, the electronics had to survive intense radiation exposure due to the proximity to the beam (less than 10 cm).  

The detector contained multiple cylindrical layers of these detectors surrounding the collider beam pipe.  The total number of pixels in these multiple planes added up to ~2x10⁹.  The effective frame rate of these detector arrays is the rate of collisions in the beam, which in this case was every 132nS (~7.57 MHz).  In order to read all the pixels, the total data rate would have been 7.57MHz x 2x10⁹, or 15x10¹⁵ Hz.  Clearly, the data rate is too high, and a new solution had to be found.

By using the fact that less than 1% of the pixels would ever be triggered on any particular collision event, a novel "sparse" data reduction technique utilizing "smart pixel technology" was developed to read only those pixels containing data.  The technique was later patented under "Data Push Architecture".  To implement the technique, Adept developed a high speed, low noise, low power CMOS pixel.  The pixel incorporated a low noise preamplifier and a 1 bit analog to digital converter (ADC) with analog and digital memory.  The pixel "decided" on its own if any data was present, signaled to the periphery when data was present, and saved the data in order to be read out when the system resources were free.

The prototypes arrays were designed, processed and tested.  The arrays met all goals.  The pixel and periphery circuits were transferred to the customer for assembly into much larger arrays and fabrication. 

Copyright © 2002 Adept IC Design
Last modified: October 18, 2000