Silicon Readout Chip

 

The design of the TOSCA experiment contains a silicon micro-strip tracker. The prototype system used in NOMAD [14, 15] uses the VA1 read-out chip, which is fully read out after each trigger. To allow the readout of many triggers within the 10  sec spill, the VA1 chip design has to be modified.

The VA1 consists of 128 charge sensitive low-noise preamplifiers followed by CR-RC shapers, track-and-hold circuitry, output multiplexing and a multiplexed calibration input. After an external trigger, the sequential readout is performed by activating the output shift registers, using a clock operating at a frequency of 1 MHz.

The modification of the VA1 chip addresses the following requirements:

• Channel by channel multi-buffering capability.
• Optimisation of the signal-to-noise performance for the current detector design [16].

The present design studies show that the above requirements can be fulfilled, making it possible for the VA1 readout chip to operate under the conditions of the NGS.

The possible overlap of information between high multiplicity events and other neutrino events recorded during the same spill can be cured by the implementation of a fast clear driven by inhibiting the processing of these high multiplicity events through an external trigger.