Portruding from the midst of the D0 detector experiment is the highly stable, liquid argon calorimeter. It consists of three units, the Center Calorimeter (CC), and the two End-cap Calorimeters (EC). In order to achieve good energy scale accuracy and resolution, the electronics must be stable and produce very little noise. Because the calorimeter is so accurate and has excellent resolution, D0 can make precise measurements with electrons, photons, and jets using no tracking system. D0 has been able to perform measurements of many interesting physical quantities using the calorimeter, including precise measurements of the W boson and top quark masses. The goal of the calorimeter upgrade is to modify the calorimeter readout system so that it can perform even better to give very precise measurements.
Each calorimeter cell consists of a liquid argon cap between an absorber plate and a G10 board. The G10 board has a high-resistivity coating to which a potential is applied with respect to the absorber plate to create the drift electric field. Particles transversing the gap produce and ionized trail of electrons and ions. In the electric field the electrons drift towards the G10 coating, producing a current. The current induces and image charge on a copper pad etched on the G10 board under the resistive coat. A readout cell is formed from many pads grouped together.
The signal from each cell is brought to a feed through port on a resistive coaxial cable. Then the signal is carried from the feed through port to the preamplifier inputs on twist and flat cables. These preamps are small hybrid ceramic printed circuits which are mounted on a printed circuit motherboard. There are 48 to a motherboard. The preamps integrate the charge produced by the calorimeter cells to produce voltages. The pulses of voltage are carried again by twist and flat cables to the shaper and baseline subtractor (BLS). The BLS process removes slowly varying offsets in the input voltage. The outputs are then read out and digitized by the Analog to Digital Converters (ADC).
The components that need to be replaced
for the upgrade are the cables between the feed-through ports and the preamps,
the preamps and their motherboards, the shapers, BLS's and sample and holds,
the power supplies for both these systems, and a new charge injection pulser
system for calibration and monitoring stability. The timing, trigger
and readout control also need to be modified to handle the faster timing,
higher trigger rates and analog buffering expected in the later runs.
Simplified Schema of Calorimeter
Electronics
Simplified Diagram of the Calorimeter Data Flow Path
Calorimeter Pictures