THE PAST

(not to be forgotten)


The prehistory.
The Genova group has been member of the DELPHI collaboration since the very beginning. The first simulations of hadronic events, used for the preliminary design of the detector, were done in Genova.
The group was primarily interested in the development of the electromagnetic calorimeter. A prototype of a liquid argon detector was realized and successfully tested. However, the HPC technique was finally chosen.

The High density Projection Chamber.
The Genova group took part to the development and test of this detector based on highly new ideas previously applied only to some small scale models with techniques useless at a larger scale. The narrow drift channels that physicists and technicians in Genova realized to study such effects as attenuation and drift velocity, are still a part of the present monitoring system.
To have an idea of the effort, consider that in the HPC there are 144 modules, mostly containing 16 "accordeons" having a linear length of about 25 m. Each "accordeon" has 60 lead wires, glued with a inter-wire gap of 200 microns. For a correct behavior none of those modules is allowed to show more than a few short circuits: this means 1 s.c./10 km. Genova was the only collaborating lab to produce full modules (read-out chambers and trigger scintillators not included).
To control the dead region around 90°, a system of lead-scintillator counters was also realized in Genova.

The software.
The experience gained during the above mentioned tests, was extremely useful for the software reconstruction of the showers in the HPC. The most relevant contributions from Genova are the geometrical shower axis reconstruction and the so called "second step" which completes the shower definition using information from other sub-detectors. Quantitatively about 1/3 of the official HPC reconstruction software was developed in Genova. HPDRAW, one of the two programs for the interactive display of HPC data, was also written here.
A sample of the over 34.000 line code for shower reconstruction in HPC.

Slow controls.
Another contribution was the realization and management of the HPC Slow Controls System which is in charge of remote controls and monitoring of the detector. More in detail it controls the High Voltages power supplies (both drift and proportional chamber voltages) and it monitors the Low Voltages (preamplifiers, etc.). Moreover it monitors and logs important detector parameters. The Genova group took care both of the hardware installation and of the relative software.

The second level trigger in TPC.
The trigger is based on a parallel algorithm implemented on a VLSI chip mounted on FASTBUS cards. Both the algorithm and the chip have been developed in Genova.

The Forward Rich.
While not directly involved in the construction of this technologically new detector in DELPHI, members of the Genova group contributed to its final structure, mainly by realizing logarithmic response preamplifiers. The preamps work on the signal of a single photoelectron as well as on the ion deposition of a charged track. They eventually replaced the previously installed ones, for a total of 28.000 channels.


Back to Welcome page

Please, send comments, suggestions and requests to Umberto Trevisan