by Tatyana Karavicheva []. Published: 29 April 2014

The T0 detector was designed and built and is operated by a Finnish-Russian team. The members come from two institutes in Finland (University of Jyväskylä and Helsinki Institute of Physics) and three in Russia (Institute for Nuclear Research RAS, Moscow Engineering Physics Institute, Russian Research Centre Kurchatov Institute).

The current T0 detector consists of two arrays of Cherenkov counters (T0C and T0A) positioned at the opposite sides of the Interaction Point  at distances of -70 cm and 370 cm. Each array has 12 cylindrical counters equipped with a quartz radiator and a photomultiplier tube.

Since its  installation during Easter of 2007 T0-C remains inaccessible, hidden under the layers of FMD and ITS detectors and services. Standing from left to right: A.Bogdanov, A.Reshetin, A.Kurepin, and F.Guber.

Small but important

T0 is primarily a trigger and timing detector but it also played a crucial role during the high luminosity part of Run 1.   Being the first of the ALICE detectors to be turned on, T0 provided a direct feedback to the LHC team enabling them to tune and monitor the collision rate at Point 2. This valuable service allowed the first beams for ALICE to be delivered on time.

T0-A array after installation in January 2008.

The fastest got even faster

During Run 1 T0 was delivering the trigger signals to the CTP just 625 ns after the collision time; being one the fastest of the ALICE detectors. Trigger consolidation for Run 2 requires reduction of that latency to below 425 ns. To achieve such a drastic cut T0 had to relocate the entire electronics from the racks O18-19 to the racks close to the CTP (C33-34) and reroute and shorten the cables. This Herculean task has already been completed and the T0 team is now recommissioning the detector.

Smiling faces next to the relocated T0 electronics. From left to right: D.Serebryakov, A.Reshetin, T.Karavicheva, and W.H.Trzaska.

FIT for the future

The ALICE upgrade for Run 3 is a challenge for all the system. To face that challenge T0, V0 and FMD teams have joined forces and resources to design, build and operate Fast Interaction Trigger (FIT). FIT will provide the functionality of both the T0 and V0 maintaining excellent timing and trigger properties together with the desired centrality and event plane resolution.  It will consist of the Cherenkov radiators (T0+) and scintillators (V0+). Both will use common fast electronics, digitization, and readout as outlined in the Chapter 10 of the Readout & Trigger System TDR:

Proposed integration of FIT and FMT. T0+ units are shown as rectangular boxes around the beam tube. (Drawing by Corrado Gargiulo.)