DELPHI Time Of Flight counters (TOF)

Technical description

The Time Of Flight detector consist in a single layer of 192 scintillation counters along the beam axis. The dimension of each single counter are 20 x 354 x 2 cm3. Each counter is provided with a Photo Multiplier tube PM in each of the both ends.

Here find picture of the dead zones of the TOF detector.

Here some day you will find a nice picture of the TOF detector.


Hardware and data acquisition

Our 192 counters are splitted in 96 counters in each side of DELPHI A, C. Each side contains 24 sectors of 4 counters each one (so 8 PMs)

Each sector digitilizes the TDCs of each 8 PMs in a 8 channel FASTBUS card called TSU. The TSU not only provides the TDC for its single channel but builds up the sector trigger via a mean timer circuit.

The ADC are digitilzed in a 96 channel module

The timing information of the sector trigger is digitilze in a TDC. That is used for the third level trigger.


The 192 counters are divided into 8 groups of 12 counters, covering each group 90 degrees of the Barrel region. 4 of these groups are located in side C and the rest in side A. The 8 octants are:

CRU Side C Right Up

CRD Side C Right Down

CLD Side C Left Down

CLU Side C Lefr Up

ARU Side A Right Up

ARD Side A Right Down

ALD Side A Left Down

ALU Side a Lefr Up

Quantities measured

When a particle crosses one of our scintillator counters generates a light pulse that propagates from its generation point to both ends of the counter where the pulse reaches a Photo Multiplier tube (PM). This devices convertes the light pulse into a electronic pulse. Each pulse is splitted in two and we measure:

- its arrival time TDC

- its charge ADC