Development of a timing detector for the TOTEM experiment at the LHC

Abstract

The upgrade program of the TOTEM experiment foresees the installation of timing detectors inside vertical Roman Pots to allow the reconstruction of the longitudinal vertex position in presence of event pile-up in high β * dedicated runs. The small available space inside the Roman Pot and the required time precision led to the study of a solution using single crystal CVD diamonds. The sensors are read-out using fast low-noise front-end electronics developed by the TOTEM Collaboration, achieving a signal-to-noise ratio larger than 20 for MIPs. A prototype was designed, manufactured and tested during a test beam campaign, proving a time precision below 100 ps and an efficiency above 99%. The geometry of the detector has been designed to guarantee a uniform occupancy in the expected run conditions keeping, at the same time, the number of channels below ten. In fact, each detector uses four diamond crystals of 4.5 × 4.5mm 2 : one is segmented in four pixels, another in two, while the remaining pair is metallized with a single electrode. The detectors are read-out using the SAMPIC chip, a fast sampler designed specifically for picosecond timing measurements with high rate capabilities. Four aligned detectors will be installed in each Roman Pot to achieve a final precision below 50 ps. The first set of prototypes was successfully installed and tested in the LHC in November 2015.

Diamond Detectors for Timing Measurements in High Energy Physics

“…This section describes the main concepts needed to design a front-end amplifier for a diamond detector, with particular focus on timing applications. More detailed studies are discussed in [23] and [35].…”

Fabrication and Characterisation of 3D Diamond Pixel Detectors With Timing Capabilities

“…The gold-sputtered pads on the sensor are connected with 25 μm aluminium wires to the input pads of a two stage amplifier with a shaping time of 1 ns and a bandwidth of 1 GHz. A single board, designed at the University of Kansas, hosts eight such readout channels with independent amplification and shaping chains [37,38]. A metallic cover can be installed on the board to protect the device from electromagnetic interferences, dusts and mechanical shocks that could damage the bonding wires.…”

“…The position of the peaks relative to muons, pions and protons was then computed relative to the positron peak. Similar techniques have been employed and validated in the past on the same beam line, using different timing detectors [38,42].…”

Measurements of timing resolution of ultra-fast silicon detectors with the SAMPIC waveform digitizer

“…We start by considering the signal average in usually negligible for fast timing, the time walk is assumed to be corrected and the jitter depends on the noise and the slope of the signal as shown in Equation 2. More details can be found in chapter 6 of [30]. The jitter from the TCD is assumed to be uncorrelated.…”