1. 24-28 May, 2010 S. Mastroianni - 17th Real-Time Conference, Lisboa, Portugal ARGO-YBJ is a cosmic ray air shower detector based on a single layer of RPC covering a total instrumented area of ~ 10,000 m 2 High altitude site (YBJ, 4300 m a.s.l.) Layer of RPC covering  5800 m 2 (  92% active surface) with 0.5 cm lead converter + sampling guard ring Central Carpet: 130 Clusters, 1560 RPCs, 124800 Strips High space-time resolution (time  1 ns; space (strip)  6.5 ×62 cm 2 ) In stable data taking since Nov. 2007 (d.c. > 90%) Low Multiplicity trigger with 20 fired pads on the central carpet Trigger rate ~ 3.7 kHz, dead time ~ 4%, data acq. rate 3 MB/s; Aims: cosmic-ray physics (~1 TeV  a few PeV) VHE γ-astronomy (above ~300 GeV) S. Mastroianni INFN sez. di Napoli On behalf of the ARGO-YBJ Collaboration The RPC charge Read-Out system of the ARGO-YBJ detector To investigate the PeV energy region, we must have the ability to detect air showers with a secondary charged particles density of ~ 10 3 particles/m 2 the charge read out has been implemented by instrumenting each RPC with two Big Pads (BP 140  125 cm 2 )  1 Cluster = 24 BPs ~1.7  10 3 particles/BigPad Saturation of digital read out BigPad dens 1000/m 2 STRIP dens 22/m 2 Detector Longitude 90° 31’ 50” East Latitude 30° 06’ 38” North 4300 m above the sea level 90 Km North from Lhasa (Tibet) Collaboration Institutes: Chinese Academy of Science (CAS) Istituto Nazionale di Fisica Nucleare (INFN)

2. 24-28 May, 2010 S. Mastroianni - 17th Real-Time Conference, Lisboa, Portugal2 Rise time ~ 20-30 ns, Amplitude mV  tens of Volts; duration ~ 10 μs Filter/Linear Amplifier/ Shaper/Peak&Hold/12-bit ADC/Buffer Conversion enabled by a local density trigger (  16,  32,  64 hit particles for Cluster) The data read-out is managed by the Control Module that provides an interface with the Trigger and the main DAQ systems …. and each Control Module is connected in a daisy-chain network (link of 1Mbit/s) for control and monitoring purposes handles the calibration (~ 4000 BPs on a very huge surface with an extreme variation of the environmental parameters) by means of a 12-bit DAC on each CM board. Typical m.i.p. signals in the Big Pad with the detector operated at 9.5 kV with a gas mixture made of 15% Ar, 10% I-C 4 H 10 and 75% R143a. Amplitude mV  40 V Duration: > 10  s Rise Time : 20-30 ns The charge read-out system is based on a custom crate (MINICRATE) - two independent sections each one manages 24 BP signals form Cluster module 3 Charge Meter cards 1 Control Module for the data read-out The Charge Meter system  Input signal adapted to 50 Ω with a coaxial cable (12.5 m, attenuation of ~ 5%)  a voltage filter cuts out spikes greater than 40 V  linear amplifier with variable gain (VGA: 0.33, 0.66, 1.3, 2.5, 5, 10, 20 and 40 V)  constant fraction amplifier cuts the long tail of the input signal in order to realize the coincidences on the same shower (in about 500 ns);  Peak&Hold with a tilt time of 4mV/μs, for 2 μs.  ADC digitalization within 1.4 μs  data collection managed via a custom bus protocol operated on the backplane lines.

3. 24-28 May, 2010 S. Mastroianni - 17th Real-Time Conference, Lisboa, Portugal3 The central carpet (130 Clusters) has been instrumented with all the charge read-out electronics at the YangBaJing Laboratory since November 2009. The gain of the electronics was set at he moment in order to operate in the amplitude range 0-300 mV of the input signals allowing the overlap between digital and analog readout which is another way to calibrate the analog system. Three local trigger configurations were successfully tested (  16,  32 and  64 particles on at least one Cluster). In about six months of data taking, a few ten million showers have been reconstructed with the analog system. The Event selection Test results and data recorded by the charge read-out system confirm the design expectations, thus the ARGO-YBJ capability to operate at a very high particle density (> 10 3 particles/m 2 ). ~ Contained events Central carpet saturated ~ localized event

4. 24-28 May, 2010 S. Mastroianni - 17th Real-Time Conference, Lisboa, Portugal4 Thank you for your attention!  POSTER –PDAQ 26