S. Mastroianni INFN sez. di Napoli On behalf of the ARGO-YBJ Collaboration

1. The RPC charge Read-Out system of the ARGO-YBJ detector S. Mastroianni INFN sez. di Napoli On behalf of the ARGO-YBJ Collaboration • Collaboration Institutes: • Chinese Academy of Science (CAS) • Istituto Nazionale di Fisica Nucleare (INFN) • ARGO-YBJ is a cosmic ray air shower detector based on a single layer of RPC covering a total instrumented area of ~ 10,000 m2 • High altitude site (YBJ, 4300 m a.s.l.) • Layer of RPC covering 5800 m2 (  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 cm2) • 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) Detector Longitude 90° 31’ 50” East Latitude 30° 06’ 38” North 4300 m above the sea level 90 Km North from Lhasa (Tibet) To investigate the PeV energy region, we must have the ability to detect air showers with a secondary charged particles density of ~ 103 particles/m2 the charge read out has been implemented by instrumenting each RPC with two Big Pads (BP 140125 cm2 )  1 Cluster = 24 BPs ~1.7103particles/BigPad BigPad dens 1000/m2 STRIP dens 22/m2 Saturation of digital read out S. Mastroianni - 17th Real-Time Conference, Lisboa, Portugal

2. The Charge Meter system Duration: > 10ms Rise Time : 20-30 ns Amplitude mV40 V • 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 • 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. 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-C4H10 and 75% R143a. 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. S. Mastroianni - 17th Real-Time Conference, Lisboa, Portugal

3. The Event selection ~ Contained events 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. Central carpet saturated ~ localized event 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 (> 103 particles/m2). S. Mastroianni - 17th Real-Time Conference, Lisboa, Portugal

4. Thank you for your attention!  POSTER –PDAQ 26 S. Mastroianni - 17th Real-Time Conference, Lisboa, Portugal