1. Electronics and data acquisition system of the extensive air shower detector array at the University of Puebla R. Conde 1, O. Martinez 1, T. Murrieta 1, E. Perez 1, H. Salazar 1, L. Villasenor 2 1 Facultad de Ciencias Fisico-Matematicas, BUAP, Puebla, Pue., 72000, Mexico 2 Instituto de Fisica y Matematicas, UMSNH, Morelia, Michoacan, 58040, Mexico villasen@ifm.umich.mx Abstract Field programmable gate arrays (FPGAs) are playing an increasing role in DAQ systems in cosmic ray experiments due to their high speed and integration and their low cost and low power consumption. In this paper we describe in detail the new electronics and data acquisition system based on FPGA boards of the extensive air shower detector array built in the Campus of the University of Puebla. The purpose of this detector array is to measure the energy and arrival direction of primary cosmic rays with energies around 1015 eV. The array consists of 10 liquid scintillator detectors and 6 water Cherenkov detectors (of 1.86 m2 cross section), distributed in a square grid with a detector spacing of 20 m over an area of 4000 m2. The electronics described also makes use of analog to digital converters with a resolution of 10 bits and sampling speeds of 200 MS/s to digitize the PMT signals. We also discuss the advantages of discriminating the PMT signals inside the FPGAs with respect to the conventional use of dedicated discrimination circuits. a) References J. Cotzomi, E. Moreno, T. Murrieta, B. Palma, E. Pérez, H. Salazar, and L. Villaseñor, The Water Cherenkov Detector Array for studies of cosmic rays at the University of Puebla, Nucl. Instr. and Meth. in Phys. Res. A., Volume 553, Issues 1-2 (2005) Pages 290-294.Volume 553, Issues 1-2 H. Salazar, O. Martínez, E. Moreno, J. Cotzomi, L. Villaseñor, O. Saavedra, Results from the Puebla extensive air showed detector array, Nuclear Physics B (Proc. Suppl.) 122 (2003) 251-254. J. Cotsomi, O. Martinez, E. Moreno, H. Salazar and L. Villaseñor, Extensive Air Shower Array at the University of Puebla for the Study of Cosmic Rays, Rev. Mex. Fis. Vol. 51 No. 1 (2005) 38-46. [L. Villaseñor and H. Salazar, Separation of Cosmic-Ray Components in Water Cherenkov Detectors, Nucl. Instr. and Meth. in Phys. Res. A., Volume 553, Issues 1-2 (2005) 295-298. Volume 553, Issues 1-2 30th International Cosmic Ray Conference, Merida, July 6, 2007 EAS-UAP Array (19º N, 90ºW, 800g/cm2) PMT EMI 9030 A PMT Electron tubes 9353 K 1. Experimental Setup 2200m a.s.l., 800 g/cm2. Located at Campus Universidad Autonoma de Puebla Hybrid: Liquid Scintillator Detectors and water Cherenkov Detectors Energy range 10 14 - 10 16 eV 5. “New” DAQ Electronics Trigger: Coincidence of 4 central detectors (40mx40m) NIM y CAMAC. Use of digital Osciloscopes as ADCs Rate: 80 eventos/h 3. Monitoring Use CAMAC scalers to measure rates of single partícles on each detector. Day-night variations <10%  /mean around 3% 4. Calibration (Control Experiments) ~74 pe Decay electron at 0.17 VEM = 41 MeV Indoors WCD: MPV of EM peak = 0.12 VEM ~ 29 MeV, i.e., dominated by knock-on + decay electrons Outdoors WCD: MPV of EM peak = 0.12 VEM ~ 29 MeV, i.e., dominated by EM particles ~ 10 MeV WCD Liquid Scint Muons deposit 240 MeV in 1.20m high water and only 26 MeV in 13 cm high liquid, while electrons deposit all of their energy. For 10 Mev electrons we expect: Mu/EM=24 for Cherenkov Mu/EM=2.6 for Liq. Scint. Outdoors Liquid Scintillator Detector: MPV of EM peak = 0.30 VEM i.e., dominated by EM particles ~ 10 MeV Motherboard based on Xilinx Spartan 2E FPGA ADC sampling at 200 MS/s: Two ADCs running 180° out of phase at 100 MS/s each Conclusions We have described the new DAQ system for the EAS-UAP air shower array. This new system takes advantage of the recent progress on on-chip fast ADCs and the ever faster and more powerful FPGAs. We have achieved “single channel” sampling rates of 200 MS/s at 10 bit by combing these modern advanced with the flexibility provided by on-chip programming using VHDL. The use of cheap GPS embedded receivers allows us to attach a precise time tag to each L2 trigger event for further off-line analyses. 10-bit ADC running at 200MS/s 16-channel discrimination cards Schematic diagram of ADC and Input/Output scheme of VHDL program Communication modules 6. Results Charge distribution for background muons Charge vs risetime for a WCD located indoors Amplitude vs risetime for a WCD located outdoors 2. “Old” DAQ Electronics