Chiavassa, A

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29th International Cosmic Ray Conference Pune (2005) 6, 313316Operation, Calibration and Accuracy of the Grande array of theKASCADE-Grande experimentA. Chiavassa , T. Antoni, W.D. Apel, F. Badea, K. Bekk, A. Bercuci, M. Bertaina ,J. Blu¨mer, H. Bozdog, I.M. Brancus, M. Bru¨ggemann, P. Buchholz, K. Daumiller,F. Di Pierro , P. Doll, R. Engel, J. Engler, F. Feßler, P.L. Ghia	, H.J. Gils, R. Glasstetter  ,C. Grupen, A. Haungs, D. Heck, J.R. Ho¨randel, K.-H. Kampert  , H.O. Klages,Y. Kolotaev, G. Maier , H.J. Mathes, H.J. Mayer, J. Milke, B. Mitrica, C. Morello	,M. Mu¨ller, G. Navarra , R. Obenland, J. Oehlschla¨ger, S. Ostapchenko , S. Over,M. Petcu, T. Pierog, S. Plewnia, H. Rebel, A. Risse, M. Roth, H. Schieler,J. Scholz, O. Sima, M. Stu¨mpert, G. Toma, G.C. Trinchero	, H. Ulrich, S. Valchierotti ,J. van Buren, W. Walkowiak, A. Weindl, J. Wochele, J. Zabierowski, S. ZagromskiandD. Zimmermann(a) Institut f¤ur Experimentelle Kernphysik, Universit¤at Karlsruhe, 76021 Karlsruhe, Germany(b) Institut f¤ur Kernphysik, Forschungszentrum Karlsruhe, 76021 Karlsruhe, Germany(c) National Institute of Physics and Nuclear Engineering, 7690 Bucharest, Romania(d) Dipartimento di Fisica Generale dell’Universita, 10125 Torino, Italy(e) Fachbereich Physik, Universit¤at Siegen, 57068 Siegen, Germany(f) Istituto di Fisica dello Spazio Interplanetario, INAF, 10133 Torino, Italy(g) Fachbereich Physik, Universit¤at Wuppertal, 42097 Wuppertal, Germany(h) Soltan Institute for Nuclear Studies, 90950 Lodz, Polandon leave of absence from Nat. Inst. of Phys. and Nucl. Engineering, Bucharest, Romanianow at University Leeds, LS2 9JT Leeds, United Kingdomon leave of absence from Moscow State University, 119899 Moscow, RussiaPresenter: A. Chiavassa (achiavas@to.infn.it), ita-chiavassa-A-abs1-he13-oralThe KASCADE-Grande experiment is in continuous and stable data taking since the beginning of 2004.TheGrande array, made of 37 plastic scintillators detectors (10 m  each) placed at a distance of 140 m fromeach other, has been set up to cover a surface (  0.5 km  ) big enough to study the primary cosmic rays in the10  -10  eV energy range. We present the status of the Grande array and discuss the calibration proceduresand the accuracies achieved in the particle density measurements. Energy deposits (in 4 cm thick scintillators)are measured from  5 MeV to  5  10  MeV, allowing us to cover the dynamic range required to study theprimary cosmic rays in the range previously mentioned. A comparison of the showers parameters reconstructedby the Grande and by the KASCADE arrays is shown.1. IntroductionThe KASCADE-Grande experiment[1] has been set up to study primary cosmic rays in the energy range from10  to 10  eV, its main goal is the detection of the knee of the iron component. This observation would con-firm the hypothesis that explains the knee of the primary cosmic rays spectrum with astrophysical motivations,and its existence is expected by the measurements of the KASCADE[2] and EASTOP[3] experiments.The experiment is located at the Forschungszentrum Karlsruhe, Germany, where, beside the existing KAS-CADE [4] array, two new detector set ups (Grande and Piccolo) have been installed. The experiment is ableto sample different components of Extensive Air Showers (electromagnetic, muonic and hadronic) with highaccuracy and covering a surface of 0.5 km  .314 A. Chiavassa et al2. The Grande arrayThe Grande array[5] is made by 37 stations of plastic scintillation detectors, 10 m  surface (divided into 16individual scintillators) and 4 cm thick. The distance between detectors is in average 137 m and they are locatedin a hexagonal grid (see fig.1 ). All 16 scintillators are viewed by a high gain photomultiplier (for timing andlow particle density measurements), the four central ones are additionally viewed by a low gain one (for highparticle density).For triggering stations are arranged in 18 clusters of hexagonal shape with six detectors surrounding a centralone. The minimum trigger requirement is the coincidence of the central and three neighbouring stations in onehexagon. The trigger rate is 5 Hz, the stability of the array is shown in figure 2 where the distribution of thenumber of counts (in 10 minutes bins) after the correction for the pressure variations is shown. The standarddeviation of the distribution is  1.1 times the standard deviation of a poissonian distribution, thus the nonpoissonian fluctuations are equal to 46% of the poissonian ones.KASCADEPiccolo-StationsGrande-Stationsx-coordinate [m]y-coordinate [m]12345678910111213141516171819202122232425262728293031323334353637Trigger-Cell 17(18)-700-600-500-400-300-200-1000100-600 -500 -400 -300 -200 -100 0 100Figure 1. Layout of the KASCADE-Grande experiment05101520253035402600 2800 3000 3200 3400 3600 3800 4000 4200 4400EntriesMeanRMS           1076  3412.  64.05Number of Triggers in 10 minutesNumber of EventsFigure 2. Distribution of the number of events, in 10 minutesbins, after the correction for the pressure coefcent.The analog signals of the high gain photomultipliers are fed into a charge amplifier, then are shaped and reachthe maximum amplitude after 8  s, the output is split in two channels that go through a final amplification. Thehigher densities are measured using the low gain photomultipliers whose signals follow the same electronicchain (without being split in two signals).To calibrate the peak sensing ADC we use a circuit that inject into the shaper-amplifiers a charge that ismeasured both by peak and charge sensing ADC. The charge values span over the whole peak ADC range, thecurves obtained allow us to convert each peak ADC count into a charge ADC count.The ADC value (in charge ADC scale) corresponding to the peak of the single particle spectrum is measuredin each station during run time. In fact each EAS event ( ﬀﬁ 5 Hz) is followed by three triggers given by astation in single mode ( ﬀﬂ 2000 Hz), in this way we can measure the spectrum (15000 events) of each stationevery eight hours. This operation allows us to determine, for each run longer than  36 hours, the peak positionOperation, Calibration and Accuracy of the Grande... 315with a precision of  3%. Using a simulation of single muons crossing the detectors we proof that the energydeposit corresponding to the peak of the single particle spectrum is 8.5 MeV.Three stations of the Grande array are located (see fig.1) inside the e/ ﬃ detectors of the KASCADE experimentallowing a check of the previously described calibration method by comparing the energy deposit in a Grandestation with the mean energy deposit of the four e/ ﬃ detectors that are located around it. Only events that havethe core located at about 100 m distance from the Grande station are selected. In this way the KASCADE de-tectors, that are separated by 13 m from each other, are at a distance from the core where the lateral distributionof particles in the EAS is flat and the mean value of their energy deposit can be compared with the Grandestations one.As the Grande and the e/ ﬃ KASCADE detectors are surrounded by different materials and as they do not havethe same thickness, we expect that the energy deposits, even if they are crossed by the same number of particles,are not equal. Figure 4 shows the measured energy deposits in the two detectors (full squares) compared withthose expected by a full shower (CORSIKA) and detector (CRES) simulation (open circles).0501001502002503003504000 10 20 30 40 50 60QADC chnumber of eventsFigure 3. Single particle spectrum measured in station5. The line shows the result of a Landau t.020040060080010000 200 400 600 800 1000KASCADE e/γ detector (MeV/m2)Grande detector (MeV/m2 )Figure 4. Comparison of the energy deposit measured(full squares) and expected from a full simulation (opencircles) in the KASCADE e/  and Grande detectors.We also compare the shower parameters reconstructed, for the same events, by the Grande and by the KAS-CADE e/ ﬃ arrays separately. We select events with the core located inside both arrays and reconstructed byboth of them. This is obtained requiring that: the maximum energy deposit in the Grande detectors is measuredby station 7 (i.e. the center of the Grande trigger cluster located inside the KASCADE array, see fig.1); thecore position, measured by KASCADE, is located inside a circle of 90 m radii centered in the middle of thearray; 0.4  "!$#&%('*),+*-. 1.4 (i.e. events with a good reconstruction) and Log Ne /1032546087:9<; 5.6 (i.e. Grandeefficiency near to one).The distribution of the differences of the x (red solid line) and y (blue dashed line) coordinates of the coreposition are shown in figure 5. It can be seen that the mean value of the differences, on both coordinates,between two arrays is lower than 2 m and that the standard deviation of the distribution is about 12 m. As316 A. Chiavassa et althe errors on the core location for the KASCADE array[4] are, at these energies,  2 m we can say that thiswidth is mainly due to the resolution of the Grande array that can be so evaluated being less than 12 m. Figure6 shows the scatter plot of the shower size measured by the two arrays. This is dominated by the statisticaluncertainties on the Grande reconstruction, that are (in the range 6.0  >=@?BADCFE,/103254&087@9< 6.1) about 25%.Possible systematic uncertainties and their origin are under investigation.0100200300400500-200 -150 -100 -50 0 50 100 150 200Entries     8394∆x=-0.6 m σx=10.8 m∆y=-2.0 m σy=11.9 m∆ core coordinates (m)Number of EventsFigure 5. Distribution of the difference of the coordi-nates of the core position (x solid line and y dashed line)measured by the KASCADE and the Grande arrays.66.256.56.7577.257.57.7586 6.25 6.5 6.75 7 7.25 7.5 7.75 8Log NeKASCADELog Ne GrandeFigure 6. Scatter plot of the shower size measuredby the Grande array vs the one measured by the KAS-CADE array3. ConclusionsThe Grande array is in continuous and stable data taking since January 2004. We have described the procedureused to calibrate the analog signals; comparing the energy deposits in the KASCADE and Grande detectorswith the expectations from a complete shower simulation, we can conclude that the calibrations of the twoarrays are coherent with each other. We have also reported the results of the event reconstruction obtainedindependently with the two arrays, showing that the resolution on the core coordinates of the Grande array isaround 12 m reaching the value foreseen in the experiment proposal.References[1] A. Haungs et al. KASCADE-Grande Collab., Proc of 28 GIH ICRC, Tsukuba (2003) 2, 985.[2] T. Antoni et al. KASCADE Coll., To appear in Astroparticle Physics (2005).[3] M. Aglietta et al. EAS-TOP Coll., Astrop. Phys. 21, 583 (2004).[4] T. Antoni et al KASCADE Coll., Nucl. Instr. and Meth. A 513, 490 (2003).[5] A. Chiavassa et al. KASCADE-Grande Coll., Proc of the 28 GIH ICRC, Tsukuba (2003).

Operation, Calibration and Accuracy of the Grande array of the KASCADE-Grande experiment

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