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Date: 2014, March 6 @ IHEP

Participants: Deng Jianrong, Feng Zhaoyang, Gou Quanbu, Hu Hongbo, Liu Siqi, Olivier Martineau-Huynh

Topic: status report on the GRAND-proto ground array

** Simulation (Feng Zhaoyang)
The goal here is to perform a precise determination of the ground array detection efficiency for EAS, in order to define a set of parameters (theta, phi, core positions, energy...) for which detection probability is large enough (90%? 95%? 99%?) to ensure that the ground array can be used efficiently as a cross-check of the EAS nature for the candidates selected with the radio array.

Reminder: during our last meeting, Feng Zhaoyang explained how the simulation had to face computation time issues: for energies above 10^17eV, standard CORSIKA simulations last too long given the computation capacities at hand for TREND. Thinning of the showers was a solution studied (but requires de-thinning, a non-standard and delicate process). CONEX-3D, as well as dropping electriomagnetic component of the inclined showers were alternatives discussed.

- Finally Zhaoyang tested an increase of the secondary particle threshold (ie the energy below which you don't track particles anymore in the simulation) from 1MeV to 5MeV. This resulted in a dramatic gain in CPU time (factor of several units, exact value depending on machine), therefore allowing to run simulations up to 10^18eV without thinning in a realistic time (typically 1 shower/day/CPU). Given our energy range (E>10^16.5eV), it is also expected that this modification will not affect the simulation results [to be checked?]

- The HXMT group accepts to let us use their CPUs for our simulation when they are free. HongBo has bought a 20TBy disks that can be used to store our simulations outputs. It is expected that 3000 showers will be generated in a month with following parameters: energies in 10^17 - 10^18eV, phi in +-20° around North, theta between 40 and 70°. Then the showers wil be translated above ground (~ 100 core positions/shower), yielding a set of 3.10^5 EAS covering the full parameter space relevant for GRAND-proto.

- Simulation of the detector's response will be carried out with the package developped for As-Gamma by Feng Zhaoyang and Guo Yiqing. Outputs of this simulation have been compared to experimental values with the AsGamma data. The match is excellent in the experiment's energy range (E<100TeV). It could however be interesting to break this analysis in energy bins, in order to confirm that there is no negative evolution of this agreement with energy. This would indeed proove critical here, as the GRAND-proto energy range is 100 to1000 times larger as that of AsGamma. Detector's parameters (size, thickness, PMT response) will be adapted to our experimental values as soon as available. Time duration of the simulation of the detector's response is negligible.

** Hardware
Prototypes of the detectors are being built and studied at IHEP & Tibet University. It is agreed that all efforts wil be made to make sure that a subset of 9 detectors can be deployed in Ulastai this summer for the following reasons:
- our timescale is very short and we need to demonstrate concrete progress and results in the GRAND-proto project within the next 1.5 year.
- Outside work in Ulastai is much harder in Autumn and Winter (shorter days, colder temperatures and hard ground).
- Olivier has teaching duties between September and December and is unelikelly to be able to come to China at that time of the year.
A DAQ chain similar as the one used for the 3-scintillator array will be used for this prototype array.

** Update (on 14/03/2014):
During our mission in Ulastai these last days together with Zhao Meng, Gu Junhua and Zhang Jianli, 5 antennas (12 working channels) could be deployed. We realized then that our initial goal to deploy an array of 15 antennas (using the TREND-50 DAQ system) + 9 scintillators this summer may not be adapted.

Deploying and maintening a system of 45 (radio) + 9 (scints) analog channels over an area of 2500mx600m would require a very important effort. It woud also imply to dismentle the present TREND-50 array.

On the other hand, the chances to perform & maintain a reliable calibration of the radio signal amplitude (a critical element for the determination of the radio signal polarization) are questionnable with an analog DAQ system.

Finaly, we expect the final (digital) DAQ system to be deployed over 35 radio units in summer 2015.

For all these reasons, it appears that cost certainly outweight benefits and this plan may therefore not be worth. An alternative could be to postpone the "physics" array tothe full array (to be deployed in summer 2015), and in the meanwhile, work with an engeneering array only, composed of 6-7 antennas + 4-6 scintillators over a reduced area (800mx400m). No polarization measurment would be performed, but this system would allow to test the material and develop the DAQ and reconstruction code both for the radio and ground arrays. It would also be used as a testbench for the digital DAQ system for the radio array.


simulation status: Presentation by Feng Zhaoyang.

-- OlivierMartineauHuynh - 2014-03-17

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Topic revision: r2 - 2014-03-18 - OlivierMartineauHuynh
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