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A ground array for the TREND-inclined test array

NSFC proposal

TREND meeting, IHEP, February 26, 2013

* Participants: Feng ZhaoYang, Gou QuanBu, Guo Yiqing, Hu HongBo, Olivier Martineau-Huynh, Zhang Yi.

* Purpose: The aim of this meeting is to discuss a proposal to NSFC for a ground array to be installed
on the TREND site, to be used as a cross-check for EAS detection.

Framework presentation:

*OMH first introduces the framework of the project:
- The ultimate goal of TREND is building a Giant Radio Array for Neutrino detection (GRAND).
Tau neutrinos of ultra high energy (E>10^17eV) from cosmic origin could be detected if they
interact in the Earth rock, and if the produce tau lepton emerges in the atmosphere, decays and
induces a shower with sufficient energy (E>10^16eV) to be detected by radio antenna.
A MC study of the sensitivity to neutrinos by a giant array has been initiated a while ago already,
and is now close to complition:
neutrino trajectory definition, neutrino interaction, tau energy loss and decay are
already included in the simulation. Simulation code for shower generation, radio signal simulation and antenna response have been developed and tested; They are now being included in the simulation chain to produce an end-to-end simulation study.
Even if this last part is not completed yet, it is already possible to estimate the sensitivity of the giant array through some basic selections.
In this preliminary study, we consider an array of 250'000 antennas deployed over a 200x200km? area over the Tianshan mountains (square grid wih 400m side).
A shower is said to be detected if :
- its energy > 10^17eV.
- At least 5 antennas are in direct view of the decay point and in a 5° cone from it.
We check which of the >30'000 showers simulated so far pass these suts and derive from this a limit on the GRAND sensitivity to cosmic neutrinos, assuming that 0 events are detected.
This limit is ~1000 x beter than the present best (AUGER), and ~10x better than the best limit for future project (ARIANA).

2 key points in the project:
1- technical: how to deploy such a large array?
2- physical: how to get 0 candidate (ie reject all backround)?

For the 1st point, there is no definitive answer yet. But specialists of the domain (for example Pascal Lautridou, founder of CODALEMA and member of TREND) suggest that we shoudl investigate on teh possibility to register 1 info only (amplitude at a given time). This would dramaticly simplify the issues and reduce costs down to one to few 100$ / unit.
The TREND-inclined prototype array would be a perfect test bench to study this issue.

For the 2nd point, the main concern is background of human origin.
The idea here is to use the fact that EAS radio signal is linearly polarized( at 1st order in a direction perpandicular both to shower direction and geomagnetic field), while background is random.

We propose to develop a prototype called TREND-inclined which would measure signal polarisation for detected signals. Only signals with polar compatible to what is expected for EAS would be selected.
The prototype is composed of 40 antennas deployed along teh North-South baseline of the 21CMA.
It would measure both vertical and East-West polarization.
It is designed to detect showers developing in the North-South axis,and would focus on inclined showers, as only them are of interest for neutrinos studies.
A ground array of scintillators xould be used to cross check offline if selected candidates are indeed EAS.

* Simulation results

* Guo Yiqing then presents the resulst of the simulation he performed for the ground array.
The layout proposed intially is composed of 21 units, arranged in 3 columns of 7 detectors with 300m spacing in teh East-West axis and ~600m in the NS (OK because we focus on showers with theta>45°). Each unit is a 1m? scintillator.
It is shown that a tilt of the scintillators from their standard horizontal position results in a significant increase in the EAS event rate (roughly a factor 10 above 65° for a tilt of 50 to 70°), with ~1 evt/day over the whole array for zen>65°.
Installing 35 detectors with 2 additionnal rows at -150m & +150m (?) induces an aditionnal gain of 3-4 in event rate.

* Discussion:

Given the (limited) budget, it seems possible to request funding for 21 detectors with 0.5m?.
20kRMB should be OK for detector+PMT.HV+electronics.
Signal would be transfered to DAQ through the optical fibers (already deployed). Computers from TREND present setup could be used.

* Guidelines for the application:

* Introduction
I believe it is important to place the proposal in the complete perspective of the project, ie:
1- simulations show that a giant radio array would be a very comptetitive setup for cosmic neutrino astronomy,
the next frontier of Astroparticles Physics.
2 - The key issue for this project would be background rejection, and in particular the (very dominant) background of human origin.
3- We think polarization measurment would allow to tag very efficiently the EAS and reject the background.
4- Only way to check this hypothesis is to build a prototype setup: TREND-inclined. The radio array would be composed of 30 antennas with polarization measurment installed on the present TREND site. It would be to small for neutrino detection, and would only detect EAS showers from "standard" origin. But it is OK because the radio properties of standard and neutrino-induced EAS are the same. The setup is already partly funded (only the electronics is missing). It benefits from the expertise from pionners of the technique (Antennas are from CODALEMA-AUGER)
5- In order to evaluate quantitatively the rejection power of the radio array, we need an independent check of the nature of the candidates selected. This is possible only if we deploy a ground array of scintillators, which is the purpose of this proposal.e

* The great expertise of IHEP for ground array & scintillator technique should be stressed.

* Yiqin's simulation results shouldbe used to show that a serious design study was performed for this proposal.

* About the remarks of the last year's reviewers:
1- Why using radio for CR physics?
I copy here what I wrote in the document TRENDProposal_Janu2013 about this issue:

Properties of high energy cosmic rays can only be measured indirectly, through the detection of the EAS generated by the primary particles in the high atmosphere. Particle interactions at these very high energies are characterized by large uncertainties and systematic biases therefore affect the estimation of the initial parameters of the cosmic rays. The most efficient solution to deal with this issue is to perform EAS detection by several different means. Being affected by different systematic effects, the combination of these different techniques is a powerful way to tackle down biases and improve our understanding of shower development.

Besides, the radio technique for the detection of EAS with radio antennas has accomplished remarkable progresses in the ten last years (understanding and modeling of the radio emission by EAS particles, measurement of the energy, autonomous detection, …), and the technique has characteristics well adapted to deployment over giant surafces (in particular low price, easiness of deployment and calibration) .

These two elements have generated strong interest for the radio technique among the cosmic rays community. Many leading groups in the field of cosmic rays have started R&D work on radio detection at MHz or GHz frequency range (Karlsruhe and Amsterdam with LOPES and AERA, Paris with EASIER and AERA, Nantes with CODALEMA and AREA, Chicago with MIDAS…).

It is not exaggerated to say that developing radio activities in a Cosmic Ray Physics group has become a standard procedure, while making the opposite choice is taking the risk of not being able to handle a technique which may play a major role in the next decade.
2- Radio & PMTs
If what the referee ment was that PMTs may generate electromagnetic waves that could trig the antennas, teh answer is very simple:
an array of 3 scintillator was deployed in 2010 on the site of the present TREND prototype and ran for most of teh last 3 years. The PMTs were carrefully shielded in a thick & air-tight metal cylinder. No rise in the radio trigger rate was observed when teh ground array was on. Reconstructiuon of teh direction of origin of teh detected signal did not point to the scintillators.

-- OlivierMartineauHuynh - 2013-03-02

Topic attachments
I Attachment History Action Size Date Who Comment
PDFpdf TRENDmeeting_26022012.pdf r1 manage 740.8 K 2013-03-02 - 10:44 OlivierMartineauHuynh Framework presentation (OMH)
PDFpdf inclined_groundarraysimulation.pdf r1 manage 144.5 K 2013-03-02 - 10:45 OlivierMartineauHuynh Simulation results (Guo Yiqing)
Topic revision: r1 - 2013-03-02 - OlivierMartineauHuynh
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