ARGO-YBJ: Italy (INFN) - China (CAS) collaboration

Collaboration:

- Italy: INFN and Dipartimento di Fisica dell'Universita', Lecce; INFN and Dipartimento di Fisica dell'Universita', Napoli; INFN and Dipartimento di Fisica dell'Universita' "Tor Vergata", Roma; INFN and Dipartimento di Fisica dell'Universita' "Roma Tre", Roma; INFN and Istituto di Cosmogeofisica del CNR, Torino; INFN, Sezione di Catania and IFCAI/CNR Palermo; INFN, Sezione di Pavia
- China: IHEP, Beijing; Hong Kong University, Hong Kong; Shandong University, JiNan; South West Jiaotong University, Chengdu; Tibet University, Lhasa; Yunnan University, Kunming; Zhenghou University, Henan

Location: Yangbajing Cosmic Ray Laboratory, 4300 m a.s.l., Tibet (China)

1. Goal of the experiment

The ARGO-YBJ experiment is devoted to the search of cosmic ray sources by means of the observation of galactic and extragalactic neutral and charged radiation in the energy range 100 GeV - 1000 TeV with a detector based on Resistive Plate Chambers (RPC's) covering an area of 6500 m2 and providing a detailed space-time picture of the cosmic ray shower front. The detector is under construction at the Yangbajing Cosmic Ray Laboratory.

More on the experiment...

2.

Activities during the 2002

- Completion of the gas distribution network at YBJ.
- Installation of the Central Station including part of the DAQ system.
- Construction of 51 Local Stations (for a total of 71 LS), 36 of them installed and put in operation at YBJ.
- Installation of 20 clusters.
- Study for the optimization of the RPCs working point (gas, HV, and front-end threshold
- 36 clusters connected to the electronics and 16 of them put in data taking for debugging runs.
- Test of the DCS system prototype
- Test of the 'scaler mode' acquisition system.

The following achievements have been obtained:

• Construction of 457 RPCs (76%) Comment: the assembling line at the provider has been stopped for about 3 months to solve technical problems related to the bakelite sheets.

• Installation of 40 Clusters (67%). Comment: about 10% of the RPCs shipped to Yangbajing broke down on the way. All the other chambers,successfully tested, have been installed.

• 36 Clusters connected to the electronics but only 16 of them put in data taking (32%). Comment: we had some DAQ problems which prevented us from increasing the trigger rate.

Milestones 2003

Construction of 600 RPCs | 31-12-2003
100 clusters installed by the end of 2003 | 31-12-2003
50 clusters in operation with electronics | 31-12-2003
36 clusters in data taking for physics run | 31-12-2002

3. INFN contribution to the experiment in terms of manpower and financial support

Manpower:

54 researchers (37 FTE), 4 technologists (2 FTE), 8 technicians (4.5 FTE) plus support from the mechanics and electronics workshops of Napoli and Roma-2.

Budget for the Year 2003: 4.1% of the CSNII total budget

4. Publications in refereed journal: 2
5. Conference talks: 1

6. Number of undergraduate and doctoral thesis on the experiment:

- n. 1 Ph.D.;
- n. 3 Laurea diplomas.

7. Leadership roles and primary responsibilities in the experiment

- Spokesperson (Italian side) B. D'Ettorre Piazzoli [Napoli University]
- Main commitments

> Lecce: Local Station electronics and trigger.

> Napoli: DAQ, gas distribution system, analog read-out, trigger.

> Roma-2: Front-End electronics, detector control system

> Roma-3: Detector assembling, experiment layout, HV system, trigger distribution.

8. Innovative instruments

The ARGO-YBJ experiment has developed

- a solid large area RPC detector [280x125 cm2, active area ~ 98 % ] with both digital (linearity up to ~ 10 p/m2) and analog (up to 104 p/m2) read-out, 1.3 ns time resolution (measured at YangBaJing Laboratory), current read-out for control of the detector operation
- electronics to handle the RPCs signal (custom design)
- DAQ system with 10 MB/s capability

Many of the technical solutions could be of general interest for experiments aiming to fully exploit the RPCs performance

9. Competing experiments

A similar approach to the g -astronomy ("full coverage" detector at high altitude, large field of view, ~ 100 % duty cycle) is already operating (MILAGRO (USA), 2600 m a.s.l., 4800 m2 water pool instrumented with PM tubes + array). The performance of ARGO-YBJ is expected to be definitely better, due to the high space-time granularity as well as to the higher elevation of the experimental site. However, a fast completion and commissioning of the detector is needed.

10. International committee which has reviewed the experiment

The ARGO-YBJ project has been examined and approved by the INFN Committee II and by the CAS Scientific Committee.