The AMIGA detector of the Pierre Auger Observatory: an overview Federico Sánchez 1 for the Pierre Auger Collaboration 2 1 Instituto de Tecnologías en Detección y Astropartículas (CNEA-CONICET-UNSAM), Buenos Aires, Argentina 2 Observatorio Pierre Auger, Av.San Martín Norte 34, (5613) Malargüe, Argentina (author list: http://www.auger.org/archive/authors_211_8.html) 32 nd ICRC (Beijing 211) AMIGA Overview The Pierre Auger Coll. 1 / 12
The Pierre Auger Observatory Goals Malargüe, Mendoza Argentina 35 27 48.2 S 69 35 5.31 W Designed to measure: Energy Spectrum Arrival Directions Composition of cosmic rays from 3 1 18 ev (1 18 ev in hybrid mode). In 28 the Pierre Auger Collaboration completed the Observatory baseline design and started the low energy enhancements: AMIGA (SD extension) HEAT (FD extension) see H.J.Mathes s talk, this conference (HE.1.4,#761) Study the energy region where the transition from galactic to extragalactic may occur (1 17 ev 1 19 ev) 32 nd ICRC (Beijing 211) AMIGA Overview The Pierre Auger Coll. 2 / 12
The Pierre Auger Observatory Detectors Main Observatory: 3km 2,16 surface detectors on 1.5 km triangular grid, 24 fluorescence telescopes with 3 3 FoV at 4 peripherical sites 614 613 612 AMIGA + HEAT AMIGA+HEAT: 23.5km 2,42 extra SDs on 75m grid (infill array) associated with 3m 2 buried scintillators, 3 extra FD telescopes tilted upwards 3 15 m Array 75 m Array, 42/42 deployed Muon Detectors, 35m 2 /(21+162)m 2 Northing (km) 611 61 69 68 67 66 Infill area Main array FD Buildings 44 45 46 47 48 49 5 51 Easting (km) 32 nd ICRC (Beijing 211) AMIGA Overview The Pierre Auger Coll. 3 / 12
The AMIGA Concept: Infill + Muon Counters SD station + 3 m2 buried scintillators 64 polystyrene strips (1%PPO+.3%POPOP) Each strip has TiO2 coating + WLS fiber glued Central Hamamatsu H884 64-anode PMT 4 cm PMT + FE electronics Two trigger modes of operation: Ethr µ 1 GeV external Trigger from the SD associated station internal manyfold strip coincidence. see B. Wundheiler s paper, this conference (HE.1.4, #341) 32nd ICRC (Beijing 211) 1 cm 3 1 m2 +1 5 m2 deployed SD trigger 54 g cm 2 AMIGA Overview The Pierre Auger Coll. 4 / 12
Surface Infill SDs identical to (and embedded in) the main array: a. Aperture c. Geometry Rec. e. Energy Estimator b. Event Sel. d. Lat. Dist. Func. f. Energy Calibration benefit from regular Auger array algorithms (see I. Maris s paper, this conference, HE.1.2,#711) 3ToT Efficiency 1.8.6.4.2 p infill array Fe infill array Infill p regular array Regular Example: Trigger Efficiency from simulations using Lat. Trig. Prob. param. Fe regular array 17 17.5 18 18.5 19 log (E/eV) The 75m spacing of the infill allows cosmic rays to be detected down to an energy of 3 1 17 ev with full efficiency. 32 nd ICRC (Beijing 211) AMIGA Overview The Pierre Auger Coll. 5 / 12 1
Surface Infill S(r) (VEM) S(r) (VEM) 1 1 1 1 1 1 Lateral Distribution function S(r) Triggered stations 1 2 4 6 8 1 12 14 16 18 1 1 r (m) θ=(27.2±.2) S(45)=276.6±11.4 Main array Rec. θ=(27.5±.6) S(1)=2.6±2.5 Lateral Distribution function S(r) Triggered stations non-triggered stations Infill array Rec. 1 2 4 6 8 1 12 14 16 18 r (m) Well contained (T5) events from 8/28 (3 hex.) to 12/21 (16 hex.) rate 28 T5/day/hexagon 1 9 8 7 6 5 4 3 2 S(1) S(45) S 38 S 35 Uncertainties Ang.Res. < 1.3 from data: Exposure 26km 2 sryr σ S35 22% see I. Maris s paper (HE.1.2,#711) 1 Number of T5 Events 32 nd ICRC (Beijing 211) AMIGA Overview The Pierre Auger Coll. 6 / 12
The Muon Detector Trigger by an Infill Station lowest level SD trigger 1 Hz Strip signal examples @ PMT level: SD trigger but no part. in MD 99% of cases PMT output current (ma) -.5-1 -1.5 Scintillator strip with no signal trigger -2-2.5 SD trigger opens 9.6µs MD window 1 2 3 4 5 6 7 8 Time (ns) Real Muon Pulse SD trigger and part. in MD trigger PMT output current (ma) -.5-1 -1.5-2 -2.5 Muon signal 1 2 3 4 5 6 7 8 Time (ns) 32 nd ICRC (Beijing 211) AMIGA Overview The Pierre Auger Coll. 7 / 12
The Muon Detector Trigger by an Infill Station lowest level SD trigger 1 Hz SD trigger but no part. in MD 99% of cases trigger SD trigger opens 9.6µs MD window 2 3 4 5 6 7 8 9 the PMT signal is sampled at 8 MHz Time (ns) Collection of 1s and s only logical 1s or s are stored that constitutes 1/64 of an MD event SD trigger and part. in MD trigger Strip signal examples @ Digital level: front-end output voltage (mv) front-end output voltage (mv) 1 8 6 4 2 1 8 6 4 2 Only logical s samples in all strips (void events, 99%) discriminator output FPGA digital samples outcoming pulse discrimination level 2 3 4 5 6 7 8 9 Time (ns) 32 nd ICRC (Beijing 211) AMIGA Overview The Pierre Auger Coll. 7 / 12 3 25 2 15 1 5 3 25 2 15 1 5 discriminator output voltage (mv) discriminator output voltage (mv)
The Muon Detector Trigger by an Infill Station Strip Number Strip Number 6 5 4 3 2 1 6 5 4 3 2 1 1s 1 2 3 4 5 6 7 SD trigger delay Typical low multiplicity event 95% of non-void events 9.6µs time window t / 12.5 ns Unusual high multiplicity event (under investigation) 1 2 3 4 5 6 7 t / 12.5 ns # of Samples Distrib. of 1s over time window shows SD trigger-md events correlation 18 16 14 12 1 8 6 4 2 MD data SD trigger delay σ 3ns 18 16 14 12 1 8 6 4 2 17 175 18 185 19 1 2 3 4 5 6 7 t / 12.5 ns 1% of the SD triggers have data in the MD. The rate of these events is 1.6Hz. In 95% of the cases fewer than 4 strips were struck. Strategies over 1s dist. to count muons B. Wundheiler s paper (HE.1.4,#341) 32 nd ICRC (Beijing 211) AMIGA Overview The Pierre Auger Coll. 8 / 12
Summary & Conclusions The AMIGA low energy enhancement of the Pierre Auger Observatory is being built (fully efficient from 3 1 17 ev). Present: the 75m infill array has been completed and 43/61 SDs (7%) are fully operative (the remaining by the end of 211). infill events recorded at a rate of 28 T5/day/hexagon ( 3 regular array rate) and analysis is on-going. 35m 2 /21m 2 scintillators for prototyping phase (to be completed by 212) have been installed (183m 2 needed for full infill array) Future: deployment of SD stations with smaller spacing (possibly 24 SDs on 433m array over 5.9km 2 ). Thank you! 谢谢! 32 nd ICRC (Beijing 211) AMIGA Overview The Pierre Auger Coll. 9 / 12
Backup 32 nd ICRC (Beijing 211) AMIGA Overview The Pierre Auger Coll. 1 / 12
MD Calibration in the Lab. 18 16 32 channel calibration in Lab 14 12 # SPE 1 8 6 4 2 5 1 15 2 25 3 35 4 45 5 Distance along fiber from PMT (cm) 32 nd ICRC (Beijing 211) AMIGA Overview The Pierre Auger Coll. 11 / 12
Counting strategies counted / impinging muons 1.4 1.2 1.8.6.4.2 ~3% <V spe > level Main Pixel Neighbor Pixels 1G3ns 1Q3ns 1C3ns 1G3ns 1Q3ns 1C3ns -.2 6 8 1 12 14 16 18 2 22 discrimination threshold (mv) 32 nd ICRC (Beijing 211) AMIGA Overview The Pierre Auger Coll. 12 / 12