Calorimetry in space with PAMELA Valter Bonvicini INFN – Trieste On behalf of the PAMELA Collaboration OUTLINE: Scientific goals of PAMELA Overview of the PAMELA instrument 3. The Si-W imaging calorimeter: description and design details 4. Scientific results 5. Conclusions Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

The PAMELA Collaboration Italy: Bari Florence Frascati Trieste Naples Rome CNR, Florence Moscow St. Petersburg Russia: Germany: Siegen Sweden: KTH, Stockholm Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

PAMELA scientific objectives PAMELA design performance (A Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) PAMELA design performance Study antiparticles in cosmic rays Search for antimatter Search for dark matter Study cosmic-ray propagation Study solar physics and solar modulation Study the electron spectrum (local sources?) energy range particles in 3 years Antiprotons 80 MeV - 190 GeV O(104) Positrons 50 MeV - 270 GeV O(105) Electrons up to 500 GeV O(106) Protons up to 700 GeV O(108) Electrons+positrons up to 2 TeV (from calorimeter) Light Nuclei up to 200 GeV/n He/Be/C: O(107/4/5) AntiNuclei search sensitivity of 3x10-8 in He/He Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

Resurs-DK1 satellite + orbit Resurs-DK1: multi-spectral imaging of earth’s surface. PAMELA mounted inside a pressurized container. Launch from Baikonur on June 15th, 2006 at 0800 UTC with a Soyuz-U rocket. As of now, ~ 1013 triggers, > 30 TB of data downloaded. Lifetime extended till end of satellite operations. Data transmitted to NTsOMZ, Moscow, via high-speed radio downlink, ~16 GB per day. Quasi-polar (70.0°) and elliptical orbit (350 km - 610 km) – from 2010 circular orbit (70.0°, 600 km). Traverses the South Atlantic Anomaly. Crosses the outer (electron) Van Allen belt at south pole. PAMELA Resurs-DK1 Mass: 6.7 tonnes Height: 7.4 m Solar array area: 36 m2 350 km 70o SAA 610 km Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013 The PAMELA instrument 21.5 cm2sr Time-of-flight Trigger / Albedo rejection / Particle identification (up to 1 GeV/c) / dE/dx 3 double-layer scintillator paddles Timing resolution: (paddle)  110 ps (ToF)  330 ps (MIPs) Anticoincidence system Rejection of events with particles interacting with the apparatus Plastic scintillator paddles MIP efficiency > 99.9% Si Tracker + magnet Measures rigidity 5 Nd-B-Fe modules (0.43T) 6 planes of double-sided Si microstrip detectors ~3 µm resolution (bending view)  MDR  1.2 TV Mass: 470 kg Power: ~ 360 W Size: 130x70x70 cm3 Si-W Imaging Calorimeter Shower-tail catcher (S4) Plastic scintillator paddle, 1 cm thick Main task: ND trigger Neutron detector 36 3He counters e/h discrimination at high energies Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

The PAMELA Imaging Calorimeter - 1 Main tasks: lepton/hadron discrimination e+/- energy measurement Characteristics: 22 W plates (2.6 mm / 0.74 X0) 44 Si layers (X-Y), 380 µm thick Total depth: 16.3 X0 / 0.6 lI 4224 channels Self-triggering mode option (> 300 GeV; GF~600 cm2 sr) Mass: 110 kg Power Consumption: 48 W Design performance: p,e+ selection efficiency ~ 90% p rejection factor ~ 105 e rejection factor > 104 Energy resolution ~ 3% @ 200 GeV Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

The PAMELA Imaging Calorimeter - 2 44 Si detector views (22X and 22Y) 8x8 cm2 detectors arranged in a 3x3 matrix 32 strips/detector, 2.4 mm pitch Strips of detectors in the same row (column) are bonded together (ladder)  24 cm long strips Each ladder (32 channels) is read out by 2 CR1.4P front-end chips  6 front-end chips/view In total: 396 silicon detectors 264 CR1.4P chips 4224 channels Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

The PAMELA Imaging Calorimeter - 3 Front-end  CR1.4P ASIC (full custom design) Design characteristics: - 16 channels/chip - channel structure: CSA, shaper, T/H, out. mux. - input-selectable calibration circuit - integrated self-trigger circuit - shaping time = 1 µs - sensitivity = 5 mV/MIP - wide dynamic range: 7.1 pC = 1400 MIP (1 MIP = 4.9 fC) - ENC ≈ 2700 e- rms + 5 e- /pF ADC: - 1 16-bit ADC/view  44 ADCs (AD977A) - total calorimeter proc. time ~ 700 µs Readout: - Calorimeter divided into 4 sections: Odd_X, Odd_Y, Even_X, Even_Y - 1 DSP/section (ADSP2187)  4 DSPs on-line calibration data compression - 1 FPGA/section (A54SX72)  4 FPGAs Architecture of one channel of the CR1.4P 1-MIP signal distribution (S/N ~ 10) Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

interacting antiproton (flight data) 84 GeV/c interacting antiproton (flight data) Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013 92 GeV/c positron (flight data) Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013 Flight data: 36 GeV/c interacting proton Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013 Flight data: 32.3 GeV/c positron Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013 Antiproton results Simon et al. (ApJ 499 (1998) 250) Ptuskin et al. (ApJ 642 (2006) 902) Donato et al. (PRL 102 (2009) 071301) O. Adriani et al., PRL 102, 051101 (2009); O. Adriani et al., PRL 105, 121101 (2010) Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

Positron selection with the calorimeter - 1 Rigidity: 20-30 GV e- Events p (non-int) p (int) Events (x 103) p (non-int) e+ p (int) Fraction of charge released along the calorimeter track (left, hit, right) Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

Positron selection with the calorimeter - 2 Rigidity: 20-30 GV e- Events e+ Events p Fraction of charge released along the calorimeter track (left, hit, right) + Energy-momentum match Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

Positron selection with the calorimeter - 3 Rigidity: 20-30 GV e- Events Events e+ p Energy-momentum match Starting point of shower Longitudinal profile Fraction of charge released along the calorimeter track (left, hit, right) + Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

Positron-to-electron fraction - 1 O. Adriani et al., Nature 458 (2009) 607-609. O. Adriani et al, Astropart. Phys. 34 (2010) 1-11. Moskalenko and Strong, Astrophys. J.493, 694-707 (1998) Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

Positron-to-electron fraction - 2 Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013 Summary PAMELA has been in orbit and studying cosmic rays for ~ 7 years. ~ 1013 triggers and > 30 TB of data have been downlinked. The Imaging Calorimeter has been performing nominally throughout this period: basic performance (noise, signal, baseline...) are nominal and stable; science performance (energy resolution, particle id., etc.) are consistent with design specifications; no degradations/failures/functionality loss observed so far; the calorimeter proved to be a key instrument to achieve the scientific results of PAMELA. Antiproton-to-proton flux ratio and antiproton energy spectrum (~100 MeV - 200 GeV) show no significant deviations from secondary production expectations. High energy positron fraction (>10 GeV) increases significantly (and unexpectedly!) with energy (recent confirmation by AMS). Primary source? The proton and helium nuclei spectra have been measured up to 1.2 TV. The observations challenge the current paradigm of cosmic ray acceleration and propagation. Waiting for other AMS results to compare contemporary measurements. Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013 ~ Spare slides ~ Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

Orbital environment and in-flight operation Particle rate: max. at the poles (cutoff <100 MV) min. at the equator (cutoff ~15 GV) Calorimeter operation: Calibration performed every 95 min. (at the ascending node) Data acquisition: - special run after calibration (“full mode”)  ~ 10 kByte/ev. - normal physics runs (“compressed mode”)  ~ 1 kByte/ev. Slow control: Temperatures Detector leakage currents Calibration & supply voltages ~ 25 Hz Calibration @ ascending node Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

Calorimeter in-flight performance - 2 ~24.3 ~24.0 GROUND (muons) FLIGHT (relativistic particles) Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

Calorimeter in-flight performance - 1 January 2008 July 2006 Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

Calorimeter in-flight performance - 2 January 2008 July 2006 Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

H and He absolute fluxes @ high energy 2.85 2.67 232 GV Spectral index 2.77 2.48 243 GV O. Adriani et al., Science 332 (2011) 69 Deviations from single power law (SPL): Spectra gradually soften in the range 30÷230GV Spectral hardening @ R~235GV ~0.2÷0.3 SPL is rejected at 98% CL Origin of the structures? - At the sources: multi-populations, etc.? - Propagation effects? (e.g. P. Blasi et al., Phys.Rev.Lett. 109 (2012) 061101 H He Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

interacting anti-proton Flight data: 11.6 GeV/c interacting anti-proton Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

non-interacting anti-proton Flight data: 18 GeV/c non-interacting anti-proton Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013 Flight data: 14.7 GV Interacting nucleus (Z = 8)‏ Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

calorimeter self-trigger (m.p. electron) Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013 13 GV Interacting He Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

CALO SELF TRIGGER EVENT: 167103 MIP RELEASED 279 MIP in S4 26 Neutrons in ND Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

Charge identification with the Calorimeter Truncated mean of multiple dE/dx measurements in different silicon planes Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013

Energy-momentum match Preliminary e- e+ ‘Electron’ ‘Hadron’ p, d p Valter Bonvicini - CHEF2013, Paris, 22-25 April 2013