The magnetic spectrometer of the PAMELA satellite experiment

The magnetic spectrometer of the PAMELA satellite experiment § § INTRODUCTION DESCRIPTION OF THE MAGNETIC SPECTROMETER § Silicon Sensors § Mechanics § Electronics TESTS RESULTS CONCLUSIONS Oscar Adriani INFN Sezione di Firenze / Dipartimento di Fisica dell’Universita’ di Firenze The PAMELA collaboration

The PAMELA experiment • • Antiproton flux Positron charge ratio MAIN TOPICS: fluxes measurement Search for light Antinuclei SECONDARY TOPICS: • • Modulation of GCR’s in the Heliosphere Solar Energetic Particles (SEP) Earth Magnetosphere … spectra e+ spectra Kailua-Kona (Hawaii) 80 Me. V/c … 190 Ge. V/c 50 Me. V/c … 270 Ge. V/c 5 November 2002 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

Expected Fluxes in 3 Years Particle Number (3 yrs) Energy Range Protons 3. 108 80 Me. V – 700 Ge. V Antiprotons >3. 104 80 Me. V – 190 Ge. V Electrons 6. 106 50 Me. V – 2 Te. V Positrons >3. 105 50 Me. V – 270 Ge. V He 4. 107 80 Me. V/n – 700 Ge. V/n Be 4. 104 80 Me. V/n – 700 Ge. V/n C 4. 105 80 Me. V/n – 700 Ge. V/n Antihelium Limit 7. 10 -8 80 Me. V/n – 30 Ge. V/n • ‘Semi-Polar’ orbit (700) Low energy particles • Wide energy range + 3 years mission Reliable measurements Kailua-Kona (Hawaii) 5 November 2002 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

Satellite and Orbit Resurs DK 1 § Earth observation role § 350 / 610 km § Inclination = 70 o § Soyuz 2 launcher § Baikonur launch site Pamela operational During launch / orbital manoeuvres § Launch date = mid 2003 § 3 year mission § Housed in an atmospheric pressure vessel § Temperature = 5 o. C ® 35 o. C § All subsystems must withstand launch vibrations! § Electronics must withstand up to ~3 krad 350 - 600 km Kailua-Kona (Hawaii) 5 November 2002 §Total mass = 380 kg / 345 W power budget § Dedicated telemetry down-link (4 Gbyte per day) 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

Principle of Operation Trigger+velocity g measurement TOP AC (CAT) SIDE AC (CAS) p measurement E measurement+ Particle id. BOTTOM SCINTILLATOR (S 4) Kailua-Kona (Hawaii) 5 November 2002 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

Pamela Subdetectors TRD Anticoincidence system • Threshold device. Signal from e±, no signal from p, p • Defines acceptance for tracker • 9 planes of Xe/Co 2 filled straws (4 mm diameter). Interspersed with carbon fibre radiators crude tracking. • Plastic scintillator + PMT 1. 2 m • Aim: factor 20 rejection e/p (above 1 Ge. V/c) (2. 105 with calorimeter) • Trigger / detects albedos / particle identification (up to 1 Ge. V/c) / d. E/dx • Plastic scintillator + PMT Si Tracker + magnet • Timing resolution = 120 ps • Measures rigidity Si-W Calorimeter • 5 Nd-B-Fe magnet segments (0. 4 T) • Measures energies of e±. DE/E = 15% / E 1/2 + 5% • 6 planes of 300 mm thick Si detectors • ~3 mm resolution in bending view demonstrated, ie: MDR = 740 GV/c • +/-10 MIP dynamic range Kailua-Kona (Hawaii) Time-of-flight • Si-X Mass ~450 kg Acceptance ~20. 5 cm 2 sr 5 November 2002 / W / Si-Y structure. • 22 Si / 21 W 16 X 0 / 0. 9 l 0 • Imaging: EM - vs- hadronic discrimination, longitudinal and transverse shower profile 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

The PAMELA Magnetic Spectrometer • Magnetic System – It produces an intense magnetic field region where charged particles follow curved trajectories • Tracking System – It allows to determine six points in the high field region to reconstruct the particle trajectory and so its momentum and charge sign • • e+ B Kailua-Kona (Hawaii) 5 November 2002 Momentum p = m g v Charge sign (e+/e-) (p/p) Ø If B uniform and perpendicular to p, then 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

A glossary of magnetic spectrometers for cosmic rays studies • • • Momentum Rigidity Deflection • DR/R = Dh/h = R Dh (Dh = constant point’s measurement error) p = q. Br (r=radius of curvature) R = p/q = Br h = 1/R = q/p spatial resolution • Maximum Detectable Rigidity (MDR) : e+ B Kailua-Kona (Hawaii) 5 November 2002 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

The PAMELA Magnetic Spectrometer MAGNETIC SYSTEM • 5 magnetic modules • permanent magnet assembled in an aluminum mechanics Permanent magnet elements Geometry of a magnetic block The “Magnetic Tower” Tower – Nd-Fe-B alloy • magnetic cavity sizes: • field inside the cavity: • places for detector planes and electronics boards lodging • Geometric Factor: 20. 5 cm 2 sr • Black IR absorbing painting (not shown in the picture!) – (132 x 162) mm 2 x 445 mm – 0. 48 T at the center Kailua-Kona (Hawaii) 5 November 2002 Base Plate Aluminum prototype frame 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

The PAMELA Magnetic System Magnetic field measurement • Gaussmeter F. W. Bell equipped with 3 -axis probe mounted on a motorized positioning device (0. 1 mm precision) • Measurement of the three components in 67367 points 5 mm apart from each other • Average field along the central axis of the magnetic cavity: 0. 43 T • Good uniformity ! Kailua-Kona (Hawaii) 5 November 2002 Main field component along the cavity axis Main field component for z=0 (II) Main field component for z=0 (I) 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

The PAMELA Tracking System The “ladder” The detector planes The TRACKER The silicon sensor • 6 detector planes • each plane: “ladders” • the “ladder”: 2 microstrip silicon sensors + 1 hybrid circuit with front-end electronics (VA 1 chip) • silicon sensors: double sided; double metalization; integrated decoupling capacitance • resolutions: • MDR > 740 (GV/c) Kailua-Kona (Hawaii) composed 5 November 2002 by 3 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

• • SILICON SENSORS Double Sided (x & y view) Double Metal (No Kapton Fanout) AC Coupled (No external chips) Produced by Hamamatsu Geometrical Dimensions Thickness Leakage Current Decoupling Capacitance Total Defects 70. 0 x 53. 3 mm 2 300 mm < 3 m. A > 20 p. F/cm < 2% Implant Pitch Readout Pitch Biasing Resistance (FOXFET) Interstrip Capacitance 25 mm 50 mm > 50 MW < 10 p. F Implant Pitch Readout Pitch Biasing Resistance (Poly. Silicon) Interstrip Capacitance 67 mm 50 mm > 10 MW < 20 p. F p side n side Kailua-Kona (Hawaii) 5 November 2002 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

SILICON SENSOR’S DEFECTS Request to Hamamatsu: Defects < 2% Defects: Short Circuit of AC coupling (Most common, not destructive) Short between adjacent strips Open circuit on metal lines It seems to be ‘perfect’… BUT The first batch was OK (Prototype ladders were ‘perfect’, bad strip < 2%) We started the mass production… Huge number of bad strips (>10%)!!!!! After a big ‘fight’ we discovered in many sensors short circuits between adjacent strips at the level of implantation (p side). Hamamatsu replaced all the bad sensors (few months of delay) Kailua-Kona (Hawaii) 5 November 2002 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

Implanted strip Kailua-Kona (Hawaii) Implanted strip 5 November 2002 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

The mechanical assembly Requirements: • • • 1 plane made by 3 ladders no material above/below the plane (1 plane = 0. 3% X 0!!!) survive to the launch phase (7. 4 grms, 50 g shocks!!!) good alignment precision thermal stresses (5 -35 0 C) Solution: carbon fibers stiffeners glued laterally to the sensors • very high Young module carbon fiber (300 Gpa) • pultrusion technology Elastic + Rigid gluing A very thin (2. 5 mm) Mylar foil is glued on the plane to increase the safety of the whole spectrometer during integration and flight phases No coating on the bonding Kailua-Kona (Hawaii) 5 November 2002 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

The first detector plane Kailua-Kona (Hawaii) 5 November 2002 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

Kailua-Kona (Hawaii) 5 November 2002 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

Siliconic glue Kailua-Kona (Hawaii) 5 November 2002 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

Vibrations tests in Galileo (Florence) First resonance frequency: 340 Hz!!!! Test plane survived to +6 db spectrum (10. 4 g rms) and repeated 50 g/5 ms + 40 g/1 ms shocks Kailua-Kona (Hawaii) 5 November 2002 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

The test plane electronics lodging on the magnetic system Kailua-Kona (Hawaii) 5 November 2002 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

Few words on the electronics…. (a dedicated talk will be necessary!) Requirements: Solutions: • Very small power consumption • (60 W all included for 36864 readout channels) • Very low noise (3 mm resolution required!!!!) • VA 1 chips (ENC = 185 e- + 7. 5 e-*C(p. F)) Small input Capacitance (<20 p. F) Decoupling between front-end and read-out • Redundancy and safety (satellite experiment) • Big modularity, hot/cold critical parts • Protection against highly ionizing cosmic rays (Mainly Single Event Effect tests) • Selection of components (dedicated tests) Limiting circuits on the power lines Architectural `tricks’ (error correction codes, majority logic etc. ) • Very big data reduction (4 GB/day of telemetry, 5 Hz trigger rate, 30 GB/day of data, >90% reduction is mandatory) • 12 dedicated DSP (ADSP 2187) with highly efficient compression alghoritm Kailua-Kona (Hawaii) 5 November 2002 CMOS low power analog and digital electronics 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

ZOP compression algorithm No Zero Suppression (Losses of particles in case of bad strips or change in the pedestals!!!) We use a reversible alghoritm (Zero Order Predictor, ZOP) Deventstrip = ADC eventstrip - PEDstrip - CNevent Deventstrip is distributed around 0 First word is transmitted Following word is transmitted if above/below n s. . A word is transmitted with the corresponding address if the preceding one was not transmitted If a cluster is identified (Deventstrip > N s) +/- 2 strips are transmitted Kailua-Kona (Hawaii) 5 November 2002 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

The magnetic spectrometer during the last beam test at CERN (July 2002) Kailua-Kona (Hawaii) 5 November 2002 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

July 2000: CERN SPS Spatial resolution h. DISTRIBUTION Dp/p versus p (July 2000 beam test with 5 ladder prototype MS) • FINAL LADDERS • FINAL ELECTRONICS • SMALLER MAGNETIC SYSTEM Kailua-Kona (Hawaii) 5 November 2002 h=1/R=q/p 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

2002: production of flight model detector planes Performances obtained with cosmic rays in Firenze : s/n for MIP Kailua-Kona (Hawaii) 5 November 2002 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

July 2002: CERN SPS During the last test (June 2002) the spectrometer flight model has been tested to determine the performances Kailua-Kona (Hawaii) 5 November 2002 300 Ge. V /c Electron event Signal/Noise Signal nons/n bending 26 view bending s/n 52 view 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

Some results on the compression… Compression time<1 ms factor>96% • Decompressed data o Non compressed data First Plane Signal/Noise • Decompressed data o Non compressed data Last Plane Resolution Dx (mm) Kailua-Kona (Hawaii) 5 November 2002 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani

CONCLUSIONS • The PAMELA magnetic spectrometer is now ready for the final assembly phase • The tracking capabilities have been accurately studied in several beam tests at CERN PS and SPS since 1998 – (s/n)x 52 , (s/n)y 26 for MIP – spatial resolution : – MDR > 740 (GV/c) • The whole detector will be assembled starting from next week in the laboratory of Roma Tor Vergata Kailua-Kona (Hawaii) 5 November 2002 11 th International Workshop on Vertex Detector – Vertex 2002 Oscar Adriani