hardware implementation of data compression ... - INFN Bologna

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2 The ALICE experiment Figure 1.1: Longitudinal section of the ALICE detector single-arm detectors: an electromagnetic calorimeter (Photon Spectrometer, PHOS) and an array of RICH counters optimized for high-momentum inclusive particle identification (HMPID). My thesis work has been focused on data coming from one of the three detectors forming the ITS, the Silicon Drift Detector (SDD). 1.1 The Inner Tracking System The basic functions of the ITS [4] are: • determination of the primary vertex and of the secondary vertices necessary for the reconstruction of charm and hyperon decays; • particle identification and tracking of low-momentum particles; • improvement of the momentum and angle measurements of the TPC.
1.1 — The Inner Tracking System 1.1.1 Tracking in ALICE Track finding in heavy-ion collisions at the LHC presents a big challenge, because of the extremely high track density. In order to achieve a high granularity and a good two-track separation, ALICE uses threedimensional hit information, wherever feasible, with many points on each track and a weak magnetic field. The ionization density of each track is measured for particle identification. The need for a large number of points on each track has led to the choice of a TPC as the main tracking system. In spite of its drawbacks, concerning speed and data volume, only this device can provide reliable performance for a large volume at up to 8000 charged particles per unit of rapidity. The minimum possible inner radius of the TPC (rin =90cm)isgivenbythe maximum acceptable hit density. The outer radius (rout = 250 cm) is determined by the minimum length required for a dE/dx resolution better than 10 %. At smaller radii, and hence larger track densities, tracking is taken over by the ITS. The ITS consists of six cylindrical layers of silicon detectors. The number and position of the layers are optimized for efficient track finding and impact parameter resolution. In particular, the outer radius is determined by the track matching with the TPC, and the inner one is the minimum compatible with the radius of the beam pipe (3 cm). The silicon detectors feature the high granularity and excellent spatial precision required. Because of the high particle density, up to 90 cm−2 , the four innermost layers (r ≤ 24 cm) must be truly two-dimensional devices. For this task, silicon pixel and silicon drift detectors were chosen. The outer two layers at r = 45 cm, where the track densities are below 1 cm−2 , are equipped with double-sided silicon micro-strip detectors. With the exception of the two innermost pixel planes, all layers have analog readout for particle identification via a dE/dx measurement in the non-relativistic region. This gives the inner tracking system a stand-alone capability as a low-pt particle spectrometer. 3
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Page 5 and 6: Contents Introduction ix 1 The ALIC
Page 7 and 8: CONTENTS 4 2D compression algorithm
Page 9 and 10: Introduction This thesis work has b
Page 13: Chapter 1 The ALICE experiment ALIC
Page 17 and 18: 1.1 — The Inner Tracking System t
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Page 21 and 22: 1.2 — Design of the drift layers
Page 23 and 24: 1.3 — The SDDs (Silicon Drift Det
Page 25 and 26: PASCAL AMBRA 1.4 — SDD readout sy
Page 27 and 28: data_in[0] data_in[1] data_in[2] da
Page 29 and 30: 1.4 — SDD readout system 1.4.2 Ev
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Page 33 and 34: Chapter 2 Data compression techniqu
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Page 37 and 38: 2.3 — Compression techniques 2.3.
Page 39 and 40: 2.4 — Lossless compression techni
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Page 47 and 48: 2.5 — Lossy compression technique
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Symlets sym2 sym3 sym4 sym8 Wavelet
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Chapter 3 1D compression algorithm
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3.2 — 1D compression algorithm Fi
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3.3 — 1D algorithm performances s
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3.3 — 1D algorithm performances F
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3.4 — CARLOS v1 Figure 3.6: CARLO
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3.4 — CARLOS v1 Figure 3.7: Pictu
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3.4 — CARLOS v1 3.4.3 Functions p
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3.5 — CARLOS v2 have a 100% compa
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3.5 — CARLOS v2 3.5.1 The firstch
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3.5 — CARLOS v2 data and when loa
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3.5 — CARLOS v2 which of the 8 qu
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- indat6 : input 32-bit bus; - inda
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3.5 — CARLOS v2 - femux is a mult
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3.5 — CARLOS v2 total optical fib
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3.5 — CARLOS v2 Figure 3.11: Desi
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3.5 — CARLOS v2 that CARLOS will
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3.6 — CARLOS v2 design flow Figur
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3.7 — Tests performed on CARLOS v
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Chapter 4 2D compression algorithm
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4.2 — CARLOS v3 vs. the previous
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4.3 — The final readout architect
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4.5 — CARLOS v3 building blocks -
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4.5 — CARLOS v3 building blocks T
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4.5 — CARLOS v3 building blocks F
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4.5 — CARLOS v3 building blocks c
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4.5 — CARLOS v3 building blocks o
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4.5 — CARLOS v3 building blocks u
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4.5 — CARLOS v3 building blocks a
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4.5 — CARLOS v3 building blocks p
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4.7 — CARLOS layout features post
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Chapter 5 Wavelet based compression
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levels used: 5.1 — Wavelet based
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5.2 — Multiresolution algorithm o
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5.3 — Choice of the architecture
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5.3 — Choice of the architecture
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Dettaglio 1 1 D1 2 Downsample Hi_De
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2 Upsample Dettaglio 1 1 D1 Hi_Rec
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5.4 — Multiresolution algorithm p
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5.5 — Hardware implementation ter
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5.5 — Hardware implementation Fig
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5.5 — Hardware implementation com
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5.5 — Hardware implementation Haa
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Conclusions The main goal of this t
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Bibliography [1] ALICE Collaboratio
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BIBLIOGRAPHY [19] D. Cavagnino, P.
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