Straw Tube Drift Chamber for the LHCb Tracking
Straw Tube Drift Chamber for the LHCb Tracking System Beijing (Tsinghua University), 18 -11 -2002 Outline: Detector Design and Test-beam Results: ü LHCb Tracking & OT Design ü OT Modules & Straw Tubes ü Gas Mixture & Drift Time Module Construction: ü Straw Material ü Injection Molding ü Module Design & Prototypes Electronics: ü FE Layout and TFC Distribution ü HV Boards ü OTIS TDC Antonio Pellegrino
LHCb Tracking System B-production strongly “forward”-peaked LHCb ~ “forward” spectrometer q charged particles “analyzed” through magnet tracked with: high-flux region (2%): Si detector (Inner Tracker) v remaining area (98%): straw drift-tubes (Outer Tracker) v 9/17/2020 Antonio Pellegrino 1
Tracking System Functions q measure charged-particles momenta: q link VErtex LOcator CAL/m system q provide angular info (with sufficient resolution) to Particle-IDentification system (RICH) 9/17/2020 Antonio Pellegrino 2
Tracking System Performance Ø high resolution: 10 Me. V in “BS DS K” invariant mass dp/p ~ 0. 4% Øhigh efficiency (multi-particle f. s. ): 80% rec. eff. “BS DS (KKp) K” 95% tracking efficiency 9/17/2020 Antonio Pellegrino 3
The Outer Tracker Design B-Field vertical measure x-coordinate OT Station consist of 4 layers: XUVX (q. U, V = 5 o sufficient to reduce combinatory) modular design: layers are composed of modules 9/17/2020 Antonio Pellegrino 4
The Outer Tracker Design (cont’d) Occupancy (%) IT/OT Boundary optimized on the basis of occupancy studies: require average occupancy < 10% position along z (a. u. ) 9/17/2020 Antonio Pellegrino 5
OT Module Design Straw Tubes packed in double-layered modules 64 -cells wide ® only ~0. 7% of 1 X 0: m “light” panels (honeycomb core with carbon skins) m “light” straws ® 9/17/2020 Antonio Pellegrino 6
Straw Tubes Cell diameter ~5 mm: reasonable occupancy sufficiently fast signal collection time ¨ T 25 ns , unrealistic ¨ T 50 ns , workable (Contamination of events from neighboring bunch crossings) 9/17/2020 Antonio Pellegrino 7
Gas Mixture and Drift Time T 50 ns fast drift gas: add CF 4 to basic Ar/CO 2 mixture Drift-time spectra measured … Ar(65)/CO 2 (5)/CF 4 (30) Drift time (ns) …and reproduced with GARFIELD simulation 9/17/2020 Antonio Pellegrino 8
Test Beam Results Drift time (ns) Measured t-r relation, coordinate resolution (~0. 2 mm), efficiency (~96%), etc. Distance from Wire (mm) Ar(75)/CO 2 (10)/CF 4 (15) selected as baseline 9/17/2020 Antonio Pellegrino 9
Straw Material CF 4 presence chose polymer as straw material: q 0. 040 mm thick Kapton XC (25% volume doping with Carbon), (370 W/cm 2 ~12 KW/m) q Passed extensive ageing tests q two windings ensure sufficient gas tightness 9/17/2020 Antonio Pellegrino 10
Straw Cross Talk The cathode (straw) material determines the level of analog (straw-to-straw) cross-talk I. e. different choices of the outer winding material: Ø 0. 025 mm Aluminum 0. 5% analog cross talk Ø 0. 040 mm Kapton XC 1. 8% analog cross talk Baseline solution: outer winding of pre-laminated Kapton XC (0. 025 mm)/Aluminium(0. 012 mm) foil (Straw winding material budget ~0. 12 of 1 X 0) 9/17/2020 Antonio Pellegrino 11
Injection-Molded Parts For the construction of the OTR modules a large number (~400000) of “small” pieces is required: q q wire locators: inserted in the straw to support the wire every 80 cm middle- and end-blocks: support wire at straw ends and define counting-gas volume This large number of small parts can be produced with injection-molding techniques, without compromising the tight local tolerances (0. 02 0. 05 mm) 9/17/2020 Antonio Pellegrino 12
Detailed Design of Detector Modules 9/17/2020 Antonio Pellegrino 13
Module Prototypes OT Module Prototype (2. 5 m long) built at NIKHEF 9/17/2020 Antonio Pellegrino 14
Module Prototypes (cont’d) OT Module Prototype (1 m long) built at Heidelberg 9/17/2020 Antonio Pellegrino 15
OT Electronics On-Detector FE Electronics: wire feed-through, HV, preamp, TDC Counting Room FE Electronics: Data serializer 9/17/2020 FE Electronics: Control & Bias, Monitor, … L 1 Electronics DAQ and L 1 Farm Antonio Pellegrino 16
OT Electronics (cont’d) 9/17/2020 Antonio Pellegrino 17
FE Electronics GOL OTIS ASDBLR HV board 9/17/2020 Antonio Pellegrino 18
FE Electronics Components 9/17/2020 Antonio Pellegrino 19
FE Electronics Assembly 9/17/2020 Antonio Pellegrino 20
FE Electronics Mock-up Models Needs modeling to assess mechanical details GND Spring +HV SMD connector 9/17/2020 Antonio Pellegrino 21
HV Boards Not just a bunch of capacitors! Strict demands: q signal (2 f. C/10 ns 300 W = 0. 06 m. V) and HV (~1500 V) separation q good transmission of fast (~10 ns) signal GND plane all along signal path q noise level << signal (2 f. C/10 ns = 200 n. A) q compact design: 5 mm channel pitch and small-space constraints (~40 mm for the whole thickness of the FE box) q high reliability: 10 years operation with scarce possibilities of access for repair 9/17/2020 Antonio Pellegrino 22
HV Boards Design Main design ingredients: ü high-quality capacitors JOHANSON 302 R 29 W 331 KV 4 E ü capacitors “buried” inside the PCB First prototypes unsuccessful: after 4 weeks test, 19 broken channels out of 10 x 32 (6 out of 10 boards with at least one broken channel)! air gap under capacitors V remains of cleaning “slurry” V inaccurate hand-placing of capacitors V 9/17/2020 Antonio Pellegrino 23
HV Boards Production Improved production procedure (19 HV boards): ü carried out under vacuum ü pick-and-place glueing avoids air-gap under capacitors ü accurate (robot) placement of capacitors ü soldering area cleaned with plasma (instead of slurry) First tests: ITOT(608 chans) < 50 n. A, up to HV=+2. 5 k. V and T=80 o. C Long-term tests of ~1000 channels forthcoming… 9/17/2020 Antonio Pellegrino 24
OTIS TDC 4 x 320 MBit/s Drift time measurement Mounting on detector Approx. 50, 000 channels 4 TDC (32 channels each) gets serialised and transmitted optically (1. 28 GBit/s) 9. 6 GBit/s ¢ OTIS TDC designed at ASIC Heidelberg (Harald Deppe, Uwe Stange, Ulrich Trunk, Ulrich Uwer) ¢ Chip Requirements: 1 ns resolution (6 bit) drift times of up to 50 ns 40 MHz, clock driven design 1. 1 MHz L 0 trigger rate up to 10% occupancy 4µs trigger latency radiation hard design (pipeline length: 160) 9/17/2020 Antonio Pellegrino 25
OTIS v 1. 0 q q q First prototype with basic functionality ~700. 000 transistors 5100µm x 6000µm Tape out: 15/04/2002 Delivery: 29/07/2002 Small test PCB with possibility to connect ASD and GOL chips 9/17/2020 Antonio Pellegrino 26
OTIS v 1. 0 (cont’d) Power. Up Reset as expected Power Consumption DLL: Lock Time Lock Lost 550 m. W 1µs not observed DAC as expected Slow Control as expected Fast Control: Memory and Trigger Management, Data Output, Debug Features Memory Selftest no errors found problems Drift Time Encoding not yet understood OUTLOOK Ø Further investigations concerning drift time encoding Ø More chips, performance tests, random trigger tests, . . . Ø Operation with detector prototype Ø Commissioning of the read out chain including TTCrx 9/17/2020 Antonio Pellegrino 27
Station Frames Proposal contained in the OT TDR… modules mounted with dowel pins onto Al precision strips defining the module positions …a mock-up module for study 4 layers of each station mounted on Al frames was also built at NIKHEF each frame consists of two halves 9/17/2020 Antonio Pellegrino 28
Station Frames (cont’d) Working group to revise frame-design constraints and solutions: o Collaborate with ITR group for common solution o Revise global strategy: ØStations should move independently ØPositioning accuracies and reproducibility o Krakow group producing a case study Global Movement (TDR) 9/17/2020 Independent Movements (Krakow) Antonio Pellegrino 29
Project Milestones 9/17/2020 Antonio Pellegrino 30
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