Development of Precision Muon Drift Tube Detectors for the High-Luminosity Upgrade of the LHC

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1 Development of Precision Muon Drift Tube Detectors for the High-Luminosity Upgrade of the LHC R. Richter, H. Kroha, B. Bittner, J. Dubbert, S. Horvat, O. Kortner, M.Kilgenstein, F. Legger, Ph. Schwegler Max-Planck-Institut für Physik, Munich S. Adomeit, O. Biebel, A. Engl, R. Hertenberger, F. Rauscher, A. Zibell Ludwig-Maximilians Universität, Munich June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 1 H. Kroha, 22/04/2010

2 Outline The slhc project The ATLAS muon spectrometer: occupancies at L peak = 4 * cm -2 s -1 Properties of Small Tubes (30 vs. 15 mm diam.) A new Small Wheel: geometry and tube numbers Technology of chamber construction A new readout architecture June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 2

3 LHC with high luminosity (slhc) Longterm planning for LHC 4000 fb the BIG upgrade Aim for high luminosiy (slhc): ~ 3000 fb -1 in years Many parts of the ATLAS detector are not able to handle such high particle rates and the sustain the corresponing rad. load need new technology and big detector upgrade IBL,new Sm Wh? year M. Nessi, ATLAS-Woche, febr L peak = 4 * cm -2 s -1 ~ 300 fb -1 /Jahr Original aim for LHC: ~ 500 fb -1 in 10 years The present ATLAS detector has been designed for these data rates and radiation load Technical challenges for ATLAS at slhc: high density of charged and neutral particles Limitation by granularity and time resol. of the subdetectors high data rates Limitation by available bandwidth for the readout high radiation load The frontend R/O electronics was only designed for 10 y s at LHC June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 3

4 Integrated vs. peak luminosity of the LHC/sLHC is peak luminosity at the beginning of the fill and decays exponentially for about 4-5 h until beam is dumped. Refill takes about 4-5 h. At peak luminosity the beam decays faster and the refill takes longer. Luminosity levelling can be used to reduce the peak luminosity, while keeping the integrated lumin. constant!!! Peak lumin. is 4 * not 10 * various schemes of the machine operation avg. lumi. June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 4

ATLAS Geometry now and at slhc Main problem for the ID: high track densities (~ 8000 tracks / beam crossing) requires completly new ID with higher granularity Main problem for the muon system: high

5 ATLAS Geometry now and at slhc Main problem for the ID: high track densities (~ 8000 tracks / beam crossing) requires completly new ID with higher granularity Main problem for the muon system: high background rates from converted n/γ s requires new chambers in some regions of the detector Many constraint for upgrade due to existing detector features: Dimensions of Magnets, Calorimeters, Muon system, maximum trigger rate, passages for services, size of the hall and available space in adjacent service halls. June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 5

6 Background hit rates in the muon system Small Wheel Big Wheel Outer Wheel Cool region Simulated rates for n/γ background Hot regions 1 step = fact. 2,15 Very hot region: CSC chambers used photon flux (khz/cm 2 ) Radiation Task Force (2003 ) Tracking in the hot regions at SLHC will suffer from high background rates need different detector concepts June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 6

7 Occupancy at 4 x nom. luminosity in the muon end-cap (all rates contain safty factor = 5) Expected performance of MDT tubes in the ATLAS muon spectrometer (schematic) low η Small Wh. Big Wh. Outer Wh. low η 31 % 25 % 14 % mid η 37 % 35 % 12 % high η 68 % 46 % 11 % Occupancies in the end-cap occupancy κ = hit rate * signal duration mid η low η 73 % 78 % 87 % mid η 69 % 71 % 89 % high η 50 % 63 % 90 % Efficiencies in the end-cap efficiency ε = exp (-κ) = 1 κ + κ 2 / high η Small Wheel Big Wheel Outer Wheel For reliable track reconstruction a single tube efficiency > 70 % is required (occup. < 30 %) the present end-cap MDTs are not suited for highluminosity operation need technology with high rate capability June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 7

8 Circular vs. Planar Drift Cell Chambers µ PRO circular geometry: Accuracy independ on angle of incidence Modular design: each tube is an independent detector unit fault tolerance Easy to pressurize: high accuracy µ µ CONTRA circular geometry: long drift time exposure to background hits long signal duration (depending on radius) significant dead time limited capability for double track resolution exposure to background hits angles of incidence up to 45 o June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 8

9 Why Small tubes? In the same rad. environment Large and Small tube chabers look as below! PROs of Small tubes: short drift time short dead time low occupancy high efficiency more independent measurements along a given track length high tracking efficiency µ 30 mm diam. tubes 50% occup. 15 mm diam. tubes 7% occup. Problems with Small tubes: More material & multiple scattering Higher channel count & cost difficult implementation of services June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 9

10 Compare 30 mm tubes to 15 mm tubes Example: occupancy in the Small Wheel 30 mm tubes low η 31 % 73 % mid η 37 % 69 % high η 68 % 50 % occup. effic'y Reduction of occupancy by a factor of ~ 7! Why? 15 mm tubes 15 mm tubes low η 4,2 % 96 % mid η 5,0 % 95 % high η 9,1 % 91 % occup. effic'y June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 10

Smaller Drift Tube Diameter for High Rates 15 mm, small tube for SLHC The non-linear r-t relation is due to Ar/CO 2 gas Advantages of 15 mm over 30 mm tubes (same drift gas and gas gain): Tube

11 Smaller Drift Tube Diameter for High Rates 15 mm, small tube for SLHC The non-linear r-t relation is due to Ar/CO 2 gas Advantages of 15 mm over 30 mm tubes (same drift gas and gas gain): Tube counting rate ~ tube diameter: 2.0 x smaller Occupancy ~ max. drift time (700 ns 200 ns): 3.5 x smaller Total occupancy 7 x smaller for same tube length. Gain drop (due to space charge) ~ tube radius r 3 : 8 x smaller 30 mm standard MDT tube June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 11

12 A layout of the Small Wheel w. 15 mm tubes Small tube drift chambers replacing standard chambers in the regions of highest hit rates Schematic) low η Small Wh. Big Wh. Outer Wh. low η 4 % 25 % 14 % mid η 5 % 35 % 12 % high η 9 % 6 % 11 % Occupancies in the end-cap mid η low η 96 % 78 % 87 % mid η 95 % 71 % 89 % high η 91 % 94 % 90 % Efficiencies in the end-cap high η Small Wheel Big Wheel Outer Wheel Upgrade of the Small wheel with small-tube drift chambers will make the end-cap region of the muon spectrometer ready for SLHC The rate capabilities of the small-tube ch s even allow to use them in the region presently covered by the CSC (see next slide) June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 12

13 Small tubes can be used in the CSC region (η>2.4) 15 mm drift-tube chamber CSC region CSC region low η 6 % 95 % mid η 9 % 91 % high η 13 % 88 % occup. effic'y Integrated design for the CSC region Precision tracking chamber: 2 x 8 smalltube layers 2nd coordinate and trigger chamber: fast 2D detector with 2 3 mm spatial resolution 2nd coord. and trigger 10 cm 28.5 cm 39µm chamber resol. at 8 khz/cm 2 99% track reconstruction efficiency up to 2000 khz/tube June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 13

14 Resolution studies with small tubes, using a cosmic ray setup in the Gamma Irradiation Facility at CERN (GIF) Presently there is no beam available for the GIF. (A new GIF is under construction in the North Area of CERN) June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 14

GIF High Rate Test 2008/2009 Upper reference chamber 15 mm tubes, 1m long Lower reference chamber 590 GBq Cs 137 γ source Cosmic trigger scintillation counters

15 GIF High Rate Test 2008/2009 Upper reference chamber 15 mm tubes, 1m long Lower reference chamber 590 GBq Cs 137 γ source Cosmic trigger scintillation counters Background rates up to 8 khz/cm 2,1200 khz/tube (max. rate at 7 x design) June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 15

16 Drift Tube Efficiency Efficiency for hits on muon tracks within the drift-tube resolution The strength of the γ-source did not allow to go up to 2000 khz/tube in this test June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 16

Spatial resolution vs. r in 30 mm tubes Spatial resol. of MDT tubes as a function of impact radius and BG level, measured at the GIF *) Gain drop effect due to space charge Irrad. rates: o 1.

17 Spatial resolution vs. r in 30 mm tubes Spatial resol. of MDT tubes as a function of impact radius and BG level, measured at the GIF *) Gain drop effect due to space charge Irrad. rates: o 1.0 khz/cm 2 o 0.7 khz/cm2 o 0.35 khz/cm2 o 0.2 khz/cm2 o no BG Resolution deterioration due to space charge fluctuations µ impact radius Resolution of a 30 mm tube vs. BG rate *) S.Horvat et al., IEEE TNS Vol.53, No.2 (2006) 562 from GIF test 2004 June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 17

18 Drift Tube Resolution at High Rates: large vs. small tubes average single-tube resolution [µm] mm diameter tubes 15 mm diameter tubes rate [khz/cm ] Without γ-background: Small tubes behave like large tubes inside 7,5 mm (no space charge) With γ-background: Small tubes show much smaller slope in resolution vs. rate than large tubes because of strongly reduced space charge June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 18

19 Conclusions Because of high occupancy, gain drop and resulting low hit efficiency, an upgrade of the Small Wheel is necessary. 15 mm drift tubes provide an attractive upgrade option for the Small Wheel, including the CSC region. June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 19

Technical challenges of small tube chamber construction precision assembly of tubes with 20 µm accuracy individual gas supply to each tube HV supply at

20 Technical challenges of small tube chamber construction precision assembly of tubes with 20 µm accuracy individual gas supply to each tube HV supply at small insulation distances many R/O electronics channels on a small area June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 20

21 Gas Distribution Injection molded plastic (Pocan) gas connections including gas distribution bars June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 21

HV decoupling capacitors: removed from RO/ HV hedgehog cards to reduce density of components, requiring no

22 HV decoupling and Signal distribution present HV distribution: HV decoupling caps and signal routing on same PC NB: There is no HV on the RO distribution boards!! Facilitates high density signal routing significantly! HV decoupling capacitors: removed from RO/ HV hedgehog cards to reduce density of components, requiring no additional space in tube direction. June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 22

23 Drift Tube Design gas distribution HV decoupling Reference surface for chamber assembly wire locator (twister) inserted inside June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 23

24 High Readout channel density R/O architecture of the present system for Large tubes R/O architecture of the future system for Small tubes (interfacing to the existing R/O chain) HH ASD AMT standard MDT R/O connector to CSM 6 MROD 4 x 6 or 3 x 8 mezzanine card serving 24 tubes General concept for mezzanine layout: Increase modularity to reduce component numbers on PCB higher channel density of R/O electronics. Maintain as many components from the existing system as possible module of 8 x 12 tubes x 80 Mb/s 32 3 x 80 Mb/s 32 3 x 80 Mb/s mezzanine card new mezzanine card serving 96 tubes 6 standard CSM serv. 3 x 6 AMTs with 576 channels = 6 modules LV power June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 24

Assembly and wire positioning accuracy 2D assembly jig Glueing of 8 tube layers per day in a single step ± 20 µm Accuracy achieved in a 12 x 8 tube module - assembled for H8 testbeam and GIF test

25 Assembly and wire positioning accuracy 2D assembly jig Glueing of 8 tube layers per day in a single step ± 20 µm Accuracy achieved in a 12 x 8 tube module - assembled for H8 testbeam and GIF test 2009 at MPI Munich - wire positions measured at the LMU Cosmic Ray Facility with 2 MDT reference chambers (large tubes) June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 25

26 Chamber Assembly Facility Clean room Assembly jig June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 26

(mezzanine cards) 110 cm Full Small tube chamber prototype for testbeam and GIF 2010 2

27 Chamb. for 2nd co-ordinate and trigger (RPC? TGC?) Prototype Chamber 100 mm 280 mm 55 cm 100 cm Existing MDT RO Elx. (mezzanine cards) 110 cm Full Small tube chamber prototype for testbeam and GIF x 8 tube layers à 72 tubes per layer (1152 channels) June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 27

28 Schedule Preliminary chamber and electronics board design ready Start of prototype construction in 2 weeks for testbeam and GIF in summer 2010 Testbeam and GIF studies ongoing. And waiting for the NEW GIF in the North Hall! High-rate tests with with neutrons and protons at the tandem accelerator at LMU in June and September 2010 Drift-tube aging tests under preparation. All components and materials have been tested for ATLAS MDTs First prototype of radiation hard ASD chip produced June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 28

29 Backup Slides June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 29

30 Drift Tube Design, cont. (chromatize d) Reference surface for assembly Endplug insulator material: Crastin (PBT), Polyester material similar as Pocan approved for aging for MDTs), cheap, good mechan./chemical properties, better than Noryl (also possible). June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 30

31 Chamber Assembly Facility Injection moulded endplugs Semi-automated drift-tube assembly Commercial Al-tubes (0.4 mm wall) June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 31

32 Scoring Regions CSCs June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 32

33 Chamber Tracking Efficiency Only 2 x 5 tube layers needed for > 99% tracking efficiency at max. 4 x design rate (CSC region). 2 x 4 tube layers sufficient for rest of Small Wheel (< 400 khz/tube). Max. 4 x nom. luminos. 15 mm tubes (statistical calculation) June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 33

34 Channel count for a Small Wheel Layout Tube lengths in the Small Wheel vary from 55cm (inner part in CSC region) to 260 cm (outer edge of the Small Wheel) Region h < 2.4 (now equipped w. MDT): 32 chambers * ~ 600 = tubes Region h > 2.4 (now equipped w. CSC): 16 chambers * 960 = tubes Total: tubes June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 34

35 June, 9th, 2010 MDT detectors for High Luminosity 12th IPRD Seminar, Siena R. Richter 35 7/6/2010 L. Rossi IPRD10 - Siena 35

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