1. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY1 The Aleph Time Projection Chamber Ron Settles, MPI-Munich/DESY TPC Symposium@LBNL 17 October 2003

2. TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY2 Summary u TPC is a 3-D imaging chamber –Large volume, small amount of material. –Slow device (~50  s) –3-D ‘continuous’ tracking (  xy  170  m,  z  600  m for Aleph) u Review some of the main ingredients u History –First proposed in 1976 (PEP4-TPC) –Used in many experiments –Aleph as an example here –Now a well-established detection technique that is still in the process of evolution…

3. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY3 Outline u Examples u TPC principles of operation –Drift velocity, Coordinates, dE/dx u TPC hardware ingredients –Field cage, gas system, wire chambers, gating, laser calibration system, electronics u The Aleph TPC u From the drawing board to the gadget u Performance u Some ‘features’ (i.e. trouble shooting…) u Conclusion

4. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY4 Some TPC examples Grand-daddy/mama of all TPCs STAR FTPC, ALICE, LC, …

5. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY5 TPC principles of operation A TPC contains: –Gas E.g.: Ar + 10-20 % CH 4 –E-field E ~ few x 100 V/cm –B-field as large as possible to measure momentum, to limit electron diffusion –Wire chamber (those days) to detect projected tracks y z x E B electron drift charged track wire chamber to detect projected tracks gas volume with E & B fields Now trying out new techniques-- ►

6. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY6 TPC Characteristics –Only gas in active volume, small amount of material –Long drift ( > 2 m ) therefore slow detector (~50  s) want no impurities in gas uniform E-field strong & uniform B-field –Track points recorded in 3-D (x, y, z) –Particle Identification by dE/dx –Large track densities possible y z x E B drift charged track

7. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY7 Drift velocity Drift of electrons in E- and B-fields (Langevin) mean drift time between collisions particle mobility cyclotron frequency V d along E-field lines V d along B-field lines Typically ~5 cm/  s for gases like Ar(90%) + CH 4 (10%) Electrons tend to follow the magnetic field lines (  ) >> 1

8. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY8 3-D coordinates z x y wire plane track projected track –Z coordinate from drift time –X coordinate from wire number –Y coordinate? »along wire direction »need cathode pads

9. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY9 Coordinate from cathode Pads projected track pads drifting electrons avalanche y x y z –Measure A i –Invert equation to get y Amplitude on ith pad avalanche position position of center of ith pad pad response width

10. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY10 TPC Coordinates: Pad Response Width Normalized PRW: Distance between pads is a function of: –the pad crossing angle  »spread in r  –the wire crossing angle  »ExB effect, lorentz angle  –the drift distance »diffusion

11. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY11 TPC coordinate resolution Same effects as for PRW are expected but statistics of drifting electrons must be considered electronics, calibration angular pad effect (dominant for small momentum tracks) angular wire effect forward tracks -> longer pulses -> degrades resolution “diffusion” term (…disappears with new technologies…)

12. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY12 Particle Identification by dE/dx –Energy loss (dE/dx) depends on the particle velocity. –The mass of the particle can be identified by measuring simultaneously momentum and dE/dx (ion pairs produced) –Particle identification possible in the non- relativistic region (large ionization differences) –Major problem is the large Landau fluctuations on a single dE/dx sample. »60% for 4 cm track »120% for 4 mm track Energy loss (Bethe-Bloch) mass of electron charge and velocity of incident particle mean ionization energy density effect term

13. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY13 TPC ingredients (Aleph example) u Wire chambers –Gating –Cooling –Mechanics u Field cage u Gas system u Laser system u Electronics

14. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY14 Wire Chambers 3 planes of wires –gating grid –cathode plane (Frisch grid) –sense and field wire plane –cathode and field wires at zero potential pad size –various sizes & densities –typically few cm 2 gas gain –typically 3-5x10 3 pad plane field wire sense wire gating grid Drift region cathode plane V=0 x z

15. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY15 Wire Chambers: ALEPH 36 sectors, 3 types –no gaps extend full radius wires –gating spaced 2 mm –cathode spaced 1 mm –sense & field spaced 2 mm, interleaved pads –6.2 mm x 30 mm –~1200 per sector –total 41004 pads readout pads and wires

16. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY16 Gating Problem: Build-up of space charge in the drift region by ions. –Grid of wires to prevent positive ions from entering the drift region “Gating grid” is either in the open or closed state –Dipole fields render the gate opaque Operating modes: –Switching mode (Aleph) –Diode mode

17. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY17 Cooling, Mechanics u Terribly mundane but terribly important (everything is important) u Cooling: –Combined air and water cooling to completely insulate the gas volume u Mechanics: –25% X_0 for sectors, preamps, cooling (but before cables)

18. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY18 E-field produced by a Field Cage HV E wires at ground potential planar HV electrode potential strips encircle gas volume –chain of precision resistors with small current flowing provides uniform voltage drop in z direction –non uniformity due to finite spacing of strips falls exponentially into active volume z y

19. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY19 Field cage: ALEPH example Dimensions cylinder 4.7 x 1.8 m Drift length 2x2.2 m Electric field 110 V/cm E-field tolerance  V < 6V Electrodes copper strips (35  m & 19  m thickness, 10.1 mm pitch, 1.5 mm gap) on Kapton Insulator wound Mylar foil (75  m) Resistor chains 2.004 M  (  0.2%) Nucl. Instr. and Meth. A294 (1990) 121

20. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY20 Laser Calibration System Purpose Measurement of drift velocity Determination of E- and B-field distortions Drift velocity Laser system  ∂( v_drift) ~ 1‰ Hookup tracks to Vdet  ∂( v_drift)~a few times 0.01‰ …used after Vdet installation ExB Distortions Laser used only in early days to get first corrections. After, tracks (mostly μ pairs from Z decays) used exclusively (read on…) Laser tracks in the ALEPH TPC

21. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY21 Gas system Properties: Drift velocity (~5cm/  s) Gas amplification (~7000) Signal attenuation my electron attachment(<1%/m) Parameters to control and monitor: Mixture quality (change in amplification) O 2 (electron attachment, attenuation) H 2 O (change in drift velocity, attenuation) Other contaminants (attenuation) Typical mixtures: Ar91%+CH 4 9%, Ar90%+CH 4 5%+CO 2 5% Operation at atmospheric pressure

22. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY22 Influence of Gas Parameters (*) (*) from ALEPH handbook (1995)

23. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY23 Electronics: from pad to storage TPC pad amp FADC zero suppression feature extraction DAQ Pre-amplifier charge sensitive, mounted on wire chamber Shaping amplifier: pole/zero compensation. Typical FWHM ~200ns Flash ADC: 8-9 bit resolution. 10 MHz. 512 time buckets Multi-event buffer Digital data processing: zero-suppression. Pulse charge and time estimates Data acquisition and recording system

24. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY24 Analog Electronics ALEPH analog electronics chain –Large number of channels O(10 5 ) –Large channel densities –Integration in wire chamber –Power dissipation –Low noise

25. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY25 More details about Aleph…

26. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY26 Wire Chambers: ALEPH Long pads for better coordinate precision

27. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY27 After 3 man-centuries (or more, depending on how you count) … From TPC90… ↑ …as usual, lots of meetings… ↓

28. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY28 From the drawing board to the gadget…

29. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY29 A Detector with TPC you end up with----------- ► …where…

30. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY30 Thanks to many people… (and to Pere Mato and Werner Wiedenmann for help on these slides) …you need a few cables, cooling, etc…

31. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY31 It finally started working…

32. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY32 ALEPH Event, early days…

33. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY33 And towards the end…

34. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY34 Coordinate Resolution(1): ALEPH TPC

35. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY35 Coordinate Resolution(2): ALEPH TPC

36. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY36 dE/dx: Results Good dE/dx resolution requires long track length large number of samples/track good calibration, no noise,... ALEPH resolution up to 334 wire samples/track truncated (60%) mean of samples 4.5% (330 samples)

37. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY37 But, there were ‘FEATURES’… Werner’s talk contains many details, see alephwww.mppmu.mpg.de/~settles/tpc  here a few examples…

38. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY38 Historical Development (1) u LEP start-up: 1989-1990 –Failure of magnet compensating power supplies in 1989 required development of field-corrections methods »derived from 2 special laser runs (B on/off) »correction methods described in NIM A306(1991)446 –Later, high statistics Z->μμ events give main calibration sample u LEP 1: 1991-1994 –VDET 1 becomes operational in 1991 –Development of common alignment procedures for all three tracking detectors –Incidents affect large portions of collected statistics and require correction methods based directly on data »1991-1993, seven shorts on field cage affect 24% of data »1994, disconnected gating grids on 2 sectors affect 20% of data –All data finally recuperated with data-based correction methods

39. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY39 Historical Development (2) u LEP 1/2: 1994-1996 –Tracking-upgrade program (LEP 1 data reprocessed) »Improved coordinate determination requires better understanding of systematic effects »Combined calculations for field and alignment distortions, reevaluation of B-field map –All methods for distortion corrections now based directly on data –Development of “few”-parameter correction models to cope with drastically reduced calibration samples at LEP 2 u LEP 2: 1995-2000 –New VDET with larger acceptance –Calibrations@Z at beginning of run periods have limited statistics –Frequent beam losses cause charge-up effects and new FC shorts »Superimposed distortions »Short-corrections with Z -> μμ;time-dep. effects tracked with hadrons

40. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY40 Examples from Werner’s slides…

41. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY41

42. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY42

43. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY43

44. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY44

45. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY45

46. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY46 e.g. (see Werner’s slides…)

47. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY47 e.g., non-linear F.C. potential

48. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY48

49. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY49 e.g., disconnected gating grids

50. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY50 e.g., field-cage shorts

51. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY51

52. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY52

53. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY53 (N.B., design your detector to be easily accessible…)

54. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY54 σ ~ 0.54E-03

55. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY55 the bottom line (e.g., momentum resolution)

56. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY56 Conclusion u We’d better learn from these past lessons so that the new TPC will evolve to a much better main tracker for the future LC  its performance will then improve by an order of magnitude relative to that at Lep…

57. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY57 Extra slides on LCTPC

58. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY58 Linear Collider TPC R & D A sampling of this work by Ron Settles

59. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY59 Goal To design and build an ultra-high performance Time Projection Chamber …as central tracker for the LC detector …where excellent vertex, momentum and jet energy precision are wanted…

60. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY60 LDC

61. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY61 GLD TPC

62. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY62 The basic idea… u Cost-effective way of instrumenting a large volume u With continuous tracking and a minimum of material u Want the largest possible granularity -- i.e. ~ 2. 10 9 voxels -- the best possible σ point resolution -- the best possible 2-track resolution

63. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY63 Why… u High granularity to ensure robust operation in presence of large backgrounds u Continuous tracking to ensure good momentum-measuring precision and >98% pattern-recognition eff. in jets

64. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY64 ILC-TPC A Large, High precision, High 3-D granularity Time Projection Chamber operated under a high magnetic field of 3 – 4 T Unprecedented requirements to TPC especially for granularity → use of micro pattern gas detector (MPGD) as a readout device  performance tests using prototypes

65. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY65 LCTPC/LP Groups (16 August 06) Americas Carleton Montreal Victoria Cornell Indiana LBNL MIT Purdue YaleEurope LAL Orsay IPN Orsay SaclayAachenBonnDESYUHamburgFreiburgKarlsruheMPI-MunichRostockSiegenNIKHEF UMM Krakow BucharestNovosibirsk PNPI StPetersburgLund PNPI StPetersburg LundCERNAsiaTsinghuaCDC:HiroshimaKEK Kinki U SagaKogakuin Tokyo UA&T U Tokyo U Tsukuba Minadano SU-IIT …Other groups interested?

66. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY66 Examples of Prototype TPCs Carleton, Aachen, Cornell/Purdue,Desy(n.s.) for B=0or1T studies Saclay, Victoria, Desy (fit in 2-5T magnets) Karlsruhe, MPI/Asia, Aachen built test TPCs for magnets (not shown), other groups built small special- study chambers

67. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY67 MPI-Munich prototype for Wires, Gem and Micromegas test in 5T at Desy and in 1T in beam at Kek

68. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY68 MWPC u Very

69. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY69 Replace ‘sensor (wire) gitter’ previous slide by either GEM or Micromegas: u Very GEM: Two copper perforated foils separated by an insulator The multiplication takes place in the holes. Usually used in 2 or 3 stages Micromegas : a micromesh sustained by 50-100  m - high insulating pillars. The multiplication takes place between the anode and the mesh One stage 200  m

70. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY70 GEM and Micromegas S1/S2 ~ E amplif / E drift S1 S2

71. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY71 Due to the high value of wt and the low grid transparency, does it work in a magnetic field? -> Simulations in Aachen

72. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY72 Prototype TPC Field cage maximum drift length: 260 mm typical cathode H.V. : - 6 kV Readout plane effective area: 100 mm×100 mm MWPC GEMs (3-stage) or MicroMEGAS

73. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY73 Experimental setup u Beam: mostly 4 GeV/c pions (0.5-4 GeV/c hadrons & electrons) u Magnet: super conducting solenoid without return yoke (max field: 1.2 T) TPC in JACCEE magnet Beam JECCEE inner diameter : 850 mm effective length: 1 m KEK  Beam Line We have conducted a series of beam experiments at KEK PS.

74. 17 October 2003TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY74 Readout scheme and Gas ALEPH TPC Electronics ： charge sensitive preamp. + shaper amp. (shaping time = 500 ns) + digitizer (time bucket = 80 nsec)