Ron Settles MPI-Munich/Desy Tsinghau/CCAST TPC School January 2008 Experience with the Aleph TPC (and other things) Ron Settles MPI-Munich/Desy 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 Outline What physics do we want to do, where? What is the best detector? TPC and the Aleph TPC 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

International Linear Collider Where?: Technology decision: COLD superconducting à la TESLA chosen International Linear Collider Baseline: 200 GeV < √s < 500 GeV Integrated luminosity ~ 500 fb-1 in 4 years 80 % e- beam polarisation Upgrade to 1TeV, L = 1 ab-1 in 3 years 2 interaction regions Concurrent running with the LHC from 2015 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

The Global Design Effort Formal organization begun at LCWS 05 at Stanford in March 2005 when Barry became director of the GDE ACFA’07 Beijing: RDR(+cost), DCR Technically Driven Schedule 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 Physics we want to do? Keisuke gave a nice overview yesterday For example, from my talk at Arlington WS Jan.2003: 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 2018 2019 2020 2024 +y 2027 +y+SF 25 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 Where are we with the Higgs? CERN Courier, Nov 2005 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 Very latest electroweak combinations: 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 Why do we think these indirect, precision meas. are telling us anything??? CERN Courier, Nov 2005 : 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 The value of precision measurements… 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 Polarization Multipole expansion 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

And in addition we have LEP events… Expt (GeV) Decay Channel (GeV/c2) ln(1+s/b) 115 GeV/c2 1 ALEPH 206.7 4-jet 114.3 1.73 2 112.9 1.21 3 206.5 110.0 0.64 4 L3 206.4 E-miss 115.0 0.53 5 OPAL 206.6 110.7 6 Delphi 0.49 7 205.0 Lept 118.1 0.47 8 208.1 Tau 115.4 0.41 9 114.5 0.40 10 205.4 112.6 …the Higgs? 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 But this all may be a fata morgana… LCs 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Speed of light in the filaments is slower than in the voids. Take this into account, ‘dark energy’ is a fata morgana? And in reality…? 75% Dark matter 25% Baryons Is this true?? 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 What is the best detector? 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 High precision tracking… 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 Highly efficient tracking, high granularity calorimetry… 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 LDC/GLD=ILD Concept or A TPC for a Linear Collider Detector 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 LDC HCal ECal TPC GLD 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 Now 2x10-5/(GeV/c) Now 0.25/E @ Zpeak Particle Flow 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

The Aleph Time Projection Chamber Ron Settles, MPI-Munich/DESY (talk at Mike Ronan’s TPC Symposium@LBNL 2003) 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 Summary TPC is a 3-D imaging chamber Large volume, small amount of material. Slow device (~50 ms) 3-D ‘continuous’ tracking (xy  170 mm, z  600 mm for Aleph) Review some of the main ingredients History First proposed in 1976 (Dave Nygren, 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… 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 Outline Examples TPC principles of operation Drift velocity, Coordinates, dE/dx TPC hardware ingredients Field cage, gas system, wire chambers, gating, laser calibration system, electronics The Aleph TPC From the drawing board to the gadget Performance Some ‘features’ (i.e. trouble shooting…) Conclusion 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 Some TPC examples STAR FTPC ALICE ILD (future) … Grand-daddy/mama of all TPCs 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

TPC principles of operation gas volume with E & B fields A TPC contains: Gas E.g.: Ar + 10-20 % CH4 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 • B y electron drift E x z charged track wire chamber to detect projected tracks Now trying out new techniques--► 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 TPC Characteristics Only gas in active volume, small amount of material Long drift ( > 2 m ) therefore slow detector (~50 ms) 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 B drift y E x z charged track • 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 Drift velocity Drift of electrons in E- and B-fields (Langevin) • mean drift time between collisions particle mobility cyclotron frequency Vd along E-field lines Vd along B-field lines Typically ~5 cm/ms for gases like Ar(90%) + CH4(10%) Electrons tend to follow the magnetic field lines (vt) >> 1 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 3-D coordinates z track Z coordinate from drift time X coordinate from wire number Y coordinate? along wire direction need cathode pads • projected track y wire plane x 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Coordinate from cathode Pads x y Amplitude on ith pad avalanche position projected track position of center of ith pad z pad response width • drifting electrons y avalanche pads Measure Ai Invert equation to get y 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

TPC Coordinates: Pad Response Width Distance between pads Normalized PRW: is a function of: • the pad crossing angle b spread in rf the wire crossing angle a ExB effect, lorentz angle  the drift distance diffusion 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

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 (…disappears with new technologies…) “diffusion” term forward tracks -> longer pulses -> degrades resolution 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Particle Identification by dE/dx Energy loss (Bethe-Bloch) 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 • mass of electron charge and velocity of incident particle mean ionization energy density effect term 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

TPC ingredients (Aleph example) Wire chambers Gating Cooling Mechanics Field cage Gas system Laser system Electronics 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 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 cm2 gas gain typically 3-5x103 Drift region gating grid cathode plane V=0 sense wire z pad plane x field wire 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 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 • 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 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 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 Cooling, Mechanics Terribly mundane but terribly important (everything is important) Cooling: Combined air and water cooling to completely insulate the gas volume Mechanics: 25% X_0 for sectors, preamps, cooling (but before cables) 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

E-field produced by Field Cage z wires at ground potential planar HV electrode E HV 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 • 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

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 mm & 19 mm thickness, 10.1 mm pitch, 1.5 mm gap) on Kapton Insulator wound Mylar foil (75mm) Resistor chains 2.004 M (0.2%) Nucl. Instr. and Meth. A294 (1990) 121 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

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 firstcorrections. After, tracks (mostly μ pairs from Z decays) used exclusively (read on…) Laser tracks in the ALEPH TPC • 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 Gas system Typical mixtures: Ar91%+CH49% Ar93%+CH45%+CO22% Ar93%+CF43%+IsoB1% Operation at atmospheric pressure Properties: Drift velocity (~5cm/ms) Gas amplification (~7000) Signal attenuation my electron attachment (<1%/m) Parameters to control and monitor: Mixture quality (change in amplification) O2 (electron attachment, attenuation) H2O (change in drift velocity, attenuation) Other contaminants (attenuation) • 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Influence of Gas Parameters (*) (*) from ALEPH handbook (1995) 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Electronics: from pad to storage TPC pad Pre-amplifier charge sensitive, mounted on wire chamber Shaping amplifier: pole/zero compensation. Typical FWHM ~200ns amp FADC Flash ADC: 8-9 bit resolution. 10 MHz. 512 time buckets Multi-event buffer zero suppression Digital data processing: zero-suppression. feature extraction Pulse charge and time estimates DAQ Data acquisition and recording system 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 Analog Electronics ALEPH analog electronics chain Large number of channels O(105) Large channel densities Integration in wire chamber Power dissipation Low noise 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 More details about Aleph… 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 Wire Chambers: ALEPH Long pads for better coordinate precision 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

After 3 man-centuries (or more, depending on how you count)… …as usual, lots of meetings…↓ From TPC90…↑ 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

From the drawing board to the gadget… 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 A Detector with TPC you end up with-----------► …where… 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 Thanks to many people… (and to Pere Mato and Werner Wiedenmann for help on these slides) …you need a few cables, cooling, etc… 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

It finally started working… 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

ALEPH Event, early days… 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 And towards the end… 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Coordinate Resolution(1): ALEPH TPC 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Coordinate Resolution(2): ALEPH TPC 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 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) 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 But, there were ‘FEATURES’… Werner’s talk contains many details, see alephwww.mppmu.mpg.de/~settles/tpc  • here a few examples… 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Historical Development (1) 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 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 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Historical Development (2) 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 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 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 Examples from Werner’s slides… 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 e.g. (see Werner’s slides…) 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

e.g., non-linear F.C. potential 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

e.g., disconnected gating grids 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 e.g., field-cage shorts 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 (N.B., design your detector to be easily accessible…) 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 the bottom line (e.g., momentum resolution) 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008

Ron Settles MPI-Munich Tsinghua TPC School Jan.2008 Conclusion 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… 09/01/2008 Ron Settles MPI-Munich Tsinghua TPC School Jan.2008