Download - The Aleph Time Projection Chamber
![Page 1: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/1.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
1
The Aleph Time Projection Chamber
The Aleph Time Projection Chamber
Ron Settles, MPI-Munich/DESY
TPC Symposium@LBNL17 October 2003
![Page 2: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/2.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
2
SummarySummary
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)
Review some of the main ingredients 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…
![Page 3: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/3.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
3
OutlineOutline
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
![Page 4: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/4.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
4
Some TPC examplesSome TPC examples
TPC ReferencePEP4 PEP-PROPOSAL-004, Dec 1976TOPAZ Nucl. Instr. and Meth. A252 (1986) 423ALEPH Nucl. Instr. and Meth. A294 (1990) 121DELPHI Nucl. Instr. and Meth. A323 (1992) 209-212NA49 Nucl. Instr. and Meth. A430 (1999) 210STAR IEEE Trans. on Nucl. Sci. Vol. 44, No. 3 (1997)
Grand-daddy/mama of all TPCsSTAR FTPC, ALICE, LC, …
![Page 5: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/5.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
5
TPC principles of operationTPC principles of operation
A TPC contains:– Gas
E.g.: Ar + 10-20 % CH4
– E-fieldE ~ few x 100 V/cm
– B-fieldas 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
chargedtrack
wire chamber to detect projected tracks
gas volume with E & B fields
Now trying out new techniques--►
•
![Page 6: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/6.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
6
TPC Characteristics
– Only gas in active volume,small amount of material
– Long drift ( > 2 m ) therefore slow detector (~50 s)want no impurities in gasuniform E-fieldstrong & 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
chargedtrack
0BE
•
![Page 7: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/7.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
7
Drift velocity
22
2
)()()(
)(1 B
BBE
B
BEEvd
Drift of electrons in E- and B-fields (Langevin) mean drift time between collisions
me particle mobility
mceB cyclotron
frequency1)( Vd along E-field lines
1)( Vd along B-field lines
Typically ~5 cm/s for gases like Ar(90%) + CH4(10%)
Electrons tend to follow the magnetic field lines () >> 1
•
![Page 8: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/8.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
8
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 •
![Page 9: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/9.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
9
Coordinate from cathode Pads
projected track
pads
drifting electrons
avalanche
y
x
y
z
– Measure Ai
– Invert equation to get y
)222)(( prwi
iyyAeA
Amplitude on ith pad
y avalanche position
iy position of center of ith pad
prw pad response width •
![Page 10: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/10.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
10
TPC Coordinates: Pad Response Width
Normalized PRW:
2
2
2ˆ
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
2̂
22 tan~ˆ
cos)tan(tan~ˆ 22
![Page 11: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/11.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
11
TPC coordinate resolution
Same effects as for PRW are expected but statistics of • drifting electrons must be considered
zz
z
D
r
)(
cos)tan(tan
tan
),,(
2
222
22
2
0
2
electronics, calibration
angular pad effect (dominant for small momentum tracks)
angular wire effect
forward tracks -> longer pulses -> degrades resolution
)_(22 angledipzZ
“diffusion” term
(…disappears with new technologies…)
![Page 12: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/12.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
12
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
2)1(
2ln
1 22
2
22
J
mv
A
ZKz
dx
dE
Energy loss (Bethe-Bloch)
m mass of electron
vz, charge and velocity of incident particle
J mean ionization energy density effect term
•
![Page 13: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/13.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
13
TPC ingredients (Aleph example)TPC ingredients (Aleph example)
Wire chambers – Gating– Cooling– Mechanics
Field cage Gas system Laser system Electronics
![Page 14: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/14.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
14
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
pad plane
field wire
sense wire
gating grid
Drift region
cathode plane
V=0
x
z
![Page 15: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/15.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
15
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
readoutpads and wires •
![Page 16: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/16.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
16
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
![Page 17: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/17.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
17
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)
![Page 18: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/18.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
18
E-field produced by a Field Cage
HV
Ewires 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
•
![Page 19: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/19.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
19
Field cage: ALEPH example
Dimensionscylinder 4.7 x 1.8 m
Drift length2x2.2 m
Electric field110 V/cm
E-field toleranceV < 6V
Electrodescopper strips (35 m & 19 m thickness, 10.1 mm pitch, 1.5 mm gap) on Kapton
Insulatorwound Mylar foil (75m)
Resistor chains2.004 M (0.2%)
Nucl. Instr. and Meth. A294 (1990) 121
![Page 20: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/20.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
20
Laser Calibration System
PurposeMeasurement 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
•
•
•
![Page 21: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/21.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
21
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)O2 (electron attachment, attenuation)
H2O (change in drift velocity, attenuation)
Other contaminants (attenuation)
Typical mixtures: Ar91%+CH49%, Ar90%+CH45%+CO25%
Operation at atmospheric pressure
•
![Page 22: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/22.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
22
Influence of Gas Parameters (*)
Parameterchange
Drif t velocity, vd Eff ect on gasamplifi cation, A
Signal ettenuation byelectron attachment
0.1% CH4 0.4 % -2.5% f or A = 1x104
10 ppm O2 Negligible up to 100 ppm Negligible up to 100 ppm 0.15%/ m of drif t
10 ppm H2O 0.5 % Negligible at 100 ppm < 0.03% / m of drif t
1 mbar Negligible if at max. -(0.5%-0.7%)
(*) from ALEPH handbook (1995)
![Page 23: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/23.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
23
Electronics: from pad to storageTPC pad
amp
FADC
zerosuppression
featureextraction
DAQ
Pre-amplifiercharge 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
![Page 24: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/24.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
24
Analog Electronics
ALEPH analog electronics chain
–Large number of channels O(105)–Large channel densities–Integration in wire chamber–Power dissipation–Low noise
![Page 25: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/25.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
25
More details about Aleph…More details about Aleph…
![Page 26: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/26.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
26
Wire Chambers: ALEPH
Long pads for better coordinate precision
![Page 27: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/27.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
27
After 3 man-centuries(or more, depending on how you
count)…
From TPC90…↑
…as usual, lots of meetings…↓
![Page 28: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/28.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
28
From the drawing board to the gadget…
![Page 29: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/29.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
29
A Detector with TPC
you end up with-----------►
…where…
![Page 30: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/30.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
30
Thanks to many people… (and to Pere Mato and Werner Wiedenmann for help on these slides)
…you need a few cables, cooling, etc…
![Page 31: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/31.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
31
It finally started working…
![Page 32: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/32.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
32
ALEPH Event, early days…
![Page 33: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/33.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
33
And towards the end…
![Page 34: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/34.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
34
Coordinate Resolution(1): ALEPH TPC
![Page 35: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/35.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
35
Coordinate Resolution(2): ALEPH TPC
![Page 36: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/36.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
36
dE/dx: Results
Good dE/dx resolution requires
long track lengthlarge number of samples/trackgood calibration, no noise, ...
ALEPH resolutionup to 334 wire samples/tracktruncated (60%) mean of samples4.5% (330 samples)
![Page 37: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/37.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
37
But, there were ‘FEATURES’…
Werner’s talk contains many details, see alephwww.mppmu.mpg.de/~settles/tpc • here a few examples…
![Page 38: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/38.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
38
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
![Page 39: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/39.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
39
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
![Page 40: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/40.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
40
Examples from Werner’s slides…
![Page 41: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/41.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
41
![Page 42: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/42.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
42
![Page 43: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/43.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
43
![Page 44: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/44.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
44
![Page 45: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/45.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
45
![Page 46: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/46.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
46
e.g. (see Werner’s slides…)
![Page 47: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/47.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
47
e.g., non-linear F.C. potential
![Page 48: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/48.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
48
![Page 49: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/49.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
49
e.g., disconnected gating grids
![Page 50: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/50.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
50
e.g., field-cage shorts
![Page 51: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/51.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
51
![Page 52: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/52.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
52
![Page 53: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/53.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
53
(N.B., design your detector to be easily accessible…)
![Page 54: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/54.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
54
σ ~ 0.54E-03
![Page 55: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/55.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
55
the bottom line (e.g., momentum resolution)
![Page 56: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/56.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
56
ConclusionConclusion
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…
![Page 57: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/57.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
57
Extra slides on LCTPC
![Page 58: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/58.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
59
GoalTo 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…
![Page 59: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/59.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
60
LDCLDC
![Page 60: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/60.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
61
GLDGLD
TPC
![Page 61: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/61.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
62
The basic idea…
Cost-effective way of instrumenting a large volume With continuous tracking and a minimum of material Want the largest possible granularity -- i.e. ~ 2 .109 voxels -- the best possible σpoint resolution -- the best possible 2-track resolution
![Page 62: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/62.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
63
Why…
High granularity to ensure robust operation in presence of large backgrounds
Continuous tracking to ensure good momentum-measuring precision and >98% pattern-recognition eff. in jets
![Page 63: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/63.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
64
Size: Effective volume = 4.1 m (diameter) × 4.6 m (full length)
Spatial resolution
r -φ : 100 – 200 μ m z: ≲ 1 mm
Two-track resolving power
r -φ : ≲ 2 mm z: ≲ 10 mm
Number of coordinate samples per track: ∼ 250
Momentum resolution (TPC alone)
δ Pt / Pt ∼ 10⁻⁴ Pt [GeV/c] for high momentum tracks
Particle identification capability: dE/dx ∼ 4%
ILC-TPCA 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
![Page 64: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/64.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
65
LCTPC/LP Groups (16 August 06) Americas
CarletonMontreal VictoriaCornellIndianaLBNLMIT
PurdueYale
EuropeEuropeLAL OrsayLAL Orsay IPN OrsayIPN Orsay
SaclaySaclayAachenAachenBonnBonnDESYDESY
UHamburgUHamburgFreiburgFreiburgKarlsruheKarlsruhe
MPI-MunichMPI-MunichRostockRostockSiegenSiegenNIKHEFNIKHEF
UMM KrakowUMM KrakowBucharestBucharest
NovosibirskNovosibirskPNPI StPetersburgPNPI StPetersburg
LundLundCERNCERN
AsiaAsiaTsinghuaTsinghua
CDC:CDC:HiroshimaHiroshima
KEKKEKKinki UKinki USagaSaga
KogakuinKogakuinTokyo UA&TTokyo UA&T
U TokyoU TokyoU TsukubaU Tsukuba
Minadano SU-IITMinadano SU-IIT
…Other groups interested?
![Page 65: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/65.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
66
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
![Page 66: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/66.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
67
MPI-Munich prototype for Wires, Gem and Micromegas test in 5T at Desyand in 1T in beam at Kek
![Page 67: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/67.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
68
MWPCMWPC
Very
![Page 68: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/68.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
69
Replace ‘sensor (wire) gitter’ previous slide by either GEM or Micromegas:Replace ‘sensor (wire) gitter’ previous slide by either GEM or Micromegas:
VeryGEM: Two copper perforated foils separated by an insulator
The multiplication takes place in the holes.
Usually used in 2 or 3 stages
Micromegas : a micromeshsustained by 50-100 m - high insulating pillars. The multiplication takes place between the anode and the meshOne stage
200 m
![Page 69: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/69.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
70
GEM and MicromegasGEM and Micromegas
S1/S2 ~ Eamplif / Edrift
S1
S2
![Page 70: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/70.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
71
Due to the high value of wt and the low grid transparency, does it work in a magnetic field? -> Simulations in Aachen
![Page 71: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/71.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
72
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
![Page 72: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/72.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
73
Experimental setup
Beam: mostly 4 GeV/c pions (0.5-4 GeV/c hadrons & electrons) 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.
![Page 73: The Aleph Time Projection Chamber](https://reader035.vdocument.in/reader035/viewer/2022062221/568138a4550346895da05fa3/html5/thumbnails/73.jpg)
17 October 2003 TPC Symposium@LBNL ALEPH TPC Ron Settles, MPI-Munich/DESY
74
Readout scheme and Gas
ALEPH TPC Electronics : charge sensitive preamp. + shaper amp. (shaping time = 500 ns) + digitizer (time bucket = 80 nsec)
Readout Device Pads: 32 pads ×12 pad rows
Width (pitch)× Length (pitch)
Gas (1 atm.)
Drift field
MWPC
SW spacing 2 mm
SW - Pads 1 mm
2 (2.3) mm×6 (6.3) mm
TDR
[Ar- 4CH (5%)- 2CO (2%)]
220 V/cm
GEM (triple stage)
CERN Standard
transfer gaps 1.5 mm
induction gap 1.0 mm
1.17 (1.27) mm×6 (6.3) mm
staggered
TDR
220 V/cm
Ar – methane (5%)
100 V/cm
MicroMEGAS
50-μm mesh
50-μm gap
2 (2.3) mm×6 (6.3) mm
Ar - isobutane (5%)
220 V/cm