TPC status

Marian Ivanov

Outlook

TPC performance ExB correction Alignment Nonlinearities and edge effects Drift velocity calibration

TPC - report June (2008)

TPC - DCA resolution

TPC resolution for fully

aligned and calibrated TPC

The systematic effect Dash line – full

miscalibration Full line Day 0

Expected Day 0 mis-

calibration on the level

comparable to intrinsic TPC

resolution up to 3 GeV

Day 0: z ~ 1mm

y ~ 0.3 mm

Full mis-calibration z ~ 5 cm

y ~ 3 mm

TPC - DCA resolution - rphi - Cosmic

TPC local y resolution for aligned

and calibrated TPC Status – 09.09.08 Rectangle A side, triangle C side

Sigma – fitter sigma of residuals

between tracks from upper part and

lover part In case the error uncorrelated to

be divided by sqrt(2.)

Systematic effects estimate A side +-0.1 cm C side +-0.3 cm

TPC - DCA resolution - z - Cosmic

TPC local z resolution for aligned

and calibrated TPC Status – 09.09.08 Rectangle A side, triangle C

side

Sigma – fitter sigma of residuals

between tracks from upper part

and lover part In case the error uncorrelated

to be divided by sqrt(2.)

Tracks crossing CE ~ 0.3 cm

TPC - curvature resolution

Day 0: C ~ 0.001 1/GeV

Full mis-calibration C ~ 0.01 (1/GeV) TPC resolution for fully

aligned and calibrated TPC

The systematic effect Dash line – full

miscalibration (mainly

ExB) Full line Day 0

Expected Day 0 mis-

calibration on the level order

of magnitude bellow intrinsic

resolution

TPC – 1/pt resolution - Cosmic

TPC 1/pt resolution for aligned

and calibrated TPC Status – 09.09.08 Rectangle A side, triangle C

side

Sigma – fitter sigma of residuals

between tracks from upper part

and lover part In case the error uncorrelated

to be divided by sqrt(2.)

Laser beam 1-3-3-3 example

Delta rfi and delta fi (direction vector) as function of the magnetic field

The interpolated value to field 0 – removed later from

the ExB global fit – assumed misalignment error

ExB correction – Taylor expansion

Left side - ExB correction – Taylor expansion Ltr.fP[1]/250 – normalized z position – (z^3-1) and (z-1) Ltr.fP[2] – local inclination angle – sin(fi) and cos(fi) bz – magnetic field

Different color for different fi laser positions

ExB correction

Left side - ExB correction versus measurement

Right side – residuals

Implemented ExB correction map – good agreement of correction factor

for symmetrized magnetic field map (after adjustment of omega-tau

factor)

Alignment and Non-linearities

Alignment coefficients Study of the cosmic production

5000000 events with magnetic field 5T

Y, Z misalignment on the level of 150-200 microns Correction for un-linearities necessary

Combine with Central electron plane study Combine with laser tracks

Alignment - y

Residuals between tracklets from inner and outer sectors

sigma ~ 150 microns – shift ~ 260 microns

Alignment - z

Residuals between tracklets from inner and outer sectors sigma ~ 220 microns – shift ~ 0.5 mm (distance to wire)

Alignment - phi

Residuals between tracklets from inner and outer sectors sigma ~ 0.38 mrad – shift ~ 0.2 mrad

Alignment - theta

Residuals between tracklets from inner and outer sectors sigma ~ 0.7 mrad – shift ~ 0.7 mrad

Laser scan – Non-linearities and Edge effect

Laser beams emitted from

the sector boundaries in

OROC to sector

boundaries in IROC ==> Difficult to disentangle

edge effect in r (local x)

and in r-phi )local y Work in progress

Non-linearities study using laser tracks - Parameters to monitor

The fitted curvature – global effect – (Parabola fit) Edge effect

Non-linearities - Gate/skirt voltage scan – Tuning of operational conditions

The step +-20 V, drift voltage (400 V/cm)=>Effective shift 0.05cm – comparable to missalignemnt

Edge effect -Outer sectors

Residuals between clusters y position and the linear extrapolation as function of the distance to the chamber edge Left (50 V setting) – Right (90 V setting)

Edge gain calibration / results

Fit function: f(x) = 1 - exp(-[0]*(x-[1]))

Edge effect - Inner sectors

Residuals between clusters y position and the linear extrapolation as function of the distance to the chamber edge Left (50 V setting) – Right (90 V setting)

Parabolic term Y – Nominal voltage (70 V GG)

Parabolic distortion from ideal line ~ 300 microns The track position resolution ~ 150 microns for infinite pt tracks

Inclination angle dependent

dY (cm)

Parabolic term Z – Nominal voltage (70 V GG)

Parabolic distortion form ideal line ~ 300 microns Inclination angle dependent

dZ (cm)

dZ (cm):z (cm)

Z position calibration,Drift velocity and

alignment

Drift velocity – calibration strategy Options:

Goofie calibration + DCS values (T, P) - (ONLINE) Time dependence (Goofie) - to be corrected for the T and P at

TPC Space dependence DCS values (T,P) – linear fit Relative precision 0.05% (1 mm at vertex)

Laser Central electrode - (ONLINE) Space and time dependence of drift velocity Relative precision ~ 0.01 cm/250cm ~ 0.004 %

Calibration using tracks – (OFFLINE) Track crossing central electrode Reconstructed primary vertex position using the tracks from A

and C side of the TPC Relative precision ~ 2 mm / sqrt(Nevents)

Drift calibration using laser tracks

Histogram of the fitted correction parameters – Delta z offset, and the drift velocity correction

Drift calibration using laser tracks - stability

Graph of the fitted correction parameters – Delta z offset, and the drift velocity correction

For some runs offset splitted by (shift by +- 0.5 time bin) – Similar effect in CE studiies

Drift calibration using laser tracks

Histogram of the fitted correction parameters – global y correction up-middle at CE position

Drift calibration - P/T

The drift velocity depends in gas density N/V ~ P/T The relative change of the P ~ 2 %, in temperature ~

0.1 K /293 K ~ 10^-4

Drift calibration - P/T resolution

Relative resolution ~ 10^-5 – 10^-4 => 250 microns

Day-night variation (TOF switching ON/OFF) Depends

Drift correction Laser - P/T correction

The drift velocity correction as function of time The drift velocity correction versus P/T relative

change

Drift correction Cosmic - P/T correction

The delta Z (cm) (A-C side) form cosmic as function of time

Red color – SPD trigger, Black – ACORDE

Delta z as function of the normalized P/T

Drift velocity - Open points

The time 0 offset – trigger dependent The current implementation – only one L1 delay Array of L1 delays (for trigger types) to be added

P/T correction ~ 200-300 microns precision The gas composition change in time

Information from the GOOFIE not (yet) reliable Necessary to refit the v drift versus P/T run by run

(optimally only offset) Vd ~ Vdnom*corr(P/T)*corr(GC)

ROC temperatures

Skirt temperatures

Drift calibration - CE

CE arrival time (in mm) as function of the global y Smaller effect as before – Smaller temperature gradient Some non-linearities visible

Drift calibration - CE

CE arrival time (in mm) as function of the global lx (after global y subtraction)

Drift calibration - CE

CE arrival time (in mm) as function of the pad phi position (after global y and local x subtraction)

Used as time 0 correction – z alignment in the current reconstruction

- the status of overlaps in the case of ideal, residual and full

misalignment ; - the status of survey, in particular the availability of alignment objects

generated from survey and if they have been tested (e.g. they are reliable

enough to be loaded into the OCDB for official use) ... and concerning

this I think you have only the alignment for the full TPC, which has

already been loaded into OCDBs.