Drift Chambers and Pattern recognisationDrift Chambers and Pattern recognisation

Fabrizio CeiFabrizio Cei Pattern recognition ideas Pattern recognition ideas INFN & Pisa UniversityINFN & Pisa University

Hajime NishiguchiHajime Nishiguchi Kapton foils for DC cathodeKapton foils for DC cathodeUniversity of TokyoUniversity of Tokyo

Johny EggerJohny Egger DC status and testsDC status and testsPSIPSI

DC Status and Tests

• Hood and inner cathodes

• Print foils

• M1 test– Drift time measurement– Cathode read out

• Next future

Cathode hood

Delivery and first tests:

second half of July

Inner cathodes

- measurement of deformation with applied forces

- simulate forces (level arm) with wires through the gas holes

- eventually stabilize free edges with tiny foam support(rohacell)

Print foils

Good results of M1 tests

possible foil pattern deformations

hood-foil tests with mounting tool

Inner cathode foil mounting test

Final design of the foil pattern

Ordering

if all requests are satisfied by the manufactory

H. H. NishiguchiNishiguchiKapton foils for DC cathodesKapton foils for DC cathodes

RequirementsRequirements

Low-MassLow-Mass: reduce resolution deterioration due to : reduce resolution deterioration due to multiple scatteringmultiple scattering

Kapton film 12.5 Kapton film 12.5 µm µm thick;thick;Aluminum deposition 50 nm thick (NOT copper !! )Aluminum deposition 50 nm thick (NOT copper !! )

AccuracyAccuracy: precise position reconstruction with vernier : precise position reconstruction with vernier pad method requires pad method requires manufacture accuracy ~ ±20 manufacture accuracy ~ ±20 µmµm and and deposition deposition byby “Etching”. “Etching”.

SituationSituation

Sample foils Sample foils withwith 3 Japanese companies3 Japanese companies suffered suffered

fromfrom many problemsmany problems, , butbut a sample foil which a sample foil which

satisfies satisfies all requestsall requests (except cost) (except cost) was builtwas built. .

ContactsContacts with with european factorieseuropean factories under way from under way from

PSI group. PSI group.

M1 test

with the 4 test chambers

Anode 1, 2

plan 0 to 4

digital Scope

8 channels

500 MHz

500 points, 8 bits

Cathodes of anode 2

plan 2,3

FLASH ADC

8 channels

100 MHz

500 points, 8 bits

24 Cathodes

Anode 1,(2,3)

LRS ADC

24 double channels

Anode 3

plan 0 to 4

AD811

Read out

Not staggered Parallel beam + tilted chambers

= .21 ns1.00 & .60 Tesla

P= 158 & 258 MeV/c

parallel < 1 %

No Field

P= 158 & 258 MeV/c

DC tilted by 1

DC tilted by 2

Behavior of amplifiers in the 1 Tesla magnetic field

-no measurable difference on induced test pulses

- time definition : t = .12 ns ( = .8 ns)

- pulse integral : I < .04 % ( = .16 % )

-no measurable effect in the magnetic field even with magnetic SMD capacitors and resistances ( contacts)

- approximate the field distortion with the new „non magnetic“ SMD elements, cables, connectors

Subtract y = b1 + b2*(sin[w*(t-t0)]): fit of the 225 first points

M1 run : w = 2* 50 MHz

Look for the first n=4,5 adjacent points above threshold

Linear fit of first n signal points and n last background points (=0)

Drift time

threshold

Drift time(Fit-measured time) against drifttime

t3 against t0

Sqrt( (Fit-measured time)2 ) = > 2.0 ns 2.8 ns(~.1 mm)

1.0 ns < (Fit-measured time) < 2.1 ns

Difference between 2 colors in t1 shows misalignment of anode w2p1 of ~.1 mm

u1 u2

d1 d2

Cathode readout

d1+d2 d1-d2

u1-u2u1+u2

Anode has a shielding effect of a few percents

Cathode u1 = n1*Anode * (1+c2 * sin[c3*x] + * c2* sin2 [c3*x])

Cathode u2 = n2 *Anode * (1-c2 * sin[c3*x] - * c2*sin2 [c3*x])

Cathode d1 = n3 *Anode * (1+c2 * cos[c3*x] + * c2*cos2 [c3*x])

Cathode d2 = n4 *Anode * (1-c2 * cos[c3*x] - * c2*cos2 [c3*x])

value for traces on 1 side of the anode is the opposite of the value for traces on the other side

and the cathode normalization factors ni are correlated in the calibration procedure

Calibration procedure not yet optimal : distributions are not flat

0.34 mm < (Fit-measured value) < .60 mm

0.11 mm < (Fit-measured value) < .35 mm

June 27

July 8

Cross talks

a) to next plane < 1%

b) To adjacent anode: 1) small on integrals 2) important for timimg

c) to near cathode of adjacent anode: Important

Corrections to b) and c) well defined by measurement of events without signal on the adjacent anode

„Domino „ read out on all channels is important 1000 points, 500 MHz, 10 bits is ideal

Present and near future planePresent and near future plane

• Analysis of Analysis of M1 runM1 run (rich sample of data) (rich sample of data)

– Magnetic fieldMagnetic field

– Anode shielding, cross talkAnode shielding, cross talk

– Exotic events Exotic events

• TestsTests– FoilsFoils

– Amplifiers and printsAmplifiers and prints

– High ratesHigh rates

• OrderOrderinging– FoilsFoils

– Frames and printsFrames and prints

– Amplifiers and cablesAmplifiers and cables

• ConstructionConstruction

• Test with first elementsTest with first elements (maybe within this year)(maybe within this year)

Positron Tracker

2002 2003 2004 2005

Test MilestoneAssemblyDesign Manufactoring

Full Prototype

Medium PrototypeCharge division & Cosmics

FP FP

Full Detector (18 DC)

FabrizioFabrizio Ideas for pattern recognitionIdeas for pattern recognition

Pattern recognitionPattern recognitionproblem in MEG:problem in MEG:

DC integration DC integration timetime ~ 1 ~ 1 ssPositron ratePositron rate on drift on drift chamberschambers ~ 5 MHz~ 5 MHz

Some superimposed Some superimposed trackstracks in each DC in each DC readout. readout.

Two turnsTwo turns(a(a rather rather frequentfrequent case)case)

AssumptionsAssumptions

Chambers are formed by Chambers are formed by two independent sensitive elementstwo independent sensitive elements;;

From each of them a From each of them a three-dimensional information of the three-dimensional information of the

crossing pointcrossing point (“hit”)(“hit”) can be extracted can be extracted

DC signals were already analysedDC signals were already analysed up to this level up to this level

WiresWires andand signal formationsignal formation not simulatednot simulated. .

Strategy outlineStrategy outline

Define a Define a segmentsegment of track as of track as two pairs of hits two pairs of hits ((oror a pair and an isolated a pair and an isolated hithit)) withinwithin two adjacent chamberstwo adjacent chambers ((one wedge)one wedge);;

Perform Perform aa fastfast andand reliable estimationreliable estimation of the of the positron momentumpositron momentum associated to any segment;associated to any segment;

Look at Look at any couple of segments any couple of segments which havewhich have the same pair of hitsthe same pair of hits (or(or the same isolated hitthe same isolated hit)) as endas end (one segment) (one segment) and beginningand beginning (the other); (the other);

Select Select the couples of segmentsthe couples of segments having having compatible momentum compatible momentum componentscomponents and and total momentumtotal momentum;;

Within this sample, Within this sample, join the couples of segmentsjoin the couples of segments which satisfy the which satisfy the geometrical requirements for a good trackgeometrical requirements for a good track;;

Save Save all “tracks” all “tracks” formed by aformed by a minimum number of segments minimum number of segments ( (44 or or 55);); Absolute timing informationAbsolute timing information not usednot used (by now). (by now).

Not enough time for details; onlyNot enough time for details; only

Technique: Technique: principal component analysisprincipal component analysis in in quadratic approximationquadratic approximation::

j ij , i

z, y, xj , i

ii

z, y, xi z, y, xh h b h a p

to to determine determine aaii, b, bijij..

hhii = one of the three spatial coordinates of one hit. = one of the three spatial coordinates of one hit.

Sum Sum overover the hitsthe hits (3 or 4) (3 or 4) in one wedge associated to a segmentin one wedge associated to a segment..Training by Training by MC eventsMC events: sample of : sample of 5 x 105 x 1055 Michel positron tracks Michel positron tracks, , corresponding to ~ corresponding to ~ (1 (1 3) x 10 3) x 1044 tracks tracks in each wedgein each wedge. .

22 events

truez,y,xz,y,x ppMinimize:Minimize:

Fast momentum Fast momentum estimationestimation

Tracks with Tracks with 4 segments 4 segments

Total Total momentummomentum

ppzz

MeV 8180 ;0 ..p p

MeVMeV

ppzz

ppxxppyy

Black: true Black: true Red: estimatedRed: estimated

pp

N.B. N.B. This is This is NOTNOT a momentum a momentum reconstructionreconstruction.

Momentum reconstructionMomentum reconstruction in one in onesegment segment minus true valueminus true value

Linking segmentsLinking segmentsAny chamberAny chamber (except #1 and (except #1 and#17) is #17) is a part of two“wedges”a part of two“wedges”

we can we can link two segmentslink two segments in in adjacent wedgesadjacent wedges requiring that requiring that they have one common pointthey have one common point..

Further selections:Further selections: compatibility of compatibility of momentum momentum

vectorsvectors in adjacent segments; in adjacent segments; compatibility of compatibility of new segmentnew segment with with extrapolated trackextrapolated track..

Segments with the same starting point.

Example of reconstructed tracksExample of reconstructed tracks

Algorithm performancesAlgorithm performances

# of # of correctly reconstructed trackscorrectly reconstructed tracks EfficiencyEfficiency = = —————————————————————————————— # of # of generated tracksgenerated tracks

Mean number of Efficiency on Efficiency on

mixed tracks first turn second turn

None 1 98.2 98.5Poisson 5 95 98.4Fixed 5 95.8 98.1

Poisson 10 91 97.5Fixed 10 92.1 97.5

Mixing

Michel positronsMichel positrons in the solid anglein the solid angle covered by the covered by the spectrometer spectrometer or or isotropicallyisotropically over the whole detector; over the whole detector; no no significant differencessignificant differences; ; positron momentumpositron momentum > 30 MeV> 30 MeV;;

A “by-product”: A “by-product”: momentum estimationmomentum estimation

Not a momentum Not a momentum reconstructionreconstruction, , but a but a reasonable reasonable starting pointstarting point for for more refined tracking more refined tracking algorithms (like algorithms (like MINUITMINUIT). ).

ConclusionsConclusions Algorithm looks to work wellAlgorithm looks to work well; ; >> 95 % 95 % for 5 mixed tracks & for 5 mixed tracks & > 91 > 91

%% for 10; for 10; more efficient more efficient for for higher momentum trackshigher momentum tracks ( (encouraging encouraging !!).).

Performances be Performances be only slightlyonly slightly ((~ 1 %) ~ 1 %) affectedaffected by by worsening the worsening the z resolutionz resolution or or reversing the scanning directionreversing the scanning direction.. Technical note soonTechnical note soon. . SuggestionsSuggestions (to investigated): (to investigated): begin the search from begin the search from outermost radiioutermost radii & try to & try to recover isolated hitsrecover isolated hits. . Possible improvementsPossible improvements: :

perform a perform a cuts fine tuningcuts fine tuning;; follow follow all possible linksall possible links between segments; between segments; use use absolute timing informationabsolute timing information as as linking toollinking tool;; perform a perform a better track extrapolationbetter track extrapolation; ; include include random noiserandom noise;; insert insert signal propagationsignal propagation in the simulation code … in the simulation code …

M1 testsM1 tests withwith four test chambersfour test chambers and and various various

readoutreadout (digiscope 500 MHz, flash & other ADCs ..)(digiscope 500 MHz, flash & other ADCs ..)

= .21 ns

1.00 & .60 Tesla

P= 158 & 258 MeV/c

parallel < 1 %

No Field

P= 158 & 258 MeV/c

DC tilted by 1 DC tilted by 2

Trigger timing resolutionTrigger timing resolution

Measurement of Measurement of four DC timesfour DC times