Tracking in a TPCTracking in a TPCD. Karlen / U. Victoria & TRIUMF

for the LCTPC collaboration

Oct 24, 2007 D. Karlen/Tracking in a TPC 2

TPC trackingTPC trackingTime Projection Chambers have performed well as the main tracker in a wide range of physics experiments & environments• eg. underground, LEP, heavy ion collisions

RDR IV-74

Oct 24, 2007 D. Karlen/Tracking in a TPC 3

TPC trackingTPC trackingIs a TPC tracker suitable for the environment and physics at the ILC?• ie. will operate well and not compromise the

physics potential of the ILC?

A growing worldwide community has been active for many years to answer this question• we must have a definitive answer before the

ILC lab is ready to approve detector construction

Oct 24, 2007 D. Karlen/Tracking in a TPC 4

Key physics issuesKey physics issuesMomentum resolution• recoil mass (HZ0)• μμγ lumi spectrum

Pattern recognition

Low mass• preserve good jet energy resolution

Oct 24, 2007 D. Karlen/Tracking in a TPC 5

Key environmental issuesKey environmental issuesBeam structure

• TPC integration time: O(100) BX• low duty factor – pulsed electronics

Machine backgrounds• will additional occupancy break pattern

recognition?• will TPC suffer HV incidents?

Magnetic field non-uniformities• can corrections recover momentum resolution?

Oct 24, 2007 D. Karlen/Tracking in a TPC 6

TPC R&D programTPC R&D programThe ILC TPC R&D program began by tackling the momentum resolution question early this decade• It was quickly realized

that to achieve theresolution goals, thegas amplification systemmust be miniaturized

• Natural application formicro pattern gas detectors

GEM

Micromegas

Oct 24, 2007 D. Karlen/Tracking in a TPC 7

Momentum resolutionMomentum resolutionSpatial resolution• several small prototypes

constructed by groupsaround the world

15-60 cm drift5-15 mm2 padsB=0-5 T

• spatial resolutiontargets achieved forlarge B (100 μm orbetter per pad row)

• reported at previousmeetings

Oct 24, 2007 D. Karlen/Tracking in a TPC 8

New developmentsNew developmentsVery fine segmentation is possible with silicon sensors readout (medipix / timepix)• 55 μm × 55 μm pixels detect signals from

individual primary ionization electrons• possible improvement in dE/dx resolution

Integrated amplification stage, with spark protection:• with 20 μm

resistive layer,silicon survivesbreakdowns now

J. Timmermans, Nikkef

Oct 24, 2007 D. Karlen/Tracking in a TPC 9

TimepixTimepix eventseventsLike a miniature bubble chamber

cosmics (time mode) alphas (amplitude mode)

14 mm

Oct 24, 2007 D. Karlen/Tracking in a TPC 10

PixilizedPixilized readoutreadoutFor the GEM+pixel option, the diffusion after gain spreads the charge over many pixels. Larger pixels would allow lower gain in the amplification stage• developments

underway toincrease pixelsize – usefulfor GEM+pixeloption

before after

Post processing on a single chip

55x5555x55µµmm22 110x110110x110µµmm22

Oct 24, 2007 D. Karlen/Tracking in a TPC 11

…… beyond spatial resolutionbeyond spatial resolutionMost of the other issues need larger scale hardware & software efforts to address• LCTPC group developing into a formal

collaboration

Oct 24, 2007 D. Karlen/Tracking in a TPC 12

LCTPC goalsLCTPC goalsBuild a large prototype TPC for test beams and cosmic ray operation in a magnet• tiled endplate• interchangeable modules using different

amplification technologies• high density electronics developments• EUDET program provides much of the

necessary infrastructure

Build software suite suitable for simulation and reconstruction:• for use with prototype data (test beam and

cosmics) and full size TPC with ILC events

Oct 24, 2007 D. Karlen/Tracking in a TPC 13

Oct 24, 2007 D. Karlen/Tracking in a TPC 14

Oct 24, 2007 D. Karlen/Tracking in a TPC 15

Oct 24, 2007 D. Karlen/Tracking in a TPC 16

Field cage designField cage design

R. Diener

Oct 24, 2007 D. Karlen/Tracking in a TPC 17

Field cageField cageTight tolerances

Oct 24, 2007 D. Karlen/Tracking in a TPC 18

Oct 24, 2007 D. Karlen/Tracking in a TPC 19

Populated endplatePopulated endplate

Oct 24, 2007 D. Karlen/Tracking in a TPC 20

Readout designsReadout designs

GEM module (no side frames)A. Ishikawa

Bulk micromegasP. Colas

PixelreadoutM. Killenberg

Oct 24, 2007 D. Karlen/Tracking in a TPC 21

GatingGatingGating can reduce thenumber ions produced in the amplification stage.

Wire gating GEM gating

Gate Open

Gate Closed

A. Ishikawa

~50cm

μ

50mm/μsec

• gating can bedone with wiresor a GEMoperated atunit gain

Oct 24, 2007 D. Karlen/Tracking in a TPC 22

Power pulsingPower pulsingPower supplies designed for average power rather than peak powerDistributed charge storage capacitors close to the switchable loads supply the peak current. Allow ~ 1 volt drop during power on cycleLocal « Low dropout » voltage regulators keep voltage stable on the electronics

Properly controlled constant current sources recharge the capacitors between cycles

J.P. Martin (U. Montreal)

Oct 24, 2007 D. Karlen/Tracking in a TPC 23

Software developmentSoftware development

M. Killenberg U. Bonn

Oct 24, 2007 D. Karlen/Tracking in a TPC 24

ScorecardScorecardSpatial resolution – establishedPattern recognition – to start again• full pad readout simulation / reconstruction

Low mass – underway• field cage designs / electronics considerations

Beam structure – not demonstrated• tests at FNAL foreseen

Beam backgrounds – not demonstratedMagnetic field non-uniformities – starting• software development, large prototype tests

Oct 24, 2007 D. Karlen/Tracking in a TPC 25

SummarySummaryA worldwide team of people are working together towards the common goal of developing a TPC design that will satisfy the needs of the ILC physics programThe more challenging issues requiring large hardware and software investments are just getting underwayPlenty of room for new collaborators and new ideas!