fred hartjes 1 6 th rd51 collaboration workshop, bari (italy), october 9, 2010 gossip testbeam...

Fred Hartjes 16th RD51 collaboration workshop, Bari (Italy), October 9, 2010

Gossip testbeam August 12 – 22 , 2010

Maarten van Dijk

Martin Fransen

Harry van der Graaf

Fred Hartjes

Wilco Koppert

Sjoerd Nauta

Rolf Schön


Principle of GossipHigh granularity pixel chipCell pitch 55 – 60 μm in X and Y

Thinned to 50 – 100 μm (not for this testbeam experiment)

Detection medium: thin gas layer instead of bulk semiconductorDrift gap ~ 1 mm high

Signal (some 6 electrons) enhanced by gas avalanche from a gridGain 5000 - 10000

Scaled up 4x for better visibility

~1 mm

14 mm (256 columns)

14 mm (2

56 rows)

The Gossip project has been recently approved by

Atlas collaboration board as an R&D project

The Gossip project has been recently approved by

Atlas collaboration board as an R&D project


Gossip functioning

Pixel chip with integrated Micromegas (InGrid)

Drift gap height 1 mmGetting > 95% track detection efficiency

Often detecting individual electrons

Track segment characterized byCrossing point

Direction


Reconstructing track segment

Track characterized by , and the crossing point (X, Y) with the reference plane


Timepix as a pixel chip

TimePixDerived from MediPix (X-ray detection)

Matrix of 256 x 256 pixels

55 µm pitch

=> 14.08 x 14.08 mm2 sensitive area

Common clock (100 MHz) to measure drift time for each pixel

Also Time-Over-Threshold (TOT) mode to measure charge signal spectrum

Postprocessing 7 µm Si doped Si3N4 for spark protection

Amplification grid (InGrid) on TimePix

InGrid


Chamber gas: DME/CO2 50/50

DME/CO2 50/50o Very slow and “cool” gaso High drift field requiredo Very low diffusiono Suited for TPC

Drift fields used in Gossipso 2 kV/cm (lowest diffusion)o 6 kV/cm (Vd = 50 µm/ns)

o LHC tracking

Calculated diffusion () and drift velocity (Vd)of DME/CO2 50/50 vs electrical field (E)

E (V/cm)

0 2 4 6 8 10 12

( m

/cm

1/2 )

0

50

100

150

200

Vd ( m

/ns)

0

20

40

60

80

L

T

Vd


Aim of the Gossip testbeam experiment in August 2010

1. Gossip parametersPosition resolution

Angular resolution of track segment

Track detection efficiency

Dependence on gas gain

Double track separation

2. Characterisation of DME/CO2 50/50 mixturePrimary ionisation/cluster density

Drift velocity

Transverse diffusion

3. Cathode emissionPillarPix detector, NO drift gap

Detecting knock-off electrons from cathode surface

Cathode from three different materials: doped diamond; Cu; Al

~ 70 µm

19.3 mm

e-


Using Gossip/GridPix telescope as a reference

Measurements done with Gossip 2

Define track with Gossip 1 and 3

Reject bad events using the Gridpix detector (19.3 mm drift gap) Wrong angle (background tracks)

Outside fiducial volume

Multiple tracks (showers)

Gossip 1 Gossip 2 Gossip 3 Gridpix (DICE)

19.3 mm


Mechanical set-up in testbeam

1 m optical bench

4 Gridpix detectors

3 x Gossip

GridPix

2 Scintillators 15 x 15 mm

Mass flow controller and meter

Angular adjustment

Angular adjustment

Remotely adjustable by

CERN XSCA table

Remotely adjustable by

CERN XSCA table


Completely remotely controlled

Communication between barrack and experimental area by 2 Ethernet cables

Using Remote Desktop

KA

TA

LP

A


DAQ and servicesDAQ of TimePix chips by MUROS

4 TimePix chips daisy chained~ 10 Hz event rate during spill

Complete remote control ofGrid voltages

Field voltages

Gas flow

Logging (every minute) of All voltages

Gas flow

Temperature

Atmospheric pressure

AdvantageParameters may be modified during beam on

Experimental conditions of all measurements well known


Temperature during testbeam

Logged every minute during the testbeam period

Temperature in hall varying between 20.6 and 25.4 °C


Atmospheric pressure during testbeam

Varying between 961 and 968.5 mbar


We used a metal tray on

the floor, 90 x 130 cm,

surrounding the whole gas

system


Special requirements for flammable gas

Gas mixture from 120 l JSP gas bottle Prepared at Nikhef

Whole gas system including bottle contained in leak tray

Checking gas leaks by measuring deficit between input flow and exhaust flow

Connected to flammable gas exhaust line


LabView controlled gas systemOperationFlow logged each minute

Alarm at leak rate > 3 ml/min

Shut off at integrated leak volume of 30 ml

Gas flow set between 5 and 50 ml/minPossible calibration error by factory (flow too low)


Gas flow during August testbeamWhite: inlet gas steam

Red: exhaust gas stream

Adjusted between 50 ml/min (purge) and 5 ml/min (standby)


Data analysis of the August 2010 testbeam

Just started, still most to be done

Only preliminary results are given

Suffering from material of upstream experimentSeveral cm of aluminium, copper plates

Showers => many multiple track events

Nuisance, but shower events can be used to study double track separation


In total 60 runs containing ~250k events

Almost all done with DME/CO2 50/50 and 150 GeV muons

Last 4 runs with Ar/iC4H10 80/20

46k events

~3k of them were hadrons

run# start time start date # of eventsVg1 Vg2 Vg3 Vg4 Vf GossipsVguard Vf DICE a1 a2 a3 a4 gas Analysed?1 19:41 12-8 273 580 580 580 500 780 540 2000 45 0 45 45 DME/CO22 12-8 1696 580 580 580 500 780 540 2000 45 0 45 45 DME/CO23 12-8 654 580 580 580 500 780 540 2000 0 0 0 0 DME/CO24 13-8 1463 580 580 580 500 780 540 2000 0 0 0 0 DME/CO25 13-8 1023 580 580 580 500 780 540 2000 0 0 0 0 DME/CO2 from ev 322 tests beam tuning6 13-8 1024 600 600 600 530 800 630 4390 0 0 0 0 DME/CO2 X7 13-8 788 450 450 450 450 650 600 4310 45 45 45 45 DME/CO2 run in TOT mode8 13-8 1340 450 450 450 450 650 600 4310 45 45 45 45 DME/CO2 X9 13-8 773 450 450 450 450 650 600 4310 45 45 45 45 DME/CO210 13-8 714 470 470 470 470 670 620 4330 45 45 45 45 DME/CO2 run in TOT mode11 13-8 1026 470 470 470 470 670 620 4330 45 45 45 45 DME/CO2 X12 13-8 4026 470 470 470 470 670 620 4330 45 45 45 45 DME/CO213 14-8 770 490 490 490 490 690 640 4350 45 45 45 45 DME/CO2 repair timing + rot. DICE, TOT14 14-8 1022 490 490 490 490 690 640 4350 45 45 45 45 DME/CO2 X15 14-8 1017 490 490 490 490 690 640 4350 45 45 45 45 DME/CO216 14-8 741 510 510 510 510 710 660 4370 45 45 45 45 DME/CO2 run in TOT mode17 14-8 1612 510 510 510 510 710 660 4370 45 45 45 45 DME/CO2 X18 14:19 14-8 1388 510 510 510 510 710 660 4370 45 45 45 45 DME/CO2 peak at 90 ns hopefully cured19 14-8 530 530 530 520 730 670 4380 45 45 45 45 DME/CO2 run in TOT mode20 17:40 14-8 4362 530 530 530 520 730 670 4380 45 45 45 45 DME/CO2 X21 14-8 550 550 550 530 750 680 4390 45 45 45 45 DME/CO2 run in TOT mode22 20:28 14-8 2188 550 550 550 530 750 680 4390 45 45 45 45 DME/CO2 X23 14-8 570 570 570 530 770 680 4390 45 45 45 45 DME/CO2 run in TOT mode24 22:12 14-8 2059 570 570 570 530 770 680 4390 45 45 45 45 DME/CO2 X25 23:27 14-8 17728 590 590 590 530 790 680 4390 45 45 45 45 DME/CO2 X Run overnight until 8:06 26 10:32 15-8 339 590 590 590 530 790 680 4390 45 45 45 45 DME/CO2 run in TOT mode27 10:55 15-8 348 600 600 600 540 800 690 4440 45 45 45 45 DME/CO2 run in TOT mode28 12:19 15-8 2275 600 600 600 540 800 690 4440 45 45 45 45 DME/CO2 X29 14:52 15-8 2192 610 610 610 550 810 700 4450 45 45 45 45 DME/CO2 X30 15-8 824 610 610 610 550 810 700 4450 45 45 45 45 DME/CO2 run in TOT mode31 15-8 694 620 620 620 560 820 710 4420 45 45 45 45 DME/CO2 run in TOT mode32 19:40 15-8 2251 620 620 620 560 820 710 4420 45 45 45 45 DME/CO2 X33 15-8 2898 620 620 620 560 1220 710 4420 45 45 45 45 DME/CO2 X34 15-8 4270 620 620 620 560 1220 710 4420 10 45 10 10 DME/CO235 16-8 5839 620 620 620 560 820 710 4420 10 45 10 10 DME/CO2 DICE trip36 16-8 4015 620 620 620 560 820 710 4420 10 0 10 10 DME/CO2 X37 16-8 4596 620 620 620 560 1220 710 4420 10 0 10 10 DME/CO2 X38 16-8 4569 620 620 620 560 1220 710 4420 10 5.75 10 10 DME/CO2 X39 16-8 17919 620 620 620 560=> 550 820 710 4420 10 5.75 10 10 DME/CO2 DICE trip problems40 16-8? 4084 620 620 620 520 1220 670 4380 10 11.5 10 10 DME/CO2 DICE reduced after trips41 17-8 4306 620 620 620 530 820 680 4390 10 11.5 10 10 DME/CO2 broad beam, low intensity42 17-8 5001 620 620 620 540 820 690 4390? 10 23 10 10 DME/CO2 ~ 10x more particles43 17-8 5307 620 620 620 540 1220 690 4440 10 23 10 10 DME/CO244 17-8 30855 620 620 620 540 820 690 4440 0 0 0 90 DME/CO2 X45 18-8 6442 620 620 620 540 820 690 4440 0 0 0 90 DME/CO2 X gasflow to 65 ml/min46 18-8 7097 620 620 620 540 820 690 4440 0 0 0 90 DME/CO2 X lower thresh. DICE47 18-8 1940 620 620 620 540 820 690 4440 0 0 0 10 DME/CO2 Vf of pos2 at 0V48 19-8 9854 620 620 620 540 820 690 4440 0 45 0 10 DME/CO2 Vf of pos2 at 0V49 19-8 8358 620 620 620 540 820 690 4440 0 45 45 10 DME/CO2 Vf of pos2 at 0V50 11:44 20-8 4440 620 620 620 540 820 690 4440 45 45 45 0 DME/CO2 Vf of pos2 at 0V51 14:50 20-8 2410 620 0 620 540 820 690 4440 45 45 45 0 DME/CO2 PillarPix dead, P3 sparky52 16:26 20-8 292 620 0 620 540 820 690 4440 45 45 45 0 DME/CO2 Hadr.;SCXA:106;306=>092;36653 16:38 20-8 3832 620 0 620 540 820 690 4440 45 45 45 0 DME/CO2 Hadrons, no field on P3 and P254 18:07 20-8 2744 620 0 620 540 820 690 4440 45 45 45 0 DME/CO2 sheet missing55 11:27 21-8 3381 620 620 620 540 820 690 4440 0 0 0 10 DME/CO256 12:48 21-8 5314 620 620 620 540 570 450 3245 0 90 0 10 DME/CO2 SC2 5.5 to PC, SC1 2.5 oppos.57 18:19 21-8 634 420 420 420 350 570 450 3245 0 0 0 10 Ar/iC4H10 150 GeV hadrons58 18:32 21-8 4314 420 420 420 350 570 450 3245 0 0 0 10 Ar/iC4H10 Hadrons => muons59 19:50 21-8 34348 420 420 420 350 570 450 3245 0 0 0 10 Ar/iC4H1060 9:30 22-8 11804 420 420 420 350 570 450 3245 0 11.5 0 10 Ar/iC4H10

Run overview Gossip beam test August 2010


What has been measured?50k events for Gossip under 45°

Grid voltage scan from -510 to -620 V

Mostly at field 2 kV/cm

2.8 k events at 6 kV/cm

10k events under 4 other angles0; 5.75; 11.5 and 23°

Both at drift field of 2 and 6 kV/cm

25k events with secondary emission detector

44k events in GridPix under 90°

5k events with parallel tracks in Gossip

e-


Typical event in all 4 detectors (angle 10°)


Typical event in GridPix under 45°

Very small diffusion but big time slewing

From asideFrom aside From topFrom top


Comparing DME/CO2 to Ar/isobutane

DME/CO2 50/50DME/CO2 50/50 Ar/iC4H10 80/20Ar/iC4H10 80/20

Tracks under 10°

In Y directionIn Y direction In Y directionIn Y direction


DME/CO2 has big advantages wrt diffusion

DME/CO2 50/50DME/CO2 50/50 Ar/iC4H10 80/20Ar/iC4H10 80/20361run58_0.txt 35 um/ns434run55_3.txt 9.5 um/ns

In X directionIn X direction In X directionIn X direction


Data analysis

Cuts on each detector individually

Cuts on fitted tracksSlope

Intercept Z=0

Fit residue

Cuts on pixel hitsFiducial area

Maximum drift time


Drift time spectrum of a Gossip

Drift time spectrumVg = 530 V run 20

drift time (ns)

0 100 200 300 400 500

fre

que

ncy

0

100

200

300

400


drift time (ns)

0 100 200 300 400 500

fre

que

ncy

0

100

200

300

400


drift time (ns)

0 100 200 300 400 500

fre

que

ncy

0

100

200

300

400

500


drift time (ns)

0 100 200 300 400 500

freq

uenc

y

0

100

200

300

400

500

Vg = -530 V

-570 V

-600 V

-620 V

TimePix chip suffering from time slewing

Less dominant at high gain


Number of hits per track in Gossip vs grid voltageUnexpected difference between the three Gossips

If drift gap of Gossip 3 were 1.0 mm, then Gossip 4 =>1.13 mm and Gossip 2 => 0.84

=> not consistent with metrology (differences of 40 µm)

Number of hits per track vs grid voltage

Vgrid (V)

-620-600-580-560-540-520-500

# o

f hi

ts

0

2

4

6

8

10Gossip 2Gossip 3Gossip 4

Expected:• 6.4 clusters•12.5 electrons

Expected:• 6.4 clusters•12.5 electrons

Tracks under 45°Tracks under 45°


Jump caused by change in atmospheric pressure?

961 mbar at -600 V

964 mbar at -610 V

Would a higher gas density give higher gas gain??

Analysis of other data needed to confirm this

Vgr

id =

-60

0V

Vgr

id =

-61

0V

Vgr

id =

-62

0V

Vgrid = -590V


Jump caused by change in temperature?

~ 23 ° C at -600 V

~ 22.5 ° C at -610 V

23.3 ° C at -620 V

Would a higher gas density give higher gas gain??

Vgr

id =

-60

0V

Vgr

id =

-61

0V

Vgr

id =

-62

0V

Vgrid = -590V


Track detection efficiencyTracks selected by GridPix detector

Completely flat plateau from ~ -570 V on

Expected for 1.0 mm DME/CO2: 98.9%

Track detection efficiency vs grid voltage

Vgrid (V)

-620-600-580-560-540-520-500

Eff

icie

ncy

0.84

0.86

0.88

0.90

0.92

0.94

0.96

0.98

1.00

1.02

Expected for 1.0 mm gas gap

Gossip 2Gossip 3Gossip 4

Efficiency vs width of the drift gap

Gap width (mm)

0.7 0.8 0.9 1.0 1.1 1.2 1.3

Eff

icie

ncy

0.97

0.98

0.99

1.00


Concluding:Detectors operating well, but some results not understood

All Gossips were operating reliably without any HV problem at high gain

The older GridPix (mostly running at -560 V) had less good gain, but probably rather good single electron efficiency

Profited Infrastructure of remote control of HV and gasParameters may be modified when beam is on

Values permanently logged

We have collected data to determine position resolution and angular resolution for 5 difference angles of incidence

Gossips have excellent track detection efficiency (~ 99%) from -570 V on

Not yet understood:Jump in number of hits for Vgrid going from -600 V to -610 V

Difference in number of hits between Gossip 2, 3 and 4 (not consistent with metrology)

fred hartjes 1 6 th rd51 collaboration workshop, bari (italy), october 9, 2010 gossip testbeam...

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