further studies on straw drift tubes for the panda forward tracker

08 September 2009 A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg 1

A.Kashchuk([email protected])

mailto:[email protected]

Near-end FEE- printed circuit board

Anode wire

Schematic view of the straw drift tube with 2 springs ‘a la COSY-TOF’

providing electrical contact to Cathode

Far-end

Elegant light-weight solution,

What quality of the electrical contact ?Aging ?What inductance ?What other problems ?

08 September 2009 3A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

ButBut

Gas gain uniformity along straw


Wire eccentricity or sagittaincreases gas gain

20%

(presented in Torino meeting)

Fe-55 scanner

1%

New measurements on 75-cm straw tubes

y = -0.0562x2 + 2.4517x + 23.501

R2 = 0.9638

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30 35 40

Point number along straw (40cm, step 1cm)

Fe-

55 p

eak

po

siti

on

(m

V)

40%


It seems (as shown below),a sagitta is an intrinsic feature of the straw tube with 2 springs and even one (!)

Mylar tubes with wall thickness 30µmAnode wire diameter 20µmCathode diameter 10mm with metal thickness 300Å=30nmExternal layer with metal thickness 300Å=30nmGas mixture Ar(90%)/CO2(10%) P=2000mb absolute at V=1550V

No sagitta without spring No sagitta without spring No puzzles anymore No puzzles anymore

Measurements become reproducible, etc.Measurements become reproducible, etc.

0

10

20

30

40

50

60

70

80

90

100

110

120

0 5 10 15 20 25 30 35 40


Fe-

55 p

eak

po

siti

on

(m

V)

#003 Copper w/o spring

#004 Aluminum w/o spring

2%

2%


30%-sagitta simulated by force 8.7g applied to the far-end


F

Calculations by Vito Carassiti

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0 3.43E -01 0.686 1.71 5.14

Displa c e mnt (mm)

Lo

ad (

N)

LOAD (N) DISPLACEMENT (mm) REACTION (N) K (N/mm)

0 0 0 0

0.02 3.43E-01 0.05733 5.83E-02

0.04 0.686 0.11466 5.83E-02

0.1 1.71 0.28665 5.85E-02

0.3 5.14 0.86 5.84E-02


Load

Reaction Force

Bending MomentumBending Momentum

Counting characteristics without springs on X-rays Fe-55 Copper straw #003

0200400600800

1000120014001600180020002200240026002800300032003400

1050 1150 1250 1350 1450 1550 1650 1750

HV (V)

Co

un

t F

e-5

5 (

Hz)

Center #003 Fe-55 close to straw

16cm to near-end

16cm to far-end


~430V

Note:Difference in countson plateau are due to distance variations from the source to straw

Counting characteristics without springs on X-rays Fe-55 Aluminum straw #004

0200400600800

1000120014001600180020002200240026002800300032003400

1050 1150 1250 1350 1450 1550 1650 1750

HV (V)

Co

un

t F

e-5

5 (

Hz)

Al #004 center at Th=970mV

16cm to near-end

16cm to far-end


~460V

Note:Difference in countson plateau are due to distance variations from the source to straw

4 characteristic regions


1

23

4

?

ElectronicsThreshol

d

Variations of the gas composition


CO2(100%)CO2(100%)

×7×7

Ar/CO2(10%)Ar/CO2(10%)

Pure Ar – the lowest electron drift velocity, but no quenching without CO2

450V 600V


Ar(90%)CO2(10%)Electron drift velocity ~ 40µm/ns – the upper limit to get needed space resolution

Note: Atlas MDTAr(93)CO2(7%) at 3barNo agingHigh rate effect (!)

Baseline mixture


VEparametersfitsDiethorn

constRdensitygasT

p

R

radiicathodeanodeba

Eab

a

VG

a

bV

V

gas

,:'

)(1

,,

)(ln

min

ln

2ln

00min

Compare spectra with/without springs HV=1600V at P=1000mb (2000mb absolute)


Fe-555.9keV

3keV

Fe-555.9keV

3keV

FWHM=15%FWHM=15% FWHM=25%FWHM=25%

Gas gain measured vs. HVby peak position of 5.9keV (Fe-55)

7.2100 VdV

dG


Assuming 17% charge collection by the FE-amplifierat P=2000mb absolute and T=295K

5.9keV

50000)1600( VG

VVcm

kVE 32;20min

Gas gain vs. P at HV=1550V


%24100dp

dG

B

p

AG

Note: Electron drift velocity is proportional to ratio E/PP reduction increases velocity reducing spatial resolution – bad (!)bad (!)

Needed gas gain


Note1:IfENC=3000eThmin=18000e=>4p.e.(~4% inefficiency)

Then needed gas gainGmin=38000ln(G)=10.5

Using Diethorn’s fitHVmin~1550V

HVmin~1420V

HVmin~1550V

Note2:Either HV or overpressurecan be used for gas gain stabilizationG(E/p)=constto compensateatmospheric pressure variationsand keep constantefficiency and spaceresolution

and more to have better time-space resolution

Compare HV-plateau at overpressure 500mb and 1000mb

0200400600800

1000120014001600180020002200240026002800300032003400

1050 1150 1250 1350 1450 1550 1650 1750

HV (V)

Co

un

t F

e-5

5 (

Hz)

Al #004 center at P=1000mb,Th=970mVP=500mb, Th=970mV


~460V

~420V

08 September 2009A.Kashchuk INFN-Ferrara and PNPI-

St.Petersburg20

0102030405060708090

100110120130140150

0 5 10 15 20 25 30 35 40


Fe-

55 p

eak

po

siti

on

(m

V)

Mean=133.2StDev=1.25Ratio=0.94%

Good gas gain uniformity along straw

Good Fe-55 spectraand HV-plateau

At P=500mb (1500mb absolute)

1550V

The technique


Fe-55 creates the signal in only one straw: counts N1, N2 N1, N2 Cross-talk, if the signal appears in both straws:

Fe-55

N1N1 N2N2

ANDAND

AND/(N1+N2)AND/(N1+N2)

Electrical cross-talks (X-talks) between 2 straws below 10-3 for X-rays Fe-55

0500

1000150020002500300035004000

1100 1200 1300 1400

HV (V)

Fe-

55 c

ou

nt

(Hz)

#1 (Cu) #2 (Al) #1 w/o #2 w/o

0.0%

0.1%

1.0%

10.0%

100.0%

1100 1200 1300 1400

HV (V)

El.c

ross

-tal

ks (

%)

Cross-talks (%) w/o Next day


0.1%-level

AND

N1, N2

Does not dependconnected to groundor not (see w/o) the external layer

0

10

1000

1100 1200 1300 1400 1500 1600 1700

HV (V)

Fe-

55 c

ou

nt

(Hz)

#1 (Cu) #2 (Al) AND#1 w/o #2 w/o AND w/o#1 next #2 next AND next


log10 scale

Above 1500V: Z-talks can reach 100%Electrical cross-talks are masked by Z-talks above 1500V

AND

N1, N2

Cross-talks in straw tube detectors by schematics


Common impedance (Z-talks)Common impedance (Z-talks)

ResonanceResonance

SolutionSolution

Electrical coupling (X-talks)Electrical coupling (X-talks)

Electrical cross-talks vs. threshold(HV=1450V)

y = -0,31x + 3,18

y = -0,18x + 3,18

-1-0,5

00,5

11,5

22,5

33,5

0 5 10 15 20 25

log

(AN

D)

Th (mV)

#1 HV=0 #2 HV=1450V at Th-scan

#1 HV=1450V #2 HV=0 at Th-scan


Fe-55 count 1500Hz (extrapolation)

Offset ch#2=959mV (CARIOCA_hot 13mV/fC)

Offset ch#1=963mV(CARIOCA_hot 11mV/fC)

Note: offset subtracted Th=1fC

log(1500)=3.17

Z-talks vs. thresholdThe lines become more and more horizontal with increasing HV


Fe-55 count 1500Hz (extrapolation)

Offset ch#2=957mV (CARIOCA_hot 13mV/fC)

Offset ch#1=965mV(CARIOCA_hot 11mV/fC)

Note: offset subtracted Th=4fC at same gas gain will correspond to 12 p.e.(12% inefficiency)

log(1500)=3.17


?

Count multiplication seen by scope HV=1750V: Direct signal from CARIOCA – blue; First hit - red


Fe-55 Cu #003


~600V

150-200V

Dis

char

ge

lim

it ~

1850

VD

isch

arg

e li

mit

~18

50V

‘pro’=dead time prolongation(1-st hit counting)

HVop>1550VRaether limitRaether limit

~2×10~2×107 7 ee

Fe-55 Al #004


~600V

150-200V

Dis

char

ge

lim

it ~

1820

VD

isch

arg

e li

mit

~18

20V

‘pro’=dead time prolongation(1-st hit counting)

HVop~1550V Raether limitRaether limit~2×10~2×107 7 ee

Inductance in common ground creates ringing Inductance in common ground creates ringing on the FEE-input resulting multiple count on outputon the FEE-input resulting multiple count on output


Z-talksZ-talks

CountCountratioratio

Fe-55

Z-talksZ-talks

Z-talksZ-talks

Fe-55

Str

eam

ers

Str

eam

ers

tt

Streamers also create multiple pulses Streamers also create multiple pulses but longerbut longer


HV=1820V: Direct signal from CARIOCA – blue; First hit - red


Sc. counter

Straw 1

Straw 2

Note:Count collected during ~17mn/point3000 events on plateauper 24 hours for tracking


HVop>1550V

MIP~400V

Z-talks region

Z-talks can and must be

suppressed

Missing

11 22

33

Note:11 --Missing ~200Vdue tolower primaryIonization22 --HV-plateaufor MIPcontinue up todischarge limit33 --Z-talks region


Z-talks

Hvop>1550V

further studies on straw drift tubes for the panda forward tracker

Documents

kashchuk infnferrara

straw tubes

metal thickness

straw drift tube

wall thickness

cathode diameter

manode wire diameter

sagittaincreases gas