08 September 2009 A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg 1 A.Kashchuk ([email protected])[email protected]

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


Documents

08 September 2009 A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg 1 A.Kashchuk ([email protected])[email protected]