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

08 September 2009 A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg 2

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 20093A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg But

Gas gain uniformity along straw 08 September 2009 A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg 4 Wire eccentricity or sagitta increases gas gain 20% (presented in Torino meeting) Fe-55 scanner 1%

New measurements on 75-cm straw tubes 08 September 2009 A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg 5 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 30µm Anode wire diameter 20µm Cathode diameter 10mm with metal thickness 300Å=30nm External layer with metal thickness 300Å=30nm Gas mixture Ar(90%)/CO2(10%) P=2000mb absolute at V=1550V

No sagitta without spring No puzzles anymore Measurements become reproducible, etc. 08 September 2009 A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg 6

30%-sagitta simulated by force 8.7g applied to the far-end 08 September 2009 A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg 7 F

Calculations by Vito Carassiti LOAD (N)DISPLACEMENT (mm) REACTION (N) K (N/mm) E E E E E September 2009A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg 8 Load Reaction Force Bending Momentum

Counting characteristics without springs on X-rays Fe-55 Copper straw # September 2009 A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg 9 ~430V Note: Difference in counts on plateau are due to distance variations from the source to straw

Counting characteristics without springs on X-rays Fe-55 Aluminum straw # September 2009 A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg 10 ~460V Note: Difference in counts on plateau are due to distance variations from the source to straw

4 characteristic regions 08 September 2009A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg ? Electronics Threshold

Variations of the gas composition 08 September 2009A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg12 CO2(100%) ×7 Ar/CO2(10%) Pure Ar – the lowest electron drift velocity, but no quenching without CO2 450V600V

08 September 2009A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg13 Ar(90%)CO2(10%) Electron drift velocity ~ 40µm/ns – the upper limit to get needed space resolution Note: Atlas MDT Ar(93)CO2(7%) at 3bar No aging High rate effect (!) Baseline mixture

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Compare spectra with/without springs HV=1600V at P=1000mb (2000mb absolute) 08 September 2009 A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg 15 Fe keV 3keV Fe keV 3keV FWHM=15%FWHM=25%

Gas gain measured vs. HV by peak position of 5.9keV (Fe-55) 08 September 2009 A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg 16 Assuming 17% charge collection by the FE-amplifier at P=2000mb absolute and T=295K 5.9keV

Gas gain vs. P at HV=1550V 08 September 2009 A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg 17 Note: Electron drift velocity is proportional to ratio E/P bad (!) P reduction increases velocity reducing spatial resolution – bad (!)

Needed gas gain 08 September 2009 A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg 18 Note1: If ENC=3000e Th min =18000e=>4p.e. (~4% inefficiency) Then needed gas gain G min =38000 ln(G)=10.5 Using Diethorn’s fit HV min ~1550V HV min ~1420V HV min ~1550V Note2: Either HV or overpressure can be used for gas gain stabilization G(E/p)=const to compensate atmospheric pressure variations and keep constant efficiency and space resolution and more to have better time-space resolution

Compare HV-plateau at overpressure 500mb and 1000mb 08 September 2009 A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg 19 ~460V ~420V

08 September 2009 A.Kashchuk INFN-Ferrara and PNPI- St.Petersburg 20 Good gas gain uniformity along straw Good Fe-55 spectra and HV-plateau At P=500mb (1500mb absolute) 1550V

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The technique 08 September 2009A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg23 Fe-55 creates the signal in only one straw: N1, N2 counts N1, N2 Cross-talk, if the signal appears in both straws: Fe-55N1N2 AND AND/(N1+N2)

Electrical cross-talks (X-talks) between 2 straws below for X-rays Fe September 2009A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg24 0.1%-level AND N1, N2 Does not depend connected to ground or not (see w/o) the external layer

08 September 2009A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg25 log 10 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 08 September 2009A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg26 Common impedance (Z-talks) Resonance Solution Electrical coupling (X-talks)

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Electrical cross-talks vs. threshold (HV=1450V) 08 September 2009A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg28 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. threshold The lines become more and more horizontal with increasing HV 08 September 2009A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg29 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

08 September 2009A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg30 ?

Count multiplication seen by scope HV=1750V: Direct signal from CARIOCA – blue; First hit - red 08 September 2009A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg31

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Fe-55 Cu # September 2009A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg33 ~600V V Discharge limit ~1850V ‘pro’=dead time prolongation (1-st hit counting) HV op >1550V Raether limit ~2×10 7 e

Fe-55 Al # September 2009A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg34 ~600V V Discharge limit ~1820V ‘pro’=dead time prolongation (1-st hit counting) HV op ~1550V Raether limit ~2×10 7 e

Inductance in common ground creates ringing on the FEE-input resulting multiple count on output 08 September 2009 A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg 35 Z-talks Countratio Fe-55 Z-talks Z-talks Streamers t t

Streamers also create multiple pulses but longer 08 September 2009A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg36 HV=1820V: Direct signal from CARIOCA – blue; First hit - red

08 September 2009A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg37 Sc. counter Straw 1 Straw 2 Note: Count collected during ~17mn/point 3000 events on plateau per 24 hours for tracking

08 September 2009A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg38 HV op >1550V MIP~400V Z-talks region Z-talks can and must be suppressed Missing 12 3 Note: Missing ~200V due to lower primary Ionization 2 - HV-plateau for MIP continue up to discharge limit Z-talks region

08 September 2009A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg 39 Z-talks Hv op >1550V

08 September 2009A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg40