1 / 40

Further studies on straw drift tubes for the PANDA Forward Tracker

Further studies on straw drift tubes for the PANDA Forward Tracker. A.Kashchuk ( anatoli.kachtchouk@cern.ch ). Contents. On electrical connection to cathodes Straw drift tube counting characteristics Gas gain vs. V and vs. P Electrical cross-talks (X-talks)

lacy-reynolds
Download Presentation

Further studies on straw drift tubes for the PANDA Forward Tracker

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Further studies on straw drift tubes for the PANDA Forward Tracker A.Kashchuk (anatoli.kachtchouk@cern.ch) A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

  2. Contents • On electrical connection to cathodes • Straw drift tube counting characteristics • Gas gain vs. V and vs. P • Electrical cross-talks (X-talks) • Common impedance cross-talks (Z-talks) • HV-plateau for MIP measured with Cosmics A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

  3. Schematic view of the straw drift tube with 2 springs ‘a la COSY-TOF’ providing electrical contact to Cathode Anode wire Far-end Near-end FEE- printed circuit board Elegant light-weight solution, What quality of the electrical contact ? Aging ? What inductance ? What other problems ? But A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

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

  5. New measurements on 75-cm straw tubes Mylar tubes with wall thickness 30µm Anode wire diameter 20µmCathode diameter 10mm with metal thickness 300Å=30nm External layer with metal thickness 300Å=30nmGas mixture Ar(90%)/CO2(10%) P=2000mb absolute at V=1550V Problem It seems (as shown below), a sagitta is an intrinsic feature of the straw tube with 2 springs and even one (!) A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

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

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

  8. Calculations by Vito Carassiti Load Reaction Force Bending Momentum A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

  9. Counting characteristics without springs on X-rays Fe-55 Copper straw #003 ~430V Note: Difference in counts on plateau are due to distance variations from the source to straw A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

  10. Counting characteristics without springs on X-rays Fe-55 Aluminum straw #004 ~460V Note: Difference in counts on plateau are due to distance variations from the source to straw A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

  11. 4 characteristic regions ? 4 3 2 1 ElectronicsThreshold A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

  12. Variations of the gas composition Pure Ar – the lowest electron drift velocity, but no quenching without CO2 Ar/CO2(10%) 450V 600V ×7 CO2(100%) A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

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

  14. Gas gain vs. V and vs. P A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

  15. Compare spectra with/without springs HV=1600V at P=1000mb (2000mb absolute) Fe-55 5.9keV Fe-55 5.9keV FWHM=15% FWHM=25% 3keV 3keV With spring Without spring A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

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

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

  18. Needed gas gain Note1: If ENC=3000e Thmin=18000e=>4p.e. (~4% inefficiency) Then needed gas gain Gmin=38000 ln(G)=10.5 Using Diethorn’s fit HVmin~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 HVmin~1420V HVmin~1550V and more to have better time-space resolution A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

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

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

  21. Absolute pressure in range of 1500-2000 mb has to be better studied to find optimum in terms of ‘efficiency-space resolution’ at high rates A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

  22. Cross-talks measurements A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

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

  24. Electrical cross-talks (X-talks) between 2 straws below 10-3 for X-rays Fe-55 N1, N2 Does not depend connected to ground or not (see w/o) the external layer AND 0.1%-level A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

  25. Above 1500V: Z-talks can reach 100% Electrical cross-talks are masked by Z-talks above 1500V log10 scale N1, N2 AND A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

  26. Cross-talks in straw tube detectors by schematics Electrical coupling (X-talks) Resonance Common impedance (Z-talks) Solution A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

  27. Cross-talks grow exponentially with reduction of threshold (increasing gas gain) A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

  28. Electrical cross-talks vs. threshold(HV=1450V) log(1500)=3.17 Fe-55 count 1500Hz (extrapolation) Offset ch#2=959mV (CARIOCA_hot 13mV/fC) Offset ch#1=963mV (CARIOCA_hot 11mV/fC) Th=1fC Note: offset subtracted A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

  29. Z-talks vs. thresholdThe lines become more and more horizontal with increasing HV log(1500)=3.17 Fe-55 count 1500Hz (extrapolation) Offset ch#2=957mV (CARIOCA_hot 13mV/fC) Offset ch#1=965mV (CARIOCA_hot 11mV/fC) Th=4fC at same gas gain will correspond to 12 p.e. (12% inefficiency) Note: offset subtracted A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

  30. What means this rise in counting rate vs. V ? ? A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

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

  32. First hit counting shows HV-plateau extension by 150-200V then discharge region and Rather limit A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

  33. Fe-55 Cu #003 ‘pro’=dead time prolongation (1-st hit counting) 150-200V Discharge limit ~1850V ~600V Raether limit ~2×107 e HVop>1550V A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

  34. Fe-55 Al #004 ‘pro’=dead time prolongation (1-st hit counting) 150-200V Discharge limit ~1820V ~600V HVop~1550V Raether limit ~2×107 e A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

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

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

  37. HV-plateau for MIP measured on cosmic muons Sc. counter Note: Count collected during ~17mn/point 3000 events on plateau per 24 hours for tracking Straw 1 Straw 2 A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

  38. 3-AND:HV-plateau for MIPStraw 1 triggered by Scint.Counter at HV=1400V on straw 2and wise versa Note: 1- Missing ~200V due to lower primary Ionization 2- HV-plateau for MIP continue up to discharge limit 3- Z-talks region 1 2 Missing MIP~400V Z-talks can and must be suppressed 3 Z-talks region HVop>1550V A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

  39. 3-ANDatHV=0 Straw 1 triggered by Scint.Counter at HV=0 on straw 2and wise versa Z-talks on MIPshifted on150-200Vw.r.t. Fe-55due to lower primary ionization Z-talks Hvop>1550V A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

  40. Conclusion • We try to avoid the springs in further design • As we hope, Z-talks will be suppressed at proper design of the Forward Tracker prototype on the next step • Pressure, gas gain and threshold have to be optimized with simulation • Gas gain has to be stabilized in working point to have no influence of atmospheric pressure variations to efficiency and space resolution • Final choice of operational parameters will be done after efficiency and space resolution measurements A.Kashchuk INFN-Ferrara and PNPI-St.Petersburg

More Related