Gas issues for a Micromegas TPC for the Future Linear Collider

1. Gas issues for a Micromegas TPC for the Future Linear Collider David Attié D. Burke; P. Colas; E. Delagnes; Y. Giomataris; A. Giganon; M. Was Endplate Meeting – September 13, 2006 Endplate meeting – September 13, 2006

2. Introduction • Goal and description of the measurement campaign • Simulations with GARFIELD/MAGBOLTZ • Gain curves • The Penning effect with a Penning mixture gas • Resolution • Evaluation of the Townsend coefficients • Comparisons of measurements/simulations gains • Conclusion Endplate meeting – September 13, 2006

3. Gain measurements : description • Aims: • find gas mixture comfortable gain margin to use into a Micromegas TPC • verification of the Townsend coefficients • Description: • Using the same detector • Transparent plastic box of • 20 cm x 20cm x 6 cm size • “Standard” 50 mm mesh of • 10 cm x 10 cm size • Sources: • - Fe 55 (5.9 keV) • - COOL-X (8.1 keV) • Monitoring of: • - pressure • - H2O • Gas mixing system with • triple mixture available Endplate meeting – September 13, 2006

4. Gain measurements : description • Drift length : 13 mm • Distance drift grid-source ~ 45 mm • HV2-HV1 = constant (but gas dependant) Source Drift grid (HV2) Gas (OUT) Gas (IN) Mesh (HV1) Anode (E=0V) Endplate meeting – September 13, 2006

5. Gain measurements : simulation Drift Velocitiy Longitudinal diffusion Transversal diffusion Edrift = 220 V/cm Simulations from GARFIELD/MAGBOLTZ Endplate meeting – September 13, 2006

6. Gain measurements : simulation Choice : Edrift = 220 V/cm Simulations from GARFIELD/MAGBOLTZ Endplate meeting – September 13, 2006

7. Gain measurements : simulation Choice : Edrift = 300 V/cm Simulations from GARFIELD/MAGBOLTZ Endplate meeting – September 13, 2006

8. Gain measurements : simulation Longitudinal diffusion Drift Velocitiy Choice : Edrift = 500 V/cm Transversal diffusion Simulations from GARFIELD/MAGBOLTZ Endplate meeting – September 13, 2006

9. Gain measurements : spectrum 5,9 keV Counts Emesh = 72 kV.cm-1 RMS ~ 6,0 % 3 keV Energy (keV) Argon Isobutane : 5% (source : Fe55) Endplate meeting – September 13, 2006

10. Pressure monitoring in Saclay Endplate meeting – September 13, 2006

11. Gain curves summary Mixtures of gases containing argon Endplate meeting – September 13, 2006

12. Gain curves Mixtures of gases containing Argon and Isobutane Edrift = 220 V/cm Endplate meeting – September 13, 2006

13. Gain curves Mixtures of gases containing Argon, Isobutane and CF4 Edrift = 220 V/cm Endplate meeting – September 13, 2006

14. Gain curves Mixtures of gases containing Argon, Ethane Edrift = 100 V/cm Endplate meeting – September 13, 2006

15. Gain curves +3% +10 % Mixtures of gases containing Argon, Ethane and CF4 Edrift = 300 V/cm Endplate meeting – September 13, 2006

16. Gain curves Mixtures of gases containing Argon, Methane Edrift = 300 V/cm Endplate meeting – September 13, 2006

17. Gain curves Mixtures of gases containing Argon, Methane and CF4 Edrift = 300 V/cm (CH4) Edrift = 250 V/cm (CH4,CF4) Endplate meeting – September 13, 2006

18. Gain measurements : Penning Effect Ne/Argon – Iso 5% The Penning mixture is a mixture of inert gas with another gas, that has lower ionization voltage than either of its constituents Penning effect : The other gas has to have lower ionization potential than the first excited state of the noble gas. The excitation of the noble gas atoms is tranfered to the quencher gas molecules via collisions Endplate meeting – September 13, 2006

19. Gain measurements : Penning Effect Ne/Argon – Iso 5% Endplate meeting – September 13, 2006

20. Gain measurements : Penning Effect Ne/Argon – Iso 5% Endplate meeting – September 13, 2006

21. Penning effect • Possibilities of Penning mixtures: • Ne-Ar • Ar-Xe • Ar-Acetylene • Ne-Xe • Ar-impurities who have lower Ei ?! • … Endplate meeting – September 13, 2006

22. Gain measurements : Townsend coefficients N = N0×exp[a×d] With a = A×P×exp[-B×P/E] Argon-Isobutane Endplate meeting – September 13, 2006

23. Resolution Best RMS ~ 6 % Endplate meeting – September 13, 2006

24. Gain measurements : comparison with simulations Simulations from GARFIELD/MAGBOLTZ Endplate meeting – September 13, 2006

25. Gain measurements : comparison with simulations Simulations from GARFIELD/MAGBOLTZ Endplate meeting – September 13, 2006

26. Gain measurements : comparison with simulations Simulations from GARFIELD/MAGBOLTZ Endplate meeting – September 13, 2006

27. Gain measurements : comparison with simulations Simulations from GARFIELD/MAGBOLTZ Endplate meeting – September 13, 2006

28. Gain measurements : comparison with simulations Simulations from GARFIELD/MAGBOLTZ Endplate meeting – September 13, 2006

29. Ratio of the fields Endplate meeting – September 13, 2006

30. Gas mixture for LC TPC • The noble gas will be probably Argon (cost, properties) • Double gas mixture or triple (with CF4) ? • The quencher choice is still open Endplate meeting – September 13, 2006

31. Summary • Still have the precedent gain and resolution with the • Argon-Isobutane mixture • Measurement with Ethene mixture • The understanding of the gap between measurements and • simulation is not obvious • The Penning Effect could be useful • For now the choice is still open… Endplate meeting – September 13, 2006