Endplate meeting – September 13, 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, 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, Gain measurements : description Description : Using the same detector Transparent plastic box of 20 cm x 20cm x 6 cm size “Standard” 50  m mesh of 10 cm x 10 cm size Sources: - Fe 55 (5.9 keV) - COOL-X (8.1 keV) Monitoring of: - pressure - H 2 O Gas mixing system with triple mixture available Aims : find gas mixture comfortable gain margin to use into a Micromegas TPC verification of the Townsend coefficients

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

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

Endplate meeting – September 13, Gain measurements : simulation Simulations from GARFIELD/MAGBOLTZ Choice : E drift = 220 V/cm

Endplate meeting – September 13, Gain measurements : simulation Simulations from GARFIELD/MAGBOLTZ Choice : E drift = 300 V/cm

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

Endplate meeting – September 13, Energy (keV) Counts Gain measurements : spectrum Argon Isobutane : 5% (source : Fe 55 ) E mesh = 72 kV.cm -1 RMS ~ 6,0 % 3 keV5,9 keV

Endplate meeting – September 13, Pressure monitoring in Saclay

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

Endplate meeting – September 13, Gain curves Mixtures of gases containing Argon and Isobutane E drift = 220 V/cm

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

Endplate meeting – September 13, Gain curves Mixtures of gases containing Argon, Ethane E drift = 100 V/cm

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

Endplate meeting – September 13, Gain curves Mixtures of gases containing Argon, Methane E drift = 300 V/cm

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

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

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

Endplate meeting – September 13, Penning effect GasIonization energy E i (eV) Xe 12,1 Ar15,7 Ne21,6 He24,5 Possibilities of Penning mixtures: Ne-Ar Ar-Xe Ar-Acetylene Ne-Xe Ar-impurities who have lower E i ?! …

Endplate meeting – September 13, Gain measurements : Townsend coefficients N = N 0 ×exp[  ×d] With  = A×P×exp[-B×P/E] Argon-Isobutane

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

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

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

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

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

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

Endplate meeting – September 13, Ratio of the fields

Endplate meeting – September 13, Gas mixture for LC TPC QuencherNameLower Explosion Limit CH 4 methane5,0 % C2H4C2H4 ethene, ethylene2,7 % C2H6C2H6 ethane3,0 % iC 4 H 10 isobutane1,8 % C 6 H 10 cyclohexene< 1 % C 6 H 12 cyclohexane Dangerous for the environment 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, 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…