Phone meeting, December 20, 2005 P. Colas - Resolution in BOS Micromegas TPC 1

Resolution from the 1mm pads of the Resolution from the 1mm pads of the Berkeley-Orsay-Saclay Micromegas TPCBerkeley-Orsay-Saclay Micromegas TPC

Resolution from the 1mm pads of the Resolution from the 1mm pads of the Berkeley-Orsay-Saclay Micromegas TPCBerkeley-Orsay-Saclay Micromegas TPC

• Reminder: the Berkeley-Orsay-Reminder: the Berkeley-Orsay-

Saclay cosmic setupSaclay cosmic setup

• resolutionresolution

D. Burke5, P. Colas5, I. Giomataris5, V. Lepeltier4, M. Ronan1, K. Sachs2, T. Zerguerras3

1) LBNL Berkeley, 2) Carleton Univ., 3) IPN Orsay, 4) LAL Orsay, 5) DAPNIA Saclay

TPC MEETING

Phone meeting, December 20, 2005 P. Colas - Resolution in BOS Micromegas TPC 2

Cosmic-ray tracks Rows 5 & 6

(software from D. Karlen, adapted by M.Ronan)

Phone meeting, December 20, 2005 P. Colas - Resolution in BOS Micromegas TPC 3

2x10 mm2 pads

1024 pads

1x10 mm2 pads

Readout anode pad plane

Track reconstructionTrack reconstructionTrack reconstructionTrack reconstruction

Subtract pedestals, using the first 15 time buckets + 15 after the chamber end

Max-likelihood fit the distribution of the number of electrons per pad with 4 parameters :

(x0, ,1/R, )

is the track width

Phone meeting, December 20, 2005 P. Colas - Resolution in BOS Micromegas TPC 4

ResolutionResolutionResolutionResolution

Cross-check of the method: use only lines 1 and 2 and 9 and 10 to define , extrapolate hit 5 into row 6 using this , and make the distribution of the difference between extrapolation and position in row 6 divided by sqrt(2)

Sigma of this distribution is the resolution.

This gives the same result as using the track fitted using all rows except 5 and 6

Phone meeting, December 20, 2005 P. Colas - Resolution in BOS Micromegas TPC 5

Results on resolution

Phone meeting, December 20, 2005 P. Colas - Resolution in BOS Micromegas TPC 6

Results on resolution

Phone meeting, December 20, 2005 P. Colas - Resolution in BOS Micromegas TPC 7

Results on resolution

Phone meeting, December 20, 2005 P. Colas - Resolution in BOS Micromegas TPC 8

Residuals vs track position in the pad

-> NO BIASXtrack

Xp

ad-X

track

Phone meeting, December 20, 2005 P. Colas - Resolution in BOS Micromegas TPC 9

Results on resolution at 1T

Gas mixture E drift (V/cm)

0 (m) 0 (m)

MC

Neff Neff

MC

Ar+5%iso 220 99±15 91.4±5.0 40.8±6.4 42.1±2.5

P10 140 126±41 124±9 20.0±8.5 22.7±2.5

Ar+3%CF4 200 225±26 103.8±4.8 19±20 58±17

Note: extrapolated to 4T, we expect a resolution of 144 at 2m with Ar isobutane and better than 120 on average, wherever the charge sharing holds

Phone meeting, December 20, 2005 P. Colas - Resolution in BOS Micromegas TPC 10

ConclusionsConclusionsConclusionsConclusions

Monte Carlo is now available for the diffusion and resolution studies.

It shows a very good agreement with the data, except for ArCF4

This shows that:

- Mis-calibrations, noise, and all kind of experimental problems (the simulation assumes a perfect detector) have no effect on the resolution.

- CF4 behaves in a way different from expectation, though the drift velocity and track width are in very good agreement with MC -> one more piece in the CF4 puzzle