Update on TPC R&D C. Woody BNL DC Upgrades Meeting October 9, 2003

C.Woody, Upgrades DC Meeting, 10/9/032 R&D Issues TPC drift cell now working Tests of new 3M GEM foils Electronics developments (see Chi’s talk) Plans for building prototype

C.Woody, Upgrades DC Meeting, 10/9/033 Test Drift Cell Drift Stack (presently 29 cm drift) Used to study Drift velocities Drift lengths Diffusion parameters Energy loss (dE/dx) Study impurities Readout structures Field cage design Lenses Lower movable source Laser Triple GEM Upper fixed source Lens Lab 2-86 in Physics

C.Woody, Upgrades DC Meeting, 10/9/034 Drift Cell Measurements Ar/CO 2 (80/20)Ar/CF 4 (95/5) Possible discrepency Gas mixture uncertainty 300 ppm O ppm H 2 O Energy Resolution (Top 55 Fe source) Drift Velocities (laser) 22% FWHM/mean 28% FWHM/mean * Data o Garfield * Data o Garfield

C.Woody, Upgrades DC Meeting, 10/9/035 Charge Distribution from Drift Cell (top source, 2 mm pad readout) Ar/CO 2 (80/20)Ar/CF 4 (95/5) Measured Simulation (N.Smirnov) pad number s =1.2 mm pad number s =1.7 mm s =1.1 mm s =1.4 mm

C.Woody, Upgrades DC Meeting, 10/9/036 GEM Foils from 3M Received 2 batches (50 each) of 10x10 cm foils Roll-to-roll process Limited to 12” width 3M Microinterconnect Systems Division, Austin, TX In collaboration with Univ. Chicago (J.Collar)

C.Woody, Upgrades DC Meeting, 10/9/037 Testing Small 3M Foils 3 stage GEM with three 1” dia. 3M foils 80 m m (55 m m) holes spaced in a hexagonal pattern with 140 m m pitch (approx. same as CERN foils) Visually looks to be excellent quality

C.Woody, Upgrades DC Meeting, 10/9/038 Comparison of Small Triple GEMS 3M GEMs give higher gain and have somewhat different slopes Ar/CO 2 (80/20)CF 4

C.Woody, Upgrades DC Meeting, 10/9/039 Electron Transfer Efficiency

C.Woody, Upgrades DC Meeting, 10/9/0310 Gain Stability - Small 3M GEMs Ar/CO 2 (80/20)CF 4 We observe a large gain variation with the small 3M GEMs with time Time scales involved imply a possible charging effect in the foils (Gas: 35 ppm H 2 0, <1ppm O 2 )

C.Woody, Upgrades DC Meeting, 10/9/0311 Gain Stability - Small CERN GEMs in Ar/CO 2 No large gain variations observed with small CERN GEMs

C.Woody, Upgrades DC Meeting, 10/9/0312 Gain Stability - Large Foils

C.Woody, Upgrades DC Meeting, 10/9/0313 TPC Prototype - To be built this year Full size module Tests field cage design Tests materials to be used in actual construction Allows testing with cosmic rays Provides structure on which to design and study readout plane Test bench for new readout electronics