E-field calculations for the TPC/HBD N. Smirnov Upgrade Working Group Meeting 05/13/03, BNL.

100 MeV e - 20 cm 55 cm 70 cm CsI Photocathode Fast, Compact TPC with enhanced electron ID capabilities 2 x 55. cm 16 identical modules with 35 pad-rows, double (triple) GEM readout with pad size: 0.2x1. cm². Maximum drift: cm. “Working” gas: fast, low diffusion, good UV transparency.

miniTPC module, proposed variant 16 identical miniTPC modules with the Drift distance 48. cm and its own Field Cage Common gas volume with double windows “working” gas – CH4, but another gases (mixtures) will be studied to select the best and convenient one. Shape: trapezoid, Cathode: Kapton or Mylar Field Cage: Kapton or Mylar with printed strip structure (for bottom and sides, wires for a top) N of Pad-rows: 35 Pad dimention: 1.x0.2 cm2 All construction (support) elements: low mass composites material like STESALIT readout channels / module / Detector Anode (Gas amplification, ReadOut): microPattern Gas Detector(s) with Printed pad structure on Kapton or Mylar ( GEM, microMeGas,…)

Points should be checked Low mass construction “good” quality of Electric Field “work together” with Cherenkov Detector Simulation: to demonstrate that the construction approach is “reasonable” Full scale prototype: real answer

MAXWELL and GARFIELD were used to simulate an Electric Field Cathode Anode +/- 20 cm 80 strips, 3 mm width, 5 mm step. Cathode, 36 kV 30 cm 10 cm 40 cm Y X 5 mm

2D MAXWELL Ex / Ey / y x x y Ex / = 916 V/cm

GARFIELD, “wires on a top” variant. Comparison with MAXWELL Ex / Ey / Y Y GARFIELD; MAXWELL Strip side wire side

Cherenkov Detector E-field 30 cm mini TPC field cage wires 3 mm 5 cm -36 kV0. V V wire plane with 5 mm step

Cherenkov Detector E-field Ex, V/cm y x x y Ey, V/cm

Status and future steps It looks not so bad We are going to continue the simulation ( with FANLAB may be) But the prototype is the crucial step.