Garfield simulations on Micromegas CERN Summer Student Programme










- Slides: 10

Garfield simulations on Micromegas CERN Summer Student Programme 2013 Tomohiro Yamaji SV: Theo Alexopoulos

Objectives Garfield-9/++ simulation of Micromegas(MM) ◆Objictive : Making movies which describe how MM works ・Simple configuration(2 D, flat cathode) ・realistic structure(3 D, cathode stripe, not perfect)

How to make movies ①Garfield-9(source code modified) ・Avalanche simulation(Call microscopic_avalanche) The default setup of garfield-9 cannot write whole electron path to output files. →source code is modified(Thanks to Mr. Kataoka) When any drift lines are simulated, electron path are printed. ②Manipulate output files ・Convert the structure of output files to simple ASCII format ・For further manipulation, digitize data and do linear interpolations ・Rearrange data according to time series ③Drawing movies ・Processing 2, a java-like program which is suitable for drawing pictures/movies

Movie(Simple configuration) ◆Very simple configuration ・ 2 D, grounded wire. Flat cathode ・primary electron starts between wires

Some features deduced from movie ◆drift property ・electron Electrons in an avalanche can reach anode by about 1 nsec gap between strips and mesh: 128 μm electron drift velocity in amplification region: 120μm/nsec ・ions Ions reach mesh by about 100~200 nsec →Ions are one hundred slower than electrons Some Ions(<10%) escape to drift region ◆apparent wrong behavior ・amplification is very small, only about 100 →probably due to defects in integration parameters of microscopic method By using AVALANCHE function, an amplification factor: ~5× 104

Movie(more realistic)

Muon track

Backups

Avalanche amplification in amplification region ◆simulation condition ・ 2 D Cell grounded mesh →simple wire ・No B field ・AVALANCHE function used ◆results ・avalanche multiplication: ~5. 5× 104

Drift velocity/Lorentz angle ◆Drift property when B fields (perpendicular to E field) are induced ・Drift velocity vd=4. 6919 cm/μsec @E=600 V/cm, B=0 T vd=4. 6299 cm/μsec @E=600 V/cm, B=0. 3 T ・Lorentz angle 17. 2071 deg @ E=600 V/cm, B=0. 3 T