1 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news First indications from electrostatic simulation exercise Goals of the simulation Parameters of simulated THGEM Values of E z Simulated trajectories News about UV light source work done by Gabriele Giacomini

2 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Electrostatic calculations are essential to optimize our THGEMs We decided to start from simple simulation exercises with ANSYS (and Garfield) in order to estimate the optimal geometrical and electrical configuration for the THGEM Critical points: - Effective CsI Q.E. depends on the electric field at the CsI surface - The backscattering effect depends on the gas and on the field too -The collection of photoelectrons in the holes for multiplication is difficult to measure and critically depends on geometry and fields The optimization of the THGEM geometry and operating parameters will need some understanding, which can be achieved only combining measurements and simulations

3 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Focusing is done by hole dipole field. Maximum efficiency at E drift =0 (like in GEM). Slightly reversed E drift (50-100V/cm) good photoelectron collection & low sensitivity to MIPS (~5-10%) ! Relative Reverse drift studies at Weizmann e Ref. PC E drift E E E=0 MIP Attention: gas and field dependent!

4 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news High field on the PC surface (high effective QE) Also at low THGEM voltages (e.g. in Ne mixtures!) e Ref PC 0.4mm thick 0.3mm holes 0.7mm pitch >3kV/cm Electric field on photocathode surface created by the hole dipole field  V THGEM =2200V  V THGEM =1200V  V THGEM =800V  V THGEM =2200V  V THGEM =1200V  V THGEM =800V C. Shalem et al. NIM A558 (2006) 468 FIELD AT THE THGEM CsI SURFACE Attention: varies with hole-pitch & hole-voltage

5 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Recent measurement by Elena Single THGEM, diam. 0.4 mm, th. 0.4 mm, pitch: 0.8 mm

6 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Photocurrent vs field on CsI not acceptable acceptable good

7 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news The operational ΔV of THGEMs depends on gas Simulation performed using tools provided by RD51 Colleagues: based on “ANSYS” and “GARFIELD”

8 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Geometrical parameters of simulated THGEM DEFAULT VALUES Thickness: 0.6 mm, Hole diameter:0.4 mm, Pitch0.8 mm, Rim:0.0 mm, Cu thickness:0.035 mm, Drift distance:4.0 mm, (cont. plane) Induction dist.:3.0 mm, (cont. plane) Induction field: 0.0 V/cm Drift field:0.0 V/cm ΔV: 1500 V Basic cell structure Simulation performed by Gabriele Giacomini, using tools provided by Matteo Alfonsi and Gabriele Croci, based on ANSYS and GARFIELD

9 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Values of E z along the “z” axis, for different diameters hole scan along the “z” axis (hole axis) Thickness: 0.6 mm, Pitch: 0.8 mm, Induction field: 0.0 V/cm Drift field: 0.0 V/cm

10 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Values of E z along the “y” axis, for different diameters 0.4 mm diam. hole Thickness: 0.6 mm, Pitch: 0.8 mm, Induction field: 0.0 V/cm Drift field: 0.0 V/cm diameter:

11 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Values of E z along the “y” axis, for different pitches pitch: hole Thickness: 0.6 mm, Diameter: 0.4 mm, Induction field: 0.0 V/cm Drift field: 0.0 V/cm

12 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news field values depend on: Thickness:E z = E z 0 × (th 0 / th) Hole diameter:non trivial (see slides) Pitch:non trivial (see slides) Rim:unknown Drift field:E z = E z 0 + E D ΔV: E z = E z 0 × ΔV / ΔV 0 Max. V attained with th. = 0.2 mm ~ 900 V Max. V attained with th. =0.4 mm:~1400 V Max. V attained with th. = 0.6 mm:~1700 V

13 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Values of E z on the CsI surface for various diameters and pitches, compared with active area E z ~ 1/ (pitch) 4

14 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Values of E z on the CsI surface for various pitches and diameters, compared with active area E z ~ exp(diam.)

15 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Photoelectron collection hole efficient collection area dead area x y

16 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news trajectories for drift = 0 V/cm x y scan along the “y” axis scan along the “x” axis x y Collection efficiency is o.k. y E z = V/cm th. 0.6 mm, diam. 0.4 mm, pitch: 0.8 mm, ΔV = 1500 V

17 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news trajectories for drift = -50 V/cm x y scan along the “y” axis scan along the “x” axis x y partial collection efficiency y E z = V/cm “full collection radius” = 0.42 mm th. 0.6 mm, diam. 0.4 mm, pitch: 0.8 mm, ΔV = 1500 V

18 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news trajectories for drift = -500 V/cm scan along the “y” axis scan along the “x” axis low collection efficiency y E z = V/cm “full collection radius” = 0.33 mm th. 0.6 mm, diam. 0.4 mm, pitch: 0.8 mm, ΔV = 1500 V

19 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news trajectories for drift = +500 V/cm scan along the “y” axis scan along the “x” axis E z by far too low y E z = - 43 V/cm x y y x th. 0.6 mm, diam. 0.4 mm, pitch: 0.8 mm, ΔV = 1500 V

20 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news trajectories for drift = +500 V/cm scan along the “y” axis scan along the “x” axis y E z = + 57 V/cm x y y x Loss of e - th. 0.6 mm, diam. 0.4 mm, pitch: 0.8 mm, ΔV = 1500 V

21 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Consistency check with other simulation programs lattice spacing: 50 μm, 30 μm, 20 μm

22 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Consistency check with other simulation programs

23 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Main uses of UV light UVA light (315 nm – 400 nm) is also called photochemical ray because many kinds of adhesives, fluorescence, and other chemistries react to UVA light. For the reason, its potential uses are uncountable, including UV curing/printing/coating, skin therapy, bank note detector, bio-weapon detector, air purification, etc Applications: 1) UV curing systems, UV coating/printing assemblies for PVC, film, glass materials, and etc. 2) Security products such as Bank note detectors, Bio-weapon Detectors, Crime scene inspection, etc. 3) Phototheraphy devices to treat skin diseases including psoriasis, rickets, eczema, jaundice, and atopic dermatitis. 4) Automotive leak detector, Food checking. UVB light (280 nm – 315 nm) is well known that UVB light exposures can be hazardous to human eyes and skin, but also UVB, often called as a dorno ray or a health ray, is assumed to be a beneficial to human health, UVB produces vitamin D in the skin, and prevent skin cancer caused by inefficient UVB exposure. Also in combinations of UVA (or by it self) UVB has become an increasingly popular and effective treatment for psoriasis, vitiligo, eczema, and other skin conditions. Most effective in case of psoriasis is UV light with wavelength of 311 nm Applications: 1) Sterilization systems to purify water, surface, and air 2) Analysis of Minerals 3) EPROM Erasure 4) High Security UV marks UVC light (200 nm – 280 nm) is also called germicidal ray. are the highest energy, most dangerous type of ultraviolet light. With that energy, it destroys DNA & PNA in microorganisms such as bacteria, viruses & mold, Thus, it generates Ozone. Especially 254.7nm is most effective wavelength for disinfections Applications: 1) Water/Surface purification system 2) Laboratory testing devices

24 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news LED at 255 nm