THGEM short results collection December 2008 @ CERN Gabriele Giacomini, Jarda Polak, Elena Rocco

How to read this summary: Since Jarda already presented all data about the photocurrent meas. during the GDD meeting 32, the latest preliminary and partial results are here reported. In the next slide you’ll see the setup use for the three different measurements and then the most representative results. REMARK: some of them should be understood and/or redone.

Same setup, several & different purposes Setup for photocurrent measurements and optimization of performance for the double THGEM structure with the iron source Quartz window of the double THGEM chamber (type C7) Hidden N2 exhaust Avantes – UV lamp picoammeters 55Fe Double THGEM C7 Leszek’s chamber Dummy/dummy Oriel Lamp N2 inlet Gas mixer Filter 3.0 OD Setup for UV light meas. with the double THGEM structure Filter 0.5 OD Three positions of the shutter: 1.completly open, 2.closed (some internal reflections), 3.Open + filter 3.0 OD Narrow Filter

Iron Source: drift scan ΔV1= Δ V2=1.36 kV THGEM: C7 d=0.4 mm pitch =0.8 mm t=0.4 mm rim=0.01 mm Iron Source: drift scan ΔV1= Δ V2=1.36 kV drift = wires THGEM 2 THGEM 1 anode d=4.5 mm d=1.6 mm

Light: drift scans with ΔV=1kV & ΔV=0.9 kV THGEM: C7 d=0.4 mm pitch =0.8 mm t=0.4 mm rim=0.01 mm drift = wires THGEM 2 THGEM 1 anode d=4.5 mm d=1.6 mm Light: drift scans with ΔV=1kV & ΔV=0.9 kV High voltage applied to the THGEMs  gain Measurement to be redone!

Light: drift scan measurement THGEM: C7 d=0.4 mm pitch =0.8 mm t=0.4 mm rim=0.01 mm drift = wires THGEM 2 THGEM 1 anode d=4.5 mm d=1.6 mm

Light: delta V scan (½) THGEM: C7 d=0.4 mm pitch =0.8 mm t=0.4 mm rim=0.01 mm drift = wires THGEM 2 THGEM 1 anode d=4.5 mm d=1.6 mm Light: delta V scan (½)

Light: Delta V scan (2/2) All currents monitored!!! THGEM: C7 d=0.4 mm pitch =0.8 mm t=0.4 mm rim=0.01 mm drift = wires THGEM 2 THGEM 1 anode d=4.5 mm d=1.6 mm Light: Delta V scan (2/2) All currents monitored!!! The sum of the total currents is not zero. There’s some systematic , but the behaviour should be not affected since the larger deviation is for higher current so for the highest field.

Single photon spectrum THGEM: C7 d=0.4 mm pitch =0.8 mm t=0.4 mm rim=0.01 mm drift = wires THGEM 2 THGEM 1 anode d=4.5 mm d=1.6 mm Single photon spectrum Exponential fit! With the assumption to be in the single photon, the estimated rate from the current is 40 kHz!!! Shutter closed!!!internal reflections.