Absolute gas gain measurement in straw drift tubes

Absolute gas gain measurement in straw drift tubes at 2 bar 15 June 2010 A. Kashchuk (PNPI, INFN), P. Gianotti (INFN) PANDA meeting at Stockholm 1

Experimental setup for absolute gas gain measurements at LNF 137 Cs 1. 395 GBq Straw tubes ‘a la COSY’ filled with Ar/CO 2(90/10) gas mixture at overpressure 1000 mbar 15 June 2010 A. Kashchuk (PNPI, INFN), P. Gianotti (INFN) PANDA meeting at Stockholm 2

Ionization current I 0 changes polarity if voltage ±V changes polarity ON 15 June 2010 A. Kashchuk (PNPI, INFN), P. Gianotti (INFN) PANDA meeting at Stockholm 3

Where zero at ±V at source ON? 12/12/2021 A. Kashchuk (PNPI, INFN), P. Gianotti (INFN) PANDA meeting at Stockholm 4

I 0 finding from raw data 15 June 2010 A. Kashchuk (PNPI, INFN), P. Gianotti (INFN) PANDA meeting at Stockholm 5

Spread of currents in various straws within 20% 4 straws in parallel 1: 4 Straw 1 Straw 2 Straw 3 Straw 4 10 4 straws connected in parallel Current (n. A) 1 0, 1 Variations around middle within 20% 0, 01 Middle with error bar 20% 0, 001 0, 0001 1000 15 June 2010 1200 1400 Voltage (V) A. Kashchuk (PNPI, INFN), P. Gianotti (INFN) PANDA meeting at Stockholm 1600 1800 6

Gas gain increment finding Ar. CO 2(90/10) at room temperature and 1000 mbar over-pressure 15 June 2010 A. Kashchuk (PNPI, INFN), P. Gianotti (INFN) PANDA meeting at Stockholm 7

Gas gain presented in Torino – wrong Reason: P measured on input at open output resulting lower pressure inside tube Frascati-Ferrara (A. Kashchuk) J. Smyrski Torino_AK 1000000 Presented in Torino Ga Gain 100000 10000 New measurements 1000 10 0 15 June 2010 200 400 600 800 1000 HV (V) 1200 A. Kashchuk (PNPI, INFN), P. Gianotti (INFN) PANDA meeting at Stockholm 1400 1600 1800 2000 8

Pedagogical reminds Gain (GG) in a cylindrical proportional counter is a function of the applied voltage V Diethorn parametrization b and a are the radii of the anode wire and of the cathode, respectively. Therefore ln(GG)/V vs V is a straight line with slope DV and intercept Emin. ln(GG)/V GAS GAIN 100000 Emin 0, 1 15 June 2010 GAS GAIN 100 HV A. Kashchuk (PNPI, INFN), P. Gianotti (INFN) PANDA meeting at Stockholm 9

Absolute gas gain and Diethorn’s parameterization G(V, ρ) 1000 mbar 1000000 Gas gain 100000 Diethorn Emin=28. 5 k. V/cm; ΔV=30 V Emin – is the minimal field needed for multiplication; ΔV - is the potential variation required to produce one more electron in the avalanche; 10000 100 10 1000 15 June 2010 1100 1200 1300 1400 1500 HV (V) A. Kashchuk (PNPI, INFN), P. Gianotti (INFN) PANDA meeting at Stockholm 1600 1700 1800 1900 10

Gas gain as current-ratio vs. Diethorn’s equation G(V, ρ) helps to see space charge effect Diethorn 28. 5/30 Diagonal 140000 Emin=28. 5 k. V/cm; ΔV=30 V GG_Current ratio 120000 Diethorn’s model validity (αTown=k. E) 100000 80000 60000 Current becomes sensitive to space charge Very high rate and large signals (to be better with MIP) V 0 0 =18 HV op ☺ 40000 20000 G_Diethorn 0 0 20000 1700 V 15 June 2010 12/12/2021 40000 60000 80000 100000 1800 V A. Kashchuk (PNPI, INFN), P. Gianotti (INFN) A. Kashchuk INFN-Ferrara and PNPI-St. Petersburg PANDA meeting at Stockholm 120000 140000 1900 V 11 11

Gas gain vs. V and over-pressure Frascati-Ferrara (A. Kashchuk) J. Smyrski 850 mb 750 mb 600 mb 500 mb Ga Gain 100000 G(1800, 500)=212000 G(1800, 600)=135200 G(1800, 750)=94100 G(1800, 850)=70600 G(1800, 1000)=52900 10000 1600 15 June 2010 1650 1700 1750 HV (V) A. Kashchuk (PNPI, INFN), P. Gianotti (INFN) PANDA meeting at Stockholm 1800 1850 1900 12

Conclusion • Results of gas gain measurements obtained with 2 methods: Cs-137 (presented here) and Fe-55 (presented by J. S. in Torino) are in agreement • Gas gain 105, if needed for high space resolution, can be reached at reduced over-pressure, e. g. from 1000 to 700 mbar in vicinity of HV=1800 V • Gas gain stabilization can be made by an automatic regulation of HV or over-pressure 15 June 2010 A. Kashchuk (PNPI, INFN), P. Gianotti (INFN) PANDA meeting at Stockholm 13