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Why we have been interested by the new FE electronics ?. RPCs for high rates. The rate capability of a RPC is limited by the voltage drop ( Vd ) in the resistive elecrode The voltage drop in the resistive electrode is : Vd = I * R I = counting rate * average charge
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RPCs for high rates • The rate capability of a RPC is limited by the voltage drop ( Vd ) in the resistive elecrode • The voltage drop in the resistive electrode is : Vd= I * R I = counting rate * average charge R = resistivity * thickness of electrode
How to increase the RPC rate capability? • Decrease the resistance decrease resistivity and/or thickness • Decrease average charge per count But Also : The ageing of the RPC is proportional to the current R. Cardarelli et al. developed a new high performance front end electronics in order to decrease the average charge, details in : http://iopscience.iop.org/1748-0221/8/01/P01003
Characteristics of the new preamplifier we have used for the tests : The New FE is based on a BJT transistor new preamplifier developed by R. Cardarelli • Sensitivity 1.5 mV/fC • Noise 2 fC RMS • Latch capability 100 ps • BW 10 MHz • Vth > 1.5 mV • Qth > 10 fC
Slide by R. Cardarelli : more details see proc., RPC 2012 conference
Slide by R. Cardarelli : more details see proc., RPC 2012 conference After the avalanche, the return to zero of the signal is driven by the BW ~ 10MHZ Rise time faster than the avalanche, Signal follows the avalanche process process
A new version of the FE has been developed with a Si-GeBJT transistor reaching : • Qth < 1fC
High rate capability Performance measurements of a 2mm gap and of a 1+1 mm bigap RPC with electrodes of phenolic plastic material (2.10^10 Ohm) done by R. Cardarelli et al. at the GIF, using the new preamplifier with a 50 ohm impedance pick-up strip show a rate capability up to 10 kHz/cm^2
With a high sensitivity & low noise preamplifier many aspects become very important: -control and reduce as much as possible all the external sources of noise, in particular the noise produced by the switching HV power supply ; For this reason we installed a high frequency filter based on a transformer - control the grounding , it has to be robust to reject the external radiofrequencies - HV high Frequency filter working principle :
Decrease by several hundreds of volts of the WP Decrease significantly of the average charge New FE : -High sensitivity -Low noise -Fast shape We can expect : - High rate capabilities - Safer operation of the chambers - Slower aging of the detector at higher Luminosities (due to the standby like operation)