Results achieved so far to improve the RPC rate capability G.Aielli for the ATLAS RPC group

Improvement of detector rate capability Detector rate capability limited by voltage drop on resistive electrodes. Strategies to improve rate capability: 𝑉 𝑔𝑎𝑠 = 𝑉 𝐴 −𝑅∙𝐼= 𝑉 𝐴 −𝜌∙𝑑∙Φ∙𝑄( 𝑉 𝑔𝑎𝑠 ) Reduce resistivity Allows to work at higher rates and depends on temperature, relative humidity of both gas and environment. Does not solve the problem of the ageing (if any). Reduce average charge/avalanche. Grants at the same time an higher rate capability at constant current. Reduce electrode thickness A reduction of the electrode thickness from 1.8 mm to 1.2 mm has been recently achieved (BME chambers – bulit in 2013). But the main focus of the past R&D was on reduction of the average charge per count.

Development of a new fast charge amplifier. A custom charge-to-voltage amplifier in BJT technology was purposely developed for this application. Importante feactures are : extremely good signal/ration , radiation hardness and possibility to match low impedence trasmission line Example of Input pulse (above) and relative output pulse (below) Properties of the preamplifier Working principle Voltage supply 3-5 Volt Sensitivity 2-4 mV/fC Noise (up to 20 pF input capacitance) 1500 e- RMS Input impedance 100-50 Ohm B.W. 10-100 MHz Power consumption 10 mW/ch Rise time input 300 – 600 ps Radiation hardness 1 Mrad, 1013 n cm-2 Concept schematics of the amplifier Presentation by R. Cardarelli (INFN Roma Tor Vergata), New diamond detector structure and related front-end electronics for sub-nanosecond TOF application, at 13th Topical Seminar on Innovative Particle and Radiation Detectors, Siena 2013

Improvement of detector rate capability Reduction on average charge per count by use of a new fast charge amplifier in Silicon BJT technology. From 20 to 3 pC/count for MIPS 20 pc/count 3 pc/count The introduction of the new preamplifier permits a shift of the efficiency curve for a ATLAS like RPC (2 mm gas gap) at lower voltage – lower charge per count.

Improvement of detector rate capability Test beam result at the Gamma Irradiation Facility (CERN) on an homogeneously irradiated detector. ATLAS like 2 mm gas gap 20 x 20 cm^2 size with new FE The total charge per count lowers from 30 to 4 pc/count (average for the GIF photon induced counts New working point  full efficiency at a rate of 7 kHz/cm2. The plateau shift is fully compatible with the Ohmic drop on resistive electrode. R. Cardarelli, A fast electronics for RPC based precision tracking muon trigger at high luminosity LHC, Oral presentation at XI workshop on Resistive Plate Chamber and Related Detectors, LNF, 2012.

Improvement of detector rate capability Efficiency vs Applied voltage for a 1+1 mm bigap RPC Test carried out with a different detector layout: Result for a 1+1 mm bi-gap RPC operated with the new preamplifier. Further improvement with respect to the 2 mm gas gap with the same electronics Total charge per count ~2pc/count, to be compared to the ATLAS standard gap and FE of 30 pc/count Full efficiency at a counting rate of 11 kHz/cm2 L. Paolozzi (INFN Roma Tor Vergata), Performance of a new generation RPCs for particle physics at colliders of the next generation, Poster at 13th Vienna conference on Instrumentation, Vienna, 2013.

Improvement of detector timing performance Time distribution for a 1 mm gap RPC at low counting rate. Readout by NINO Front End. Time distribution for a 1 mm gap RPC at a counting rate of 3 kHz/. Readout by new custom preamplifier. Raw resolution 7309 ps including the trigger scintillator jitter of 550 ps. Time resolution in high rate environment after correction for trigger jitter: 𝛔 𝐭 =𝟒𝟖𝟎±𝟐𝟎 𝐩𝐬 The result obtained at high rate is compatible with the one obtained at lower rate with the same detector. L. Han, Studies on fast timing and high precision tracking trigger based on Resistive Plate Chambers, Poster at 13th Vienna conference on Instrumentation. L. Paolozzi, Performance of a new generation RPCs for particle physics at colliders of the next generation, Poster at 13th Vienna conference on Instrumentation.

Improvement on frontend preamplifier Preliminary results and simulations for SiGe technology applied to the new preamplifier. Silicon amplifier SiGe amplifier R. Santonico, Problems and opportunities for the RPCs of the next future, Oral presentation at XII workshop on Resistive Plate Chamber and Related Detectors. Pulses recorded from a 500 micron diamond sensor irradiated by 241Am source. Single stage amplifier for SiGe technology: sensitivity limited from scope noise.

Improvement on front-end preamplifier From Cadence simulation of the full preamplifier in SiGe technology: Simulated amplified pulse for a 3 fC input signal Noise ≅ 200 electrons RMS

Summary and timeline of the preliminary R&D phase 2008 first prototype of a new FE scheme with a standard BJT applied to diamond detectors 2009 First prototype of a 20x20 cm^2 size bi-gap RPC with a gamma source 2010 first RPC ATLAS-like prototype (2 mm gas gap) 20 x 20 cm^2) equipped with the NEW FE realized on a dedicated discrete component PCB. Beam and GIF rate capability test 2011 first test of a Bi-gap small prototype( 20x20cm^2) at the GIF with the new FE 2012 first prototype of discrete component SiGe preamplifier based on the new FE concept

Expected R&D timeline Activity 2014/06 2014/09 2014/12 2015/03 2015/06 2015/09 2015/12 2016/03 2016/06 2016/09 2016/12 2017/03 2017/06 2017/09 2017/12 New Gas Search   New Gas GIF validation SiGe chip FE development Final SiGe chip FE Pre Production New gas gap lab studies Large size gap high rate validation Module 0 production and beam test Module 0 performance and Ageing test

Conclusions Preliminary test on small RPC prototypes (20x20cm^2) with higher rate capability already quite good. Further tests needed to confirm and to optimize the performance More R&D needed on realistic size prototypes (~1m^2)  define in a new layout and test the performance More investigation on the thinner gas gap construction to fit the ATLAS need for BIS07/08 Ageing studies also need to be done