RPC Electronics

1. RPC Electronics • On chamber electronics • Strips. • CMS RPC custom chip. • Amplify and discriminator board. • The FEM • Time digitizer • Interface to the DAQ • Crates • R&D PHENIX forward trigger review C.Y. Chi

2. RPC Strip • Our chamber is closely follow the CMS design. Our on-chamber electronics will try to follow their electronics too. • The CMS barrel strips is 1.3m long, 4 cm or 2cm wide. • 15/40 ohms impedance. 420pf/160pf capacitance. • Fully terminated strips. • CMS endcap RPC • Cover 5/16 degree in phi, 7 to 38mm in width and 22 to 55 cm in length • Un-terminated. • PHENIX RPC strip width range from 11.4 mm by 141mm to 64.6 mm by 554.2mm. • The smallest one has 46 ohms impedance and 16 pf of capacitance. • The largest one has 10 ohms impedance and 286 pf of capacitance. PHENIX forward trigger review C.Y. Chi

3. CMS RPC preamp/discriminator chip Build on AMS 0.8 um BiCMOS process, +5V device. 15 ohms input impendence. 45mW/channel. 8 channels per chip. It is designed in Bari, Italy. It has preamp, gain stage, zero crossing discriminator, monostable (cover the dead time) and LVDS driver. The chip is designed to deal with 20 fC up to 20 pC with1.7fC ENC noise. Zero crossing is necessary to deal with large dynamic range. The time walk is about .6ns except for very large charge. Testing show that threshold level could be as high as 100fc without loosing efficiency. PHENIX forward trigger review C.Y. Chi

4. CMS board CMS has two version of amplify/discriminator boards, 32 channels or 16 channels versions. 32 channel board is designed to be mated with a cable adapter. The cable adapter can be connected to coaxial cable. The impendence of the input can be adjusted through series resistance before the chip input. The output cable is .1” pitch twist-flat cable. It has DAC for threshold and build in test pulse function. PHENIX forward trigger review C.Y. Chi

5. RPC on-chamber electronics discussion • Ken contacted Bari, Italy group last year and we made a visit to Bari on Feb 9th. • We can re-fabricate 5000 chips, 2 wafers, for 50K Euro + package cost. • We have order four 32 channel boards + adapter boards • I bring back a 16 channel version of the board + it’s kapton adapter. • They sent us 12 chips last year. • The baseline program is to use CMS 32 channels board. • questions need to be resolved. • Impendence matching issues. • Power and slow download issues. • Size could be tight for RPC1a+b. PHENIX forward trigger review C.Y. Chi

6. RPC FEM L1 trigger discriminator T D C Correction Table L1 Delay 5 Events Buffer LVDS receiver DCM Leading Edge Time 40MHz from GTM 320 MHz PLLX8 Beam clock Timing Window cut To L1 A test FPGA code for the FEM is written. It is target at ALTERA Cyclone II device. 320 MHz clock will translate to 3.3ns time bin. We could reduced the bin size by half. The size of the FEM is determine by the twist flat cable.  64 channel for 6U module. PHENIX forward trigger review C.Y. Chi

7. RPC FEM Crate F E M F E M Inter- face T I M I N g 8 FEMs L1 primitives Slow Control DCM GTM L1 Each FEM produce 32 bits L1 primitives every clock cycle. Up to 8 FEM can send L1 primitives to interface board by using National semiconductor’s Channel link, 320Mbits/sec link. The interface board will use ALTERA Stratix GXII to send 256 bits of data to L1 every beam crossing. Interface board will collect 8 FEMs data and send DCM. A crate can have 16 FEMs. PHENIX forward trigger review C.Y. Chi

8. Channel count etc… The crate size is like 6U VME crate. I would like to limit the length discriminator cable to 10 meters. The RPC2, 3, we will need to find the crate space near the detector. PHENIX forward trigger review C.Y. Chi

9. R&D issue Amplify/ discriminator cable strip Try to understand the issue between termination, interconnect and amplify/discriminator impedance. Amplified pulse Amplified pulse added ideal reflected pulse PHENIX forward trigger review C.Y. Chi