1. RPC Front End Electronics
On chamber discriminator
The strips
The CMS discriminator chips
The discriminator board
Test results
The TDC board
The TDC and Crate block diagram
The TDC board test result
The trigger board
The board counts
Status
July 10, 2008
PHENIX RPC 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.
Lemo cables are used to connect strip to the discriminator board
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.
July 10, 2008
PHENIX RPC 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.
All the chips has been fabricated. Two wafers has been packaged and tested.
July 10, 2008
PHENIX RPC review
C.Y. Chi

4. RPC 32 channel discriminator board
Cable adapter board
LVDS discriminator
output
Serial
download
32 channels per board
Fused +6V input analog/digital power supply ~.46A
(use +5V, +3V through low drop regulators)
Serial download is used to set 10 bits 4 channel threshold DAC (4mv per bin) and
Fire test pulse.
July 10, 2008
PHENIX RPC review
C.Y. Chi

5. Connection diagram RPC TDC 64 ch RPC disc 32 ch
Half octant
Module edge
3M (Gray)
RPC
TDC 64 ch
RPC
disc 32 ch
3M (Gray)
Adapter
Board
16 short
RG174 cables
2-3 m cable ?
8 meters cable ? 3M
N3432-L302RB 3M PL Or pl 3M
3M (gray)
2-3 m cable?
8 meter cable ?
Adapter
Board
3M (Black)
D89140-????
3M (Black) RB
Signal Cable : 40 conductors twist flat ribbon cable
3M 1700/40 Twisted Pair, Flat Cable, .050" 28 AWG Stranded
Fire rating VW-1
July 10, 2008
PHENIX RPC review
C.Y. Chi

6. On board test pulse vs. threshold study
The discriminator is moving 4mv per step.
The test pulse is feed to the input amplify through 1pf cap.
(not for calibration, functional check only)
Channel 14 TDC distribution, DAC step =80
TDC
step
July 10, 2008
PHENIX RPC review
C.Y. Chi

7. Direct pulse injection (threshold effect)
CMS Disc threshold
Channel 26
Channel 26
Channel 28
TDC
Channel 30
Channel 32
Channel 32
Threshold (8 mv per step)
TDC distribution at step =20 (160mv)
Test pulse is set around ~ 4mv input
July 10, 2008
PHENIX RPC review
C.Y. Chi

8. Direct Pulse Injection (fixed threshold)
Channel 44
Channel 45
Channel 46
TDC
disc.
fired
Input (steps)
Inject test pulse through the cable adapter card + 10pf capacitance (channel 45)
2mv per step, 160mv threshold (~80fc)
Cross talk seen at round 100mv.
July 10, 2008
PHENIX RPC review
C.Y. Chi

9. Long output cable study
DISC LVDS output at
discriminator board
1.4V
DISC output after
~10 meter cables
1.63V
69 ns time difference
1.61ns/ft  ~42 ft
Digitally subtracted pulse between
+ and – side of discriminator LVDS output
500mv per division
Long output cable study
July 10, 2008
PHENIX RPC review
C.Y. Chi

10. RPC TDC MODULE D 32 channel I digitizer S C Receiver LVDS Interface
Chip
Collects 64
Channel Of
Data
L1 trigger
primitives
TDC serial download
Trigger
window
L1 trigger primitives
Event
Data
32 channel
digitizer D I S C
Disc Serial
download
LVDS
Transmitter
MASK
Digitized
Data
Receiver
LVDS
Serial
Download
Timing etc.
L1 trigger etc
Event
Data
44X BC
Test Pulse
Serial download
PLL
Test
Pulse
44X BC
4x beam clock
July 10, 2008
PHENIX RPC review
C.Y. Chi

11. TDC Module TDC: Test Pulse: Trigger Window: Mask:
Use 44X beam crossing clock to digitized the discriminated LVDS pulse, ~2.5ns for 9.6MHz RHIC clock
Test Pulse:
Generated internally with the FPGA with the same 44x beam crossing clock
Trigger Window:
The lower and upper limits be can set channel by channel
Mask:
Mask bits can be set to turn off individual channel.
Serial data to Discriminator Board:
Control test pulse firing and discriminator threshold ( chip by chip)
The TDC Internal Test Pulse Scan
average TDC value
Sigma on the TDC
test pulse step
test pulse step
July 10, 2008
PHENIX RPC review
C.Y. Chi

12. RPC FEM crate Output XMIT To L1 T D C T D C Clock Master
L1 primitives T D C T D C
Output
To L1
XMIT
Clock
fanout
Clock Master
TDCs
Control
Slow
GTM
DCM L1
RPC(HBD) crate/BUS structure 6Ux160 mm VME size
July 10, 2008
PHENIX RPC review
C.Y. Chi

13. RPC Trigger Board 2.8 Gbits/sec
Transceiver blocks
Arria FPGA
De-serialized
FEM data &
format trigger
data
Optical transmitter
2.8 Gbits/sec
Optical transmitter
Trigger data from FEM
1 pair of cable per FEM
RPC triggers is being designed. Schedule for prototype around Sept.
The module can receive up to 6FEM’s trigger data
The optical trigger data contains, idle, clock numbers and up to 12 16bits
FEM trigger data every beam crossing.
July 10, 2008
PHENIX RPC review
C.Y. Chi

14. Channel count etc… (one side)
Station
1a+b 2 3
total
Channel
3072
3848
2872
9792
Channel per FEM (TDC) 64 65
FEM (TDC) 48
190
Disc Board 96
128
380
L1 trigger Fibers 8 16 32
FEM/ fibers 6 4
Support board/crate
FEM/crate 12
Crates
The crate size is like 6U VME crate.
I would like to limit the length discriminator cable to 10 meters.
(to be tested about jitters)
The RPC2, 3, we will need to find the crate space near the detector.
Crate need to be recess in the rack. Cable routing space needed in front of the crate.

15. Channel count etc with RPC2/3 strips combined… (one side)
Station
1a+b 2 3
total
Channel
3072
~3848/2
~2872/2
Channel per FEM (TDC) 64
FEM (TDC) 48 32 24
104
Disc Board 96
208
L1 trigger Fibers 8 16
FEM/ fibers 6
XMIT to DCM 4 5
L1 boards
FEM/crate 12
~10
Crates
The crate size is like 6U VME crate.
I would like to limit the length discriminator cable to 10 meters.
(to be tested about jitters)
The RPC2, 3, we will need to find the crate space near the detector.
Crate need to be recess in the rack. Cable routing space needed in front of the crate.

16. STATUS
The discriminator and TDC modules has been successfully prototyped.
Waiting for on chamber testing.
Grounding issue need to be resolved with chamber testing
CMS 32 channel board has been tested in both Colorado and BNL factory.
We are building, 40 discriminator modules, 20 TDC boards, 3 sets of crates+ clock master modules for the coming run and individual factory readout/test stand.
Trigger modules is being designed.
July 10, 2008
PHENIX RPC review
C.Y. Chi