Download - RPC Front End Electronics
Sept 25, 2008 PHENIX RPC review
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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
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020406080
100120140160180
1 3 5 7 9 11 13 15 17 19
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.
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CMS RPC preamp/discriminator chipBuild 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.
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Chip production With help of Giuseppe Isaelli and Flavio Loddo from Bari Italy,
we got 4 32 channel CMS boards about 1.5 years ago. These boards works both on the bench in Nevis and chamber
testing in University of Colorado. We decide to use the CMS RPC chip as the frontend
discriminator chips. With help of Flavio, the chip production start at end of the last
year. The wafer is fabricated in AMS through EuroPratice and
packaged in Taiwan The chip testing is done by Matrix. (the same company did the
CMS RPC chip testing) The yield is around 99%, few bad chips out of ~2000
We now have twice more chips than we needed in hand.
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Cable adapter board
RPC 32 channel discriminator board
32 channels per boardFused +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) andFire test pulse. One DAC setting per chip.
LVDS discriminator output
Serial download
The design is following closely the CMS design
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RPCdisc32ch
3M6834-4500PL
Or8534-4500pl
RPCTDC64ch
Half octant Detector
Module edge
AdapterBoard
AdapterBoard
2-3 m cable ? 8-18 meters cable ?
2-3 m cable? 8-18 meter cable ?
3M (Gray)3432-5302
3M (Black)3432-
5302RB
3M (Gray)3417-6640
3MN3432-L302RB
3M (Black)D89140-????
Signal Cable : 40 conductors twist flat ribbon cable
3M (gray)3431-5302
3M4640-7300
3M 1700/40 Twisted Pair, Flat Cable, .050" 28 AWG StrandedFire rating VW-1
16 short RG174 cables
Connection diagram
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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
On board test pulse vs. threshold study
TDC bin size ~2.5ns
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Direct Pulse Injection (fixed threshold)
Inject test pulse through the cable adapter card + 10pf capacitance (channel 45)
2mv per step, 160mv threshold (~80fc)
Cross talk seen at round 100mv.
Input (steps)
Channel 45
TDC
Channel 46Channel 44
disc.fired
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DISC LVDS output at discriminator board
DISC output after
~10 meter cables
69 ns time difference1.61ns/ft ~42 ft
Digitally subtracted pulse between+ and – side of discriminator LVDS output
500mv per division
1.4V
1.63V
RMS on the TDC distribution at step=60
0
0.1
0.2
0.3
0.4
0.5
0.6
0 20 40 60 80
channel
RM
S
rms
Long output cable study 1
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Short Cable
Disc threshold
TDC
79 ft cable (~24 meters)
Long output cable study 2
100 mv/div 50ns/div
The station 2 cable length could be along as 20 metersAlthough the result looks O.K., but this is in a lab environment.
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DISC
LVD
SR
eceiver
Triggerwindow
32 channeldigitizer
PLL TestPulse
LVDSTransmitter
4x beam clock
44X BC
44X BC Test Pulse
MA
SK
Serial dow
nload
Disc Serialdownload
TDC serial download
Interface Chip
Collects 64
ChannelOf
Data
DigitizedData
L1 trigger etc
L1 trigger primitives
L1 trigger primitives
Serial DownloadTiming etc.
EventData
EventData
RPC TDCMODULE
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The TDC Internal Test Pulse Scan
test pulse step test pulse step
average TDC
value
Sigma on the
TDC
TDC: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)
TDC Module
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RPC(HBD) crate/BUS structure 6Ux160 mm VME size
TDC
TDC
OutputTo L1
Clockfanout
L1 primitives
L1
GT
M Slow
Control
TDCs XMIT
DC
M
Clock Master
RPC FEM crate
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Trigger data from FEM1 pair of cable per FEM
Arria FPGADe-serializedFEM data &
format triggerdata
Transceiver blocks
RPC Trigger Board
Optical transmitter
Optical transmitter
2.8 Gbits/sec
RPC triggers has been layout.
The module can receive up to 6 (8) FEM’s trigger dataThe optical trigger data contains, idle, clock numbers and up to 12 16bits
FEM trigger data every beam crossing.
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Channel count etc… (one side)
Station 1a+b 3 totalChannel 3072 2872 5944
Channel per FEM (TDC)
64 64
FEM (TDC) 48 48 96
Disc Board 96 96 192
L1 trigger Fibers 8 8 16
FEM/ fibers 6 6Support board/crate 3 3FEM/crate 12 12
Crates 4 4 8
The crate match 6U VME crate mechanical size.
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Production QA
For discriminator boards We do even/odd channel direct pulse inject
through a 12 bits DAC pulser vs threshold We do on board test pulse test vs threshold
For TDC boards Fire the discriminator on board test pulse can
check the data TDC internal test pulse scan Data to L1 trigger board test. ( still need to be
works out)
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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.
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Production Outlook The production cycle normally last about 6
months. This include, fabricate boards, buy parts, board assembly and testing.
We will start production around Nov this year. The discriminator board does not have many
parts, the cycle will be slightly shorter.