Status of the CARIOCA project

LEB Conference, Stockholm 2001

Status of the CARIOCA projectStatus of the CARIOCA projectWalter BoniventoWalter Bonivento

CERN / INFN CagliariCERN / INFN Cagliarifor the LHCb collaborationfor the LHCb collaborationand the CERN MIC groupand the CERN MIC group

LEB Stockholm 2001

W.Bonivento CERN/INFN Cagliari

The LHCb muon The LHCb muon detectordetector

R3-R4 of M4-M5 RPC 48% area rate cap. 1kHz/cm2

R1-R2 of M1 t.b.d. 1% area rate cap. 1MHz/cm2

the rest MWPC 52% area rate cap. 100kHz/cm2

LHCb muon detector: main task provide L0 trigger for b X

Five stations, M1 to M5; four radial regions, R1 to R4

LEB Stockholm 2001


Readout electronicsReadout electronicsfor MWPC:for MWPC:

a) detector architecture a) detector architecture

2mm gap, 1.5mm wire spacing

wire, cathode and combined readout

Main performance requirement: efficiency in 20ns >99%

2 bi-gap logically OR-ed (DIALOG chip)

LEB Stockholm 2001


Detector signal: current with fast (ns) rise, fall

Detector capacitance from 20pF to 200pF

One threshold for time stamping: time resolution from slewing effect


b) requirementsb) requirements

Optimum amplifier peaking time compromise between noise and slewing

5.1)(1nst

LEB Stockholm 2001


Optimum amplifier peaking time: about 10ns

At large Cdet weak dependence of time resolution on peaking time

To be able to set the threshold at about 6 p.e.



Measurements on a prototype chamber performed with ahybrid from PNPI and a modified version of ASDQ chip (M.Newcomer-Penn)

noise <2fC for Cdet 40-250pF

At gas gain of 105

average 40fC for wires and 20fC for cathode range 150fC for 95% of the signals

LEB Stockholm 2001


High rate: dead time

pulse width <50ns unipolar and tail cancellation

wire signals AC coupled with RLCdec= 100s

baseline shifts baseline restoration

Low cross-talk : Zin< 50



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CARIOCACARIOCAProject overviewProject overview

80k FE channels at 1Mrad dose in 10 years custom chip in radiation tolerant technology 0.25 m CMOS

Final goal: differential structure

Cancels preamp

tail

Cancels 1/ttail

LEB Stockholm 2001



PROTOTYPE CHIPS: step by step approach

•2000: positive preamp+current discriminator +LVDS 4ch (1 analog ch.)

•2001: positive preamp+current discriminator +LVDS 14ch

LEB Stockholm 2001



•2001: negative preamp 8ch analog

•2001: positive preamp+shaper 4ch analog (diff. out.)

•2001: positive preamp+shaper+voltage discriminator+LVDS 4ch (diff. out.)•2002: positive and negative full chain with baseline restorer (diff.out.)

LEB Stockholm 2001


The positive The positive preamplifier:preamplifier:

a) designa) designCurrent amplifier NMOS with current mode feedback; unipolar

feed

NN

CRgmgm

p 2321 Dominant pole at about 20MHz, the other two at

150MHz and 300MHz

Large input transistor W/L=1600m/0.7mId=2mA

6I

I

3

4

IN

OUT N

N

gmgm

Followed by current discriminator (presented at LEB2000 by D.Moraes and replaced by a voltage discriminator in next version) +LVDS driver

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b) measurementsb) measurements

Response to a delta Linearity...and analog measurements

Sensitivity: 8mV/fC (measurement)

Digital (S-curve)...

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Threshold vs.Cd

Response to a delta

Channel uniformity of noise and threshold: 7% r.m.s. Cross talk around 1%

Power consumption of about 18mW per channel dominated by LVDS driver

Simulation (CADENCE)

Analog measurementDigital measurement

Noise vs. Cd

ENC = 867e- + 36e-/pF

calculation from noise theory

LEB Stockholm 2001



b) measurementsb) measurementsProblems of the discriminator:1) it does not work below 10fC (need 5fC). It was tested on a chamber prototype efficiency plateau shifted by 100V w.r.t. to our best measurement (with ASDQ chip).

2) it slows down the signal rise-time significantly (input C of discr.)

Peaking time vs.Cd

7ns are expected from p.a. alone

Discriminator changed in next versions of the chip

LEB Stockholm 2001


The negative The negative preamplifier:preamplifier:

a) designa) design

N2,N3,N4 replaced by PMOS

LEB Stockholm 2001


The negative and The negative and positive preamp:positive preamp:

frequency responsefrequency response negative positive

Input impedance: below 50

3dB level is at:• 16 MHz for negative• 23 MHz for positive

CADENCE simulation

Closed loop gain

Cdet=60pF

LEB Stockholm 2001



b) measurementsb) measurementsResponse to a delta

Linearity

Cd=100pFCd=15pF

MeasurementsSimulation

LEB Stockholm 2001


Peaking time vs. Cdimproved w.r.t firstprototype

Sensitivity vs. Cd



Noise vs. Cd

Response to a delta

ENC= 951e- + 31e-/pF


Channel uniformity of noise and threshold: 7% r.m.s.

LEB Stockholm 2001




Response to a quasi 1/t pulse

Cd=15pF

Cd=100pFquasi 1/t injector

LEB Stockholm 2001


The shaper:The shaper:a) designa) design

Designed for 1ns peaking time (not to add to the preamp)

Folded cascode fully differential balanced (CMF)

Dominant pole (neglecting p.z. comp)at 160MHz

LEB Stockholm 2001


The shaper:The shaper:a) design a) design

snnsnsns

ss

ss

405.3809

/1/1

/1/1

42

31

4

3

2

1

Cdet=60pF

• 2-pole/zero network to compensate for the 1/t tail • basic idea from R.A.Boie et al.,NIM 192(1982)365• adapted to a differential amplifier design (M.Newcomer, Penn)

LEB Stockholm 2001


The shaper:The shaper:b) measurementsb) measurements

Response to a delta: single ended ouptut (true output will be differential)

Cd=15pF Cd=100pF

This prototype chip with the positive preamplifier

LEB Stockholm 2001



Response to a delta: single ended output (true output will be differential). Saturation current on ( ) and off ( )

Linearity: improved with saturation current ON (changes the DC level at the drain of N0)


LEB Stockholm 2001



Response to a delta: single ended output (true output will be differential). Saturation current on.

Cd=15pF

Cd=100pF

LEB Stockholm 2001



Noise vs. Cd

Sensitivity vs. Cd

Response to a delta: single ended output

ENC= 1290e- + 40e-/pFwith saturation current ON


Parallel noise term higher thanpreamp alone due to twopreamplifiers at shaper input

Peaking time vs. Cd.Faster than negative consistent with different bandwidth

LEB Stockholm 2001




Cd=15pF

Cd=100pF

LEB Stockholm 2001



Peaking time vs. Cd

Sensitivity vs. Cd

Pulse width vs. Cd



LEB Stockholm 2001


Conclusions and Conclusions and perspectivesperspectives

• Amplifier+shaper+Voltage discriminator chip (following ATLAS MDT chip design) under test • +Baseline restoration chip under design

Negative preamplifier and positive preamplifier with shaperchips tested and satisfying the requirements for LHCb operation

LEB Conference, Stockholm 2001

THE ENDTHE END

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Status of the CARIOCA project