La nuova elettronica di front-end
per il rivelatore RICH di COMPASS
Michela Chiosso
Università di Torino – Dip. di Fisica Generale
INFN – Sezione di Torino
1th Congressino di Dipartimento
Dip. di Fisica Generale A. Avogadro, 7- 8 Aprile 2008
Outline
 Cherenkov counters
 The COMPASS RICH:
general description
the multi-anode photomultipliers photon-detection
the read-out electronics
 CMAD-V3, a new front-end chip for the multi-anode
photomultipliers
The COMPASS experiment
COmmon Muon Proton Apparatus for Structure and Spectroskopy
270 physicists, 25 institutes, 11 countries
 nucleon structure
measurements
hadron spectroscopy
measurements
The COMPASS spectrometer
COmmon Muon Proton Apparatus for Structure and Spectroskopy
Rich detector: a cherenkov counter
Cherenkov Effect
cos qc
qC
= 1/bn
b thr 
1
n
qmax
1
 arccos
n
 qC  0
The ingredients:
1. Radiator
2. Light collector
3. Large area photon detectors

b 1
d2N 2z 2
2


sin
c
2
dxd 

 
 p .e .
N p .e .
 minimizing p.e
 maximizing Np.e.
Cherenkov Light Imaging Technique:
the first paper
. ..... .. ...
RICH
Ring Image Cherenkov
1977 Ypsilantis & Seguinot
Gaseous radiator; image focusing by spherical or
parabolic mirrors
Particle Identification
COMPASS RICH  gaseous radiator
COMPASS RICH
Radiator
C4F10
 transmittance > 80% (=165 nm)
 n=1.0015
Light collector
2 spherical mirrors:
 total surface = 21m2
 Angular acceptance:
± 250 mrad horizontal; ± 180 mrad vertical
Photon-detectors
 12 MWPC with CsI photocathodes
 4 camera with multianode photomultipliers
The photon detectors
MWPCs with CsI Photocathodes
(already in use since 2001)
FAST photon detection system
•
•
MAPMTs 576 in total
telescopes of fused silica lenses
•
read-out electronics:
 sensitive FE:
MAD4 chip
 TDC: F1
Time resolution: few ns
MAPMT
aspherical surface
spherical surface
planar surface
Inside
A photon-detector view…
CsI MWPC
MaPMT
Outside
MAD4 + F1
Phast photo-detection system
Photon detectors : MAPMT
 wide wavelength range
 time resolution < 1 nsec
 adequate for high rate operation – up to which rate ?
 robust
Summarising:
 good for next RICH generation
 but expensive for large surfaces
 our challenges:
 large ratio of the collection and photocathode areas
with minimal image distortion
 ratio = 7.3 achieved  LENS SYSTEM, critical design
 make use of the UV range  fused silica LENSES
couple to a read-out system able to guarantee efficiency,
high rate operation and to preserve time resolution
Performances
Ch photons from
physics event
photons / ring (b≈ 1) 65
time resolution <1ns
ring (b ≈1) : 0.3 mrad
2  /K separation at ph> 55 GeV/c
Excellent suppression of m-halo
high rate capability: up to 100 kHz
Ch photons from
m-halo
Single photoelectron detection
Hamamatsu R7600-03-M16 MAPMT
pedestal
bialkali photocathode, 18x18 mm2 active surface, 16 pixels
1 multiplication stage less
1e
UV extended glass window with borosilicate glass
(200 – 700 nm)
Wide dynamic range
all these photoelectrons
must be detected for
good efficiency
Hit multiplicity per event vs threshold
~ 30 fC
~ 90 fC
~ 270 fC
Large flat region between cross-talk and detection losses region
MAPMT readout electronics
MAD4 boards and Dreisam
boards mounted close to the
MAPMTs
144
DREISAM
boards
576
16-channel
PMT
9 CATCH
1152
MAD4
boards
144
Roof
boards
144 gigabit 36 HOT-CMC
optical fibres
Readout electronics of 1 quarter
Analog electronics:
MAD4 boards + Roof board
 Based on MAD4 chip:
pre-amplifier + shaper + comparator
 Low noise: 5-7fC
 Average PMT signal: 500 fC
 Up to 1MHz/channel
7 fC
CMAD: the new front-end chip for
RICH-MAPMT
Chip designed to replace the older ASIC (MAD4)
Key requirements:
Preserve the compatibility with the existing read-out
Gain optimized for MAPMT read-out
8 channels per chip
Gain programmable channel by channel
Threshold and baseline adjustable channel by channel (on board DACs)
.
Hits rate > 5 MHz
From 0.8 mm BiCMOS
to 0.35 mm CMOS
CMAD versus MAD4
CMAD
MAD4
8 channels
4 channels
programmable gain channel by channel:
from 0.4mV/fC to 1.2mV/fC in step of 0.08;
additional 4x gain multiplication
fixed gain = 3.5 mV/fC
improved baseline restorer:
able to cope with a rate > 5MHz/channel
baseline restorer:
up to 1 MHz/channel
programmable threshold on each single
channel
programmable common
threshold for 4 channels
programmable baseline on each single
channel
-------------------
10 bits threshold DAC on chip
8 bits threshold setting
the full biasing circuit is incorporated on chip
CMAD: Channel overview
in
FE
out +
VBL
LVDS
One shot
VTH
out b7
b9
DAC
b0
b7
b9
DAC
b0
Front-end building blocks
in
Preamp
Vref_OTA
OTA
+
BLH
Vout
 Variable gain preamp
 shaper
 baseline restorer
Vref_blh
From the 1th DAC
CMAD: some test results
Preamplifier
Linearity
Gain Control
Threshold and baseline
settings
(DACs test)
Channels equalization
Channel speed
CMAD: some test results
Preamplifier
Linearity
CMAD: some test results
Gain Control I
C=C feedback
R=R feedback
Cdigit = Rdigit
CMAD: some test results
Gain Control II
CMAD: some test results
Threshold and baseline
settings
(DACs test)
CMAD: some test results
Threshold and baseline
settings
(DACs test)
Channels equalization
CMAD: some test results
Channel speed
CMAD: In production!
CMAD Team
M.Chiosso, O. Cobanoglu, P. Delaurenti, M. Brusa, G. Mazza, D. Panzieri, A. Rivetti
Thanks to many colleagues…
the COMPASS Torino group
Università di Torino – Dip. Di Fisica Generale A. Avogadro
I.N.F.N – Sezione di Torino
Maxim
ALEKSEEV
Antonio AMOROSO
Ferruccio BALESTRA
Raimondo BERTINI
Maria P. BUSSA
Michela CHIOSSO
Marialaura COLANTONI
Oleg Yu. DENISOV
Andrea
FERRERO
Raffaello GARFAGNINI
Ivan GNESI
Antonino GRASSO
Angelo
MAGGIORA
Marco MAGGIORA
Daniele PANZIERI
Bakur PARSAMYAN
Guido PIRAGINO
Elena ROCCO
Stefano SOSIO
Torino group responsabilities in COMPASS
collaboration
Detectors
Multiwire proportional chambers (MWPCs)
Rich-Wall
RICH electronics and mirrors
MW1 electronics
Physics
Pion polarizability analysis (Primakov)
L polarization analysis
Drell-Yan physics at COMPASS (proposal)
Hadron run coordination
Spare Slides
New PID performances
Kaons identification efficiency
 PID efficiency studies based on kaons from decay of exclusive F(1020)
(Ch.threshold < pk < 60 GeV/c)
Michela Chiosso
10th ICATPP
09/10/2007
New PID performances
2006 data
efficiency vs θk
Michela Chiosso
10th ICATPP
09/10/2007
10 bit DAC