Post on 01-Jun-2020
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Università degli studi di Torino
Tesi di Laurea Triennale“Characterization of front-end electronics boards for ionization chambers used to
monitor hadrontherapy beams”
di RIVERO FABIO
RELATORE: PROF. CRISTIANA PERONICO-RELATORE: DOTT. ALESSANDRO LA ROSA
September 2007 Fabio Rivero 2
KEY WORDS:• Hadrontherapy: Hadrons' beam for cancer treatment
Low dose on surface
High dose in depth
High precision on dose delivery
Minimal lateralscattering
• Monitoring and control of hadrontherapy beams
• Front-end electronics (TERA 06 Chip)
September 2007 Fabio Rivero 3
MY WORK FOR THE CNAO OF PAVIA
DETECTORSWITH THE
FRONT-END ELECTRONICS TESTED
Laboratorio Tecnologico (Via 7 Comuni, To)
Centro Nazionale Adroterapia Oncologica
September 2007 Fabio Rivero 4
THE PIXEL DETECTORSSTRUCTURE:
DEVELOPED FROM:
CHIP TERA 05 CHAMBERS(older
version)
MOPI (at Marie Curie
Institute, Orsay)
• Cathode - gap 5 mm – Anode• Anode subdivided in 1024 pixel• Pixel = 5 x 5 mm2
• Active area = 160 x 160 mm2
• Read-out: ASIC Tera06
September 2007 Fabio Rivero 5
THE ASIC TERA 06• Recycling integrator architecture
• 0.8 µm AMS CMOS
• 64 channel/chip
• 100 fC minimum detectable charge
• 1 µA maximum input current
• 200 fA background current
• 16 bit counters
designed by the INFN Torino Division
materially produced by the IBA Group, Belgium
• No dead-time in read-out
September 2007 Fabio Rivero 6
HOW THE CHIPS WORKI to f converter
QIN= 5us x 1uA= 5 pC
Qread= 8 x 600 fC = 4.8 pC
N = 8
∆V = 3 V;
Csub = 200 fF;Ch. Q = Csub*∆V = 600 fC
OTA_ref
SINGLE CHANNEL:
September 2007 Fabio Rivero 7
HOW EVERY CHANNEL WORKSEvery channel has:
• a converter, that converts current into frequency;
• a counter, of 16 bits;• a latch, that allows the
saving of the counts of every channel at the same time;
• a multiplexer, that unify all the 64 channels in order to allow the reading of the selected channel.
I→f converter 16 bit counter
I→f converter 16 bit counter
I→f converter 16 bit counter
I→f converter 16 bit counter
I→f converter 16 bit counter
... ...
in0
in1
in2
in62
in63
16
16
16
16
16
16
OTA
ref
Vpul
se+
Vpul
se-
A_re
set
latc
h
chan
nel
sele
ct6
MUX
D_r
eset
rstA : analogical reset signal;rstD : digital reset signal;
September 2007 Fabio Rivero 8
THE FRONT-END TERA 06: BOARDSTOP-SIDE: BOTTOM-SIDE:
SixLayers:Top layer
Layer 2
Layer 3 OTA
Layer 4 GND
Layer 5 Vcc
Bottom layer
CHIP 1
CHIP 0
September 2007 Fabio Rivero 9
HOW THE BOARDS WORK
September 2007 Fabio Rivero 10
TESTS DONE• PART 1: on all 60 boards
1. PEDESTALS: channel counts
2. CHARGE QUANTUM: quantization error
• PART 2: on few boards1. LINEARITY: variation of current into
channel2. STABILITY IN TIME: different
measurements at different times
September 2007 Fabio Rivero 11
Before testing…cleaning!ULTRASOUND CLEANER: BOARDS CLEANED
DRYING:
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EXPERIMENTAL SET UP
•Power supply card voltage fixed at 6 V;•Vota = 2.05 V, fixed reference voltage;•V th = 2.5 V, threshold comparator voltge;•V p+ = 3.12 V•V p- = 2.12 V( V p = V p+ - V p- = 1.0 V, Q = Csub x Vp )
•two comunication boards LA TxRx;•a computer with the necessary LabViewsoftware
POWER SUPPLY
the first to convert the TTL signal in RS422 long-distance standard, the second to convert RS422 in TTL
September 2007 Fabio Rivero 13
On all 60 boards PEDESTALS
Pedestal Spread
0,60
0,80
1,00
1,20
1,40
1,60
1,80
2,00
0 50 100
Channel
Pede
stal
(Hz)
FE_057_029FE_111_086FE_005_050
chip counting without current injected inFound by measuring the counts of the chips with every channel floating
<PED> ~ 1.2 Hz
September 2007 Fabio Rivero 14
On all 60 boards CHARGE QUANTUM:
Charge Quantum Spread
164166168170172174176178180182
0 50 100Channel
Cha
rge
Q.(f
C)
FE_044_024FE_090_076FE_084_015
Found by injecting manually current of 100 nAinto every channel of the chips with a injector
<C.Q.> ~ 173.26 fC and Stand. Dev of 2.26 fC or 1.3%
September 2007 Fabio Rivero 15
BACKGROUND CURRENTBackground Current Spread
100
150
200
250
300
350
0 50 100Channel
I(fA
)
057_029052_046005_050
On all 60 boards
I = Background Current;
f = Frequency
Q = Charge Quantum
PEDESTALS BACKGROUND CURRENT
<Ibk> ~ 195 fA
September 2007 Fabio Rivero 16
LINEARITYMeasuring the charge quantum at
different currentvalues (from 5 nA
to 1,5 µA)
On few boards
I = f * q
( I = current q = charge f = frequency )
0,00E+00
1,00E+06
2,00E+06
3,00E+06
4,00E+06
5,00E+06
6,00E+06
0 200 400 600 800 1000 1200 1400
Input Current (nA)
Out
put f
requ
ency
(Hz)
SATURATION FROM 850nA
RELATIVE DEVIATION UNDER 1%Verify the fit:
September 2007 Fabio Rivero 17
STABILITY IN TIME On few boards
Measuring the charge quantum at different times
A = taken on 12/07/07B = taken on 17/07/07 at
14:50C = taken on 17/07/07 at
16:12D = taken on 18/07/07 at
14:12
ratio A/B, A/C, A/D and the corrispondent percentual
relative deviation The test showed a perfect
constancy of measurements in time
Allunder 4 ‰
% Deviation FE_010_009
0
0,05
0,1
0,15
0,2
0,25
0,3
0,35
0,4
0 20 40 60 80 100 120
Channel
% D
evia
tion
FE_010_009 AB% deviation
FE_010_009 AC% deviationFE_010_009 AD% deviation
September 2007 Fabio Rivero 18
SUMMARY57 of them worked out correctlyThere had to be tested
60 boards3 with different
problems
On few boards :• the linear behaviour with the increase of current is confirmed, with a saturation after at least 850 nA of current;• there is no instability of measurements with time.
The working chips on board for the TERA 06 electronic front-end tested are ready to be mounted on the detector.
Our work on TERA 06 will be submitted in NIM A
September 2007 Fabio Rivero 19
THANKS TO:
Torino Group of Medical Physics• my parents
• Dott. Alessandro La Rosa
• my relator Prof. Cristiana Peroni and all the Torino Group of Medical Physics
September 2007 Fabio Rivero 20
Thanks for your attention!