Performances of a pixel
ionization chamber to
monitor a voxel scan
hadron beam
A.Boriano 3, F.Bourhaleb
2,3,
R. Cirio 3, M. Donetti
F. Marchetto 3, C. Peroni 3, C.J. Sanz Freire
1
1,3
Ion Beam Applications, Louvain la-Neuve, Belgium
2 TERA Foundation, Novara, Italy
3 University and INFN, Torino, Italy
2,3,
outline
Mechanical
structure of the pixel
ionisation chamber
Read-out: electronics and performances
Data Acquisition System
Results from test with protons at PSI
Results
from test with C+6 at GSI (2000)
Preliminary
GSI (2002)
PTCOG 2002 - Catania
results from test with C+6 at
sanz@to.infn.it
The pixel
chamber

parallel plate ionization chamber

anode segmented in 1024 square pixels

pixel dimension = 7.5 X 7.5 mm2

sensitive area = 24 X 24 cm2

1 mm water equivalent thickness

front-end electronics, located around the
chamber, to perform analog to digital
conversion
PTCOG 2002 - Catania
sanz@to.infn.it
Detector
design
The detector has to be thin to
minimize the effects on the beam
energy and shape
Anode and cathode are glued to
frames in order to assure the
mechanical rigidity and the gap
thickness
Water equivalent thickness < 1 mm
PTCOG 2002 - Catania
sanz@to.infn.it
Front-end
electronics

located around the chamber

we have developed a full custom
chip (TERA05)

every chip has 64 channels that
convert the collected charge into
counts
PTCOG 2002 - Catania
sanz@to.infn.it
Linearity at 100 fC charge
quantum
PTCOG 2002 - Catania

20 pA < I < 0.6 A

Linearity better
than 0.7 %
sanz@to.infn.it
Linearity at 600 fC charge
quantum
PTCOG 2002 - Catania

10 pA < I < 2 A

Linearity better
than 0.3 %
sanz@to.infn.it
Reproducibility of charge
quantum
I = 49.96 nA
Qc = 600 fC
24 ºC < T < 27 ºC
1 month
6 measures
PTCOG 2002 - Catania
sanz@to.infn.it
Data
acquisition
Signals (RS422 standard) are
delivered via twisted pair flat cables
(100 m maximum length)

max transfer rate = 10 MHz = 40
Mbyte/s

read out transfer time = 50 s

read out cycle total time = 100 s

real time operating system
PTCOG 2002 - Catania
<100 m

sanz@to.infn.it
Beam test at PSI



Profiles

PSI test with a 138 MeV proton beam
7 mm FWHM beam
Spot-scanning
measurement ok
Uniformity of the response
~0.9%
PTCOG 2002 - Catania
sanz@to.infn.it
Beam test at GSI

Beam characteristics

Aims

raster-scan delivery system

spatial resolution

C+6, beam dimension = 8.8 mm
(FWHM)

homogeneity of
response

data acquisition synchronized with
raster-scan
PTCOG 2002 - Catania
sanz@to.infn.it
Spatial resolution
PTCOG 2002 - Catania
Spatial resolution
 < 0.2 mm
sanz@to.infn.it
Homogeneity of the response
18 × 18 cm2 uniform field
 = 2.0 %
 = 1.1 %
PTCOG 2002 - Catania
sanz@to.infn.it
DAQ- test gsi 2002
PC
CPU
Pixel chamber
4 chip
PMC
F
I
F
O
OUT
16 bit
1024
4
4
chip pixel chip
4 chip
Operative Systen
VxWorks with
Tornado II
environment
PTCOG 2002 - Catania
sanz@to.infn.it
Daq with 49 pixels map
49
pixels
map
The map
follows the
beam...
PTCOG 2002 - Catania
sanz@to.infn.it
Beam intensity dependence
 1 single voxel
treated
with several beam
intensities
 Deviation from
linearity is within 1%
PTCOG 2002 - Catania
sanz@to.infn.it
Spatial resolution
 14x14 cm2 field
 ~2100 voxels
 DAQ: 7x7 map that
follows the beam
Spatial resolution  < 0.2 mm
PTCOG 2002 - Catania
sanz@to.infn.it
PTCOG 2002 - Catania
sanz@to.infn.it
PTCOG 2002 - Catania
sanz@to.infn.it
Detector
design
Thick version
When used in plastic phantom the
detector can be thick.
With photon or electron beam air gap
has to be minimized.
Anode and cathode are glued to a
plastic slab, which is a grid of 1024
holes.
Each hole can be considered as an
independent sensitive volume.
PTCOG 2002 - Catania
sanz@to.infn.it
Very Large Scale
Integration (VLSI)
if conversion
output  Qint
100 fC<charge
quantum<800 fC
Imax= 4 A
64 channels
16 bit wide counters
multiplexed digital
output
dead-time free readout
max read out rate = 10
MHz
PTCOG 2002 - Catania
TERA0
5
channel # 1
channel # 64
sanz@to.infn.it
Read out electronics
Recycling Integrator architecture.
PTCOG 2002 - Catania
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Spread of charge
quanta
I = 49.96 nA
26 chips
RMS  1 %
PTCOG 2002 - Catania
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Data acquisition
Slow data acquisition
• connection by twisted pair flat
cables (100 m max)
• max rate transfer = 1 MHz =
2 Mbyte/s
• read out transfer time = 1 ms
• PCI DAQ card
• LabVIEW software
• cheap solution
• easy to handle
PTCOG 2002 - Catania
sanz@to.infn.it