Upload
brandy-curry
View
222
Download
0
Tags:
Embed Size (px)
Citation preview
The pixel ionisation chamber: a detector for beam monitor
and dosimetry
A.Boriano 1,2, F.Bourhaleb 2,3, R. Cirio 2, M. Donetti 2,4, F. Marchetto 2, C. Peroni 2, C.J. Sanz Freire 2^
1 ASP, Torino, Italy2 University and INFN, Torino, Italy
3 ICSC WorldLab, Lausanne, Switzerland4 TERA Foundation, Novara, Italy
^ partially supported by IBA, Louvaine- la-Neuve, Belgium
PTCOG XXXV – PMRC Tsukuba – November 15 2001
PTCOG XXXV - PMRC Tsukuba November 15 2001
Roberto Cirio INFN Torino
2
Improving the Magic Cube (3D dosimeter for hadron beams)
The IBA Magic Cube at NPTC in BostonThe Magic Cube can be bought at Physalus
PTCOG XXXV - PMRC Tsukuba November 15 2001
Roberto Cirio INFN Torino
3
The pixel chamberparallel 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, perform analog to digital conversion
PTCOG XXXV - PMRC Tsukuba November 15 2001
Roberto Cirio INFN Torino
4
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 in digital output
PTCOG XXXV - PMRC Tsukuba November 15 2001
Roberto Cirio INFN Torino
5
TERA05Very Large Scale Integration (VLSI)if conversionoutput Qint
100 fC<charge quantum<800 fCImax= 4 A64 channels16 bit wide countersmultiplexed digital outputdead-time free readoutmax read out = 10 MHz
channel # 1
channel # 64
PTCOG XXXV - PMRC Tsukuba November 15 2001
Roberto Cirio INFN Torino
6
Linearity at 100 fC charge quantum
20 pA < I < 0.6 A
Linearity better than 0.7 %
PTCOG XXXV - PMRC Tsukuba November 15 2001
Roberto Cirio INFN Torino
7
Linearity at 600 fC charge quantum
10 pA < I < 2 A
Linearity better than 0.3 %
PTCOG XXXV - PMRC Tsukuba November 15 2001
Roberto Cirio INFN Torino
8
Spread of charge quanta
RMS 1 %RMS 1 %
I = 49.96 nA
26 chips
PTCOG XXXV - PMRC Tsukuba November 15 2001
Roberto Cirio INFN Torino
9
Reproducibility of charge quantum
I = 49.96 nAQc = 600 fC24 ºC < T < 27 ºC1 month6 measures
PTCOG XXXV - PMRC Tsukuba November 15 2001
Roberto Cirio INFN Torino
10
Data acquisition
connection detector-data acquisition by twisted pair flat cables (100 m maximum lenght)
max rate transfer = 10 MHz = 40 Mb/s
read out transfer time = 50 s
read out cycle total time = 100 s
real time operating system
<100 m
PTCOG XXXV - PMRC Tsukuba November 15 2001
Roberto Cirio INFN Torino
11
Beam test at GSI
Beam characteristics
raster-scan delivery system
270 MeV/u, C+6, 8.8 mm (FWHM)
data acquisition synchronized with raster-scan
Aims
spatial resolution
homogeneity of response
PTCOG XXXV - PMRC Tsukuba November 15 2001
Roberto Cirio INFN Torino
12
Spatial resolution
Spatial resolution < 0.2 mm
PTCOG XXXV - PMRC Tsukuba November 15 2001
Roberto Cirio INFN Torino
13
Homogeneity of response
18 × 18 cm2 uniform field18 × 18 cm2 uniform field
= 1.1 % = 1.1 %
= 2.0 % = 2.0 %
PTCOG XXXV - PMRC Tsukuba November 15 2001
Roberto Cirio INFN Torino
14
Beam test at PSI
Beam characteristics
spot-scan delivery system
138 MeV/u, p, 7 mm (FWHM)
data acquisition non-synchronized with spot-scan
Aims
Intercomparison
PTCOG XXXV - PMRC Tsukuba November 15 2001
Roberto Cirio INFN Torino
15
Comparison with PSI proton beam transverse profile
PTCOG XXXV - PMRC Tsukuba November 15 2001
Roberto Cirio INFN Torino
16
Field shape varying with time
6 MV Elekta accelerator at S.Anna hospital in Torino
1.2x1.2 cm2 square field going to
12.4x12.4 cm2 square field
…very good for IMRT with photons too …!(cfr. collaboration with
IBA/Wellhofer/Scanditronix)
PTCOG XXXV - PMRC Tsukuba November 15 2001
Roberto Cirio INFN Torino
17
Conclusionsparallel plate pixel ionization chamber
big sensitive area
1024 independent measurements
VLSI electronics dead-time free readout
one dead-time free readout of all 1024 channels every 100 s
GOOD MONITOR FOR SCANNED BEAMS
Next step might be a real-3D-Magic Cube ( dosimeter)