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The pixel ionisation chamber: a detector for beam monitor and dosimetry

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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 ... – PowerPoint PPT presentation

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Title: The pixel ionisation chamber: a detector for beam monitor and dosimetry


1
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, Italy
  • 2 University and INFN, Torino, Italy
  • 3 ICSC WorldLab, Lausanne, Switzerland
  • 4 TERA Foundation, Novara, Italy
  • partially supported by IBA, Louvaine- la-Neuve,
    Belgium
  • PTCOG XXXV PMRC Tsukuba November 15 2001

2
Improving the Magic Cube (3D dosimeter for
hadron beams)
The Magic Cube can be bought at Physalus
(furio.gramatica_at_physalus.it)
3
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, perform analog to digital conversion

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

5
TERA05
  • Very Large Scale Integration (VLSI)
  • i?f conversion
  • output ? Qint
  • 100 fCltcharge quantumlt800 fC
  • Imax 4 ?A
  • 64 channels
  • 16 bit wide counters
  • multiplexed digital output
  • dead-time free readout
  • max read out 10 MHz

6
Linearity at 100 fC charge quantum
  • 20 pA lt I lt 0.6 ?A
  • Linearity better than 0.7

7
Linearity at 600 fC charge quantum
  • 10 pA lt I lt 2 ?A
  • Linearity better than 0.3

8
Spread of charge quanta
  • I 49.96 nA
  • 26 chips

9
Reproducibility of charge quantum
  • I 49.96 nA
  • Qc 600 fC
  • 24 ºC lt T lt 27 ºC
  • 1 month
  • 6 measures

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

11
Beam test at GSI
12
Spatial resolution
13
Homogeneity of response
14
Beam test at PSI
15
Comparison with PSI proton beam transverse profile
16
very good for IMRT with photons too !(cfr.
collaboration with IBA/Wellhofer/Scanditronix)
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
17
Conclusions
  • parallel 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)
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