the pixel ionisation chamber: a detector for beam monitor and dosimetry a.boriano 1,2, f.bourhaleb...

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

([email protected])



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



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

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



6

Linearity at 100 fC charge quantum

20 pA < I < 0.6 A

Linearity better than 0.7 %



7

Linearity at 600 fC charge quantum

10 pA < I < 2 A

Linearity better than 0.3 %



8

Spread of charge quanta

RMS 1 %RMS 1 %

I = 49.96 nA

26 chips



9

Reproducibility of charge quantum

I = 49.96 nAQc = 600 fC24 ºC < T < 27 ºC1 month6 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

<100 m



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



12

Spatial resolution

Spatial resolution < 0.2 mm



13

Homogeneity of response

18 × 18 cm2 uniform field18 × 18 cm2 uniform field

= 1.1 % = 1.1 %

= 2.0 % = 2.0 %



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



15

Comparison with PSI proton beam transverse profile



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)



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)

the pixel ionisation chamber: a detector for beam monitor and dosimetry a.boriano 1,2, f.bourhaleb...

Documents

roberto cirio infn torino

pmrc tsukuba

pixel ionisation chamber

digital conversion slide

digital output slide

belgium ptcog

iba magic cube

custom chip tera05