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

PTCOG XXXV - PMRC Tsukuba November Roberto Cirio INFN Torino 2 Improving the Magic Cube (3D dosimeter for hadron beams) The IBA Magic Cube at NPTC in Boston The Magic Cube can be bought at Physalus

PTCOG XXXV - PMRC Tsukuba November Roberto Cirio INFN Torino 3 The pixel chamber parallel plate ionization chamber anode segmented in 1024 square pixels pixel dimension = 7.5 X 7.5 mm 2 sensitive area = 24 X 24 cm 2 1 mm water equivalent thickness front-end electronics, located around the chamber, perform analog to digital conversion

PTCOG XXXV - PMRC Tsukuba November 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 Roberto Cirio INFN Torino 5 TERA05 Very Large Scale Integration (VLSI) i  f conversion output  Q int 100 fC<charge quantum<800 fC I max = 4  A 64 channels 16 bit wide counters multiplexed digital output dead-time free readout max read out = 10 MHz channel # 1 channel # 64

PTCOG XXXV - PMRC Tsukuba November 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 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 Roberto Cirio INFN Torino 8 Spread of charge quanta RMS  1 % I = nA 26 chips

PTCOG XXXV - PMRC Tsukuba November Roberto Cirio INFN Torino 9 Reproducibility of charge quantum I = nA Qc = 600 fC 24 ºC < T < 27 ºC 1 month 6 measures

PTCOG XXXV - PMRC Tsukuba November 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 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 Roberto Cirio INFN Torino 12 Spatial resolution Spatial resolution  < 0.2 mm

PTCOG XXXV - PMRC Tsukuba November Roberto Cirio INFN Torino 13 Homogeneity of response 18 × 18 cm 2 uniform field  = 1.1 %  = 2.0 %

PTCOG XXXV - PMRC Tsukuba November 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 Roberto Cirio INFN Torino 15 Comparison with PSI proton beam transverse profile

PTCOG XXXV - PMRC Tsukuba November Roberto Cirio INFN Torino 16 Field shape varying with time 6 MV Elekta accelerator at S.Anna hospital in Torino 1.2x1.2 cm 2 square field going to 12.4x12.4 cm 2 square field …very good for IMRT with photons too …! (cfr. collaboration with IBA/Wellhofer/Scanditronix)

PTCOG XXXV - PMRC Tsukuba November Roberto Cirio INFN Torino 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)