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 2,3, F. Marchetto 3, C. Peroni 3, C.J. Sanz Freire 1,3 1 Ion Beam Applications, Louvain la-Neuve, Belgium 2 TERA Foundation, Novara, Italy 3 University and INFN, Torino, Italy

PTCOG outline outline Mechanical structure of the pixel ionisation chamber Mechanical structure of the pixel ionisation chamber Read-out: electronics and performances Read-out: electronics and performances Data Acquisition System Data Acquisition System Results from test with protons at PSI Results from test with protons at PSI Results from test with C +6 at GSI (2000) Results from test with C +6 at GSI (2000) Preliminary results from test with C +6 at GSI (2002) Preliminary results from test with C +6 at GSI (2002)

PTCOG 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, to perform analog to digital conversion

PTCOG 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 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 Linearity at 100 fC charge quantum 20 pA < I < 0.6  A Linearity better than 0.7 %

PTCOG Linearity at 600 fC charge quantum 10 pA < I < 2  A Linearity better than 0.3 %

PTCOG Reproducibility of charge quantum I = nA Qc = 600 fC 24 ºC < T < 27 ºC 1 month 6 measures

PTCOG 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 <100 m

PTCOG Beam test at PSI PSI test with a 138 MeV proton beam PSI test with a 138 MeV proton beam 7 mm FWHM beam 7 mm FWHM beam Spot-scanning Spot-scanning Uniformity of the response ~0.9% Uniformity of the response ~0.9% Profiles measurement ok Profiles measurement ok

PTCOG Beam test at GSI Beam characteristics raster-scan delivery system C +6, beam dimension = 8.8 mm (FWHM) data acquisition synchronized with raster-scan Aims spatial resolution homogeneity of response

PTCOG Spatial resolution Spatial resolution  < 0.2 mm

PTCOG Homogeneity of the response 18 × 18 cm 2 uniform field  = 1.1 %  = 2.0 %

PTCOG PMC FIFOFIFO CPU Pixel chamber PC OUT 16 bit Operative Systen VxWorks with Tornado II environment 1024 pixel 4 chip 4 chip 4 chip DAQ- test gsi 2002

PTCOG pixels map The map follows the beam... Daq with 49 pixels map

PTCOG Beam intensity dependence 1 single voxel treated with several beam intensities Deviation from linearity is within 1%

PTCOG Spatial resolution 14x14 cm 2 field ~2100 voxels DAQ: 7x7 map that follows the beam Spatial resolution  < 0.2 mm

PTCOG

PTCOG

PTCOG 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 TERA0 5 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 rate = 10 MHz channel # 1 channel # 64

PTCOG Read out electronics Recycling Integrator architecture.

PTCOG Spread of charge quanta RMS  1 % I = nA 26 chips

PTCOG 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 Slow data acquisition