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Performances of a pixel ionization chamber to monitor a voxel scan hadron beam

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

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Performances of a pixel ionization chamber to monitor a voxel scan hadron beam

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  1. 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

  2. outline • Mechanical structure of the pixel ionisation chamber • Read-out: electronics and performances • Data Acquisition System • Results from test with protons at PSI • Results from test with C+6 at GSI (2000) • Preliminary results from test with C+6 at GSI (2002) sanz@to.infn.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, to perform analog to digital conversion sanz@to.infn.it

  4. 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 sanz@to.infn.it

  5. 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 sanz@to.infn.it

  6. Linearity at 100 fC charge quantum • 20 pA < I < 0.6 A • Linearity better than 0.7 % sanz@to.infn.it

  7. Linearity at 600 fC charge quantum • 10 pA < I < 2 A • Linearity better than 0.3 % sanz@to.infn.it

  8. Reproducibility of charge quantum • I = 49.96 nA • Qc = 600 fC • 24 ºC < T < 27 ºC • 1 month • 6 measures sanz@to.infn.it

  9. <100 m 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 sanz@to.infn.it

  10. Profiles measurement ok • Uniformity of the response ~0.9% Beam test at PSI • PSI test with a 138 MeV proton beam • 7 mm FWHM beam • Spot-scanning sanz@to.infn.it

  11. 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 sanz@to.infn.it

  12. Spatial resolution  < 0.2 mm Spatial resolution sanz@to.infn.it

  13. 18 × 18 cm2 uniform field  = 2.0 %  = 1.1 % Homogeneity of the response sanz@to.infn.it

  14. DAQ- test gsi 2002 Pixel chamber PMC 4 chip CPU PC 1024 pixel 4 chip 4 chip F I F O OUT 16 bit 4 chip Operative Systen VxWorks with Tornado II environment sanz@to.infn.it

  15. Daq with 49 pixels map 49 pixels map The map follows the beam... sanz@to.infn.it

  16. Beam intensity dependence • 1 single voxel treated with several beam intensities • Deviation from linearity is within 1% sanz@to.infn.it

  17. Spatial resolution • 14x14 cm2 field • ~2100 voxels • DAQ: 7x7 map that follows the beam Spatial resolution  < 0.2 mm sanz@to.infn.it

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  20. 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. sanz@to.infn.it

  21. channel # 1 channel # 64 TERA05 • Very Large Scale Integration (VLSI) • if conversion • output  Qint • 100 fC<charge quantum<800 fC • Imax= 4 A • 64 channels • 16 bit wide counters • multiplexed digital output • dead-time free readout • max read out rate = 10 MHz sanz@to.infn.it

  22. Read out electronics Recycling Integrator architecture. sanz@to.infn.it

  23. RMS  1 % Spread of charge quanta • I = 49.96 nA • 26 chips sanz@to.infn.it

  24. Data acquisition Slow 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 sanz@to.infn.it

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