The on-line detectors of the beam delivery system for the Centro Nazionale di Adroterapia Oncologica(CNAO)

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Osborne Rudolph Bryant
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Monaco1,2, A. Pecka1,2, C. Peroni1,2,G. Russo1,2, R.

1 The on-line detectors of the beam delivery system for the Centro Nazionale di Adroterapia Oncologica(CNAO) A. Ansarinejad1,2, A. Attili1, F. Bourhaleb2,R. Cirio1,2,M. Donetti1,3, M. A. Garella1, S. Giordanengo1, F. Marchetto1,V. Monaco1,2, A. Pecka1,2, C. Peroni1,2,G. Russo1,2, R. Sacchi1,2 Istituto Nazionale di Fisica Nucleare (INFN), Torino, Italy 2 Dipartimento di Fisica Sperimentale, Università di Torino, Italy 3 Fondazione CNAO, Milano, Italy 1 * Presenting author; A. Ansarinejad ansari@to.infn.it

2 Overview Hadrontherapy CNAO Project Monitor system Tests and measurements Results Conclusions

3 Hadrontherapy Advantages: Comparison 110 Low dose on surface High dose in depth Carbon ions High precision on dose delivery Dose [%] 80 Minimal lateral Scattering and Electrons 50 fragments effect 40 Photons Depth [mm]

4 CNAO Project in progress Centro Nazionale di Adroterapia Oncologica

The CNAO Synchrotron Protons: 60-250 Mev Carbon ions: 120-400 Mev/u Active system of dose distribution Beam dimension: 4-10mm(FWHM) Max particles

5 The CNAO Synchrotron Protons: Mev Carbon ions: Mev/u Active system of dose distribution Beam dimension: 4-10mm(FWHM) Max particles number/spill: 1010(p) 4 x 108 ( C+6) Max field dimension: 20x20cm2 Three treatment rooms Extraction lines: -Three identical horizontal lines -One vertical line

6 Active beam delivery system. Carbon source Proton source de/dz Synchrotron Z Ec Scanning magnets Active system of dose distribution Monitor system INFN and University of Torino in Collaboration with CNAO Foundation

7 Active system of dose distribution functionality Measure the beam position and fluence Required precision on the (X,Y) coordinate: ~100 mm Required precision on single beam fluence: ~1% of the total Operation flow Once the fluence required on a given spot is reached the beam is moved to the next spot by changing the current in the deflection magnets. During the beam delivery to a given spot, position corrections, when necessary, have to be applied again via deflection magnets Typical time constant to deflect the beam by few mm is ~ 200 ms Detector and control system Detectors are based on parallel plate ionization chambers with one of the electrodes splitted in pixels or strips Trasmission chambers with a low material budget Control system based on FPGA s

On-line monitor system For each beam-line: Box2 BEAM Box1 50 cm SUPPORTO NOZZLE 5 ionization chambers; 2 Integral chambers, 2 strip and 1 pixel In two completely independent

8 On-line monitor system For each beam-line: Box2 BEAM Box1 50 cm SUPPORTO NOZZLE 5 ionization chambers; 2 Integral chambers, 2 strip and 1 pixel In two completely independent boxes : chambers BOX1, BOX2 chamber (concerning read-out electronics and power supply) for safety reasons Gas used in chambers : nitrogen High voltage cathode polarization: + 400V

9 Monitor System Pixel Chamber: Integral 2D Position Chamber: Measurement 2D Intensity Intensity Measurement Measurement Precision 200 µm Strip Chambers: Position Measurement Integral Chamber: Relative intensity Intensity Measurement measurement every µs frequency 1MHz precision 100 µm I ral g nte 1 X p i r St BOX 1 Y p i r St f 1MHz I ral g nte 2 BOX 2 e Pix l

10 Detectors characteristics strip Between cathode and anode 5mm gap Anode Segmented in 128 strip 1.55 mm width with 0.1 mm of space pixel Between cathode and anode 5mm gap Anode Segmented in 1024 pixel pitch : 6.6 mm

11 Detector Assembly Electrodes foils: Kapton( 25/50 µm) + Copper (20 µm) Mylar + Aluminum (12 µm)

12 Tightening Foil Stretching to obtain a flat surface 24 clamps - 20 N (Pixel anode) - 10 N (strip anode) - 5 N (mylar)

13 Cleaning tracks with compressed air Weight positioning Gluing

14 Pixel chamber Detector Assembly Soldering

15 Detector Assembly final product BOX1 BOX2

16 BOX Lay Out : Detectors (chambers), Readout Board and Slow Control Board READOUT BOARD DETECTORS SLOW CONTROL BOARD

17 Front-end Number of channels to be read-out: ~1600 channels To avoid calibration (as much as one can) the channel gains have to be uniform Designed a ASIC chip TERA, developed for radiotherapy monitors (MatriXX, StaTrack, Compass, etc ) TERA µm CMOS technology

18 Strip and Pixel Chambers Readout FRONT END TERA 06 Recycling integrator architecture 64 channels 100 fc charge quantum 800 fc Max counting rate 5 MHz Acquisition speed 10 MHz Latch dead time free read-out Non Linearity <1% Readout board

19 Detectors Characterization preliminary tests ( X-ray tests) Portable X Data Acquisition Ray source for laboratory System with 2mm diameter collimator 50 kv and 160 mas BOX containing the Experimental Setup ionization

20 Detector specifications Response uniformity (+/- 2%) obtained with a uniform electronic gain over the channels (ASIC chip TERA06) and gas gap constant over the full active area Gain corrections: temperature and pressure variation are corrected for and applied at each treatment fraction (1-3 min) Background current: Negligible (< 1%)

21 Temperature and pressure correction with a dedicated Slow Control Board Main features To read physical parameters (p, T, f,hv) from BOX1 and BOX2 To set cathode polarization High Voltage and intervention thresholds To identify and check the elements inserted in High Voltage the beam line cathode polarization Power Supply (0 : 1000V) P (mbar) and ΔP (mbar) sensors T (K) sensor

22 Characterization Tests Background Current: defined as the current leakage in condition of no beam. Must be very small to avoid the subtraction of noise Reproducibility: response constant with time Uniformity: defined as the gain uniformity of the detectors over the sensitive area. The identical behavior and same values of measurement in all of points on sensitive area to a fast and precise on-line monitoring.

23 Background Currents Mean Background current (fa) per channel Pixel and Strip Chambers 190 Charge Quantum fc 170 For each voltage the 160 measurement was repea five times, every 60s Voltage (V) Strip X Strip Y Pixel Background current smaller than 200 fa to be compared to typical current during treatment of na: at least three orders of magnitude smaller

24 Reproducibility Ratio Strip X/Integral 1 1,3 1,29 1,28 1,27 1,26 1,25 1,24 1,23 1,22 1,21 1,2 1, Run Serie 1 Results: StpX/Integral % Serie 2 Serie 3 Serie 4 10

25 Gain Uniformity X-Ray source using a 2mm colimator Scan on 64 points 8x8 matrix Moving the head of the X Ray Source RESULTS 1.70% for the strip chambers 2.03% for the integral chamber1 1.70% for the pixel chamber 1.89% for the integral chamber2 Moving BOX

26 Conclusions The beam monitor systems developed for the CNAO to control fluence and position of the proton/ion radiotherapy beams have been built and tested. The aimed position precision is +/- 100 mm and the fluence uncertainty on a single beam is less than 1% of the total Temperature and pressure are measured and gas gain correction are applied Background currents are less than 200 fa, three orders of magnitude smaller than the nominal treatment current (na) Reproducibility in time of the response is better than 2% Gain uniformity over the sensitive area is better than 2%

The Electronics Readout and Measurement of Parameters of. a Monitor System

458 / 1004 The Electronics Readout and Measurement of Parameters of a Monitor System Abdolkazem Ansarinejad 1, Roberto Cirio 2 1 Physics and Accelerators School, Nuclear Science and Technology Research