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| TUPPP01 |
DEE Voltage Calibration for the ACCEL Proton Therapy Cyclotron
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102 |
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- J. H. Timmer, P. A. Komorowski, H. Röcken
ACCEL, Bergisch Gladbach
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ACCEL Instruments GmbH has developed a superconducting cyclotron for the use in proton therapy systems. An essential step during the commissioning of the medical cyclotron is the calibration and balancing of the DEE voltages. Using a very compact and low cost X-ray detector the bremsstrahlung spectrum of stray electrons accelerated by the four RF cavities has been measured. To determine the peak voltage a regression analysis of the measured spectrum has been carried out using a non-linear multiple convolution model taking into account the energy gain of the stray electrons between the liner and the DEE, the bremsstrahlung spectrum integrated over angle as well as the attenuation effects caused by the liner and the limited detector resolution. The correlation between the model and the measurement was very good. A software tool enabling automatic spectrum acquisition and analysis capable of online determination of the DEE voltages has been developed in LabVIEW graphical programming environment. Careful balancing of the DEE voltages resulted in better beam focusing and a cyclotron extraction efficiency larger than 80%. The absolute acceleration voltage has been confirmed by turn-separation measurements.
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