Speaker
Description
A dedicated pencil beam scan system is developed and integrated into the proton therapy system of China Institute by a joint effort of Pyramid Consult Inc. and China Institute of Atomic Energy. In nozzle commissioning, a proton beam with an intensity of tens nA is provided by the CIAE beam production system, including a 242MeV superconducting cyclotron and a fast energy variable beam transportation system. Most of the scanning devices are commercial products from the pyramid, including the ion chambers, the helium beam path, the magnet, and its amplifier. A Scintillator - camera system named Lynx from IBA, is used to provide position readouts of the beam spot in the commissioning. A dedicated controlling software and related strategy for the beam commission of the scanning system is developed by the CIAE team. In the commissioning, firstly, a straightforward irradiation consisting of 114 beam spots is carried out to evaluate both the nonlinearity and cross-talks of the scanning magnets. Afterward, these coordinates are generated by Lynx and analyzed by the reported software. A modified 2D polynomial fitting, including Hyperbolic Functions, is invested in the commissioning to yield an open loop control accuracy in orders of millimeters. An iterative learning algorithm is also developed to give an even better accuracy. A 50mm separation irradiation map consisting of 37 points is carried out by combining these two corrections on the first day of commission, reaching an accuracy of 0.55mm. An irradiation field of 250mmX250mm is also verified at the same time.
| Minioral | Yes |
|---|---|
| IEEE Member | No |
| Are you a student? | No |
